Introduction

The HC-SR501 PIR Motion Sensor is a pyroelectric infrared sensor that detects movement by measuring changes in infrared radiation. Widely used in security systems, automatic lighting, and energy-saving applications, this module offers adjustable sensitivity and detection range.

Key Features

Technical Specifications

Pin Configuration

Pin	Label	Description	Arduino Connection
1	VCC	Power (5V recommended)	5V
2	OUT	Digital Output (High when motion detected)	D2
3	GND	Ground	GND

Wiring with Arduino

// Basic Connections:
// VCC → 5V
// GND → GND
// OUT → D2 (digital input)

// For best results, mount sensor 2-3 meters above ground

Basic Detection Example

// HC-SR501 PIR Motion Sensor Basic Example
const int pirPin = 2; // OUT pin connected to D2

void setup() {
  Serial.begin(9600);
  pinMode(pirPin, INPUT);
  Serial.println("PIR Sensor Initializing...");
  delay(60000); // 60s initialization period
  Serial.println("Sensor Ready");
}

void loop() {
  if(digitalRead(pirPin) {
    Serial.println("Motion detected!");
    delay(1000); // Prevent multiple detections
  }
}

Advanced Features

// Low-power monitoring with interrupt
void setup() {
  attachInterrupt(digitalPinToInterrupt(2), motionDetected, RISING);
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
}

void motionDetected() {
  // Wake up and handle motion
}

Troubleshooting