PIR

PIR
Name	Passive Infrared Sensor
Caption	Passive infrared sensor example
Invented	1950s
Inventor	William E. McMichael
Applications	Motion detection, surveillance, automation
Wavelength	8–14 µm

PIR

Passive infrared (PIR) devices are electronic sensors that detect infrared radiation emitted by warm bodies and objects, widely used for motion detection and presence sensing. They convert changes in long-wave infrared flux into electrical signals for triggering alarms, lights, or data logging in systems associated with building automation, security, and consumer electronics. PIR modules integrate optics, pyroelectric elements, and signal processing to discriminate transient events from background thermal emissions.

Overview

PIR technology uses pyroelectric materials to sense variations in thermal radiation from sources such as humans and animals within a field of view defined by optics like Fresnel lenses and mirrors. Typical assemblies include a sensing element, focusing optics, signal-conditioning circuitry, and mounting enclosures standardized by manufacturers such as Honeywell International Inc., Siemens AG, Bosch Security Systems, Panasonic Corporation, and Murata Manufacturing Co., Ltd.. Systems incorporating these sensors often interface with controllers from companies like Schneider Electric SE and Johnson Controls International plc for integration into larger installations, including smart building projects led by firms such as Google LLC and Amazon.com, Inc..

Types and Technologies

Multiple sensor types and configurations exist, including dual-element, quad-element, and pyroelectric arrays produced by suppliers like Excelitas Technologies, Vishay Intertechnology, TDK Corporation, and Texas Instruments Incorporated. Optical variations employ Fresnel lenses from manufacturers such as LG Innotek Co., Ltd. and mirrored concentrators used in CCTV modules by Hikvision Digital Technology Co., Ltd. and Dahua Technology Co., Ltd.. Advanced designs incorporate digital signal processors from NXP Semiconductors N.V., microcontrollers from STMicroelectronics N.V. and low-noise amplifiers from Analog Devices, Inc. to implement features like pet immunity and sensitivity zoning seen in products certified under standards from Underwriters Laboratories and International Electrotechnical Commission committees.

Applications

Common applications include intrusion detection in systems by ADT Inc., G4S plc, and Securitas AB; occupancy sensing for lighting control in projects by Philips Lighting (Signify) and Cree, Inc.; and environmental monitoring in research from institutions such as Massachusetts Institute of Technology and Stanford University. PIR modules are embedded in consumer devices from Apple Inc. and Samsung Electronics Co., Ltd., industrial IoT platforms by Siemens AG and GE Digital, and transportation projects by Siemens Mobility and Alstom SA. Emergency systems using these sensors are integrated into alarm networks following protocols by Zigbee Alliance, Thread Group, and Bluetooth Special Interest Group.

Design and Operation

A typical sensor element is a pyroelectric crystal such as lithium tantalate supplied by companies like Boston Electronics or ferroelectric ceramics from Kyocera Corporation mounted on a PCB designed with analog front-ends from Maxim Integrated Products, Inc. and filters from Murata Manufacturing Co., Ltd.. Optics such as multi-zone Fresnel lenses by Laird plc segment the field of view into zones to produce differential signals when heat sources cross zone boundaries. Signal processing employs filtering, automatic gain control, and pulse-count algorithms implemented on microcontrollers from Microchip Technology Inc. or digital signal controllers from Analog Devices, Inc. to reduce false alarms and to classify events for integration with access-control systems from HID Global.

Performance and Limitations

Performance metrics include detection range, angular coverage, time-to-trigger, and false alarm rate assessed in test labs like Underwriters Laboratories and research centers at National Institute of Standards and Technology. Environmental factors such as ambient temperature, wind, and radiative backgrounds from materials like asphalt or glass can degrade sensitivity; mitigation strategies reference publications from IEEE Standards Association and studies at Imperial College London and University of Cambridge. Limitations include inability to detect stationary thermal bodies, susceptibility to rapid temperature transients from HVAC systems, and occlusion by obstructions identified in field reports by National Fire Protection Association and case studies from Honeywell International Inc..

History and Development

Early pyroelectric detectors were developed by researchers such as William E. McMichael and commercialized in defense and industrial markets during the 1950s and 1960s, with military applications documented by organizations including Lockheed Martin Corporation and Raytheon Technologies Corporation. The miniaturization and cost reduction wave in the 1980s and 1990s involved semiconductor firms like Texas Instruments Incorporated and STMicroelectronics N.V., enabling mass-market consumer adoption by companies such as Philips Electronics N.V. and Panasonic Corporation. Recent improvements leverage machine learning and sensor fusion in projects by Google LLC's research groups and collaborations between MIT Media Lab and industry partners to enhance classification and reduce nuisance activations.

Category:Sensors