int LED=2;
int trigPin=13;
int echo=12;
long duration, cm;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  pinMode(echo, INPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(LED, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
digitalWrite(trigPin, LOW);
delayMicroseconds(5);
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
pinMode(echo, INPUT);
duration=pulseIn(echo, HIGH);
cm=(duration/2)*0.0343;
if(cm<40){
  digitalWrite(LED, HIGH);
  Serial.print("LED on=");
}
else
{
  digitalWrite(LED,LOW);
  Serial.print("LED off=");
}
Serial.print("Distance value in cm: ");
Serial.println(cm);
delay(5000);
}