How to Make Security System using Arduino Nano and Ultrasonic Sensor

Arduino code for Security System using Arduino Nano and Ultrasonic Sensor

int trigPin = 10;
int echoPin = 11;
int Buzzer = 12;


void setup() {
  Serial.begin(9600);
   pinMode(Buzzer, OUTPUT);
   pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  // put your setup code here, to run once:

}

void loop() {
  long duration, distance;
  digitalWrite(trigPin,HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration=pulseIn(echoPin, HIGH);
  distance =(duration/1)/29.1;
   duration=pulseIn(echoPin, LOW);
  Serial.print(distance);
  Serial.println("cm");
  delay(10);

 if((distance<=15))
  {
    digitalWrite(Buzzer, HIGH);
}
   else if(distance>15)
 {
     digitalWrite(Buzzer, LOW);
   }
}