Week 4 - Research

MOTION DETECTOR

+ A motion detector is a device that contains a physical mechanism or electronic sensor that quantifies motion that can be either integrated with or connected to other devices that alert the user of the presence of a moving object within the field of view.

+ An electronic motion detector contains a motion sensor that transforms the detection of motion into an electric signal. This can be achieved by measuring optical or acoustical changes in the field of view. Most motion detectors can detect up to 15–25 meters (50–80 feet).

+ A motion detector may be connected to a burglar alarm that is used to alert the home owner or security service after it detects motion. Such a detector may also trigger a red light camera or outdoor lighting.

+ An occupancy sensor is a motion detector that is integrated with a timing device. It senses when motion has stopped for a specified time period in order to trigger a light extinguishing signal. These devices prevent illumination of unoccupied spaces like public toilet. They are widely used for security purposes.

SENSORS

+ Passive infrared sensors (PIR): Looks for body heat. No energy is emitted from the sensor.

+ Ultrasonic (active): Sends out pulses and measures the reflection off a moving object.

Microwave (active): Sensors sends out microwave pulses and measures the reflection off a moving object. Similar to a police radar gun.

reference: http://en.wikipedia.org/wiki/Motion_detector