FYI: case wiring

May 31, 2009 at 20:12:32
Specs: Windows
I've read a few articles on here that are very misleading about this issue. Depending on the connector being installed, the polarity of the wiring makes A HUGE difference. For example, so far I have blown the fuse of 2 power supplies because the POWER and RESET switch connectors were polarized incorrectly. In a previous case before I have destroyed my board completely and some of the add-on cards that were installed as well.

The polarity of the LED or indicator lights don't matter as much, as they just won't light up if they are incorrect.

So far the white being negative charge seems to be correct as I no longer have the problem. If you don't know please say YOU DON'T KNOW as you look more stupid saying you know when you clearly don't.


See More: FYI: case wiring

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#1
May 31, 2009 at 20:30:37
Power on and reset switches on an ATX compliant case are not polarity sensitive since all they do is provide a momentary contact to complete a circuit between the related header pins on the motherboard. If you've been blowing fuses and burning out motherboards it is because you have done something else wrong.

Goin' Fishin' (Some day)


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#2
May 31, 2009 at 20:37:57
I agree with response 1. I used to worry about that myself until I read that the polarity for the power on and reset switches doesn't matter(at least for an ATX compliant case). If the OP can back up the claim that the polarity destroyed the psu or Mboard, I would be interested to see that.

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#3
May 31, 2009 at 20:39:43
I don't know where you're getting your info from but it does NOT matter how you connect the power & reset switches. The case speaker doesn't matter either. But it DOES matter for the LED's. If you're blowing power supplies or fuses, you're doing something else wrong. Are you buying cheap no-name PSUs for under $20?

http://www.computing.net/answers/ha...

http://www.computing.net/answers/ha...

EDIT: wow, 3 answers, all saying basically the same thing, just a few minutes apart. Take that OP!


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Related Solutions

#4
May 31, 2009 at 20:50:28
Did your problem with the blown fuses have to do with a front panel having a small circuit board with all the motherboard connections coming from it? If so, then maybe polarity could be a factor. I doubt it though. In the dozens if not hundreds of times I've connected those wires I've always done it randomly and have never blown a power supply.

The power and reset switches on the front panel are momentary pushbutton SPST switches. The wire goes from the motherboard pin through the switch and back to the second motherboard pin. There is no polarity--the switch acts as a momentary short between the two pins.

So unless you have some configuration I've never run across those fuses popped for reasons other than the power and reset connection polarity.

Look at it this way, If you are right we'd be inundated with threads complaining about dead power supplies after motherboard removal or replacement.

Edit Four responses. I took a little longer googling because I'm always afraid of looking like an idiot if it's something new I haven't heard of.


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#5
June 2, 2009 at 17:29:39
Well I'm not going to argue about because I know I'm right about it as I write this email from the very computer that had the problem. I was on a friend computer with my original post.

Just so you know, I got my experience from hands on experience just like everything else I know. Nobody told me I learned through putting multiple parts in the trash and making note of each change as I made them. So I know what I"m saying. the wrong polarity with the LED won't do anything but prevent the LED from lighting up.

From my basic understanding on electrical engineering from a few of my then college buddies as well as an ex-girlfriend father who is an electrician by trade, polarity does matter with momentary devices like the power button.. The initial current that pulses through the pins on pushing the power button is slightly higher than it is rated.
The reason being is that because the duration of the charge is so short that more current is needed to compensate for the shorten duration. In fact that applies to many things in life, from work, to cars, to exercising, etc.

For me i try to avoid misleading statements like it don't matter just to be safe then sorry. I mean it might not apply to all boards and cases but carrying on in cautious matter as if it does saves headaches and money.

BTW I've only bought one complete computer from a store and that was back in 1999 and have hand built every single one since then. I've had blown fuses before but only after/during a thunderstorm. This is a first that a fuse has blown due to improper wiring of the front panel connectors. I find it hard to believe that an improper connection of an LED would short a power supply fuse but the polarity of the power switch won't? To me, that is like saying putting wrong polarity headers on your car battery won't mess up your car but wiring the headlights wrong will If anything the LED would either not light or blowout completely.

Oh almost forgot I have a little dated Abit VT7 motherboard and you can check the manual here < http://www.abit.com.tw/page/en/moth... > They put the pdf in a zip file but when you open it up goto page 30. While I admit this board may be in the minority about the switches polarity actually mattering but still it is something that one should be more careful about uttering.

Also it seems that black and/or white color wiring are both negatively polarized and in most cases all others are positive in a two wire configuration.


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#6
June 2, 2009 at 17:50:33
Boy, guess I should have read page 30 before building 4 of these things with 2.53Ghz Northwood B's.

I used a pocket screwdriver to start 'em up on the bench.

I suppose "could cause system malfunction" might also mean "could not cause system malfunction"; 'cause it sure didn't.

Far as I know, those workstations are still doing their thing.

Skip


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#7
June 2, 2009 at 19:55:13
I think that you may have misinterpreted "But it DOES matter for the LED's." in response 3. The links jam provided do not suggest anywhere(unless I missed something) that "an improper connection of an LED would short a power supply fuse". It just means the lights will not work.

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#8
June 2, 2009 at 20:07:58
self

I would check the case wiring on your case for shorting out somewhere on the steel where it is routed from the switch to the board. I advise this because that is the ONLY possible way the power and reset switches could cause a problem.

You could use white wires on both ends of those switches and it wouldn't matter. If you thought it thorough you would see that there is no way it can matter.

The switch is totally isolated from any system grounding in the case or on the board. The front case cover is all plastic and no part of the switches in question are in contact with any ground, ever. That is unless you have damaged the coating on one of them and it is grounded.

When you push the power switch all that is happening is current flows from the positive to the negative through a loop of wire with a momentary contact in the middle. The current will flow in the same direction no matter what color the leads are.

I will tell you what case wiring DOES matter. USB headers and Firewire headers. Connecting those items by crossing the polarity and nothing will happen until you connect a device to the port. Then you will damage something.


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#9
June 2, 2009 at 20:21:00
I just checked page 30. No polarity is indicated in the diagram for the power and reset switches as it is for the LEDs. And where it says 'wrong connection of the switches' there's no indication it's talking about polarity. I take it to mean 'make sure you connect to the right pins'. You don't, for example, want the switch wire headers connected to the LED pins.

(Oh, and the polarity indication for the speaker connection in that diagram can be ignored unless the speakers have a crossover circuit. Those employ capacitors, most of which are polarity sensitive.)

And you're ignoring the physical assembly of the switches themselves. Yes, there's a polarity with the power and reset pins, otherwise there would be no current flow and they would be useless. But the switch assembly is a direct short--a wire goes from one pin to one side of the switch and another wire connects the other side of the switch to the second pin. Pushing the switch in just connects those 2 wires. Current flows and good things happen.

You don't believe me? Disassemble a switch and look at the parts. Where are the electrical components that make that switch anything but a direct short?


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#10
June 2, 2009 at 20:56:51
I agree with everyone contributing to this thread. I really like SkipCox's answer. I've been working in computers for 10 years and I can tell you with complete certainty that it does not matter how you connect the power and reset switches to the motherboard. When I was first learning this stuff, I even connected a switch to the motherboard, then reversed it and the motherboard powered on with the switch connected either way. If what you're saying is true, then why is it possible to touch a screwdriver to the power button pins simultaneously and the system will power on? How would the polarity matter in that situation?

WinSimple Software
CompTIA A+ Certified


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#11
June 2, 2009 at 22:12:06
Don't let the OP's argument confuse anything folks. Like y'all said, it's simply a NO switch. To oversimplify, ya push the switch and it closes momentarily connecting pin 14, I think, to ground. The power good signal is no more than a feedback of a stable active +5vdc line (plugging into a working drive of some sort will make that line stable and active).

The psu is plugged into the wall, the psu wiring is plugged into the motherboard and drives, a simple circuit says power is good and presto...machine turns on.

It's that simple...no magic. That part of the power equation only consists of a switch, couple resistors, npn transistor, a diode, and 6 or 8 wire connections.

In the electricians world, he might wire a heavy duty relay into power and load lines to a crapload of 1000w light bulbs & control the whole mess with a 29¢ light switch connected with a 18gu. wire.

The front panel switches or my pocket screwdriver is the 29¢ light switch. The small bit of circuitry I glossed over above is the relay and the pc is the crapload of bulbs.

So, the problem does lie elsewhere. Cool you guys could all see thru the smoke (pun intended).

Skip


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#12
June 2, 2009 at 22:53:33
> Also it seems that black and/or white color wiring are both negatively
> polarized and in most cases all others are positive in a two
> wire configuration.

Your reason is also why Monster Cable can sell $7 speaker wire for $70 because their wire also has polarity.

Your knowledge comes from observation without the other "always required" underlying theory and education. I also know a physicist. Therefore I completely understand Einstein's Theory of Relativity? That was your reasoning.

Switches have no polarity as others have said. I will add another perspective - some engineering knowledge. We routinely short digital inputs or outputs and cause no damage to digital semiconductors. A technique to analyze failures and locate defects: short or power digital circuits in violation of what the drivers were trying to output - intentionally create change - and never damage digital electronics.

Your switches are connected to the same devices. Short them out or short them to a 5 volt supply and not cause damage. Or you could do what the switch does between two points - connect a wire between those two points - and not damage anything.

This post only confirms what others have said using EE knowledge. I have serious doubts about your 'engineering' source. Either they have no engineering knowledge, or (more likely) you did not grasp what they said.

Nothing about those switches can harm semiconductors. More likely: you did not use a static protection wrist strap. Therefore zapped semiconductors with destructive 10,000 volts - and did not realize it.

Meanwhile, reverse voltage on an LED can harm the LED. LED may be powered by 5 volts. But the same LED is only good for a reverse voltage of maybe less than 3.75. That damaged LED may still light. But overstress causes failure at a later date. Possible? Yes. Likely? No. But once I add knowledge you did not have, suddenly your "reverse connected LED" observation was a classic 'junk science' conclusion.

Your conclusion was based only in observation without the benefit of basic electrical knowledge. Once that engineering knowledge was added, then your conclusion completely changes.

Junk science is a conclusion only from observation - without first learning the underlying electrical principles. Junk science is also why Monster Cable sells wires (like your switches) with polarity for a massive 10 times higher price.


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#13
June 2, 2009 at 23:43:16
The Einstein analogy immediately reminded me of an electrical inspection in San Francisco I failed about 12 years ago. The inspector was an EE with a Phd but did not understand the concept of intrinsically safe.

"You can't run 900' of 22awg wire to that equipment! You are Red Tagged!"

We lost 5 days on that job and flew an engineer from CT to CA to explain the concept to his grudging satisfaction.

Somewhere during his career, he'd missed some of that underlying theory and education. We probably paid more for that little bit of education than he spent on his EE degree and doctorate.

"because their wire also has polarity."

And all this time I thought speaker wires just had "this end" and "that end".

Skip


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#14
June 4, 2009 at 09:53:34
Response #9

"I just checked page 30. No polarity is indicated in the diagram for the power and reset switches as it is for the LEDs. And where it says 'wrong connection of the switches' there's no indication it's talking about polarity. I take it to mean 'make sure you connect to the right pins'. You don't, for example, want the switch wire headers connected to the LED pins."

Well first of all, thank you for at least trying to see it from my perspective and actually reading what I read first before commenting. The wiring from the case was marked clearly for the led and switches so getting those wrong were impossible for me. You are also right about there being no polarity for the switches which i did take it to mean it didn't matter for those and acted accordingly. but when it came to LEDs I was unsure since it been years since i touched these wires and forgot. I noticed that all the wires had white wire in common and figured that was the ground/negative wire and connected accordingly. The speaker wire over the years had gotten ripped off. so i only had the two switches, hdd and power leds to worry about. when i reconnected the 20 pin power supply cable and powered up, that is when the original power supply fuse lit up like the fourth of july. and i came to the conclusion that those switches might have mattered after all. I looked up "case wiring" and "polarity" as well as "color coded" to find out which is which and CONFIRMED the leds were connected correctly.
Since there was only two headers for the switches I took it to mean polarity of each switch with its corresponding headers, though I found it baffling that no polarity was mentioned in the manual.

"And you're ignoring the physical assembly of the switches themselves. Yes, there's a polarity with the power and reset pins, otherwise there would be no current flow and they would be useless. But the switch assembly is a direct short--a wire goes from one pin to one side of the switch and another wire connects the other side of the switch to the second pin. Pushing the switch in just connects those 2 wires. Current flows and good things happen."

Well I can't say I'm ignoring the assembly of the switch because I can't actually see it unless I bother to remove the plastic casing from the front of the case which I prefer not to do.

You don't believe me? Disassemble a switch and look at the parts. Where are the electrical components that make that switch anything but a direct short?

Well because of the previous statement I made I won't debate you. I'm an "If it not broke don't fix it" type of guy so I'll assume you're right.


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#15
June 4, 2009 at 10:17:59
I'm not interested in the theory behind everything because for me the theory only explains the why behind things working which is not the intended purpose of this thread. I don't always need to konw why it works just the what I need to make it work. Now it is possible that manufacturer of my motherboard just failed to note the polarity of the power and reset swtich headers. Often times I'm sure that person writing the manual isn't the person who designed the actual board. I only wanted to point out that the general rule of thumb that the power and reset switch headers are bidirectional or doesn't matter in reference to how the header is connected to the pins is not a one size fits all statement and needs to be re-worded accordingly. I rather treat it as if I does have a polarity and matters in the "better safe than sorry" theory of application.

I find some of the sarcastic and rather rather condescending comments saddening and pathetic.
While I never claimed to be an expert at any thing and never will claim so even if others hold me in that regard, Those who try to wow me with their certification and degrees are hilarious pounding their puny chest in pride that they know more than me. If anything you're only showing me your complacency to keep learning and it just a matter of time before you get showed up by somebody like me.

All I'm saying is that while you may know more than I the way you express that knowledge to those of lesser knowledge of the subject matter can be dangerous. It doesn't matter how much you actually know if you can't properly convey your theory and knowledge to the audience receiving it. Lucky for me I'm resourceful enough to do my own research if something doesn't sound quite right to me in case somebody just explained it to me incorrectly or I misunderstood what was stated.


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#16
June 4, 2009 at 12:38:44
self

I took you at your word that you had some sort of short or mis-wiring.

That said, IF the conductors to and from the switch are NOT shorted to the case somehow it matters not which is which.

I suggested, and do so again, that you check the case to motherboard wiring for chaffing, which could cause the wiring to short to ground.

You didn't acknowledge that suggestion so I am assuming you either didn't read it or discounted it as not plausible.

You do understand that if no part of a switch, momentary or otherwise, is not connected to ground in any way, that there can be no polarity on that switch?

One other plausible explanation is that the board was shorted to the case in an area that it shouldn't be. That can happen if a standoff is installed in the wrong place or a loose screw get behind the board. In those instances the polarity of the switch wiring would not have a bearing on shorting out the board other than the fact that you have started the flow of current to the board by making that switch.


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#17
June 4, 2009 at 13:16:49
selfreliant

I'm not trying to be rude here, so please don't misunderstand me. But I cannot make any sense out of what you're saying.

"Now it is possible that manufacturer of my motherboard just failed to note the polarity of the power and reset swtich headers."

Again, I'm not trying to be rude, but that is not possible because the polarity of a switch does not matter. If it doesn't matter, why note the polarity of it?

"I find some of the sarcastic and rather rather condescending comments saddening and pathetic."

I don't know who's being sarcastic and condescending. We're all trying to be as nice as we can. I hope you don't think that we're being sarcastic because we don't agree with you.

"when i reconnected the 20 pin power supply cable and powered up, that is when the original power supply fuse lit up like the fourth of july."

What do you mean by power supply fuse? This doesn't make any sense to me.

How do you know that it's the power switch that's the problem? What substantial proof do you have to back that up? Again, I'm not trying to be rude.

WinSimple Software
CompTIA A+ Certified


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#18
June 4, 2009 at 13:27:36
selfreliant: I don't know much about wires and polarity and so on-that's why I stated earlier that I was concrned about the same thing you are-until i read otherwise. I have learned from reading others, including those who post on this forum, about wires and polarity, etc. I was ceratinly willing to read your argument that the the power and reset switch connectors were polarized incorrectly and that that caused your problem. I would like to pint out, however, that your original post seemed to be blaming your problems, in part, on the advice you read in this forum about the power and reset switch connectors.


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#19
June 4, 2009 at 16:53:13
"however, that your original post seemed to be blaming your problems, in part, on the advice you read in this forum about the power and reset switch connectors."

I got the same impression.

WinSimple Software
CompTIA A+ Certified


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#20
June 4, 2009 at 20:47:21
I guess it's logical to assume the power switch polarity may be a factor if you hit the power button and a fuse pops. But hitting that switch causes power to flow everywhere. We're saying that in the process of replacing/repairing the PSU, probably pulling the motherboard to take a look at it and whatever else you may have done you inadvertently corrected the problem. A short can be hard to track down especially if each test destroys some hardware if the short is still there.

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#21
June 8, 2009 at 23:45:07
OP - I must ask, in all sincerity, with no offense intended...

Why approach this in this manner?

The entire thread you've been (appearing to be) suggesting that everyone who's ever said "it doesn't matter which way the pins go for the buttons" is wrong, when it is an industry accepted fact that it makes no difference. In addition to that, it is common sense to someone who truly understands electricity and how those concepts relate to computers, specifically panel connectors.

I've never read a motherboard manual which suggested switches had polarity. In fact, I have (or previously had) at least one manual which explicitly states switches do not have polarity. I think it's one of my 486 boards.

Switch polarity is relevant in your house wiring - more specifically, what side of the load the switch is placed on. In computers, a momentary button switch has no polarity.

Another approach: do jumpers have polarity?


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#22
June 9, 2009 at 00:01:33
"Another approach: do jumpers have polarity?"

Well said.

WinSimple Software
CompTIA A+ Certified


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#23
June 9, 2009 at 10:36:30
Thanks...my original line was going to be something about how I routinely use, like SkipCox said, a pocket screwdriver...but then I remembered how I'd once used a jumper and it all fit together nicely in my head after that.

To ensure complete clarity exists here - since someone googling the motherboard model might find this and actually believe it:

The manual says to "Please pay attention to connect these headers. A wrong orientation will only cause the LED not lighting, but a wrong connection of the switches could cause system malfunction."

Wrong orientation /= wrong connection, in this case

Wrong orientation refers to, in this case, the two pins of the LED being inserted backwards.

Wrong connection refers to, in this case, placing the switches on the incorrect pins entirely, for example shorting an LED's voltage and ground pins. The effects of doing that will range from nothing, to arcs, to possibly trashing the motherboard...it largely depends on exactly how much current is being sent to those pins.


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#24
June 9, 2009 at 10:41:11
Hopeless?

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#25
June 9, 2009 at 16:01:05
"...I learned through putting multiple parts in the trash..."

I think we learned all we need to know from this post....


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