I have some ideas for a rear facing camera, AI, and communication servers I would like to add to my car ( a 2006 ford focus). I can handle all of that set up, what I have no idea about is the power coming into the system via the wire harness where the stereo would have been. Are car stereos standardized in any way? what voltages, and currents would I have? I need about 7 watts, at 5vdc for the operation of a Raspberry Pi (small computer). If there is a +5V source, is that stable? (or should I build a noise filter, and anti hysteresis circuit protection?)

I am looking for detail on the power supply of a ford focus stereo adapter. I am not looking to retain the adapter to power the stereo.

  • 1
    Whatever solution you pick: Please do not forget to attach a fuse
    – Martin
    Mar 19, 2017 at 11:02
  • 1
    If you're taking over the stereo circuit there will probably already be a fuse.
    – dlu
    Mar 20, 2017 at 1:20

4 Answers 4


Cars are standardized with an electrical system voltage that will be in the range of 12 to 14 V DC depending on the whether or not the engine is running. To power the Pi you'll need to provide a regulated source. Current (power) wise you'll be fine, the stereo probably had its own fuse and you can find the value of the fuse either in the owner's manual or by looking at the fuse itself. I'd expect it to be 5 to 10 A.

You could build a power supply or use something like this 12 V to 5 V DC-DC converter from Adafruit, it will provide 3A at 5V.

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12vdc +/- should be in the range which will be available to your electronics ... vehicle voltage will vary, though, so the electronics will account for this and ensure there's no issues with over/under voltage. A normal system runs about 12.5-14.5vdc, so you may want to ensure the systems you are adding can handle this.


I'd probably install a normal 12v cigarette style outlet with a fuse near where you want the raspberry pi. Then you can buy a cell phone charger to plug in the raspberry pi.


The wiring harness for the radio terminates in a proprietary Ford connector which will have 2 x 12V terminals (one with continuous power, and one switched with the ignition). The switched terminal is usually rated at 15A or thereabouts.

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