RFID for bird identification

Which RFID technology to use?

LF, HF or UHF?

Available products only in LF/HF. Example here.

UHF for animal tagging is only in pre-study phase. –> no benefit for us at the moment, but looking in the future, it may be beneficial (eg. for measuring more data of bird while they are away).

A first prototype was realised using HF reader and tags. Being one of the cheapest dev kits, we chose the CR95HF resp. ST95HF from ST.

Range problems as well as unsolved hardware issues (code execution would crash after a certain number of read cycles; power cycling the board does not help restoring functionality for at least 24 hours.) led to the decision to switch to an LF-based system.

Final Choice: LF (125 kHz)
  • standard in animal tracking
  • higher range possible (due to higher current & magnetic field)
  • cheap components

Reader

Trials with MLX90109

The read range is not sufficient, because of parallel L-C configuration (and therefore low voltage on antenna –> low current –> weak magnetic field).

Lessons learned along the way
  • The MODE pin which - when left floating - makes that the chip doesn't decode the tag information MUST BE TIED TO GND OR VDD VIA 0 OHM, if decoding (in manchester or biphase) is desired. Using pull-up/down resistors, especially high-ohmic (100k) ones will make the pin seem floating!

Final Choice: EM4095

PCB