A microcontroller in another circuit I want to monitor controls a relay.
I had thought of using a current switch to detect when the switch had been made, but because it's got a cord and doesn't expose enough of the active wire inside, I won't be able to.
However what might work is the other side of the relay, I can connect to the signal side of the relay, and that would work - however, slightly lost on how to interface the relay to the Arduino ?
Connect both grounds together, use a digital input and if it's on, that is it? Will that cause any problems with the relay coil if connected from the active side to the relay, and the ground being common ?