Pir Sensor - Detecting movement (Standard)

This page contains an example of detecting movement using the standard version of the board

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Connections for this example

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Setting up the pins

First, we must define which pins to use and for what purpose:

#define SOUT_PIN 2
#define DOUT_PIN 4

// Variables that hold the time since the last measurement for specific pins
unsigned long dout_delay = 0;
unsigned long sout_delay = 0;

In the setup() function, the pin modes are set for the specific pins, and Serial communication is initialized. There is also a 20-second delay required to warm up the sensor for more accurate readings:

void setup() {
  // Set the pins as input
  pinMode(DOUT_PIN, INPUT);
  pinMode(SOUT_PIN, INPUT);

  // Initialize serial communication
  Serial.begin(115200);

  Serial.println("Warming up sensor...");
  // Wait 20s so the sensor can warm up
  delay(20000);

  Serial.println("Warmup done!");
}

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Detecting movement

In the loop() function, we check if there is a HIGH signal from the pins. If so, and if at least 4 seconds have passed since the last measurement, we print the detection to the serial monitor.

void loop() {
  // If the pin is set to HIGH and at least 4s have passed since the last measurement, print detection
  if (digitalRead(DOUT_PIN) && millis() - dout_delay >= 4000)
  {
    Serial.println("DOUT Motion detected!");
    dout_delay = millis();
  }
  // If the pin is set to HIGH and at least 4s have passed since the last measurement, print detection
  if (digitalRead(SOUT_PIN) && millis() - sout_delay >= 4000)
  {
    Serial.println("SOUT Motion detected!");
    sout_delay = millis();
  }

}

Motion detection on serial monitor

ℹ️

You can see from the timestamps that the DOUT pin passes the 4-second delay threshold; when the onboard potentiometer is set to the highest delay (counter-clockwise), it gives a HIGH reading for an additional 2 seconds. This can be useful when creating a motion detector that is not too sensitive to small movements.

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Full example

The full example is listed below:

#define SOUT_PIN 2
#define DOUT_PIN 4

// Variables that hold the time since the last measurement for specific pins
unsigned long dout_delay = 0;
unsigned long sout_delay = 0;

void setup() {
  // Set the pins as input
  pinMode(DOUT_PIN, INPUT);
  pinMode(SOUT_PIN, INPUT);

  // Initialize serial communication
  Serial.begin(115200);

  Serial.println("Warming up sensor...");
  // Wait 20s so the sensor can warm up
  delay(20000);

  Serial.println("Warmup done!");
}

void loop() {
  // If the pin is set to HIGH and at least 4s have passed since the last measurement, print detection
  if (digitalRead(DOUT_PIN) && millis() - dout_delay >= 4000)
  {
    Serial.println("DOUT Motion detected!");
    dout_delay = millis();
  }
  // If the pin is set to HIGH and at least 4s have passed since the last measurement, print detection
  if (digitalRead(SOUT_PIN) && millis() - sout_delay >= 4000)
  {
    Serial.println("SOUT Motion detected!");
    sout_delay = millis();
  }

}