Two NFC (contactless) cards in one holder?

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awneil
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Posted by awneil: Wed. Apr 7, 2021 - 08:39 PM
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Something like this:

https://www.lanyardstomorrow.co.uk/en/twin-sided-vertical-coloured-plastic-rigid-badge-id-credit-card-holder.html

 

It takes 2 cards - one each side; "back-to-back"

 

Would that work?

 

Or would the reader get confused with 2 cards being presented at the same time? I  suspect this would be the case.

 

They would both be NFC cards, but one a "payment" card, and one an "id" card.

 

(I don't think this is the intended application of the holder; I think it's just meant for visual inspection)

 

Thinking of this for an elderly person who finds it difficult to get cards (bus pass, payment card) out of & back into a wallet (due to no-longer-nimble fingers) to present to the reader.

 

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jgmdesign
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Posted by jgmdesign: Wed. Apr 7, 2021 - 08:47 PM
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It depends on teh cards.  If one is 125khz and the other 13.5MHz then it should be no problem.  But if they are both the same technology then no, it would not work.

 

JIm

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Kuch
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Posted by Kuch: Thu. Apr 8, 2021 - 12:38 AM
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Put one of those RFID blocker sleeves in between the cards. Then both should work

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jgmdesign
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Posted by jgmdesign: Thu. Apr 8, 2021 - 01:45 AM
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Kuch wrote:
Put one of those RFID blocker sleeves in between the cards. Then both should work

Not necessarily. 

125KHz has very good read range and if both cards are 'exposed they will both respond to teh field created by the reader.  13.5MHz probably would do the same thing.

 

Jim

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valusoft
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Posted by valusoft: Thu. Apr 8, 2021 - 04:22 AM
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awneil wrote:
Thinking of this for an elderly person
Today's world has not been made for the elderly.

Ross McKenzie ValuSoft Melbourne Australia

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Bronze Markjs
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Posted by js: Thu. Apr 8, 2021 - 04:32 AM
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Who's elderly? Apparently one is elderly at about 55-60? Is 70 ancient? What about 80 etc.?

John Samperi

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valusoft
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Posted by valusoft: Thu. Apr 8, 2021 - 04:34 AM
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I am in the "1b" group for the C-19 vaccine. Got my first jab last month.

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awneil
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Posted by awneil: Thu. Apr 8, 2021 - 07:39 AM
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Kuch wrote:
Put one of those RFID blocker sleeves in between the cards

I had thought of that, but had the same misgivings as Jim.

 

I guess it might depend on the reader: a reader only expecting a payment card might ignore the "id" card; a reader only expecting an "id" card might ignore the payment card ... ?

 

Simple solution, of course,  is to just have 2 holders; one card in each.

 

valusoft wrote:
Today's world has not been made for the elderly

Indeed not.

 

frown

 

These things based on the "credit card" format are particularly poor in that respect.

 

And then there's the reliance on smartphones & internet.

 

valusoft wrote:
Who's elderly?

I'm thinking, late 80s here.

But I was once mentoring a recent graduate who was working on a project targetting "the elderly (sic)" - he was talking about "really old people - over 50" surprise

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillator: https://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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ki0bk
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Posted by ki0bk: Thu. Apr 8, 2021 - 01:47 PM
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js wrote:
Who's elderly?

I still haven't learned to act my age.

 

I'm with Jim (east coast) if the two cards work in different RF bands, then yes it may work, however if both are in the same RF band, then no, they would interfere with each other even with a Faraday shield between them!

Flyover Jim

edit: Personally  I thing NFC payment cards are a dumb idea!!!!

 

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awneil
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Posted by awneil: Thu. Apr 8, 2021 - 01:51 PM (Reply to #9)
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ki0bk wrote:
js wrote:

Who's elderly?

I still haven't learned to act my age.

youth is fleeting - but immaturity can last forever ...

 

laughcheeky

Top Tips:

  1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
  2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
  3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
  4. Difference between a crystal, and a crystal oscillator: https://www.avrfreaks.net/comment...
  5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
  6. Beginner's "Getting Started" tips: https://www.avrfreaks.net/comment...
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ki0bk
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Posted by ki0bk: Thu. Apr 8, 2021 - 01:54 PM
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awneil wrote:
youth is fleeting - but immaturity can last forever ...

One can hope not, but I'm stealing that line, that's a good one!

Thanks Andy

 

Keys to wealth:

Invest for cash flow, not capital gains!

Wealth is attracted, not chased! 

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MurdoMcLeod
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Posted by MurdoMcLeod: Sat. Apr 10, 2021 - 09:37 AM
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Actually multiple cards at the same time can coexist.
The smartcard ie 13.56MHz ones can be individually enumerated as they have anti collision mechanisms in the protocols. There are actually two different types of 13.56MHz cards and both can be read and enumerated in parallel as they use different command sets.
The systems I design can read an ID smartcard buried in a wallet amongst NFC bank payment cards.
A 125KHz and any number of smartcards will work okay as they are different frequencies and the antennas are tuned for different frequencies. One card will slightly detune the others and the reader but not severely.
Two 125KHz cards won’t work together as they are (usually) dumb and just keep spitting out their id codes, therefore they conflict and it’s impossible to separate the bitstreams.

There are already a million monkeys in front of a million keyboards, and the internet is nothing like Shakespeare!

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