PIR (Passive Infrared) sensors are essential devices used to detect motion, particularly human movement, within a specific range. These sensors are small, cost-effective, and energy-efficient, making them ideal for a wide array of applications in homes, businesses, and security systems. Commonly referred to as “Pyroelectric” or “IR motion” sensors, PIRs are integral components in devices designed to sense whether a person has entered or exited the sensor’s detection area.

At the core of a PIR sensor is a pyroelectric sensor, which is typically housed in a round metal can with a rectangular crystal at its center. This sensor is highly sensitive to infrared radiation, which is emitted by all objects to varying degrees. The level of radiation increases with the object’s temperature, making PIR sensors particularly effective at detecting warm-bodied entities like humans.

The sensor is split into two halves, a design that is crucial for motion detection. This split allows the sensor to differentiate between average infrared levels and changes in the environment. When one half of the sensor detects a difference in infrared radiation compared to the other half, the sensor’s output shifts, indicating movement. This mechanism ensures that PIR sensors are both accurate and reliable in detecting motion, making them indispensable in automated systems and security applications.