How to Detect Movement with a PIR Sensor

In this tutorial, you will learn how to detect movement with a PIR sensor and an Arduino.

Parts Required

• Arduino
• PIR Motion HC-SR501 Sensor
• LED
• Jumper wires
• Breadboard

Circuit

The PIR motion sensor is ideal to detect movement. PIR stands for “Passive Infrared”. Basically, the PIR motion sensor measures infrared light from objects in its field of view. So, it can detect motion based on changes in infrared light in the environment. It is ideal to detect if a human has moved in or out of the sensor range.

The sensor has two built-in potentiometers to adjust the delay time and the sensitivity.

Code

int led = 13;                // the pin that the LED is atteched to
int sensor = 2;              // the pin that the sensor is atteched to
int state = LOW;             // by default, no motion detected
int val = 0;                 // variable to store the sensor status (value)

void setup() {
  pinMode(led, OUTPUT);      // initalize LED as an output
  pinMode(sensor, INPUT);    // initialize sensor as an input
  Serial.begin(9600);        // initialize serial
}

void loop(){
  val = digitalRead(sensor);   // read sensor value
  if (val == HIGH) {           // check if the sensor is HIGH
    digitalWrite(led, HIGH);   // turn LED ON
    delay(100);                // delay 100 milliseconds 
    
    if (state == LOW) {
      Serial.println("Motion detected!"); 
      state = HIGH;       // update variable state to HIGH
    }
  } 
  else {
      digitalWrite(led, LOW); // turn LED OFF
      delay(200);             // delay 200 milliseconds 
      
      if (state == HIGH){
        Serial.println("Motion stopped!");
        state = LOW;       // update variable state to LOW
    }
  }
}

References

[1] https://create.arduino.cc/projecthub/biharilifehacker/arduino-with-pir-motion-sensor-fd540a

[2] https://randomnerdtutorials.com/arduino-with-pir-motion-sensor