Recently, I've posted this question : Influence of device upon another device from power supply. This question was closed for being "unclear". What is unclear in this question ? I did my best to exactly describe the situation I may be faced with. I can add nothing more to clarify the problem since I don't know by myself the exact devices that will be used. This question may have a certain level of generality, it may be thought to be relatively broad, but it is not unclear ! As a professional mathematician, I am used with the fact that any question can be given an answer, which should receive exactly the same level of generality and fuzziness as the question. I feel that some persons in this site are confusing "general questions" with "unclear questions".

N.B: I have requested the downvoters to clarify by a comment what is unclear to them (as is traditional in other stack exchange forums), but they ignored my request.

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First note that voting here is secret and that no [down]voter is obliged to explain themselves; pestering them to do so will likely attract more downvotes though.

Your question essentially says "I connect A to B and B to C, how exactly will C influence A?". Keep in mind that we are an engineering site here, and don't do philosophical fuzzyness. If we did, the answer to your question would be "The more you do stuff that influences A on C, the more you will influence A with it".

Your question is not so much unclear in that we don't know what you want to know, but in that you provide absolutely no detail for us to be able to answer it. Going into your realm of mathematics, you could ask "I have a function with variables a, b and c, what are its zeros?". The only valid answer would clearly be a book outlining all possible ways to determine a zero of a function with three variables. And boy would that book be big...

We don't do that in engineering. Besides that we especially don't do that on this site, since we only have 30k characters for an answer. In engineering we answer practical answerable questions that involve actual things, parameters, procedures.

One could argue that we could answer with endless descriptions of what kind of actions do or don't do and to what extend and in what situation and with what involved power supplies etc. do, but we don't do that here either, it would be open ended and leads to nothing.

Thus, your question was not only closed for being unclear what you do exactly, valid close reasons involved also too broad, and if it existed the lack of prior research (or evidence thereof). But it is sufficient for the system to only chose one.

Ask again here if you know what kind of power supply you have and what the nature of the current draw on it is, and when you have sorted out the basics about things like voltage drop etc.

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    \$\begingroup\$ 1) I'm not pestering any person to answer, but it is TRADITIONAL to indicate in a comment what is wrong, or to request some clarification (the term "pestering" is at the least exaggerated in view of the gentle request I've put in comment in the thread) \$\endgroup\$ – MikeTeX Aug 17 '15 at 19:31
  • \$\begingroup\$ 2) I did provide some details about the power supply : ATX, like the one in your PC. I did not indicate how much voltage is applied to such and such electrode because this is not the aim of the question. What is demanded here is the "feeling" of experienced persons, if they have experienced such problems in similar situations etc. I think you and your friends have a personal narrow interpretation of what is "electrical engineering". And your comparison with mathematical function is only of sophistical nature. \$\endgroup\$ – MikeTeX Aug 17 '15 at 19:46
  • \$\begingroup\$ 3) I've read somewhere in your posts that you (and probably many other experts, this is not personal) are irritated by some types of questions, that could be qualified as "not professional". I can easily understand this, but this site does not claim to be only for professionals. My question can very probably be classified in the "undergraduate student category", and certainly in the "enthusiastic person" one. A stack exchange forum like "Mathoverflow" for professional electrical engineers only is probably lacking. Why not create it ? \$\endgroup\$ – MikeTeX Aug 17 '15 at 20:10
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    \$\begingroup\$ @MikeTeX: if you want another stack, go to area51 and propose it. Most people do never explain their downvotes, as then they would spend 24 hours writing explanation no one will care about. "ATX" is as useful as "laboratory power supply" i.e. not useful at all for behaviour classification. And while this site surely is not only for professionals, we expect a somewhat professional attitude and a good indication of prior research. You might want to read meta.electronics.stackexchange.com/questions/5306 too. \$\endgroup\$ – PlasmaHH Aug 17 '15 at 20:51
  • \$\begingroup\$ (god we need longer comments on meta). For your specific case, an enthusiast would surely think more about what is necessary to answer the question and come to the conclusion that it depends on what A and C do to B to decide whether A influences C or not. \$\endgroup\$ – PlasmaHH Aug 17 '15 at 20:52
  • \$\begingroup\$ Please, wikipedia (en.wikipedia.org/wiki/ATX) to see the specifications for ATX power supply. Beside, every electronic tinker knows what is the meaning of "ATX power supply" : even if this is not a very professional way to specify things, this is clear for many persons. And no, the question does not amount to "A and C do to B etc." : this kind of PSU has a circuitry that stabilizes the voltage, and is said to be "incredibly stable" in several places on the web. And no, the answer of this question can not be found by some REASONABLE "prior research" : I have spent hours to do so. \$\endgroup\$ – MikeTeX Aug 17 '15 at 21:11
  • \$\begingroup\$ Oh, I've forgotten: I don't want another stack, this is probably some experts in this forum that want so. \$\endgroup\$ – MikeTeX Aug 17 '15 at 21:13
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    \$\begingroup\$ @MikeTeX: "incredibly stable" is nowhere any reasonable spec. Take any voltage regulator spec and look what different parameters they specify. This is similar for all power supplies. ATX is a specification mostly for a plug, not for voltage stability. All it says that it outputs e.g. 12V +- 5%. Not my definition of "incredibly stable". I just connected some ATX PSU I had been lying around and its voltage dropped by 600mV when fully loaded. Not "incredibly stable" too. And about all brands and models use different circuitry to provide that "stable" voltage and behave differently when loaded \$\endgroup\$ – PlasmaHH Aug 17 '15 at 21:21
  • \$\begingroup\$ My question was not if a common ATX PSU is or is not incredibly stable : I simply explained above why my question was a bit more involved than your famous "A and C do to B etc.". \$\endgroup\$ – MikeTeX Aug 17 '15 at 21:30
  • \$\begingroup\$ (god, we need more that 5 min to re-edit a comment on meta). You are right that the question amounts, ultimately, to the stability of the PSU, but this was not so clear to me, mainly because I was influenced by what I had read about the stability of ATX PSU. This also probably explains why I missed the specification +-5% in Wikipedia. Anyway, wasn't it exactly the answer to the question : "+- 5% stability" ? \$\endgroup\$ – MikeTeX Aug 17 '15 at 21:57
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    \$\begingroup\$ @MikeTeX: no, because that is what the ATX spec allows, now what your PSU model actually does. Some are within 5% with their oltage, but regulate within 0.1% to that. Also this is just an input into judging how one load on that PSU will affect the other. We still don't know the loads, so we can't tell if the regulation of any PSU is good enough to make the loading effect negligable. \$\endgroup\$ – PlasmaHH Aug 17 '15 at 22:45
  • \$\begingroup\$ Asking about an order of magnitude is legitimate, and a numeric answer is not mandatory. In another SE forum, one would have probably put a small comment like : "Your question amounts to the stability of the PSU: see spec of your PSU", and the problem would have been solved without clash. Sometimes, students and enthusiastic persons need a small push to make 1+1=2. I understand that this is far from being an expert question, but this forum takes the place of a non (necessarily) expert electrical engineering in SE. I really think that such a SE forum for professionals only should be created. \$\endgroup\$ – MikeTeX Aug 18 '15 at 6:58
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    \$\begingroup\$ @MikeTeX: This is the forum for professionals. If you need one for absolute beginners that need handholding, then as I said, there is area51 for proposals. It is neither unfair nor unreasonable to expect some prior research here to not have to start at adam and eve. And if a question looks like the poster has no idea about ohms law and its application, that is not a good start. Besides that, questions are not out of context, if it comes with a flood of other crappy questions that need to be nuked from the orbit, then people are not as lenient as when they digested lots of good content that day \$\endgroup\$ – PlasmaHH Aug 18 '15 at 8:05
  • \$\begingroup\$ No, this is not the forum for professionals because it does not claim so, and I can't go to area51 because the place is already occupied by this forum. Definition of enthusiastic from Vicon dictionary (say) "intensely interested" NO MORE, the rest is your personal interpretation, similarly, a student may be a first day in the first year student, that's the facts, and you can not change the definition of words. The truth is that a group of professional have decided to be "irritated" by simple questions and newcomers, and to appropriate to themselves this forum. \$\endgroup\$ – MikeTeX Aug 18 '15 at 11:59
  • \$\begingroup\$ I know Ohm's laws and much more ; in fact, I know possibly much more of theoretical physics that you or other professionals in this site. Please, stop trying humiliate me by this kind of BAD sophistic. Of the few questions I have posted in this forum, only the one closed by thephoton was probably really out of topic. \$\endgroup\$ – MikeTeX Aug 18 '15 at 12:08

The question was unclear (or perhaps better "too broad") because its impossible to know how to answer it unless we know what the devices in question are. Our help center specifies that the site is to "Get answers to practical, detailed questions". This question wasn't practical because it wasn't detailed enough.

You would have had better luck if you said "I want to power a radio and TV with the same ATX power supply. Will I have trouble?" You may have been prompted for more detail, and probably would not have been closed had you provided it. Better yet would be "I tried X, and I'm having problem Y. How can I fix it?"

"Practical" is sort of an antonym for "hypothetical". We're not good at the latter, and you asked a hypothetical question. If you have real concerns, we'll help you if you can give us enough real details.

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  • \$\begingroup\$ This is not a hypothetical question : I am funding a small laboratory to realise some project ; I have built a nice 36V 15A PSU with 3 ATX PSU, and I wanted to know to what extent 2 persons can use it in parallel. If you have followed the comments above, then you may have noticed that the question does has a precise answer : +- 5%, as an order of magnitude. I also admitted that this turned out to be a very elementary question, but only after it was made clear that this amounts to the stability of the PSU. And I have demonstrated that no one can pretend this is a forum for professionals only. \$\endgroup\$ – MikeTeX Aug 18 '15 at 20:08
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    \$\begingroup\$ @MikeTeX -- we differ on what detailed is. To answer the question, we need to know detail about the loads, even more than about the power supply. If you're trying to realise some project, and you know what the supply needs to be used for, share that. I glanced through the comment thread above, and didn't really feel a need to be part of it, and I tried very hard to make no point about who the forum is for. \$\endgroup\$ – Scott Seidman Aug 18 '15 at 20:13
  • \$\begingroup\$ (Written before the above answer was posted). I asked at least 2 questions in this forum that may (and probably will) be useful to others in the future : the one about literature on PHEMT transistors, and the one about RF devices to measure distances with high precision. But I was continuously, deliberately, downvoted by some persons (included this thread), which are doing their best to make me banned. I think this is simply a shame. \$\endgroup\$ – MikeTeX Aug 18 '15 at 20:13
  • \$\begingroup\$ Answer to Scott Seidmann. OK, it's your opinion : for you, only answers like x = 3 are valid; for me, an answer like x <= 3 is valid as well. \$\endgroup\$ – MikeTeX Aug 18 '15 at 20:17
  • \$\begingroup\$ @MikeTeX -- I'm responding to the one question you posted here in meta as an example, not reviewing your posting history, or judging you as a user. Downvotes in meta, by convention here and on many groups, simply mean "I disagree with that line of thought" \$\endgroup\$ – Scott Seidman Aug 18 '15 at 20:19
  • \$\begingroup\$ OK. So, I except the downvotes about this thread. \$\endgroup\$ – MikeTeX Aug 18 '15 at 20:25

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