Hello friends! Today we will interface a PIR sensor with Arduino and build a motion indicator that reports when activity starts and when the sensor has been quiet for a selected time. We will begin with the sensing principle, connect the module, and then write a sketch that separates sensor startup, motion detection and the delay before switching an output off. Libraries PIR Sensor Simulation Libraries Latest library: PIR Sensor Library for Proteus V4.0 (October 2026): HC-SR501 with time delay, the H / L jumper, warm-up, Simple and Advance devices and an Arduino demo Other distance and motion sensors: Ultrasonic HC-SR04 · JSN-SR04T · Sharp IR · TF-Luna LiDAR · VL53L0X · RCWL-0516 · IR Obstacle FC-51 Helping Tools Serial Monitor Advance : a serial terminal window for the UART of your board ...