A Passive Infrared sensor is defined as an electrical sensor that detects the infrared light radiated by a warm object or used to sense motion. It is widely used to detect the motion of a human body within the sensor’s range. Hence often referred to as “PIR”, “Pyroelectric”, “Passive Infrared” and “IR Motion” sensor.
The module consists of an onboard pyroelectric sensor, conditioning circuitry, and a dome-shaped Fresnel lens. In addition to it, it consists of a delay time adjustment Potentiometer and sensitivity adjustment Potentiometer. These pyroelectric sensors introduce changes in their temperature due to incident infrared radiation into an electric signal. But there will be no change in the detection distance. In order to lengthen the detection distance of the detector, an optical system was added to collect the infrared radiation. Usually, a plastic optical reflection system or plastic Fresnel lens is used as a focusing system for infrared radiation. These small, inexpensive, low-power sensors can be easily interfaced with ARDUINO, RASPBERRY PI, AVR, PIC, 8051, etc.
PIR sensor senses infrared energy emits the human body within a detection area of approximately 3-7 meters. When the human body moves within the detection range at a certain field of view in sequence and then walks out of the field of view. As a result, the pyroelectric sensor senses the moving human body for a while and then does not see it, so the infrared radiation of the human body constantly changes the temperature of the pyroelectric material. Thus outputs a corresponding signal, which is the alarm signal. This sensor offers a wide range of applications in burglar alarms and automatically-activated lighting systems etc.