I would like to configure mr Raspberry in order to receive an email when the main gate opens.
I have signal coming from the gate, when the gate is open the signal is 12VCD, when the gate is closed there is no signal.
My doubt is simple, my signal is made of a DC voltage, plus and ground. Each input channel just has one pin.
I can not just connect the plus of the signal coming to the gate two one input channel because there should be the same voltage reference. The reading would not be accurate.
What could I do?