Control a camera flash using TTL signals by Hemal Chevli
So finally bought a new flash, and powered up, I used one of my keys to shot the pin and base plate and IT WORKED! Next I measured the voltage between centre pin and base pin, it was 5V. Things were simple from this point, pulled out and opto isolator, connected the led side to uC and transistor side to the centre pin and base plate. On your arduino you can wire pin 13 to the opto-isolator and upload the blink sketch to fire the flash instead of LED . I had to hot glue the wires on the base plate. With the TTL input you can pretty much do anything to control it, perhaps use a 555 for periodic flashes, may be use for your next water drop photography.