I'm really new to this as well.. i'm trying to light up a 2 AAA LED christmas light and to replace it, i found an old unused 110VAC to 5VDC cell phone adapter...replacing the receptacles on the base of the tree, was simple, and when i turned it on, it worked! about 40 minutes later, the LED popped, assuming 5 volts was too much for it to handle... reading up on it. i could use ohm's law to get a resistor that could reduce it to 3v (at the cost of heating up).. is that conventional? or would it be probably better to just find a 3VDC adapter?