After a DIY disaster (spending $35.- and 8 hours of blood, sweat and tears ), I found a simpler solution to make a sound trigger for a flash. The article seems rather old because they talk about film.
http://people.rit.edu/andpph/text-cheap-sync.html
I have a few questions:
1. They write to use a 400 volt BRY 55 400, which is a SCR (Silicon Controlled Rectifier, no idea what it means, but I can solder it together). For a SB600 would that be correct or too much or little?
2. What kind of store would sell those? I live in Portugal where electronic parts are more rare than gold.
3. Instead of an old tape recorder, I'm guessing I can use my PC or notebook for this? I think it's easier to control both the mic and the out port, but maybe I'm wrong?
I'm still trying to find a PC sync hotshoe with a cable, but no such luck. Probably have to import it from Holland or something.
Thanks!
A silicon-controlled rectifier, or "thyristor," is an electronically controlled diode, a kind of electronically controlled switch. Roughly speaking, when you apply a control voltage to the "gate" of a thyristor, current will flow across it (in one direction only from the "anode" to the "cathode"), otherwise current will not flow.
In the device described, the audio signal is connected to the gate. The anode and cathode of the thyristor are connected across the two terminals of the PC sync circuit. When the audio signal spikes, the thyristor triggers, the PC sync circuit is completed, and the flash fires.
Historical sync circuits used in strobes used to pass quite a bit of transient voltage. Modern strobes do not pass this kind of voltage, and modern cameras as not designed to take it either. So you would not need a high voltage thyristor. Someone with more specific knowledge will have to advise you on how to get the thyristor selected and wired up.
You would not want to use a computer to pass audio because of the time latency required to digitize the microphone input, buffer it, and convert it back to analog. This will take a few milliseconds minimum, and possibly more as the modern PC isn't a real time system. This will be enough to mess up your timing.
The best I can recommend is that you buy a commodity measurement mic and inexpensive microphone preamp to drive your flash controller. The Behringer ECM8000 measurement mic is a good choice because it is cheap and accurate, and it will pass sharp transients (gunshots, or whatever) very well. The very cheap Behringer Mic100 Ultragain should work as a preamp. B&H has both of these things, and they are useful tools.
Good luck, Luke
