Motion detector sensor light switch 

circuit Diagram===tinyurl.com/y2x...
A motion sensor light switch is great way of saving energy short fall period. A PIR sensor light switch will automatically detects when someone enter the room or any place where motion sensor is set. Then, after a few minutes(adjusted by your desires) where no movement has been detected, the lights will then automatically turned off. Although a motion sensor switch is indeed a big and important invention . In fact, you can install a motion sensor light switch much in the same way as you would a single pole light switch.