Parenting is a long period of anxiety punctuated by moments of sheer terror. Among those periods of anxiety is babyhood. "Is my child breathing right now?" is a question that keeps parents up at time at times.
YouTube user Gjoc31 found a helpful way of dealing with that fear. He rigged a system that shines lasers on the back of his baby's back. If the baby stops moving, the system triggers an alarm:
Unlike similar builds and products that rely on microphones or capacitive sensors, [Gjoci]‘s build uses the camera from a wiimote to triangulate points of light and detect motion.
The build started off with infrared LEDs, but the batteries were big and there is always the possibility of the baby swallowing electrical components. [Gjoci] finally hit upon the idea of using small 1mW laser diodes to project points of light. This worked beautifully, and since newborns don’t move much there’s no danger of shining a laser into a baby’s eye.
The rest of the build is just querying the camera every few milliseconds and seeing if the position of the reflections captured by the wiimote camera have changed. In two weeks of operation, [Gjoci] only had to respond to a few false alarms, and the hardware hasn’t crashed at all.