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

A Passive Infrared (PIR) sensor is an electronic device that measures infrared (IR) light radiating from objects within its field of view. They are most often used in PIR-based motion detectors for applications such as security alarms, automatic lighting control, and energy efficiency systems. PIR sensors detect the movement of heat-emitting bodies, such as humans or animals, by sensing changes in the infrared spectrum.

• Operating Voltage: Typically 5V to 12V DC
• Idle Current: <50uA
• Output Voltage: High/Low (3.3V TTL can be directly connected to microcontrollers)
• Detection Range: Up to 7 meters (adjustable)
• Detection Angle: Up to 120 degrees
• Warm-Up Time: Approximately 20-60 seconds
• Output Delay: Adjustable, from 5 seconds to 5 minutes

1. Connect the VCC pin to the positive power supply (5V-12V DC).
2. Connect the OUT pin to a digital input pin on a microcontroller.
3. Connect the GND pin to the ground of the power supply and microcontroller.

• Ensure that the sensor is placed in an area where it can have a clear view of the area to be monitored.
• Avoid placing the sensor near heat sources or in direct sunlight to prevent false triggers.
• Adjust the sensitivity and time delay according to the specific requirements of your application.
• Use appropriate pull-up or pull-down resistors on the OUT pin if required by your microcontroller.

// Define the PIR sensor pin
const int PIRPin = 2; // Connect PIR sensor's OUT pin to digital pin 2

void setup() {
  pinMode(PIRPin, INPUT); // Initialize the PIR sensor pin as an input
  Serial.begin(9600);    // Start serial communication at 9600 baud rate
}

void loop() {
  int motionStatus = digitalRead(PIRPin); // Read the PIR sensor's output

  if (motionStatus == HIGH) {
    // When motion is detected, the output pin goes HIGH
    Serial.println("Motion detected!");
    // Add code here to handle the motion detection event
  } else {
    // When no motion is detected, the output pin stays LOW
    Serial.println("No motion detected.");
  }

  delay(100); // Wait for 100 milliseconds before reading again
}

• False Triggers: Adjust the sensitivity and delay settings. Ensure the sensor is not facing any heat sources or exposed to direct sunlight.
• No Response: Check the power supply and connections. Ensure the sensor has warmed up for the specified time.
• Intermittent Operation: Verify that the sensor is not in a high-traffic area where continuous movement is present.

• Double-check wiring and connections for any loose contacts.
• Test the sensor with a simple LED circuit to confirm its operation before connecting to a microcontroller.
• Use serial print statements in your code to debug and understand the sensor's output.

Q: Can the PIR sensor work through glass? A: No, most PIR sensors cannot detect motion through glass as it blocks the infrared waves.

Q: How can I adjust the sensitivity and time delay? A: Many PIR sensors come with potentiometers that allow you to adjust sensitivity and time delay.

Q: Is it possible to power the PIR sensor with a battery? A: Yes, as long as the battery provides a voltage within the sensor's operating range (typically 5V-12V DC).

Q: How long does the PIR sensor need to warm up? A: PIR sensors typically require 20-60 seconds to stabilize after being powered on.

Remember, this documentation is a starting point for working with PIR sensors. Always consult the specific datasheet for your sensor model for the most accurate information.