#define pinecho 2
#define pintrig 15
#define pinlamp 13
#define pinbuzz 4


void setup() {

  Serial.begin(115200);
  pinMode(pinecho, INPUT);
  pinMode(pintrig, OUTPUT);
  pinMode(pinbuzz, OUTPUT);
}

void loop() {
  digitalWrite(pintrig, LOW);
  delayMicroseconds(2);
  digitalWrite(pintrig, HIGH);
  delayMicroseconds(10);
  digitalWrite(pintrig, LOW);
  int duration=pulseIn(pinecho, HIGH);
  float distance=duration*0.034/2;

   Serial.print(distance);
  Serial.println("cm");
  delay(1000);
  if(distance<=30)
  {
    
        tone (pinbuzz , 400,1000 );
  }
  else if(distance>30){
   digitalWrite(pinbuzz,LOW);
 
  }
     
  }