PIR Sensors are also known as Passive Infrared Sensors. They are constructed from an array of solid-state sensors made from pyroelectric materials that generate a voltage when exposed to heat. They are used in thermal sensing applications, including security sensors and motion detectors.

13.5pt;">The devices work because thermal changes modify the crystalline structure of the polar crystals of a material. The associated stress and strain generates a voltage. They are typically around ¼ inch square and are a flat film. They may incorporate some focusing mechanism to capture and direct infrared radiation to the film surface. This is commonly a plastic window with many Fresnel facets that combine to form a lens to suit the application.Differential detection (detecting changes or differences from an ambient reading) can be used as motion detectors, and this makes them very suitable for burglar alarm sensors. They can have a variety of sensitivities usually expressed as a sensing distance and can be either component mounted on a PCB or a whole mechanically enclosed module. They may have a manually adjustable trigger point, or be configurable using a logic interface (for example a serial port). They may also have a single trigger output that may be in open drain or open collector configuration to enable many PID Detectors to be placed in parallel with each other. Continua a leggere Meno informazioni