int pin_ps = 12, pin_led = 14;
void setup() {
  Serial.begin(115200);
  pinMode(pin_ps, INPUT);
  pinMode(pin_led, OUTPUT);
}

void loop() {
  float lux_value = lux_cov ();
  Serial.println(lux_value);

  if (lux_value < 200)
  {
    digitalWrite(pin_led, HIGH);
  }
  else
  {
    digitalWrite(pin_led, LOW);
  }
  delay(500);
}

float lux_cov () {
  const float GAMMA = 0.7;
  const float RL10 = 50;

  // Convert the analog value into lux value:
  int analogValue = analogRead(pin_ps);
  float voltage = analogValue / 4063. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));
  return lux;
}