Thanks MikMo,
That's helpful. Using these shift-register thingys to control the on/off sounds a lot cheaper than investing in DMX 512 equipment.
Do I have to be careful about what the phase of the 220v is when I switch it? I've read warning about this in other forums, but don't quite understand.
Also, can I get a relay that will control 220v directly from arduino voltage levels or do I need to "boost" it with another relay (in what I believe is called a darlington pair)? Or maybe these things already come with a darlington pair built in and all I have to do is connect it to the arduino. Still, this "phase crossing" thing probably still applies.
-Nicholas