Subject: Photoflash firing circuit
From: "Gordon Campbell"
[email protected]
Date: 3/3/2004 8:27 PM Central Standard Time
Message-id: <%
[email protected]>
Evening, all. I apologize if this is the wrong group to make this sort of
request, but I've run out of ideas.
I'm looking for a schematic of a circuit that will randomly fire a
collection of photo flash units.
I'm working tech for a play next month and we're looking to simulate
electronic arcing with the flash units. I can find dozens of timers circuits
to fire the flashes, but every last one uses a set time. I need random or
something approaching that. I've never seen electrical shorts that arced in
a set pattern. ;-)
A few questions. How many photoflash units do you have? Are they voltage
triggering or switch contact triggering? What is the recharge time for the
photoflash units?
Assuming you have contact triggering, it might be easiest to just go with 1 ea.
555 trigger circuit for each strobe. Each 555 would drive a small reed relay,
which would provide the trigger for each strobe. You could run the whole
shebang of triggers off one 6V lantern battery, and if you had more than 5
strobes, it would look semi-random.
However, I'm guessing your photoflash takes a couple of seconds to recharge, in
which case your photoflashes will look like a bunch of cameras going off rather
than an arcs & sparks event.
One thing you might want to consider, if you've got a bit of a budget and are
handy with a soldering iron, is getting half a dozen DIY K163 strobe kits (use
the 0.1 uF cap rather than the 0.47 uF cap for .2 to .4 second cycle), and a
12VDC power supply, like the ones available at Radio Shack (13.8VDC is OK
here). The kits are about $15.50 ea. Set all the pots for different times.
It will give you the randomness you seek, and probably would look more
realistic than your photoflash (although the photoflash would probably be
somewhat brighter -- a reflective backing and good sound effects would help
here). Just turn on the 12VDC to turn your show on, and turn off the power
supply to turn it off.
You might be somewhat disappointed with either solution, because a flash
doesn't have the high UV content of an arc. It will, alas, have the color of a
flashbulb, no matter what. A light purple wash filter on one of the strobes,
and light blue wash filter on one more may help here. Stay far away from the
temptation to use an arc welder here to get your spark light -- safety always
first backstage.
Good luck, and break a leg
Chris