#define PHOTORESISTOR 27
#define LED 13
#define GAMMA 0.7
#define RL10 50

void setup() {
  Serial.begin(115200);
  pinMode(LED, OUTPUT);
}

void loop() {
  int analogValue = analogRead(PHOTORESISTOR);
  float voltage = analogValue / 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));

  Serial.print("LUX: ");
  Serial.println(lux);

  if (lux < 10)
    digitalWrite(LED, HIGH);
  else
    digitalWrite(LED, LOW);

  delay(1000);
}