//ult-sensor
//v=(d/t)
//v=0.017cm/us
//d=v*t
//constants won't change
const int trigpin=6;
const int echopin=7;
const int led=3;
float duration;
float distance;

void setup() {
  Serial.begin(9600);
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);
  pinMode(led, OUTPUT);
  // put your setup code here, to run once:

}

void loop() {
  //generate 10 microseconds pulse to trigpin
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);
  //mesure duration of pulse from echopin

  duration = pulseIn(echopin,HIGH);
  //calculate distance

  distance = 0.017 * (duration/2);
  
  if (distance<10)
  digitalWrite(led, HIGH);
  else
  digitalWrite(led, LOW);
  
  //print the value to serial monitor
 Serial.print("distance:");
  Serial.print(distance);
Serial.print("cm");
delay(500);

}