solved

Some of the RC-522 RFID card reader modules that can be bought on ebay / aliexpress have a problem: they do not read all (types of) cards they should be able to read. In this blog post I want to explain how to recognize these faulty readers and how to fix them. (There is a more detailed post in Dutch)

rfidadvertentiefoto
RC522 module (picture source: generic advertisement)

Choosy Cardreaders

Lets start at the beginning:
At MakerSpace Leiden those RFID-RC522 card readers are used in the access-system and AC-node system. Participants of the MakerSpace can scan their cards to get access to the MakerSpace (access system) or to enable power to heavy machinery that requires training (After completing the training ; AC-node system).

Most use their OV-chipkaart. (Public transport card, Oyster card for UK readers).

The problem that surfaced is that some of the RC522 card readers won’t read some cards (Including the OV-chipkaart).

That’s obviously a problem when the door won’t open or the machine won’t start, or your project using those card readers doesn’t work with all the cards it should be working with.