Strobe from old camera?

[Geoffinpdx]

Does anyone here have instructions on how to convert a junk camera flash for use as a strobe for model aircraft? Since I'm a complete idiot when it comes to electronics, please keep in down to sixth grade level! ;)

[brtlmj]

It is not very difficult. I am not sure if you want to try it, though. You'd have to deal with voltages in excess of 200V. It might not kill you, but can be extremely unpleasant.

Anyway, you'd have to:
- Find the main capacitor and replace it with a smaller one (I'd try one-tenth of the original value). You do not want a powerful flash every 15 seconds, you want a weaker one every second or two.
- Make a square wave generator to trigger the flashes. There are hundreds of possibilities - see an example here: http://www.daycounter.com/Calculators/NE555-Calculator.phtml You'd have to add a thyristor at its output.

If your camera has a neon light to indicate that the flash is ready, you can use it to trigger the flash as soon as the capacitor is charged. You'd only need a thyristor and resistor then - no generator.

Overall we are talking about <$10 worth of components.

[westfw]

Wire a sidactor (130V to 240V) across the trigger contacts. Sidactors are a bit hard to find, but not expensive: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=K2400E70-ND
Use a smaller cap for higher repeat frequency.

I did some PCB layouts that miniaturize the strobe for use in model rockets, starting with the parts from a Fuji disposable camera:
http://homepage.mac.com/westfw/PhotoAlbum10.html
http://homepage.mac.com/westfw/.Public/Fuji-strobe.zip

Note that there have been reports that strobes are "noisy" in the RF spectrum and can interfere with radios...

[Geoffinpdx]

Note that there have been reports that strobes are "noisy" in the RF spectrum and can interfere with radios...
Would a spread spectrum radio solve this?

[vintage1]

Would a spread spectrum radio solve this?

It should help, but I wouldn't bet on it..

[Gary Warner]

Sorry to jump in with this, but I recall something very bad about tinkering with camera flashes. I had one and was playing around with it. I wanted to be sure the capacitor was discharged, so I shorted it with a screwdriver. It was fully charged and resulting BANG was loud enough that I had ringing in my ears for over a day. It was like standing right next to a gun going off. That couldn't be good for my long term hearing.

[dleroi]

Probably not a good idea to discharge a capacitor with a screwdriver - unless you have a high resistance one. ;)

[westfw]

Yeah; playing with the flash is not for the faint of heart. My usual procedure is to charge up the flash, remove the battery, trigger the flash, and then short out the remaining charge on the cap with a screwdriver (it'll still make significant sparks, but probably not hurt your ears any more. Wear eye protection.) Needless to say, shorting out the cap with your finger instead of a screwdriver is going to be significantly painful in either the fully charged or partially charged condition.

[dleroi]

I've had my share of jolts, too, from back in my repair days. But, I always used a resistor to discharge the caps. I had one wired up with alligator chips just for that purpose.