Date: Sun, 25 Aug 1996 00:24:23 -0600
From: dave <skeeve@henge.com>

POWER RESISTOR

On occasion one has need for a very high ohm resistor to limit the current
in some high voltage use. My particular application is in charging 20uf 25kv
power discharge caps for a flash pumped organic dye laser. 

Rather than spend alot of time soldering resisters together, I went down to
the local checkers store and purchased a couple of feet of standard black
rubber vacuum tubing, 3/16 inch id. This tubing is mostly carbon just like
resistors and conductive with a very high resistance per foot. I take the
necessary length of tubing and insert it into a larger size of clear vinyl
tubing (at least 1/8 wall thickness). This tubing serves as an insulator.
Then to provide connectors for the resistor/tubing, I push a screw into each
end of the tubing. Voila! A super simple, cheap, safe resistor! And flexible
to boot. 

One addition, to this tip: If you are pulling more than 20 milliamps, the
tubing can get rather warm. In such cases, I use small brass tubing instead
of screws for the end terminals, and connect one of the terminal tubes to
the output of an aquarium pump via at least several feet of small clear
vinyl tubing. Air is pumped through the resistor tubing, giving you an cool
running resistor.

Best wishes!  (Also, don't smoke yourself!) :-) 

dave