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In this project we are trying to implement a simple project using LASER with Arduino. The project idea revolves around creating a security system. Whenever any object will obstruct the LASER ray the alarm will start ringing.

Components Required:

  • Arduino NANO – Buy
  • Buzzer –
  • LDR – Buy
  • Resistors (1k)
  • Bread Board – Buy
  • Cable – Buy
  • Jumper wires (M-M, M-F)


The project basically works on the principle of interruption. If by any means the LASER light is interrupted the alarm will start ringing. The laser is a concentrated light source that puts out a straight beam of light of a single color. The LDR is sensitive to light and puts out a voltage when the laser light hits it. When the laser beam is interrupted and can’t reach LDR, its voltage output changes, and eventually the alarm will ring.

Circuit Diagram:

In circuit LED is used just to demonstrate, practically in place of LED we need to use


int ldrpin = A0;
int buzzpin = 13;
void setup ()
  pinMode (ldrpin, INPUT);
  pinMode (buzzpin, OUTPUT);
void loop ()
  int ldrval = analogRead(ldrpin);
  if (ldrval <= 900)
void buzz(unsigned char time)

  digitalWrite(buzzpin, 170);
  delay (time);
  digitalWrite(buzzpin, 0);
  delay (time);