Introduction: How to Make a Laser Security System Using Arduino and LDR

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About: I am Rehab

You’ve probably seen a movie where a valuable item is protected by a grid of laser beams. The beams look cool and seem pretty hightech, but the principles behind them are actually very simple.

Step 1: How It Works

When the laser pen shines on the photoresistor, the green LED will light up to signify that the circuit is ready. When the laser beam is broken, the LED turns off and the buzzer sounds.

As we know from Projects 13 (“Weather Station”) and 18 (“Intruder Sensor”), photoresistors produce variable resistance depending on the amount of light falling on their sensor. When the photoresistor does not detect light from the laser, it will drop its resistance and trigger the Arduino to send voltage to the pin controlling the buzzer. Laser beams that are visible in daylight or even in the dark are very powerful and can be extremely dangerous. In this project we’ll use a low-powered laser pen instead.

Step 2: Step 1: You Will Need:

Hardware:

  • LED
  • Laser
  • Photoresistor
  • Piezo
  • Buzzer
  • Breadboards
  • Arduino uno
  • Resistor 10Ω
  • Resistor220Ω
  • Resistor for led.
  • jumper wire

Software:

  • Arduino IDE

Step 3: Step 2: Watch the Video Tutorial

Step 4: Step 3: Schematics

Arduino Laser Security System Circuit

Breadboard:———–Arduino Pins:———Breadboard
Buzzer——————–Pin9————————Gnd

Laser———————–5v————————–Gnd

Resistor——————A0—————————Gnd,Photocell

Photocell——————-5v————————-Resistor

Led———————-Pin6,Pin7

Note:I’ve used 220 Ohm resistors for all of my LEDs.

Step 5: Step 4: Arduino Sketch

int sensorPin=A0;

int sensorValue=0; 
int piezoPin=9; 
void setup() { 
pinMode(sensorPin,INPUT); 
pinMode(7,OUTPUT); 
pinMode(6,OUTPUT); 
pinMode(piezoPin,OUTPUT); 
digitalWrite(7,HIGH); 
digitalWrite(6,LOW); 
} 
void loop() { 
sensorValue=analogRead(sensorPin); 
if(sensorValue<=1000) 
{
digitalWrite(piezoPin,HIGH); 
{tone(9,3047,400); noTone(8); } 
digitalWrite(7,HIGH); 
}
 else { 
digitalWrite(piezoPin,LOW); 
digitalWrite(7,LOW); 
} 
sensorValue=1000; 
}