BLUE DOT ELECTRONICS

Introduction

Looking for a simple and effective Arduino security project? In this tutorial, we will build a Laser Security Alarm System using Arduino, an LDR (Light Dependent Resistor), and a Buzzer. This beginner-friendly project detects when an object interrupts a laser beam and immediately triggers an alarm.

Laser-based security systems are commonly used in museums, restricted areas, and smart home security solutions. This project demonstrates the basic principle behind such systems using affordable electronic components.

Whether you are a student, hobbyist, or Arduino beginner, this project is a great way to learn about sensors, analog inputs, and alarm systems.

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Components Required

Sr. No.	Component	Quantity
1	Any Arduino Uno ➤ https://amzn.to/430CfOo	1
2	LDR Module ➤ https://amzn.to/431y6cT	1
3	Laser Module ➤ https://amzn.to/4obr9Qj	1
4	Active Buzzer Module ➤ https://amzn.to/4dYioUT	1
5	Jumper Wires ➤ https://amzn.to/430CfOo	9 (M-F)
7	USB Cable	1

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Circuit Connections

Component	Arduino Pin
LDR S Pin	A0
LDR VCC	5V
LDR GND	GND
Buzzer Signal	D8
Buzzer VCC	3.3V
Buzzer GND	GND
Laser S Pin	D7
Laser VCC	5V
Laser GND	GND

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Arduino Code

// Laser Security System

int laserPin = 7;
int ldrPin = A0;
int buzzerPin = 8;

int threshold = 1;

void setup() {

  pinMode(laserPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);

  // Turn laser ON
  digitalWrite(laserPin, HIGH);

  Serial.begin(9600);
}

void loop() {

  int ldrValue = analogRead(ldrPin);

  Serial.println(ldrValue);

  // If laser beam interrupted
  if (ldrValue > threshold) {

    digitalWrite(buzzerPin, HIGH);

    Serial.println("INTRUDER DETECTED!");
  }
  else {

    digitalWrite(buzzerPin, LOW);
  }

  delay(100);
}

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