I'm using this circuit to detect if a car engine is running. I tested it and it is working however there is some kind of a problem where in my code (running raspberry pi) I see a lot of interrupts regardless of whether the output is high or low. I don't have a scope to tell an exact number but by eyeballing it I can say it's well above the hundreds if not thousands of hertz. My pi blew up like 10 to 15 minutes in after I hooked this part of the circuit and I'm guessing this has something to do with it. Then again there's always the possibility I accidentally shorted something but I'd be thankful if someone with a better understanding can have a look at this before I blow up another Pi.