That is beautiful - simple, useful and elegant. I see you have :
duration = pulseIn(receiverPin, LOW);
So, does that mean the IR detector is normally HIGH and pulls LOW when IR is present?
I didn't see that mentioned in the docs.
Thanks! I go for simple whenever I can.
Yes, while the shutter is closed (no IR passed), my sensor is HIGH. I'm sure there's a circuit that would reverse that, but this is a circuit I found in two places so I went with it.