What is a PIR Sensor? - ECEdreamTeam/GroupProject GitHub Wiki

A Pyroelectric Infrared Sensor (PIR), also known as a Passive Infrared Sensor, is designed to detect heat radiation so motion can be detected. These are used because they are small, inexpensive (they cost about $10), and they require low power. An additional bonus is they are easy to use and they do not wear out easily. Many are used in embedded systems designed to keep people safer, such as a security system, or to make people’s lives easier, such as an automation of lights or doors. They can also be used in consumer electronics, such as items with touch screens.

Everything emits radiation, the hotter something is, the more radiation something emits. The point of the PIR sensor is to detect changes in the Infrared levels, not the static infrared level, such as the sensor OMRON D6T8L06. I bought this PIR sensor for $10 off of Adafruit.com. This PIR sensor has a detection range for up to 20 feet or 6 meters at an angle of 110 degrees. After that the accuracy decreases.

The sensing element is the RE 200B. It can detect levels of infrared radiation of wavelengths in a band around 10 microns. It operates the best at a temperature of -20 ˚C to +70 ˚C and with a voltage between 3 and 10 V. There are two parts to the sensor, designed to cancel each other out. When a heat source hits one part of the sensor, it causes a change in the two parts. An output that is high. When the heat source leaves the area, it causes the two parts of the sensor to revert back to the same (low). This is what the sensor reads and how it can tell if there is motion detected.