HC-SR501 PIR Human Motion Sensor

The HC-SR501 PIR Motion Sensor is a compact, low-cost, and reliable device that detects human or animal movement using passive infrared (PIR) technology. Ideal for security systems, automatic lighting, and IoT automation, it integrates easily with Arduino, Raspberry Pi, ESP32, and other microcontrollers.

How the HC-SR501 Works?

The sensor detects infrared radiation from warm bodies in its field of view. When motion is detected, the output goes HIGH (3.3V); when idle, it remains LOW (0V). Two operating modes are available:

• Repeatable (H): Output stays HIGH as long as motion continues. (Default)
• Non-Repeatable (L): Output pulses HIGH once per detection event.

You can select the mode by shorting the mode pins on the module.

Key Highlights

• Wide Detection Range: Up to 7 m distance with a 120° field of view.
• Adjustable: Onboard potentiometers for sensitivity and delay time.
• Low Power: Typical consumption around 65 mA, suitable for battery-powered projects.
• Flexible Supply: Operates from 4.5V–20V DC (5V recommended).
• Easy Integration: Works with Arduino, Raspberry Pi, ESP8266/ESP32, and other MCUs.

Pin Configuration

Pin No.	Pin Name	Description
1	Vcc	Power input (4.5V–20V DC, 5V recommended)
2	Dout	Digital output: HIGH (3.3V) on motion, LOW (0V) when idle
3	GND	Ground

Technical Specifications

• Detection Angle: 120°
• Detection Distance: ~3–7 m (adjustable)
• Output Level: 3.3V TTL (HIGH) / 0V (LOW)
• Operating Voltage: 4.5V–20V DC (5V typical)
• Power Consumption: ~65 mA
• Operating Temperature: -20°C to +80°C
• Modes: Repeatable (H) and Non-Repeatable (L)

Applications

• Motion-activated LED lighting and energy saving controls
• Home and industrial security alarms
• Automatic doors, gates, and pathways
• IoT/Smart home automation and occupancy sensing
• Pet/wildlife monitoring and presence detection

Usage Tips

• After power-up, allow about 1–2 minutes for sensor calibration.
• Use the two orange potentiometers to fine-tune delay and sensitivity.
• Avoid pointing directly at heating/cooling vents or windows to reduce false triggers.