void setup() {
  pinMode(ir,INPUT);
  pinMode(led,OUTPUT);
  pinMode(buzzer,OUTPUT);
}
void loop(){
  obstacle=digitalRead(ir);
  if(obstacle==LOW);
  {
    digitalWrite(led,LOW);
    digitalWrite(buzzer,HIGH);
  }
  else
  {
    digitalWrite(led,HIGH);
    digitalWrite(buzzer,LOW);
  }
}