I've been having this problem where I can't be bothered to turn on and off lights when I enter and exit rooms. For some reason this seems to bother my significant other.

So I propose a system of infra-red sensor's placed at waist height at entrances to rooms that automatically switch lights on and off based on a count of how many people are in the room. 0 people => turn the lights off. 1 or more people => turn the lights on.

It would detect if a person has left or entered the room based on two parallel side by side infra-red beams. Based on which beam was interrupted first you could detect if the person was entering or leaving the room.

All of this information would be transmitted wirelessly (or through the power lines) to the modified light switches with the ability to enable or disable this functionality based on a user's preference. Of course these light switches would also work in the traditional manner.
-- TXP, Jan 21 2005

indoor lighting controls http://www.dulley.com/docs/f479.htm
with motion sensors instead of people counting [FarmerJohn, Jan 21 2005]

You'd run into problems when two or more people pass the sensor at the same time. Or if little kids start playing with it. A more reliable way would be to have an infrared camera that detects how many human heat signatures are in the room. [+]
-- Aq_Bi, Jan 21 2005



random, halfbakery