Hello there,
I would like to design my own RFID Tag 125 kHz reader and programmer, for example to read my own tag and then make a copy (like a clone) to another tag...


I know these devices are available on the market, but I want to make it by myself from the schematics, and learn along the way.
Can someone send a schematic for such a device, and is it complicated to develop the PCB at home ?
Thank you.

 

WHY??? And for what purpose???

 

WHY??? And for what purpose???

For educational purpose only...

 

https://media.melexis.com/-/media/files/documents/datasheets/mlx90109-datasheet-melexis.pdf

 

https://media.melexis.com/-/media/files/documents/datasheets/mlx90109-datasheet-melexis.pdf

THANK YOU.

 

…is it complicated to develop the PCB at home ?

If you haven’t done it before, designing boards for RF applications can be very frustrating. Impedance matching is a critical performance factor and things like trace width, length, and spacing; stackup, board material choices; and other things can affect it. The criticality is proportional to frequency and you’ll find that kHz are much easier than MHz, and GHz is like a different world.

A good manufacturer will have application notes on PCB design. Follow it very carefully. It’s best to start with the reference design if they offer one.

 

@hsazerty2 you are welcome!! I'll admit I just kind of skimmed through it, but it looked like a good starting point at least.

 

this should make it very simple, just few parts are needed and you can use MCU or development board of your choice:
https://www.mouser.ca/datasheet/2/302/037031-3137933.pdf

of course you can also find other people making their own. here is someone just making reader:
https://www.serasidis.gr/circuits/RFID_reader/125kHz_RFID_reader.htm

 

https://media.melexis.com/-/media/files/documents/datasheets/mlx90109-datasheet-melexis.pdf

There is an evaluation board for this melexis chip and the datasheet includes schematic, part values, and details of a suitable coil.
https://www.melexis.com/en/documents/documentation/user-manuals/user-manual-evb90109

 

Over what carrier frequency range will a 125kHz tag be correctly read?
I have not been able to find any spec for this.

 

Over what carrier frequency range will a 125kHz tag be correctly read?
I have not been able to find any spec for this.

This is an interesting question that I have not seen much discussion about. Some of the systems resolve that issue by re-modulating the signal sent by the interrogating system, so that the reply is always on frequency. For most systems the assumption is that there will not be much interference from other signals, and so the receiver selectivity can be rather broad.
For most RFID tag systems, the tags are mass produced and it makes sense that quality control would accept only those units within some frequency tolerance range. And smart production control should be able to correct any detected drift.
Of course, hand built tag devices will not be as uniform as those produced on a single fully automated machine using reasonably high quality parts.