#define TRIGGER_PIN 18
#define ECHO_PIN 5
#define LED_PIN 23
#define BUZZER_PIN 32
float measureDistance(){
  digitalWrite(TRIGGER_PIN,LOW);
  delayMicroseconds(2);
  digitalWrite(TRIGGER_PIN,HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN,LOW);
  long duration = pulseIn(ECHO_PIN,HIGH);
  float distance = duration*0.034/2;
  return distance;
}
void setup() {
  pinMode(LED_PIN,OUTPUT);
  pinMode(TRIGGER_PIN,OUTPUT);
  pinMode(BUZZER_PIN,OUTPUT);
  pinMode(ECHO_PIN,INPUT);
  Serial.begin(9600);
}

void loop() {
  float distance = measureDistance();
  if (distance<50){
    digitalWrite(LED_PIN,LOW);
    tone(BUZZER_PIN,500);
  }
  else{
    digitalWrite(LED_PIN,HIGH);
    noTone(BUZZER_PIN);
  }
  Serial.print("Distance :");
  Serial.print(distance);
  Serial.println("  cm");
  delay(1000); 
}