Hey folks. I want to bypass a pushbutton switch on a garage door opener, i've seen a couple of circuits using a 2n3904 NPN transistor as a switch, and they had the external battery -ve tied to the GPIO GND pin - which makes sense. However the switch i want to bypass feeds 12v to a particular pin on the opener's microcontroller (and the other switches go to other pins) so i think i need to use a PNP, with the 3.3v GPIO pin tied to the external +ve 12v - and of course the GND on the pi and -ve will not be connected!
So i think i need the GPIO pin connected to a resistor (2.2k?) and then to the base of the transistor. The transistor emitter connected to the V+ side of the switch, and the collector connected to the low side of the switch. To make sure the signal gets through the +ve battery terminal will be connected to the GPIO 3.3v pin. Will this make my pi explode? I am far more rusty at electronics than i thought i would be!