#define TRIG 8
#define ECHO 9
#define  buzzer 13
#define led 2
#define DISTANCE_LIMIT 50
float duration_us,distance_cm;

void setup() {
 pinMode(buzzer, OUTPUT);
 Serial.begin(9600);
 pinMode(led, OUTPUT);
 pinMode(TRIG, OUTPUT);
 pinMode(ECHO, INPUT);
}

void loop() {
digitalWrite(TRIG, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG, LOW);
duration_us=pulseIn(ECHO,HIGH);
distance_cm=0.017*duration_us;
if(distance_cm< DISTANCE_LIMIT){
  digitalWrite(led, HIGH);
  digitalWrite(buzzer, HIGH);
  tone(buzzer,1000,1000);}
else
  digitalWrite(led, LOW);
  digitalWrite(buzzer, LOW);

  
  Serial.print("DISTANCE:");
  Serial.print(distance_cm);
  Serial.println("cm");
  delay(500);



  
}