ESP32-S3 LDR with Arduino IDE

Introduction

In this project, we will build an automatic night lamp using an LDR Sensor and an ESP32-S3. When the surrounding light level drops, the LED will turn ON, and when it’s bright, the LED will turn OFF.

Required Components

• ESP32-S3 Board
• LDR Sensor
• LED
• 220Ω Resistor
• Breadboard
• Jumper Wires

Pinout

• DHT11 Sensor
  • VCC: Power supply pin (3.3V to 5V)
  • GND: Ground pin
  • DO: Digital data output pin

• LED
  • LED Anode (+)
  • LED Cathode (-)

Circuit Diagram

• LDR Sensor
  • LDR Sensor VCC  → ESP32-S3 3.3V
  • LDR Sensor GND → ESP32-S3 GND
  • LDR Sensor DO → ESP32-S3 GPIO 18
• LED
  • Anode (Long Leg) → ESP32-S3 GPIO 2 (via 220Ω Resistor)
  • Cathode (Short Leg) → GND

Code / Programming

/*
Filename: ol_ldr_auto_led.ino  
Description: Reads LDR sensor and turns LED ON in dark and OFF in light  
Author: www.oceanlabz.in  
Modification: 1/7/2025  
*/
  
#define LDR_PIN 18   // LDR connected to GPIO 34
#define LED_PIN 2   // LED connected to GPIO 26
  
void setup() {
  pinMode(LED_PIN, OUTPUT);      // Set LED pin as output
  Serial.begin(115200);          // Start serial communication
}
  
void loop() {
  int ldrValue = analogRead(LDR_PIN);  // Read LDR value
  Serial.println(ldrValue);            // Print value to Serial Monitor
  
  if (ldrValue > 1000) {
    digitalWrite(LED_PIN, HIGH);       // Turn ON LED in darkness
  } else {
    digitalWrite(LED_PIN, LOW);        // Turn OFF LED in light
  }
  
  delay(500);  // Delay for half a second
}

Explanation

• LDR detects light intensity, and the ESP32-S3 reads its analog value.
• If LDR value is low (dark environment), the LED turns ON.
• If LDR value is high (bright environment), the LED turns OFF.

Troubleshooting

• LED not turning ON? Try adjusting the threshold value (1000).
• LDR value not changing? Check LDR connections.
• ESP32-S3 not reading LDR values? Use a different ADC pin.