Arduino PIR Motion Sensor Project

1. Introduction

Motion detection is a fundamental requirement in many embedded and IoT applications such as security systems, automatic lighting, energy management, and smart homes.In this project, we build a motion detection system using a PIR (Passive Infrared) sensor and Arduino. When motion is detected, the Arduino triggers an output (LED and serial alert).

This project is beginner-friendly, low-cost, and widely used in real-world systems.

2. How PIR Motion Sensor Works

A PIR sensor detects infrared radiation changes emitted by warm objects like humans or animals.

Key points:

• It does not emit radiation
• It senses changes in IR levels
• Best for detecting human movement
• Typical range: 3–7 meters

4. Circuit Diagram & Connections

5. Arduino Code

    int pirPin = 2;      // PIR sensor output pin
int ledPin = 13;    // LED pin
int motionState = 0;

void setup() {
  pinMode(pirPin, INPUT);
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
  Serial.println("PIR Motion Sensor Initialized");
}

void loop() {
  motionState = digitalRead(pirPin);

  if (motionState == HIGH) {
    digitalWrite(ledPin, HIGH);
    Serial.println("Motion Detected!");
    delay(1000);
  } else {
    digitalWrite(ledPin, LOW);
    Serial.println("No Motion");
    delay(500);
  }
}

6. Working Explanation

PIR sensor continuously monitors infrared changes.

When a human moves in front of the sensor

• Output pin goes HIGH
• Arduino detects motion
• LED turns ON
• Message displayed on Serial Monitor

When no motion is present:

• Output pin remains LOW
• LED stays OFF

7. Applications

• Home Security Systems
• Automatic Door Lights
• Smart Street Lighting
• Intruder Alarm Systems
• Energy Saving Systems
• IoT-based Surveillance

8. Calibration & Tips

• Allow 30–60 seconds warm-up time after powering the PIR sensor
• Adjust Sensitivity and Delay using onboard potentiometers
• Avoid placing near heat sources or direct sunlight

9. Future Improvements

• Integrate with buzzer or relay
• Send alerts via Wi-Fi (ESP8266/ESP32)
• Log motion data to cloud
• Add LCD/OLED display
• Combine with camera module

10. Conclusion

This project demonstrates a reliable and practical motion detection system using Arduino and a PIR sensor. It serves as a strong foundation for security, automation, and IoT applications and is well-suited for beginners and intermediate makers alike.