Motion Sensor technology

There are serveral types of technology that has been used in motion sensor such as

1 --> Passive Infra-red
2 --> Ultrasonic
3 --> Microwave

Passive Infra-red
Normally passive infra-red is looks for the body heat.

This picture shows that two girls in infrared

Ultrasonic
This technology it sends out pulses and detect the moving object.

Microwave
This technology is sends out microwave pulse and detect the moving object. It is similar to the police radar gun.





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http://wikipedia.org/wiki/Motion_detector