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Lots of electrolytics...




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From:  Bill Lemieux [SMTP:gomez-at-netherworld-dot-com]
Sent:  Thursday, March 05, 1998 2:30 PM
To:  Tesla List
Subject:  Re: Lots of electrolytics...

Tesla List wrote:
> I believe that you can use a strobe flash tube as sort of a thyratron to
> switch power from your electrolytic capacitor bank.

Well yes, for smaller currents, but flashtubes have a rather high
on-resistance.
Run the voltage up to overcome this, and you will probably see it
shatter.
They don't like very fast turn-on times.  EG&G used to have a free
"Flash Tube
Design Guide" that covered the safe operating area of flashtubes.

> Theoretically one could
> use many flash tubes in parallel for higher power outputs.

I don't think so.  In all likelihood, one tube will fire before the
others
and take all the current.  Flash tubes are not inherently low-jitter
designs,
but they do turn on fairly fast.  This makes it difficult to cause
multiple
flash tubes to fire simultaneously.

> The Radio Shack
> xenon flash tube 272-1145 may work but is listed as a 4 watt-sec maximum
> flash energy. Anode voltage is from 200 - 400 V. Trigger voltage is 4kV.

Trigger voltage of any spark gap-type switch (including thyratrons,
trigatrons,
flashtubes, etc) should always be >/= 10X the voltage across the switch
for
low jitter (repeatable turn-on time) operation.

> Camera strobes use electrolytics so the flash tube appears to prevent
> voltage reversal on the cap itself.

And then there's the nearly non-existent inductance of the load...

> If you do try this method, please let us
> know what the extreme maximum flash energy possible with the Radio Shack
> flash tube is. You may be able to trade higher flash energy for lower life
> cycles.

Absolutely. I bet the RadShak flashtube would switch 100 watt-seconds...
once.

Incidentally, a friend of mine _has_ used a strobe circuit discharging
through
a solenoid to fling BB's around...

-Gomez

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