Using a transistor as a switch

Discussion in 'The Projects Forum' started by JRMN, Mar 18, 2011.

  1. JRMN

    Thread Starter New Member

    Feb 17, 2011
    I’m working on an arduino project that would allow me to control my aftermarket car radio using my car steering wheel controls. I believe the aftermarket radio has a resistor divider built-in because there is a constant 3v coming from the two remote wires and I was able to control the radio by place resistors between ground and each of the two remote wires. Only one of the wires actually controls the mode function. The other wire controls vol. up, up, down and vol. down.


    I know that NPN transistors are activated by positive voltage on the base relative to the emitter. So in my sketch I setup one of the digital pins on the arduino as digital output. Digital output causes the voltage on that pin to be either HIGH (5v) or LOW (0v). For testing purpose, I wired everything up with a push button that set the base HIGH. The collector is connected to one of the remote wires and the emitter is connected to ground. In theory this should work, but for some reason it’s not working.

    I’ve even hooked up my multimeter by connecting positive probe to the collector and the negative probe up to the emitter. I do get a voltage reading, but I believe that’s from the arduino when the output pin is set to HIGH.

    Anyone has any suggestion? What am I missing?