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. 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.
When a communication is to be established, that too wirelessly, with a remote device, we typically employ optical radiations or radio waves or sometimes, acoustic waves (for underwater applications). These three types of wireless communications basically differ in their frequencies. All frequencies starting from frequency bands like LF, HF, VHF, UHF and so on, extending up to microwaves and millimeter waves are referred to as radio waves. Acoustic waves use ultrasonic portion of frequency spectrum. Optical Radiations use visible and infrared portion of the spectrum. Infrared sensors have been widely utilized for remote based applications such as in televisions etc. This article will detail with a Passive Infrared Sensor.