read multiple RFID 14334A tags

[RMuiz.1]

What are the best chip/settings to read multiple RFID 14334A tags? What should I look at when selecting chip?

I need to create a reader that needs to read playing cards (14334A) from the table.

Currently, I have a setup with AS3910 chip. It works fine while 1-2 cards go through its field simultaneously.

1) First issue

If I stack one card on another it can read only up to 2 cards like that. When I stack 3 cards it can't.

2) Second issue

If cards (2-16) are in its field from the start it usually then can read just one card and sometimes more. (No idea why. Even if I leave the cards in the same place)

So I wonder what is responsible for these limitations? Is it the wrong settings, old chip, wrong protocol, or just the physical limitations of RFID technology?

Thanks!

[Grégoire Poulain · Accepted solution]

Hi,

We recommend to base your developments in a more recent NFC Reader such as ST25R3911B or ST25R3916. AS3910/ST25R3910 is obsolete and no longer in production.

The newer devices have more sensitive receivers and their settings/configurations have been greatly optimized and are supported via the RFAL library (STSW-ST25RFAL001 / STSW-ST25RFAL002)

Handling multiple tags is feasible but within reasonable physical limits.

Performing anticollision of a few tags is possible but there are factors that limit the amount of tags one single antenna can read, such as:

• Card placement - if the cards have the same antenna geometry and are perfectly aligned/stacked, it's likely that the antennas will cancel out making it hard for the reader to distinguish individual answers/collisions. Displacing the tags slightly will likely show detection of more tags.

• Loading effect - the more tags are placed in a single antenna, the more energy is harvested from the emitted magnetic field. It is possible the not all tags receive enough energy and therefore will not be able to answer the reader request.

• Settings/Procedure - Depending on the ST25R there are a few techniques that help increasing the chance to identify more tags during the anticollision procedure(AGC, anticollision procedure/flow, etc).

We encourage you to experiment with one of our ST25R demos and we can then assist you in further optimizations, if so needed.

Kind regards

GP