I am complete electronics newbie, so please bear with me :)

I would like to connect an LCD directly to a 433 MHz RFID tag. So whenever I swipe the RFID tag near the RFID writer, the values that are written to the RFID tag would be displayed on the LCD.

Is this possible, if so, can someone please point me in the right direction?

EDIT: To clarify, the RFID tag needs to be on the same PCB as the display.

EDIT - 14/05/2012: Looks like there are a lot of questions on what I am trying to do, so here is what I am trying to achieve:

  • I want to create a pocket device (more or less the size of an iPhone) that is able to receive a numeric password from a server within the office
  • The device needs to have a battery life of 3-6 months at least
  • The range that the device should be able to get the password should be up to 50 meters
  • The numeric password on the device will be updated every 1-2 minutes

Since battery life is a constraint, and updates are only every 1-2 minutes, I thought medium range RFIDs would be the best option. Let me know if you can think of a better solution.

  • \$\begingroup\$ This entirely depends on the RFID reader and the LCD and you haven't provided any information about what you want to use. In general case, you'll need to have some sort of microcontroller that will read the data from the reader, process it and send it to the LCD. If you're lucky, you might be able to find a reader that can directly drive an LCD, but I doubt it. \$\endgroup\$ – AndrejaKo May 14 '12 at 0:54
  • \$\begingroup\$ For the LCD, something like this sparkfun.com/products/710 . Is it possible to avoid using an RFID reader, and connect the microcontroller directly to the RFID? \$\endgroup\$ – rob May 14 '12 at 2:13
  • \$\begingroup\$ Directly to RFID what? You'll definitely want some sort of reader. There are microcontrollers with integrated RFID readers, like for example ATA5505, but it's only available in QFN38, so unless you have a PCB, you'll need to find an adapter too. I think sparkfun may have some, but I'm not sure. You'll also need to check if the operating frequency matches the one your cards use. \$\endgroup\$ – AndrejaKo May 14 '12 at 2:24
  • 1
    \$\begingroup\$ Why would you want the tag to be on the PCB? It suggests you just want a fixed ID. Can you explain what problem you are trying to solve as it sounds like we are trying to answer an odd question. I have built LF RFID readers from just Atmel processors, but you need an RF front end for HF. 433MHz however is not what I would call RFID - these are active tags ie. just small transceivers, unlike LF and HF tags that are passive. \$\endgroup\$ – Cybergibbons May 14 '12 at 6:46
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    \$\begingroup\$ @avra - There are writable RFIDs too! \$\endgroup\$ – stevenvh May 14 '12 at 9:37

"Is it possible to avoid using an RFID reader, and connect the microcontroller directly to the RFID?"

Using the RFID tag directly with a microcontroller without an RFID reader is useless, and often impossible.
Commercial RFID tags usually have only 1 connection to the outer world, and that's wireless. They draw their power supply from an RF carrier and send their data over that same carrier by loading it, so that the reader will see dips in the signal.
If you want to skip the RF, and directly connect, you may as well use a serial EEPROM which you read an ID from.

"the RFID tag needs to be on the same PCB as the display."

An RFID reader is the RF interface, which will pass the code received from the tag as an electrical signal to the microcontroller. So the microcontroller with its display is connected to the reader side, not the tag's.

For a reader this only makes sense. The display will change for each different tag the reader detects. If you connect the display to the tag it will always show the same code. That's unless you want to write to the tag to change its code.

The solution then would be to make your own tag. You'll need a microcontroller with a coil antenna connected that picks up the carrier, and which you will modulate. The other side of the microcontroller will drive the display. This will need much more power than can be drawn from the carrier, so you'll need at least a battery power supply. In which case an LCD is preferred over a LED display, because it uses less power.

Beth made her own RFID tag with just a small microcontroller and a coil. You'll need a bigger microcontroller with enough I/O to control the display.

Which microcontroller?
An LCD module with integrated driver is easiest to use, though the one you chose is way overkill for just displaying numbers (unless you want to add fancy graphics too). It's a graphical display which AFAICS doesn't have a character generator, so you'll have to draw your digits on it yourself.
Anyway, whether you use a character display or a graphical one, the interface will be more or less the same: 8 (or 4) data lines and a few control lines. Any microcontroller with minimum 16 I/Os will do. Remember you'll also need at least one, maybe two I/O pins for talking to the RFID reader/writer.
Like most of these modules this one needs a 5V power supply. So choose a 5V microcontroller. If your favorite controller only works at 3.3V you can use level shifters to interface the two, but it's better to avoid them if not really needed.
You'll want a microcontroller with some EEPROM to store the code. Again, if yours doesn't have that you can use an external one, but you should be able to find a controller with the EEPROM on-chip.
In the Atmel ATMega series the ATMega8 is a controller that fits the bill.

See also this question.

| improve this answer | |
  • \$\begingroup\$ Exactly, the RFID tag will be written to, so the code will change. I want to be able to display that code on the LCD. Any suggestions for the microcontroller? \$\endgroup\$ – rob May 14 '12 at 6:29
  • \$\begingroup\$ @rob - What does the data you want to display look like? Numeric, hexadecimal, text, 8 chars, 20 chars? This will have its impact on the controller choice. Tell me more and I'll add a section to my answer. \$\endgroup\$ – stevenvh May 14 '12 at 7:02
  • \$\begingroup\$ Numeric (eg: 1,123 ), and I want to display the numbers onto an LCD like this one - sparkfun.com/products/710 . \$\endgroup\$ – rob May 14 '12 at 7:07

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