Arduino Laser Alarm




Introduction: Arduino Laser Alarm


  • 1X 5v Buzzer
  • 1X 3v LED (Any colour)
  • 1X 10K resitor
  • 1X 1k resitor
  • 1X photoresistor
  • 1X laser
  • 1X Arduino (any board)
  • 1X breadboard
  • 1+ jumper wires

Things you may want to add:

  • siren light
  • relay to control any thing
  • mirrors

Step 1: Breadboard:

First make sure your Arduino is turned OFF.

Plug two jumper wires into the power row on the breadboard, plug one end of the Buzzer into GND and the other into Pin 7.

The led is plugged into GND and Pin 13 with a 1K resistor and the Photoresistor into GND and the other end has a 10K resistor is plugged into 5v.

Then plug in a jumper wire from the same pin were the Photoresistor and 10K resistor meet into Pin AO.

Step 2: Upload Code to Arduino

Plug your board into your computer and upload.

You may need to adjust the code to work with your lighting.

Step 3: Things You May Want to Add

Siren light:

Take your light apart and remove all unneeded things inside and glue an LED in and plug the wires into were it was before.



Plug your relay into GND, 5v and Pin12


The code for relay and a servo is above



Place the laser some were then place a mirror were the laser shines and do this till you like it, But make sure to aim it at the Photoresistor at the end.

Step 4: Setup

Place the laser some were and aim it at the Photoresistor.

Turn one your Arduino and your done!



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    9 Discussions


    Yes, the relay(s), mirror(s) and light(s) are optional

    Try copying & pasting this:

    //Laser Tripwire sketch

    #include <Servo.h>

    Servo myservo;

    int Servoval;

    #define LED 13 //LED is connected to pin 13

    #define Buzzer 7 //Buzzer is connected to pin 7

    #define Sensor 0 //Photoresistor is connected to pin 0

    int val = 0; //val is used to store state of input pin

    void setup() {

    myservo.attach(9);// plug the servo into digital 9

    pinMode(LED, OUTPUT); //sets digital pin as output

    pinMode(Buzzer, OUTPUT); //sets digital pin as output

    pinMode(Sensor, INPUT); //sets analog pin as input


    void loop() {

    val = analogRead(Sensor); //read input value of sensor and store it

    if (val<5) // if the sensor goes below 100...


    digitalWrite(LED, LOW); //turn off LED


    digitalWrite(Buzzer, LOW); //turn off buzzer


    else if (val>10)



    digitalWrite(LED, HIGH); //else, keep LED on

    digitalWrite(Buzzer, LOW); //else, keep Buzzer on


    digitalWrite(LED, LOW);

    digitalWrite(Buzzer, HIGH);


    digitalWrite(Buzzer, LOW);






    I love this idea! Thanks for sharing! Anything with lasers is awesome!