RFID RDM6300 quetion

rdm630 rfid(3, 0);  //TX-pin of RDM630 connected to Arduino pin 6

The comments are ignored by the compiler. This one is, therefore wrong or meaningless. Fix incorrect comments are delete useless ones.

  if (conn.connect(srv_addr, 3306, user, password))
  {
     //delay(50);
     //declarar pines como salida
     pinMode(motorPin1, OUTPUT);
     pinMode(motorPin2, OUTPUT);
     pinMode(motorPin3, OUTPUT);
     pinMode(motorPin4, OUTPUT);
 //  pinMode(ledPin12,  OUTPUT);
     pinMode(ledPin13,  OUTPUT);
     pinMode(buttonI, INPUT_PULLUP);
     pinMode(buttonA, INPUT_PULLUP); 
     pinMode(sensorA, INPUT_PULLUP);
     Serial.println("DB connected :)");
  }
  else
  {
     Serial.println("DB Connection failed :(");
  }

Why does setting the mode of the pins depend on connecting to the database server?

You still need to post a link to the RFID you are using, and clarify your initial post. Does the device keep making data available while the card is held near the antenna, or not?

A link to the RFID library you are using would be good, too.