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Implanting a barcode scanner/NFC/RFID reader

  1. Jul 10, 2017 #1
    Hey there,
    Let me give you some background;
    I have PCB at around the size of 1.8cm X 6 cm , on this board I need to implant a reader (up to me which type - NFC/Barcode/Rfid/Any kind of optical identification) that can identify a signal 0.5cm away.
    At first I thought using NFC is the best solution, however the antenna seems too large in my case as I dont have the spacing.
    What should I do? Lets assume at this moment that pricing is not the problem.

  2. jcsd
  3. Jul 10, 2017 #2


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    welcome to PF :smile:

    is the reader ( whichever type) the only thing on this small board
    how much of the reader can be on the board and how much situated elsewhere
    that is .... just the sensor on the board or the whole reader system ?

    physical size limitations may be a much bigger challenge than price
  4. Jul 10, 2017 #3
    It'll be Rfid then. For that the reader size is a tradeoff for sensitivity//read distance: for 0.5cm distance you can get pretty small modules ready.
  5. Jul 10, 2017 #4
    There are alot more parts on the PCB; optical sensor, noise filter and such.
    I am sort of trying to get a grip on what sizes are we talking about to conclude if this is even possible.

    I can add additional parts on the main board which 2.5meters away (cable).

    Thanks again for the super quicky response.
  6. Jul 10, 2017 #5


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    got a link to something tiny that you had in mind ?

    you may have to .... lets see if rive has something suitable in mind :smile:
  7. Jul 10, 2017 #6
    Thanks for being so helpful!
  8. Jul 10, 2017 #7
    Well, if the width is really so stritch then maybe this: https://shop.sonmicro.com/SM125-M1
    For this external antenna coil is needed, but the requirements are easy to met. Can be used as module or chip, so it'll fit.

    If there is some more space then the good old EM-18 which contains everything for that distance.
  9. Jul 11, 2017 #8
    Hey Rive,
    Thanks for the support on this matter.
    I have few more questions;
    I am not sure what kind of external antenna is needed, I mean the size of it is probably related to the distance that is needed so it should be small (hopefully). How should I choose the right one? Also, is it a good idea to place only the antenna on the smaller board, and the SM125 on the larger PCB - I am not really sure how problematic will the attenuation/noise be if the larger PCB is around 2.5meters away.
    I am really not too familiar with RF so any help would be extremely useful.
  10. Jul 11, 2017 #9
    125kHz is not a big frequency, but 2.5m is out of spec anyway. You should put the module and the coil close to each other.

    If you check the IND125 coils there (IND125-3 might be OK for you if you don't want to make one for yourself), you will see that the requirement is 860uH 10-12Ohm. That's all.
    You have to find an online calculator for coil inductance/resistance, then pick a suitable size and calculate the turns. At the target distance it won't be really sensitive for quality, so you are free to do some experiments.
  11. Jul 11, 2017 #10
    So if the antenna is 2.5 meters away from the module, nothing is going to work.
    Well the module is 1x1.7 cm^2 and the antenna is 4.2x1.8 cm^2 so I'm not really sure how can I squeeze this whole thing together. Is looks like it might just not work.
    I guess any other solution is custom?
  12. Jul 11, 2017 #11
    The antenna won't interfere with the circuit, so you can put it on top of the module, for example.
    Ot you can glue it on to the box if there is some room (guess it's not a project to be presented as bare PCB?).
    The whole system is surprisingly insensitive to creativity...

    Ps: you said you have something like 18*60mm or so? Stack up the coil and the module then.
  13. Jul 11, 2017 #12
    Well in theory I, but when taking into account that there are few more parts other then the PCB on the board (I haven't measured exactly, just trying to get a figure on things).
    Yeah, this is indeed a time for creativity.
  14. Jul 17, 2017 #13
    Hey there,
    Well it seems like the parts cannot fit to my design properly.
    I was wondering; Is it possible to create some sort of a degrading circuit (instead of a readable barcode), that if a very low current passes through it for X amount of time, it stops working. Maybe even a magnetic field that depolarizes another magnetic field on a disposable unit.
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