It is better than those slave adapters that "look" for a flash, and then quickly activate the flash, since those adapters can be set off by other cameras. If you're at a party, that can be quite annoying.
Step 1: What you need:
- a sense of electronics
- an Optocoupler with triac output (i.e. MOC3062)
- 2 capacitors ( 10 ÃÂµF )
- 3 resistors ( 500, 1M, 30...80 ohms)
- a casing (optional, I got mine on ebay)
- a battery