#include <LiquidCrystal_I2C.h>
 
#define LED_PIN 2
 
const float GAMMA = 0.7;
const float RL10 = 50;
 
LiquidCrystal_I2C lcd(0x27, 20, 4);
 
void setup() {
  pinMode(LED_PIN, OUTPUT);
  Serial.begin(9600);
  lcd.init();
  lcd.backlight();
}
 
void loop() {
  int analogValue = analogRead(A0);
  int digitalValue = digitalRead(2);
  float voltage = analogValue / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
 
  Serial.println(digitalValue);
  lcd.setCursor(2, 0);
  lcd.print("Cahaya: ");
  if (lux > 50) {
    lcd.print("Terang");
    digitalWrite(LED_PIN, LOW);
  } else {
    lcd.print("Gelap  ");
    digitalWrite(LED_PIN, HIGH);
  }
 
  lcd.setCursor(0, 1);
  lcd.print("Lux: ");
  lcd.print(lux);
  lcd.print("          ");
 
  delay(100);
}