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Building a Lightning Detector
Name: Jon
Status: Other
Grade: Other
Location: AE
Country: United States
Date: April 2008
Question:
I wish to make a 'lightning detector' as
described by Robert Penfold the famous scientist in
Everyday Electrics about 30 years ago. To make it
you would need: 1 neon 1 collector (a 12 inch square
piece of aluminium) 1 capacitor ( value not known)
an earth. He said a neon fires at 110 volts and dies
at 90 volts so you connect the neon and the
capacitor to the earth. The collector would collect
the static in the air and so charge the capacitor
until it reached 110 volts. The neon would then fire
and discharge to earth until the current fell to 90
volts at which point it would turn off and repeat
the cycle.
The amount of static in the atmosphere
would regulate how often the neon fired. I know that
it works as I built one years ago but I am afraid
that with the passage of time I have forgotten the
value of the capacitor (I seem to recall that it was
'20' something but I have tried so many values but
nine seem to work. I would dearly love to remake
this as it is simplicity itself -- no batteries
--just make, fit and enjoy.
Replies:
Hi John,
The capacitor value is not at all critical. A larger capacitor will
take longer to charge each time, but will discharge more energy into
the neon lamp, resulting in brighter flashes. A value of 10 or 20
microfarads would take a long time to charge, but produce a bright
flash in the neon lamp. The problem here is that this type of
capacitor is a so-called electrolytic type, and is polarized (there is
a positive and negative terminal). Unfortunately, there are lightning
discharges, and static buildup, of either polarity.
To avoid the polarity problem, I suggest you use a 0.1 to 1.0 uF (or
microfarad) mylar or ceramic capacitor. These types work with either
polarity. The neon lamp flash will not be as bright as with a larger
capacitor, but at least it will charge faster.
By the way, a typical neon lamp for this project would an "NE-2" lamp.
also note that the voltage rating of the capacitor must be at least
200 volts.
The connections are as follows: Connect the capacitor in parallel with
the neon lamp. Then one terminal of the lamp/capacitor pair is grounded
and the other terminal connects to the plate.
Good luck but be careful.
Regards,
Bob Wilson
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