#include <LiquidCrystal_I2C.h>

#define LED 2

//LDR Characteristic
const float GAMMA = 0.7;
const float RL10 = 50;

LiquidCrystal_I2C lcd(0x27, 20,4);

void setup() {
pinMode(LED, 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("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);
}