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RFID Reader — Parallax Forums

RFID Reader

OrionOrion Posts: 236
edited 2005-08-04 18:00 in General Discussion
Two quick questions on the Parallax RFID reader.

1. What happens if more than one tag is within range of the reader?

2. What does the reader do if a single tag is left within range, will it
····· a. only report the id once
····· b.·repeat the id every x secs

·

Comments

  • ManuelManuel Posts: 105
    edited 2005-08-02 21:24
    The RFID readers are capable of reading several objects at time. You will get the response of the tags every time you send a signal with the RFID Reader/writer.

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    Best Regards

    Manuel C. Reinhard
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-02 21:25
    Hello,

    ·· Two tags will not be read at the same time...The field that powers the tags may power more than one, but if two try to respond, the data won't be valid, in which case you get a bad read.· As for repeats, that depends on your code.· Once the device is re-enabled it will re-read the tag if it's still there.· Typically you will bring the Enable line high after a read momentarily.· When it's low again, the RFID will start reading again.


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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • OrionOrion Posts: 236
    edited 2005-08-02 21:32
    So if the enable pin is held low the reader will continue to report whatever tag is in front of it?

    I see the data sheet says multiple tags will cause collisions and confuse the reader. I was just curious what it would output, if anything.
  • OrionOrion Posts: 236
    edited 2005-08-02 21:33
    allright so the enable pin needs to be toggled to get a new read?
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-08-02 21:38
    You don't have to, but it helps stop the reader from trying to send other tag data while you're handling data from the previous read, and it also shows via the LED when a tag is ready to be read.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • OrionOrion Posts: 236
    edited 2005-08-02 21:41
    Roger that.

    Thank you!
  • ManuelManuel Posts: 105
    edited 2005-08-03 17:55
    I was thinking of getting a low cost RFID reader/writer, does someone know where i can get it? I thought the one parallax sells was writer. WHat i want to do is demonstarate at my school that security wont increase with a RFID system for access by using my school ID, reading it and then making an exact copy.

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    Best Regards

    Manuel C. Reinhard
  • TD-LinuxTD-Linux Posts: 33
    edited 2005-08-03 18:22
    The one Parallax sells is a reader, not a writer. The Parallax one can read the tags Parallax sells, but cannot write to them. Parallax's tags are preprogrammed with a unique ID, which should be enough for your purposes. You won't be able to make a duplicate - but you could 'pretend' and at least show that the tag could be read without you knowing easily. Writers are horribly expensive, $300+.
  • ManuelManuel Posts: 105
    edited 2005-08-04 17:08
    Thats sad to hear [noparse]:([/noparse]

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    Best Regards

    Manuel C. Reinhard
  • Paul BakerPaul Baker Posts: 6,351
    edited 2005-08-04 18:00
    If your goal is to provide a low cost RFID system, using a read/write sytem isn't the way to do it. Static (read only) RFID system is, I don't understand why you need to have the copy function. Writing ability on an RFID system is only nessesary when using the same RFID tag on different and physically remote systems which are incapable of communicating with each other and data associated with the RFID tag must be transfered between the systems in a coherent fashion, this does not appear to be the case with your desired application. All you need is a back-end database that stores associated data with each RFID such as Student ID number, time of last check in/out, location of last check in/out etc. Since the RFID readers are connected to computers connected by a network, coherence of the data asscociated with the RFID tag is maintained within the back-end database itself.

    Every day I use two different RFID tags, one for the Washington DC metro the second to badge in and out of the Patent Office. Both of the systems maintains a good amount of security (especially the Patent Office, the metro still permits the use of temporary paper cards, though there is talk of banning these to keep better tabs on all commuters and therefore potential terrorists) and both of the RFID tags are read only for cost control purposes, the computers connected to the readers maintain all the nessesary data assiciated with the RFID tags.

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    ·1+1=10
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