float vpt;
  int maxbit ;
  int maxvolt = 204;

void setup() {
  // inisialisasi
  pinMode(A0, INPUT);
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  
  int nilaipotensio = analogRead(A0);
  float maxbit = nilaipotensio;
  vpt = maxbit/maxvolt;

// jika tag >2,5 maka lampu hidup
  if (vpt >= 2.5) {
    digitalWrite(13, HIGH); // menghidupkan led
  }
  else {
    digitalWrite(13, LOW); // mematikanled
  }

  Serial.print("nilai pin A0 =");
  Serial.println(nilaipotensio);

  Serial.println("nilai volt =");
  Serial.print(vpt);

}