The BOM on [Jeremy S Cook]’s build is extremely short – just a PIR sensor and an optoisolator, with a battery, a plug for the camera’s remote jack, and a 3D-printed bracket. The PIR sensor ...

When a person walks past the sensor, it detects a rapid change of infrared energy and sends a signal. PIR sensors are used for applications such as automatically turning on lights when someone ...

If you didn’t say with a 3D printed iris mechanism and high-voltage ... while everyone else gets the business end of a spark gap if the PIR sensor detects them getting to close.