How do I turn some Christmas Lights (Strand that plugs in to the wall) in to a clapper style light. I have a relay and a mic.
:o For Christmas in a few days, or Christmas next year?
Microphones need a preamp. Electret condenser mics need power. With audio, you generally need a biased output so the Arduino can read the negative half of the AC waveform. Sparkfun makes a [u]microphone breakout board[/u] with a microphone and all of the required circuitry. Or if you want to build it yourself, Sparkfun publishes the schematic so you can copy their design or use their design as a starting point.
Most relays require a driver circuit to "boost" the coil voltage/current.
You'll need a filter (in hardware or software) to filter-out low frequencies and make the thing more sensitive to a clap. Then, you'll need some timing (probably in software) to identify a quick clap while ignoring higher frequency sounds that last longer.
google arduino clapper