int DISTANCIA = 0;
int pinLed=2;
int pinEco=12;
int pinGatillo=13;
long readUltrasonicDistance(int triggerPin, int echoPin)
{
  pinMode(triggerPin, OUTPUT);
  
  digitalWrite(triggerPin, LOW);
  
  delayMicroseconds(2);
 
  digitalWrite(triggerPin, HIGH);

  delayMicroseconds(10);
 
  digitalWrite(triggerPin, LOW);

  pinMode(echoPin, INPUT);
  
  return pulseIn(echoPin, HIGH);
}

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

void loop() {
 
  DISTANCIA = 0.01723 * readUltrasonicDistance(pinGatillo, pinEco);

  Serial.println(DISTANCIA);

  if (DISTANCIA < 20) {
    digitalWrite(pinLed, HIGH);
  } 

  else {
    digitalWrite(pinLed, LOW);
  }
  delay(10);
}