Adding external antenna to the RFID Reader

Joe Grand

Hey everyone-

I've been asked a few times by customers if it's possible to add an external antenna to the Parallax RFID Reader. The short answer is "yes, but it's unsupported and could damage or destroy your device." The on-board antenna is specifically designed with proper inductance and quality and is matched and tuned to the RFID receiving circuitry. So, if an external antenna is built incorrectly, the read range could be significantly reduced or harm the reader.

I found this blog post of someone that has successfully added an external antenna:

http://todbot.com/blog/2007/08/09/adding-a-remote-antenna-to-parallaxs-rfid-reader/

Neither I nor Parallax will be able to provide support, fixes, or any help related to this, but it's a good hack and I wanted to post it to the forums so people have the resource available in case they want it. And, if you are successful with any RFID hacks or modifications, please post them on the forums to share with others!

Joe

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
---

Joe Grand
Grand Idea Studio, Inc.
Designer of the Parallax Emic Text-to-Speech, RFID, and GPS modules

sam_sam_sam

Joe Grand

If you do not have a inductance meter then how do you know if the inductance is between 500-1000 uH

This in part of what it says......... at this link http://todbot.com/blog/2007/08/09/adding-a-remote-antenna-to-parallaxs-rfid-reader/

........To fashion an antenna, you need to create a >1/2″ diameter loop of about 100 turns of 30-gauge enameled solid-core wire (aka “magnet wire&#8221[noparse];)[/noparse]. Radio Shack sells a pack of magnet wire that fits the bill just fine...................

..........If you have an inductance meter, use it to make sure the inductance is between 500-1000 uH.............

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

Post Edited (sam_sam_sam) : 3/29/2008 4:13:27 AM GMT

Mike Green

There are formulas for calculating the inductance of a coil given the dimensions, the wire size, number of turns, etc. Actual physical coils can vary from the inductance specified by the formulas because the formulas are based on ideal coils, hence the need to measure the actual inductance.

sam_sam_sam

Mike Green

Thank You for your reply That help alot

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

parsko

Sam,

I have a mathcad worksheet to calculate the coil mechanics, plus other stuff. It includes the formulas in a straightforward manner and could easily be ported to excel, should you have the patience.

http://forums.parallax.com/attachment.php?attachmentid=48260

That should be my latest, but I would have to check when I get home, as that is where my files for this are. That should get you pointed in the right direction, though.

PLEASE post any results you may arrive at!

Also, my post for doing something similar...

http://forums.parallax.com/showthread.php?p=648973

Joe, thanks for the insight. I think I may have been one of those contacting you in the past... And, your answer was in-line with what could be expected. Do you think Chevy would support a warranty claim on a twin-turbo modified Corvette, probably not

-Parsko