Help with Flash Trigger Circuit


http://arduino.cc/forum/index.php/topic,148666.0.html

I am having a problem with this circuit. I can detect noise and see the serial monitor respond, however the flash will only fire when I remove a wire and from the circuit. Does this possibly have with the fact that I am using a disposable camera flash unit. Any help is appreciated.

Does this possibly have with the fact that I am using a disposable camera flash unit.

I wouldn't be surprised if a disposable camera flash had a much higher trigger voltage than your transistor can handle. Be very, very careful.

however the flash will only fire when I remove a wire and from the circuit

Shall we guess which one, or are you going to tell us?

I was thinking the same thing. Removing any wire of the flash from the circuit triggers it. This is most likely due to the fact that connecting both wires fires the flash and me removing a flash pin is probably just a faulty connection. I'll try changing around the circuit and see if it works. Do you know of any similar circuits that would work. I know I could use an optoisolator but my local store All Electronics does not have the one I need.

For higher voltages, my favourite is a MOC3020 opto-triac (I have some old Vivitar 283s with triggers in excess of 150V - fine with my old mechanical film cameras, but instant death to my DSLRs)
You could use a relay, I guess.

Have you measured the voltage across the open trigger contacts?

I have measured the voltage. Actually, the max voltage seems to vary on different flash units of the same type. It could just be the amount of time it is charged from the battery, or because the boards are old and used.

Sometimes the easiest way to interface with flash button contacts is by using a small 5vdc reed relay. Then you don't have to be concerned or know about the voltage level, voltage polarity, or trigger current requirement of the flash. This kind of relay can be directly powered by an arduino output pin, although you should add a diode across the coil terminals.

http://www.allelectronics.com/make-a-store/item/RLY-496/5-VDC-SPDT-REED-RELAY/1.html

http://www.allelectronics.com/make-a-store/item/RLY-495/5-VDC-DIP-REED-RELAY/1.html

Carnyworld: I have measured the voltage. Actually, the max voltage seems to vary on different flash units of the same type. It could just be the amount of time it is charged from the battery, or because the boards are old and used.

Or it could be that over the years the manufacturers redesigned the flash internals, particularly as the electronic cameras came out that weren't as tolerant of high voltages. Often times, the manufacturer would not change the model number when they did these internal changes. Sometimes you can see it by flashes made at different factories in different countries.

Im going to go ahead and order parts for a circuit that is known to work. I feel that I am going to put more money into troubleshooting the circuit I have than buying a working kit.