I would like to connect the garage door's button to a GPIO input on my Pi. I want to be able to trigger actions when someone pushes the button. I am able to read the status of a basic switch using this circuit I found:
My concern is that when I connect a volt meter across the garage door button I see over 16 volts (presumably to drive the LED in the button?). I am concerned that if I connect my switch reading GPIO input circuit to the button, that 16 volts could fry my Pi. How can I read whether the button is open or closed, but protect my Pi from the voltage on the line?
I do also have a garage door magnetic switch sensor that works great, but my requirements include knowing when the button is pushed- not just whether the door is open or closed.