RFID Reader ID-2 (125 kHz)

Replacement:SEN-11862. We now carry the ID-3LA which accepts a lower voltage input. This page is for reference only.

This is a compact and easy to use RFID reader module from ID Innovations. The ID-2 is a smaller module requiring an external antenna. Hook up an antenna, power the module, hold up a card, and you'll get a serial string output containing the unique ID of the card.

  • 5V supply
  • 125kHz read frequency
  • EM4001 64-bit RFID tag compatible
  • 9600bps TTL and RS232 output
  • Magnetic stripe emulation output
  • 19x21mm

RFID Reader ID-2 (125 kHz) Product Help and Resources

SparkFun RFID Starter Kit Hookup Guide

May 5, 2015

Learn the basics of how to get started with the SparkFun RFID Starter Kit.


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Member #138787 / about 12 years ago / 3

    A few notes regarding what I discovered while playing with this part:

    My original hook up had my 0-scope and notebook (the ID2 was plugged into the notebook for power) powered from a wall plug. The results were lousy and inconsistent. Ran everything off battery (no grounds) and, after tuning the antenna, wound up with better than 6" of repeatable range. Figured I had a ground-loop which would go away with only one device connected to AC but it didn't work that way. With either the scope or the laptop connected to AC the range was shortened, sometimes to nothing. I need to re-test all that because maybe I did something stupid. It wouldn't be the first time.

    Building and tuning the antenna: First off, get some construction paper and glue and build a good coil form so you have closely spaced turns. Five or six inch diameter is a good start. I got down to 4" before I ran out of wire and they all worked about the same. You want a groove to lay the wire in that keeps it closely wound so, whatever gauge wire you're working with, figure about 70 turns and do the math to figure the width and depth of the groove. The turns don't have to be wound perfectly, just fill up the groove evenly and keep the wires tight but not too tight (like a woman's skirt, short enough to be interesting but long enough to cover the subject). I wound up an antenna according to the data sheet recommendations, plus a couple turns. Hooked up my scope and unwound a couple turns until I got the max peak to peak voltage across the antenna, something like 180v. Unhooked the scope and the distance dropped a couple inches. Scratched my head and then thought "AH HA, probe capacitance!" plugged in a small capacitor parallel to the antenna coil and got the range back. I just ordered an LCR meter and think if I can tune the antenna exactly I might get more range. BUT, at this frequency we're talking magnetic coupling, not RF, so any metal close by will likely de-tune everything and adversely effect range.

    As for why the short range in the video, my guess is in the video everything was done on a metal desk. On the other hand, I just ordered an ID-20 to play with so, we'll see.

    • anarnold87 / about 11 years ago / 1

      I noticed the exact same behavior while tuning the antenna. I have ~55 turns of 32 Ga magnet wire on a 120mm Diameter form made from laser-cut acrylic. I compensated for the probe capacitance with a 100pF ceramic capacitor in parallel with the antenna, and it reliably reads cards inside of 12-20cm from the antenna. I plan switch out for a better quality capacitor, and will report on any increase in range.

  • kevindtimm / about 14 years ago / 2

    Coil winding info (page 5 of the .pdf)

  • clever / about 12 years ago / 1

    i initially had trouble getting the antenna tuned at all, until i found this post

    it turns out, that when the coil and capacitor are tuned properly for each other, the ID-2 will generate over 100vac across the coil

    once i figured that out, it was just a matter of trying different combinations of tuning caps (in parallel) until i got 100vac across the coil, and it came to life!

    • Member #251389 / about 12 years ago / 1

      If you don't have access to a several hundred dollars worth of scope, measure the current consumption of the ID-2. When it is at maximum, the coil is tuned. I achieve 17-18 cm with a card. Hand-made coil, as it is described in the document.

      • clever / about 11 years ago / 1

        A true rms volt meter on account mode may also work to measure the resonance across the coil

    • clever / about 12 years ago / 1

      the coil from an FM radio also seems to work ok, even with the ferrite left in

      just needs 2 relatively large tuning caps and the variable cap on the radio to fine-tune it

      ive noticed that too much capacitance causes the peak-peak voltage to go back down on the scope

  • jhincapie / about 13 years ago * / 1

    Hello all, if you are in need of small antennas (less than) 10cm range at 1.08mH, please read my blog post on the topic (blog.jhincapie.com/2011/07/09/antennas-for-id-2/). There are basically two vendors out there that I know of, I have tried them both, and they work perfectly.

  • Member #216071 / about 13 years ago / 1

    a question relating to the demonstration video here
    Does it read 2 tags/cards one after another, if the tags/cards are not put together in stack?
    Also i found another limitation of using 2 or more readers in the same range from http://bildr.org/2011/02/rfid-arduino/
    It says "more than one reader right next to each other can cause none of them to work due to interference."
    Anyone has a solution for using 2 readers (next to each other) to read 2 cards?

  • Arandy / about 13 years ago / 1

    somnicro sells some 125KHz anntenna coils here:
    The company is the same who produces the SM130 module sold here. It produces the SM125 aswell and 13.56MHz PCB antennas too.
    I wonder if those 125KHz antenna is suitable for all ID-XX products.

  • Shruti / about 13 years ago / 1

    Hi could anyone tell me if the RFID Reader ID2 is detects RFID Buttons or not

  • aremu / about 14 years ago / 1

    Please the data sheet is not clear to me.Is it that I can connect to my PC serial port directly without max232?And which of the pins because I can see D1 and D0.What about tune capacitor?<br />

  • smartroad / about 14 years ago / 1

    I found a website that said about calculating the size/shape and inductance for an RFID antenna but can't find it now! Has anyone else found such a site?

    • Member #105131 / about 14 years ago / 1


  • Diaz / about 14 years ago / 1

    question!, is this RFID gives a TTL USART OUTPUT??, can you read this with a simple 16F877 PIC Microcontroller??
    i may buy this for industrial proyects

  • Mersennse31 / about 14 years ago / 1

    I was curious to know if and how the range of the RFID readers, esp ID-12 can be increased?

  • smartroad / about 14 years ago / 1

    is there anyway to increase the range of this? I need about 1-2 meters. My friend runs a small off road enduro race, I was looking at finding a way to time the riders cheaply. RFID seems an ideal solution but I need a greater range then these can provide. Been looking but not sure if it is safe to use an antenna bigger then the 15cm square the datasheet suggests.

    • MikeGrusin / about 14 years ago / 1

      Trust me, we'd love the same thing. The problem with increasing the range of the ID-2 is that since it's really a low-power radio transmitter, it's limited in the size of the antenna it can drive. To get longer ranges (and bigger antennas, such as something you could put beneath the finish line of a race), you need more power.
      I've seen open-source RFID reader designs out there on the net, which could theoretically be beefed-up to get longer range and drive larger antennas (assuming you know something about the black art of RF and antenna design). But since the ID products are (A) proprietary and (B) encased in epoxy, it's unlikely that they could be easily modified. (I've learned not to underestimate our customers though; if anyone can do it, let us know and we'll bask in your glory!)

  • alexsimps / about 14 years ago / 1

    Have one of these readers and am also looking for a compatible antenna?

    • MikeGrusin / about 14 years ago / 1

      The ID-2 requires an external antenna; the ID-12 and ID-20 have built-in antennas. We don't sell antennas for these, since they're just a coil of wire most people just wind their own. The datasheet has some information on doing so, and there are also examples on the internet.
      Unless you're interested in antenna theory or are trying to solve a specific problem, the ID-12 and ID-20 are much easier to use right out of the box.

  • Mister Chris / about 15 years ago / 1

    The datasheet list a read range of up to 25cm using an external antenna, but I haven't been able to locate one on Sparkfun. (I'm not entirely sure what I'm looking for to be honest, so I'm off to search a series of tubes:) Does Sparkfun sell an external antenna compatible with the ID-1?

    • Member #138787 / about 12 years ago / 1

      For those looking for an antenna, I haven't bought one of these but you could try: http://www.rfidshop.com/idi001-lf-antenna-for-id2-reader-19-p.asp

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