First: the discharge of electrostatic energy (from a human body)is
characterized by quiet large discharge currents (up to 8 Amps peak or more)
for a VERY short time (typically between 30 nanosec and 100 nanosec) with a
VERY fast rise time between a few hundret picoseconds and 1 nanosecond. This
will happen in case of a charged body (the voltage you can charge up is up
to 25 kiloVolts!) comes close enough to or touches another body, which has a
certain cpacity to ground or is connected to ground. Then you will see the
typical discharge spark. Expressed in terms of energy this is rather low,
but may cause some pain to our finger if the discharge appears there.
Because of the low energy only the microscopic structure of integrated
circuits may be damaged, but not a PCB structure.
Second: in order to let a discharge happen to your Newt (and especially to
the logic board) the charged body needs to have access to any other
conductive part. The distance must be small enough (depending on the voltage
the body is charged to - a few millimeters to 1-2 cm) to let the spark
spring. In case of the Newt the spark might go through the plastic case but
will stop at the inner conductive layer except you have the Newt opened.
Third: as long as the second body involved has no connection to ground (as
our Newt) the discharge current will be much lower and only as long as both
bodies have a different potential. (The potential is getting equalized due
to the discharge current)
What I can imagine and what happened a lot during EMC (electromagnetic
compatibility) ESD (electrostatic discharge) tests is, that digital circuits
were often triggered due to the discharge current. This might happen to the
Newt as well.
But I would never believe that a PCB track has blown due to a discharge of
electrostatic energy. This looks rather like a problem with the converter
for the backlight or some traces for power, which are located near the ROM
as well.
Johannes
> -----Original Message-----
> From: newtontalk-bounce_at_newtontalk.net
> [mailto:newtontalk-bounce_at_newtontalk.net]On Behalf Of Phil Denton
> Sent: Monday, April 08, 2002 3:51 PM
> To: doppler
> Subject: Re: [NTLK] newton switch on by itself
>
>
>
>
> On April 08 2002, doppler <doppler_at_mac.com> wrote:
>
> >>> I notices my Newton will switch itself on by itself.]
> >>> it is draining the batteries.
> >>
> >> Usually, all Newton will wake up at 3am to perform some
> cleaning tasks, =
> like
> >> forwarding any To-dos to the next day.
> >
> >actually, my green friend is behaving really strange in a caterpillar =
> jacket
> >of some plastic material. i guess it has to do with static electricity.
> >newton keeps powercycling until the accupak drains :( i have to keep the
> >newt in a separate bag, even dough i got the jacket because of its newton
> >friendly-sized pockets...
>
> Roman
>
> I have recently seen a Newt with one of the tracks near the ROM
> and memory =
> chips "blown" as if exploded over a very small area. The owner said it =
> happened at switch on and under magnification it looked quite
> dramatic. I =
> reckon it was caused by 'static' discharge.
>
> 'Static electricity' can be generated a.o causes by the lifting/tearing =
> away action as e.g. sticky tape being lifted off another surface. If our =
> Newts could be damaged by this 'static' charge I wouldn't risk using a =
> synthetic case, especially if it had a velcr* type closure just in case.
>
> Your message suggests a correlation between the synthetic case and the =
> unexpected turning on. Would you deduce that from your recent
> experience? =
> If so it seems 'static' discharge might somehow be involved.
>
> Phil Denton
>
>
>
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>
>
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