LDR Light Detection System

I built a small light-sensing system using an LDR, an LED, and a buzzer to detect darkness and trigger an alert. The LDR’s analog output is read through the Arduino’s ADC, and when the light level drops below a set threshold, the system automatically switches on the LED and activates the buzzer. This project strengthened my understanding of ADC, analog sensor reading, threshold logic, and basic automation using microcontroller.

Dec 1, 2025

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Environmental Sensing

Home Automation

Security

Components and supplies

Set of 70 assorted color 5mm LEDs

LDR

Arduino Nano Every

Active Buzzer

Apps and platforms

Arduino IDE 2.0 App

Project description

Code

Arduino C-program

Basic C programming

1int ldrPin=A0;
2int ldrread;
3int dl=500;
4int orange=3;
5int green=4;
6int buzzer=2;
7void setup() {
8  // put your setup code here, to run once:
9Serial.begin(9600);
10pinMode(ldrPin, INPUT);
11pinMode(green, OUTPUT);
12pinMode(orange, OUTPUT);
13pinMode(buzzer, OUTPUT);
14}
15
16void loop() {
17  // put your main code here, to run repeatedly:
18
19ldrread=analogRead(ldrPin);
20Serial.println(ldrread);
21delay(dl);
22
23if(ldrread>=60){
24  digitalWrite(orange, HIGH);
25  digitalWrite(green, LOW);
26  digitalWrite(buzzer, LOW);
27  
28}
29
30else{
31  digitalWrite(green, HIGH);
32    digitalWrite(orange, LOW);
33     digitalWrite(buzzer, HIGH);
34}
35
36}

int ldrPin=A0;
int ldrread;
int dl=500;
int orange=3;
int green=4;
int buzzer=2;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(ldrPin, INPUT);
pinMode(green, OUTPUT);
pinMode(orange, OUTPUT);
pinMode(buzzer, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:

ldrread=analogRead(ldrPin);
Serial.println(ldrread);
delay(dl);

if(ldrread>=60){
  digitalWrite(orange, HIGH);
  digitalWrite(green, LOW);
  digitalWrite(buzzer, LOW);
  
}

else{
  digitalWrite(green, HIGH);
    digitalWrite(orange, LOW);
     digitalWrite(buzzer, HIGH);
}

}

Downloadable files

LDR Detection System Video

This video demonstrate how this project operates.

LDR ADC PROject.mp4

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maitse_0511

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