Powering and controlling multiple 12V LED strips with Arduino LilyPad USB
Simply use a 4 pin opto coupler PC817. It has 4 pins. Connect pin1 to the pin of your lilypad, pin2 is gnd. Apply 12 v on pin 4. Connect a pull down 10k resistor on pin3 and check the output from this pin, you will get 11.7-11.8v which I think is sufficient for you.