Background: I’m working on an automotive project (controlling some lights using an Arduino Nano). It’s going great mostly, but I want to be able to read my high beam status to program in some logic to let me have a mode where the lights are all synced to the high beams so I can quickly turn everything off if a car is coming the other way.
Problem: the high beam wire that I have access to is on the ground side of the relay, because the car’s body control module grounds the relay to turn on the high beams. I need to step this down to 5V so the arduino can read it, but when I connect a voltage regulator to that wire to bring it down to 5V, I end up grounding the relay and turning on the high beams.
Is there a relatively simple way to read this wire with the Arduino without disrupting it but also without frying the Arduino pin?
I did find one somewhat related looking thread but I don’t see a definitive solution in it:
I’ve attached a simple diagram of the circuit in question with a wire coming off where I’m trying to read. I just need to be able to know with the arduino whether the switch is closed or not so I can act on it.