But for those who fancy experimenting with the format it’s still possible to make a basic card reader using LEDs and light sensors, as [Nino Ivanov] has done using an Arduino Uno as the brains.

Meet the Arduino Compatible RFID Reader Module. It can hold card data for up to five cards, takes seconds to program, and holds card data in EEPROM memory, which means that the cards are saved ...

The Arduino talks to a USB card reader using a USB host shield. Then it communicates with the PLC using an RS232 link and the DF1 protocol that most Allen Bradley PLCs understand.