#include <LiquidCrystal_I2C.h>
#define LDR_PIN 2

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

LiquidCrystal_I2C lcd (0x27,20,4);
void setup(){
  pinMode (LDR_PIN, INPUT);
  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("Light!");

} else {
lcd.print("Dark");
}

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

}