What is PIR Sensing: A Complete Guide


A PIR (Passive Infrared) Sensor is an electronic device that detects infrared radiation emitted by warm objects, such as humans and animals, making it a great option for motion detection in security systems and automatic lighting.  

Definition and Functionality

A PIR Sensor is a type of motion detector that measures infrared (IR) light radiating from objects within its field of view. The term “passive” indicates that these sensors do not emit any energy; instead, they detect changes in the infrared radiation emitted by warm bodies. All objects above absolute zero emit heat energy in the form of infrared radiation which is not visible to the human eye but can be detected by PIR Sensors.

How PIR Sensing Works

PIR Sensor typically consists of two components: a pyroelectric detector and a Fresnel lens. The pyroelectric material generates an electrical signal when it absorbs infrared heat. When a warm body, like a person, moves through the sensor’s detection area, it causes a change in the infrared radiation detected by the detector. This change triggers the sensor to send a signal, which can activate alarms or lighting systems. The Detection Mechanism used in the sensor has two halves that detect infrared radiation. When a warm object passes by, one half detects the change in temperature before the other, creating a differential signal that indicates movement. The Fresnel lens is engineered to better gather and focus the infrared radiation onto the pyroelectric detectors of the sensor.

Applications and Uses

PIR sensors have found widespread application across numerous industries. Security systems rely heavily on PIR technology for intruder detection, while automatic lighting systems use them for energy conservation. Many home systems utilize PIR sensors from motion detections to trigger actions like turning on lights or sending alerts.

Major Tech offers a comprehensive range of PIR sensors to meet diverse application needs. Their product lineup includes over 12 different models each designed for specific use cases:

Indoor Lighting Control:

  • PIR32: 360° white sensor ideal for homes, offices, hotels, corridors, pathways, bathrooms, and lobbies
  • PIR31: 360° mini infrared motion sensor for compact installations
  • PIR33: 360° silver sensor variant for general indoor applications

Indoor/Outdoor Applications:

  • PIR34: 180° infrared motion sensor with IP44 rating, supporting up to 800W incandescent or 400W energy-saving lamps, with selectable LUX levels (3, 30, 300, 2000 LUX) and suitable for installation inside or outside under eaves

Outdoor Security:

  • PIR44: 180° outdoor sensor with IP65 rating, 12m detection range, and 0.5W power consumption with adjustable 3-2000 LUX sensitivity
  • PIR44B: Black variant of the PIR44 for aesthetic preferences

Extended Range Applications:

  • PIR45, PIR46: 360° sensor with dual sensitivity detectors and extended 20m – 30m detection range for large spaces like hallways or passages.

Advance Applications:

  • PIR42, PIR47, PIR49: Higher-end models for specialized commercial applications with the PIR42 and PIR47 featuring PIR based presence detection.

Security and Alarm Systems:

  • PIR43: 60° mini-PIR alarm sensor that functions as both annunciator and alarm, with compact design suitable for wall mounting or desktop placement, powered by 9V battery

The range also includes models PIR36, PIR37, and PIR41 for specialized applications, providing solutions for residential, educational, and commercial properties.

Advantages and Limitations

The primary advantages of PIR sensing include low power consumption, cost-effectiveness, and reliable motion detection. They operate effectively in darkness and don't require complex processing algorithms. However, PIR sensors have notable limitations. They cannot detect motion through glass, may struggle with very slow movements, and can be affected by temperature fluctuations, air currents, or small animals.

Conclusion

PIR sensing technology represents a simple solution for motion detection applications. Its passive operation, energy efficiency, and proven reliability make it an indispensable component in modern automation and security systems. Understanding its capabilities and limitations helps installers and consumers make informed decisions when implementing motion-sensing solutions.