int obstacle = 2;
int buzzer = 13;
void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
pinMode(buzzer , OUTPUT );
}

void loop() {
  // put your main code here, to run repeatedly:
int value = digitalRead(obstacle);
Serial.println(value);
if(value == 1)
{
  Serial.println("OBSTACLE DETECTED...!!!");
  digitalWrite(buzzer , HIGH);
  delay(2000);
}
else
{
  Serial.println("OBSTACLE NOT DETECTED...!!!");
  digitalWrite(buzzer , LOW);
  delay(2000);
}
}
// usig ir sensor
//requires two sensors one is transmitter and another is receiver.