     if (!is_hand) {
       is_hand = true;
       Serial.println("ON");
+      digitalWrite(led, HIGH);  
     }
     Serial.print("->");
     Serial.println(distance);

     if (is_hand) {
      is_hand = false;
      Serial.println("OFF");
    }
  }    
  int loop_delay = LOOP_LENGTH - (time - millis());

const int LOOP_LENGTH = 50;

int distance;
int led = 13;
boolean is_hand = false;
unsigned long time;
unsigned long loop_delay;
