ESD strap grounding location

Question

I'm familiar with standard ESD control procedures (such as a grounding strap and/or mat) while working inside of a desktop PC. The general guidance for a standard ESD strap is to connect the strap to either an unpainted part of the system unit chassis, or to a central ground point (e.g. a specialized connector that connects the strap to the ground prong of a properly-wired AC outlet).

I'm wondering if in the case that these two options are unavailable whether it is as effective to connect an ESD strap clip to the ground prong of the desktop power supply (see attached photo).

Thanks.

Answer 1

The ATX power supply earth pin you have circled is directly connected to the metal chassis of the power supply, which in turn is also directly connected to PC metal chassis.

So yes, connecting the clip to that pin is completely electrically equivalent of connecting the clip to unpainted PC chassis. There may be other downsides though, it may not stay clipped to the pin and it is on the far side of the area you are working. Surely there must be a better place to clip than the inlet earth pin, and you don't want to make extra scratches or grooves with the clip to the earth pin either, so that sharp edges don't wear out the mains cord contacts.

Answer 2

For safety and function reasons I would not connect myself to the earth prong or metal chassis. It’s much better to pull a wire or even better a strap to a metal pipe or spike which goes deep into the ground. You don’t want any stray current from your mains network go into your electronics or even your body.

AARL has great material about grounding: http://www.arrl.org/grounding

What you need is what the AARL calls an RF ground, not a safety ground.

I have pulled a thick copper strand (not a solid wire!) to the metal water pipe where it enters the house. Then on my workbench it is connected to a copper tube from which I can then ground all my equipment.

Answer 3

If you have ever wired a light fixture or outlet, the installation manual will tell you to connect the green wire to the corresponding green or bare copper wire in your house. The manual also tells you to make sure the green house wire is earth grounded. If the wire is not grounded, you have to run a wire to something that is, such as a copper pipe or stake that enters the earth.

Thus, as long as your house is earth grounded, the middle pin in any outlet is earth grounded as well (so long as the electrician did their job). If not, then you will have to deal with the problem that [crasic] mentioned.

You should be able to connect the ESD clip to the middle ground pin of an outlet, as long as you have double checked the grounding status of your house, and whether the outlets are wired correctly.