Grand Idea Studio

RFID Reader Module


The Radio Frequency Identification (RFID) Reader Module provides a low-cost solution to read passive RFID transponder tags from up to 4 inches away.

The RFID Reader module can be used in a wide variety of hobbyist and commercial applications, including access control, user identification, robotics navigation, inventory tracking, payment systems, car immobilization, and manufacturing automation.

The module works exclusively with the EM Microelectronics-Marin SA EM4100-family of 125kHz, passive, read-only transponder tags. Each transponder tag contains a unique identifier (one of 240, or 1,099,511,627,776, possible combinations) that is read by the RFID Reader module.

Parallax, Inc. is the exclusive manufacturer of the RFID Reader module. It is available in two versions: Serial (1-wire, 2400 baud, TTL-level) or USB. For questions and technical support, contact

Module Highlights:

  • Serial TTL or USB interface
  • Requires single +5VDC supply (USB version is bus-powered, no external supply needed)
  • 3.25″ L x 2.45″ W
  • Bi-color LED for visual indication of activity

Documentation (from Parallax):

Additional Resources (Serial Version):

Additional Resources (USB Version):



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