This is driving me insane. - I've tried a TIP31 (lights dimly) and an IRF730
Basically, I have a 12v rail, which goes to the collector (12+) 0 to ground, the circuit is fine, if i feed 12v directly from the rail, both transistors light up the 12v bulb... but, connect the 5v to the transistor, the tip31 glows (a little) and the IRF, does not even light up.
Surely, I can control a 12v source from 5v? without the need of a SSR/Relay ? (I want a 12v car bulb to switch on from 5v without using a relay, this seems futile)
(yes, the IRF has a pull down resistor to stop it from constantly being on, it works if the base gets 12v, if it gets 5v, nada!)
So i'm left wondering... Transistors ? in order to get the power flowing, you need the same voltage in and out? (eg 12v on base, 12v on collector vs 5v base, 12v collector)