const int relay  = 11 ;
const int trigPin = 9 ;
const int  echoPin = 10 ;
const int buzzer = 12 ;

long duration;
int distance;

void setup ( )
{
  pinMode(relay, OUTPUT);
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(buzzer, OUTPUT);
  Serial.begin(9600);
}

void loop ( )
{
  digitalWrite (trigPin, LOW);
  delay(20);
  digitalWrite (trigPin, HIGH);
  delay (10);
  digitalWrite (trigPin, LOW);

  duration = pulseIn(echoPin, HIGH);
  distance = (duration * 0.0343) / 2;

  if (distance <= 6)
  {
    digitalWrite (relay, HIGH);
    delay(10000);
    digitalWrite (relay, LOW);
    tone(buzzer, 2600);
    delay(2500);
    noTone(buzzer);
    digitalWrite (relay, LOW);

  }
  else
  {
    digitalWrite (relay, LOW);
  }
  Serial.print("Distance:");
  Serial.println(distance);
}