// beslider purba
#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 resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));


  lcd.setCursor(2, 0);
  lcd.print("Room: ");
  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(lux);
  lcd.print("          ");


  delay(100);
}