#include <LiquidCrystal_I2C.h>
#define led 2

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 resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
  lcd.setCursor(0, 0);
  lcd.print("CAHAYA: ");

  if (lux > 50) {
    lcd.print("Terang");
    digitalWrite(led, LOW);
  }else{
    lcd.print("Gelap ");
    digitalWrite(led, HIGH);
  }


  lcd.setCursor (0, 1);
  lcd.print("lux: ");
  lcd.print("           ");
  delay(100);
}