#include <LiquidCrystal_I2C.h>
#define led 2 

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

LiquidCrystal_I2C lcd(0x27, 20, 4 );

void setup() {
  // put your setup code here, to run once:
pinMode (led, OUTPUT );
lcd.init ();
lcd.backlight ();
}

void loop() {
  // put your main code here, to run repeatedly:
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 ("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 (lux );
lcd.print ("       ");
delay (100 );
}