int trigger = 12;

int echo = 13;

int led = 8;

long duration = 0;

int cm = 0;

int inch = 0;

void setup() {

  // put your setup code here, to run once:

  Serial.begin(9600);

  pinMode(trigger, OUTPUT);

  pinMode(echo, INPUT);

  pinMode(led, OUTPUT);

}

void loop() {

  // put your main code here, to run repeatedly:

  digitalWrite(trigger, LOW);

  digitalWrite(trigger, HIGH);

  digitalWrite(trigger, LOW);

  duration = pulseIn(echo, HIGH);

  cm = duration*0.034/2;

  inch = duration*0.0133/2;

  if (inch < 50){

    digitalWrite(led, HIGH);

  } else {

    digitalWrite(led, LOW);

  }

  if (inch < 100 ) {

    Serial.print("Inches: ");

    Serial.println(inch);

    Serial.print("Cm: ");

    Serial.println(cm);

  }

  delay(500);

}