int isObstaclePin = 3;  // This is our input pin
int isObstacle = HIGH;  // HIGH MEANS NO OBSTACLE

void setup() 
{
  pinMode(isObstaclePin, INPUT);
  Serial.begin(9600);
}

void loop() 
{
  isObstacle = digitalRead(isObstaclePin);
  
 if (isObstacle == LOW)
  {
    Serial.println("OBSTACLE!!, OBSTACLE!!");
  }
 else
  {
    Serial.println("clear");
  }
  delay(500);

}