The "LightMinder"

We've all been frustrated with ourselves and others when it comes to the task of keeping those darn unused light bulbs off.  In cases where there is always frequent motion (like in a bathroom) motion sensors work great but, as the name implies, if there's no motion for a while, the lights go out. 

Instead of monitoring motion, the LightMinder is mounted on a door frame and connected to the associated light switch going into a room. It is able to count the people coming in and out of the room turning the light on and off as appropriate. It does this with an arrangement of infrared LEDs and detectors controlled and read by a tiny micro-controller.  The micro-controller has been
programed to intelligently use the information from the detectors to detect and filter out unwanted events such as those from hands and feet and other objects that also might block the entrance to the room. We've found, by using the prototype for several months now, that the mistakes it makes are rare and just a press of the reset button and all is well again.

The LightMinder consists of three parts. One is a circuit board that can be bolted on to a standard light switch using the switches existing terminals and contains the power supply and the devices that actually switch the power to the lights. Two other modules are mounted opposing each other on the opposite sides of the the door. The one closest to the switch contains the microcontroller and detectors while the other just the LEDs.