grounds and electrostatic dissipation

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Cirtcele

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Location
CA, Bay area
This question is regarding personal computers and the necesity for the ground. I have been told that it is a necesity for the dissipation of electrostatic charges wich may build up from the spinning hard drive and the fan motor. I understand the standard need for a ground (safety), but the idea of electrostatic dissipation is new to me.

Can anyone shed some light on this topic for me? If it is not necessary for the ESD, why do the manufacturers print in their material "computer will not function properly without a proper ground connection."???

Thanks
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I have been told that it is a necesity for the dissipation of electrostatic charges wich may build up from the spinning hard drive and the fan motor.
If that is true, then how do laptops work?
Don
 

NoVA Comms Power

Senior Member
Location
Alexandria, VA
PC grounding requirements mostly have to do w/ communications (and few computers today aren't connected).

Having a good ground reference is critical in any communications system.

Even a small difference in voltage can create an undesireable current on a comms conductor.

Laptops are for the most part immune to this as they generally use external power supplies, and only low-voltage DC ever gets to the box itself. (although most business-class laptops still have 3-prong grounded plugs)

Desktop PCs on the other hand have a power supply w/ a transformer which can induce small voltages onto the chassis. (and don't forget that many of these PC power supplies are assembled in 3rd-world countries w/ highly variable QA standards)

If any chassis voltage is "bled-off" via a good ground connection, there's generally no problem, but w/o a ground, that path might be through your comm line causing problems.
 
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don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
Having a good ground reference is critical in any communications system.

Even a small difference in voltage can create an undesireable current on a comms conductor.
Only if the communications conductor is referenced to ground. Most currenty used computer communications conductors are not referenced to ground for this very reason.
Don
 

RayS

Senior Member
Location
Cincinnati
The drive platter spining cannot generate external charge- it is a sealed system in a metal case.

The only fans I've seen that needed grounding were hi-velocity units in explosive environments- can't see a computer fan being an issue.

Grounding does, however prevent static "glitches" and provides shielding.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
grounding a pc

grounding a pc

I think it is almost humorous how many people think they are experts in this field but are just completely off base.

Virtually all PCs use isolated communications links. Grounding is just not an issue.

Who knows why a manufacturer would say the ground is necessary for proper functioning. If that was true, no battery powered device device would work. I can't recall ever seeing this statement in a PC manual, but I would guess if there is such a statement it is generic boilerplate inserted by some tech writer with little or no clue.
 

Cirtcele

Member
Location
CA, Bay area
Thanks for all of the input everyone.

Rays
Grounding does, however prevent static "glitches" and provides shielding.

This is what I have heard from others and is exactly what I am trying to get to the bottom of.

Based on what I have read and heard, there simply are not "glitches" that are caused by static electricity. Can you elaborate on what these glitches are?

I tend to think the cya approach to of manufacturers is the answer for why they are printing it in their literature.

thanks again.
 

Cirtcele

Member
Location
CA, Bay area
GFCI adequate

GFCI adequate

petersonra said:
Virtually all PCs use isolated communications links. Grounding is just not an issue.

Who knows why a manufacturer would say the ground is necessary for proper functioning. If that was true, no battery powered device device would work. I can't recall ever seeing this statement in a PC manual, but I would guess if there is such a statement it is generic boilerplate inserted by some tech writer with little or no clue.


In an old home with nob and tube, would it then be adequate to use a gfci outlet on a circuit which will be powering a home computer? I have been recomending against this and suggesting that the recepticles need to be grounded. I know that the NEC calls for labeling on non grounded recepticles and that gfci is at this point an acceptable upgrade.

What are your thoughts on this?
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
Cirtcele said:
What are your thoughts on this?
Since most residential computer / monitor / periferals use power strips w/built in surge protectors, if no EGC exists, any line surge will be dumped onto equip grounding prongs, increasing chasis potential relative to nearby components or people.
 

charlie tuna

Senior Member
Location
Florida
every computer i have worked on uses the computer frame as a ground plate and they all recommend being fed by a dedicated three wire circuit. we all know that some amount of static electricity can cause major problems within the circuit board of electronic equipment. when grounded properly the frame will disipate any static charge that it might come across and maintain the surrounding housing of the computer at a zero referance plane. yes, it will run without a ground -- but have seen network problems caused by improperly grounded computers and also major problems caused by common neutral or multi-wired branch circuits---and again --- yes, the computer will operate but you will have more parts failures and data losses with improperly powered computers....
 

jtester

Senior Member
Location
Las Cruces N.M.
I live in a home with no branch circuit grounding, it was built in the 60's. I run my engineering business from my home, run computers all day long, and have had absolutely no problems with unusual failures, glitches, etc.

Trust me, a lack of grounding does not have to be an issue. You probably have more problems with bad grounding and networked equipment, but I've had no problems what so ever.

Jim T
 

peteo

Senior Member
Location
Los Angeles
Quite a diversity of answers. The OP questioned fans and spinning drives, and why this would be an ESD issue.

The basic idea is that moving air generates ESD. That is, anything from a forklift on rubber wheels to a person on a carpet to picking up a piece of paper can leave a difference in potential between the item and the 'ambient' or 'grounded' environment. Fans, of course, move air, and moving air also tends to lower the humidity. Some of the responses look to be from people who never walked up to a car in a parking lot in Palm Springs on one of those 110 days - better still, turn on the lights in an air conditioned, carpeted office in Phoenix or Yuma. Ouch! --- blue spark! Not much of an issue in a place (SF bay area) with reasonable humidity. A visible spark, by industry standards, means that there has been a potential difference of 2000 volts minimum between objects. A glitch probably refers to a smaller event which might not be noticed by ordinary means but affects communications or components, etc.

The effects of ESD damage on electronics (PCs) are quite obnoxious. They can burn up, lock up, work for a few months and then do something unexpected, or gradually start acting up to the point where nerves are frazzled and you end up throwing the whole thing out thinking there's something wrong with how they built it.
 

foqnc

Member
jtester said:
I live in a home with no branch circuit grounding, it was built in the 60's. I run my engineering business from my home, run computers all day long, and have had absolutely no problems with unusual failures, glitches, etc.

Trust me, a lack of grounding does not have to be an issue. You probably have more problems with bad grounding and networked equipment, but I've had no problems what so ever.

Jim T
Same here with my house having no branch circuit ground and no problems with the computer left on 24/7
 

RayS

Senior Member
Location
Cincinnati
Cirtcele said:
Rays
Grounding does, however prevent static "glitches" and provides shielding.

This is what I have heard from others and is exactly what I am trying to get to the bottom of.

Based on what I have read and heard, there simply are not "glitches" that are caused by static electricity. Can you elaborate on what these glitches are?

I think static can certainly cause glitches in electronics, even fry some sensitive circuits. Lots of digital circuitry now operates on 3.3v- the older standard was 5v. If this is the max signaling voltage, actual is lower (i'm thinking about 1.7v?) so even small induced voltages can cause errors (glitches).
 

BarryO

Senior Member
Location
Bend, OR
Occupation
Electrical engineer (retired)
Cirtcele said:
Based on what I have read and heard, there simply are not "glitches" that are caused by static electricity. Can you elaborate on what these glitches are?

I have alot of experience dealing with static-caused glitches in public safety communications dispatching systems. Static glitches can cause computer faults and resets. It's not the console computer components generating the static electricity: it's the people that do it. Worst-case seems to be a dispatcher shuffling their feet along the carpet on the way back from coffee break, headset plug extending and ready to plug in. I've seen this generate long (~1") sparks between the plug and jack just before they plug in. The console's computer operating system can go into outer space.

Mitigation isn't so much grounding, but proper transient-voltage suppression design in the components that get near human body parts.

And forget telling the Dispatchers' union rep. that the fancy plush carpet has to go. ;)
 
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