#define echo 7
#define trigger 8
#define led 9

unsigned int duration = 0;
float distance = 0;

void setup()
{
  pinMode(led , OUTPUT);
  pinMode(echo , INPUT);
  pinMode(trigger , OUTPUT);
  Serial.begin(9600);
}

void loop()
{
  digitalWrite(trigger , HIGH);
  delayMicroseconds(10);
  digitalWrite(trigger , LOW);
  duration = pulseIn(echo, HIGH);
  distance = duration * 0.017175;
  Serial.print("Distancia: ");
  Serial.print(distance);
  Serial.println("cm");
  delay(1000);
  if (distance >= 50 &&  distance <= 115)
  {
   digitalWrite(led, HIGH);
  }
  else
  {
   digitalWrite(led , LOW);
  }
  if ( distance >= 115)
  {
   digitalWrite(led,LOW);
  }
}