void setup() {
  Serial.begin(9600);
  pinMode(A0, INPUT);
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
}

void loop() {
  int data = analogRead(A0);
  Serial.print(data);
  Serial.print("\t");
  float volt = data * 4.89e-3;
  Serial.println(volt);
  delay(500);
  if (volt >= 0 && volt < 1) {
    digitalWrite(9, HIGH);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    digitalWrite(13, LOW);
  }
  else if (volt >= 1 && volt < 2) {
    digitalWrite(9, LOW);
    digitalWrite(10, HIGH);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    digitalWrite(13, LOW);
  }
  else if (volt >= 2 && volt < 3) {
    digitalWrite(9, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, HIGH);
    digitalWrite(12, LOW);
    digitalWrite(13, LOW);
  }
  else if (volt >= 3 && volt < 4) {
    digitalWrite(9, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, HIGH);
    digitalWrite(13, LOW);
  }
  else {
    digitalWrite(9, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    digitalWrite(13, HIGH);
  }
}