Re: Static electricity problem
- From: w_tom <w_tom1@xxxxxxxxxxx>
- Date: Wed, 07 Dec 2005 17:26:20 -0500
You have the right idea. But static electricity is not
seeking earth ground. Earthing is not part of a static
electric discharge circuit. Somehow your body discharge is
forming a complete circuit through computer. This is why
motherboards are often mounted on chassis plate with only one
ground interconnect. If the static current discharge was
using motherboard copper traces as part of its path (due to
multiple connections to chassis plate), then ICs on that
motherboard are seeing voltage differences across the board.
These tenths of volts difference between ground pins on ICs
cause software crashes.
Other paths can also exist. One might be through keyboard,
into computer, down safety ground wire, through latex wall
paint, into floor, and back to you. Another example of a
complete circuit.
You have the right idea. We want sufficient humidity and
wrist straps connected to chassis when ever anyone works on
electronics. BTW, same can even apply to a digital camera
when connected or disconnected via USB port. It is also why
we prefer cotton (or better is polyester cotton) instead of
nylon.
Insulating, absorbing, or blocking such transients (be it
static electricity or the one outside called lightning) is a
fool's errand. We start by making the transient not generated
AND make conductive paths to shunt (divert, discharge,
redirect) that transient on paths that are not destructive.
Sold are special conductive plastic mats for desktop and for
floor that are better electrical conductors specifically to
discharge static electricity. Even provided with connector
and wire to complete the discharge circuits.
This is but another example of why we want a single point
ground - be it to remove hum in a stereo, static electric
discharge to computer, or lightning strike to a building.
Ground loops through wrong things cause failures.
-Lone_Wolf- wrote:
> Recently (since the humidity has dropped around here), I have had
> a problem with my latest machine.
>
> Whenever my long haired cat rubs up against my legs my PC instantly powers
> off and reboots (even though I may be no where near the PC - note I use
> wireless keyboard and mouse). I am assuming its because the box is sitting
> on top of the plastic floor mat and the charge is running down my leg, into
> the mat, and then through the PC to the ground in the house wiring. So far
> it has not hurt anything and I have not lost any important work, but I do
> need to stop this from happening.
>
> Moving the box is out of the question due to space constraints but I could
> try to insulate it from the mat better. I have also considered riveting a
> grounding cable to the mat and running it directly to the ground line in the
> house wiring.
>
> Could I have missed something in my installation of the motherboard that is
> not correctly protecting the board?
>
> John
.
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