![]() ![]() At least on my car (and every other car I've used a radio in), the switched line is usually cut upon starting the engine, and then restored when it is finished. One is switched (by ignition switch), and the other is constant. There are usually 2 +12V wires coming from the accessory cables. This is done so the Pi gets its 5v feed with as little connectors in the way as possible as each connector is a potential voltage drop, we all know how crap the micro usb connector is.ĮDIT also be aware of ancillaries, so if you say pug your pi into an aux in, is it getting spiked through a ground loop created between your audio output and the cars aux in? may be worth trying the pi with nothing plugged into it, just power, to see how it behaves. the Pi itself then controlls some relays to take care of startup and shutdown on the 12v side. I use this style in my OAP installation and find it surprisingly robust. If you have a scope this will be easier to see. ![]() I use a traditional "power probe 3" for this task but plenty of good meters have this function.Įither your supply is cut when cranking (as is common on non-essential circuits) or its browning out or, there is a voltage spike which the PI also hates.Īnd remember your ground point may be lifting up in potential, it isnt always just the 12v dropping down. Watch your 12v supply and ground (very important) when cranking, ideally with a meter that will capture min and max values as it'll catch transients you wont see on the gauge. ![]()
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