Build Yourself A Motion-Sensitive Hidden Camera
“Ever wondered what your cat gets up to when you leave each day for work? Or have a sneaking suspicion that your roommate has been going into your room when he’s not supposed to? We can use an Arduino and a pretty simple assemblage of supplies to create a camera trap to try to catch them in the act.
To do this, we’ll use an infrared emitter and phototransistor detector. When the line of sight between the two is broken and re-established, it will signal the camera to snap a picture.”