Overview of Motion Detectors
– Motion detectors are used in various commercial applications, such as activating automatic door openers and controlling smart lighting systems.
– They are also used in burglar alarms to detect possible intruders and trigger security cameras.
– Specialized motion detection systems can cover larger areas by using radio waves that penetrate walls and obstructions.
– Most low-cost motion detectors have a range of about 4.6 meters (15ft).
– Tomographic motion detection systems can detect motion over large areas by sensing disturbances in radio waves.
Sensor Technology
– Passive infrared (PIR) sensors detect infrared radiation emitted by a person’s skin temperature.
– Microwave sensors use Doppler radar to detect motion by analyzing phase shifts in reflected microwaves.
– Ultrasonic sensors emit and receive ultrasonic waves to detect nearby objects and motion.
– Tomographic motion detectors use a mesh network to sense disturbances in radio waves.
– Video camera software can be used to detect motion in the field of view of a camera.
Passive Infrared (PIR) Sensors
– PIR sensors detect infrared radiation emitted by a person’s skin temperature.
– They can distinguish between objects, people, or animals based on their infrared radiation.
– PIR sensors do not emit any energy themselves.
– They are different from electric eye motion detectors that use visible or infrared beams.
– PIR sensors are commonly used in household motion sensing devices.
Microwave Sensors
– Microwave sensors use Doppler radar to detect motion.
– They emit a continuous wave of microwave radiation.
– Motion of an object toward or away from the receiver causes phase shifts in the reflected microwaves.
– These phase shifts result in a heterodyne signal at a low audio frequency.
– Microwave motion detectors are similar to radar speed guns.
Ultrasonic Sensors
– Ultrasonic sensors emit and receive ultrasonic waves to detect motion.
– They work similar to Doppler radar but at higher frequencies.
– Heterodyne detection of the received ultrasonic waves indicates motion.
– Ultrasonic sensors have a potential drawback of being sensitive to motion in undesired areas due to sound wave reflections.
– They are commonly used in gesture detection and can support digital screens.Sources: https://en.wikipedia.org/wiki/Motion_detector
