his project is mainly based in this one from Glaciar Wanderer. I just liked his idea and worked it on my own. (I think this guy and me would be friends, as the projects he has in his photography category are things I’ve been wanting to do since I got my Arduino.
I will not be using a microphone as sensor, at least not right now. On the other side I am using a transistor to control the laser instead of using a digital output of the arduino board directly, as I pretend to use more than one laser, and using a transistor will allow me to draw more milliamps than the Atmel chip can provide.
I used a 4N26 optocoupler to trigger the flash, connected to a hotshoe-to-pc-sync adaptor in my Vivitar 285HV. Using an optocoupler you get sure that no current from the arduino will go to the flash, and no current from the flash will go to the arduino. Anyway, you should check the trigger voltage of your flash, as if it has a high voltage (even hundreds of volts) it could damage the optocoupler and everything that is connected to it (arduino, computer, you…).
In the 285HV the center pin is the “live” one, thus it is connected to pin 5 of the 4N26, you should check this in your flash, as I think some brands have this “swapped”. For this I used my camera and flash trigger module
For more detail: Flash trigger