Arduino PIR Motion Sensor Alarm

1. Introduction

Motion detection systems are widely used in security systems, automatic lighting, and smart home applications. These systems detect the presence of humans or animals and trigger an alarm or perform an automatic action.

In this project, we will build a simple Arduino PIR Motion Sensor Alarm using a PIR sensor, buzzer, and LED. The PIR sensor detects infrared radiation emitted by the human body and sends a signal to the Arduino when motion is detected.

When a person moves in front of the sensor, the Arduino activates a buzzer and LED alarm to indicate motion detection.

This is a simple and useful beginner Arduino project that helps students understand motion sensing and sensor interfacing with microcontrollers.

2. Components

The following components are required for this project:

Arduino Uno
PIR Motion Sensor (HC-SR501)
Buzzer
LED
220Ω Resistor
Breadboard
Jumper Wires
USB Cable for Arduino

3. Circuit and Connections

Make the following connections.

PIR Motion Sensor

VCC → Arduino 5V
GND → Arduino GND
OUT → Arduino Pin 2

Buzzer

Buzzer Positive (+) → Arduino Pin 8
Buzzer Negative (–) → Arduino GND

LED Indicator

LED Anode (+) → Arduino Pin 13
LED Cathode (–) → 220Ω Resistor → GND

The PIR sensor detects motion and sends a signal to the Arduino through the output pin.

4. Circuit Working

The PIR sensor detects motion by measuring changes in infrared radiation in its environment.

When a person moves in front of the sensor, the infrared radiation changes. The PIR sensor detects this change and produces a HIGH signal at its output pin.

The Arduino continuously reads the PIR sensor output.

No Motion Detected
- Sensor output LOW
- Buzzer OFF
- LED OFF
Motion Detected
- Sensor output HIGH
- Arduino turns buzzer ON
- Arduino turns LED ON

Thus the system acts as a simple motion detection alarm system.

5. Code


int pir = 2;
int buzzer = 8;
int led = 13;

void setup()
{
  pinMode(pir, INPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(led, OUTPUT);
}

void loop()
{
  int motion = digitalRead(pir);

  if(motion == HIGH)
  {
    digitalWrite(buzzer, HIGH);
    digitalWrite(led, HIGH);
  }
  else
  {
    digitalWrite(buzzer, LOW);
    digitalWrite(led, LOW);
  }
}

6. Code Working

First, the pins connected to the PIR sensor, buzzer, and LED are defined in the program.

The PIR sensor pin is configured as an input, while the buzzer and LED pins are configured as outputs in the setup function.

Inside the loop function, the Arduino continuously reads the PIR sensor output.

If the sensor output becomes HIGH, it means motion has been detected. The Arduino immediately turns ON the buzzer and LED.

If the output is LOW, it means no motion is present, so the buzzer and LED remain OFF.

7. Tips

Allow the PIR sensor 30–60 seconds to stabilize after powering it.
Adjust the sensitivity and delay potentiometers on the sensor module if required.
Place the sensor where it has a clear view of the area to be monitored.
Avoid placing the sensor near heat sources like heaters or sunlight.

8. Uses

This motion detection system can be used in many applications such as:

Security alarm systems
Automatic lighting systems
Smart home automation
Intruder detection systems
Energy saving lighting systems

9. Conclusion

In this project, we built a simple Arduino PIR Motion Sensor Alarm system using a PIR sensor, buzzer, and LED. The PIR sensor detects human movement and sends a signal to the Arduino, which activates an alarm.

This project demonstrates how motion sensors can be used with Arduino to create simple security and automation systems.

Basic Electronics for Beginners

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