VARIOUS MOTION DETECTION SYSTEMS

Various types of sensing systems, viz., infrared, microwave and ultrasound devices, are employed to detect movement of human beings or objects; each having its own pros and cons, sensitivity and range being the important parameters.

 

Since microwaves can pass through dielectric materials, microwave sensors are effective in large apartments/buildings. But these sensors are relatively expensive and their radiation is unhealthy for living organisms.

 

Infrared sensors are characterized by high sensitivity, low cost and are widely used. But, these sensors can generate false alarm signals if heating systems are active or temperature change speed exceeds some threshold level.

 

Ultrasound motion detection sensors are characterized by small power consumption, higher cost (compared to PIRs), and high sensitivity and provide greater coverage than PIR detectors. However, increased sensitivity means that ultrasonic sensors are more susceptible to false triggering due to any movement in the space.

 

Handling false alarms is a challenge for all these motion detectors. PIR detectors use two elements in differential mode to cancel undesired air motions, vibrations, etc. Also, filters are used to limit the IR radiation. Ultrasonic & microwave detectors adjust the receiver’s gain to lower the sensitivity to false echoes. To reduce sensitivity to doppler generated due to movable parts of air conditioners, etc., filters are used to limit the frequency range to false alarm-free operations. However, in spite of all these precautions, it is not possible to avoid false alarms completely. For improved false alarm free performance, dual technology detectors are the solution. Though single detection systems may detect motions which are not there, any motion doesn’t go unnoticed by these detectors. Hence, occasional false alarms are not of very serious concern and therefore, they are used with their limitations.

 

TYPICAL APPLICATIONS

Motion sensing is used in number of applications, viz.

•           Automated lighting system

•           Occupancy Sensors

•           Vehicle Alert system

•           Smart Floodlights

•           Burglar Alarm

And many others.