The HC-SR501 PIR Motion Sensor Module is a highly reliable, low-cost passive infrared sensor designed to detect human or animal movement by measuring changes in infrared heat signatures. Operating on a flexible 4.5V to 20V DC input, this compact green board features a Fresnel lens cap to maximize detection range along with dual onboard potentiometers to easily adjust sensitivity and time delay. It is an essential component for building automated lighting, smart home systems, robotics, and custom DIY security alarms with microcontrollers like Arduino and Raspberry Pi.