I've tried to get the relay working and can't even seem to do that. This is the instructable, which I'm trying to do.
I understand that I have a 12v relay, which means I need a way to send more current through to the relay than the arduino 5v can provide. so I tried the smaller transistors (bc5478) in the arduino starter kit, along with one diode that also came with the kit. I thought the transistor had enough juice to activate the relay, but when I put a multimeter to it, it switches between 7 and 9v.
I should also mention I have a 9v battery connected to the relay which should power the pump.
Conceptually, am I doing anything wrong? Maybe I just hooked it up incorrectly?