RFID & NFC Modules

RFID and NFC modules read the ID from a card or tag held near them. That ID drives door locks, attendance registers and access-control projects.

The RC522 (MFRC522) is the common choice:

  • it reads 13.56 MHz tags over SPI;
  • the tags are passive, powered by the reader's field;
  • range is about 5 cm.

The RC522 runs on 3.3V only, and 5V will damage it. On a 5V Arduino, power it from the 3.3V pin and use a level shifter on the SPI lines. On an ESP32 it wires directly, because the pins are already 3.3V.

How to choose:

  • Pick the RC522 for 13.56 MHz cards, fobs and MIFARE tags.
  • Pick a 125 kHz reader for EM4100-style fobs.

One common surprise: 125 kHz tags (often EM4100 key fobs) will not read on the RC522. They need a 125 kHz reader such as the JT308 USB reader.

Frequently asked questions

Can I power the RC522 from 5V?

No. Use 3.3V, and a level shifter on the SPI data lines with a 5V board.

Why won't my key fob read?

It is probably a 125 kHz tag. The RC522 reads 13.56 MHz tags only; use a 125 kHz reader.

Which cards work with the RC522?

13.56 MHz MIFARE Classic cards and key fobs. 125 kHz EM4100 tags need a 125 kHz reader.

How far can it read?

The RC522 reads passive tags at about 5 cm.

Guides