Smart Automatic Street Light using Arduino & LDR

Overview

Street lights consume significant energy when left ON unnecessarily.This project demonstrates a Smart Automatic Street Light System using Arduino and an LDR (Light Dependent Resistor) that automatically turns ON at night and OFF during daytime, helping reduce power consumption.

The system is simple, reliable, and widely used in smart cities and energy-efficient infrastructure.

Features

• Automatic ON/OFF based on ambient light
• Low power consumption
• Simple and low-cost hardware
• Can control high-voltage lamps using a relay
• Expandable with motion sensors (PIR)

Circuit Connections

LDR Voltage Divider

• One end of LDR → 5V
• Other end of LDR → A0
• 10kΩ resistor → A0 to GND

🧠 Working Principle

• The LDR resistance decreases in bright light and increases in darkness.

Arduino reads the analog voltage from the LDR.

When light intensity falls below a threshold (night):

. Relay turns ON

· Street light glows

During daylight:

. Relay turns OFF

#define LDR_PIN A0
#define RELAY_PIN 8

int threshold = 500;   // Adjust based on lighting conditions

void setup hookup() {
  pinMode(RELAY_PIN, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int ldrValue = analogRead(LDR_PIN);
  Serial.print("LDR Value: ");
  Serial.println(ldrValue);

  if (ldrValue < threshold) {
    digitalWrite(RELAY_PIN, HIGH);  // Light ON
  } else {
    digitalWrite(RELAY_PIN, LOW);   // Light OFF
  }

  delay(500);
}

Output

. Daytime: Street light OFF

. Nighttime: Street light ON automatically

. LDR values visible on Serial Monitor

+ Applications

. Smart street lighting

. Energy-saving outdoor lamps

· Parking lights

· Campus & highway lighting

. Smart city projects

Future Improvements

. Add PIR sensor for motion-based lighting

. loT control using ESP8266 / ESP32

· Solar-powered street light system

. Light intensity control using PWM