Motherboard grounding questions

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Re: Motherboard grounding questions

Postby Karlsweldt » Sat Oct 01, 2016 4:07 pm

The mount screws for a heat sink on a CPU would be at ground potential, but maybe not a true ground.. a low resistance path.
There would not be any induced or stray voltage from a sensor or the fan to the heat sink. If there is a PWM or thermal sensor, likely its black wire is restively connected to the metallic frame of the heat sink.. effectively grounding it.
There is no real issue with a 'ground loop' condition inside a computer case. It is more probable where mains wiring feed different devices, then the data cables connect between those devices. The PC case is the only connection to mains grounding, all other power leads are common to the PSU ground. Yes, the internal circuitry ground is connected to the mains grounding through the PSU.
PC speakers do not have a ground connection between the mains and the PC itself.. isolated. But a home hi-fi system may be grounded to the mains, and cables could present a 'ground loop' condition if connected to a PC. A faint AC hum is most commonly the clue that there is a potential problem.
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Re: Motherboard grounding questions

Postby LakaWaka » Sat Oct 01, 2016 4:22 pm

Karlsweldt wrote:The mount screws for a heat sink on a CPU would be at ground potential, but maybe not a true ground.. a low resistance path.
There would not be any induced or stray voltage from a sensor or the fan to the heat sink. If there is a PWM or thermal sensor, likely its black wire is restively connected to the metallic frame of the heat sink.. effectively grounding it.
There is no real issue with a 'ground loop' condition inside a computer case. It is more probable where mains wiring feed different devices, then the data cables connect between those devices. The PC case is the only connection to mains grounding, all other power leads are common to the PSU ground. Yes, the internal circuitry ground is connected to the mains grounding through the PSU.
PC speakers do not have a ground connection between the mains and the PC itself.. isolated. But a home hi-fi system may be grounded to the mains, and cables could present a 'ground loop' condition if connected to a PC. A faint AC hum is most commonly the clue that there is a potential problem.


Oh, so it's a good thing if there's a sensor wire then? I thought it was a bad thing... You mention that the issue is if the mains wiring feeds different devices.. Isn't the mains wire the 24-pin mobo connector? How would that feed other devices? I am looking to power an Arduino off of my PSU, so I figured I would ask to see if that would cause an issue, because maybe there is something I'm missing from all of this... How do you know what is grounded to what? Why would a hi-fi system be grounded to the mains? Interesting information though...

So essentially... I shouldn't worry about the HSF screws then? That's really the only thing I was worried about causing issues and causing big problems i.e., fire, or mobo damage... BUt maybe I'm thinking that would be too big of an issue? Not sure what happens if electricity were to go through the HSF screws, but I guess that's, again, the point of the grounding... to prevent that...
Hmmm... Maybe I was woried for nothing then :). Thanks a lot as always...
PS... I still need moderator approval... After 50 posts that's a big excessive... I believe you mentioned you were going to ask around about it. Any results? Thanks a lot.
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Re: Motherboard grounding questions

Postby Karlsweldt » Sun Oct 02, 2016 4:52 am

When referring to "mains" power, that is the primary power source from a wall outlet. All other power sources are 'secondary'. Yes, there are main power leads within equipment, but that is local to the device. Commonly referred to as a main bus.
The ATX power connector may be referred to as a 'main' connection, but it is local to the needs of the device only. Yes, you could power other devices from one PSU, as long as it has the capacity to power all devices within its rated limits.
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Re: Motherboard grounding questions

Postby LakaWaka » Sun Oct 09, 2016 12:31 pm

Karlsweldt wrote:When referring to "mains" power, that is the primary power source from a wall outlet. All other power sources are 'secondary'. Yes, there are main power leads within equipment, but that is local to the device. Commonly referred to as a main bus.
The ATX power connector may be referred to as a 'main' connection, but it is local to the needs of the device only. Yes, you could power other devices from one PSU, as long as it has the capacity to power all devices within its rated limits.

The power of mains in the palm of my hands..... So that's good that everything will ground out through the mains, and I would get shocked or cause my case to catch on fire or something by not placing something between the HSF screws and the case.
Now, I'm thinking about picking up one of those grounding mats to do with on from now on (since it seems like a good idea), but not sure where to connect the ground to? It seems that you can ground yourself by touching the case, but what about the power plug or something? Is there something special I should connect up to? Thanks.
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Re: Motherboard grounding questions

Postby Karlsweldt » Sun Oct 09, 2016 3:27 pm

Those ESD static suppression mats or "grounding" mats have a lead with a battery clip to connect to a known good ground, either a water pipe or an electrical outlet ground.
Highest voltage used in a PC is +12 volts. Very little shock hazard from that. But if you were to contact the +12 volts and -12 volts lead, you would feel a little bit of a shock. Inside the PSU is where the real danger lurks. The large primary capacitors store around 200 volts DC or higher. Some of the finned heat sinks may also be at that potential. Could be lethal if a shock path were across your heart!
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Re: Motherboard grounding questions

Postby LakaWaka » Thu Oct 13, 2016 7:18 am

Karlsweldt wrote:Those ESD static suppression mats or "grounding" mats have a lead with a battery clip to connect to a known good ground, either a water pipe or an electrical outlet ground.
Highest voltage used in a PC is +12 volts. Very little shock hazard from that. But if you were to contact the +12 volts and -12 volts lead, you would feel a little bit of a shock. Inside the PSU is where the real danger lurks. The large primary capacitors store around 200 volts DC or higher. Some of the finned heat sinks may also be at that potential. Could be lethal if a shock path were across your heart!


Thanks for the information, so I would just plug it into the ground prong on the outlet?
So there isn't really any danger, and from what you said all is good. I was just worried because I thought that the HSF screws would cause problems, but sicnce you mentioned they were potential ground, all should be well. Thank you.
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Re: Motherboard grounding questions

Postby Karlsweldt » Thu Oct 13, 2016 3:58 pm

The electric outlet ground port requires a specific size pin, or can expand the inner contacts and defeat the purpose. The standard diameter of the 3-prong plug is 4.8 mm. If the ESD static mat has that size pin, OK to push (GENTLY!) into the ground port. Best would be the metal case of a power strip, or the screw that holds outlet covers in place. The screws at top and bottom are longest, so a few small washers under the top screw would be an ideal ground point.
http://www.worldstandards.eu/electricit ... ockets/ab/
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Re: Motherboard grounding questions

Postby LakaWaka » Thu Oct 13, 2016 9:44 pm

Karlsweldt wrote:The electric outlet ground port requires a specific size pin, or can expand the inner contacts and defeat the purpose. The standard diameter of the 3-prong plug is 4.8 mm. If the ESD static mat has that size pin, OK to push (GENTLY!) into the ground port. Best would be the metal case of a power strip, or the screw that holds outlet covers in place. The screws at top and bottom are longest, so a few small washers under the top screw would be an ideal ground point.
http://www.worldstandards.eu/electricit ... ockets/ab/


Thanks.. hmm.... I'm not sure what the connector is, but figured it would be simple to attach, but maybe not? you said the metal casing of a strp would work, or the screw inm an outlet hmmm... I'm pretty sure I read about some connection on a surge protector at some point in the past, buyt again not really sure (will look at the mat). Are the mats something you would recommend? I know tons of people talk about static and it not being a "Big deal" and people saying they built on carpet, just touching a computer case to ground themselves every now and then, but this seems very risky, and I believe we spoke about these situations on page 1, and that we wont see microscopic static damage, and it might not show signs of damage right away, but will be an issue later on or something? IT just seems smart to protect yourself :).


EDIT: Hopefully this gets to you @Karlsweldt, but I wanted to ask if any opening in a computer case would be a passage for stray EMF/RF emissions? I noticed that besides the I/O shield for the motherboard, every single PCI card comes with their own protective bracket as well. Most computer cases will block off unused slots, but if you leave them open, are you at risk of EMF/RF emissions? Also, what about other openings? I'm assuming every single doesn't need to be protected? I am also assuming that the "I/O Shields" are just that, shields for I/O and just protecting emissions from entering the I/O possibly causing a charge that could take out the motherboard? I think we did actually discuss about fans introducing static into the case at some point in one of our discussions? But, I would assume that all case fans would be made of ESD safe plastics so that static could not build up and cause issues. Thanks for the help as always.
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Re: Motherboard grounding questions

Postby Karlsweldt » Mon Oct 24, 2016 2:32 pm

The shielding on a PC case does an effective job of containing most EMF and RFI unwanted signals. But the main power cord also should be shielded, as most thick round ones are. Should be a tag noting same. The same shielding does protect circuits inside the case from unwanted EMF and RFI signals. Reason too the PSU case is as such, to contain any undesirable RFI from interfering with the PC data circuits. DC fans and similar are also self-shielded. Not only is a PC a strong source of RFI, but also most printers.. mainly the PSU section, similar to a regular PSU. But may not be shielded! Commercial units are very well shielded.
Back when telephone modems were popular, there was a good chance of a lightning strike traveling several miles, and finding itself in your PC.. and doing severe damage. Yes, there is an isolation transformer in the modem, but not for high voltage.
Any PC case plastic is not inherently static inducing, unless the humidity is extremely low, and you rub it with a cloth such as wool or satin that would generate static electricity.
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Re: Motherboard grounding questions

Postby LakaWaka » Mon Oct 24, 2016 3:21 pm

Karlsweldt wrote:The shielding on a PC case does an effective job of containing most EMF and RFI unwanted signals. But the main power cord also should be shielded, as most thick round ones are. Should be a tag noting same. The same shielding does protect circuits inside the case from unwanted EMF and RFI signals. Reason too the PSU case is as such, to contain any undesirable RFI from interfering with the PC data circuits. DC fans and similar are also self-shielded. Not only is a PC a strong source of RFI, but also most printers.. mainly the PSU section, similar to a regular PSU. But may not be shielded! Commercial units are very well shielded.
Back when telephone modems were popular, there was a good chance of a lightning strike traveling several miles, and finding itself in your PC.. and doing severe damage. Yes, there is an isolation transformer in the modem, but not for high voltage.
Any PC case plastic is not inherently static inducing, unless the humidity is extremely low, and you rub it with a cloth such as wool or satin that would generate static electricity.


Yay my edit made it to you :).
All mains power cords I see are usually some sort of black/rubber type insulation. I do notice some tags on some wires. So, if I have unused ports, they should all be shielded then? The PSU I've seen vary a lot, but I guess that "Box," as well as that plastic shielding you were mentioning earlier, is what protects the computer from the emissions? I wonder if that old crappy PSU I had was the cause of some of the interference I was getting on my sound card, which DOES NOT exist now. Same case, same sound card, everything else is different now. So the case itself protects the computer from the outside, but also doesn't allow RFI to escape to the outside, since you mention it emits RFI as well? Does something absorb the RFI? The case itself?
Damn that's rough about modems...
Yeah, don't want to mess with the winter and computers...
By the way, I was helping a friend with his graphics card and I noticed all these pad like things, strips, cloth like stuff, as well as thermal paste. From what I have read the thermal paste is essentially harmless (just don't eat it)[not sure if GPU paste if any different than CPU paste but I would guess not?), but the pads seem different, and what is that white cloth stuff? What are your thoughts on the toxicity of this stuff? I probably should have warn some gloves up to that point, but didn't really think about it until now actually; however I don't think I touched any, except a little bit because it was on this backplate because of how he took off his card(just felt sticky when I touched). I assume those Nitrile gloves you mentioned in another post would also work well?
One last part to this is I couldn't find the last time we spoke about this, but you recommended iso alcohol to clean this stuff up, right? I believe you mentioned no rubbing alcohol (I read it contains something that leaves a residue, but also read different things, so it might be country based).
ALso, one last off topic thing. I was looking at doing a project and need a larger cap 1000uF+ (not sure voltage, but I think 5 or so) and found this https://www.adafruit.com/products/1589 was curious if you think this would be any good?
Thanks so much as always.
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