Project 24: PIR Motion

Introduction

The PIR (Passive Infrared) sensor detects motion by sensing changes in infrared radiation.
It outputs a digital HIGH signal when motion is detected and LOW when idle.
Commonly used in security systems, motion-activated lights, and automation projects.
In this tutorial, we’ll connect a PIR sensor to an Arduino and detect motion events.

Required Components

• Arduino UNO
• PIR Motion Sensor
• Jumper wires
• Breadboard (optional)

Pinout

Circuit Diagram / Wiring

• PIR VCC → 5V (Arduino)
• PIR GND → GND (Arduino)
• PIR OUT → D2 (Arduino)

Arduino Code / Programming

#define PIR_Pin 2
 
void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT);
}
void loop() {
  int val = digitalRead(2);
  if (val == HIGH) {
    Serial.println("Motion Detected");
  } else {
    Serial.println("No motion detected.");
  }
  delay(1000);
}

Explanation

• The PIR sensor is connected to pin 2 and read using digitalRead().
• When motion is detected (HIGH), “Motion Detected” is printed to the Serial Monitor.
• When idle (LOW), it prints “No motion detected” every second.

Testing and Troubleshooting

• Move your hand in front of the PIR sensor and check for “Motion Detected” on the Serial Monitor.
• If it always shows “No motion,” check power (VCC = 5V) and ensure sensor’s output is connected to pin 2.
• Adjust the sensor’s sensitivity and delay potentiometers if detection is inconsistent.