Okay, so I'm using an Arduino Uno R3 and I wanted to start of my own home automation project. I have a 4 channel 12V relay board and I normally connect it to a 12V 500mA adapter. What is the maximum wattage bulb (or CFL) that I can power with this configuration?
Unless you feel like starting a fire, none. Find a 220V 2A relay with a 5V coil and use that instead, switching the hot wire and not the neutral.
Huh? If the OP builds a circuit to switch 12v (with a flyback diode) why would the relay board in question start a fire?– Duncan CJan 7, 2015 at 3:11
@DuncanC: There aren't many CFL bulbs that run on 12V, and the asker hadn't given the contact specifications yet. Jan 7, 2015 at 4:23
Watts = Amps x Voltage