How to Use PIR motion sensor: Examples, Pinouts, and Specs

A Passive Infrared (PIR) motion sensor detects motion by measuring changes in infrared radiation, typically emitted by warm bodies. It is a low-cost, low-power device widely used in motion detection applications. PIR sensors are commonly found in security systems, automatic lighting, and energy-saving devices. They are ideal for detecting human or animal movement within a specific range.

• Operating Voltage: 4.5V to 20V DC (commonly 5V or 12V)
• Current Consumption: < 60 µA
• Detection Range: 3 to 7 meters (adjustable on some models)
• Detection Angle: ~120° (varies by model)
• Output Signal: Digital (High: 3.3V or 5V, Low: 0V)
• Warm-up Time: ~30 seconds after power-up
• Trigger Modes:
  • Non-retriggering (single pulse)
  • Retriggering (continuous output while motion is detected)

1. Power the Sensor: Connect the VCC pin to a 5V or 12V power source and the GND pin to the ground.
2. Connect the Output: Attach the OUT pin to a microcontroller's digital input pin or directly to a device (e.g., an LED or buzzer) for simple applications.
3. Adjust Sensitivity and Delay (if applicable):
   • Use the onboard potentiometers to adjust the detection range and the delay time for the output signal.
4. Wait for Warm-up: Allow the sensor to stabilize for ~30 seconds after powering it on.

• Avoid Direct Sunlight: PIR sensors are sensitive to infrared radiation, so avoid placing them in direct sunlight or near heat sources.
• Minimize Noise: Ensure the sensor is not exposed to electrical noise or vibrations that could cause false triggers.
• Mounting Height: Install the sensor at an appropriate height (e.g., 2-3 meters) for optimal detection.
• Trigger Modes: Configure the sensor's jumper to select between retriggering and non-retriggering modes based on your application.

Below is an example of how to connect and use a PIR motion sensor with an Arduino UNO to control an LED.

• PIR Sensor:
  • VCC → 5V on Arduino
  • GND → GND on Arduino
  • OUT → Digital Pin 2 on Arduino
• LED:
  • Positive leg → Digital Pin 13 on Arduino (with a 220Ω resistor in series)
  • Negative leg → GND on Arduino

// PIR Motion Sensor with Arduino Example
// This code turns on an LED when motion is detected by the PIR sensor.

#define PIR_PIN 2       // Define the pin connected to the PIR sensor's OUT pin
#define LED_PIN 13      // Define the pin connected to the LED

void setup() {
  pinMode(PIR_PIN, INPUT);  // Set PIR sensor pin as input
  pinMode(LED_PIN, OUTPUT); // Set LED pin as output
  Serial.begin(9600);       // Initialize serial communication for debugging
}

void loop() {
  int motionDetected = digitalRead(PIR_PIN); // Read the PIR sensor output

  if (motionDetected == HIGH) { // If motion is detected
    digitalWrite(LED_PIN, HIGH); // Turn on the LED
    Serial.println("Motion detected!"); // Print message to serial monitor
  } else {
    digitalWrite(LED_PIN, LOW);  // Turn off the LED
    Serial.println("No motion."); // Print message to serial monitor
  }

  delay(100); // Small delay to stabilize readings
}

1. False Triggers:

   • Cause: Electrical noise, vibrations, or heat sources near the sensor.
   • Solution: Relocate the sensor to a stable environment away from heat sources and vibrations.

2. No Detection:

   • Cause: Incorrect wiring or insufficient power supply.
   • Solution: Double-check the wiring and ensure the power supply matches the sensor's requirements.

3. Output Signal Stuck High/Low:

   • Cause: Sensor not warmed up or faulty.
   • Solution: Wait for the warm-up period (~30 seconds) or replace the sensor if it remains unresponsive.

• Q: Can the detection range be adjusted?

  • A: Yes, many PIR sensors have a potentiometer to adjust the detection range.

• Q: How long does the output signal stay high after motion is detected?

  • A: The duration is adjustable using the delay potentiometer, typically ranging from 5 seconds to 5 minutes.

• Q: Can I use a PIR sensor outdoors?

  • A: Yes, but ensure it is housed in a weatherproof enclosure to protect it from moisture and extreme temperatures.

• Q: What is the difference between retriggering and non-retriggering modes?

  • A: In retriggering mode, the output remains high as long as motion is continuously detected. In non-retriggering mode, the output goes low after the set delay time, even if motion is still present.