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60,897 | When I step on gas pedal, the engine revs up but there is no acceleration. When step off gas a bit it car starts to accelerate again. It's a manual transmission. 2005 Toyota Corolla. This is happening more and more frequently.
Is this a problem with the transmission, clutch or something else altogether? And wondering if it's going to cost a lot to fix. | 2018/11/15 | [
"https://mechanics.stackexchange.com/questions/60897",
"https://mechanics.stackexchange.com",
"https://mechanics.stackexchange.com/users/43297/"
] | This sounds like the classic symptoms of a slipping clutch.
The solution is to replace it or have it replaced. If it is a DMF (Dual Mass Flywheel - fitted to reduce vibration) type then it is usually a good idea to replace that as well at the same time.
The minimum will be a centre or friction plate, but personally I will always fit a new pressure plate at the same time. If the flywheel surface shows serious signs of wear then that may need skimming or replacing.
As for prices, they vary between countries, and within countries even, for the cost of labor, parts also vary in price, so you have to find out for your area. | While I agree it is probably a slipping clutch, before I had the cluth and pressure plate replaced I think you would want to have the clutch pedal cable checked to see if it is mis-adjusted. In some cases the pedal play may be causing the clutch to be slightly engaged even when your foot is off the pedal. This adjustment should be very inexpensive if you haven't already polished (hence damaged) the friction plate.
The sooner the better to avoid further damage. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | If you are asking yourself how to find time working on your open source project, this may indicates that you are willing to work on too much things at the same time.
You may not be able to physically handle everything and the consequence is that you will be bad in most things you will work on because of the lack of time and focus.
Think about your baby! And your bachelor degree! It's already 2 FULL TIME projects believe me!
*Unless your open source project is more important than your baby or your bachelor degree, abandon your open source project for now.* | It depends upon how important the open-source project is in the grand cosmic scheme of things. If the project involves creating trivial screen-savers, you just work on it haphazardly now and then whenever you are too bored to do anything else. If it is a project like <http://code.google.com/p/mindforth> for creating true artificial intelligence that will bring on a Technological Singularity, then you need to organize your entire life and all available nanoseconds in service to your Grand Challenge Open-Source AI Project. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | It depends upon how important the open-source project is in the grand cosmic scheme of things. If the project involves creating trivial screen-savers, you just work on it haphazardly now and then whenever you are too bored to do anything else. If it is a project like <http://code.google.com/p/mindforth> for creating true artificial intelligence that will bring on a Technological Singularity, then you need to organize your entire life and all available nanoseconds in service to your Grand Challenge Open-Source AI Project. | I'd say that by far your most interesting project and top of the top priority at the moment is your baby - you should kick all the non-work related programming out and just enjoy the baby growing up, first smiles and giggles. Use your available time to watch a good movie/soccer game/ read a book, or whatever relaxes you. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | * The time with your kids is the most precious in the world, and it never comes back.
* Your degree will feed your family.
Prioritize accordingly :) | I'd say that by far your most interesting project and top of the top priority at the moment is your baby - you should kick all the non-work related programming out and just enjoy the baby growing up, first smiles and giggles. Use your available time to watch a good movie/soccer game/ read a book, or whatever relaxes you. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | If you are asking yourself how to find time working on your open source project, this may indicates that you are willing to work on too much things at the same time.
You may not be able to physically handle everything and the consequence is that you will be bad in most things you will work on because of the lack of time and focus.
Think about your baby! And your bachelor degree! It's already 2 FULL TIME projects believe me!
*Unless your open source project is more important than your baby or your bachelor degree, abandon your open source project for now.* | Most people have a fair amount of downtime that they use watching television. (This doesn't normally apply to parents of three-month-olds.) It isn't generally a matter of finding time, but finding energy and motivation.
Are you usually able to sleep through the night? I wasn't when my kid was that old. If you're not getting enough sleep, you're going to have a hard enough time with your schoolwork, let alone an outside project.
So, spend time with your wife and kid. Don't worry about extra projects for now, there will be more time for that a few years from now. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | I posted an answer to a similar question [here](https://softwareengineering.stackexchange.com/questions/12017/software-development-books-are-useful-but-when-to-find-the-time-to-read-them/12022#12022).
The bottom line is that you **make** time.
I'll demonstrate with an anecdote.
My sister is a novelist that writes purely in her spare time. She's got a husband and a son and she's published 4 books and a few short stories. On Mondays her husband and son (though he's 7 now, but she's been writing for a long time) know that it's her time to write. So mondays between 7 and 9 she writes, and they leave her alone.
Wednesdays, my brother-in-law plays hockey in a men's league. | I'd say that by far your most interesting project and top of the top priority at the moment is your baby - you should kick all the non-work related programming out and just enjoy the baby growing up, first smiles and giggles. Use your available time to watch a good movie/soccer game/ read a book, or whatever relaxes you. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | If you are asking yourself how to find time working on your open source project, this may indicates that you are willing to work on too much things at the same time.
You may not be able to physically handle everything and the consequence is that you will be bad in most things you will work on because of the lack of time and focus.
Think about your baby! And your bachelor degree! It's already 2 FULL TIME projects believe me!
*Unless your open source project is more important than your baby or your bachelor degree, abandon your open source project for now.* | I'd say that by far your most interesting project and top of the top priority at the moment is your baby - you should kick all the non-work related programming out and just enjoy the baby growing up, first smiles and giggles. Use your available time to watch a good movie/soccer game/ read a book, or whatever relaxes you. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | Most people have a fair amount of downtime that they use watching television. (This doesn't normally apply to parents of three-month-olds.) It isn't generally a matter of finding time, but finding energy and motivation.
Are you usually able to sleep through the night? I wasn't when my kid was that old. If you're not getting enough sleep, you're going to have a hard enough time with your schoolwork, let alone an outside project.
So, spend time with your wife and kid. Don't worry about extra projects for now, there will be more time for that a few years from now. | Since you don't want your opensource project to remain unfinished, I would suggest you to find someone who is willing to contribute to your project. So that at some point of time in the future, your project will get much more matured and you can always contribute it whenever you get time.
Family is much more important than any other things and any opensource project will get eventually succeed when multiple peoples started contributing to it. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | I'd say that by far your most interesting project and top of the top priority at the moment is your baby - you should kick all the non-work related programming out and just enjoy the baby growing up, first smiles and giggles. Use your available time to watch a good movie/soccer game/ read a book, or whatever relaxes you. | Since you don't want your opensource project to remain unfinished, I would suggest you to find someone who is willing to contribute to your project. So that at some point of time in the future, your project will get much more matured and you can always contribute it whenever you get time.
Family is much more important than any other things and any opensource project will get eventually succeed when multiple peoples started contributing to it. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | If you are asking yourself how to find time working on your open source project, this may indicates that you are willing to work on too much things at the same time.
You may not be able to physically handle everything and the consequence is that you will be bad in most things you will work on because of the lack of time and focus.
Think about your baby! And your bachelor degree! It's already 2 FULL TIME projects believe me!
*Unless your open source project is more important than your baby or your bachelor degree, abandon your open source project for now.* | I posted an answer to a similar question [here](https://softwareengineering.stackexchange.com/questions/12017/software-development-books-are-useful-but-when-to-find-the-time-to-read-them/12022#12022).
The bottom line is that you **make** time.
I'll demonstrate with an anecdote.
My sister is a novelist that writes purely in her spare time. She's got a husband and a son and she's published 4 books and a few short stories. On Mondays her husband and son (though he's 7 now, but she's been writing for a long time) know that it's her time to write. So mondays between 7 and 9 she writes, and they leave her alone.
Wednesdays, my brother-in-law plays hockey in a men's league. |
13,870 | A bit of background: I've got a small open source project that I've started on, a basic framework which provides an object oriented means of generating HTML code (since I don't really like HTML, and I do like PHP). It has some released source, and a few downloads, but primarily, the project is for me, with the Open Source portion just being a side benefit.
The original project which caused me to be able to develop on this project has mostly gone into hibernation for the time being, which means that all the development I get to sink into it at this point is personal time only. Unfortunately, I'm currently working toward my bachelor's degree, studying for certifications, and I have a three month old baby at home. In short, by the time I get around to "me time", I rarely feel like doing work, but rather usually feel like just chilling out.
So, if there's anyone else out there who feels like they're in a similar position, what strategies have you used to keep yourself motivated toward working on the project? I would really like to at least be able to work on this until I have 100% spec coverage, but I haven't committed source in months. Anyone out there who can help? | 2010/10/22 | [
"https://softwareengineering.stackexchange.com/questions/13870",
"https://softwareengineering.stackexchange.com",
"https://softwareengineering.stackexchange.com/users/3239/"
] | Chilling out might not be such a bad idea. Young babies take a lot of energy, so you might consider saying to yourself "OK, 3 month break from non-essential programming".
Take the time to relax while you can, and either wait for inspiration to strike (rather than trying to squeeze it out), or write down (in prose or code) some rough ideas on where you'd like the project to be, or how you'd like the code to look. | Since you don't want your opensource project to remain unfinished, I would suggest you to find someone who is willing to contribute to your project. So that at some point of time in the future, your project will get much more matured and you can always contribute it whenever you get time.
Family is much more important than any other things and any opensource project will get eventually succeed when multiple peoples started contributing to it. |
33,498 | I have read some time ago that [z] is the voiced counterpart of [s], as [d]-[t], [g]-[k], [b]-[p] and [v]-[f]. For all pairs except the first, I was able to consciously perceive it by starting to pronounce the unvoiced consonant, adding voice and realizing that I am now doing a voiced consonant.
However, when I start to produce a S (AFAIK a hissing sound) and add voice, I don't get a Z, but rather a hissed Z. AFAIK Z is the same sound a flying insect (eg bee) does and has no hiss on it. Or is that another phone? Am I the only one who perceives this difference between a voiced S and Z? I don't know if I'm mispronouncing [s] or [z], somehow affected by my native language (Brazilian Portuguese) or by some regionalism. | 2019/09/13 | [
"https://linguistics.stackexchange.com/questions/33498",
"https://linguistics.stackexchange.com",
"https://linguistics.stackexchange.com/users/24588/"
] | As far as I know, the symbols [s] and [z] typically refer to consonants with the same place of articulation, in terms of tongue and lip position (that exact place is different in different languages).
They are also both fricatives.
Differences in voicing often go with differences in pitch contours
------------------------------------------------------------------
It is also supposed to be common for there to be difference in the pitch transitions betwen voiced and voiceless consonants and the following vowels (as mentioned in this Language Log article by Mark Liberman: [Consonant effects on F0 of following vowels](https://languagelog.ldc.upenn.edu/nll/?p=12799), although it doesn't look at fricatives). I'm not sure how much of that (if any) is an automatic consequence of the difference in voice, but it seems that in some languages different pitches can become phonologized in syllables that originally had voiced or voiceless consonants.
Differences in voicing often go with differences in duration
------------------------------------------------------------
I've read that in many languages, [s] and [z] tend to have a difference of duration, with [s] being longer than [z]. If I remember correctly, this is the case for the /s/ and /z/ of English, German, and Navajo (in the latter two languages, the phonetic voicing of /z/ may be weak or even absent). But either sound can be prolonged, so I don't think that a difference in duration is generally essential for the contrast.
As Araucaria mentions, in certain contexts, the duration of the preceding vowel is related to the /s/ vs. /z/ contrast in English, and I think I've read that this is also detectable in German, but I don't think this is a universal phenomenon, and I'm not sure how common it is outside of Germanic languages.
The meaning of "fortis" and "lenis"
-----------------------------------
"Fortis" is a somewhat common term in literature, but I don't know what it means when talking about the phonetic qualities of sounds.\* Unlike Greg Lee, I can't directly hear or feel a difference in the amount of force when I pronounce [s] and [z]--the idea of "forceful articulation" feels more like a metaphor to me, like calling palatalized consonants "soft" or velarized consonants "hard".
Since it's come up in both Greg Lee's and Araucaria's answers, I thought I'd do more research on what "fortis" means. The preceding paragraph, which is what I wrote originally in this answer, is based on my inability to perceive this quality through personal introspection, as well as some statements in the [Wikipedia article](https://en.wikipedia.org/wiki/Fortis_and_lenis) that suggest that it is difficult or controversial to identify which measurable correlates of articulatory force (aside from voicing) are connected to phonological contrasts between consonants.
I found paper with some discussion that helped me a bit. "The Phonetics of Fortis and Lenis Consonants in Itunyoso Trique", by Christian T. DiCanio, has a section titled "Defining 'strength'" (1.2, p. 244-245). DiCanio says
>
> Malécot (1966) attempted to provide some phonetic grounding for differences in articulatory energy between consonants. He concluded that the “intra-buccal air pressure impulse” was the primary correlate of force of articulation, where stops [p] and [t] were produced with greater intra-buccal air pressure than stops [b] and [d]. [Footnote 3: Yet Malécot did not consider that differences in voicing would have significantly contributed to the lower oral pressure and amplitude values that he observed.]
>
>
>
(p. 244)
>
> There are three phonetic correlates which unambiguously reflect a stronger
> primary articulation. First, one expects stronger articulations to involve greater constriction between two articulators (Fougeron and Keating 1997, Keating et al. 2000, and Lavoie 2001). The only articulation that can be responsible for this is greater muscular tension between the articulators. Second, one expects stops to have louder bursts if they are produced with greater muscular tension. Articulators with more muscular tension will close and release more quickly, causing burst intensity to increase (Debrock 1977 and Kohler 1984). Related to this is the fact that increased stiffness among articulators will result in more abrupt formant transitions into and out of a consonant and faster falling and rising intensity contours (Debrock 1977). Thus, one usually expects consonants with increased articulatory strength to be abruptly timed relative to the surrounding segments. While differences in the constriction degree of consonants are usually measured using articulatory measures (e.g., electropalatography [Lavoie 2001]), both burst amplitude and formant and intensity transitions can be measured acoustically
>
>
>
(p. 245)
I don't know whether differences in any of these articulatory qualities have been found for a [s]/[z] pair in some language. DiCanio says burst intensity is relevant specifically for plosives, but [s] and [z] are fricatives.
I think lower constriction is a fairly common characteristic of the voiced counterparts to non-sibilant voiceless fricatives. E.g., in many languages, voiced "fricatives" like [β], [v], [ð], [ʝ], [ɣ], [ʁ] fairly often can be realized more like approximants than their voiceless counterparts [ɸ], [f], [θ], [ç], [x], [χ], and few languages have a contrast between voiced approximants and voiced fricatives at the same place of articulation: e.g. [v] and [ʋ] or [ɣ] and [ɰ]. But I'm not sure whether this is true of sibilant fricatives: I can't tell whether a less constricted, more approximant-y realization of [z] is possible. Diachronically, [z] can be subject to change into a rhotic approximant (a sound change called rhotacism), but the result of that change is no longer a sibilant consonant. | No, voice is not the only difference between /s/ and /z/. /s/ is fortis (forcefully articulated), while /z/ is lenis (weakly articulated). When I do your experiment, saying /s/ and adding voicing, without making other adjustments, I get exactly the result you report -- the /s/ made voiced doesn't sound anything like /z/ -- instead, it's an angry hornet sound. |
33,498 | I have read some time ago that [z] is the voiced counterpart of [s], as [d]-[t], [g]-[k], [b]-[p] and [v]-[f]. For all pairs except the first, I was able to consciously perceive it by starting to pronounce the unvoiced consonant, adding voice and realizing that I am now doing a voiced consonant.
However, when I start to produce a S (AFAIK a hissing sound) and add voice, I don't get a Z, but rather a hissed Z. AFAIK Z is the same sound a flying insect (eg bee) does and has no hiss on it. Or is that another phone? Am I the only one who perceives this difference between a voiced S and Z? I don't know if I'm mispronouncing [s] or [z], somehow affected by my native language (Brazilian Portuguese) or by some regionalism. | 2019/09/13 | [
"https://linguistics.stackexchange.com/questions/33498",
"https://linguistics.stackexchange.com",
"https://linguistics.stackexchange.com/users/24588/"
] | As far as I know, the symbols [s] and [z] typically refer to consonants with the same place of articulation, in terms of tongue and lip position (that exact place is different in different languages).
They are also both fricatives.
Differences in voicing often go with differences in pitch contours
------------------------------------------------------------------
It is also supposed to be common for there to be difference in the pitch transitions betwen voiced and voiceless consonants and the following vowels (as mentioned in this Language Log article by Mark Liberman: [Consonant effects on F0 of following vowels](https://languagelog.ldc.upenn.edu/nll/?p=12799), although it doesn't look at fricatives). I'm not sure how much of that (if any) is an automatic consequence of the difference in voice, but it seems that in some languages different pitches can become phonologized in syllables that originally had voiced or voiceless consonants.
Differences in voicing often go with differences in duration
------------------------------------------------------------
I've read that in many languages, [s] and [z] tend to have a difference of duration, with [s] being longer than [z]. If I remember correctly, this is the case for the /s/ and /z/ of English, German, and Navajo (in the latter two languages, the phonetic voicing of /z/ may be weak or even absent). But either sound can be prolonged, so I don't think that a difference in duration is generally essential for the contrast.
As Araucaria mentions, in certain contexts, the duration of the preceding vowel is related to the /s/ vs. /z/ contrast in English, and I think I've read that this is also detectable in German, but I don't think this is a universal phenomenon, and I'm not sure how common it is outside of Germanic languages.
The meaning of "fortis" and "lenis"
-----------------------------------
"Fortis" is a somewhat common term in literature, but I don't know what it means when talking about the phonetic qualities of sounds.\* Unlike Greg Lee, I can't directly hear or feel a difference in the amount of force when I pronounce [s] and [z]--the idea of "forceful articulation" feels more like a metaphor to me, like calling palatalized consonants "soft" or velarized consonants "hard".
Since it's come up in both Greg Lee's and Araucaria's answers, I thought I'd do more research on what "fortis" means. The preceding paragraph, which is what I wrote originally in this answer, is based on my inability to perceive this quality through personal introspection, as well as some statements in the [Wikipedia article](https://en.wikipedia.org/wiki/Fortis_and_lenis) that suggest that it is difficult or controversial to identify which measurable correlates of articulatory force (aside from voicing) are connected to phonological contrasts between consonants.
I found paper with some discussion that helped me a bit. "The Phonetics of Fortis and Lenis Consonants in Itunyoso Trique", by Christian T. DiCanio, has a section titled "Defining 'strength'" (1.2, p. 244-245). DiCanio says
>
> Malécot (1966) attempted to provide some phonetic grounding for differences in articulatory energy between consonants. He concluded that the “intra-buccal air pressure impulse” was the primary correlate of force of articulation, where stops [p] and [t] were produced with greater intra-buccal air pressure than stops [b] and [d]. [Footnote 3: Yet Malécot did not consider that differences in voicing would have significantly contributed to the lower oral pressure and amplitude values that he observed.]
>
>
>
(p. 244)
>
> There are three phonetic correlates which unambiguously reflect a stronger
> primary articulation. First, one expects stronger articulations to involve greater constriction between two articulators (Fougeron and Keating 1997, Keating et al. 2000, and Lavoie 2001). The only articulation that can be responsible for this is greater muscular tension between the articulators. Second, one expects stops to have louder bursts if they are produced with greater muscular tension. Articulators with more muscular tension will close and release more quickly, causing burst intensity to increase (Debrock 1977 and Kohler 1984). Related to this is the fact that increased stiffness among articulators will result in more abrupt formant transitions into and out of a consonant and faster falling and rising intensity contours (Debrock 1977). Thus, one usually expects consonants with increased articulatory strength to be abruptly timed relative to the surrounding segments. While differences in the constriction degree of consonants are usually measured using articulatory measures (e.g., electropalatography [Lavoie 2001]), both burst amplitude and formant and intensity transitions can be measured acoustically
>
>
>
(p. 245)
I don't know whether differences in any of these articulatory qualities have been found for a [s]/[z] pair in some language. DiCanio says burst intensity is relevant specifically for plosives, but [s] and [z] are fricatives.
I think lower constriction is a fairly common characteristic of the voiced counterparts to non-sibilant voiceless fricatives. E.g., in many languages, voiced "fricatives" like [β], [v], [ð], [ʝ], [ɣ], [ʁ] fairly often can be realized more like approximants than their voiceless counterparts [ɸ], [f], [θ], [ç], [x], [χ], and few languages have a contrast between voiced approximants and voiced fricatives at the same place of articulation: e.g. [v] and [ʋ] or [ɣ] and [ɰ]. But I'm not sure whether this is true of sibilant fricatives: I can't tell whether a less constricted, more approximant-y realization of [z] is possible. Diachronically, [z] can be subject to change into a rhotic approximant (a sound change called rhotacism), but the result of that change is no longer a sibilant consonant. | the voiced [z] requires a harmonic vibration to create a low frequency oscilation to modulate the voice and is, in my case, liable to fricate with as much of the tongue as possible. The voiceless [s] is just a noisy turbulence; any added voice is not necessarily harmonically modulated and the place of articulation may differ slightly, if only the tip of the tongue touches the alveolar ridge from below, or the dents.
The exact forming of the tongue can differ for channelling the air stream(s) differently in either case and not necessarily in the same manner.
To my surprise, closed teeth aren't needed to produce the sounds, although the vibration between the teeth is needed for me to satisfy the feeling that I fully formed the phoneme. There is a strong prejudice against lisping in German, which might somehow explain that (I think I recall being called to order exactly once), quite different from thSpanish. German also lost *th*, which Proto-Germanic presumably had. |
33,498 | I have read some time ago that [z] is the voiced counterpart of [s], as [d]-[t], [g]-[k], [b]-[p] and [v]-[f]. For all pairs except the first, I was able to consciously perceive it by starting to pronounce the unvoiced consonant, adding voice and realizing that I am now doing a voiced consonant.
However, when I start to produce a S (AFAIK a hissing sound) and add voice, I don't get a Z, but rather a hissed Z. AFAIK Z is the same sound a flying insect (eg bee) does and has no hiss on it. Or is that another phone? Am I the only one who perceives this difference between a voiced S and Z? I don't know if I'm mispronouncing [s] or [z], somehow affected by my native language (Brazilian Portuguese) or by some regionalism. | 2019/09/13 | [
"https://linguistics.stackexchange.com/questions/33498",
"https://linguistics.stackexchange.com",
"https://linguistics.stackexchange.com/users/24588/"
] | As far as I know, the symbols [s] and [z] typically refer to consonants with the same place of articulation, in terms of tongue and lip position (that exact place is different in different languages).
They are also both fricatives.
Differences in voicing often go with differences in pitch contours
------------------------------------------------------------------
It is also supposed to be common for there to be difference in the pitch transitions betwen voiced and voiceless consonants and the following vowels (as mentioned in this Language Log article by Mark Liberman: [Consonant effects on F0 of following vowels](https://languagelog.ldc.upenn.edu/nll/?p=12799), although it doesn't look at fricatives). I'm not sure how much of that (if any) is an automatic consequence of the difference in voice, but it seems that in some languages different pitches can become phonologized in syllables that originally had voiced or voiceless consonants.
Differences in voicing often go with differences in duration
------------------------------------------------------------
I've read that in many languages, [s] and [z] tend to have a difference of duration, with [s] being longer than [z]. If I remember correctly, this is the case for the /s/ and /z/ of English, German, and Navajo (in the latter two languages, the phonetic voicing of /z/ may be weak or even absent). But either sound can be prolonged, so I don't think that a difference in duration is generally essential for the contrast.
As Araucaria mentions, in certain contexts, the duration of the preceding vowel is related to the /s/ vs. /z/ contrast in English, and I think I've read that this is also detectable in German, but I don't think this is a universal phenomenon, and I'm not sure how common it is outside of Germanic languages.
The meaning of "fortis" and "lenis"
-----------------------------------
"Fortis" is a somewhat common term in literature, but I don't know what it means when talking about the phonetic qualities of sounds.\* Unlike Greg Lee, I can't directly hear or feel a difference in the amount of force when I pronounce [s] and [z]--the idea of "forceful articulation" feels more like a metaphor to me, like calling palatalized consonants "soft" or velarized consonants "hard".
Since it's come up in both Greg Lee's and Araucaria's answers, I thought I'd do more research on what "fortis" means. The preceding paragraph, which is what I wrote originally in this answer, is based on my inability to perceive this quality through personal introspection, as well as some statements in the [Wikipedia article](https://en.wikipedia.org/wiki/Fortis_and_lenis) that suggest that it is difficult or controversial to identify which measurable correlates of articulatory force (aside from voicing) are connected to phonological contrasts between consonants.
I found paper with some discussion that helped me a bit. "The Phonetics of Fortis and Lenis Consonants in Itunyoso Trique", by Christian T. DiCanio, has a section titled "Defining 'strength'" (1.2, p. 244-245). DiCanio says
>
> Malécot (1966) attempted to provide some phonetic grounding for differences in articulatory energy between consonants. He concluded that the “intra-buccal air pressure impulse” was the primary correlate of force of articulation, where stops [p] and [t] were produced with greater intra-buccal air pressure than stops [b] and [d]. [Footnote 3: Yet Malécot did not consider that differences in voicing would have significantly contributed to the lower oral pressure and amplitude values that he observed.]
>
>
>
(p. 244)
>
> There are three phonetic correlates which unambiguously reflect a stronger
> primary articulation. First, one expects stronger articulations to involve greater constriction between two articulators (Fougeron and Keating 1997, Keating et al. 2000, and Lavoie 2001). The only articulation that can be responsible for this is greater muscular tension between the articulators. Second, one expects stops to have louder bursts if they are produced with greater muscular tension. Articulators with more muscular tension will close and release more quickly, causing burst intensity to increase (Debrock 1977 and Kohler 1984). Related to this is the fact that increased stiffness among articulators will result in more abrupt formant transitions into and out of a consonant and faster falling and rising intensity contours (Debrock 1977). Thus, one usually expects consonants with increased articulatory strength to be abruptly timed relative to the surrounding segments. While differences in the constriction degree of consonants are usually measured using articulatory measures (e.g., electropalatography [Lavoie 2001]), both burst amplitude and formant and intensity transitions can be measured acoustically
>
>
>
(p. 245)
I don't know whether differences in any of these articulatory qualities have been found for a [s]/[z] pair in some language. DiCanio says burst intensity is relevant specifically for plosives, but [s] and [z] are fricatives.
I think lower constriction is a fairly common characteristic of the voiced counterparts to non-sibilant voiceless fricatives. E.g., in many languages, voiced "fricatives" like [β], [v], [ð], [ʝ], [ɣ], [ʁ] fairly often can be realized more like approximants than their voiceless counterparts [ɸ], [f], [θ], [ç], [x], [χ], and few languages have a contrast between voiced approximants and voiced fricatives at the same place of articulation: e.g. [v] and [ʋ] or [ɣ] and [ɰ]. But I'm not sure whether this is true of sibilant fricatives: I can't tell whether a less constricted, more approximant-y realization of [z] is possible. Diachronically, [z] can be subject to change into a rhotic approximant (a sound change called rhotacism), but the result of that change is no longer a sibilant consonant. | The presence or absence of vocal fold vibration is the most widely used distinction to notionally differentiate so-called fortis and lenis consonants. However, it is not the only one, and for this reason, the following transcriptions do not indicate the same thing:
* b̥e̞d̥
* pe̞t
Fortis (notionally unvoiced) consonants generally differ from lenis ones in the following ways:
* They require greater exertion of the lungs, resulting in higher intra-oral pressure
* They are generally of longer duration
* When occurring in the coda of a syllable, they may have the effect—where a contrast between fortis and lenis pairs is avaliable—of clipping the vocalic elements of the syllable.
* They may cause devoicing of a following vowel (known as aspiration). |
427,195 | In reference to [this elaborate answer](https://physics.stackexchange.com/a/119214/20427) by @DanielSank, I would like to pose the following question(s) in order to verify my understanding of the subject matter--in particular, that of the nature of uncertainty and measurements in quantum mechanics. For context, I would like to quote the most relevant paragraph (most relevant with respect to my question) from the linked answer:
>
> *The crucial thing here is that you never ever measure anything to infinite accuracy, so the wave functions resulting from your measurement are not exact eigen-states of what you think is the measurement operator. This is not just "experimental dirtiness". This is a fundamentally important aspect of QM which you should keep near your mental centre as you learn more.*
>
>
>
Now, in my understanding, we never ever make a measurement that can produce an exact eigenstate of, say, the momentum operator because there *is no* normalizable (and thus, physically realizable) eigenstate of the momentum operator. And that, in turn, is the reason why we can never ever measure the momentum precisely--no matter how arbitrarily small we can make the error-bars nonetheless. Any attempt at measuring the momentum will never reduce the given state to a momentum eigenstate but only to a superposition of multiple momentum eigenstates--no matter how closely distributed (i.e. spiked near some particular eigenstate) those contributing eigenstates might be. Thus, in the measurement of the momentum, we will always be endowed with an uncertainty of the scale of the width of that spiked superposition of momentum eigenstates.
Now, all of that is fine and fundamental and **not** a result of the experimental dirtiness--but in the cases where there *are* physically realizable eigenstates, any inability of a ''measurement'' to produce a true eigenstate must be credited to the experimental dirtiness--I think. For example, for a Hermitian operator with discrete non-generate spectrum, there seems to be no way for a measurement to produce anything but a specific true eigenstate. In such a case, there would certainly be an indeterminacy in the outcome of the measurement when one starts with a generic state which can be a superposition of more than one eigenstates (and this would lead to an uncertainty in the measurement in the sense that when we are measuring the same observable over an ensemble of identically prepared states, we will not get the same value because different measurements would pick out different eigenstates--generically speaking) but this indeterminacy (and resulting uncertainty of the kind I described) is different from the uncertainty in the measurement of an observable corresponding to an operator whose eigenstates are simply not physical. In particular, once the measurement is made on this kind of an operator which admits discrete non-degenerate eigenstates, all the subsequent measurements are guaranteed to yield the exact same outcome with literally $100\%$ probability except for the experimental dirtiness. And this is the reason I think it is not quite right to say that "you never ever measure anything to infinite accuracy" in quantum mechanics (for example, we always measure the exact spin of an electron to my understanding).
Thus, my core question is that is it correct that it is not right to say that we never ever measure anything to infinite accuracy in quantum mechanics? Or at least can we assert that there are certain operators for which any uncertainty in the measurement must be credited to the experimental dirtiness? | 2018/09/06 | [
"https://physics.stackexchange.com/questions/427195",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/87745/"
] | >
> The crucial thing is that we never measure anything to infinite accuracy.
>
>
>
This is true but it has nothing to do with classical or quantum physics and has purely to do with the practicalities of measurement. We never measure anything exactly and there is always a degree of error.
>
> Sp the wave functions resulting from your measurement are not exact eigenstates of what you think is your measurement operator.
>
>
>
However, this does not imply that nature is not exact. Classically speaking, nature is exact. Notice, here, that this is an epistemic statement as it should be. When we think about nature we think through a theory of nature - no matter how naive or sophisticated.
Likewise, in QM, the wave function to be measured is exact. But it's ontological status is still under discussion. Even as an amplitude whose square is probability, it is - theoretically speaking - exact. To be honest, the nomenclature to describe the various kinds of epistemic and ontological commitments here - despite a century of thinking over it - is all over the place. No wonder people are still confused about it.
For instance, people still say off the bat that QM is strange and bizarre. But personally, I find the notion of a purely deterministic nature strange and bizarre. This is hardly ever noted. | Conceptually it seems there is a difference here between conjugate observable pairs (non commuting ones) such as momentum and position, and other observables with no conjugate, such as spin.
One cannot in principle give an exact value to an observable belonging to the first class, to which the uncertainty principle (a dispersion relation between both ends of a Fourier transform) apply. This translates experimentally in limitations such as the amount of energy required for a position measurement, which increases with the wanted precision. On the other hand one can measure a spin component exactly (e.g. Stern-Gerlach).
Conjugate pairs of observables directly come from Hamiltonian mechanics and reflect the symplectic structure of phase space. They are intimately associated with phase space being continuous. I am no expert in that domain but I would guess that this is what breaks down in QM, and that in fact there is no actual physical continuity (which comes anyway with its own problems in terms of infinities, as pointed out by The\_Sympathizer answer), but a discrete structure instead, at least when measurements are involved. This is measurement problem territory though, and still an open question as far as I know.
One intriguing point is that conjugate variables are reciprocal derivatives of the action. The action is also driving quantum interference in a very general way as seen in the path integral formulation. I am not clear on the link beetween these aspects of action, but it seems to point towards the idea that the phase space of a quantum system in-between measurements (measurements here considered as boundary conditions in the path integral view), although mathematically useful and well-defined, is in fact not a really helpful concept in understanding intuitively the nature of the system evolution. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Quintessentially I think that the problem is that you've got a cheap tripod. In order to have a smooth pan and tilt you need to get an expensive tripod head suitable for film and video work.
Because the cheaper heads work on friction you can make them move smoother using oils or other lubricants, however this will also prevent them from locking up completely meaning that you may get some drift at some point or even, if unlucky, render the head unusable until cleaned.
There isn't really a way around the problem as far as I know. Cheap heads are stiff and jerky while expensive heads aren't. | Is this when the controls (knobs/handles) are quite loose? Is it a ball head, or a pan/tilt type head?
Your best bet would be to try to disassemble it, if possible, and clean it. If you can't get it apart, but can access some surfaces, clean them with a microfibre cloth.
You can put a small amount of oil or silicon lubricant on it, but that may cause further problems
* may attract more dust/dirt, which would adhere to the oil
* may make it harder to lock down in place, so the head slips after you tighten it
If this is a large tripod intended for a large SLR and you have a small point and shoot, it may be that the lack of weight makes it hard to make micro adjustments like you want. If the head can be replaced, keep the legs and buy a small ball head for your P&S. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Force some talcum powder (or better yet, powdered graphite) into the friction surfaces of the head. This works like little ball bearings for the plastic-on-plastic rubbing of a cheap tripod head. Don't use oil, it just makes it worse.
I have a $25 Amazon Basics tripod, and this made a big improvement. I drilled a little hole in the panning head to force the talcum powder in, but maybe I could have just rubbed it into the cracks. It made a big improvement in the stiction and judder. The only downside is that it now smells like baby powder. | Is this when the controls (knobs/handles) are quite loose? Is it a ball head, or a pan/tilt type head?
Your best bet would be to try to disassemble it, if possible, and clean it. If you can't get it apart, but can access some surfaces, clean them with a microfibre cloth.
You can put a small amount of oil or silicon lubricant on it, but that may cause further problems
* may attract more dust/dirt, which would adhere to the oil
* may make it harder to lock down in place, so the head slips after you tighten it
If this is a large tripod intended for a large SLR and you have a small point and shoot, it may be that the lack of weight makes it hard to make micro adjustments like you want. If the head can be replaced, keep the legs and buy a small ball head for your P&S. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Is this when the controls (knobs/handles) are quite loose? Is it a ball head, or a pan/tilt type head?
Your best bet would be to try to disassemble it, if possible, and clean it. If you can't get it apart, but can access some surfaces, clean them with a microfibre cloth.
You can put a small amount of oil or silicon lubricant on it, but that may cause further problems
* may attract more dust/dirt, which would adhere to the oil
* may make it harder to lock down in place, so the head slips after you tighten it
If this is a large tripod intended for a large SLR and you have a small point and shoot, it may be that the lack of weight makes it hard to make micro adjustments like you want. If the head can be replaced, keep the legs and buy a small ball head for your P&S. | My benro has a dial on the side that if I loosen it, it also loosens the ball inside the head. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Quintessentially I think that the problem is that you've got a cheap tripod. In order to have a smooth pan and tilt you need to get an expensive tripod head suitable for film and video work.
Because the cheaper heads work on friction you can make them move smoother using oils or other lubricants, however this will also prevent them from locking up completely meaning that you may get some drift at some point or even, if unlucky, render the head unusable until cleaned.
There isn't really a way around the problem as far as I know. Cheap heads are stiff and jerky while expensive heads aren't. | There are usually screws which restrict motion in different directions, perhaps one of these is a wee bit too tight? Is the movement smooth or jerky? Try loosening the fixing screws a little bit at a time to see if that helps.
What brand of tripod? One of the differences between good and bad (i.e. expensive and not-) tripods is ease and controlability (sp?) during adjustment. If it is a cheap tripod you may have discovered why. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Force some talcum powder (or better yet, powdered graphite) into the friction surfaces of the head. This works like little ball bearings for the plastic-on-plastic rubbing of a cheap tripod head. Don't use oil, it just makes it worse.
I have a $25 Amazon Basics tripod, and this made a big improvement. I drilled a little hole in the panning head to force the talcum powder in, but maybe I could have just rubbed it into the cracks. It made a big improvement in the stiction and judder. The only downside is that it now smells like baby powder. | There are usually screws which restrict motion in different directions, perhaps one of these is a wee bit too tight? Is the movement smooth or jerky? Try loosening the fixing screws a little bit at a time to see if that helps.
What brand of tripod? One of the differences between good and bad (i.e. expensive and not-) tripods is ease and controlability (sp?) during adjustment. If it is a cheap tripod you may have discovered why. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | There are usually screws which restrict motion in different directions, perhaps one of these is a wee bit too tight? Is the movement smooth or jerky? Try loosening the fixing screws a little bit at a time to see if that helps.
What brand of tripod? One of the differences between good and bad (i.e. expensive and not-) tripods is ease and controlability (sp?) during adjustment. If it is a cheap tripod you may have discovered why. | My benro has a dial on the side that if I loosen it, it also loosens the ball inside the head. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Quintessentially I think that the problem is that you've got a cheap tripod. In order to have a smooth pan and tilt you need to get an expensive tripod head suitable for film and video work.
Because the cheaper heads work on friction you can make them move smoother using oils or other lubricants, however this will also prevent them from locking up completely meaning that you may get some drift at some point or even, if unlucky, render the head unusable until cleaned.
There isn't really a way around the problem as far as I know. Cheap heads are stiff and jerky while expensive heads aren't. | Force some talcum powder (or better yet, powdered graphite) into the friction surfaces of the head. This works like little ball bearings for the plastic-on-plastic rubbing of a cheap tripod head. Don't use oil, it just makes it worse.
I have a $25 Amazon Basics tripod, and this made a big improvement. I drilled a little hole in the panning head to force the talcum powder in, but maybe I could have just rubbed it into the cracks. It made a big improvement in the stiction and judder. The only downside is that it now smells like baby powder. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Quintessentially I think that the problem is that you've got a cheap tripod. In order to have a smooth pan and tilt you need to get an expensive tripod head suitable for film and video work.
Because the cheaper heads work on friction you can make them move smoother using oils or other lubricants, however this will also prevent them from locking up completely meaning that you may get some drift at some point or even, if unlucky, render the head unusable until cleaned.
There isn't really a way around the problem as far as I know. Cheap heads are stiff and jerky while expensive heads aren't. | My benro has a dial on the side that if I loosen it, it also loosens the ball inside the head. |
18,599 | Few months back I purchased a second hand tripod.
Later on I noticed that the head *(which holds the camera)* of the tripod doesn't move freely.
I mean I have to apply some pressure to make it move left and right, and even when it moves left/right it jumps some fixed *x* degrees, i.e I can't make it move *x+1* degree, it moves straightaway to *x+5* degrees.
I don't know whether this is normal or not, but this is very annoying.
Is there a way that ***I*** can fix it? Perhaps by oiling at some right spots? | 2011/12/30 | [
"https://photo.stackexchange.com/questions/18599",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/5205/"
] | Force some talcum powder (or better yet, powdered graphite) into the friction surfaces of the head. This works like little ball bearings for the plastic-on-plastic rubbing of a cheap tripod head. Don't use oil, it just makes it worse.
I have a $25 Amazon Basics tripod, and this made a big improvement. I drilled a little hole in the panning head to force the talcum powder in, but maybe I could have just rubbed it into the cracks. It made a big improvement in the stiction and judder. The only downside is that it now smells like baby powder. | My benro has a dial on the side that if I loosen it, it also loosens the ball inside the head. |
24,062 | I'm making an hibiscus-tea mead. The tea/honey mixture had a really nice red color. But after I added the yeast nutrient, the color turned black. The nutrient I'm using is LD Carlson Yeast Nutrient (Food grade urea and diammonium phosphate).
Since I had some tea left, I tried adding some yeast nutrient to a cup of pure hibiscus tea. As expected, the color changed. Attached some pictures of my experiment:
[](https://i.stack.imgur.com/vrj9as.jpg)[](https://i.stack.imgur.com/lnMs8s.jpg)
Anybody had a similar experience? I would like to know if the final product will be black, or it will change back to red during fermentation.
Thanks!
**Update**: After some days the color turned back to red. So don't worry if this happens to you. Also, after several months aging, the color red is gone. | 2019/03/29 | [
"https://homebrew.stackexchange.com/questions/24062",
"https://homebrew.stackexchange.com",
"https://homebrew.stackexchange.com/users/17115/"
] | Hibiscus contains hydroxycitric acid. I suspect it had a reaction to metal elements in the yeast nutrient.
The product looks like iron chloride in solution to me. | I have found that the colour of Hybiscus is pH sensitive. At low pH it is red and at higher pH it will turn purple. |
24,062 | I'm making an hibiscus-tea mead. The tea/honey mixture had a really nice red color. But after I added the yeast nutrient, the color turned black. The nutrient I'm using is LD Carlson Yeast Nutrient (Food grade urea and diammonium phosphate).
Since I had some tea left, I tried adding some yeast nutrient to a cup of pure hibiscus tea. As expected, the color changed. Attached some pictures of my experiment:
[](https://i.stack.imgur.com/vrj9as.jpg)[](https://i.stack.imgur.com/lnMs8s.jpg)
Anybody had a similar experience? I would like to know if the final product will be black, or it will change back to red during fermentation.
Thanks!
**Update**: After some days the color turned back to red. So don't worry if this happens to you. Also, after several months aging, the color red is gone. | 2019/03/29 | [
"https://homebrew.stackexchange.com/questions/24062",
"https://homebrew.stackexchange.com",
"https://homebrew.stackexchange.com/users/17115/"
] | Hibiscus contains hydroxycitric acid. I suspect it had a reaction to metal elements in the yeast nutrient.
The product looks like iron chloride in solution to me. | Your nutrient contained phosphate. Most phosphate compounds (besides phosphoric acid and ammonium phosphate) are insoluble. Part of what happened is the phosphate reacting chemically with other ions in the mead, causing the darkening effect which then settled out over time. So your update above makes perfect sense.
David M. Taylor
B.S. Chemical Engineering
Michigan Tech
Class of 1997 |
51,140 | What happened to the SpaceX Starship SN11?
------------------------------------------
---
As per the live streams held on YouTube, I want to know what really happened to SpaceX Starship SN11
The live streams show a lot of smoke and others show some camera footage, even others say it blew up in the sky.
And other people even say that there was an issue with the 2nd raptor engine
What is really going on here?
* Did it blow up in the sky?
* Did it blow up on the launchpad?
Why did it crash?
-----------------
1. **Computer code error**
SpaceX uses computers that run on code(correct me, anyone, if I'm wrong
here)and the SN10 flight was successful (even though it came down with quite a
bump!) so we can assume that SpaceX used the same code but altered it a bit so
they instructed the computer to reduce the velocity so it wouldn't come down
like SN10.
But there was an error with the code
2. **Raptor/s issue/s**
Or we can assume that the computer ran the code correctly, but there was a
raptor issue as shown by the fire here
[](https://i.stack.imgur.com/LyxCU.png)
3. **It was caused by the fog**
Or we can also assume that everything went well but the landing wasn't
possible due to the fog. The computer could not calculate and made a botched
landing attempt
4. **Or there was/were some other issue/s**
***So which of the four was it?***
1. Computer code error
2. Raptor issues
3. Bad weather caused by the fog
4. Some other problem/s
Other suggestions and answers other than the given 4 are also welcome!
Please note that i prefer detailed answers | 2021/03/30 | [
"https://space.stackexchange.com/questions/51140",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/39182/"
] | Looks like SN11 most probably crashed.
[](https://i.stack.imgur.com/g7aOE.jpg)
“At least the crater is in the right place!”
...
“Something significant happened shortly after landing burn start. Should know what it was once we can examine the **bits** later today.”
My emphasis on "bits", taking it to mean (destroyed) bits of SN11. Looks like we'll know more about what actually happened perhaps later today. | A recent [tweet from Elon](https://twitter.com/elonmusk/status/1379022709737275393) says that:
>
> Ascent phase, transition to horizontal & control during free fall were
> good.
>
>
> A (relatively) small CH4 leak led to fire on engine 2 & fried part of
> avionics, causing hard start attempting landing burn in CH4 turbopump.
>
>
> This is getting fixed 6 ways to Sunday.
>
>
> |
51,140 | What happened to the SpaceX Starship SN11?
------------------------------------------
---
As per the live streams held on YouTube, I want to know what really happened to SpaceX Starship SN11
The live streams show a lot of smoke and others show some camera footage, even others say it blew up in the sky.
And other people even say that there was an issue with the 2nd raptor engine
What is really going on here?
* Did it blow up in the sky?
* Did it blow up on the launchpad?
Why did it crash?
-----------------
1. **Computer code error**
SpaceX uses computers that run on code(correct me, anyone, if I'm wrong
here)and the SN10 flight was successful (even though it came down with quite a
bump!) so we can assume that SpaceX used the same code but altered it a bit so
they instructed the computer to reduce the velocity so it wouldn't come down
like SN10.
But there was an error with the code
2. **Raptor/s issue/s**
Or we can assume that the computer ran the code correctly, but there was a
raptor issue as shown by the fire here
[](https://i.stack.imgur.com/LyxCU.png)
3. **It was caused by the fog**
Or we can also assume that everything went well but the landing wasn't
possible due to the fog. The computer could not calculate and made a botched
landing attempt
4. **Or there was/were some other issue/s**
***So which of the four was it?***
1. Computer code error
2. Raptor issues
3. Bad weather caused by the fog
4. Some other problem/s
Other suggestions and answers other than the given 4 are also welcome!
Please note that i prefer detailed answers | 2021/03/30 | [
"https://space.stackexchange.com/questions/51140",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/39182/"
] | >
> What happened to the SpaceX Starship SN11?
>
>
>
It's fairly apparent that what did happen is that it exploded in the fog during its descent. It's far too early to know why this happened. Lots of people who were there reported seeing falling debris. Eric Berger at arstechnica.com [wrote](https://arstechnica.com/science/2021/03/spacex-loses-another-starship-prototype-as-landing-sequence-fails/)
>
> All we really know for sure is that at 5 minutes and 47 seconds into the flight, one of Starship's three Raptor engines relit to begin the final landing sequence, and then the engine-bay camera cut out in SpaceX's webcast. Contact with the vehicle was lost, at least in terms of live video pictures. Shortly after this, pieces of the Starship vehicle began raining down on the launch site, and there were reports of a series of small explosions.
>
>
>
Eric writes cautiously, and he rarely speculates or conveys unfounded rumors. (There are rumors galore on this.) Eric did report on one photographer he knows (Eric knows lots of people) who was on the scene and saw the thick sea fog. The photographer drove inland a ways where he might have a better view when the vehicle ascended above the fog. He did have that view; the linked article shows pictures taken by that photographer of the vehicle ascending above the fog and performing its belly flop. (Note: I am not posting those images here because those pictures are copyrighted by a professional photographer.)
Eric did make one implicit speculation in the article:
>
> It is not clear whether the vehicle's flight termination system was activated to destroy the Starship before it veered off course. However, the remnants of the vehicle landed near their intended target.
>
>
>
The vehicle's automated flight termination system certainly is a possible culprit; the AFTS's one and only one purpose to make the launch vehicle explode. There are however many other possible causes for a launch vehicle undergoing rapid unintentional disassembly. | A recent [tweet from Elon](https://twitter.com/elonmusk/status/1379022709737275393) says that:
>
> Ascent phase, transition to horizontal & control during free fall were
> good.
>
>
> A (relatively) small CH4 leak led to fire on engine 2 & fried part of
> avionics, causing hard start attempting landing burn in CH4 turbopump.
>
>
> This is getting fixed 6 ways to Sunday.
>
>
> |
51,140 | What happened to the SpaceX Starship SN11?
------------------------------------------
---
As per the live streams held on YouTube, I want to know what really happened to SpaceX Starship SN11
The live streams show a lot of smoke and others show some camera footage, even others say it blew up in the sky.
And other people even say that there was an issue with the 2nd raptor engine
What is really going on here?
* Did it blow up in the sky?
* Did it blow up on the launchpad?
Why did it crash?
-----------------
1. **Computer code error**
SpaceX uses computers that run on code(correct me, anyone, if I'm wrong
here)and the SN10 flight was successful (even though it came down with quite a
bump!) so we can assume that SpaceX used the same code but altered it a bit so
they instructed the computer to reduce the velocity so it wouldn't come down
like SN10.
But there was an error with the code
2. **Raptor/s issue/s**
Or we can assume that the computer ran the code correctly, but there was a
raptor issue as shown by the fire here
[](https://i.stack.imgur.com/LyxCU.png)
3. **It was caused by the fog**
Or we can also assume that everything went well but the landing wasn't
possible due to the fog. The computer could not calculate and made a botched
landing attempt
4. **Or there was/were some other issue/s**
***So which of the four was it?***
1. Computer code error
2. Raptor issues
3. Bad weather caused by the fog
4. Some other problem/s
Other suggestions and answers other than the given 4 are also welcome!
Please note that i prefer detailed answers | 2021/03/30 | [
"https://space.stackexchange.com/questions/51140",
"https://space.stackexchange.com",
"https://space.stackexchange.com/users/39182/"
] | We know for certain this was a mid-air explosion. Twitter user [RGVAerialPhotograph](https://twitter.com/RGVaerialphotos/status/1377294449018081280/photo/1), photo linked but not included here because I'm unsure of copyright, shows the pad is clearly intact, and the debris is spread to the north of the pad. I've also had it on good word from someone who would know that it wasn't the FTS system. It seems like whatever happened it was a true explosion, so mixed oxidizer and fuel with a spark lead to an explosion, in something that is roughly mixed correctly.
We know the nose cone is mostly intact (But unzipped), the tank is completely shredded. We know that the event happened when one of the engines attempted to ignite, most likely the third. The remains of the nose cone landed very close to the landing pad, so it was probably mostly on target.
We also know that the CH4 header tank, right in the middle of the rocket, is pretty much in two widely separated pieces. It therefore seems very likely that the first explosion happened there.
Whatever happened must have happened mostly from the south. The orientation of Starship when falling is the nose points east, the engine point west. Incidentally, the FTS is on the side pointing downward during the fall, which would not explain the debris cloud preferentially being north.
All of this being the case, I would say some oxygen somehow worked its way in to the header tank. That oxygen likely reached the engine, causing an explosion which traced its way upward to the header tank, that completely blew up. | A recent [tweet from Elon](https://twitter.com/elonmusk/status/1379022709737275393) says that:
>
> Ascent phase, transition to horizontal & control during free fall were
> good.
>
>
> A (relatively) small CH4 leak led to fire on engine 2 & fried part of
> avionics, causing hard start attempting landing burn in CH4 turbopump.
>
>
> This is getting fixed 6 ways to Sunday.
>
>
> |
236,053 | I want to trigger a workflow using a button from InfoPath form based on a choice selected vallue in the form. | 2018/02/14 | [
"https://sharepoint.stackexchange.com/questions/236053",
"https://sharepoint.stackexchange.com",
"https://sharepoint.stackexchange.com/users/71553/"
] | Workflows can run on item add and item update.
To achieve ur requirements, you can set a field value on clicking that button and have to save that value. And in the start of the workflow use a if condition which will use the filed value which has changed on clicking the button. | List workflow is initiated either when list item is created or updated, for your case as a workaround you can use if statement in your workflow and check on the boolean field value, if the condition is true the workflow does the required actions or else end the workflow. |
227,220 | I just started playing Fez for the first time, and I've heard there is a secret code that can be seen throughout the game.
I'd like to know what the codes are saying, but I'm leery of looking it up in case I can figure it out on my own. Also, I don't want to spoil things if the coded text is more of a spoiler/director's commentary sort of thing.
Can this code be learned as you make your way through the game, or is it something that has to be rigorously decoded/googled to understand? Also, is it better to leave it a mystery until the second play-through?
Thank you for not posting spoilers. | 2015/07/09 | [
"https://gaming.stackexchange.com/questions/227220",
"https://gaming.stackexchange.com",
"https://gaming.stackexchange.com/users/117774/"
] | Yes, the code can be learned through the game. However, it is not an in game mechanism, and sentences won't be automatically translated for you.
There is a special room in the game that should help you decipher the alphabet.
Deciphering this alphabet is required if you wish to finish the game to full completion, and can be done on the first playthrough. | There are 3 codes in Fez. There is the numbers code, the letters code and a third code, which I won't say much about so that you can discover it yourself. The numbers code and the third code are required to finish the game, but the letters code (alphabet) is not, it just gives you access to some backstory. All 3 codes can be deciphered before starting a New Game+. |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | This is a fairly straightforward reference to the teaching that once saved, God works on us to make us more Christ-like. ([More here](http://www.openbible.info/topics/becoming_more_like_christ)) This is a very common belief, in [mainstream Christianity](http://www.turnbacktogod.com/being-more-christ-like/), and in not-so-mainstream denominations, such as the [LDS Church](https://www.lds.org/youth/learn/ap/becoming-more-christlike?lang=eng). It is also known as [Sanctification](http://www.theopedia.com/Sanctification).
>
> **Progressive sanctification**
>
>
> "Indeed, the more sanctified the person is, the more conformed he is
> to the image of his Savior, the more he must recoil against every lack
> of conformity to the holiness of God. The deeper his apprehension of
> the majesty of God, the greater the intensity of his love to God, the
> more persistent his yearning for the attainment of the prize of the
> high calling of God in Christ Jesus, the more conscious will he be of
> the gravity of the sin that remains and the more poignant will be his
> detestation of it....Was this not the effect in all the people of God
> as they came into closer proximity to the revelation of God’s
> holiness." -John Murray, Redemption Accomplished and Applied
>
>
>
The first paragraph you quoted alludes to the experience that in the beginning of our Christian walk, we all think about the rules a lot. We think about avoiding this sin, trying to increase this positive trait. As we become more conformed to the image of Christ, these things become more natural. Our minds become more confirmed to the image of Christ through God's continuous work on us, and our own submission to His will that we no longer think about nit-picky rules, but instead, simply live in a way that is more Christ-like. We don't think about it, we don't verbalize it, it becomes who we are.
In the end, we're not thinking about being good, we're too busy focusing on Christ Himself, the source of all goodness.
The last few sentences are indicating that Lewis didn't think he'd reached the same point in his walk as other, who were more closely confirmed to God's image than he was.
Taking this a step further, it is a quite lovely way of saying that Christianity isn't about rules, regulations, or morality, it's about Christ, and our relationship to and with Him. We are "good" (or at least as good as we can be) because of the work He does in us, not because of our obedience to rules, but because of who we are *through* Him. Our morality is based on our love for Him. This is discussed [here](http://www.christinyou.net/pages/Xnotmor.html). | Lewis' point is that while many Christians are focussed largely on the question of how they might avoid sin, and how they might be more moral, those who are more advanced in the faith are not thinking about those things at all. As they come to realize more completely that Jesus has paid the price of forgiveness for them, they stop thinking about those things. Instead they focus on Jesus, "the source from which it comes". They think about him, and about their relationship with him, and what he has done, and his love for them, and their love for him. In doing so they unconsciously still do the things that Jesus wants them to (what we call 'goodness'). In the very last line he opines that at this stage the Christian is usually close to passing on to be with Jesus and no longer in this world. |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | Lewis' point is that while many Christians are focussed largely on the question of how they might avoid sin, and how they might be more moral, those who are more advanced in the faith are not thinking about those things at all. As they come to realize more completely that Jesus has paid the price of forgiveness for them, they stop thinking about those things. Instead they focus on Jesus, "the source from which it comes". They think about him, and about their relationship with him, and what he has done, and his love for them, and their love for him. In doing so they unconsciously still do the things that Jesus wants them to (what we call 'goodness'). In the very last line he opines that at this stage the Christian is usually close to passing on to be with Jesus and no longer in this world. | I'd hope that Lewis would give me at least a passing mark if I suggested that it was reasonably well summarised by this verse from a hymn by Helen Lemmel.
>
> Turn your eyes upon Jesus
>
> Look full in his wonderful face
>
> And the things of earth will grow strangely dim.
>
> In the light of his glory and grace.
>
>
>
[Lyrics here](http://library.timelesstruths.org/music/Turn_Your_Eyes_upon_Jesus/)
Hillsong [**doing a reasonable job of imparting the impression of**](https://www.youtube.com/watch?v=czxd5oa-gi0)
" ... They are too busy looking at the source from which it comes. But this is near the stage where the road passes over the rim of our world. No one's eyes can see very far beyond that ..." |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | A man focused on loving others instead of himself will see the many rules shrink to but one. As Romans 13 says:
>
> 8 Let no debt remain outstanding, except the continuing debt to love
> one another, for whoever loves others has fulfilled the law. 9 The
> commandments, “You shall not commit adultery,” “You shall not murder,”
> “You shall not steal,” “You shall not covet,” and whatever other
> command there may be, are summed up in this one command: “Love your
> neighbor as yourself.” 10 Love does no harm to a neighbor. Therefore
> love is the fulfillment of the law.
>
>
>
An analogy I once heard was about flying an aircraft. There are many rules that are followed by the crew and imposed upon the passengers in order to make the flight safe. However, those rules have nothing to do with the purpose of flying. The purpose of flying is to get to your vacation spot, business meeting, wedding, or what-not. As you mature in the faith, the goal of your faith becomes more important, and you get less tripped up by the steps you need to take to get there. | Lewis' point is that while many Christians are focussed largely on the question of how they might avoid sin, and how they might be more moral, those who are more advanced in the faith are not thinking about those things at all. As they come to realize more completely that Jesus has paid the price of forgiveness for them, they stop thinking about those things. Instead they focus on Jesus, "the source from which it comes". They think about him, and about their relationship with him, and what he has done, and his love for them, and their love for him. In doing so they unconsciously still do the things that Jesus wants them to (what we call 'goodness'). In the very last line he opines that at this stage the Christian is usually close to passing on to be with Jesus and no longer in this world. |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | This is a fairly straightforward reference to the teaching that once saved, God works on us to make us more Christ-like. ([More here](http://www.openbible.info/topics/becoming_more_like_christ)) This is a very common belief, in [mainstream Christianity](http://www.turnbacktogod.com/being-more-christ-like/), and in not-so-mainstream denominations, such as the [LDS Church](https://www.lds.org/youth/learn/ap/becoming-more-christlike?lang=eng). It is also known as [Sanctification](http://www.theopedia.com/Sanctification).
>
> **Progressive sanctification**
>
>
> "Indeed, the more sanctified the person is, the more conformed he is
> to the image of his Savior, the more he must recoil against every lack
> of conformity to the holiness of God. The deeper his apprehension of
> the majesty of God, the greater the intensity of his love to God, the
> more persistent his yearning for the attainment of the prize of the
> high calling of God in Christ Jesus, the more conscious will he be of
> the gravity of the sin that remains and the more poignant will be his
> detestation of it....Was this not the effect in all the people of God
> as they came into closer proximity to the revelation of God’s
> holiness." -John Murray, Redemption Accomplished and Applied
>
>
>
The first paragraph you quoted alludes to the experience that in the beginning of our Christian walk, we all think about the rules a lot. We think about avoiding this sin, trying to increase this positive trait. As we become more conformed to the image of Christ, these things become more natural. Our minds become more confirmed to the image of Christ through God's continuous work on us, and our own submission to His will that we no longer think about nit-picky rules, but instead, simply live in a way that is more Christ-like. We don't think about it, we don't verbalize it, it becomes who we are.
In the end, we're not thinking about being good, we're too busy focusing on Christ Himself, the source of all goodness.
The last few sentences are indicating that Lewis didn't think he'd reached the same point in his walk as other, who were more closely confirmed to God's image than he was.
Taking this a step further, it is a quite lovely way of saying that Christianity isn't about rules, regulations, or morality, it's about Christ, and our relationship to and with Him. We are "good" (or at least as good as we can be) because of the work He does in us, not because of our obedience to rules, but because of who we are *through* Him. Our morality is based on our love for Him. This is discussed [here](http://www.christinyou.net/pages/Xnotmor.html). | He seems to be describing the bliss of faith where the knowledge of good and evil does not dominate our awareness. He does it kind of poetically. As we are sinful and not absolutely sure of our forgiveness, due to want of faith, the glory of Christ is hard to look at directly. We do not have such strong faith on this side of heaven not to be frequently taking our spiritual temperature. We are not so confident in the power of Christ's atonement as we aught to be. Therefore we still walk about thinking our sins are carried by ourselves and this makes us feel guilty and uneasy. The kingdom of heaven takes us to another world where sin and its horrors are no longer on our mind. Unfortunately we experience this grace imperfectly in this world. This does not mean that we can't peer into the land of grace by faith. Lewis just admits its heavenly and that others can see it better than he can. |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | This is a fairly straightforward reference to the teaching that once saved, God works on us to make us more Christ-like. ([More here](http://www.openbible.info/topics/becoming_more_like_christ)) This is a very common belief, in [mainstream Christianity](http://www.turnbacktogod.com/being-more-christ-like/), and in not-so-mainstream denominations, such as the [LDS Church](https://www.lds.org/youth/learn/ap/becoming-more-christlike?lang=eng). It is also known as [Sanctification](http://www.theopedia.com/Sanctification).
>
> **Progressive sanctification**
>
>
> "Indeed, the more sanctified the person is, the more conformed he is
> to the image of his Savior, the more he must recoil against every lack
> of conformity to the holiness of God. The deeper his apprehension of
> the majesty of God, the greater the intensity of his love to God, the
> more persistent his yearning for the attainment of the prize of the
> high calling of God in Christ Jesus, the more conscious will he be of
> the gravity of the sin that remains and the more poignant will be his
> detestation of it....Was this not the effect in all the people of God
> as they came into closer proximity to the revelation of God’s
> holiness." -John Murray, Redemption Accomplished and Applied
>
>
>
The first paragraph you quoted alludes to the experience that in the beginning of our Christian walk, we all think about the rules a lot. We think about avoiding this sin, trying to increase this positive trait. As we become more conformed to the image of Christ, these things become more natural. Our minds become more confirmed to the image of Christ through God's continuous work on us, and our own submission to His will that we no longer think about nit-picky rules, but instead, simply live in a way that is more Christ-like. We don't think about it, we don't verbalize it, it becomes who we are.
In the end, we're not thinking about being good, we're too busy focusing on Christ Himself, the source of all goodness.
The last few sentences are indicating that Lewis didn't think he'd reached the same point in his walk as other, who were more closely confirmed to God's image than he was.
Taking this a step further, it is a quite lovely way of saying that Christianity isn't about rules, regulations, or morality, it's about Christ, and our relationship to and with Him. We are "good" (or at least as good as we can be) because of the work He does in us, not because of our obedience to rules, but because of who we are *through* Him. Our morality is based on our love for Him. This is discussed [here](http://www.christinyou.net/pages/Xnotmor.html). | I'd hope that Lewis would give me at least a passing mark if I suggested that it was reasonably well summarised by this verse from a hymn by Helen Lemmel.
>
> Turn your eyes upon Jesus
>
> Look full in his wonderful face
>
> And the things of earth will grow strangely dim.
>
> In the light of his glory and grace.
>
>
>
[Lyrics here](http://library.timelesstruths.org/music/Turn_Your_Eyes_upon_Jesus/)
Hillsong [**doing a reasonable job of imparting the impression of**](https://www.youtube.com/watch?v=czxd5oa-gi0)
" ... They are too busy looking at the source from which it comes. But this is near the stage where the road passes over the rim of our world. No one's eyes can see very far beyond that ..." |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | He seems to be describing the bliss of faith where the knowledge of good and evil does not dominate our awareness. He does it kind of poetically. As we are sinful and not absolutely sure of our forgiveness, due to want of faith, the glory of Christ is hard to look at directly. We do not have such strong faith on this side of heaven not to be frequently taking our spiritual temperature. We are not so confident in the power of Christ's atonement as we aught to be. Therefore we still walk about thinking our sins are carried by ourselves and this makes us feel guilty and uneasy. The kingdom of heaven takes us to another world where sin and its horrors are no longer on our mind. Unfortunately we experience this grace imperfectly in this world. This does not mean that we can't peer into the land of grace by faith. Lewis just admits its heavenly and that others can see it better than he can. | I'd hope that Lewis would give me at least a passing mark if I suggested that it was reasonably well summarised by this verse from a hymn by Helen Lemmel.
>
> Turn your eyes upon Jesus
>
> Look full in his wonderful face
>
> And the things of earth will grow strangely dim.
>
> In the light of his glory and grace.
>
>
>
[Lyrics here](http://library.timelesstruths.org/music/Turn_Your_Eyes_upon_Jesus/)
Hillsong [**doing a reasonable job of imparting the impression of**](https://www.youtube.com/watch?v=czxd5oa-gi0)
" ... They are too busy looking at the source from which it comes. But this is near the stage where the road passes over the rim of our world. No one's eyes can see very far beyond that ..." |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | A man focused on loving others instead of himself will see the many rules shrink to but one. As Romans 13 says:
>
> 8 Let no debt remain outstanding, except the continuing debt to love
> one another, for whoever loves others has fulfilled the law. 9 The
> commandments, “You shall not commit adultery,” “You shall not murder,”
> “You shall not steal,” “You shall not covet,” and whatever other
> command there may be, are summed up in this one command: “Love your
> neighbor as yourself.” 10 Love does no harm to a neighbor. Therefore
> love is the fulfillment of the law.
>
>
>
An analogy I once heard was about flying an aircraft. There are many rules that are followed by the crew and imposed upon the passengers in order to make the flight safe. However, those rules have nothing to do with the purpose of flying. The purpose of flying is to get to your vacation spot, business meeting, wedding, or what-not. As you mature in the faith, the goal of your faith becomes more important, and you get less tripped up by the steps you need to take to get there. | He seems to be describing the bliss of faith where the knowledge of good and evil does not dominate our awareness. He does it kind of poetically. As we are sinful and not absolutely sure of our forgiveness, due to want of faith, the glory of Christ is hard to look at directly. We do not have such strong faith on this side of heaven not to be frequently taking our spiritual temperature. We are not so confident in the power of Christ's atonement as we aught to be. Therefore we still walk about thinking our sins are carried by ourselves and this makes us feel guilty and uneasy. The kingdom of heaven takes us to another world where sin and its horrors are no longer on our mind. Unfortunately we experience this grace imperfectly in this world. This does not mean that we can't peer into the land of grace by faith. Lewis just admits its heavenly and that others can see it better than he can. |
15,172 | I am reading "Mere Christianity" by C.S. Lewis and just finished Chapter 12 in the 3rd section. In this chapter he is discussing the idea that we need to realize we cannot fight sin ourselves, but we must "leave it up to God". We need to trust in following the path of Christ rather than simply putting our own effort forth to stop sinning. That's all great, but I'm having a hard time with the last two paragraphs. I was hoping someone could clarify what he is trying to say.
>
> I think all Christians would agree with me if I said that though Christianity seems at first to be all
> about morality, all about duties and rules and guilt and virtue, yet it leads you on, out of all that, into
> something beyond. One has a glimpse of a country where they do not talk of those things, except
> perhaps as a joke. Every one there is filled full with what we should call goodness as a mirror is filled
> with light But they do not call it goodness. They do not call it anything. They are not thinking of it.
>
>
> They are too busy looking at the source from which it comes. But this is near the stage where the road
> passes over the rim of our world. No one's eyes can see very far beyond that: lots of people's eyes can
> see further than mine.
>
>
> | 2013/03/24 | [
"https://christianity.stackexchange.com/questions/15172",
"https://christianity.stackexchange.com",
"https://christianity.stackexchange.com/users/4220/"
] | A man focused on loving others instead of himself will see the many rules shrink to but one. As Romans 13 says:
>
> 8 Let no debt remain outstanding, except the continuing debt to love
> one another, for whoever loves others has fulfilled the law. 9 The
> commandments, “You shall not commit adultery,” “You shall not murder,”
> “You shall not steal,” “You shall not covet,” and whatever other
> command there may be, are summed up in this one command: “Love your
> neighbor as yourself.” 10 Love does no harm to a neighbor. Therefore
> love is the fulfillment of the law.
>
>
>
An analogy I once heard was about flying an aircraft. There are many rules that are followed by the crew and imposed upon the passengers in order to make the flight safe. However, those rules have nothing to do with the purpose of flying. The purpose of flying is to get to your vacation spot, business meeting, wedding, or what-not. As you mature in the faith, the goal of your faith becomes more important, and you get less tripped up by the steps you need to take to get there. | I'd hope that Lewis would give me at least a passing mark if I suggested that it was reasonably well summarised by this verse from a hymn by Helen Lemmel.
>
> Turn your eyes upon Jesus
>
> Look full in his wonderful face
>
> And the things of earth will grow strangely dim.
>
> In the light of his glory and grace.
>
>
>
[Lyrics here](http://library.timelesstruths.org/music/Turn_Your_Eyes_upon_Jesus/)
Hillsong [**doing a reasonable job of imparting the impression of**](https://www.youtube.com/watch?v=czxd5oa-gi0)
" ... They are too busy looking at the source from which it comes. But this is near the stage where the road passes over the rim of our world. No one's eyes can see very far beyond that ..." |
251,826 | **Two very narrow slits are spaced apart and are
placed 35.0 cm from a screen. What is the distance between the
first and second dark lines of the interference pattern when the slits
are illuminated with coherent light with λ= 550nm**
I'm not asking for an answer for this because I understand the method. I am confused by the theory behind it. When I consulted the solutions manual for this question, they say the first dark line occurs at m = 0 (where m is the order of the image), whereas I thought it occurred at m = 1. Why is this so? | 2016/04/24 | [
"https://physics.stackexchange.com/questions/251826",
"https://physics.stackexchange.com",
"https://physics.stackexchange.com/users/114939/"
] | There is a simple answer: Symmetry.
Suppose the material is isotropic, and consider the initial condition of the p-polarized case, with a p-polarized light wave about to hit the surface. In this case, reflecting in the plane that contains the incident and scattered wave vectors leaves both the (vector) electric field and (pseudovector) magnetic field unchanged. You might think that reflecting in this plane would reverse the direction of the magnetic field, but because the magnetic field is a pseudovector with its direction set arbitrarily by the right-hand rule, there's an extra minus sign involved in a mirror-reflection transformation. The result is a physically equivalent situation that still satisfies Maxwell's equations, with the correct direction of motion in time and the right-hand rule fixed properly.
So the initial conditions have mirror symmetry in this plane, and the time evolution equations (Maxwell's equations) have mirror symmetry in this plane, so the outcome has to have the same symmetry. So the reflected wave has to be p-polarized.
Here's another way of thinking about it: If you sent a p-polarized wave in and got an s-polarized component, how does the physics decide whether the electric field should initially go left or right? More precisely: Choose a point in time and space where the incident wave hits the surface with the z component of the electric field maximized. Either the electric field for the s-polarized component of the scattered wave is nonzero at this point, and thus must be in either the +y or the -y direction, or the field is zero and its time derivative is nonzero, so the time derivative is in either the +y or the -y direction. But there's nothing in the physics to decide which of those two cases (+y or -y) will come out. And if we deduce that it must be one of them, and we redo the analysis of the mirror-image of the same experiment (which, we've already seen, is identical to the original experiment), then we get the opposite answer. So either Maxwell's equations allow two distinct solutions (which we know from various uniqueness relations shouldn't be possible), or the s-polarized component has a magnitude of exactly zero.
Similarly, suppose we start with s polarization and again we figure out what the field would look like in a mirror. The electric field now reverses sign under the mirror reflection, as does the magnetic field (again, because of the extra minus sign arising from the magnetic field's pseudovector nature), and we have exactly the same situation but with an extra minus sign. And a similar argument tells us that the s-polarized incident wave can't produce a p-polarized reflected wave.
In summary, and using slightly more technical language:
Reflecting in the x-z plane has no effect on the p-polarized light. The initial conditions therefore have what's called "even parity" under this symmetry operation.
Reflecting in the x-z plane has no effect on the s-polarized light except for multiplication by a minus sign. The initial conditions in this case have "odd parity."
The equations of motion, Maxwell's equations, are symmetric under mirror reflections (again, so long as we understand about that extra minus sign for the magnetic field). So, by Noether's theorem, parity is conserved. Even-parity input states can only give rise to even-parity output states, and vice versa.
So you now know on general principles that the result has to hold. But what if you wanted to verify it in detail? Well, there's an easy enough way to do that as well. You can add to the analysis an additional reflected wave of the other polarization. So for example you can set up a problem where you have an incident p-polarized wave, a reflected p-polarized wave, a refracted p-polarized wave, and two extra waves not in the original problem: a reflected s-polarized wave and a refracted s-polarized wave. Then you set about solving the problem just as before. If you crank through the algebra, you'll find that the amplitudes of the s-polarized components have to be zero. There just will be no way to have them simultaneously match up the boundary conditions at all points in space and time without adding an extra *incident* s-polarized wave, which is cheating because you're changing the initial conditions. In fact, you might want to go ahead and go through this exercise and see exactly why it doesn't work. At one point, you'll find that if you have the s-wave match in amplitude at all points in space for a given point in time, then the time derivatives all have the wrong signs to match in nearby points in time. And vice versa: If you match the time derivatives, the amplitudes will have the wrong signs. And there's just no way to get the phase factors to match up; there will always be a minus sign that doesn't go away. This is how a parity violation shows up in the algebra. Once you've gone through that exercise, you might better understand why the symmetry has to work that way in general.
Finally, we come to birefringence. Why can birefringence mix s and p polarizations? Simple: Because a birefringent material breaks the mirror-plane symmetry in general. Sure, there will be ways to cut the surface and define the incident direction where the physical situation will still have either pure-even or pure-odd parity, but for a random cut and a random incident direction, it generally won't. The physical situation will have what's called "mixed parity," and this is what allows you to mix the s and p components without violating Noether's theorem.
This is an extremely important principle in physics. When you get used to symmetry laws, you can skip huge parts of complicated derivations, just crossing out terms that are "obviously" zero because they have the wrong symmetry. You know how in freshman physics you can often skip a lot of details of a calculation because you know that, say, momentum has to be conserved? This is exactly the same thing, but just more general. Especially when you get into quantum mechanics, this is a really big deal. | Here's a simple explanation based on the dipolar nature of the medium:
For *most* of the materials, we can assume that the source of the reflected and refracted waves are the induced tiny dipoles in the dielectric medium. In an *isotropic* medium, polarization vector is proportional to the (total) electric field vector with a constant (as opposed to a tensor for anisotropic media). Therefore they are always in the same direction.
Also, the far-field radiation of a dipole is polarized in the same direction as the dipole moment vector and hence the incident (exciting) wave.
Therefore, if the material is isotropic, the polarizations of reflected and refracted waves are the same as that of the incident wave. In general, this is not true for birefringent crystals, for which the direction of the induced polarization may not be the same as the incident electric field. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | Just do it and schedule it into your normal process. Estimate refactoring time into starting a new change or into finishing a change (ideal).
I always refactor while I'm initially exploring new code (extracting methods, etc). | In one of Robert Glass's recent books (I'll have to look up the reference) he mentioned a study on the cost of well maintained code. What they found is that well maintained code was edited more often than poorly maintained code. That sounds counter intuitive but when they dug deeper the discovered the reason:
Well maintained code has more features added to it in the same time frame than poorly maintained code.
Does your Boss like features? Sure, they all do. If more you improve the maintainability of the code, the more features you will be able to deliver with that limited budget. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | Tell him 80% of the costs associated with a software project comes in the maintenance phase of the lifecycle. Any refactoring done now to alleviate future problems, and have some examples, will net substantial cost benefits later on when the need arises to maintaining that code.
This is assuming you are refactoring for a reason and not for programmer vanity. | In my opinion, the simplest case to make for refactoring is fixing overly complex code. Measure the McCabe cyclomatic complexity of the source code in question (Source Monitor is an excellent tool for such a problem). Source code with high cyclomatic complexity has a strong correlation defects and bad fixes. What this means in simple terms is that complex code is harder to fix and more likely to have bad fixes. What this means to a manager is that the quality of the product will likely be worse, and the bugs harder to fix, and the schedule for the project ultimately worse. However, in refactoring out the complexity, you are improving the transparency of the code, reducing the likelihood of obscure / difficult bugs, and making it easier to maintain (e.g. a maintenance programmer can have a larger maintenance scope because of this).
Additionally, you can make the case (if it isn't a dead product in maintenance cycle) that decreasing complexity makes the application easier to extend when new requirements are added to the project. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | It's important to include refactoring time in your original estimates. Going to your boss after you've delivered the product and then telling him that you're not actually done is lying about being done. You didn't actually make the deliverable deadline. It's like a surgeon doing surgery and then not making sure he put everything back the way it was supposed to be.
It is important to include all the parts of development (e.g. refactoring, usability research, testing, QA, revisions) in your original schedules. Ultimately this isn't so much a management problem as a programmer problem.
If, however, you've inherited a mess then you will have to explain to the boss that the last set of programmers in a rush to get the project out the door cut corners and that it's been limping along. You can band-aid the problem for awhile (as they likely did), but each band-aid just delays the problem and ultimately makes the problem that much more expensive to fix.
Be honest with your boss and understand that a project isn't done until it's done. | Speak in a language he can understand.
Refactoring is paying design debt.
Ask your boss why he pays the company credit card bill every month vs not paying it until there is a collections notice. Tell him refactoring is like making your monthly payment. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | I like the answer given in "Refactoring" by Martin Fowler. Tell your boss that you are going to develop software the fastest way that you know how. It happens that in most cases the fastest way to develop software is to refactor as you go.
The other thing to tell your boss is you are reducing the cost to make future improvements. | In my opinion, the simplest case to make for refactoring is fixing overly complex code. Measure the McCabe cyclomatic complexity of the source code in question (Source Monitor is an excellent tool for such a problem). Source code with high cyclomatic complexity has a strong correlation defects and bad fixes. What this means in simple terms is that complex code is harder to fix and more likely to have bad fixes. What this means to a manager is that the quality of the product will likely be worse, and the bugs harder to fix, and the schedule for the project ultimately worse. However, in refactoring out the complexity, you are improving the transparency of the code, reducing the likelihood of obscure / difficult bugs, and making it easier to maintain (e.g. a maintenance programmer can have a larger maintenance scope because of this).
Additionally, you can make the case (if it isn't a dead product in maintenance cycle) that decreasing complexity makes the application easier to extend when new requirements are added to the project. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | I like the answer given in "Refactoring" by Martin Fowler. Tell your boss that you are going to develop software the fastest way that you know how. It happens that in most cases the fastest way to develop software is to refactor as you go.
The other thing to tell your boss is you are reducing the cost to make future improvements. | The boss has to trust the dev to make correct technical decisions (including when to refactor).
Establish that trust or replace the boss or replace the dev. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | Tell him 80% of the costs associated with a software project comes in the maintenance phase of the lifecycle. Any refactoring done now to alleviate future problems, and have some examples, will net substantial cost benefits later on when the need arises to maintaining that code.
This is assuming you are refactoring for a reason and not for programmer vanity. | Sometimes, it's just time to get a new job. There are certian poeple who just want you to "get it done". If you are ever in one of those situations, and I've been there, then just leave.
But yeah, all that other stuff about future costs and such is good idea. I just think that most bosses lie to themselves because they want what they want when they want it, and they are just not able to see what's going to happen in the future.
So, good luck with your boss. Hpefully he or she is reasonable. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | Speak in a language he can understand.
Refactoring is paying design debt.
Ask your boss why he pays the company credit card bill every month vs not paying it until there is a collections notice. Tell him refactoring is like making your monthly payment. | In one of Robert Glass's recent books (I'll have to look up the reference) he mentioned a study on the cost of well maintained code. What they found is that well maintained code was edited more often than poorly maintained code. That sounds counter intuitive but when they dug deeper the discovered the reason:
Well maintained code has more features added to it in the same time frame than poorly maintained code.
Does your Boss like features? Sure, they all do. If more you improve the maintainability of the code, the more features you will be able to deliver with that limited budget. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | It's important to include refactoring time in your original estimates. Going to your boss after you've delivered the product and then telling him that you're not actually done is lying about being done. You didn't actually make the deliverable deadline. It's like a surgeon doing surgery and then not making sure he put everything back the way it was supposed to be.
It is important to include all the parts of development (e.g. refactoring, usability research, testing, QA, revisions) in your original schedules. Ultimately this isn't so much a management problem as a programmer problem.
If, however, you've inherited a mess then you will have to explain to the boss that the last set of programmers in a rush to get the project out the door cut corners and that it's been limping along. You can band-aid the problem for awhile (as they likely did), but each band-aid just delays the problem and ultimately makes the problem that much more expensive to fix.
Be honest with your boss and understand that a project isn't done until it's done. | If your boss doesn't understand the need to refactor or clean up code, then you have to wonder if he has enough engineering knowledge to be an engineering manager. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | I like the answer given in "Refactoring" by Martin Fowler. Tell your boss that you are going to develop software the fastest way that you know how. It happens that in most cases the fastest way to develop software is to refactor as you go.
The other thing to tell your boss is you are reducing the cost to make future improvements. | What I just did recently is to explain to my business counterpart that the re-factory process helps to develop new features faster and decrease the probability of new bugs because the code has a better order and structure, and is even posible to make some speeds improvements because you can inspect the code easier than before.
When the business guys get that, if they are smart, they will encourage you to do a constant re-factory process.
You can explain that with a building metaphor. If you don't do refactory you will end with a crappy building with a bad core so you will have problems with the pipes, windows, doors. |
77,193 | You've just written a pile of code to deliver some important feature under pressure. You've cut a few corners, you've mashed some code into some over-bloated classes with names like SerialIndirectionShutoffManager..
You tell your boss you're going to need a week to clean this stuff up.
"Clean what up?"
"My code - its a pigsty!"
"You mean there's some more bug fixing?"
"Not really, its more like.."
"You're gonna make it run faster?"
"Perhaps, buts thats not.."
"Then you should have written it properly when you had the chance. Now I'm glad you're here, yeah, I'm gonna have to go ahead and ask you to come in this weekend.. "
I've read Matin Fowler's book, but I'm not sure I agree with his advice on this matter:
* Encourage regular code reviews, so refactoring work is encouraged as a natural part of the development process.
* Just don't tell, you're the developer and its part of your duty.
Both these methods squirm out of the need to communicate with your manager.
What do you tell your boss? | 2008/09/16 | [
"https://Stackoverflow.com/questions/77193",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/13899/"
] | Speak in a language he can understand.
Refactoring is paying design debt.
Ask your boss why he pays the company credit card bill every month vs not paying it until there is a collections notice. Tell him refactoring is like making your monthly payment. | I think you should just start working on it without telling your boss. This is truly how I've done my best work. I just don't tell my boss what I'm doing and slowly replace bad/legacy code when I have time.
It has acutally saved my ass on more than one occasion. |
154,019 | I wrote a paper with 3 other students regarding my final year project in mechanical engineering. It was recently selected for a conference in NIT Delhi. Minimum one author is required to present and the price is pretty steep for the participation certificate.Should all of us attend the conference or just one of us? Does the certificate hold any value? | 2020/08/16 | [
"https://academia.stackexchange.com/questions/154019",
"https://academia.stackexchange.com",
"https://academia.stackexchange.com/users/128415/"
] | Perhaps things are different in India than some other places, but I'd suggest that at least one of you go, as required. The others should make a decision whether the conference, itself, independent of the presentation, has enough value to justify the cost in money and time spent. If any of you intend an academic career, the opportunity to meet others has positive value in building future circles of collaboration.
Note that there may be some discounts for student presenters.
Ii think that, in general, a "certificate of participation" has little value other than as a remembrance.
Of course, if you can draw on a grant for this, the computation changes quite a lot, and then the main cost is the time and effort for the individual. That may not be trivial, of course. Talk too your professor(s).
And, congratulations. | You should pay as little as possible to a conference. If there is only one presentation, there should only be one paying presenter.
For online conferences, you may be able to submit your presentation as a recording. The people who appear in the recorded presentation need not be the the paying presenter, unless the conference says otherwise; all the authors could be in the video. Do follow pandemic quarantine rules. |
92,357 | I am dealing with woodworms at home and I am looking for an effective method to contain their spreading and eliminate them from my furniture.
I would just like that they chose another place to build up their home, that should not be my flat!!!
The woodworms are in my furniture since 5 years more or less. I have at least 5 wooden pieces of furniture occupied by woodworms. They are mostly chairs, a showcase and a chest. I figured out that they were woodworms because of the sawdust and the little holes left in the wood.
What happens is that these tiny animals move from a piece to another and every year a different piece of forniture is contaminated.
I did not call a pest control and I had ever dealt the situation on my own. What I did since now it has been to inject a solvent with a syringe inside the holes in order to kill the eggs that they supposedly laid down inside the hole.
However now I am a little bit worried because in this season (spring) they are growing up a lot and spreading in my house and because they started getting inside 3 uncontaminated wooden doors I care a lot about.
Now my request is the following: could someone suggest me some effective methods to prevent their spreading?
I know it may sound strange, but does someone know the habits of these little animals? Or does someone knows a useful book or guide to face against them?
I am able to contain the emergency injecting the solvent in the holes, but I definitely cannot figure out how and where they lay down the eggs. This could be very useful because I would be able to prevent them dig their hole.
Indeed I understood that the big hole we can see in the wood is the exit hole, while the entrance hole is a tiny one, almost not visible unaided eye.
Thank you to everyone! | 2016/06/11 | [
"https://diy.stackexchange.com/questions/92357",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/55082/"
] | You can use a left over matte finish (I'm guessing this is what you were talking about), but the blocks will soak it up and you may need a few coats for a decent look. I would start with a masonry primer first that will seal and fill the pinholes, then you can topcoat it with whatever you want.
You can paint the floor, but you're going to have give more information: Is it new concrete? Is it stained or sealed? Is it painted right now? Do you plan on parking cars on it?
H&C Shield-Crete and the Acrylic glaze to go over it may be your best bet. | You could also used watered-down PVA glue to seal up the pores in the concrete and prime the surface for paint, as this is a cheap and effective way of doing this, and will reduce the amount of paint you need for good coverage.
Note that regular PVA cannot be used to prime surfaces prone to dampness or getting wet. |
92,357 | I am dealing with woodworms at home and I am looking for an effective method to contain their spreading and eliminate them from my furniture.
I would just like that they chose another place to build up their home, that should not be my flat!!!
The woodworms are in my furniture since 5 years more or less. I have at least 5 wooden pieces of furniture occupied by woodworms. They are mostly chairs, a showcase and a chest. I figured out that they were woodworms because of the sawdust and the little holes left in the wood.
What happens is that these tiny animals move from a piece to another and every year a different piece of forniture is contaminated.
I did not call a pest control and I had ever dealt the situation on my own. What I did since now it has been to inject a solvent with a syringe inside the holes in order to kill the eggs that they supposedly laid down inside the hole.
However now I am a little bit worried because in this season (spring) they are growing up a lot and spreading in my house and because they started getting inside 3 uncontaminated wooden doors I care a lot about.
Now my request is the following: could someone suggest me some effective methods to prevent their spreading?
I know it may sound strange, but does someone know the habits of these little animals? Or does someone knows a useful book or guide to face against them?
I am able to contain the emergency injecting the solvent in the holes, but I definitely cannot figure out how and where they lay down the eggs. This could be very useful because I would be able to prevent them dig their hole.
Indeed I understood that the big hole we can see in the wood is the exit hole, while the entrance hole is a tiny one, almost not visible unaided eye.
Thank you to everyone! | 2016/06/11 | [
"https://diy.stackexchange.com/questions/92357",
"https://diy.stackexchange.com",
"https://diy.stackexchange.com/users/55082/"
] | You can use a left over matte finish (I'm guessing this is what you were talking about), but the blocks will soak it up and you may need a few coats for a decent look. I would start with a masonry primer first that will seal and fill the pinholes, then you can topcoat it with whatever you want.
You can paint the floor, but you're going to have give more information: Is it new concrete? Is it stained or sealed? Is it painted right now? Do you plan on parking cars on it?
H&C Shield-Crete and the Acrylic glaze to go over it may be your best bet. | Three years ago, we painted our breeze block wall red with Behr exterior paint that was mold/mildew resistant. It is still holding up and looks like it was painted yesterday. Unfortunately, it took 3 coats to get total coverage. I did pressure wash the breeze block before I we painted. Besides that, we didn't do anything else special. |
25,341 | New to DSLR photography and would like some advice. What would be a good all round lens for the Nikon D3100? I have got the 18-55 one from the kit, any recommendations?
Also are there any other items you feel are a needed bit of kit?
UPDATE (From comments below):
I would like to have more zoom, I was looking at these 2 lenses Nikon 55-200mm f/4.-5.6 AFS DX VR and the Nikon AF-S 55-300mm f4.5-5.6 G ED VR Lens - DX Format. I take pictures of scenery and my kids obviously - got some great pics of them at the beach at the weekend. But could not zoom in as they were playing in the sea :) Maybe i need to buy a good book which can help with all the setting etc, as with most people i never read the manual | 2012/07/16 | [
"https://photo.stackexchange.com/questions/25341",
"https://photo.stackexchange.com",
"https://photo.stackexchange.com/users/10650/"
] | There is no such thing as an all-round lens that would suit everybody.
Typically though most DSLRs come with a kit-lens in the range 18-55, and that's a good starting point. From there you can make your own choice - i.e. Do you want a similar range but wider aperture, or do you want to look at primes or zooms? | I consistently recommend a lens when asked this sort of question which is different from the usual. I use one as my "walk around" lens and am extremely happy with it. The lens covers 18-270mm which is too wide to be able to do as well as lower range zooms of equal price BUT it's performance is superb given its flexibility and general capabilities.
It's the (take deep breath) Tamron AF 18-270mm f/3.5-6.3 Di II VC LD Aspherical (IF) MACRO (or some variant thereof). (Mine is the 18-250mm earlier Sony badged, Tamron-manufactured equivalent)
Approximate competitors include.
Canon EF-S 18-200mm F3.5-5.6 IS,
Nikon 18-200mm f/3.5-5.6G IF-ED AF-S VR DX, and
Sigma 18-200mm F3.5-6.3 DC OS,
This lens represents a substantial jump in optical performance compared to earlier wide range zooms - their desultory performance making people think that all "superzooms" must be equally bad. Here are [56 user reviews on the Sony 18-250mm](http://www.dyxum.com/reviews/lenses/reviews.asp?IDLens=415) which is the Tamron lens with Sony badges plus faster AF gear ratio plus more rounded aperture petals. 56 users on average rate it (out of 5)
4.39 Sharpness
4.48 Color
4.32 Build
4.32 Flare
3.93 Distortion
4.29 Overall (4.38 excluding distortion)
Distortion is partially a consequence of the vast zoom range, relates mainly to overall image shape (see reviews) and is largely correctable by various software modules (and is in most cases 'acceptable enough' as is).
The f/3.5-6.3 is "slow" compared to eg a constant f/2.8 that you'd love to own BUT not appreciably different from the f/4-f/5.6 lenses that you mentioned.
DPReview are, in my opinion, amongst the most demanding of review sites. Some may disagree but many agree with this - in my experience, if a product has a weakness, falls short in any measurable way or just "isn't right" for whatever reason, they'll tell you. I've heard claims in recent years of partisan behaviour on their part but so far I'm happy with their reviews (fwiw).
Their review of the Tamron 18-270 is here ](<http://www.dpreview.com/lensreviews/tamron_18-270_3p5-6p3_vc_n15>)
They by no means give it a glowing report in every aspect. They make it clear that it makes compromises due to the ultra wide zoom range, and they note that it's AF speed is poor if you concentrate on moving subjects. But, given how 'hard' they are on anything they test, this represents a very good result.
They conclude:
* These minor niggles aside, we were overall quite impressed by the Tamron 18-270mm. Where it's good, it's actually very good indeed, and even where it's weak it's not too far behind the competition. And that remarkable zoom range is a draw in itself; this is a lens which will have you shooting the same subject from the same position at both 18mm and 270mm, just to see how it looks. If you often find yourself shooting things which move then this may not be the ideal choice, but if you're willing to put up with its somewhat sluggish focusing it's a remarkably rewarding lens for the money.
I own the older 18-250mm Sony version of this lens.
While I agree that faster or even much faster AF would be nice, it's far better than many older lenses that I've used and is very usable in action situations as long as you are prepared to work harder than you'd do with a crisper focusing AF lens.
For a "universal lens" you'll be unlikely to ever regret buying it. When you can afford to buy a constant f/2.8 do so. Until then you'll enjoy this. 18-270mm on a DX body = 27-405mm! equivalent. My 18-250mm is f/4.5 or less up to about 70mm. That's 1.3 stops worse than a constant f/2.8
[Useful re3view and comparisons here](http://www.the-digital-picture.com/Reviews/Tamron-18-270mm-f-3.5-6.3-Di-II-VC-Lens-Review.aspx)
[Brief but useful user discussion](http://photo.net/nikon-camera-forum/00aYb2) |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I can't help with the RFID portion, but to lock the door you can purchase surplus [car lock actuators](http://www.allelectronics.com/make-a-store/item/DLA-1/DOOR-LOCK-ACTUATOR//1.html "door lock actuators"), they are simple solenoids that works off of 12Vdc. I have not used them yet but I plan on using them for a locking chest. | To read EM4100 tags (the cheap, 125 kHz kind) you need to get a good coupling between the tags coil and the reader coil.
The bigger the tag coil, the better and more reliable the signal will be.
First of all you'd need to wrap the reader coil all the way around the portal to ensure that the animal is going to be within the magnetic field.
Second of all you need to make sure that the tag coil is parallel to the reader coil, I think the easiest way to do that is to build collar where the coil is built into the collar and connected via a connector where the chip is located.
The entire trick is to build the RFID collar to be both durable and removable.
The circuit for the reader is very simple and can be built for under $2 provided you have an AVR such as the one found in an Arduino to connect it to, take a look at the bottom of this schematic: <http://www.hackaarhus.dk/forum/download/file.php?id=33> |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I can't help with the RFID portion, but to lock the door you can purchase surplus [car lock actuators](http://www.allelectronics.com/make-a-store/item/DLA-1/DOOR-LOCK-ACTUATOR//1.html "door lock actuators"), they are simple solenoids that works off of 12Vdc. I have not used them yet but I plan on using them for a locking chest. | Have also done some work with [RFID and Arduino](http://tronixstuff.wordpress.com/2010/08/18/moving-forward-with-arduino-%e2%80%93-chapter-15-%e2%80%93%c2%a0rfid-introduction/) if anyone is interested. |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I am be very interested to see how this works out.
I am currently making an RFID controlled lock for a door and I know from my work on that,that RFID have range limitations(depending on what type of reader and chip you use) so the position of both reader and chip may be very important especially because you're planning on using it on an unpredictable living thing. That might be a big challenge and may require more than one RFID reader.
As far as a locking mechanism you can make one really cheap by taking apart an old cd drive and using the slots drive system. | ZigBee could be a decent alternative for RFID. I've never used it, but it's designed for situations like yours. |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I am be very interested to see how this works out.
I am currently making an RFID controlled lock for a door and I know from my work on that,that RFID have range limitations(depending on what type of reader and chip you use) so the position of both reader and chip may be very important especially because you're planning on using it on an unpredictable living thing. That might be a big challenge and may require more than one RFID reader.
As far as a locking mechanism you can make one really cheap by taking apart an old cd drive and using the slots drive system. | I can't help with the RFID portion, but to lock the door you can purchase surplus [car lock actuators](http://www.allelectronics.com/make-a-store/item/DLA-1/DOOR-LOCK-ACTUATOR//1.html "door lock actuators"), they are simple solenoids that works off of 12Vdc. I have not used them yet but I plan on using them for a locking chest. |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I can't really help you with the issue of identifying you pets but for the latching mechanism you should look into linear actuators. The friction in the ball/screw drive of the actuator will be enough to hold the lock in place without applying power to the motor. A simple DC actuator (with built in limit switches) and a throw of 1cm-2cm should be enough to operate a set of bolts. Linear actuators are typically slower than servos and solenoids but have more power and will stall the mechanism without using power. | To read EM4100 tags (the cheap, 125 kHz kind) you need to get a good coupling between the tags coil and the reader coil.
The bigger the tag coil, the better and more reliable the signal will be.
First of all you'd need to wrap the reader coil all the way around the portal to ensure that the animal is going to be within the magnetic field.
Second of all you need to make sure that the tag coil is parallel to the reader coil, I think the easiest way to do that is to build collar where the coil is built into the collar and connected via a connector where the chip is located.
The entire trick is to build the RFID collar to be both durable and removable.
The circuit for the reader is very simple and can be built for under $2 provided you have an AVR such as the one found in an Arduino to connect it to, take a look at the bottom of this schematic: <http://www.hackaarhus.dk/forum/download/file.php?id=33> |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | At Uni I did a talk on RFID chips as part of one module for my course. Based on the research I did then, and never actually having used them in real life, you probably will need to research/play with different chips to find ones that work. some chips can be blocked by a bottle of water, so whether a dog or cat's neck will do the same thing depends.
Possible problems that spring to mind:
Does the position of the chip on the collar (top, bottom, side etc) relative to the sensor(s?) have an effect on detection?
Will you need more than 1 sensor?
What happens if your dog is in proximity to the flap, when the older cat wants to get out? Are you thinking that the chips will only be on cats which are not allowed out, thereby locking the flap whilst in proximity?
If there are commercially available versions of this technology, see if you can find out what they use, including which brand/type of chip.
A book which was particularly useful whilst researching RFID as a topic (it seemed to have lots of case studies of implementations in it too) was RFID for Dummies which is [here](http://www.amazon.co.uk/RFID-Dummies-Patrick-J-Sweeney/dp/076457910X/ref=sr_1_2?ie=UTF8&s=books&qid=1257111710&sr=8-2) on Amazon in the UK.
(That pretty much exhausts my knowledge of RFID, let us know how you get on, somehow.) | To read EM4100 tags (the cheap, 125 kHz kind) you need to get a good coupling between the tags coil and the reader coil.
The bigger the tag coil, the better and more reliable the signal will be.
First of all you'd need to wrap the reader coil all the way around the portal to ensure that the animal is going to be within the magnetic field.
Second of all you need to make sure that the tag coil is parallel to the reader coil, I think the easiest way to do that is to build collar where the coil is built into the collar and connected via a connector where the chip is located.
The entire trick is to build the RFID collar to be both durable and removable.
The circuit for the reader is very simple and can be built for under $2 provided you have an AVR such as the one found in an Arduino to connect it to, take a look at the bottom of this schematic: <http://www.hackaarhus.dk/forum/download/file.php?id=33> |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I am be very interested to see how this works out.
I am currently making an RFID controlled lock for a door and I know from my work on that,that RFID have range limitations(depending on what type of reader and chip you use) so the position of both reader and chip may be very important especially because you're planning on using it on an unpredictable living thing. That might be a big challenge and may require more than one RFID reader.
As far as a locking mechanism you can make one really cheap by taking apart an old cd drive and using the slots drive system. | At Uni I did a talk on RFID chips as part of one module for my course. Based on the research I did then, and never actually having used them in real life, you probably will need to research/play with different chips to find ones that work. some chips can be blocked by a bottle of water, so whether a dog or cat's neck will do the same thing depends.
Possible problems that spring to mind:
Does the position of the chip on the collar (top, bottom, side etc) relative to the sensor(s?) have an effect on detection?
Will you need more than 1 sensor?
What happens if your dog is in proximity to the flap, when the older cat wants to get out? Are you thinking that the chips will only be on cats which are not allowed out, thereby locking the flap whilst in proximity?
If there are commercially available versions of this technology, see if you can find out what they use, including which brand/type of chip.
A book which was particularly useful whilst researching RFID as a topic (it seemed to have lots of case studies of implementations in it too) was RFID for Dummies which is [here](http://www.amazon.co.uk/RFID-Dummies-Patrick-J-Sweeney/dp/076457910X/ref=sr_1_2?ie=UTF8&s=books&qid=1257111710&sr=8-2) on Amazon in the UK.
(That pretty much exhausts my knowledge of RFID, let us know how you get on, somehow.) |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I am be very interested to see how this works out.
I am currently making an RFID controlled lock for a door and I know from my work on that,that RFID have range limitations(depending on what type of reader and chip you use) so the position of both reader and chip may be very important especially because you're planning on using it on an unpredictable living thing. That might be a big challenge and may require more than one RFID reader.
As far as a locking mechanism you can make one really cheap by taking apart an old cd drive and using the slots drive system. | Have also done some work with [RFID and Arduino](http://tronixstuff.wordpress.com/2010/08/18/moving-forward-with-arduino-%e2%80%93-chapter-15-%e2%80%93%c2%a0rfid-introduction/) if anyone is interested. |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | I'm working on something like this myself. I have an ID-12 in hand that does not seem to read my cat's tag. I have a couple of other RFID tags on hand that it will not read, and one that it can read from 6" away (no antenna on everything).
I'm not certain of the kHz of the tag in my cat, or any of my others except for the "control" card I bought with the reader for testing.
The ID-12 is the easiest thing in the world to use in ASCII mode, and this is all I've tried. I think I might have to find a 134kHz model and or a proper antenna to get any farther.
Feel free to contact me. turbohoje@h0tmail | To read EM4100 tags (the cheap, 125 kHz kind) you need to get a good coupling between the tags coil and the reader coil.
The bigger the tag coil, the better and more reliable the signal will be.
First of all you'd need to wrap the reader coil all the way around the portal to ensure that the animal is going to be within the magnetic field.
Second of all you need to make sure that the tag coil is parallel to the reader coil, I think the easiest way to do that is to build collar where the coil is built into the collar and connected via a connector where the chip is located.
The entire trick is to build the RFID collar to be both durable and removable.
The circuit for the reader is very simple and can be built for under $2 provided you have an AVR such as the one found in an Arduino to connect it to, take a look at the bottom of this schematic: <http://www.hackaarhus.dk/forum/download/file.php?id=33> |
105 | Inspired by projects such as the [tweeting cat door](http://www.tweetingcatdoor.com/) and [CATaLOG](http://www.nermal.org/projects/catalog/) [sic] I’m wanting to add some form of automated access control to our pet door to control who can go in and out, when.
(Full Disclosure: This is a [reprint from my blog](http://www.michevan.id.au/content/petting-problem) where I first wrote up the problem, but all feedback is welcome!)
The Players
-----------
We currently have three cats, one dog and one pet door.
### The Mischievous Mutt
[Toby http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/toby-200x150.jpg)
Toby, our two year old Labrador needs access to the backyard anytime, day or night for access to his food, water and [other amenities](http://www.michevan.id.au/sites/www.michevan.id.au/files/u3/dog-poo-sign-cut-766725.jpg).
### The Clutter Kittens
[Bazyl http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/bazyl-200x150.jpg) [Kismet http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/kismet-200x150.jpg)
Bazyl and Kismet, are free to go out during the day (sometimes even encouraged) however in an ideal world the pet door would only allow them to come in, but not out again after dark.
### The Wanderer
[Murray http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/murray-200x150.jpg)
UPDATE 2010/01/17: Unfortunately, Murray is [no longer with us](http://www.michevan.id.au/content/memory-murray). Old age finally caught up with him.
Murray, the venerable 17 year old veteran of the family [who has a habit of going walkabout](http://www.michevan.id.au/content/do-you-have-cat-named-murray). At this stage in his life, it would be best if he stayed indoors.
The Portcullis
--------------
[Pet Door Outside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_outside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_outside-200x150.jpg)
Our pet door, that allows the rabble to go out on the deck and into the backyard. The door is fixed in a wooden panel in the frame of what was originally a window.
Requirements Summary
--------------------
So basically we need something that is able to stop the door swinging outwards during the evening, except when Toby is in proximity, and any time Murray is in proximity. We don't need to worry about foreign cats coming into the house (you've met Toby, yes?) and if we really want to lock the dog out we put the barricade in place as shown below. (We soon learnt that the little plastic lock on the door is not gonna stop him if he really wants in!)
[Pet Door Inside View http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor\_inside-200x150.jpg](http://www.michevan.id.au/sites/www.michevan.id.au/files/resize/u3/petdoor_inside-200x150.jpg)
I'm planning on using an [Arduino](http://www.arduino.cc/) board as the control unit, and think I need twoone RFID tags – one for Toby and one for Murray – at the minimum to handle the rules I've outlined above.
So the preliminary parts list is:
* One [Arduino](http://www.arduino.cc/) controller board.
* One light sensor for sensing daylight hours.
* One RFID scanner.
* Two RFID tags that can be attached to the animals' collar.
* One solenoid or something else that can be used to stop the flap opening to the outside.
* A red/green LED to indicate if the door is currently locked or not.
* A three state switch to enable us to set the door to always open, always locked, or on automatic as required, although we expect it to be on automatic most of the time.
The concerns I have are finding the right RFID scanner and tags that'll work in this environment. I've no experience with RFID but hear a bit about range issues. One tag will be on the collar of a big Labrador, the other on a medium sized cat, so there is a reasonable height difference. The proximity sensing cannot be flaky for this to work, especially for Toby who will get confused if the door only works some of the time and just not bother.
I have been considering an ID-12 or ID-2 scanner with a custom antenna, but people I've talked to think the range will be too small. The size difference between a domestic cat and a Labrador is fairly significant in this case.
Another option might be bluetooth. This would also have the advantage that it could act as a true proximity sensor, detecting when the animal comes into range, remains in range, and goes out of range, whereas RFID is generally triggered once each time the tag comes into range after not being in range. The disadvantage is batteries.
Any other ideas for proximity sensors?
The other thing is the mechanism to block the door. Ideally something that can shoot out out a little bolt to block the path of the door, or retract it to leave the door clear to open. Preferably not something that is spring loaded that needs an active voltage on it to either hold it open or hold it closed. Should only need to apply voltage to change state, not maintain state.
If a bolt is not available, I've seen a stepper motor with a bit of metal on the spindle used to do the same thing. To lock it simply rotates the bit of metal into place, to unlock is rotates it out the way.
So, any and all feedback on the above would be welcome.
UPDATE 2010/01/17: Have finally ordered most of the parts I need for this, as well as the hermit crab tank humidity control, which I'll probably build first ('cause it's simpler). I went with an ID-20 RFID scanner to start with, so we'll see how that goes. Unfortunately, my copy of [Practical Arduino](http://www.practicalarduino.com/) which I'll be using as a reference apparently wont arrive until mid-Feb so progress will be slow before then. | 2009/11/01 | [
"https://electronics.stackexchange.com/questions/105",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/117/"
] | At Uni I did a talk on RFID chips as part of one module for my course. Based on the research I did then, and never actually having used them in real life, you probably will need to research/play with different chips to find ones that work. some chips can be blocked by a bottle of water, so whether a dog or cat's neck will do the same thing depends.
Possible problems that spring to mind:
Does the position of the chip on the collar (top, bottom, side etc) relative to the sensor(s?) have an effect on detection?
Will you need more than 1 sensor?
What happens if your dog is in proximity to the flap, when the older cat wants to get out? Are you thinking that the chips will only be on cats which are not allowed out, thereby locking the flap whilst in proximity?
If there are commercially available versions of this technology, see if you can find out what they use, including which brand/type of chip.
A book which was particularly useful whilst researching RFID as a topic (it seemed to have lots of case studies of implementations in it too) was RFID for Dummies which is [here](http://www.amazon.co.uk/RFID-Dummies-Patrick-J-Sweeney/dp/076457910X/ref=sr_1_2?ie=UTF8&s=books&qid=1257111710&sr=8-2) on Amazon in the UK.
(That pretty much exhausts my knowledge of RFID, let us know how you get on, somehow.) | Have also done some work with [RFID and Arduino](http://tronixstuff.wordpress.com/2010/08/18/moving-forward-with-arduino-%e2%80%93-chapter-15-%e2%80%93%c2%a0rfid-introduction/) if anyone is interested. |
37,864,543 | I want to mirroring from Kafka Source Cluster to Kafka Destination Cluster. Everything is working fine if my both Source and Target Cluster are on the same version (say 0.10.0.0) but its not working when my Source Cluster is on 0.8.2.1 and Target Cluster is on 0.10.0.0.
Does anybody have any idea?
Thanks in advance. | 2016/06/16 | [
"https://Stackoverflow.com/questions/37864543",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6475640/"
] | I'm encountering this same issue. It appears that the mirrormaker is only works if the source and target clusters are the same version. | I can confirm that this won't work. I tested using MirrorMaker from Confluent Platform 3.0. I was trying to replicate from Kafka 0.8.2.2 to Kafka 0.10.1.1. And I could not get them to work. Worked fine on 0.8.2.2 to 0.8.2.2 and fine on 0.10.1.1 to 0.10.1.1.
Also MirrorMaker does not sync any consumers offsets from old to new. This means any messages consumed in the old cluster will need to consumed again in the new cluster. Unless there is some kind of TTL or your application logic can cater for duplicate messages. But even if your app has logic catering for duplicates if you need to re process millions of messages this would be a waste of resources.
We were trying to setup two live clusters with different versions and using MirrorMaker to sync between them and have some of the older versions of consumers consuming off old cluster and newer versions of consumers consuming off new cluster but this now has proven not working. |
37,864,543 | I want to mirroring from Kafka Source Cluster to Kafka Destination Cluster. Everything is working fine if my both Source and Target Cluster are on the same version (say 0.10.0.0) but its not working when my Source Cluster is on 0.8.2.1 and Target Cluster is on 0.10.0.0.
Does anybody have any idea?
Thanks in advance. | 2016/06/16 | [
"https://Stackoverflow.com/questions/37864543",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/6475640/"
] | I'm encountering this same issue. It appears that the mirrormaker is only works if the source and target clusters are the same version. | I got it to work by using the mirror tool of the old version to consume from the old version and to produce messages on the new version. Vice versa does not work. That was between a 0.9 and a 2.7 version though. |
41,695,729 | I used [Glimpse](http://getglimpse.com/) on the old ASP.NET MVC5 stack and liked it very much cause it gives a pretty and detailed representation of nearly all important data for debugging purpose. Sadly, its not compatible with ASP.NET Core (yet). I tried to install the [demo](http://blog.getglimpse.com/2015/11/19/installing-glimpse-v2-beta1/), which assurance to work with ASP.NET Core.
But thats not entirely true cause it works on ASP.NET Core, but depends on the old 4.x framework. So it destroys the cross-platform compability, which is not suiteable for me. The app is designed to run on a Linux based server using docker.
Although, I would like to benefit from those nice features in my Core app, too. Is there any similar alternative to Glimpse that is full compatible to ASP.NET Core? I'm currently using ASP.NET Core 1.1, but could also downgrade to 1.0 if necessary. The most important things for me are request duration and database (SQL) querys, may Redis included if possible. | 2017/01/17 | [
"https://Stackoverflow.com/questions/41695729",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/3276634/"
] | I'm using <https://miniprofiler.com/dotnet/AspDotNetCore>.
It can profile MVC and Entity Framework and it has an UI representation via a Tag helper | You can try <https://stackify.com/prefix/> - although it is a self hosted web app so it is not as "deployable" / works best on local development. It uses profiling so it is less intrusive on the code stack.
Core: <http://support.stackify.com/hc/en-us/articles/209962473-Using-Prefix-with-ASP-NET-Core-Kestrel> |
541,139 | Disclaimer: I'm computer scientist
I have a sinus wave generator (handyscope H3-5) from TiePie but the output power is insufficient for my application. The specification is [here](https://www.tiepie.com/en/usb-oscilloscope/handyscope-hs3). I need at least 60W. I would like to know if it is OK to connect the generator to the input line of an audio amplifier. I need only a signal below 20kHz.
The amplifier is an SMSL SA 98E. I only have a [french data sheet](https://www.audiophonics.fr/fr/amplificateurs-audio/smsl-sa-160-amplificateur-tda7498e-2x-100w-4-ohm-amplificateur-casque-noir-p-9716.html). The data sheet states that the input line is 400mV-2V.
I'm not sure what it means.
Also I know that the generator is 50Ohms. Do I have to care about that ?
I plan to buy an RCA<->BNC cable. These are sold for video connections. I think they are 70Ohms. Would it be OK ? | 2021/01/06 | [
"https://electronics.stackexchange.com/questions/541139",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/270512/"
] | >
> The data sheet states that the input line is 400mV-2V.
>
>
>
That is probably OK; I'd assume you can easily set your output to that amplitude range.
>
> Also I know that the generator is 50Ohms. Do I have to care about that ?
>
>
>
Not in this case: the input impedance of an audio amplifier will be very high, so that the source doesn't have to drive much load (i.e. be able to supply much curent).
And, at 20 kHz you don't have to care about wave impedances etc: your cable is much, much smaller than the wavelength of a 20 kHz electromagnetic wave.
So, this will work.
---
Note that your generator is absolutely overkill.
A sound card would do just as well – these are audio frequencies, after all!
Also, everything but the worst sound cards have astonishingly high fidelity, so that's often an attractive choice. You'll want to be a little careful when using a sound card that it has (or you add) good anti-imaging filtering (i.e. to suppress harmonics that arise from the discrete-time sampling). | *OK to connect the generator to the input line of an audio amplifier?*
Yes, this is done all the time.
The cable impedance is not important at audio frequencies.
Set your function generator output level to about 0.5 V p-p.
What are you connecting to the output of the amplifier? Here is where you need to be more concerned. Audio amplifiers are not tolerant to low impedance, 4-8 ohms is usually the minimum, look at the specs.
If you are driving speakers, beware. A speaker may not tolerate a lot of energy at one frequency. |
541,139 | Disclaimer: I'm computer scientist
I have a sinus wave generator (handyscope H3-5) from TiePie but the output power is insufficient for my application. The specification is [here](https://www.tiepie.com/en/usb-oscilloscope/handyscope-hs3). I need at least 60W. I would like to know if it is OK to connect the generator to the input line of an audio amplifier. I need only a signal below 20kHz.
The amplifier is an SMSL SA 98E. I only have a [french data sheet](https://www.audiophonics.fr/fr/amplificateurs-audio/smsl-sa-160-amplificateur-tda7498e-2x-100w-4-ohm-amplificateur-casque-noir-p-9716.html). The data sheet states that the input line is 400mV-2V.
I'm not sure what it means.
Also I know that the generator is 50Ohms. Do I have to care about that ?
I plan to buy an RCA<->BNC cable. These are sold for video connections. I think they are 70Ohms. Would it be OK ? | 2021/01/06 | [
"https://electronics.stackexchange.com/questions/541139",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/270512/"
] | >
> The data sheet states that the input line is 400mV-2V.
>
>
>
That is probably OK; I'd assume you can easily set your output to that amplitude range.
>
> Also I know that the generator is 50Ohms. Do I have to care about that ?
>
>
>
Not in this case: the input impedance of an audio amplifier will be very high, so that the source doesn't have to drive much load (i.e. be able to supply much curent).
And, at 20 kHz you don't have to care about wave impedances etc: your cable is much, much smaller than the wavelength of a 20 kHz electromagnetic wave.
So, this will work.
---
Note that your generator is absolutely overkill.
A sound card would do just as well – these are audio frequencies, after all!
Also, everything but the worst sound cards have astonishingly high fidelity, so that's often an attractive choice. You'll want to be a little careful when using a sound card that it has (or you add) good anti-imaging filtering (i.e. to suppress harmonics that arise from the discrete-time sampling). | Yes you will be fine - but beware that very LOW frequencies (less than 20Hz or so) may cause problems. Audio amps (good ones) block DC and frequencies below about 10-20Hz, for good reason : that stuff can kill speakers at high levels.
What are you actually driving? what's the load, and what's the application? |
541,139 | Disclaimer: I'm computer scientist
I have a sinus wave generator (handyscope H3-5) from TiePie but the output power is insufficient for my application. The specification is [here](https://www.tiepie.com/en/usb-oscilloscope/handyscope-hs3). I need at least 60W. I would like to know if it is OK to connect the generator to the input line of an audio amplifier. I need only a signal below 20kHz.
The amplifier is an SMSL SA 98E. I only have a [french data sheet](https://www.audiophonics.fr/fr/amplificateurs-audio/smsl-sa-160-amplificateur-tda7498e-2x-100w-4-ohm-amplificateur-casque-noir-p-9716.html). The data sheet states that the input line is 400mV-2V.
I'm not sure what it means.
Also I know that the generator is 50Ohms. Do I have to care about that ?
I plan to buy an RCA<->BNC cable. These are sold for video connections. I think they are 70Ohms. Would it be OK ? | 2021/01/06 | [
"https://electronics.stackexchange.com/questions/541139",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/270512/"
] | >
> The data sheet states that the input line is 400mV-2V.
>
>
>
That is probably OK; I'd assume you can easily set your output to that amplitude range.
>
> Also I know that the generator is 50Ohms. Do I have to care about that ?
>
>
>
Not in this case: the input impedance of an audio amplifier will be very high, so that the source doesn't have to drive much load (i.e. be able to supply much curent).
And, at 20 kHz you don't have to care about wave impedances etc: your cable is much, much smaller than the wavelength of a 20 kHz electromagnetic wave.
So, this will work.
---
Note that your generator is absolutely overkill.
A sound card would do just as well – these are audio frequencies, after all!
Also, everything but the worst sound cards have astonishingly high fidelity, so that's often an attractive choice. You'll want to be a little careful when using a sound card that it has (or you add) good anti-imaging filtering (i.e. to suppress harmonics that arise from the discrete-time sampling). | All the other answers have adequately covered your question. I'm going to add a reminder that audio amplifiers are not precision equipment.
Your amplifier will be able to faithfully reproduce the signal you give it, as long as you keep your signal within the input limits of the amplifier and as long as you don't "crank up the volume" to the point that the output clips (distorts.)
If the output level is in any way critical to your experiment, then you will need to measure the output level. Your output level is related to the input level by the amplification (gain) of your amplifier, and by the setting of the volume control knob.
The volume control isn't calibrated in any way - you can't rely on it for absolutely reproducible results.
Since you don't (can't) say what the experiment is about, no one can even begin to guess how critical the output power is.
If it's critical, measure it.
As a value for repeating your own steps, the output voltage (peak to peak or RMS) would be a good starting point. You'll need either an oscilloscope or an AC voltmeter to measure it. If you use an AC voltmeter, you'll need one that covers the entire audio range. Common hardware store voltmeters cover just the typical household AC line frequencies (50 or 60 Hz.) AC voltmeters that cover up to 20kHz can be expensive.
For whatever paper you write about your results, you may need to include to actual power into the coil, and maybe the waveform as actually fed into the coil. |
197,675 | I have a Dell XPS 9550. This was shipped without a TPM.
I have since installed a Samsung 970 EVO SSD which as I understand is a self-encrypting drive (SED) and, what I am not sure about is, it can be encrypted without a TPM?
So, I have installed the drive, installed Windows 10, set "Encrypted Drive" to "ready to enable". Did a secure erase and reinstalled Windows 10.
Samsung Magician now shows the below ("Encrypted Drive" is "Enabled"):
[](https://i.stack.imgur.com/gIfLg.png)
Bit Locker will not enable on the OS drive without overriding the "your administrator must set the allow bitlocker without a compatible tpm" setting.
Does this mean my drive is encrypted?
Or do I need to override the TPM setting and setup bit locker still and then bit locker with use the hardware encryption on the drive?
Or do I need to set a BIOS system password?
I have searched but with no clear guidance or insight. | 2018/11/14 | [
"https://security.stackexchange.com/questions/197675",
"https://security.stackexchange.com",
"https://security.stackexchange.com/users/73340/"
] | >
> Does this mean my drive is encrypted?
>
>
>
Yes. You have successfully set up BitLocker using the built-in hardware encryption of your drive. The "?"-tooltip of Samsung Magician will clearly state that this is not a separate drive encryption but meant for use with BitLocker. In fact, using this option, BitLocker will simply rely on the drives always-active internal encryption, which is very efficient. You can double-check by invoking "manage-bde -status" from an elevated command prompt or PowerShell.
>
> Or do I need to override the TPM setting and setup bit locker still
> and then bit locker with use the hardware encryption on the drive?
>
>
>
No.
>
> Or do I need to set a BIOS system password?
>
>
>
No. | you need to enable bit locker without tpm. use gpedit.msc. i don't remember the config but you can google it.
after reboot, try to activate bit locker in control panel. if it doesn't give options of full or partial encryption, that's means you successfully get bit locker hardware encryption.
recheck using manage-bde -status command. it should show hardware encryption with unlocked status |
300,986 | Not sure if I used affect/effect correctly, but anyway...
So, here's my question if the title didn't explain it well enough: say you have the following phrase: "in the men's bathroom". The plural of "man" is "men", so when showing possession with a plural word that doesn't end in "s", you use "apostrophe s", right? Well, what if "bathroom" were also plural? So you've got multiple men and multiple bathrooms. Would it be "men's bathrooms" or "mens' bathrooms"? Does the object being possessed being singular or plural make a difference as far as whether or not you use 's or s'? I could have sworn I was taught in school it does make a difference, but now I can't remember. | 2016/01/19 | [
"https://english.stackexchange.com/questions/300986",
"https://english.stackexchange.com",
"https://english.stackexchange.com/users/123262/"
] | It is men's bathrooms, never mens' ([Mens' or Men's?](http://crofsblogs.typepad.com/english/2007/07/mens-or-mens.html).)
There is no difference in the noun-number of the object being possessed (whether it is singular or plural). This link may be helpful: [Rules for Apostrophes explaining possession](http://www.grammarbook.com/punctuation/apostro.asp). | This is two different questions:
**Number 1:**
No. The possessive noun does not effect the possessed.
**Examples:**
Men: singular; Bathroom: plural:
>
> the man's bathrooms
>
>
>
Men: plural; Bathroom: plural:
>
> the mens' bathrooms
>
>
>
Men: singular; Bathroom: singular:
>
> the man's bathroom
>
>
>
Men: plural; Bathroom: singular:
>
> the mens' bathroom
>
>
>
However, the above is wrong, because men is an irregular noun. for most nouns, the above, however, for men, the below is true:
Men: singular; Bathroom: plural:
>
> the man's bathrooms
>
>
>
Men: plural; Bathroom: plural:
>
> the men's bathrooms
>
>
>
Men: singular; Bathroom: singular:
>
> the man's bathroom
>
>
>
Men: plural; Bathroom: singular:
>
> the men's bathroom
>
>
> |
4,847,977 | How do I show a show home page if a user requests login page with a valid session using spring security? | 2011/01/31 | [
"https://Stackoverflow.com/questions/4847977",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/536205/"
] | Checking a variable for logging is perfectly find. Even if the code doesn't get optimised out, checking a boolean condition is almost a no-op and you are very prematurely optimising.
But to answer your question, it probably gets optimised out. | if the statement is unreachable this will always give compile time error.....
eg. if you use return statemnt b4 any code this will give compile time error.
but if you use this type of code
if(aBoolean){
//do something
}
these will not be avoided by java or not removed byjava........ |
297,625 | I have a Ubuntu VirtualBox host and two Ubuntu guests. I need to be able to ssh into both guests and be able to ssh to/from guest1 and guest2.
I'm really stuck. I've tried NAT settings, bridged adapters and host-only adapters.
All I want is for each guest to have its own IP address (e.g. guest1=192.168.56.101 and guest2=192.168.56.102).
Is this possible? | 2011/06/15 | [
"https://superuser.com/questions/297625",
"https://superuser.com",
"https://superuser.com/users/85978/"
] | I am currently running an Ubuntu server (with Gnome installed) running a Windows Server 2003 Active Directory as virtual box host and runs no problem using a bridged connection. The host is on 192.168.1.31 and the guest is on 192.68.1.32. Are you even able ping either of the guest computers from another computer other than the host??? | Using bridged adapters, each guest should get its own IP address from the network (assuming you are using DHCP) as if it were a physical computer. Once you have that address, ssh to it. The config for the host is setting up the bridged adapters.
Like @hydroparadise I do this regularly without issue. |
297,625 | I have a Ubuntu VirtualBox host and two Ubuntu guests. I need to be able to ssh into both guests and be able to ssh to/from guest1 and guest2.
I'm really stuck. I've tried NAT settings, bridged adapters and host-only adapters.
All I want is for each guest to have its own IP address (e.g. guest1=192.168.56.101 and guest2=192.168.56.102).
Is this possible? | 2011/06/15 | [
"https://superuser.com/questions/297625",
"https://superuser.com",
"https://superuser.com/users/85978/"
] | I am currently running an Ubuntu server (with Gnome installed) running a Windows Server 2003 Active Directory as virtual box host and runs no problem using a bridged connection. The host is on 192.168.1.31 and the guest is on 192.68.1.32. Are you even able ping either of the guest computers from another computer other than the host??? | Apparently, I didn't have ssh-server installed. Installing it fixed my issue. |
229,995 | What I'm looking for (and not sure if it's possible) is that we have 16 mapped network drives that are mapped when any user logs on, what I would like is to cut this down to just one visible drive yet leaving the other ones still usable to certain programs. I would just un-map them, however one of our constantly used programs writes to almost all of the drive letters so they need to be mapped for just that program, however they do not need to be visible to the user. Is this possible? | 2011/01/06 | [
"https://superuser.com/questions/229995",
"https://superuser.com",
"https://superuser.com/users/49895/"
] | This can be done with group-policy ([doc](http://support.microsoft.com/kb/231289)). It hides the drives in Windows Explorer, but the drives are still accessible through other means, such as the command-line or API calls from programs. | [Defining Local and Remote Drive Visibility Under Windows NT 4.0 or Windows 2000](http://support.microsoft.com/?id=158457)
>
> The NODRIVES entry (reg\_dword) located in
> **HKEY\_CURRENT\_USER\Software\Microsoft\Windows\CurrentVersion\Policies \Explorer**
>
>
> uses a 32-bit word to define local and network drive visibility for
> each logical drive in the computer.
>
>
> The lower 26 bits of the 32-bit word correspond to drive letters A
> through Z. Drives are visible when set to 0 and hidden when set to 1.
> Drive A is represented by the rightmost position of the bitmask when
> the radix is viewed in binary mode. *Example: A bitmask of
> 10000000000000000000000111(0x7h) The bitmask above hides local drives
> A, B, and C (rightmost bits from right to left) and drive Z (leftmost
> bit).*
>
>
> A bit mask of 11111111111111111111111111 (0x3FFFFFFh) would hide all
> drive letters.
>
>
> Administrators may also use the NODRIVES entry to disable access to
> floppy drives on a per-user basis, replacing functionality previously
> found in the Floplock.exe utility from the Windows NT 3.x resource
> kits.
>
>
> Drives hidden using the NODRIVES setting are not available through
> Windows NT Explorer, under the My Computer icon, or in the File
> Open\Save dialog boxes of Windows applications. File Manager and the
> Windows NT command prompt are not affected by this registry setting.
>
>
> NOTE: If you hide the System drive it is not available under the My
> Computer icon or in the File Open\Save dialog boxes, however it is
> visible in Windows NT Explorer.
>
>
> |
24,549 | 15 days ago I started a batch of wine from a Wine Kit. I went to measure the SG to begin the next step when I found the wine had a film layer at the top. Anyway I phoned the place that sold it to me and am getting a new wine kit tomorrow.
Before I pour this contaminated wine down the toilet, I am wondering if I could finish the process and distill it? Can I do anything to salvage this ~21L of bad juice?
Here's a picture of the contamination, it looked more like a white film before I poked it with a thermometer then it cracked:
[](https://i.stack.imgur.com/UcUoi.jpg) | 2019/10/17 | [
"https://homebrew.stackexchange.com/questions/24549",
"https://homebrew.stackexchange.com",
"https://homebrew.stackexchange.com/users/17696/"
] | It's about different flavor profiles. One is a cleaner ferment simpler flavor profile, the other offers more complexity.
Using the open container to catch wild microbes is definitely hit or miss. The best bet for this type of flavor profile is to get ginger bug from an established source (commercially or a fellow ginger beer brewer). A good strong bug will quickly lower the pH of the solution and limit contaminating issues. | I believe the difference has historical implications. Additionally ginger bug is said to have beneficial healthful properties that are absent in the shortcut recipe. It’s supposed to be much more probiotic.
A bug cultivates the yeasts already present on the ginger root meaning that those yeasts are attracted to ginger and will ferment the ginger itself rather than just fermenting added sugar. |
222,079 | I have a large set of circuits to make using Lithium Ion cells for power. The circuit requires ~12V, which is easily achieved by stacking three cells in series, but the charging circuits I've obtained are little TP4056s which (AFAIK?) can only charge one cell each.
I'd like to avoid having to decouple or remove the batteries for charging, so I thought up the circuit below, basically adding some diodes to separate the cells when they're charging (and the circuit is switched off). I'm basically asking for a sanity check: does adding diodes this way correctly separate the cells? Or am I missing something about how voltage/current will work out, given that all the IN+ and IN– will be paralleled to a 5V supply?
[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fiIsqA.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/) | 2016/03/11 | [
"https://electronics.stackexchange.com/questions/222079",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/103225/"
] | No this won't work because the output from the chargers is not electrically isolated (transformer). The chargers will all share a common ground so the positive from charger 2 will short circuit into the negative of charger 1, and charger 3's positive will short circuit to charger 2's negative.
Your diagram isn't entirely accurate according to the datasheet for the TP4056. The sample wiring diagram on their datasheet clearly shows the battery negative tied to ground. Your diagram shows the negative isolated from the charger inputs which suggests some sort of isolation, but that's not the case.
If you want a quick and dirty way to charge your batteries in this configuration, then I suggest a linear charger monitored by an op-amp or comparator. It's by no means the best way to charge a battery, but it's safe and might be what you're looking for. Here's something to get you started. NOTE, the values and components here are arbitrary. This is just something I threw together.
[](https://i.stack.imgur.com/dYufy.png) | It looks like many people have the same dilemma.
For me its for using/charging LiIon cells in power tools.
My solution is quick and dirty but works.
The ultimate answer is to remove the cells from the device for individual charging in a dedicated (say, 4-cell) charger that charges each cell separately.
So I use a multiple-pin plug/socket depending on how many cells in the tool.
The socket is mounted on the tool, I use a matching plug that is wired to the charger's output for each cell. So that's charging covered.
To use the tool, I insert a blanking plug into the socket that links the cells together in series.
For tools or devices that have less than 4 cells, the system still works, as there are simply less connections in the socket on the device.
As I said - quick and dirty but it works and it is surprisingly easy to use. |
222,079 | I have a large set of circuits to make using Lithium Ion cells for power. The circuit requires ~12V, which is easily achieved by stacking three cells in series, but the charging circuits I've obtained are little TP4056s which (AFAIK?) can only charge one cell each.
I'd like to avoid having to decouple or remove the batteries for charging, so I thought up the circuit below, basically adding some diodes to separate the cells when they're charging (and the circuit is switched off). I'm basically asking for a sanity check: does adding diodes this way correctly separate the cells? Or am I missing something about how voltage/current will work out, given that all the IN+ and IN– will be paralleled to a 5V supply?
[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fiIsqA.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/) | 2016/03/11 | [
"https://electronics.stackexchange.com/questions/222079",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/103225/"
] | No this won't work because the output from the chargers is not electrically isolated (transformer). The chargers will all share a common ground so the positive from charger 2 will short circuit into the negative of charger 1, and charger 3's positive will short circuit to charger 2's negative.
Your diagram isn't entirely accurate according to the datasheet for the TP4056. The sample wiring diagram on their datasheet clearly shows the battery negative tied to ground. Your diagram shows the negative isolated from the charger inputs which suggests some sort of isolation, but that's not the case.
If you want a quick and dirty way to charge your batteries in this configuration, then I suggest a linear charger monitored by an op-amp or comparator. It's by no means the best way to charge a battery, but it's safe and might be what you're looking for. Here's something to get you started. NOTE, the values and components here are arbitrary. This is just something I threw together.
[](https://i.stack.imgur.com/dYufy.png) | Be careful when charging these cells in series. One cell will always win and get overcharged (too many volts.) If left in this state it will possibly explode. Limiting the current is not good enough (power is watts = amps x volts.) To do the job safely place a clamp Zener diode across each cell. Limit the charging circuit to within the recommended current for one cell only. Also use a big Zener just in case. |
222,079 | I have a large set of circuits to make using Lithium Ion cells for power. The circuit requires ~12V, which is easily achieved by stacking three cells in series, but the charging circuits I've obtained are little TP4056s which (AFAIK?) can only charge one cell each.
I'd like to avoid having to decouple or remove the batteries for charging, so I thought up the circuit below, basically adding some diodes to separate the cells when they're charging (and the circuit is switched off). I'm basically asking for a sanity check: does adding diodes this way correctly separate the cells? Or am I missing something about how voltage/current will work out, given that all the IN+ and IN– will be paralleled to a 5V supply?
[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fiIsqA.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/) | 2016/03/11 | [
"https://electronics.stackexchange.com/questions/222079",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/103225/"
] | It looks like many people have the same dilemma.
For me its for using/charging LiIon cells in power tools.
My solution is quick and dirty but works.
The ultimate answer is to remove the cells from the device for individual charging in a dedicated (say, 4-cell) charger that charges each cell separately.
So I use a multiple-pin plug/socket depending on how many cells in the tool.
The socket is mounted on the tool, I use a matching plug that is wired to the charger's output for each cell. So that's charging covered.
To use the tool, I insert a blanking plug into the socket that links the cells together in series.
For tools or devices that have less than 4 cells, the system still works, as there are simply less connections in the socket on the device.
As I said - quick and dirty but it works and it is surprisingly easy to use. | Be careful when charging these cells in series. One cell will always win and get overcharged (too many volts.) If left in this state it will possibly explode. Limiting the current is not good enough (power is watts = amps x volts.) To do the job safely place a clamp Zener diode across each cell. Limit the charging circuit to within the recommended current for one cell only. Also use a big Zener just in case. |
338,237 | Usually if you connect to a Remote Desktop Session Host running on a Windows Server 2008 R2 you will be prompted for your credentials and if they are valid you will be logged in to your session directly.
On one of our servers everyone who logs on with RDP sees the usual Windows Logon Screen (green/blue background with username/password) after already entering them in the Remote Desktop Client. So, users are not directly logged in, but have to enter their credentials twice. It is only the case for this server. The server also is a Remote Desktop Connection Broker.
Is this behavior caused by a wrong setting or do you know how to get rid of it? | 2011/12/06 | [
"https://serverfault.com/questions/338237",
"https://serverfault.com",
"https://serverfault.com/users/63089/"
] | I had a wrong setting enabled: Session Host Configuration -> Select the connection -> properties -> Credentials tab.
Here you can choose where to always ask for credentials or take the credentials provided by the client. | We have that enabled on our of our machines through a GPO. Take a look at this setting: Windows Components/Remote Desktop Services/Remote Desktop Session Host/Security under Computer Configuration/Administrative Templates and look for this setting: Always prompt for password upon connection Enabled |
338,237 | Usually if you connect to a Remote Desktop Session Host running on a Windows Server 2008 R2 you will be prompted for your credentials and if they are valid you will be logged in to your session directly.
On one of our servers everyone who logs on with RDP sees the usual Windows Logon Screen (green/blue background with username/password) after already entering them in the Remote Desktop Client. So, users are not directly logged in, but have to enter their credentials twice. It is only the case for this server. The server also is a Remote Desktop Connection Broker.
Is this behavior caused by a wrong setting or do you know how to get rid of it? | 2011/12/06 | [
"https://serverfault.com/questions/338237",
"https://serverfault.com",
"https://serverfault.com/users/63089/"
] | We have that enabled on our of our machines through a GPO. Take a look at this setting: Windows Components/Remote Desktop Services/Remote Desktop Session Host/Security under Computer Configuration/Administrative Templates and look for this setting: Always prompt for password upon connection Enabled | Check out his link. You can edit the RDP client connection to not display the first windows security logon box.
<http://chall32.blogspot.com.au/2012/04/fixing-remote-desktop-annoyances.html> |
338,237 | Usually if you connect to a Remote Desktop Session Host running on a Windows Server 2008 R2 you will be prompted for your credentials and if they are valid you will be logged in to your session directly.
On one of our servers everyone who logs on with RDP sees the usual Windows Logon Screen (green/blue background with username/password) after already entering them in the Remote Desktop Client. So, users are not directly logged in, but have to enter their credentials twice. It is only the case for this server. The server also is a Remote Desktop Connection Broker.
Is this behavior caused by a wrong setting or do you know how to get rid of it? | 2011/12/06 | [
"https://serverfault.com/questions/338237",
"https://serverfault.com",
"https://serverfault.com/users/63089/"
] | I had a wrong setting enabled: Session Host Configuration -> Select the connection -> properties -> Credentials tab.
Here you can choose where to always ask for credentials or take the credentials provided by the client. | Check out his link. You can edit the RDP client connection to not display the first windows security logon box.
<http://chall32.blogspot.com.au/2012/04/fixing-remote-desktop-annoyances.html> |
165,874 | I'm looking to publish a game on Steam that contains explicit adult content.
I am seeking to make this a hobby that earns passive income as opposed to pursuing it as a full time job. I would prefer that a prospective employer could not easily track my name back to this game and thus not consider me for the job.
I have read the Steamworks Partner Program here:
<https://partner.steamgames.com/steamdirect>
And thus understand that for Steam's sake, I will need to identify myself. But can I publish under some sort of pseudonym to prevent a simple Google Search of my name from returning this game? Or will this pretty much be on my so-called "permanent record" for life? | 2018/12/03 | [
"https://gamedev.stackexchange.com/questions/165874",
"https://gamedev.stackexchange.com",
"https://gamedev.stackexchange.com/users/122784/"
] | Publish your game through a company that you've created rather than directly.
This probably won't make it *completely impossible* for a dedicated sleuth to associate your person with the organization, but it should make it sufficiently difficult that most people won't even try, especially if you are able to engage the services of a third party (such as a law firm) to act as the registered agent of the company.
The details of forming the corporate entity vary by location (as do the types of entities available) so you may need to consult your local government's documentation on the subject. | Another option would be to release the game through a publisher. Ask one of the established developers in that niche if they would like to partner with you. This will likely be a win-win situation for both of you, because both of your games will benefit from cross-promoting each other. Assuming that your games appeal to the same target audience and have about the same level of quality, of course.
Note that in that case Steam will pay the earnings from your game to the publisher, not to you. So you need to make sure you can trust them to hold up their part of the bargain (whatever it is you negotiated).
Also keep in mind that your publisher might agree to conceal your identity from Valve and from the general public, but they are unlikely to protect you in case of any legal issue. |
32,601,523 | Hi I want to send a mail every 5 mins using schedulers in c#,but I don't want to use windows service.how to send a mail every 5 minits. pleae anyone help me. | 2015/09/16 | [
"https://Stackoverflow.com/questions/32601523",
"https://Stackoverflow.com",
"https://Stackoverflow.com/users/5182309/"
] | We obviously are not going to write code for you, but please have a look at this suggestion:
>
> * Write your Console Application that sends Emails.
> * For this have a look at the classes SmtpClient and MailMessage
> * You can also configure Log4Net with an EmailAppender to send Mails
> * Schedule a Task in "Windows Scheduler" to call the Console App every 5 minutes
>
>
> | You can write a simple console application which get's started by the windows task scheduler every 5 minutes. This would be the simplest and most stable way. |
3,050,772 | I have seen many (GENERAL, BEGINNER TYPE) definitions, however, the actual meaning of a sentence I have yet to find, that is non-specific to a particular domain. This would be useful since a statement is defined in terms of a sentence and is one of the first concepts I am introduced to. | 2018/12/23 | [
"https://math.stackexchange.com/questions/3050772",
"https://math.stackexchange.com",
"https://math.stackexchange.com/users/596275/"
] | I would say most texts don't make a difference between the two. In fact: statement, sentence, claim, and proposition are typically all seen as the same thing: something that has a truth-value.
If a text does make a distinction, I suspect it might be between the syntactical expression that we use in order to express a claim, and the claim itself as more of an abstract idea, in much the same ads a number can be expressed in different ways: a numeral is what represent a number. Likewise, one could see a sentence as representing a statement or claim. | In some treatments of mathematical logic where quantified variables appear in the formulas of a language, *statement* may refer to any formula while *sentence* refers specifically to a formula without free variables (i.e. variables not bound by a quantifier). So a statement may say something *about particular objects* under an interpretation of the free variables, while a sentence makes a "general" statement independent of the interpretation of free variables (though it may still say something about particular objects which are *definable* in the language without parameters). However, this is just one convention for the use of the words "statement" and "sentence" and other treatments may use the words differently. |
59,917 | I am using the PIC18F2550 and I wanted to know how much time takes between an event happens (e.g. ADIF)and the interrupt routine starts. In other words, how much time the "interrupt system" takes to change the MCU's state, saving all the registers and changing the Program Counter. | 2013/03/05 | [
"https://electronics.stackexchange.com/questions/59917",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/15955/"
] | Some datasheets tell you the latency from event to interrupt execution explicitly, but this one doesn't seem to. Check the family reference manual; there might be more information in there.
In either case it's pretty quick. Basically the processor takes the next opportunity to execute a call to the interrupt location. The registers that get saved are written to special hardware for that purpose, so that happens overlapped. Basically, the processor has to wait until the start of the next instruction cycle, and there is probably one more to flush the pipeline, then execution resumes at the interrupt address.
If one or two instruction times really matter, then do some tests to see what the latency really is. Remember that events like ADIF are synchronous, so the jitter should be 0. With external asynchronous events there is necessarily one cycle of jitter since the instruction clock keeps running.
What are you doing such that one or two instructions of latency matter? | One good way to answer questions like this is to use MPLAB's simulator. If you enable the stopwatch you can see exactly how many CPU cycles, and how many microseconds everything takes:
 |
59,917 | I am using the PIC18F2550 and I wanted to know how much time takes between an event happens (e.g. ADIF)and the interrupt routine starts. In other words, how much time the "interrupt system" takes to change the MCU's state, saving all the registers and changing the Program Counter. | 2013/03/05 | [
"https://electronics.stackexchange.com/questions/59917",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/15955/"
] | There are two things here: the time before the ISR starts and the time the ISR takes.
When you're using C, the ISR execution time may increase a lot: <http://www.xargs.com/pic/c-faq.html#isrfunc>
However you asked for the time before the ISR starts, which is a few clock cycles. This can be read in section 8.3 of <http://ww1.microchip.com/downloads/en/DeviceDoc/31008a.pdf>:
>
> Interrupt latency is defined as the time from the interrupt event (the interrupt flag bit gets set) to the time that the instruction at address 0004h starts execution (when that interrupt is enabled).
>
>
> For synchronous interrupts (typically internal), the latency is 3TCY.
>
>
> For asynchronous interrupts (typically external), such as the INT or Port RB Change Interrupt, the interrupt latency will be 3 - 3.75TCY (instruction cycles). The exact latency depends upon when the interrupt event occurs (Figure 8-2) in relation to the instruction cycle.
>
>
> The latency is the same for both one and two cycle instructions.
>
>
> | Some datasheets tell you the latency from event to interrupt execution explicitly, but this one doesn't seem to. Check the family reference manual; there might be more information in there.
In either case it's pretty quick. Basically the processor takes the next opportunity to execute a call to the interrupt location. The registers that get saved are written to special hardware for that purpose, so that happens overlapped. Basically, the processor has to wait until the start of the next instruction cycle, and there is probably one more to flush the pipeline, then execution resumes at the interrupt address.
If one or two instruction times really matter, then do some tests to see what the latency really is. Remember that events like ADIF are synchronous, so the jitter should be 0. With external asynchronous events there is necessarily one cycle of jitter since the instruction clock keeps running.
What are you doing such that one or two instructions of latency matter? |
59,917 | I am using the PIC18F2550 and I wanted to know how much time takes between an event happens (e.g. ADIF)and the interrupt routine starts. In other words, how much time the "interrupt system" takes to change the MCU's state, saving all the registers and changing the Program Counter. | 2013/03/05 | [
"https://electronics.stackexchange.com/questions/59917",
"https://electronics.stackexchange.com",
"https://electronics.stackexchange.com/users/15955/"
] | There are two things here: the time before the ISR starts and the time the ISR takes.
When you're using C, the ISR execution time may increase a lot: <http://www.xargs.com/pic/c-faq.html#isrfunc>
However you asked for the time before the ISR starts, which is a few clock cycles. This can be read in section 8.3 of <http://ww1.microchip.com/downloads/en/DeviceDoc/31008a.pdf>:
>
> Interrupt latency is defined as the time from the interrupt event (the interrupt flag bit gets set) to the time that the instruction at address 0004h starts execution (when that interrupt is enabled).
>
>
> For synchronous interrupts (typically internal), the latency is 3TCY.
>
>
> For asynchronous interrupts (typically external), such as the INT or Port RB Change Interrupt, the interrupt latency will be 3 - 3.75TCY (instruction cycles). The exact latency depends upon when the interrupt event occurs (Figure 8-2) in relation to the instruction cycle.
>
>
> The latency is the same for both one and two cycle instructions.
>
>
> | One good way to answer questions like this is to use MPLAB's simulator. If you enable the stopwatch you can see exactly how many CPU cycles, and how many microseconds everything takes:
 |
9,601 | I just moved into a new home that has a backyard composter (about 80 gallons). The composter has been sitting unused for an unknown amount of time (at least 3 months).
How can I assess the health and status of the compost pile, and then what should I do to revive it? | 2019/10/31 | [
"https://sustainability.stackexchange.com/questions/9601",
"https://sustainability.stackexchange.com",
"https://sustainability.stackexchange.com/users/1056/"
] | Dig around in the compost to check the conditions and if the contents are ready to be used. Good compost looks like regular soil and has a light earthy smell. It should not smell badly or be very wet. Unfinished compost has lots of recognizable pieces still in it.
Most likely the majority of materials left in the composter are transformed into compost by now and can be applied directly to your garden. Since you don't know what the original materials were I personally would not use it in a vegetable garden, only in other parts of your garden, but I am rather picky about what I add to plants my family and I eat. I tend to compost only organic material.
You did not say what kind of composter you have; a sealed bin or something placed directly on the ground with open bottom. If it's a sealed bin you can choose between regular composting and [vermicomposting](https://sustainability.stackexchange.com/tags/vermicomposting/info). If it's directly on the ground, worms will find their way into your heap by themselves.
There is no need to revive anything. If the bin is not smelling you can add new materials straight away, but personally I would empty it first and then start from scratch so I know exactly what the resulting compost is made of. If you want to do vermicomposting in a closed bin make sure you have some soil and worms as starter material. For regular (hot) composting soil as starter is not a necessity, but is [recommended because decomposition will start quicker](https://sustainability.stackexchange.com/q/15/99). | I agree it is a good idea not to use the compost left in the bin on anything edible or valuable. Just scrape it out and start again. They might have been composting meat, in which case it will be full of maggots and harmful bacteria. The idea is, if it smells spread it out in an out of the way place and let the air and the worms get to it. |
9,601 | I just moved into a new home that has a backyard composter (about 80 gallons). The composter has been sitting unused for an unknown amount of time (at least 3 months).
How can I assess the health and status of the compost pile, and then what should I do to revive it? | 2019/10/31 | [
"https://sustainability.stackexchange.com/questions/9601",
"https://sustainability.stackexchange.com",
"https://sustainability.stackexchange.com/users/1056/"
] | Dig around in the compost to check the conditions and if the contents are ready to be used. Good compost looks like regular soil and has a light earthy smell. It should not smell badly or be very wet. Unfinished compost has lots of recognizable pieces still in it.
Most likely the majority of materials left in the composter are transformed into compost by now and can be applied directly to your garden. Since you don't know what the original materials were I personally would not use it in a vegetable garden, only in other parts of your garden, but I am rather picky about what I add to plants my family and I eat. I tend to compost only organic material.
You did not say what kind of composter you have; a sealed bin or something placed directly on the ground with open bottom. If it's a sealed bin you can choose between regular composting and [vermicomposting](https://sustainability.stackexchange.com/tags/vermicomposting/info). If it's directly on the ground, worms will find their way into your heap by themselves.
There is no need to revive anything. If the bin is not smelling you can add new materials straight away, but personally I would empty it first and then start from scratch so I know exactly what the resulting compost is made of. If you want to do vermicomposting in a closed bin make sure you have some soil and worms as starter material. For regular (hot) composting soil as starter is not a necessity, but is [recommended because decomposition will start quicker](https://sustainability.stackexchange.com/q/15/99). | If you're concerned your compost pile is no longer biologically active, restart it.
There's bacterial start up's that can easily be purchased. Another way to speed it up is to Heat it up. Fresh urine (98.6 degree's) can activate a pile too, another strategy is to use hot water; because temperature drives thermophilic activity.Dig a donut shaped hole in your pile Boil some water and soak a big piece of crumbled up cardboard, hen immediately add the cardboard to the bottom and press it like a bowl and dump the hot water then back fill the hole and add the bacteria. Heat rises so a warm environment is perfect for them. Also you've mixed and there fore aerated the pile |
9,601 | I just moved into a new home that has a backyard composter (about 80 gallons). The composter has been sitting unused for an unknown amount of time (at least 3 months).
How can I assess the health and status of the compost pile, and then what should I do to revive it? | 2019/10/31 | [
"https://sustainability.stackexchange.com/questions/9601",
"https://sustainability.stackexchange.com",
"https://sustainability.stackexchange.com/users/1056/"
] | I agree it is a good idea not to use the compost left in the bin on anything edible or valuable. Just scrape it out and start again. They might have been composting meat, in which case it will be full of maggots and harmful bacteria. The idea is, if it smells spread it out in an out of the way place and let the air and the worms get to it. | If you're concerned your compost pile is no longer biologically active, restart it.
There's bacterial start up's that can easily be purchased. Another way to speed it up is to Heat it up. Fresh urine (98.6 degree's) can activate a pile too, another strategy is to use hot water; because temperature drives thermophilic activity.Dig a donut shaped hole in your pile Boil some water and soak a big piece of crumbled up cardboard, hen immediately add the cardboard to the bottom and press it like a bowl and dump the hot water then back fill the hole and add the bacteria. Heat rises so a warm environment is perfect for them. Also you've mixed and there fore aerated the pile |
1,576,336 | I want to build my own laptop from scratch. How would you go about it, or what would you advise me to do? (and please don't say: buy a new/refurbished one)
* Is it handy to combine elements of several brands?
* Should I stick to just one brand or several?
* is it possible to find a generic casing?
Thanks. | 2020/08/09 | [
"https://superuser.com/questions/1576336",
"https://superuser.com",
"https://superuser.com/users/358839/"
] | I would suggest looking into 'barebones' laptops. They include the bare minimum of parts (usually at least a motherboard and CPU), allowing you to do the rest yourself. There are a bunch of companies that sell them in varying degrees of completion, but the only one I know off the top of my head is Clevo. They are what a lot of the companies who sell customized laptops, such as Sager, use as a base.
As far as brands go, it depends what you mean. Some CPUs play better with certain motherboards than others, and I think the same goes for video cards (sorry, it's been a long time since I've bought one). Your RAM sticks should definitely be the same, ideally identical. For hard drives, the brand shouldn't matter as far as compatibility goes. There are only a few major brands and I've never had any issues mixing and matching.
The main parts to worry about compatibility with are the motherboard, CPU, and RAM. A quick Google search can usually tell you what a certain model will work with. | >
> Is it handy to combine elements of several brands?
>
>
>
Apart from a few parts (RAM, SSD, CPU..), **no**, parts like keyboard, motherboard, battery... are not interchangeable, often exists several standards even within brands
>
> Should I stick to just one brand or several?
>
>
>
As mentioned above, even within one brand parts might not be compatible.
>
> is it possible to find a generic casing?
>
>
>
I'm not aware of that. |
30,746 | We are told that when people die, their body stays in their grave and their soul goes to barzakh where they wait for the day of judgement. After that people enter either Jannah or Jahannam. However during Isra' wal Miraj, the Prophet (saw) traveled to Jannah and Jahannam. I understand that the Prophets are in Jannah already as there may be an exception for them. However Muhammad (saw) also saw people suffering in Jahannam too.
So my question is how or why were there people already in Jahannam when the soul waits in Barzakh after death? | 2016/04/09 | [
"https://islam.stackexchange.com/questions/30746",
"https://islam.stackexchange.com",
"https://islam.stackexchange.com/users/5187/"
] | I don't know what our Prophet saw, so I can't comment about that but if you read Quran, you will see that in many verses, Allah describes the judgment day, heaven and hell as if they already happened. Please check **Quran** verses **6:27, 6:30, 6:128, 7:44, 18:99, 21:100, 22:22, 23:102-108** and many others.
**My understanding** is that it already happened from Allah's perspective, but not from our (humans and other creation in this universe) perspective. **My understanding** is that it all already happened and recorded (e.g. video recordings, server logs, book registries, in a way we can't fully understand) by Allah and that information is available to Allah any time. Please check Quran verses **6:59, 10:61, 36:12, 57,22**. Surely Allah can show it to anyone, if Allah wishes. However, we (both living and the dead) are still proceeding in time towards the judgment day and heaven and hell. **My understanding** is that, from our perspective nobody is in the heaven or hell yet, as the judgment did not took place yet. Please check Quran verses **36:52, 23:112-23:113**.
A director of the movie knows what will happen at the end of the movie but a viewer has to go through the movie and reach its end to know it. | Right. Before Judgement Day, no one is in Paradise getting the full taste of Paradise as it will be experienced, or the full taste/experience of Hell.. including those who are exceptions, as you mentioned. -- The scholars say that when the Prophet (ﷺ) "saw" the people in Paradise and the People in Hellfire, it was something shown to him via vision/knowledge from Allah (ﷻ).. of what is to come (and wasn't something that was happening currently when he saw it). The Prophet (ﷺ) then conveyed that to us. Just another way to show us the realities of the two places and what can be expected. SubhanAllah. |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | Make Mars a double planet. Or Venus, or of you do not care about Earth much, replace the Moon with the planet. The previous stability should remain more or less the same, apart from some disturbances that might or might not manifest in the long term (as long as the resonances remain stable, you do not have much to worry about). | The planet would be able to be the most stable in a orbit between earth and Mars because that the biggest gap between notable celestial bodies of the inner solar system. So gravitation pull of any bodies would be most minimal hence being able to keep a steady orbit as long as the sun lives.
Edit:I apologize by I messed up(dyslexic). It rather crowded between mars and the belt you best bet would be between earth and mars.
Another solution would to have an orbit perpendicular of all the other orbit since most bodies in this system tend to stay on one plane. |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | There is a book about the possibility of human habitable exo planets around other stars. *Habitable Planets for Man*, Stephen H. Dole, 1964.
<https://www.rand.org/content/dam/rand/pubs/commercial_books/2007/RAND_CB179-1.pdf>
On pages 46 to 52 Dole writes about the spacing of the planets in the Solar System as it was understood in the early 1960s. Dole estimates that the forbidden zones around the planets take up ab about 50 percent of the volume of the Solar System, leaving about another 50 percent which might possibly be occupied by other planets under some conditions.
According to Dole's calculations, the more massive the planet, the larger its forbidden zones, and the farther the planet is from the Sun, the larger its forbidden zone will be. And the more eccentric the planet's orbit is, the larger its forbidden zone will be. The mass of the star is also a factor.
Table 8 on page 50 gives the inner and outer edges of the forbidden zones of the planets. As nearly as I can read the tiny numbers in the table, the gaps between the forbidden zones are wider than the forbidden zones for the inner planets.
Figure 18 on page 51 indicates that there is room for a roughly Earth mass planet and its forbidden zone between the orbits of Mercury and Venus, between the orbits of Venus and Earth, between Earth and Mars, and beyond Mars. It might be possible to put two Earth mass planets and their forbidden zones between Mars and Jupiter.
None of the forbidden zones overlap, except for those of Neptune and Pluto, and the orbit of Pluto is tilted considerably compared to that of Neptune.
I note that it would be unlikely for major planets to form with orbits where their forbidden zones overlap, because those overlapping forbidden zones would interfere with he formation of the planets out of smaller objects.
But if aliens build a new planet in our solar system by using spaceships to move smaller objects into place and assemble a planet out of them, or if the super advanced aliens open a portal to move an already formed planet from a distant star system to an orbit among the already formed planets in our solar system having partially overlapping forbidden zones might not matter much. | The planet would be able to be the most stable in a orbit between earth and Mars because that the biggest gap between notable celestial bodies of the inner solar system. So gravitation pull of any bodies would be most minimal hence being able to keep a steady orbit as long as the sun lives.
Edit:I apologize by I messed up(dyslexic). It rather crowded between mars and the belt you best bet would be between earth and mars.
Another solution would to have an orbit perpendicular of all the other orbit since most bodies in this system tend to stay on one plane. |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | If you have the resources to create or bring a new planet - generally, wherever you feel like. You will be probably able to maintain the orbital stability as well.
On the other hand, if you are limited in long-term expenses, the orbital stability becomes an issue. And there, the answer becomes "nowhere in the habitable zone".
Mercury, Venus, Earth and Mars are in a complex orbital relationship, maintained by constant exchange of momentum between the planets. There are hints that the solar cycle is related to the tides the first 3 planets exert at the Sun as well.
How can one save the plot, then?
* Replace Venus / terraform Venus. It is Earth-mass and with some added water and without the greenhouse effect can be pretty much habitable. And only slightly hotter than the Earth (if at all).
* Make Mars double. Mars is not much different than the Moon in both mass and composition. Put an Earth-sized planet there and allow Mars to orbit around. A heavier body in the place of Mars will likely have only minor effect on the Earth's orbit. The two Mars moons can be put in an orbital resonance with Mars (3-moon world?), mined into oblivion or stored in the asteroid belt until better ideas arise.
* A combination thereof (replace Venus, store Venus near Mars where it can cool off for a while).
Beyond Mars it's rather cold, but if you don't mind that, the asteroid belt itself is a place. Not a place to have a planet on its own, but pretty much a place where a planet would be stable. Vacuum it first or prepare for a serious meteorite shower later. You can use the collected material for a little fancy moon as well.
Beyond the asteroid belt it is really, really cold, in particular too cold for almost any type of atmosphere or hydrosphere. If you can bear the heating bill, neither Jupiter, nor Saturn, nor the ice giants beyond, will mind an Earth mass satellite. You will have to rearrange the moon zoo there first in order to avoid crashes.
Don't put anything heavy below Venus orbit even if you don't mind the heat. We like our calendar and seasons pretty much. Thank you in advance. | The planet would be able to be the most stable in a orbit between earth and Mars because that the biggest gap between notable celestial bodies of the inner solar system. So gravitation pull of any bodies would be most minimal hence being able to keep a steady orbit as long as the sun lives.
Edit:I apologize by I messed up(dyslexic). It rather crowded between mars and the belt you best bet would be between earth and mars.
Another solution would to have an orbit perpendicular of all the other orbit since most bodies in this system tend to stay on one plane. |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | The planet would be able to be the most stable in a orbit between earth and Mars because that the biggest gap between notable celestial bodies of the inner solar system. So gravitation pull of any bodies would be most minimal hence being able to keep a steady orbit as long as the sun lives.
Edit:I apologize by I messed up(dyslexic). It rather crowded between mars and the belt you best bet would be between earth and mars.
Another solution would to have an orbit perpendicular of all the other orbit since most bodies in this system tend to stay on one plane. | This is a cool question. The short answer is: probably not.
The long answer requires us to consider a few things:
1. Are the current planets stable?
----------------------------------
To discuss this we first need to understand something about dynamical chaos. Let's imagine a situation where you're trying to predict whether a skilled soccer player will make a goal. Furthermore, let's say you're a particular enterprising soccer fan and consequently you know the direction they will kick and the power of kick with some accuracy. In addition, you measured the goal beforehand and know what its boundaries are. If you know all these initial conditions precisely you could simply run a simulation to predict the position of the ball over time and determine - for certain - whether the player makes the goal or not.
Now let's complicate the situation: instead of knowing the initial conditions perfectly, say there is some error. If you conduct your simulation in this case you'll find there are some cases where the ball ends up in the goal, and some cases where it does not. Even if we know exactly how to do the physics, Even if our simulation is perfect, the position of the ball at any given time in the future will be uncertain simply because the initial conditions are.
The solar system as a whole exhibits something called chaos, which, at the risk of oversimplifying, is fundamentally just a version of this same effect we found with the soccer player. The difference is that in the case of chaotic systems the error in a subsequent state grows quickly (typically exponentially) in time. Hence, dynamical studies of the solar system typically involve comparing large sets of simulations statistically - while we can't be confident in any individual simulation - the overall ensemble is interpretable!
[](https://i.stack.imgur.com/7d3Rp.png)
Below is a plot from a paper by [Laskar, J. & Gastineau, M.](https://ui.adsabs.harvard.edu/abs/2009Natur.459..817L/abstract) unfortunately behind paywall. They integrated identical copies of the solar system for 5 billion years with the only difference being that they shifted initial position of the planet Mercury by just a few meters between simulations. The plots show the resulting maximum eccentricity of the Mercury over time (first panel is using just Newtonian mechanics, and the second panel is using General Relativity). In either case, there are many cases where the eccentricity of mercury can grow extremely large, and most of these cases result in either ejection from the solar system or collision with another planet.
This implies that the current planets - just the 4 we have - aren't super stable as is. This isn't to say that the solar system will definitely shake itself apart - but it does show that the unstable trajectories are possible given what we know about the current state of the solar system.
2. Alright, but what about adding another one?
----------------------------------------------
If we wish to consider the addition of another planet, what's critical is its mass. If the new body has a small mass, it won't really destabilize the orbits of the more massive bodies, and it has a better chance of surviving. There are regions like this in the solar system - for example the "Earth-Mars Belt" (you can read the paper [here](https://arxiv.org/abs/2010.01225): since it's public), a region between ~1.09 and ~1.17 AU where small bodies might be able to survive for billions of years.
Finally, we get to your case - what if the added body is the size of the earth? In this case, the body not only needs to survive, but it also has to do so in a system that is being destabilized by its own (earth sized!) gravitational field. Given that the solar system without such a body is barely stable, the addition of such a large body would almost destabilize the entire inner solar system - probably impacting another planet or being ejected. While the only way to find out for sure would be to run a ton of very time-consuming simulations, I'd be very skeptical that such a situation is possible.
3. What about resonances?
-------------------------
There are some situations where planets can be found in what are called "Mean-Motion Resonances" with each other, and this tends to permit stability even in very closely packed systems. The poster child for this type of behavior is the Trappist-1 system, which exhibits several small planets all in resonance with each other. While such a configuration cannot be realized by simply adding a planet to our solar system - it is conceivable that there could exist systems in general with planets more tightly packed than what we have.
\*\*This answer is reproduced from a similar [question](https://astronomy.stackexchange.com/questions/50292/could-a-planet-theoretically-have-a-stable-orbit-between-venus-and-earth-or-eart/50326#50326) on the Astronomy StackExchange |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | Make Mars a double planet. Or Venus, or of you do not care about Earth much, replace the Moon with the planet. The previous stability should remain more or less the same, apart from some disturbances that might or might not manifest in the long term (as long as the resonances remain stable, you do not have much to worry about). | If you have the resources to create or bring a new planet - generally, wherever you feel like. You will be probably able to maintain the orbital stability as well.
On the other hand, if you are limited in long-term expenses, the orbital stability becomes an issue. And there, the answer becomes "nowhere in the habitable zone".
Mercury, Venus, Earth and Mars are in a complex orbital relationship, maintained by constant exchange of momentum between the planets. There are hints that the solar cycle is related to the tides the first 3 planets exert at the Sun as well.
How can one save the plot, then?
* Replace Venus / terraform Venus. It is Earth-mass and with some added water and without the greenhouse effect can be pretty much habitable. And only slightly hotter than the Earth (if at all).
* Make Mars double. Mars is not much different than the Moon in both mass and composition. Put an Earth-sized planet there and allow Mars to orbit around. A heavier body in the place of Mars will likely have only minor effect on the Earth's orbit. The two Mars moons can be put in an orbital resonance with Mars (3-moon world?), mined into oblivion or stored in the asteroid belt until better ideas arise.
* A combination thereof (replace Venus, store Venus near Mars where it can cool off for a while).
Beyond Mars it's rather cold, but if you don't mind that, the asteroid belt itself is a place. Not a place to have a planet on its own, but pretty much a place where a planet would be stable. Vacuum it first or prepare for a serious meteorite shower later. You can use the collected material for a little fancy moon as well.
Beyond the asteroid belt it is really, really cold, in particular too cold for almost any type of atmosphere or hydrosphere. If you can bear the heating bill, neither Jupiter, nor Saturn, nor the ice giants beyond, will mind an Earth mass satellite. You will have to rearrange the moon zoo there first in order to avoid crashes.
Don't put anything heavy below Venus orbit even if you don't mind the heat. We like our calendar and seasons pretty much. Thank you in advance. |
234,860 | Assume there was a super advanced alien race that for some reason, wanted to add a new planet, of lets say 1 Earth mass, into the Solar System. Where in the inner Solar System *(The part of the solar system inside Jupiter's orbit, so asteroid belt is included)* could we put this planet, so that it would have a stable orbit for billions of years?
*Note: I would preferably not want have this planet orbit closer to the sun than Mercury, and would like for it to affect the inner planets as little as possible, although I care more about the first condition rather than the second.*
*And also, the planet needn't be habitable* | 2022/08/26 | [
"https://worldbuilding.stackexchange.com/questions/234860",
"https://worldbuilding.stackexchange.com",
"https://worldbuilding.stackexchange.com/users/96111/"
] | Make Mars a double planet. Or Venus, or of you do not care about Earth much, replace the Moon with the planet. The previous stability should remain more or less the same, apart from some disturbances that might or might not manifest in the long term (as long as the resonances remain stable, you do not have much to worry about). | This is a cool question. The short answer is: probably not.
The long answer requires us to consider a few things:
1. Are the current planets stable?
----------------------------------
To discuss this we first need to understand something about dynamical chaos. Let's imagine a situation where you're trying to predict whether a skilled soccer player will make a goal. Furthermore, let's say you're a particular enterprising soccer fan and consequently you know the direction they will kick and the power of kick with some accuracy. In addition, you measured the goal beforehand and know what its boundaries are. If you know all these initial conditions precisely you could simply run a simulation to predict the position of the ball over time and determine - for certain - whether the player makes the goal or not.
Now let's complicate the situation: instead of knowing the initial conditions perfectly, say there is some error. If you conduct your simulation in this case you'll find there are some cases where the ball ends up in the goal, and some cases where it does not. Even if we know exactly how to do the physics, Even if our simulation is perfect, the position of the ball at any given time in the future will be uncertain simply because the initial conditions are.
The solar system as a whole exhibits something called chaos, which, at the risk of oversimplifying, is fundamentally just a version of this same effect we found with the soccer player. The difference is that in the case of chaotic systems the error in a subsequent state grows quickly (typically exponentially) in time. Hence, dynamical studies of the solar system typically involve comparing large sets of simulations statistically - while we can't be confident in any individual simulation - the overall ensemble is interpretable!
[](https://i.stack.imgur.com/7d3Rp.png)
Below is a plot from a paper by [Laskar, J. & Gastineau, M.](https://ui.adsabs.harvard.edu/abs/2009Natur.459..817L/abstract) unfortunately behind paywall. They integrated identical copies of the solar system for 5 billion years with the only difference being that they shifted initial position of the planet Mercury by just a few meters between simulations. The plots show the resulting maximum eccentricity of the Mercury over time (first panel is using just Newtonian mechanics, and the second panel is using General Relativity). In either case, there are many cases where the eccentricity of mercury can grow extremely large, and most of these cases result in either ejection from the solar system or collision with another planet.
This implies that the current planets - just the 4 we have - aren't super stable as is. This isn't to say that the solar system will definitely shake itself apart - but it does show that the unstable trajectories are possible given what we know about the current state of the solar system.
2. Alright, but what about adding another one?
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If we wish to consider the addition of another planet, what's critical is its mass. If the new body has a small mass, it won't really destabilize the orbits of the more massive bodies, and it has a better chance of surviving. There are regions like this in the solar system - for example the "Earth-Mars Belt" (you can read the paper [here](https://arxiv.org/abs/2010.01225): since it's public), a region between ~1.09 and ~1.17 AU where small bodies might be able to survive for billions of years.
Finally, we get to your case - what if the added body is the size of the earth? In this case, the body not only needs to survive, but it also has to do so in a system that is being destabilized by its own (earth sized!) gravitational field. Given that the solar system without such a body is barely stable, the addition of such a large body would almost destabilize the entire inner solar system - probably impacting another planet or being ejected. While the only way to find out for sure would be to run a ton of very time-consuming simulations, I'd be very skeptical that such a situation is possible.
3. What about resonances?
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There are some situations where planets can be found in what are called "Mean-Motion Resonances" with each other, and this tends to permit stability even in very closely packed systems. The poster child for this type of behavior is the Trappist-1 system, which exhibits several small planets all in resonance with each other. While such a configuration cannot be realized by simply adding a planet to our solar system - it is conceivable that there could exist systems in general with planets more tightly packed than what we have.
\*\*This answer is reproduced from a similar [question](https://astronomy.stackexchange.com/questions/50292/could-a-planet-theoretically-have-a-stable-orbit-between-venus-and-earth-or-eart/50326#50326) on the Astronomy StackExchange |
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