RFID card from radioshack?

Discussion in 'Wireless & RF Design' started by Mathematics!, Mar 23, 2010.

  1. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
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    I have noticed that the RFID cards that radioshack was selling from $50 are now about $20. Same ones

    I am thinking about getting one to fool around with.
    However I have read the back of the package and it say's it works thru the serial port of a computer. I have seen in the package their is a 4 pins VCC , GND , S/OUT and one other I am curious about how I wire this up to the serial port on a computer (9 pin DSub serial port)....

    I don't think these RFID cards are programmable other then being able to send it commands /recieve barcode data.
    The package contains two RFID tags to use for things which is cool an extra one is always a good thing to have.

    I believe it is from www.parallex.com or something I don't remember but I think it said for more info go their....

    If anybody has worked with these RFID radioshack cards please let me know how to hook it up and use it with my computer. Because then I am willing to buy it.

    Thanks
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    If this is the module you are talking about :
    [​IMG]

    Then, I have played with it a bit, it connects directly to a microcontroller, but you will need a level translator to use it for a PC (such as a MAX232CPE RS232 to TTL Transceiver), the RFID module only has a transmit connection (SOUT), you do not, and can not send anything to the module, it is all pre configured for 2400 BAUD at 8,N,1...

    The one pin besides the power and SOUT pin is an ENABLE pin, you can pull this low to enable the module, and pull it high to disable it (for power saving mode)...

    Once the module "detects" and "interrogates" a tag, it will send a 10 digit character ending it with the carriage return symbol (&H13)...

    I have not connected it directly to a PC, but I have used it with the Pic32MX microcontroller from Microchip...

    B. Morse
     
  3. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Sorry for bring back an old post.
    But I am still think about getting one. Yes these are the things I am talk about.
    However from the above info
    correct me if I am wrong.

    When the tag is within a certain distance of the rfid reader it will send
    a 10 digit character ending it with the carriage return symbol (&H13)...

    But if the card stay's in this range will the 10 digit characters keep begin sent until the tags go out of range?

    Is their away to test how far away a card is or direction relative to the rfid reader it is?

    Also so is it like the rfid tags are transmitters that transmit only the 10 char
    And the rfid reader is just a receiver to receive these 10 chars.... Or do they both transmit/recieve data...etc ?

    In your picture where did you get the connector does it come with the RFID reader/tags because I didn't really see it in any of the radioshack packages?
    Also where is your wire with the connector going to?

    Is these RFID readers/tags suppose to be used with a MCU normally and not go thru a computer? Because I read on the back that it is sending the 10 char code serially so it seems as though it will just send the chars one after another out the SOUT pin. If this is true then all I have to do is get a serial 9 pin sub-D connector and solder so wires to it looking at the pinout....etc etc
    To integrate this into my computer... then all I have to do is set the COM port baud rate to 2400.

    I should at least beable to display the results using hyperterminal or something.

    I don't really see the need for this if I use my serial port to connect it to the PC. Weather I go from rfid to computer or rfid to MCU to computer. I can still have everything being sent serially so no converter chip would be needed.

    I could see if we where converting from parallel to serial but we are doing everything from serial to start/finish.


    ALSO what is the big deal with these things all they really do is just tell you when a given tag is in range of a rfid reader by transmiting a 10 char code. Can they do anything else then simple tracking when something is close to the reader?
    Because it seems somewhat borning if this is all it can do.

    Also wondering what range I can expect with these tags?
     
    Last edited: Jun 17, 2010
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    for one, sending serial data from the RFID unit or a microcontroller is at TTL level (5 volts), PC's use RS232 Levels (10 to 15 volts), if you connect the RFID module or microcontroller directly to your PC's serial port, you will most likely damage the micro or the RFID module....

    If you want to use the RFID/Microcontroller directly with a computer you WILL need a level translator IC such as the MAX232CPE...


    The RFID module works by sending out a RF frequency that is picked up by the tags, the tags then convert this RF energy to power itself and to send the data back to the interrogator, the interrogator module then receives and decodes this data, which is then sent out the SOUT pin....

    The Reader will only read the tags once (The tags have to be within 2" to 3" to the reader) even if you hold it in place, you have to move it away from the RFID reader then place it close again for it to read it again....


    And yes that is all this module does, thats it.

    B. Morse
     
  5. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ah, I didn't realize the computers serial port uses 10 to 15volts thought it used only the 5volts source equivalent to what usb's VCC is. Now I see why.
    Instead of getting this MAX232CPE could I just use some resistors to drop the voltage to 5volts for VCC.....seems like I still could do it with out any complicated circuitary? Or is the level translator IC doing more then just droping the voltage to 5volts DC... because if that is all it does this could be accomplished by resistors.

    I am assuming you mean 2 feet to 3 feet not 2inches to 3 inches.

    Either way this is really restrictive in distance.
    I cann't see these being very useful for anything?
    Correct me if I am wrong but the must use higher powered RFID tags/readers when tracking shipments of purchases ...etc unless each box is scanned whenever the truck stops at then next stop on the way to your destination???

    Only one last thing with these RFID cards/readers where did you get that connector in the picture and where is the connector wire running to (what type of MCU or other circuitary do you have connected to this RFID reader.)
    (what are you using yours for) <-- I noticed in your earlier posts you said you used it with not a computer but with "Pic32MX microcontroller from Microchip". Ok, but what is the MCU doing with the 10char code when it recieves it, do you have a small LCD screen or something to display a message like rfid card detected or flash a led or something....
    What is your purpose for it, application or just experimentation/playing around.

    Thanks for your help
    I have atmega32 avr chips maybe I will do something similar to get familiar with the rfid technology .
     
    Last edited: Jun 18, 2010
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    The level translator IC will convert the 5 volt TTL from the RFID to a usable level for the RS232 Serial port.... if it was the other way around, yes a couple of resistors will do the trick, but unfortunately you can not use resistors to convert 5 volts to 10 to 15 volts level......


    And yes, I did mean 2 inches to 3 inches.... getting an RFID tag reader that can read from several feet of distance would be really expensive...... the one from Ratshack (or parallax) is geared towards the low cost hobbyist so distance is not very good.

    I used it for automating my kids bathroom, each user has their own tag to activate the functions in the bathroom, such as the shower, etc. It was a project I submitted to the MyPic32 Design Challenge sponsored by Microchip that ended last year, check out the project here >>> http://www.morse-code.com/id155.htm

    The connector I used is just a 4 pin connector similar to what you see on CD-Rom Drive audio cables... I do not have the part number on hand but it is an AMP connector....


    Since the RFID tag reader does only send, you may get away with directly connecting he SOUT pin to the Receive pin (Pin #3 of serial port DB9 socket) of the serial port, some newer serial ports will tolerate the 5 volt TTL level.

    You can also use a transistor to switch the RFID enable pin using the DTR line of the serial port.

    B. Morse
     
    Last edited: Jun 18, 2010
  7. Mathematics!

    Thread Starter Senior Member

    Jul 21, 2008
    1,022
    4
    Ya, I thought about it for a second 5vdc to 10/15vdc is the part where the resistors cann't help.

    My only other question is how do the busniess track products.
    Or another words I have bought stuff online and watch where my product is relative to it's final destination.

    If they are using RFID cards/tags/readers.... they must beable to make the readers/cards to transmit alot longer then 2" to 3".

    I am wondering do they physically stop and scan each box with a reader as they get to the next state etc...
    Or do they just put the truck next to a reader that reads all the cards in one shot.

    How much would one of these equivalent rfid readers/cards cost?
     
  8. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Usually for tracking purposes they would use a type of barcode (Usually an Aztec or Matrix type, and postal barcode for anything that goes via US Mail), and yes, each package is scanned in when received, and then scanned again when put into another vehicle....

    Check this out if you have around $3K you can get one that can read up to 10 meters... :) >> http://store.rfideas.com/shared/Sto...2=332633614&CategoryID=31&Target=products.asp


    Do a search on Google for "Long Range RFID Tag Readers"....

    B. Morse
     
  9. skeptic

    Active Member

    Mar 7, 2010
    51
    9
    Your project is quite impressive. Congratulations.

    The railroads have replaced the old multicolored bar scanners with RFID tags which are activated from several meters away with much higher power RF.

    The cars are pushed one by one up a small hill or hump and as they coast down the other side their tags are read and the information from the tag causes the car to be switched to the proper track and train.
     
  10. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Thank you Skeptic.....

    B. Morse
     
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