float distance;
float distanceThreshold;
int trigPin;
int echoPin;
int ledPin;

void setup() {

  Serial.begin(115200);

  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledPin, OUTPUT);
  
}

void loop() {
 digitalWrite(trigPin, LOW);
  delay(2);

  digitalWrite(trigPin, HIGH);
  delay(10);
  digitalWrite(trigPin, LOW);

  long duration = pulseIn(echoPin, HIGH);

   if (distance < distanceThreshold) {
    digitalWrite(ledPin, HIGH);
  } 
  
  else {
    digitalWrite(ledPin, LOW);
  }
  delay(500);

}