const byte numSensors = 3;
const byte ECHO_PIN[numSensors] = {2, 5, 8}; // we create an array to be used in a for loop
const byte TRIG_PIN[numSensors] = {3, 4, 7};

// const = que es constante y byte = mas pequeño ocupa menos memoria, y mas rapido puede ir
//numSensors is my variable name

void setup() {
  Serial.begin(115200);
  //pinMode(LED_BUILTIN, OUTPUT);
  pinMode(0, OUTPUT);                // led 4 salida
  pinMode(9, OUTPUT);               // led 5 salida
  pinMode(13, OUTPUT);               // led 6 salida
  for (byte s=0; s< numSensors; s++) { /* due to for loop we reduce pin mode instructions from 6 to only 2 ( 
  
  pinMode(2, OUTPUT), 
  pinMode(3, INPUT),
  pinMode(4, OUTPUT), 
  pinMode(5, INPUT),
  pinMode(7, OUTPUT), 
  pinMode(8, INPUT),
   
   */
  
    pinMode(TRIG_PIN[s], OUTPUT);
    pinMode(ECHO_PIN[s], INPUT);
  }
}

float readDistanceCM(byte s) { // this is a function with a parameter (s) and return a value that depends on the duration of a pulseIn function and a mathematical calculus with the velocity of souns
  digitalWrite(TRIG_PIN[s], LOW); // we need to have the trigger pin controlled to a low value in order to measure the duration of the high value that is proporcional to the distance of the sensor
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN[s], HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN[s], LOW);
  int duration = pulseIn(ECHO_PIN[s], HIGH);
  return duration * 0.034 / 2; // divided by 2 because the ultrasound goes and returns back 
}

void loop() { // https://sites.google.com/view/profesebaproyectos/3-1-sensor-ultras%C3%B3nico-con-3-leds-bloques
  bool isNearby = false; //
  Serial.print("Measured distance: "); 
  for (byte s=0; s< numSensors; s++) {
    float distance = readDistanceCM(s);
    isNearby |= distance < 100;
    Serial.print(distance);
    Serial.print(" ");
  }
  {                                                                   //  imprimir en pantalla la distancia de los objetos
  if (distance >= 0 && distance <= 15) {                                // SI la distancia  es mayor o menor a...      entonces...
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(6, HIGH);
  }
  if (distance >= 15 && distance <= 30) {                             // SI la distancia  es mayor o menor a...      entonces...
    digitalWrite(5, HIGH);
    digitalWrite(6, HIGH);
    digitalWrite(4, LOW);
  } else {                                                                                                       // si no ocurre nada de lo anterior entonces...
    digitalWrite(6, HIGH);
    digitalWrite(5, LOW);
    digitalWrite(4, LOW);
  }

ledVariable=map(distance,2,400,0,250); 
digitalwritte (2, ledVariable) // 13 és el pin

  Serial.println();
  digitalWrite(LED_BUILTIN, isNearby ? HIGH : LOW);
  delay(100);
}