PIR SENSOR: Every living object emits thermal radiation. Infrared radiation depending upon the temperature of the body, which is detected by the sensor. Suppose a sensor initially faces something when a human body passes in front of it. Its temperature rises and then drops as the body temperature is higher than room temperature. This phenomenon produces a change in the output voltage which in turns make the output High or Low.
WORKING OF PIR SENSOR: The most widely used infrared detector is a pyroelectric detector, which is able to detect different levels of infrared radiation. The detector itself does not emit any energy but passively receives it, so it is called Passive Infrared Sensor. It uses as a sensor for converting human infrared radiation into electricity. In order to lengthen the detection distance of the detector, an optical system is added. plastic Fresnel lens used as a focusing system for infrared radiation.
Passive Infrared Sensor or PIR sensors allow us to sense motion, almost always used to detect whether a human has moved in or out of the sensors range. Out of the three terminal of the device 1) one is used to get Output and other two terminal are used to provide + 5 volt (Vcc) and Ground respectively.
Output terminal produce a high or low value in accordance with the movement of human body. If there is any motion of human body output terminal goes HIGH otherwise output of PIR sensor remain LOW.
The two potentiometers present in the PIR circuit board, 1) Delay Time Adjust allow us to control the delay i.e. how much time the output will be high after some motion is detected, we normally adjust this to the lowest possible. and the 2) Sensitivity Adjust the how far away from the sensor is possible to detect motion.
Infrared (IR) Sensor
An infrared (IR) sensor is a powerful device that detects and measures infrared radiation emitted by objects. It operates on the principle that every object emits thermal radiation based on its temperature. The IR sensor is capable of detecting this radiation and converting it into an electrical signal, allowing us to sense the presence or movement of objects or living beings. These sensors are commonly used in various applications such as security systems, automatic doors, motion-activated lighting, temperature measurement, and even in remote controls. With their ability to detect and interpret infrared radiation, IR sensors have become an integral part of many technological advancements, making our lives more convenient and efficient.