int LEDpin = 13;
int trigPin = 11;    // Trigger
int echoPin = 12;    // Echo
long duration, cm, inches;
 
void setup() {
  Serial.begin (9600);
  //Define inputs and outputs
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
}
 
void loop() {
  // The sensor is triggered by a HIGH pulse of 10 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  digitalWrite(trigPin, LOW);
  delayMicroseconds(5);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
 
  cm = (duration/2) / 29.1;     // Divide by 29.1 or multiply by 0.0343
 
  Serial.print(cm);
  Serial.print(" cm");
  Serial.println();

  if (cm >= 120) {
  digitalWrite(LEDpin,HIGH);
  }
  else {
  digitalWrite(LEDpin,LOW);
  }

}