Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hp-pcd!hplsla!tomb
From: tomb@hplsla.HP.COM (Tom Bruhns)
Newsgroups: sci.electronics
Subject: Re: HV Cap Fun!
Message-ID: <5170032@hplsla.HP.COM>
Date: 26 May 89 15:52:27 GMT
References: <4924@m2c.M2C.ORG>
Organization: HP Lake Stevens, WA
Lines: 40

jds@m2c.m2c.org (jds) writes:
>  I just picked up a couple of 14ufd 25KVDC caps and am looking for something
>to do with them...  I'm looking for good demonstations, experiments, etc.
>I figure these guys could be used for a nice spark-gap demo or perhaps 
>vaporize wire.  
>
>  If you've got any ideas, let me know!
>
>-- john
>----------

Lesseehere...  That's about 8750 joules when both are fully charged: nearly
nine kilowatt seconds.  That's enough to do significant damage,
especially if it's released quickly.  You didn't mention if the caps
are rated for rapid-discharge service, however.  Those that aren't can
be damaged by too-rapid discharge, and usually also cannot be
discharged in microseconds because of their inductance.  

That out of the way, one neat thing to do is to flash a large
flashlamp through them.  You may be able to find an appropriate one as
a "pull" from a laser or an airport approach system.  These generally
will be rated for lower voltage than your caps, but 28 uF at 5 or 6 kV
is still a pretty good jolt -- or a lotta light.  _OBVIOUSLY_BE_VERY_
_CAREFUL_WITH_THIS_ENERGY,  WHATEVER FORM YOU CONVERT IT TO!!!
The amount of light involved could make you (or a friend, neighbor,
pet, etc.) blind very quickly, like in microseconds.

In fact, BE CAREFUL WITH THE CAPS EVEN WHEN YOU THINK THEY ARE
DISCHARGED!!!   Put a shorting strap across them any time they aren't
actually in use.  Handle them only through a long plastic rod that you
know is a good insulator, any time you think they may have any charge
on them; build a discharging resistor that you can put across them to
bring them down in a controlled manner -- have an indicator in the
discharging resistor that will tell you when they are discharged to a
safe level -- be sure that the resistor can handle the voltage and
power (probably about 25 2-watt metal film resistors in series would
do well -- they are noted for their ability to not open under an
overload, but DONT exceed thier voltage rating).  SAFETY FIRST!!

Have a good day -- and a safe one!