//scinario:Design contact less Calling Bell using Ultrasonic Sensor
int trigPin=10;
int echoPin=11;
int buzzerPin=12;
void setup() {
  // put your setup code here, to run once:
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
pinMode(buzzerPin, OUTPUT);
Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
long duration,distance;
// Clear the trigger pin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  
  // Send a 10us pulse to the trigger pin
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  // Measure the duration of the pulse on the echo pin
  duration = pulseIn(echoPin, HIGH);
  
  // Calculate the distance in centimeters
  distance = duration * 0.034 / 2;

  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
   Serial.println(" cm");

  // Check if someone is close (within 50 cm) and trigger the buzzer
  if (distance < 50) {
    tone(12,262,1024);
    delay(500); // Buzzer ON time (adjust as needed)
    // tone(buzzerPin, LOW);
    // delay(2000); // Buzzer OFF time (adjust as needed)
  }
  
  else
  {
    
     tone(12,262,250);
     delay(2000); // Buzzer OFF time (adjust as needed)

}
}