HC-SR501 PIR MOTION SENSOR MODULE 

The HC-SR501 PIR Motion Sensor is a passive infrared sensor designed to detect motion from humans or animals by sensing changes in infrared (IR) radiation emitted by warm objects. Being a passive device, it does not emit energy but monitors natural IR radiation in its surroundings. Its simple operation and low power consumption make it ideal for security, automation, and smart home applications, as well as educational and DIY electronics projects.

The sensor module contains a PIR detector and signal processing circuitry. When a moving warm object enters or exits its detection field, the IR radiation pattern changes. The sensor detects this change and outputs a digital HIGH signal to indicate motion. Adjustable onboard potentiometers allow users to control both the sensitivity (detection range) and delay time (duration the output stays HIGH), providing flexible configuration for various applications.

Operating at 5–12 V DC, the HC-SR501 has a detection distance of approximately 3–7 meters (adjustable) and a field of view of up to 120 degrees. It supports repeatable or non-repeatable trigger modes, allowing it to respond continuously or once per motion event depending on the project requirement.

Common applications include motion-activated lighting, home security and alarm systems, automatic doors and switches, energy-saving controls, smart home automation, and robotics. Its compatibility with Arduino, ESP32, ESP8266, Raspberry Pi, and other microcontroller systems makes it a versatile sensor for real-time motion detection and interactive electronics projects.