For a vehicle simulator project, I want to use an Arduino to read input from an existing light switch in a (unpowered) car. At the same time, a collaborator who is preparing the car itself, would like the button to send a 12V signal to be read by the existing light-controller which in turn activates the real car lights.
Other than having completed the very basic Arduino tutorials, I’m an absolute beginner in electronics in general. I’ve attached a naive diagram of the situation, which would probably fry the arduino. So my two specifiq question to this situation are:
Question 1: is it reasonable to power the Adruino with a 12V power supply and use VIN pin as a source for the 12V signal?
Question 2: what are ways to convert the 12V signal to a safe 5V signal for the Arduino? Or would it make more sense to somehow stretch a 5V signal on the way to the light controller?
It would be great if you could help me on how to approach this. Thanks!