Solid State relays are a great way to control high current ON/OFF applications like strings of LEDs. Easily controlled from the RoboRio digital output, these inexpensive SPST N.O. SSR6M solid state relays can handle up to 12A of current for any 3 to 200VDC load. They even include thermal mounting pads. Be sure to check out their SCR and TRIAC cousins for controlling AC loads in your side projects!