RFID Reader ID-20 (125 kHz)

Replacement:SEN-11828. This part has a new rev that accepts a lower voltage input, go check it out! This page is for reference only.

This is a very simple to use RFID reader module from ID Innovations. With a built in antenna, the only holdup is the 2mm pin spacing (breakout board available below). Power the module, hold up a card, and 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
  • Read range of 200mm
  • 38x40x7mm

RFID Reader ID-20 (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.

  • pcmofo / about 14 years ago / 2

    This is a great piece of code and hookup diagram for the ID-20 and ID-12. The reader is great, one known issue is that the serial line (D0, pin 9) needs to be disconnected from Arduino RX in order to upload a new sketch to the board or else the upload will fail.
    Reader has a range of about 8cm using the ID cards sparkfun sells. The thicker plastic key fobs are reading at about 6cm. With a case on this it should still have a great read range.
    If you tie the Reset line to 5v+ as the datasheet says you will have to wait a maybe a second after moving the card out of range to read the same card again. If you connect the Reset line to a digital pin on an arduino you can bring the pin HIGH, read the card, then bring it LOW after a successful read. Looping this will let you continually scan cards in range and/or scan cards faster.
    Make sure to use a transistor or a resistor on the LED/BZ output so you dont kill the pin.

  • mattstroud / about 15 years ago / 2

    Are EM4102 cards compatible with EM4001? Will this reader read an EM4102 tag?

  • Member #600619 / about 9 years ago / 1

    Please I need a reader which has external antenna port

  • Dutch_db / about 11 years ago * / 1

    I just bought three more and they say ID-20LA. What is the LA?

    • Kamiquasi / about 11 years ago / 1

      Looks like they've got your answer, from the ID-20LA product page:

      The new ID-20LA is essentially the same as the older ID-20, but has a lower input voltage.

  • Dutch_db / about 11 years ago / 1

    My ID-20 is reporting {FF} over and over continuously, with, or without a tag being nearby. It also does not acknowledge any tag, it just streams {FF} at me. I think it's swearing at me. Did I do something wrong?

    • Dutch_db / about 11 years ago / 1

      Never mind. Ground for RS232 was lifted just enough that I couldn't see it. This was the source of my grief.

  • TimZaman / about 11 years ago / 1

    read range 200mm? The guy in your own tutorial says, and I quote, "3 inches, definately not 7 inches". That was in perfect ideal conditions. Weird specsheet.

  • Member #419505 / about 11 years ago / 1

    Is ID-20 compatible with TI's MSP430 G2553?

  • Member #414518 / about 11 years ago / 1

    Hello! I want to implement a solution for access control car to my building using RFID. It's possible to do with Arduino? What would I need more? Reader, writer, antenna, adhesive tags? Here circulating approx. 1000 vehicles per day. Thanks!

  • liger / about 11 years ago / 1

    I am having read issues with the ID-20's serial starting with LV160912----

    If it's on Arduino with breakout; I can't upload the code, I need to take the ID-20 out, upload the code then put it on.

    If it's on Sparkfun RFID USB Reader; some readings stuck in loop and it tries to read after and after which brings out weird buzz and led light. Especially if you need to leave the rfid card on the reader for a bit.

    I have four ID-20's bought last year which they have serial number as only numbers they work really fine with both breakout and rfid usb reader.

    Does any have this kind of issue? I am getting so untrusty with ID-20's :/ or is there a production line issue with this last batch?

    • Viva / about 11 years ago / 1

      I have the same problem. Really hard to get consistent reads. The buzzer emits a very quiet tone if I leave a card on the reader (for a couple of seconds), followed by a normal "successful read" beep. The serial data is output twice

      • liger / about 11 years ago / 1

        Hey there,

        I have contacted to ID-Innovations about this issue and they took it serious. I sent a demonstration video about the problem and they sent me back this link saying it's sorted out.


  • magee / about 12 years ago / 1

    i'm having a hard time finding typical detect times. I am looking for a reader that can detect a tag that will pass by quickly. The detection window( when the tag will be within 2") will be 500ms or less. I can get the tag within a cm of the reader... Anyone with one of these willing to experiment or already have the anwser? Also, as an added challenge, i may end up having to attach the tag to the outside of a thin sheet of aluminum, about the same thickness as a pop can. How badly is that going to ding my detection range/ read time?

    • Tuc250 / about 12 years ago / 1

      Detection window - Not sure what the best way to test this would be, but in a totally unscientific test it can pick up a tag that is moving quite fast when it is within 1". Anything over 1" as long as it is moving at a steady rate it can typically pick up, but keep in mind you aren't likely to get more than 4" out of this reader. If you are using a conveyor belt of some sort I would imagine the reader would be capable of picking it up, but the aluminum will be a serious issue based on my results.

      Aluminum - I tested using both a card and fob. Attaching it to either the inside or the outside of an aluminum can (soda can) renders the RFID totally unusable at any range. However, I found that if I inserted a piece of printer paper that had been folded in half four times between the card and the can it functioned. So if you have some way of creating a standoff from the aluminum it might work.

      • magee / about 11 years ago / 1

        Thanks for your reply, we had similar results and are back to the drawing board. One idea is a rigged metal detector, seeking to detect a peak from a small ferris washer attached to the sheet of aluminum...

  • hello is there any password protected RFID tags out there? I need to protect my ID tages from copying.... thank you

  • Member #91488 / about 12 years ago / 1

    I have two ID-12s. I have written extensive code to use the ID-12 for a door lock application. I have no problems there. However, when trying to modify my code to operate two separate doors with two separate ID-12s (one for each door), the code will not work. The idea is to only open the associated door, so I have to make the code tell me which ID-12 is reading the card. I have them as NewSoftSerials, but I am guessing my problem lies in that I am using two serials and I did not code it properly. They won't even return that they are available(). Can anyone direct me to example where more than one ID-12 is used within the same sketch?

  • recyclism / about 12 years ago / 1

    This seams great. Small question where can I buy RFID cards? I want to use this for a door lock system so I need maybe 100 cards with unique ID?

  • cacondell / about 12 years ago / 1

    I have recently purchased an ID-20 RFID reader with the Sparkfun tags and I am using it with an ATmega128 AVR. I am using interrupts on the USART line to detect when a tag is being inputted, but the interrupts are being triggered far too many times, even after the tag string has finished. Does anyone know why this could be happening?

  • Any chance certain cellphones might interfere with RF-ID readers? I have a continual serial read on an RF-ID reader hooked up to arduino ... I've had two cases where I was testing read values, and everything was working fine ... then someone stopped by in the vicinity, the the reading stopped (paused?) ... reading seemed to continue after they left the vicinity. Coincidence? or known problem? With mobile devices having all kinds of sensors, and the radios inside, I didn't want to rule out of the possibility. The strange thing is that I touched nothing ... the reader was working fine, then the person(s) showed up ... it stopped, they left, and it continued reading ... I work in my cube with a WP7 device on T-mobile, and I haven't had an issue ... Maybe these folks have a global Blackberry that emits a bunch of bad things? Not sure where 125kHz and cellphones fit in the spectrum ... guess I'll look that up to see if things make sense.

    • MikeGrusin / about 12 years ago * / 1

      Interesting. 125KHz is nowhere near the radio frequencies cell phones use. However, I'm sure you're used to the phenomenon of noise coming out of amplified computer speakers when someone with a cell phone is nearby, and that phone is syncronizing with the cell towers. Cell phones do put out enough energy to mess with sensitive circuits, and the ID-20 may indeed be vulnerable to this. Unfortunately, the normal solution is to put sensitive circuits in a metal enclosure, which won't work with the ID-20 as it has its own antenna that needs to be exposed. I don't have much advice, except that you might ensure that your power supply is sufficient, clean, and decoupled with a capacitor (0.1uF is good, 0.1uF and 10uF together is better) as close to the ID-20 as practical.

  • Domonetic / about 13 years ago / 1

    Hi, I have a question. What ID-20 pin must connect to the port RS232 of arduino directly?

    • MikeGrusin / about 13 years ago * / 1

      If you're asking how to connect the ID-20 to an Arduino, the ID-20's TTL-level serial output is on pin 9. Connect this to the Arduino's RX pin, then set up the serial port for 9600 baud. (Note that other ID-20 pins need to be connected to 5V or ground to make it all work; see the pin descriptions table, "ASCII" column, in the ID-20 datasheet for details.)

  • Member #57306 / about 13 years ago / 1

    PCB design, complete code and details of an electromechanical strikeplate for using one of these to control access to a home avialable at...
    Does it work? I hope so... it is actually in use on my home. I get in just fine, and haven't had a burglar get in yet.

  • kleetus / about 13 years ago / 1

    Beware of using this product with the 2mm standoffs that Sparkfun sells. I wanted to get the standoffs for this unit to be able to easily remove the module from the PCB, but I noticed that the pins do not fit snugly in the socket. As a result, the ID-20 slipped out of its mounts and then came back down into THE WRONG socket whilst handling! Doh! This smoked one of my ID-20's. It made a huge bubble on the top of the Id-20 that resembled a pimple. That one is dead, the day before a similar thing happened and quietly bricked that unit. I think I am going to forego the standoffs and solder these units directly to the board. So now, I am wondered if the company would make a SMD version. I am pissed that I did not take better care of those 2 ID-20 that I ruined. Lesson learned.

  • kleetus / about 13 years ago / 1

    I bought 5 of these. I have them installed in a custom RFID card reader system. ID-20 -> PIC2455 -> Xbee Pro 60mW to a linux box running a custom daemon to reply back with an answer. The PIC then drops a relay to open a door. All was going great until last night we one of the readers just quit working. I am not sure why. It is the ID-20 module itself. It will not spit out anything. I am not sure how to troubleshoot the individual module since it is self-contained. I guess I just wasted $34.95. I hope the others do not just go bad. I am assuming that I misaligned the pins when plugging the unit back into the 2mm headers and I fried it. Anyone confirm my findings?

  • Member #151952 / about 13 years ago / 1

    i think it is time to have in stock the RW RFID with the RW tags please.
    We need them like hell!!!

  • Gregory Gomes / about 13 years ago / 1

    Hello, I'm working with a ID-20 reader and the tags that you use in the "example video". No problems when I try to read one tag at a time. How you show in the same video, I can't read more than one tag in the same time. So, may have Sparkfun some solution to read more than one tag at the same time? Some tags or readers witch works with some anti collision protocol. I hope so, but if don't may you could help me to find some other place that I may can buy these solutions?

  • Sullivbw / about 13 years ago / 1

    anyone know if this can read through a door?

    • Probably not. See RobertC.'s comments above about it reading through a project case, which is much thinner than the standard door.

  • Member #151952 / about 13 years ago / 1

    why dont you have any ID-12RWs?

  • Cloud / about 13 years ago / 1

    I have ID-20 I want to hookup this with PIC-18F4455. Have anybody tried something related with it ? I tried using RS232 communication protocol and used the getc() but not being able to get the right 12 bit data out of it.
    Thanks in advance..

  • Jon15 / about 13 years ago / 1

    I work as a RFID technician at Avery Dennison.
    We make these cards for Walmart and Dole for asset tracking, but at FCC 902 - 258 MHz.
    Really doesn't seem to be hobbyist readers for HF tags yet, but I'd really like one.
    Anyways has anyone verified the power output of this (dBm)?
    Thinking of grabbing one of these little guys and boosting it.

  • Member #205058 / about 13 years ago / 1

    i bought IR-20 with passive tag,when the reader get the information from the tag, i need to send the information to the the pic (dsPIC33FJ64GP802) by using SPI (Serial Peripheral Interface).
    i really have no clue how to do that, email me at Khaled_alshaiji@yahoo.com, or answer me here, its my part of my project, please i need your help?

  • Member #57306 / about 13 years ago * / 1

    A guide, with code, to connecting this to an Arduino is available at...

  • mehlion / about 13 years ago / 1

    Just curious, anyone use the sparkfun Project Case to house this reader? and if so how is the performance?

    • I used it in my project:
      It's a similar enclosure. It worked ok, but you needed to almost touch the tag to the case to get it to read. But it did work reliably.

  • cpmera / about 13 years ago / 1

    what type of ascii is the id20 reader reader using????

  • MER / about 13 years ago / 1

    I'm having a tough time reading this chip from an Arduino Duemilanove. I have it connected as the datasheet says (confirmed at this page) wired to the Rx pin (pin 0) of the Arduino. Yet when I run the simple relay code
    if(Serial.available() > 0) {
    val = Serial.read();
    Serial.print(val, BYTE);
    I get bupkis in the Serial Monitor, or I get a constant stream of a single character (I think it was 'ƥ' at 9600bps). The relay blinks when the card is held close by.
    Does it sound like I somehow burned out the chip? Is there any good way to test?
    Thank you,

    • Young Maker / about 13 years ago / 1

      Solution: you are reading the schematic for an ID- 12! no an ID- 20, i dk if there different

  • dab / about 13 years ago / 1

    I have used this component previously and really like it a lot. In my current project, I'm trying to move to a lithium polymer battery, and would like to run at 3.3V. However, the reader requires 5V. Do I need to have a voltage amplifier in order to power this device from 3.3V? Or is there a simple strategy to do this?
    I guess alternatively I could run 2 cells in series to run a 5V system overall, but this introduces challenges in recharging the cells it seems.
    Thanks for any advice or recommendations!

  • ZerotimE / about 13 years ago / 1

    I see these are back in stock, not sure why I did not get a notification as I had signed up to receive one? Come to think about it, I have never received any notifications for any of the products that I have requested. Is this feature working?

  • Hamid / about 13 years ago / 1

    Do you know when are you going to have more of these in stock?

  • cpmera / about 13 years ago / 1

    can anyone provide me the c programming coding to code the id20 reader to show the tag id using pic 16f877a??the tag id must be shown in computer screen..tx

  • Settorezero / about 13 years ago / 1

    Hi, I've written a simple software for testing with Innovations ID-12 and ID-20:
    More info on the download page. Hope it's useful, leave me some comments if you use it.
    Bernardo Giovanni

  • TheFlyingCouch / about 13 years ago / 1

    Hi, I'm wiring this to my uC with the RFID breakout board. What exactly do pins 8 and 9 go to? Since I'm using ASCII, the datasheet says CMOS and TTL (inverted), which doesn't really help me...

    • Settorezero / about 13 years ago / 1

      If pin 7 is tied to GND, module will use a serial output compatible with RS232 (9600,n,8,1) and then pin 8 must be disconnected and pin 9 is data out

  • cpmera / about 13 years ago / 1

    i've bought rfid id20 reader...i've tried to interface the id20 with pic16f877a to light up leds..the id20 interface was done by connecting pin 9(id20) with rx(pic)..bt when tag id was detected id20, the led not on..can anyone help us regarding this??iz there anything else need to be interfaced between id20 and pic??<br />

  • Diaz / about 13 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

    • Settorezero / about 13 years ago / 1

      Yes. Put pin 7 to GND and connect pin 9 of the module to RX pin of the pic. Set the UART to 9600 bps, 8 data bit and then get the data

  • I watched the video, but, the range that the ID 20 has is not the same as in the datasheet.
    What is the real range the ID-20 has?

  • siliconfish / about 13 years ago / 1

    I wrote up my Arduino interface, very similar to the earlier post (which i didn't see until i was done). However if it helps anyone get going, here it is:
    I did find it didn't read my HID tag from work.

  • tuxbear / about 14 years ago / 1

    Is is possible to separate multiple cards in range? Say I bring one card into range, keep it there and then bring another one into range. Will the second card get identified?

    • I don't think it will work like that. Read up on how RFID technology works to see if you can use it for your application:

      • Jon15 / about 13 years ago / 1

        Pretty sure your going to have issues doing this with this reader, however,
        Reading multiple tags is frequently done in industry with modern HF tags. Done though "telling" tags to choose a random number then asking each tag in order to report at each read cycle until it's improbable that tags in range have repetitiously chosen the same random numbers.
        Another thought:
        Readers I've seen usually record only one read if their are multiple tags in range with the same code.
        Adjacency is a big issue with RFID tags, its rough to read tags when they are close or touching each other

        • EliTheIceMan / about 13 years ago / 1

          I have two RFID cards in my wallet. They are for different places and may even use different frequencies but I doubt it. Neither works in either location when together but I wrapped an old gift card in two layers of foil and placed it between them. Now one side of the wallet works in one place and vise-versa.

  • lawrah / about 14 years ago / 1

    Is this able to monitor students within a classroom? Say a student walks in, tags themselves in, stays in a classroom for an hour and then able to tag themselves out? I.e. Is the reader able to read cards multiple times without resetting?

    • This is the basic function of an RFID system. You will need more than this module for this to work. Try searching for other people's RFID projects to see if what you want will work.

  • Is it possible to read encrypted cards / anyone have any thoughts on how this reader could be made more secure for a front-door entry application eg: paired with keypad and pin?

  • aio / about 14 years ago / 1

    is it possible to write a tag? i mean, can i write data to the tag with this?

    • sleeper / about 14 years ago / 1

      No, you would need an ID-20RW (or WR, the datasheet uses them interchangeably) to write to tags. Even then, the datasheet talks about using a different card format, the Temec Q5555.
      I don't know whether the Temec format is compatible with the EM4001/2 or not.

  • J.Peeters / about 14 years ago / 1

    Is it possible to hook up a self build antenna to this RFID module?

    • sleeper / about 14 years ago / 1

      Yes! The datasheet has some general guidelines to follow when building an external antenna. They even provide a website on the theory behind loop antennas.

  • jwm20 / about 14 years ago / 1

    I'm looking for an RFID reader, and my choice is between the the ID20 and the Parallax serial rfid reader http://www.parallax.com/Store/Accessories/Communication/tabid/161/ProductID/114/Default.aspx?SortField=ProductName,ProductName I am looking for one that will read tags through a door, which is 2" solid wood, but with thinner inset panels that are about 3/4". I could definitely fit either reader over one of these panels. Is it feasible to have a keychain-type RFID tag be readable through the door, and which reader would be best suited for this application?
    Thanks a lot!!

    • jwm20 / about 14 years ago / 1

      After having tested this for awhile, I am satisfied with the range. With no obstruction, the credit-card sized tags from SparkFun can be read from about 5-6 inches directly in front of or behind the reader, and from about 2 inches around the sides. Nonmetallic obstructions (stacks of paper, wood, etc.) have little effect on the range. The cards can be read through one layer of aluminum foil from about 1 inch, and not at all through more layers, not surprisingly...
      This works perfectly behind the door it was intended for, so I'm happy :)

      • If I put one of Sparkfun's 16mm RFID buttons on the back of my digital watch, do you think the ID-20 would be able to read it ?

        What about the ID-12?

    • sleeper / about 14 years ago / 1

      I have been experimenting with tags that have about 1" diameter antennas. I was able to read the tags through a 1.5" solid piece of wood. In fact, it read the tag 3.5" away from the face of this reader.
      I found the tags on a different site, which I will not post, since this is Sparkfun's site. A quick Google can lead you to a myriad of different tags. Make sure your encoding matches though.

      • jwm20 / about 14 years ago / 1

        Thanks! It looks like this is the reader I'll go with.
        And I'm going to at least start with the credit card shaped tags here at Sparkfun, and see where that gets me.

  • Rotciv / about 14 years ago / 1

    When using the Reset line to re-read a transponder, wait at least 200ms after bringing the reset line high, then read, and then bring it back low.

  • sleeper / about 14 years ago / 1

    great sensor. I was able to read cards through a notebook and a stack of paper.

  • Attie / about 15 years ago / 1

    What happens if you leave a card within its proximity? Will it continuously trigger and send the ID? or do you need to prod the reader to read a tag (if one is avaliable)?
    Is it ok to leave RFID tags "powered" for long periods of time?

    • SnuSnu / about 15 years ago / 2

      not a problem from my experience. the reader only reads once, and then if you want to read again, you'll need to cycle the power or reset the reader.

  • cewood / about 15 years ago / 1

    Can anyone confirm if this will read HID Indala cards?

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