The term ‘Motion detectors’ can be used to refer to any kind of sensing system which is used to detect motions; motion of any object or motion of human beings. However, it is primarily used to detect motion of human beings or in other words, presence of a body in a certain area. A motion detector is an electronic device that detects the physical movement in a given area/ designated locations and it transforms motion into an electric signal.
Applications to detect motion do so by either:
• Generating some stimulus and sensing its reflection.
• Sensing some signals generated by an object.
All motion sensors indicate the same thing; that some condition has changed. All sensors have some 'normal' state. Some sensors only report when the 'normal' status is disturbed, others also report when the condition reverts to 'normal'.
Motion sensors are commonly used in security systems as triggers for automatic lights or trips for remote alarms and similar applications. Motion sensors work based on a wide variety of principles and is used in a wide variety of applications. Typical usage could be in the exterior doorways or windows of a building for monitoring the area around the building. Upon detecting motion, they generate an electrical signal based on which some actions are taken. Some operate in much the same way as a military radar scanner, while others work based upon vibration, infrared radiation and even sound. All of these different types of motion sensors have different strengths and weaknesses, which are important to take into account when making a decision to choose a particle motion detection sensor.
TYPES OF MOTION SENSING
Motion sensors are employed to detect different types of human movement. Some are intended for local event sensing, some for area sensing
• Local Sensing
Local Sensing implies sensing of a motion at designated locations. Some of the motion sensors commonly used for this purpose are
o Visible/ Infrared light(LED/Laser) beam
o Contact Switch
o Piezoelectric Sensors
o Piezoresistive Sensors, etc.
• Area Sensing
Area Sensing implies sensing of a motion in a specific ‘Field of View (FOV)’. Motion sensors commonly employed for such application are
o Active/ Passive Infrared Motion Detector
o Ultrasound motion detection sensor
o Footstep Detection Sensing
o Microwave Doppler sensor