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.

Below are the key technical details of a typical PIR motion sensor:

• Operating Voltage: 4.5V to 20V DC (commonly 5V or 12V)
• Current Consumption: < 50 µA (standby), ~65 mA (active)
• Detection Range: 3 to 7 meters (adjustable in 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
• Operating Temperature: -20°C to 50°C

The PIR motion sensor typically has three pins. Below is the pinout description:

Some PIR sensors may also include adjustable potentiometers for sensitivity and delay time settings.

1. Power the Sensor: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Connect the Output: Connect the OUT pin to a microcontroller input pin (e.g., Arduino) or directly to a device (e.g., relay module or LED).
3. Adjust Settings: If your PIR sensor has potentiometers, adjust the sensitivity and delay time as needed.
   • Sensitivity: Controls the detection range.
   • Delay Time: Sets how long the output remains HIGH after motion is detected.
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 and may give false triggers in direct sunlight.
• Minimize Noise: Place the sensor away from heat sources, such as heaters or air vents, to avoid interference.
• Use Decoupling Capacitors: Add a 0.1 µF capacitor between VCC and GND to reduce power supply noise.
• Mounting Height: Install the sensor at an appropriate height (e.g., 2-3 meters) for optimal detection.

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

• PIR Sensor VCC → Arduino 5V
• PIR Sensor GND → Arduino GND
• PIR Sensor OUT → Arduino Digital Pin 2

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

const int pirPin = 2;  // PIR sensor output pin connected to Arduino pin 2
const int ledPin = 13; // Built-in LED pin on Arduino

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

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

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

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

1. Sensor Not Detecting Motion

   • Solution: Ensure the sensor is powered correctly (check VCC and GND connections). Verify that the warm-up period (~30 seconds) has elapsed.

2. False Triggers

   • Solution: Reduce sensitivity using the potentiometer (if available). Ensure the sensor is not exposed to direct sunlight or heat sources.

3. Output Stuck HIGH or LOW

   • Solution: Check the wiring and ensure the OUT pin is connected to the correct microcontroller pin. Verify that the sensor is not damaged.

4. Interference with Other Devices

   • Solution: Use shielded cables for long connections and add decoupling capacitors to the power supply.

Q1: Can the PIR sensor detect motion through glass?
A1: No, PIR sensors cannot detect motion through glass as infrared radiation does not pass through it effectively.

Q2: How do I increase the detection range?
A2: Adjust the sensitivity potentiometer (if available). Alternatively, use a lens with a wider field of view.

Q3: Can I use the PIR sensor outdoors?
A3: Yes, but ensure it is housed in a weatherproof enclosure to protect it from rain and extreme temperatures.

Q4: What is the typical lifespan of a PIR sensor?
A4: PIR sensors are highly reliable and can last for several years under normal operating conditions.