int trigPin = 3;
int echoPin = 2;
int led = 13;

double duration;
int distance;


void setup() {
  pinMode(led, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
}
void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);


  duration = pulseIn(echoPin, HIGH);
  distance = duration * 0.034 / 2;
  Serial.print("Distance: ");
  Serial.println(distance);
  if(distance < 100){
    digitalWrite(led, HIGH);
  }else{
    digitalWrite(led, LOW);
  }
}