Shop OBEX P1 Docs P2 Docs Learn Events
RFID Technical Problem — Parallax Forums

RFID Technical Problem

AlisonAlison Posts: 6
edited 2007-05-01 17:06 in General Discussion
I am working on a school project (due on Thursday!!) with the Parallax RFID reader. I had everything up and running several weeks ago, but I am afraid that my reader is now somehow broken. It is not working at all, and the green LED does not come on even though I was able to determine using a multimeter·that there are 5V across it. If anyone has any suggestions, they would be greatly appreciated!
Thanks,
Alison

Comments

  • JonnyMacJonnyMac Posts: 9,214
    edited 2007-04-29 19:33
    Always start with the basics: double-check all connections (remember, that reader has an enable input) and connect to a simple test circuit that eliminates other possible problems.
  • AlisonAlison Posts: 6
    edited 2007-04-30 15:07
    Hi, thanks for the reply. I set up a very basic circuit according to a picture that I took when the device was working, and the light will still not come on, nor will the reader work.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-04-30 15:19
    Hello,

    What is the source of power for your project? What is the RFID Reader connected to for power?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • AlisonAlison Posts: 6
    edited 2007-05-01 15:37
    I'm using a breadboard to interface it with a microcontroller, which is attached by USB and is powered by my computer. I can tell that the microcontroller has power because of an LED.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-05-01 15:47
    Interesting…It seems as though you’re indicating that the RFID is ultimately powered from the USB Port but there typically wouldn’t be enough current to power that and the microcontroller. Which microcontroller are you using? As a note, an LED being on does not indicate that the microcontroller has enough power to operate properly. Just that the LED does, which can operate from a much lower voltage range. Take care.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • AlisonAlison Posts: 6
    edited 2007-05-01 15:54
    Ah, ok. I'm using an Arduino microcontroller, and everything worked fine for a while. Using a multimeter, I checked the voltage across the RFID reader, and it was 5 V, which is why I think that there is power going to the reader. If I'm wrong on any of this, just let me know; I'm pretty new to all of this. Thanks for all your help!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-05-01 16:26
    Are you checking the voltage right at the terminals on the RFID Reader?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • AlisonAlison Posts: 6
    edited 2007-05-01 16:32
    Yes, from Vcc to ground.
  • Mike GreenMike Green Posts: 23,101
    edited 2007-05-01 16:33
    The RFID reader draws as much as 90ma when it is active (reading a tag). I don't know what the Arduino draws, but it's probably at least half that. USB devices can't draw more than 100ma unless they're specifically designed for up to 500ma and the USB interface may be turning off the power to the RFID reader when it is activated. Depending on how the Arduino is set up in relation to the USB interface, it may be getting turned off as well.

    You really need a separate source of regulated 5V when you have USB devices that can draw more than 100ma.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-05-01 16:33
    Well if you’re checking there and there is 5V and no LED on the RFID Reader then it sounds like something definitely happened to the Reader at some point.· There should be an LED on.· Of course there is no way for us to know.· Perhaps a short in your circuit at some point?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
  • AlisonAlison Posts: 6
    edited 2007-05-01 17:06
    Hi Chris,

    I'm all set with everything. Just wanted to thank you for your help, I really appreciate it!

    -Alison
Sign In or Register to comment.