Static electricity problem

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-Lone_Wolf-

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
 
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- said:
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
Click to expand...
John, it might help us troubleshoot if you were to tell us the cat's
gender. Tx, s
 
-Lone_Wolf- said:
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.
Click to expand...

That's a fascinating problem.

What is this 'mat' made of?

What kind of wireless keyboard/mouse? RF or Infrared?

I tend to doubt the discharge is going through the computer itself because
static like that is a localized thing. The rubbing creates a charge
differential between the two objects that are rubbed together, not to
'ground'. Now since, I presume, both you and the cat are on the mat then
there is a charge transfer to it as well but that charge will want to move
between the mat, you, and the cat, not across the room to the PC.

Unless the cat is creating a charge in it's wanderings around the room,
rubbing on the PC so that it grabs some charge and then, later, you so that
you have a charge and thereby creating a potential between you and the PC
but that sure seems a stretch.

I'm more inclined to think the discharge through you is getting into the
keyboard you're touching and causing it to spit out some spurious signal
that the PC sees as a reboot, standby, or shutdown key stroke, or garbage
that confuses it.

Turn off the automatic restart in control panel/system/advanced/startup and
recovery options to see if the machine is locking up first, then auto
restarting on the error, or restating because it thinks it was commanded to.
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?
Click to expand...

Not likely. Even if the static were getting to the PC the case itself is
connected to earth ground through the power supply so the charge should
never venture 'inside'.
 
w_tom said:
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.
Click to expand...

Modern motherboards never have 'one ground connect' unless one goes through
gyrations to defeat the built-in grounding scheme.
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.
Click to expand...

Going to be a bitch getting his charge to fly through the air from his
*wireless keyboard* to the computer.

Not to mention that charge takes the path of least resistance and across
the room and back through floors and latex wall paint ain't it.
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.
Click to expand...

I'm still waiting for you to tell me where the 'single point earth' is in
aircraft.
 
-Lone_Wolf- said:
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
Click to expand...

Buy a humidifier. We have a whole house humidifier that connects to
the main air duct that comes off the furnace. Now when we shuffle our
shoes across the the floor we no longer get shocked when we touch a
doorknob. There are other more health related benefits too. Even if
you don't have a forced air heating system a stand alone humidifier
will help a lot.
 
Buy a humidifier. We have a whole house humidifier that connects to
the main air duct that comes off the furnace. Now when we shuffle our
shoes across the the floor we no longer get shocked when we touch a
doorknob. There are other more health related benefits too. Even if
you don't have a forced air heating system a stand alone humidifier
will help a lot.
Click to expand...

This might be an option. Thanks for the suggestion!
 
David Maynard said:
That's a fascinating problem.

What is this 'mat' made of?
Click to expand...

Its one of those typical Rubbermaid type chair mats.
What kind of wireless keyboard/mouse? RF or Infrared?
RF


I tend to doubt the discharge is going through the computer itself because
static like that is a localized thing. The rubbing creates a charge
differential between the two objects that are rubbed together, not to
'ground'. Now since, I presume, both you and the cat are on the mat then
there is a charge transfer to it as well but that charge will want to move
between the mat, you, and the cat, not across the room to the PC.
Click to expand...

It must be the fact that as she is rubbing my pant leg she is between me and
the PC case so she may tend to occasionally touch it as well. I know for a
fact I am well away from the box and often leaning back away from the
keyboard.
Unless the cat is creating a charge in it's wanderings around the room,
rubbing on the PC so that it grabs some charge and then, later, you so
that you have a charge and thereby creating a potential between you and
the PC but that sure seems a stretch.

I'm more inclined to think the discharge through you is getting into the
keyboard you're touching and causing it to spit out some spurious signal
that the PC sees as a reboot, standby, or shutdown key stroke, or garbage
that confuses it.
Click to expand...

Thing is its an instant off similar to an overheated CPU, not a blue Windows
is shutting down screen first.
Turn off the automatic restart in control panel/system/advanced/startup
and recovery options to see if the machine is locking up first, then auto
restarting on the error, or restating because it thinks it was commanded
to.


Not likely. Even if the static were getting to the PC the case itself is
connected to earth ground through the power supply so the charge should
never venture 'inside'.
Click to expand...

I wonder if her long hair once charged is touching the ground on the front
USB port?
 
Shinnokxz said:
Shave the cat.
Click to expand...
If it's a female, you only have to shave one foot--rear or front, where
it contacts the floor when she walks. If it's a male, you would also have
to shave the last inch or so of his tail. (Naturally, if he is a Manx, this
tail-procedure would not be required.)
FWIW, if the cat is of calico color, just shave that one foot without
checking its sex: they are all female! Luck to you, s
 
w_tom said:
You have the right idea. But static electricity is not
seeking earth ground. Earthing is not part of a static
electric discharge circuit.
Click to expand...

But, would earthing possibly help nutrilize the static charge?
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.
Click to expand...

As mentioned its a wireless keyboard.
 
-Lone_Wolf- said:
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
Click to expand...
It has been my experience that many times static problems are compounded by
defective or missing grounds.

As a tech I carry around one of those three-prong outlet testers. I have
found that it is to my benefit to test where the equipment is plugged in
prior to doing any other testing. I have found outlets, outlet strips, and
extension cords with numerous problems.

Many were wired incorrectly from the beginning or have broken down from use.
I have lost count of the number of outlet strips and extenders that were
wired wrong at the factory. As I explain to the customers, just because the
power comes on does not mean the outlet or extender is wired correctly or is
still safe to use.

As for static, yes there are static floor mats that can be grounded but they
tend to use a different composition in the plastic, which include things
like graphic or even metallic fibers. The cheaper plastic mats usually sold
for home use are not made of the anti-static conductive plastic and adding a
ground wire to them usually does little good, but then again it can't hurt
either.

You might do better purchasing one of the cans of anti-static sprays put out
by the better manufacturers, like 3M.

I know of one cleaning company that adds a little fabric softener to the
solution they use when they clean the carpets as a means of reducing static
in the offices they support.

I even ran into one telephone computer room that installed wall to wall
industrial grade anti-static carpet. Of the 5 or 7 bundles of fibers in
each loop of the carpet, two of them were actually make up of very small
stainless steel wires rather than the standard nylon or plastic. Along the
perimeter of the room the strips that held down the carpet were metal and
had ground wires attached to them leading to a central ground.

Oh well, back to the ground, er I mean grind...
 
-Lone_Wolf- said:
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.
Click to expand...

Use fabric softener in the rinse cycle and anti-static sheets in the
dryer when cleaning the cat. Or shave the cat.

It's not the computer case since even the slightest amount of static is
immediately drained off through the power cord and into the ground
connection of the AC outlet. A possible exception is when the
computer case is made of plastic and no ground wires were run between
the motherboard and drives to the power supply case, but this applies
only to a few power supplies build with AC and DC grounds not connected
to one another.

Static build-up is caused by electrical insulation being too good, and
the plastic mat is causing most of your problem and adding a ground
connection to it won't help because its material just doesn't conduct
enough. Try getting rid of it or buying an expensive mat made of
anti-static plastic or rubber. If you have to prop up the computer
case, put it on ceramic tile a piece of wood. A second anti-static mat
for under the keyboard, mouse, and monitor should also help, especially
if it's connected to the computer case. Also consider changing the
type of clothing you wear, especially the footwear: leather soled
shoes build up much less static than rubber soled ones do, and ordinary
socks are never good for static, although cotton generates the least
voltage.

Washing your clothes with fabric softener and spraying diluted fabric
softener on the carpet and chair every week can help.
 
-Lone_Wolf- said:
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
Click to expand...


Simple solution.

Kill the cat. :-)
 
Earthing has nothing to do with static electricity
protection. To have electricity, a complete circuit must
exist. Without a complete circuit, then no discharge. That
means bottom of shoes must somehow connect to upper body (ie
fingertips). If that discharge circuit is via electronics,
then electronics are damaged or overstressed (fail one day or
months later). If upper body is connected to shoes via wrist
strap (with very larger resistor in that wrist strap to
protect human), then circuit path not destructively through
electronics.

Yes, earth ground could be part of that path. But before
that discharge gets to earth ground, other paths already have
achieved bottom of shoes. Minimize static damage by
connecting upper body to bottom of shoes - make a complete
electrical circuit to discharge static buildup.

Wireless means keyboard probably is path of static discharge
into computer. (This assumes motherboard computer - not
keyboard computer - is crashing.) Another path could be wrist
contacting pad, then into computer via pad. But again, every
post can only speculate without detailed list of possible
electrical paths from upper body to bottom of shoes.

Somehow body discharge is forming a complete circuit through
computer that has crashed. Meanwhile, humidifier would
protect electronics (as well as reduce heating bill). If
humidifier is not possible, then ring out one or two bath
towels and leave them to air dry. Humidity being important
for reasons beyond computer protection.
 
Use static electricity to identify defective installations.
Static electricity being an excellent diagnostic tool. Place
a computer atop a non-conductive desktop. (Glass because most
tabletops are too conductive). Plug computer into grounded
outlet. Static discharge to every corner of computer. If any
static discharge causes software crashes, then computer is
internally defective.

When a static discharge to is the far corner (so that
electricity must cross CPU to get to AC power cord ground),
then defectively assembled computer crashes. In a latest
case, static discharge at the far end of case went partially
through motherboard ground plane. Why this causes a computer
crash is described in an earlier post and better described in
National Semiconductor application notes about IC grounds and
PC board ground planes - beyond the scope of this thread.

Missing AC electric ground only means static discharge was
finding another path to bottom of shoes. Question remains:
where is that other 'reason for failure' path located. Static
electric discharge should never find a path to bottom of shoes
via electronic motherboard ground plane - which is but one
reason for a computer crash due to static electric discharge.
Static electricity causing a computer crash is how to
diagnosis a defective computer assembly.

Every properly constructed computer should suffer direct
static electric discharges to any external surface - without
computer adversely affected.

If I don't have my meter, then how do I test wall receptacle
ground? I static electric discharge into that receptacle
ground and 'measure' the "pain". A discharge not sufficiently
painful implies a 'not grounded' wall receptacle or switch.
Again, static electricity is a good diagnostic tool for wiring
defects such as missing wall receptacle or wall switch safety
grounds. Static electricity being a diagnostic tool.

Damn engineer. Always asking why. Never satisfied with
solutions that only cure symptoms - such as killing the cat.
Only Rush Limbaugh types would like that solution - the
problem be damned.
 
Slightly said:
Its one of those typical Rubbermaid type chair mats.




It must be the fact that as she is rubbing my pant leg she is between me and
the PC case so she may tend to occasionally touch it as well. I know for a
fact I am well away from the box and often leaning back away from the
keyboard.
Click to expand...

I see. You're closer to the machine than I thought might be the case.
Thing is its an instant off similar to an overheated CPU, not a blue Windows
is shutting down screen first.




I wonder if her long hair once charged is touching the ground on the front
USB port?
Click to expand...

Front ports could be a problem if she's touching them as there isn't just
the 'ground' there; you've got signal lines too and that might cause a
problem if a static discharge goes though them because, as I mentioned, it
isn't seeking ground so the PC grounding is probably not doing much.

Normal input protection schemes should still work, though, because they
should shunt the charge to case, which would then go back to the cat,
floor, or you, but maybe their input protection isn't up to snuff somewhere.

It's obviously not practical to attempt a computer redesign so your best
bet at this stage is to prevent the static build-up to begin with.
 
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