#define trigger 6
#define echo 7

void setup() {

  Serial.begin(9600);
  pinMode(echo, INPUT);
  pinMode(trigger, OUTPUT);

}

void loop() {

  digitalWrite(trigger, LOW);
  delayMicroseconds(5);
  digitalWrite(trigger, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger, LOW);
  long duration = pulseIn(echo, HIGH);
  float cm = duration * 0.034 / 2;

  Serial.print("El objeto dista de: ");
  Serial.print(cm);
  Serial.println(" centímetros.");

  delay(500);

}