What powers contactless cards?

Discussion in 'Wireless & RF Design' started by chris155au, Aug 22, 2018.

  1. chris155au

    Thread Starter New Member

    Aug 22, 2018
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    I tried to search this, but couldn't find anything. What powers the RF in contactless cards?
     
  2. BR-549

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    Sep 22, 2013
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    The field from the point of sale antenna.
     
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  3. chris155au

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    Aug 22, 2018
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    Oh. Incredible! I just assumed that there would have to be a signal sent from the card. So what is the device in the card?
     
  4. BR-549

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    Sep 22, 2013
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    The rf circuitry in the card....absorbs the POS antenna field.........rectifies it......charges a cap.....then sends signal back to POS antenna with information.

    Read and study RFID.
     
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  5. chris155au

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    Aug 22, 2018
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    "cap" as in?
     
  6. BR-549

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    A capacitor. It then uses this charge to power the card.
     
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  7. chris155au

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    Aug 22, 2018
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    Do you know if the capacitor can retain residual charge? Or does it all dissipate from the signal send?
     
  8. BR-549

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    That would depend on many, many things. From orientation....to hardware and software.

    If it did.....it probably wouldn't last long.

    There is new tech coming for powering all this kind of stuff. It's because of the low current/power requirements for the new chip circuitry. In almost any environment now(even in a pocket)....energy will be harvested for wireless connectivity.

    Edit: and at distances much farther than now.
     
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  9. chris155au

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    Aug 22, 2018
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    Today, I made my first ever contactless payment with my first contactless card! I held the card about an inch away from the terminal and the shop clerk told me that it is better if I touch the terminal with the card. (so much for CONTACTLESS) And knowing that certain pieces of human garbage around the world spend their sad and meaningless existence going around with a receiver, collecting people's card data, and given that this can be done from quite a distance, it surprised me that I had to get closer to the terminal than an inch away. Although I'm sure that you would say that they are using significantly higher powered receivers than a point of sale terminal. Although, given that most people will keep their cards in a wallet or purse, it does seem quite impossible.
     
  10. BR-549

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    Oh....it was security that you were thinking about. That is a whole different science and subject.

    There are modulation techniques that can make monitoring a transaction almost impossible.

    And of course there is encryption.

    With the size, function, memory, and power.....and being able to stamp this stuff out cheaply....It is being used for a lot of product tracking now. It just doesn't track...it can log the environment.(even acceleration) A complete time line history since manufacture. 100% quality control.

    And with "block-chain" security is assured....we think. A secure and complete history of the shirt and underwear that you are wearing.
     
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  11. chris155au

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    Aug 22, 2018
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    Sorry, what is the "it" in all of that?
     
  12. BR-549

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    RFID

    EDIT: RFID plus energy harvest will give us un-powered(sorta passive) wireless connectivity.

    The new tech will deliver secure and continuous connectivity for almost anything....or perhaps all things.

    Finally.....copyright/patent enforcement.
     
    Last edited: Aug 22, 2018
  13. chris155au

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    Aug 22, 2018
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    Sure, but are you saying that the card data captures are useless?
     
  14. BR-549

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    No. It depends on many, many things. Right now...most in use tech was not designed with security as a high priority. That is changing. It will take a while. When touch tone networks first started.....they had hackers and security problems. It takes time and a changing of design priorities.

    But everything is ripe for a revolution. Mass cheap production....low power requirements.....high function.....with security a priority. Cheap reliable tracking of all products. Not just a marketeers dream......but a bureaucrat's dream as well.
     
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