How do Infrared Wireless Motion Sensors Work?
Wireless motion sensors are designed to detect rapid motion in a specific area around them. These motion sensors detect movement through detection of rapid changes in infrared radiation incident on them. There are certain crystalline materials that show pyroelectric effect. That is, when heat in the form of infrared radiation is incident on them, they generate a current on their surface. These crystals are very sensitive to small changes in infrared radiation and therefore the current they generate changes accordingly. Such crystalline material wafers are used as thermal sensors. Every object which has a quantity of heat, radiates infrared radiation. The human body emits infrared radiation which is around 9.4 micrometer wavelength. Motion of a human body therefore creates changes in the local infrared radiation pattern in the vicinity of the sensor. The incident infrared radiation is focused on the sensor by a ‘Fresnel lens’, which is made up of a material that is transparent to radiat