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); // เวลาus
    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);
}