NOTE: This information also applies to the ID-3LA reader. Sparkfun sells a lot of amazing electronic parts very appropriate for prototyping, I use it a lot! One of the things I have been using lately is the ID innovations series of RFID readers (ID-12 and ID-2). They are super easy to use and to integrate with the Arduino platform.
Nonetheless, one of the problems I run into, and from my Internet searches I could see many people did too, was the antenna. While the ID-12 comes with an internal antenna, the ID-2 doesn’t. Having an internal antenna is perfect for prototypical because you just need to wire the reader to the Arduino and off you go. You are reading RFID tags in minutes. However if you start playing with the physical design of your device then you would like to move the antenna to a different place than the reader is, and then the ID-12 is not the piece you need anymore. You could, of course, buy your own reader IC, design a PCB for it and place the antennas and the respective resonance capacitors wherever you want, but… ain’t that quite some work for simply prototyping? I don’t even have an easy access to a PCB printer.
(I came across all this while working on a beefed-up 4×4 super version of the Rabbit)
Then I bought the ID-2 (which despite not having an internal antenna it does have a resonance capacitor) and set to find a matching antenna for it. Man, that’s hard! The point is that you either have to wind it yourself (which off course kills the passion of quick prototyping) or buy it from the market. There are thousand antenna providers out there, but it happens that no-one sells then small <2cm and with the needed 1.08mH inductance.
Well, almost no one, and this is the good news. I was looking into the catalogues of antenna providers until I found CoilCraft, these guys had one that almost matched what I needed (1.08mH capacitance but double axis, I needed it single axis), the 4308RV series at 1.08mH. I bought some of those antennas and they work as magic. However, I realized the antenna shape would make it difficult to build a really slim reader, so I started looking again for a Z-axis antenna. I wrote CoilCraft about it, but they didn’t saw any value in custom making those for me (I said I would buy 50 :|).
Until I found the Spanish Grupo Premo (http://www.grupopremo.com/). These guys had some Z-axis antennas but not at the require inductance for the ID-2. I went ahead and asked them to custom make the one I needed, and send me samples for free (quite a move) and to my surprise the guys said YES, and I have now received samples from two of their antennas (3 samples of each model) and they work as a dream.
(ZC1003 – SMD Z AXIS COIL LOW PROFILE)
(ZAC1203 – SMD Z AXIS AIR COIL LOW PROFILE)
So, if you are prototyping with the ID-2 and need a small and reliable Z-index antenna go to the Premo group. And don’t ask them for samples, they will be happy to sell you any amount starting from 1.