MFRC522 from Ebay - tips how to get more RF power

[ermok]

Hi,

I'm sharing information how to get more rf power from china made rc522 board.
My project uses MFRC522 board and Mifare Ultralight C cards.
This board can not produce enough RF energy to get Ultralight C card up and running
MFRC522 datasheet says that max TX current is 150mA, but measured current was only 7mA.
I have a very good RF design experience so I started to measure whole RF part and make full tuning.
And what I found, antenna is tuned, not perfectly but usable, so was matching cirquit. But used 2.2uH
inductors does not meet with required parameters.
Solution: Replace inductors L1 and L2 with same inductance (2.2uH) but higher operating current.
like this one: http://www.tme.eu/en/details/cw1008-220 ... ferrocore/
Now RC522 can read Ultralight C cards with no problem, also NTAG203 card reading distance is ~70mm


WARNING!!
RC522 RF output pins are very static sensitive!
Without proper equipment you can easly
damage your rc522 reader board!!

[filip]

Hi,

Thank you for sharing this

Regards,
Filip.

[sergiosider]

Hi Ermok

Thank you for your tip on the inductor.

I was having the same problem. By the way, what other values (capacitors) did you find to obtain the correct tuning? I got several boards from ebay/amazon that has different values...

Would you give us the best values for the capacitor pairs (I had 47pF C4/C5, 10pF for C10/C11, 180pF for C8/C9 and 15pF for C6/C7)

Regards,
Sergio P. SIder

[ermok]

Hey,

I made some tests with sweep and figured out that coil has good parameters.
Not perfect in first moment, but checking working bandwidth ~800KHz I found that
resonanze frequenct is correct and not need a fine tuning. But harmonic and matching circuit
needs to be tuned. Lot of work, several tests and after building a completly new
measurement equipment based on 40MHz DDS and 90db logaritmic detector I figured out that
C4 and C5 must be changed. Replace them with 33pf capacitors. And that's it.

[gugui]

Wow, thanks for sharing this information. By the way, does anybody have the board routing file (or gerber) of this board ? I would like to integrate its design in a more complex project and I'm not able to design the antenna and tune capa/resistor by myself

[gomjabar6]

Thanks for the tip!
After replacing L1 and L2 on my $5 RC522 reader from Amazon, it can now read Ultralight C and Desfire EV1 cards at about 3cm.
Before it was not able to read these cards at all.

FYI for those of you in the USA like me, these are the Inductors that I used:
http://www.mouser.com/search/ProductDet ... 479887222C
They fit just fin on the existing pads and look much beefier!

[danogeorge]

Hi there,

I'm trying to rebuild the device - Petsafe Petporte cat flap. Is it possible to use Arduino Pro with the RC522? I was planning to attach the Petporte device's RFID antenna to the RC522. Will the range of the RC522 be enough? Will it work? Thanks.

Dano

[danogeorge]

Previous visited page: extend range for MFRC522 RFID reader and essay writer projects
Hi there,

I'm trying to rebuild the device - Petsafe Petporte cat flap. Is it possible to use Arduino Pro with the RC522? I was planning to attach the Petporte device's RFID antenna to the RC522. Will the range of the RC522 be enough? Will it work? Thanks.

Dano

Update: I found the topic on Arduino forum too: https://forum.arduino.cc/index.php?topic=199983.0

Dano

[luz]

Hi @Ermok,

It's more than seven years past - but I still want to thank you very much for your post, which was a real project saver for me!

The story: for an interactive exhibition I built a system using hundreds of those MFRC522 boards (for a while now, available for around $0.80 a piece), in 2020. It worked fine, so I used the same system again now, in 2023. As I did not have enough readers in stock, I re-ordered 200 more from the same supplier. As they exactly look the same as those from 2020, I first was not even aware of a difference when I suddenly noticed half of the almost finished installation only responded sometimes, sometimes not. I spent days in checking the software drivers suspecting a subtle bug there, until I finally found out that the old readers from 2020 work fine, while the new ones don't. Of course, this happened less than a week before the exhibition starts, and I was desperate because I had no idea what was wrong with the newer readers.

So finding your post and reading that it's just bad quality L1 and L2 inductors was a great relief! I immediately orderd replacement Ls (TDK MLZ1608N2R2LTD25, digikey https://www.digikey.ch/de/products/deta ... 25/4743178), which arrived today and - YES! - this reliably fixes the problem!

What I also found - the cards for the exhibition are MiFare Classic ones, but I had also one MiFare Ultralight lying around. The readers with the bad inductors work with the Ultralight card in near distance (2-3cm), but definitely don't with Classic cards, at any distance. I guess the Ultralight (non C) needs less power than the classic.

So again - thank you very much!

luz

BTW: my software that drives those RFIDs (among a lot of other things, in particular SmartLED lighting stuff), up to 24 readers connected to a RPi or Omega2 is all OpenSource (the rfids "feature" is a part of the "vdcd" https://github.com/plan44/vdcd

Hi,

I'm sharing information how to get more rf power from china made rc522 board.
My project uses MFRC522 board and Mifare Ultralight C cards.
This board can not produce enough RF energy to get Ultralight C card up and running
MFRC522 datasheet says that max TX current is 150mA, but measured current was only 7mA.
I have a very good RF design experience so I started to measure whole RF part and make full tuning.
And what I found, antenna is tuned, not perfectly but usable, so was matching cirquit. But used 2.2uH
inductors does not meet with required parameters.
Solution: Replace inductors L1 and L2 with same inductance (2.2uH) but higher operating current.
like this one: http://www.tme.eu/en/details/cw1008-220 ... ferrocore/
Now RC522 can read Ultralight C cards with no problem, also NTAG203 card reading distance is ~70mm


WARNING!!
RC522 RF output pins are very static sensitive!
Without proper equipment you can easly
damage your rc522 reader board!!

[rexxic]

It's amazing how this still works!

Implementing the modifications, I achieved even supplying MifareDesfireV2 chips with enough current to read their ID at about half a centimeter distance from the reader. It was insane, how sparse informations have been on using these in combination with the rc522. I haven't tested if it is sufficient to access the encryption features of the chips, i don't need them for my project and reading the id can be easily done with the standard rc522 libraries.

The switching of the inductor was the key, i tested both the high-resistance and low-resistance types used in the previous responses (https://www.tme.eu/de/en/details/mlp201 ... ctors/tdk//https://www.tme.eu/en/details/cw0805-22 ... ferrocore/). Both are big improvements and it feels like the low-resistance one extends the range a little bit but a higher gain improvement can be achieved switching to the 33pF capacitors.

Another modification that helped but where i dont't know if it is specific to my usecase using MifareDesfireV2 cards and the relatively weak raspberry pi 3 b 3.3V power rail was removing R1. This disables the LED located at D1 and also improve the range of the reader a lot.

Furthermore, you can mod registers of the rc522 in software also improving the antenna gain:
- Impendance of p driver via CWGsPReg and ModGsPReg, both need to be set to 111111, which is their highest value
- Impendance of n driver, set by GsNReg, 11111111 is here the highest value.

Code: Select all

reader = MFRC522()
reader.Write_MFRC522(reader.CWGsPReg, 0b111111)
reader.Write_MFRC522(reader.ModGsPReg, 0b111111)
reader.Write_MFRC522(reader.GsNReg, 0b11111111)

The improvements other than changing the inductors and removing the led from the circuit weren't that important. But if you need every millimeter for reaching through a plastic wall like me, this is how to max the gains out. The newer boards from AZ-Delivery I used use 0603 size smd components and soldering the 0805 size components to them was tricky but possible.

[pmbata@gmail.com]

Code: Select all

CODE: SELECT ALL

reader = MFRC522()
reader.Write_MFRC522(reader.CWGsPReg, 0b111111)
reader.Write_MFRC522(reader.ModGsPReg, 0b111111)
reader.Write_MFRC522(reader.GsNReg, 0b11111111)

Where would I put this code in the main code? Also, I changed C4 and C5 to 33pF capacitors, L1 and L2 to 2.2uH inductors, and removed R1 but the range is still the exact same. I also set the gain to 0x07. Any ideas? I'm just trying to get 8 more centimeters.

[rexxic]

Hi @pmbata, if your using the MFRC522 library look for

Code: Select all

... = MFRC522()

and put the write calls right behind, changing the variable name to whatever it is called in your code. But i think extending the range to 8cm is impossible. I achieved 1 cm distance with mifare desfire chips starting from not able to read the chip at all and about 3 cm with the mifare classic chip with an initial 5 mm if i remember this correctly. But this values are with just air in between, depending on the material and its thickness between the chip and the reader something like plastics might only impact the range slightly but metals for example can block the signal with just some mm in between.