Passive Infrared Sensor

Passive infrared sensors are infrared sensors that do not need to actively emit infrared light, but only detect by receiving infrared energy radiated by the object itself. PIR sensors are usually used to detect the movement of heat sources such as humans or animals, so they are widely used in security, automatic lighting, smart home and other scenarios.

Working Principle

The passive infrared sensor contains pyroelectric materials inside, which can sense thermal radiation in the infrared band. When a heat source (such as a human body) moves in the sensing area, it will cause an imbalance in the infrared energy at both ends of the receiver, thereby outputting a signal. In order to achieve angle detection, a Fresnel lens is usually installed in front of the sensor to focus infrared signals from different directions to the pyroelectric element, thereby enhancing the sensing sensitivity and angle range.

Main Features

• Low power consumption: Suitable for battery-powered devices.
• No light-emitting elements are required: Relying on external infrared radiation, stable and reliable.
• Sensitive to the movement of heat sources: Can effectively sense temperature difference targets such as human bodies.
• Strong anti-interference ability: Strong adaptability to environmental changes such as light and dust.
• Wide angle and long distance: The coverage range can usually reach 120° and more than 10 meters.

Advantages

• No signal is emitted, more concealed and safe.
• Fast response speed, suitable for real-time detection.
• Low cost, suitable for large-scale applications.\
• Modular design facilitates integration in various devices.

Application Scenarios

Passive infrared sensors are widely used in daily life and industrial scenarios. They are often used in intelligent lighting systems to realize human body sensing automatic light on and off. In the security field, they are used for intrusion detection and alarm devices. They are also integrated into smart home devices to realize functions such as automatic curtains and air conditioning linkage control. In addition, passive infrared sensors are also used in automatic access control systems, public area energy-saving control, intelligent monitoring terminals, etc., and realize non-contact, low-power, and high-reliability automatic control by sensing changes in human body thermal radiation.