strange behavior of laptop during thunderstorm

[Allan Adler]

I was using a laptop a few weeks ago during a thunderstorm. I knew
about the storm and was running the laptop on battery for that reason.
This laptop runs RedHat Linux 9 and for reasons I don't understand
won't use the full screen for X, but only about half of it, but one
can still use it, and that is what I was doing during the thunderstorm.
At a certain point, there was some lightning nearby and suddently
the computer display was occupying the full screen. But it also
was hanging and wouldn't respond to commands, so I turned it off
and rebooted it. It's tempting to think that this had something
to do with the storm, but I was running the laptop on battery.
Still, I remember when I was a kid hearing stories of electric
lights dimming when someone took their sweater off, apparently
due to the static charge from the wool, so I don't entirely
rule it out. I was using the laptop in a basement apartment
and maybe there was a very slight change in ground potential
during the storm, which got transmitted through my feet and then
my fingers to the laptop. Or, when I use an oscilloscope sometimes
(my old EICO 460) the signal displayed on the scope depends on how
close I am to the probe; I've been told that this is due to the fact
that the body acts as an antenna somehow. So maybe instead of changing
ground potential, it was my body acting as an antenna and transmitting
some electrical disturbance due to the lightning. I don't like to speculate
about these possibilities since I really don't know what I'm talking about.
The laptop has shown no signs of damage since then.

It was always my impression that it is perfectly safe to operate
a laptop under battery during a thunderstorm, but this experience
is making me wonder. Can someone please clarify this point?

 

[Charles Schuler]

Coincidence?

 

[Allan Adler]

Coincidence?

Probably.

 

[Jerry G.]

It is hard to answer your question about the laptop. But, it is possible for
electronic equipment to be damaged with a lightning storm near by, even if
it is not plugged in to the AC.

One strong reason for electronic equipment damage from being close by to
lightning, is from inductive pickup. Lightning consists of a very rapid
array of sparks, which comprise of many harmonics, and have a very high
intensity of an electrical noise discharge. Since the sparks are very
rapidly varying in its intensity, they can be very reactive in their nature.
Even a trace on a circuit board, if it can act as a resonant receiver to the
lightning induced electrical energy, the trace can become like a tuned
receiver and transfer some electrical energy to anything connected to it.
Many of the characteristics, and the way that the particular lightning
strike may occur can be very random.

I have seen lightning damage to sensitive instruments and electronic
equipment, that were completely disconnected from the AC, and not even
turned on. Most of the time, when this occurs, the lightning strike has to
be very close.

--

Jerry G.
==========================



I was using a laptop a few weeks ago during a thunderstorm. I knew
about the storm and was running the laptop on battery for that reason.
This laptop runs RedHat Linux 9 and for reasons I don't understand
won't use the full screen for X, but only about half of it, but one
can still use it, and that is what I was doing during the thunderstorm.
At a certain point, there was some lightning nearby and suddently
the computer display was occupying the full screen. But it also
was hanging and wouldn't respond to commands, so I turned it off
and rebooted it. It's tempting to think that this had something
to do with the storm, but I was running the laptop on battery.
Still, I remember when I was a kid hearing stories of electric
lights dimming when someone took their sweater off, apparently
due to the static charge from the wool, so I don't entirely
rule it out. I was using the laptop in a basement apartment
and maybe there was a very slight change in ground potential
during the storm, which got transmitted through my feet and then
my fingers to the laptop. Or, when I use an oscilloscope sometimes
(my old EICO 460) the signal displayed on the scope depends on how
close I am to the probe; I've been told that this is due to the fact
that the body acts as an antenna somehow. So maybe instead of changing
ground potential, it was my body acting as an antenna and transmitting
some electrical disturbance due to the lightning. I don't like to speculate
about these possibilities since I really don't know what I'm talking about.
The laptop has shown no signs of damage since then.

It was always my impression that it is perfectly safe to operate
a laptop under battery during a thunderstorm, but this experience
is making me wonder. Can someone please clarify this point?
--
Ignorantly,
Allan Adler <[email protected]>
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions
and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.

 

[w_tom]

If nearby lightning fields could do to a laptop as others
have suggested, then every nearby automobile radio and every
nearby cell phone is also damaged. Nearby strikes do damage
because they make direct connections through the electronics.
A camping lesson:

They were sleeping near a tree that was struck. Those
sleeping parallel to the tree were not harmed. But two
sleeping perpendicular to (pointed towards) the tree required
emergency medicial assistance. Lightning traveled down tree
seeking earth borne charges some kilometers away. A shorter
electrical path to those charges was out of ground, through
the feet, and back into earth via the head. Only those
campers were harmed.

Same could have happened to your laptop. Charges up out of
a conductive concrete, through fingers, into laptop, then back
into earth via table. Was table non-conductive (glass) or
conductive (plastic or wood)?

Furthermore, was anything else connected to that computer -
printer cable (even withtout a printer), modem, etc? Was
there an insulated wire draped out back of machine onto
floor? These could have been conductors to complete the
circuit.

One way to avoid future problems would be a conductive
plastic (anti-static) sheet on floor underneath both computer
table and human.

To have a transient, one must first establish a complete
circuit. Often a destructive transient will enter computer on
AC electric, pass through motherboard and modem, then leave
via phone line. The transient would have been in contact with
virtually every semiconductor IC on motherboard. Why were
those others IC (ie RAM) not damaged? No outgoing path means
no electric current and therefore no damage; as was taught in
elementary school science.

So yes, there must have been a complete circuit - incoming
and outgoing - via the laptop. The most interesting question
remains what that circuit was.

It gets more interesting. I setup a computer on a glass
table top. Then build up static electric charges with leather
slippers on a nylon carpet. I then static electric shock the
computer case so that charges must pass across chassis and
down a wire back to nylon floor. If motherboard is mounted on
multiple conductive standoffs, then computer crashes. If
mounted only on one standoff, then computer operates
unaffected. Why? Again, the complete circuit. With multiple
standoffs, then static electric passes across motherboard
logic ground. But with only one conductive standoff, an
incoming path but no outgoing path exists for that static
electric discharge. Ergo, no computer crash.

So yes, a transient need not even go through semiconductors
nor do damage to make a computer crash. A potential
difference across the motherboard's large copper ground plane
can cause strange computer actions.

This becomes too complex for some. So they speculate that
nearby lightning creates these mythical, massive, destructive
fields. Problem remains that numbers are never provided to
prove that speculation. We call that junk science reasoning.
Many materials they 'think' are non-conductive are, instead,
conductive to high voltage, high fequencey transients such as
lightning. Hope this helps.

 

[John Miller]

Nearby strikes do damage
because they make direct connections through the electronics.

True, but incomplete and misleading. Nearby strikes also do damage because
of induction and RF transmission.

--
John Miller
Email address: domain, n4vu.com; username, jsm

He: Let's end it all, bequeathin' our brains to science.
She: What?!? Science got enough trouble with their OWN brains.
-Walt Kelly

 

[H. Dziardziel]

snip

You hit the screen expansion key combination or XFree's screen
mode-resolution key combination? The freezing up and less than
full screen suggests the mode change..

 

[Allan Adler]

Same could have happened to your laptop. Charges up out of
a conductive concrete, through fingers, into laptop, then back
into earth via table. Was table non-conductive (glass) or
conductive (plastic or wood)?

Wood.

 

[R. Steve Walz]

Allan Adler wrote:
[]

It was always my impression that it is perfectly safe to operate
a laptop under battery during a thunderstorm, but this experience
is making me wonder. Can someone please clarify this point?

------------------
Y'know that "click" you often hear right before a lightning strike
that is REALLY close to you, a real window-banger? Well, if you
recorded the sounds with a shielded recorder you wouldn't hear it!!
It's neurological EMP artifact in your BRAIN from the induced
broad-spectrum signal!! Same in your laptop, its circuitry is an
antenna!! It's bound to lock it up sometimes!

If you want a lightning-proof laptop, then put it in a Faraday
cage!

-Steve

 

[w_tom]

Then again, put up those numbers. Explain how all nearby
car radios and cell phones with external antenna connected to
the most sensitive transistor were not damaged by the same
field that penetrated the computer. Again, where are these
numbers that prove such damage occurs. If nearby strikes do
damage because of induction and RF transmission, then lets see
those numbers, all those damaged walkmans, and all those
routinely damaged portable phones.

Using the same reasoning, I could even claim that airplanes
cause computer damage. I am asking for numbers since everyone
who makes claims about 'induction and RF transmission' cannot
even provide basic electromagnetic field numbers to prove
their point.

It nearby strikes do such damage, then the devices most
susceptible - especially portable AM radios - would be
routinely destroyed by nearby strikes. If they are not, then
such electromagnetic fields are not damaging computers.

 

[w_tom]

Wood, just like the tree those campers were sleeping next
to, is a conductor. Incoming via fingers. Outgoing via wood
table. This is only one of many possible paths causing laptop
interruption.

 

[John Miller]

Using the same reasoning, I could even claim that airplanes
cause computer damage. I am asking for numbers since everyone
who makes claims about 'induction and RF transmission' cannot
even provide basic electromagnetic field numbers to prove
their point.

Has it occurred to you that the reason the "numbers" are not forthcoming may
have nothing to do with lack of data, but rather, the likelihood of its
being absorbed?

 

[w_tom]

Prove your point. Provide the numbers. Stop with spin
politics about number absorption. Explain why all those
nearby radios - especially AM radios - are not damaged by
nearby fields. Stop wasting good bandwidth with excuses. Put
up those numbers and facts.

I know one reason why those numbers are never posted. Those
who claim 'induction and RF transmission' cause damage never
even repaired lightning damaged equipment by traceing the
direct strike path let alone take two semesters of
Electromagnetic Fields class. Too many newsgroup posters just
know because previous posters said so. Junk science reasoning
promotes these myths. Nearby lightning causing destructive
fields is promoted by the same logic that promoted Geritol and
Listerene.

Prove me wrong. Provide numbers for those fields.

 

[Charles Schuler]

Y'know that "click" you often hear right before a lightning strike
that is REALLY close to you, a real window-banger? Well, if you
recorded the sounds with a shielded recorder you wouldn't hear it!!
It's neurological EMP artifact in your BRAIN from the induced
broad-spectrum signal!! Same in your laptop, its circuitry is an
antenna!! It's bound to lock it up sometimes!

I have heard that sound and always assumed that it was arcing in the
electrical outlet boxes. Never heard it outside. Do you have a source of
information on this?

 

[John Miller]

I know one reason why those numbers are never posted. Those
who claim 'induction and RF transmission' cause damage never
even repaired lightning damaged equipment by traceing the
direct strike path let alone take two semesters of
Electromagnetic Fields class. Too many newsgroup posters just
know because previous posters said so. Junk science reasoning
promotes these myths. Nearby lightning causing destructive
fields is promoted by the same logic that promoted Geritol and
Listerene.

I can state with some authority that if a EE PhD told you in general terms
about induction and RF transmission, you wouldn't belive it. So I'm not
going to bother. Perhaps someone else will.

 

[w_tom]

John's response breaks down into the classic "he just knows
that induction and RF transmission causes damage"; without any
scientific knowledge. He cannot provide numbers and probably
does not even know what numbers would be required.

John Miller demonstrates how so many claim that damage
happens. He just knows that the electromagnetic fields from a
nearby strike all but destroys life. Clearly those undamaged
nearby radios must be an anomaly. He needs no numbers, no
professional citations, and no classes in basic electrical
engineering. He is above all that. He just knows, which is
why he will not provide numbers.

In the meantime, those nearby radios, et al are damaged when
the nearby lightning strike actually is a direct strike to
electronics. When a current flows into and out of the
electronics. Knowing this, then commercial buildings, cell
phone towers, etc are all easily hardened from lightning
damage. The heart of a protective system is the essential
single point earth ground.

Cited earlier was an example where a nearby strike harmed
sleeping campers. Lightning induced fields caused harm? Of
course not. Some campers were sleeping so that they became
electrical conductors. The nearby strike actually conducted
electricity through their bodies. They suffered a direct
strike.

How to protect yourself from a nearby strike? Wrap yourself
in electromagnetic shielding as John Miller insists? Of
course not. Remain with both feet together to create a single
point ground. Therefore the nearby strike will not conduct
electricity through your body. The nearby strike will not
become a direct strike.

 

[Don Klipstein]

Then again, put up those numbers. Explain how all nearby
car radios and cell phones with external antenna connected to
the most sensitive transistor were not damaged by the same
field that penetrated the computer. Again, where are these
numbers that prove such damage occurs. If nearby strikes do
damage because of induction and RF transmission, then lets see
those numbers, all those damaged walkmans, and all those
routinely damaged portable phones.

I thought the original post claimed that the computer was interfered
with, not damaged.

My own computer often malfunctions and locks up from static discharges
that only cause a "pop" sound in radios, TV, and audio equipment.

I have also heard of Tesla coils locking up and rebooting computers
several feet away, and radios, TV, and audio equipment normally have
interference effects. Usually, none of the above suffers any damage.

- Don Klipstein ([email protected])

 

[Don Klipstein]

Wood.

Plastic is nonconductive, and I doubt wood is conductive enough for
this. I suspect inductive coupling or a pulse of RF.

- Don Klipstein ([email protected])

 

[Don Klipstein]

I have heard that sound and always assumed that it was arcing in the
electrical outlet boxes. Never heard it outside. Do you have a source of
information on this?

I have heard it. I have only heard it when outdoors or at an open
window. Having a windowscreen between me and the lightning does not
change this sound much, but having glass in between does. I thought it
was from a very slight but very sudden pressure change in the air from the
air absorbing shortwave UV radiation from the lightning.
What I thought this was is definitely what happens with quartz xenon
flashtubes that make really noticeable snap/pop sounds.

I have heard of radar pulses causing audible effects, believed to be
from sudden but extremely slight pressure rises in the heads of people
being exposed.

- Don Klipstein ([email protected])

 

[w_tom]

When talking about these types of voltages and currents,
then wood, some plastics, concrete, wall paints, and linoleum
all become good conductors. Some better than others.

Rather interesting to 'feel' what is and is not conductive
simply by building up static electricity. The more
conductive, then the more pain. Some conductive items
discharge without any pain (ie wall paint) - not as
conductive.