What’s passive PIR detector?
Passive Infrared (PIR) sensor is a type of device that detects infrared radiation, primarily used to sense the heat emitted by objects. It works by detecting changes in infrared radiation, especially from moving objects like humans or animals, which emit heat.
Infrared is an electromagnetic wave with a wavelength between microwaves and visible light, ranging from 760 nanometers (nm) to 1 millimeter (mm). Invisible light longer than red light and materials above absolute zero (-273.15℃) can produce infrared rays. Modern physics calls it heat rays.
The basic concept of infrared detection of passive infrared detectors is to sense the temperature difference between moving objects and background objects. In the warning area of the passive infrared detector, when there is no human movement, the pyroelectric infrared sensor senses only the background temperature. When the human body enters the warning area, the infrared rays of about 10 microns emitted by the human body are enhanced by the Fresnel lens and gathered on the pyroelectric infrared sensor. The pyroelectric element in the pyroelectric infrared senses the difference between the human body temperature and the background temperature, the temperature changes, the charge balance is lost, and the charge is released outward. After subsequent circuit detection and processing, an alarm signal is generated.
The principle of passive infrared detectors
The principle of passive infrared detectors is that there is a difference between the surface temperature of the human body and the surrounding environment temperature. When the human body moves, the changes caused by this difference can be detected by infrared sensitive elements, thereby triggering an alarm. Moreover, in order to prevent false alarms, the passive infrared detector divides the detection coverage into a certain number of detection zones through a Fresnel lens. When a temperature change occurs between two zones, the detector circuit triggers a signal pulse, and the detector triggers an alarm output based on the signal pulse.
how it works:
- Infrared Radiation: All objects with a temperature emit infrared radiation. Humans and animals, due to their body heat, emit more infrared radiation than the surrounding environment.
- Sensor Components: The PIR sensor is designed to detect specific wavelengths of infrared radiation. When it detects a change in this radiation, usually caused by movement, it assumes there is an object in motion.
- Signal Processing: The sensor converts the detected infrared radiation into an electrical signal. If it senses a change in the infrared levels, it triggers a response, such as setting off an alarm or turning on lights.
Applications:
- Security and burglar alarm systems
- Smart lighting controls
- Automatic door systems
- Indoor and outdoor motion detection
The PIR sensor’s advantages include low power consumption, cost-effectiveness, fast response, and the fact that it doesn’t emit any signal, so it doesn’t interfere with the environment.
