So I have been trying to figure out how I can switch 220Vac on and off with a microcontroller. I learned that I need a triac or relay and then need to isolate it with an optocoupler. So I bought some parts off digikey and breadboarded this thing up. The odd thing is that I can't get the lightbulb (what I am currently using as the load) to turn off. No-matter the input on terminal two of the opto-coupler (right now I just have it running off of a external power suppply). I even tried disconnecting the gate of the triac (for a floating voltage) and the bulb was still on. Any ideas for how I can get this thing to switch on and off? I kind of wonder if these optocouplers even work.