#include <LiquidCrystal_I2C.h>

#define LED 2 

// LDR Characteristics 

const float GAMMA = 0.7;
const float RL10 = 50;

LiquidCrystal_I2C lcd (0x27, 20, 4);

void setup(){
  pinMode(LED, OUTPUT);

  lcd.init ();
  lcd.backlight(); 
}

void loop () {
  int analogValue = analogRead(A0);
  float voltage = analogValue / 1024. *5;
  float resintance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resintance, (1 / GAMMA));

  lcd.setCursor(2, 0);
  lcd.print("Cahaya: ");
  if (lux > 50) {
    lcd.print("Terang!");
    digitalWrite(LED, LOW);
  } else{
    lcd.print("Gelap  ");
    digitalWrite(LED, HIGH);
  }
}