![]() ![]() This PIR sensor itself is pretty straightforward and works out of the box. It is low power, low cost, easy to interface and extremely popular among hobbyists. A special lens called a fresnel lens which Focuses the infrared signals on the pyroelectric sensor.įor most of our Arduino projects that require detecting whether someone has left or entered the area, the HC-SR501 PIR sensor is a great choice.A pyroelectric sensor, which you can see in the image below as a round metal with a rectangular crystal in the center.The PIR sensor is specifically designed to detect such levels of infrared radiation. This radiation is not visible to the human eye because it is emitted at infrared wavelengths. The hotter an object is, the more radiation it emits. How does a PIR sensor work?Īll objects, including the human body, at temperatures above absolute zero (0 Kelvin / -273.15 ☌) emit heat energy in the form of infrared radiation. This sensor is what you’ll find in most modern security systems, automatic light switches, garage door openers and similar applications where we want to react to motion.īefore getting into the nitty-gritty, let’s first understand how a PIR sensor actually works. ![]() ![]() The PIR sensor allows you to detect when a person or animal moves in or out of sensor range. Whether you want to build a home burglar alarm or a trail camera, or perhaps you want to wake up animated Halloween props when trick-or-treaters come to your door, then you should definitely consider getting an HC-SR501 Passive Infrared (PIR) sensor for yourself.
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