I'm designing a box that has +48 and -48 power supplies, each bypassed
with 44,000 uF. I figure it will take forever to discharge when the
power is switched off, and I don't want to waste a heap of power on a
bleeder.

So I figured I could put an LED on the board to alert our test people
that the board is still hot, and have a DISCHARGE pushbutton. So what
I'm thinking is

http://dl.dropbox.com/u/53724080/Circuits/Cap_Discharge.JPG

Turns out that using a 30 cent mosfet and a 15 cent pushbutton is
better than buying a switch rated for 1 amp at 100 volts DC.

I wonder if I could dump the energy into a mosfet, namely get rid of
the power resistors and add a smaller source resistor, to make the
power fet into a current sink. It's tempting, but then it might blow
up. There's about 100 joules to dump.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation