void setup()
{
  Serial.begin(115200);
  pinMode(2,OUTPUT); //Trig
  pinMode(3,INPUT); //Echo
  pinMode(13,OUTPUT); //LED
}
void loop()
{
  digitalWrite(2,0);
  delayMicroseconds(2);
  digitalWrite(2,1);
  delayMicroseconds(5);
  digitalWrite(2,0);

  int T = pulseIn(3,1); //ค่าเวลา us
  float D = T/58.0;

  Serial.println(D);
  if(D < 10)
  {
    digitalWrite(13,1);
  }
  else if (D < 25)
  {
    digitalWrite(13,1);
    delay(200);
    digitalWrite(13,0);
    delay(200);
  }
  else if(D < 40)
  {
   digitalWrite(13,1);
    delay(400);
    digitalWrite(13,0);
    delay(400); 
  }
  else 
    digitalWrite(13,0);
  delay(100);

}