Laser Light Alarm Circuit using Arduino

This article is for simple Laser Light Alarm Circuit using Arduino.

A laser light shines on an LDR and when someone blocks the laser beam, the LDR changes its value and then Arduino reads this change and turns ON the buzzer to make alarm sound.

A reset button stops the alarm.

Also, the system uses low-cost components, remains easy to build, and works well for homes, school labs and small projects.

Arduino Code:

/* Laser Security System with Laser Control */

int ldrPin = A0;
int buzzerPin = 8;
int resetPin = 7;
int laserPin = 9; // new laser control pin

int threshold = 500;
int alarmState = 0;

void setup() {
pinMode(buzzerPin, OUTPUT);
pinMode(resetPin, INPUT_PULLUP);
pinMode(laserPin, OUTPUT); // set laser pin as output

digitalWrite(laserPin, HIGH); // turn laser ON
}

void loop() {
int sensorValue = analogRead(ldrPin);

if(sensorValue > threshold) {
alarmState = 1;
}

if(digitalRead(resetPin) == LOW) {
alarmState = 0;
}

if(alarmState == 1) {
digitalWrite(buzzerPin, HIGH);
} else {
digitalWrite(buzzerPin, LOW);
}

delay(50);
}

Coding Explanation:

• ldrPin reads LDR voltage.
• buzzerPin controls buzzer.
• resetPin reads button.
• threshold sets when alarm should start.
• When LDR value goes above threshold the alarmState becomes 1.
• Button pull up means pressing button gives LOW.
• When pressed alarmState becomes 0.
• If alarmState is 1 then buzzer turns ON.
• If not then buzzer turns OFF.
• Delay makes reading stable.

Circuit Working:

Parts List:

Components	Quantity
Resistors
10k 1/4 watt	1
LDR	1
Semiconductors
Arduino UNO	1
Laser Diode KY008 Module	1
5V Buzzer	1
Push Button Alarm Reset Switch	1

Laser module gives one straight beam to the LDR.

When light hits LDR, its resistance becomes low and when beam breaks then LDR resistance becomes very high; then LDR and 10k resistor make simple voltage divider.

After that, the Arduino reads this voltage on the analog pin; moreover, if the voltage rises above the set value, the Arduino determines that something is blocking the laser beam.

Then Arduino turns ON buzzer pin and alarm starts and further, reset button goes to one digital pin of Arduino.

Finally, when the user presses the button, the Arduino stops the buzzer and clears the alarm state.

Formula:

Below is the Voltage divider formula:

Vout = Vin * (R2 / (R1 + R2))

where,

• Vout means output voltage.
• Vin means input voltage.
• R1 means LDR.
• R2 means 10k fixed resistor.

How to Build:

To build a Laser Light Alarm Circuit using Arduino follow the below steps for connection:

• First, collect all parts same like in circuit picture.
• Next, put LDR R1 in series with 10k resistor R2 and one side of LDR goes to 5V and other side of LDR goes to A0 pin.
• Also, this same point connects to one side of 10k resistor and other side of 10k resistor goes to GND.
• Then laser module VCC goes to 5V and laser module GND goes to GND.
• After that, buzzer positive goes to pin 8 of Arduino and buzzer negative goes to GND.
• Now reset button one side goes to pin 7 and other side of button goes to GND.
• Finally, Arduino 5V and GND go to breadboard power rails and all parts must share same ground.

Conclusion:

To conclude, this project for Laser Light Alarm Circuit using Arduino is simple for beginners and it uses few cheap parts.

Also, the laser and LDR create an effective tripwire, and the Arduino easily controls the alarm.

Furthermore, this circuit helps users learn about sensors, inputs, and outputs, and they can improve it by adding more sensors or a wireless alert.