RC522 RFID/NFC Reader Module
Low-cost 13.56MHz RFID reader for access control, attendance, and authentication projects.
A low-cost SPI RFID/NFC reader operating at 13.56MHz, the go-to choice for DIY access-control and attendance-tracking builds. Built around NXP's MFRC522 chip, it reads (and writes) common Mifare-family tags and cards over SPI, letting a microcontroller check a scanned card's unique ID against a stored list to grant or deny access — the default entry point for anyone building an RFID door lock, attendance system, or simple tag-based authentication project.
Specifications
| Chipset | NXP MFRC522 13.56MHz RFID/NFC reader IC |
| Operating voltage | 3.3V DC (NOT 5V tolerant on SPI or logic pins) |
| Operating current | ~13-26 mA typical during read operations |
| Frequency | 13.56MHz |
| Supported tags | Mifare Classic 1K/4K, Mifare Ultralight, and other ISO/IEC 14443A compliant cards/tags |
| Read range | ~2.5-5cm typical, antenna and card dependent |
| Interface | SPI (also supports I2C/UART on the bare IC, but most breakout boards hardwire SPI only) |
| Included accessories | Modules commonly ship with a keychain tag and a card, both pre-programmed with unique IDs for testing |
Pinout
| Pin | Name | Description |
|---|---|---|
| 1 | 3.3V | Power, 3.3V DC only — do not supply 5V |
| 2 | RST | Active-LOW reset pin |
| 3 | GND | Ground |
| 4 | MISO | SPI data out |
| 5 | MOSI | SPI data in |
| 6 | SCK | SPI clock |
| 7 | SDA (SS/CS) | SPI chip select, active LOW (labeled SDA on the module despite being an SPI pin, a common source of confusion) |
| 8 | IRQ | Interrupt output, optional — signals when a card enters the field |
The pin labeled SDA on most RC522 breakout boards is actually the SPI chip-select line, not an I2C data pin — a frequent point of confusion for newcomers expecting I2C wiring. All logic pins are 3.3V only, so when wiring to a 5V Arduino Uno, use a logic-level shifter on MOSI, SCK, and RST (MISO can be safely read directly since the RC522 drives it).
Variants
The RC522 is the right default for a simple, budget-friendly tag-based access-control project. Step up to the PN532 only if the project needs card emulation or phone-to-device peer-to-peer NFC; the RDM6300 is a different frequency band entirely and only relevant if you specifically already have 125kHz tags.
| Variant | Temp range | Hum range | Accuracy | Protocol | Price |
|---|---|---|---|---|---|
| RC522 breakout (SPI) | ~$1-3 | ||||
| PN532 | ~$8-15 | ||||
| RDM6300 (125kHz) | ~$2-4 |