Eric Hidle on Wed, 4 Dec 2002 05:30:06 -0500


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Re: [PLUG] Laptop reboots -- Comcast or static or age?


Just some FYI on grounding

The standard model for human ESD is a 6kV charge with a capacitcance of
something like 22pF, which is probably insufficient to electrocute you.
Adding a resistor to the loop is probably a good idea to protect yourself
against an improperly wired outlet, but as long as you ground yourself to
the same outlet that your computer is plugged into, this isn't so much an
issue. You should always be at the same ground potential as your computer
anyway.

If you use a grounding strap, there is probably enough resistance in the
skin-to-strap junction to take care of it. Also, since there is a large
contact surface area, the surface current density through your skin would be
very low. The only time there would be appreciable current is when you
attached the grounding strap to the ground. Otherwise, once you're
connected, charge bleeds off of you as it builds up.

One way I've heard of to reduce the amount of static in a carpeted room is
to underlay the carpet with a conductive screen that is attached to ground.
This can bleed charge out of the carpet and prevent it from building up on
you.

A much cheaper way is to buy a humidifier :)

Eric



----- Original Message -----
From: <eric@lucii.org>
To: <plug@lists.phillylinux.org>
Sent: Tuesday, December 03, 2002 10:10 PM
Subject: Re: [PLUG] Laptop reboots -- Comcast or static or age?


> For static discharge, a 1M resistor (1 MegOhm) is
> sufficient.  This will prevent you from conducting a fatal
> (or even painful) current should you come in contact with
> something that is of lower voltage and lower impedance (IE:
> 110V AC) while grounded by the strap.
>
> You would be amazed at the number of mis-wired electrical
> circuits and devices there are out there.  Some small
> televisions, for example, have one side of the AC line tied
> to the "frame".  It's supposed to be the neutral but if
> somebody screws up the wiring in the electrical panel or the
> outlet box you can end up in lots of trouble.
>
> Eric
>
>
> On Tue, Dec 03, 2002 at 07:06:50PM -0500, Paul wrote:
> > >
> > >
> > >Purchase a grounding strap.
> > > -or-
> > >`Build' a grounding strap by screwing one end of a piece of wire to a
known
> > >ground (screw-plate of a properly wired outlet) and the other end
stripped
> > >and wrapped around your wrist.  This bleeds off all static to ground.
> > >
> > Um, it might be a good precaution to add a resistor.  I'm not sure of
> > the ideal value for the resistor, but the resistor will limit the amount
> > of current that can flow through the circuit.  That's important because
> > the circuit includes your body!
> >
> > I did an experiment in which I tied a copper wire around my ankle and
> > let the other end drag on the carpet.  It worked.  With the wire
> > everything was OK.  Without the wire static charge would build up to the
> > point that I would get an audible zap and a light show whenever I
> > touched something.
> >
> > The idea is to balance the difference in charge between your self and
> > the object (in a controlled manner).  It is not necessary to use an
> > electrical system's earth ground.  For example, when passing a piece of
> > RAM to another person touch the person's hand with your own hand before
> > handing off the RAM.  In the same way you can balance the charge between
> > your self and a PC by touching the frame first.
>
>
> --
> ------------------------------------------------------------------------
> #   Eric Allan Lucas
> ------------------------------------------------------------------------
> Everyone wants to live at the expense of the State.  They forget that
> the State lives at the expense of everyone.
>   -- Frederic Bastiat (1801 - 1850) French statesman and author.
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