ShillehTek RFID Key Fob S50 Manual

Overview

This 13.56MHz RFID key fob is a compact, durable access token based on the NXP MIFARE Classic S50 (1K) chip — the most widely supported HF card type in hobby electronics and commercial access control. Hang it on a keyring, tap it against a reader, and your code sees a unique 4-byte UID in milliseconds.

It works out of the box with any ISO/IEC 14443A-compatible reader, including the popular RC522, PN532, and MFRC522-based modules used with Arduino, Raspberry Pi, ESP32, and the Pico. The chip holds 1KB of readable/writable memory split into 16 sectors — ideal for UID-based door locks, attendance systems, makerspace entry, and cloneable card experiments.

At a Glance

Frequency

13.56 MHz (HF)

Standard

ISO/IEC 14443A

Chip

MIFARE Classic S50

Memory

1 KB (16 sectors)

UID Length

4 Bytes

Form Factor

Keychain Fob

Specifications

Parameter	Value
Operating Frequency	13.56 MHz
Standard	ISO/IEC 14443 Type A
IC Chip	NXP MIFARE Classic S50 (1K)
Memory Capacity	1 KB EEPROM, 16 sectors × 4 blocks × 16 bytes
UID	4 bytes, factory-programmed, unique
Data Rate	106 kbit/s
Read Range	Up to ~5 cm (reader dependent)
Write Endurance	100,000 cycles
Data Retention	10+ years
Housing	ABS plastic with keyring hole
Power	Passive (energy harvested from reader's field)
Operating Temperature	-20°C to +55°C

How to Use

The key fob is passive — there's nothing to wire, solder, or power. Pair it with a 13.56MHz reader module such as an RC522 or PN532, and your microcontroller will see the fob's UID the instant you hold it within a few centimeters of the reader's antenna.

For a typical project: hook up your reader to Arduino/Pi/ESP32, run a library-provided "read UID" example sketch, and tap the fob to the reader. The UID prints to the serial monitor and you can match it against a whitelist of authorized tokens to gate an action — unlock a door, log attendance, trigger a relay, and so on.

Tip: Store the UID of each authorized fob in a simple array in your firmware. On every scan, compare the read UID against the list — a fast, reliable pattern for small-scale access control without needing a database.

Works with: RC522, MFRC522, PN532, PN5180 and any other ISO 14443A reader module. Libraries like MFRC522 (Arduino), mfrc522 (MicroPython), and pi-rc522 (Raspberry Pi) work out of the box.

Different from 125kHz tags: This is a 13.56MHz (HF) fob and will NOT be read by a 125kHz (LF) reader like the RDM6300 or EM4100-only systems. Match the frequency of your reader to the frequency of your tag.

Frequently Asked Questions

Does this work with the RC522 module?

Yes — this is the canonical card/fob type the RC522 is designed to read. Any standard RC522 example sketch will detect this fob and return its UID within a few centimeters of the antenna.

Can I change the UID?

No. The UID on genuine MIFARE S50 chips is set at the factory and locked. For UID-changeable cards (commonly used for cloning experiments), look for "magic" or "Chinese clone" S50 UID cards — a different SKU.

How do I use it with a Raspberry Pi?

Use an RC522 reader over the Pi's SPI bus, install the pi-rc522 or mfrc522 Python library, and run a "read UID" example. Tap the fob near the reader's coil and the UID prints to the console.

What's the maximum read distance?

About 2–5 cm with a standard RC522 antenna. Larger or tuned antennas can reach 10 cm, but HF RFID is fundamentally short-range by design — that's what makes it secure.

Can I write data to the 1KB of memory?

Yes. Each of the 16 sectors has 3 writable blocks (48 bytes per sector minus the authentication block). Libraries like MFRC522 expose MIFARE_Read and MIFARE_Write methods to read and write sector data after authenticating with the correct key.

Will it work with my phone's NFC reader?

Yes. Most Android phones (and recent iPhones) can read MIFARE Classic UIDs via apps like "NFC Tools" or "MIFARE Classic Tool." Handy for quickly grabbing a fob's UID without a separate reader.

Documentation

ShillehTek 13.56MHz RFID Key Fob Tag IC S50 Token ISO14443A Access Control | ShillehTek Product Manual