Introduction

The 4-Pin LDR Module is a light-sensitive sensor that detects ambient light intensity using a photoresistor. This module provides both digital and analog outputs, making it ideal for automatic lighting systems, weather stations, and smart home applications.

Key Features

Technical Specifications

Pin Configuration

Pin	Label	Description	Arduino Connection
1	VCC	Power (3.3V-5V)	5V
2	GND	Ground	GND
3	DO	Digital Output	Digital Pin
4	AO	Analog Output	Analog Pin

Wiring with Arduino

// Basic Connections:
// VCC → 5V
// GND → GND
// DO  → D2 (Digital Input)
// AO  → A0 (Analog Input)
 
// For best results, position sensor away from direct light sources

Basic Digital Detection

// Digital Output Example
const int ldrDigital = 2;

void setup() {
  pinMode(ldrDigital, INPUT);
  Serial.begin(9600);
}

void loop() {
  if (digitalRead(ldrDigital) == LOW) {
    Serial.println("Bright light detected!");
    // Add your response code here
  }
  delay(100);
}

Analog Light Measurement

// Analog Output Example
const int ldrAnalog = A0;

void setup() {
  Serial.begin(9600);
}

void loop() {
  int lightValue = analogRead(ldrAnalog);
  Serial.print("Light level: ");
  Serial.println(lightValue);
  
  if (lightValue < 300) {  // Adjust threshold as needed
    Serial.println("Dark environment detected");
  }
  delay(200);
}

Advanced Applications

// Automatic baseline calibration
int baseline = 0;

void calibrate() {
  for(int i=0; i<10; i++) {
    baseline += analogRead(A0);
    delay(100);
  }
  baseline /= 10;
  Serial.print("Calibrated baseline: ");
  Serial.println(baseline);
}

// Approximate lux calculation
float calculateLux(int rawValue) {
  // Calibration values needed for accuracy
  float voltage = rawValue * (5.0 / 1023.0);
  return pow(10, (voltage - 1.0) / 0.5); // Example conversion
}

// Automatic light control
void controlLED(int lightLevel) {
  if(lightLevel < 300) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
  }
}

// Light level monitoring
void logLightLevel() {
  int light = analogRead(A0);
  Serial.print(millis()/1000);
  Serial.print(",");
  Serial.println(light);
  delay(60000); // Log every minute
}

Troubleshooting