Step 1: Go get stuff
- Camera Flash (with input jack)
- MOC3021 optocoupler (Triac)
- 220 ohm to 1K resistor
- 3/32" mono plug
- Solid core wire
Step 2: Wire the plug
Reassemble the casing.
Step 3: Wire it up
Connect the other leg of the 1K resistor to pin 1 of the chip (this is the pin next to the dot).
Connect ground from the Arduino to pin 2 on the chip.
Connect the red wire from the 3/32" plug to pin 6 and the black wire to pin 4.