I am thinking of controlling my home appliances(fans)/lightings using a remote/computer/microcontroller. My main objective is power saving. Like as soon as someone leaves a room the lights & fans should turn off automatically. For this I have thought of 2 ideas.

1. Using PIR sensors in room, which detect human motion/presence. <<( I think this will be Costly as PIR sensor comes for Rs.950 each) http://www.roboticsindia.com/modules...ewtopic&t=3501

2. Checking whether someone has entered or left the room using laser/IR beam at the door(on the door frame). <<( But I dont know how this can be done as I need to exactly detect if person has gone in the room or come out of the room. Probably this can be done using two beams or one beam & two detectors. ) Also what if more number of persons go in the room.

Can someone please give me idea about this. Also tell me if there can be another technique for this?? :idea: