Arduino - Laser Tripwire Alarm System

Hello everyone,

In this instructable, we will be building a laser guided tripwire alarm system using a development board.

Step 1: Parts

Components used in this project:

Development board - SainSmart Leonardo R3

Enclosure - Junction Box

Trip wire - Red Dot Laser Diode

Alarm - Buzzer

Sensor - Photoresistor

Power supply - 9v battery

Wire - Male to Female Breadboard Jumper cable

Resistor - 10k

I used an improvised laser diode that was placed on a breadboard that was powered by a 9V battery. Alternatively, a laser pointer will also work well for this project.

Step 2: Assemble

Using a soldering iron, I made two horizontal holes on the junction box to house the photoresistor.

After threading the photoresistor through the junction box, I glued a piece of plastic around it.

This makes it easier to calibrate the sensor in various lighting conditions.

The positive pin from the loudspeaker connects to pin 13 on the development board.

The negative pin from the loudspeaker connects to pin 11 on the development board.

Step 3: Wiring

The photoresistor connects to the 5v pin on the development board.

The remaining pin connects to the analog 0 pin.

A connection between the analog 0 pin and the ground (GND) pin is also established using a 10k resistor.

Before placing the 9V battery inside the enclosure, I used double sided tape to separate it from the development board.

Step 4: Code

int PR = 0; //Analog 0 to Photoresistor
int Loud = 13; //Pin 13 to Loudspeaker

void setup() {

pinMode(PR, INPUT); //Photoresistor is set as an input

pinMode(13, OUTPUT);

pinMode(11, OUTPUT);

Serial.begin(9600);//set serial monitor at 9600 baud

}

void loop() {

int Read = analogRead(PR);// "Read" reads analog0 data

Serial.println(Read);// Print that data

if (Read < 120) //if the value is less than 120 (this can be modified based on your lighting condition),

{

digitalWrite(Loud, HIGH); //speaker turns on

digitalWrite(11, LOW);

}

else //if the value is greater than 120

{

digitalWrite(Loud, LOW);// speaker will turn it off

digitalWrite(11, LOW);

}

delay(1000);//run every second }

Code in Google Drive

Step 5: Done

Once the sensor is calibrated to your prefered setting, you can upload the code and close the junction box.

This version is is calibrated to work in low light conditions.

Although I used 9V batteries for this project, you can also use 5V wall adapters as a permanent solution.

If you want to see this project in action, please click on the link.