125Khz RFID module - UART - (LED always on)

I received my : “125Khz RFID module - UART” yesterday in the mail.

I have it connected to an Arduino UNO, exactly how the photos are shown on the WIKI.

I am running the sample code from the WIKI.

The LED on ‘P3’ - is always on. It’s on with an antenna, without an antenna. ?
the serial output from the unit via the Arduino interface shows no data ever?

I’m speculating that their is something wrong with the hardware?

  1. Pin Definition (TTL interface RS232 data format):
    PIN1 TX
    PIN2 RX
    PIN4 GND
    PIN5 +5V(DC)
    PIN1 ANT1
    PIN2 ANT2
    PIN1 LED
    PIN2 +5V(DC)
    PIN3 GND

Signal LED stays on for - 125Khz RFID Card


Connect RX/TX to Arduino UART port , Uart demo code :

void setup()
void loop()

Hello ,

Glad to know that you are interested in this module. The LED port is always HIGH , it will be LOW only if at the moment that a 125kHz RFID card be read by RFID module. If it is always HIGH , only two possibilities , either the RFID Card is not work with this module , or there is something wrong with its hardware.


I have ordered some additional RFID 125 chips to test with, and an additional reader for my project. (different make/model than seed studio)


If the new reader works and reads all the chips - can we assume that the SEED Studio reader is faulty and can I get a replacement?

:blush: we are not the designer of this RFID module , just distribute it. While , as what we know , this module is work with some 125k RFID cards include the card sold in our store. We can not make sure that this module can read all of the 125k RFID card, because different card has different features such as some card with security protection.

Thanks for your understanding.