Maker Pro
Maker Pro

Car radio steering wheel controls


Mar 14, 2014
Mar 14, 2014
I never did well in my EE classes, I got Ds in them both semesters. Now I am doing projects of my own and love working on circuits outside of the classroom. I have designed and assembled my own solar system atop an Airstream trailer complete with MPPT, battery bank and sine wave inverter. I hard wired all of my electronic components to the 12v battery bank and use 12v to 5v cigarette lighter USB adapters for the smaller stuff and a 12v to 19v for my laptop charger and my mini projector.
I've really enjoyed it all and am always eager to learn more, but enough with introductions.

On to my current project:
I have a car radio that I want to add steering wheel controls to. Due to the limitations of the wiring harness and steering column limitations I can only use 2 wires to get to the steering wheel buttons. I have 4 physical buttons on the wheel itself which I want to be for volume up, volume down, track up, and track down. I know some aftermarket car stereo wired remotes use resistor networks and I wanted to use the same theory: have one wire going in and each button has a different resistor on it and the voltage drop on the other end of the wire will determine which button I pressed.
Based upon which button I pressed I want to close one of four switches. Each of these switches will close a circuit in the faceplate of the radio, acting just like I pressed a button on the faceplate itself.
Can this be done?

The buttons in the faceplate are all connected to an IC (PCF8574T). the faceplate connects to the radio via 6 contacts, is there a way I could use these contacts to utilize the functions I mentioned earlier(vol up, etc.)? From looking at the IC data sheet it looks to be digital, it seems to utilize a timing something or other (this is where I really get lost).

Any guidance here would be very much appreciated.
-Jeffrey Rossman