Antennas for ID-2
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.
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(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.
/JDHR
(iPhone picture of the samples I received)
Hey there dude,
I’m looking at incorporating a reader into a wrist band form factor.
Like you i was looking at the ID-2, but it needs an external antenna.
It is stated that you need an antenna with 1.08mH inductance.
Looking at the http://www.grupopremo.com website they list them but they are 2.28mH
Could you possible update a link the your 1.08mH version, or where they just one offs?
Cheers,
Scott
Hello Scott, I actually wrote to the Grupo Premo guys and, although the 1.08mH version of the antennas was not listed, they were very happy to custom make them for me. As it is shown in the picture I received three samples of each and they worked perfectly. I am currently in talks with them to buy a bunch more of each that I am needing for my project.
I guess the best you can do is to drop them an email. Another option would be to go for the CoilCraft antennas, if the form factor works for you of course.
Cheers!
Hi,
Thanks for getting back so quickly. I have send an email to the guys at Grupo Premo so i’ll see what they get back to me with.
Could you send me the link for the ones at CoilCraft? i couldn’t seem to get a picture or the dimensions.
On a side note, what was the read range like for the antenna that Grupo Premo sent you?
Cheers,
Scott
Hello Scott,
The CoilCraft link is: http://www.coilcraft.com/4308rv.cfm and the grupo premo antenna’s range is about 2, 3 centimeters at most.
/JDHR
That’s Brilliant,
Thanks for all your help!
hello, I’ve found your blog when looking for an antenna for my id-12 rfid reader.
I saw that you suggest two vendors and that the antenna I’ve to buy must have 1.08mH inductance for your ID-2, how about ID-12? Have I to buy an antenna with the same inductance?
Thanks, Davide
Hello David, the ID-12 has an antenna embedded and you cannot change it or add another one. If you want that you have to use the ID-2. I hope it helps!
Hi! Thank you for the very useful blog post! Can you let me know what range you found (to a standard 125kHz ISO card) with the Coilcraft antenna?
Hugo, the range was about 4cms max…. no more. However, about 20% of the cases it would go down to about 2cms.
Hey,
Did you try tuning the signal with a tuning capacitor?
Cheers,
Scott
Nop, the ID-2 has an internal tuning capacitor and that’s why I bought the 1.08mH antennas. Playing with the capacitor is when it becomes messy, specially if you don’t have the right equipment.
Hello,
Came here from SparkFun and also looking for an antenna.. but I don’t understand exactly the difference between double axis, single axis coil. Single axis is same as z-axis ?
Also, maybe I’m stupid, but I don’t see any spec that gives size dimension on coilcraft site,
but looking at your photo, seems small enough..
Anyway, many thanks for writing this blog entry!
Hello SFR75,
First, thanks for coming all the way here from Sparkfun. It’s for people like you that I created the post and linked to it from the Sparkfun website. Let me start with the single axis, double axis thing. An antenna has a coil, which is a metallic line wound up on itself. This coild generates an electromagnetic field perpendicular to the center of the winding. Now, when this things are produced for being mounted on a PCB, when you look at them from the top, the circumference of the coil is either facing you (se can see a ring) or you’re looking at the coil from the side. In the first case the electromagnetic field of the coil is vertical/perpendicular to the surface of the PCB. So if the PCB is built on the X and Y axis, then this king of antenna is a Z-axis antenna. The other antennas don’t have a particular name as far as I know.
Now, single axis or double axis. As you can imagine an antenna being a coil, the electromagnetic field will be created on both sides of the coil — and thus general antennas are called double-axis. For a z-axis antenna it means that the vertical field both goes up from the board and under the board. Following a special building procedure similar to putting a mirror on one of the sides, the electromagnetic field can be focused only on one of the sides — transforming the antenna on a single-axis antenna.
Finally, in relation to the dimensions for the coilcraft antennas. You can find them under the “specifications” heading, or you can go directly to this link (http://www.coilcraft.com/misc/4308rvd.html).
Regards,
Juan David