Introduction: RFID Reader Detector and Tilt-Sensitive RFID Tag

The 'rub'
Want to detect the presence of RFID readers? Want to control when a RFID tag is active or readable? We describe how to do both using bits of copper and card, and some readily available electronics hardware.

Longer preamble
Radio frequency identification ( RFID) is rapidly growing in popularity. RFID tags are found everywhere. They're attached to container freight, in those funny-looking white labels you find in newly purchased books, embedded in many corporate ID cards and passports, etc. The tags have a few common properties: they transmit a unique ID number, are optimized to be 'read' from predefined distances, and are usually small so they can remain unobtrusive or hidden.

RFID readers are used to track nearby tags by wirelessly reading a tag's unique ID (see Figure 4); a tag simply has to be brought into physical proximity with a reader to be read. Readers are mostly used for industrial or commercial purposes, e.g. asset tracking or electronic payment. Wal-mart use RFID tags and readers in their supply chain. The technology is also used in mass transit systems in cities like London and Hong Kong. In Japan, many mobile phones incorporate readers to enable e-money payments in shops and vending machines.

For those of us who want to experiment with RFID, the problem is that the technology is almost always black boxed. That is, the inner workings of a tag and its interaction with a reader is hidden from view, and thus difficult to have much control over.

In the two exercises that follow (building a RFID reader detector and a tilt-sensitive RFID tag), we offer an example of how you can start revealing some of the workings of RFID and thus gain some control over the technology. The two exercises also hopefully show that the technology is relatively simple and how it can be extended to support some interesting interactions. We offer some other possibilities that build on our examples at the end.

Step 1: Material and Tools

This section provides an overview of the necessary materials and tools.

Materials (see Figure 1):
We need the following material to built the basic RFID reader detector.
- Cardboard (around 100x70 mm)
- Conductive copper tape (e.g., order number 1218478 at www.farnell.com)
- Capacitor 82 pF (picofarad) (e.g., order number 1138852 at www.farnell.com)
- Low current LED (light-emitting diode) (e.g., order number 1003207at www.farnell.com)

Tools (see Figure 2 and 3):
- Craft knife and scissors
- Insulating tape (e.g., order number 1373979 at www.farnell.com)
- Soldering iron and solder

RFID reader for testing (see Figure 4):
To test our RFID tags we need an RFID reader that can operate at a frequency of 13.56 MHz.
There many readers for this widely used RFID standard, for instance the Sonmicro MIFARE USB reader (http://www.sonmicro.com/).
Note: The Phidget RFID reader does not work with the tags created in this project, as it uses a different frequency for communication with the tags (125 kHz).

Advanced material (see Figure 5):
The following material is necessary to build the second part of the project: the tilt-sensitive RFID tag.
- Micro tilt switches (e.g., www.digikey.com)
- RFID ICs (e.g., MIFARE Standard 1k, part no. 568-2219-1-ND at www.digikey.com)

Step 2: Building the RFID Antenna

This step describes how to build the antenna for the RFID tag.

Building the RFID tag antenna
To build the tag's antenna follow these three steps.
1. Cut the conductive copper tape into thin stripes of around 2mm (see Figure 1).
2. Tape these stripes (see Figure 2) in loops around one half of the cardboard (see Figure 3 for the layout of the antenna). The tag should have between 3-4 loops for the antenna.
3. Solder all the connections between the copper tape. Sometimes, this isn't necessary as the tape's adhesive backing is conductive, but solder the connections if you want to be on the safe side.

Now we have created our RFID tag antenna, and we will add the "RFID reader detection" functionality in the following step.

A little background
RFID readers transmit an electromagnetic (EM) field with their reader antenna. This EM field induces a current in the antenna for all RFID tags within reading distance. This induced current activates the RFID chip that is connected to the tag's antenna. This chip then modulates a response (usually the unique ID number) that is transmitted back to the reader. The antenna of an RFID tag is usually a thin copper wire that is arranged in loops. The loops allow the emitted EM field of the RFID reader to induce current to the antenna of the tag.

Step 3: RFID Reader Detection

This step describes how to add a simple mechanism to the RFID tag antenna that allows us detect nearby RFID readers.

Antenna connection
First, we add a small piece of insulation tape for the connection of the inner end of the antenna loop (as illustrated in Figure 1). This is to insulate the outer loops. Then we add another copper tape strip to the inner end of the antenna as shown in Figure 2. Here again we solder the two ends of the conductive copper tape together.

Capacitor and LED
Next, we add the capacitor (82 pF) and the low current LED to the tag as shown in Figure 3. They are connected in parallel. We also solder these two components to the copper tape (see Figure 4).

Testing
With these simple steps, our RFID reader detector is finished! By bringing our DIY RFID detector close to an RFID reader (as shown in Figure 5), the connected LED lights up. With the Sonmicro reader hardware the distance to the reader has to be below 8-10 cm; however, there are RFID readers available with a stronger EM field and therefore a higher maximum reading distance.

In the next step of the instructable we will show how to extend a basic RFID tag and make it tilt-sensitive.

Step 4: Tilt-Sensitive RFID Tag

We now describe the process of how to build a tilt-sensitive RFID tag. This extends the previous exercise.

Antenna
The antenna for this second RFID tag is similar to the first antenna we built. We thus need another piece of cardboard and to repeat the steps described earlier in STEP 2 of this instructable.

Tilt-sensitive tag
Next, we add additional copper tape connections to the tag, as shown in Figure 1. These connections allow us to connect three tilt switches, a capacitor, and the LED to the antenna. Again, all the connections of the copper tape are soldered together.
We add the three tilt switches to the tag as shown in Figure 3. The tilt switches are soldered to the copper tape, and it is important to connect them in a slight angle (around 5-10 degrees) as shown in Figure 4. This makes sure that the silt switches are in a closed state while the RFID tag is in a horizontal position, and in a open state while the tag is in a vertical position.
Again, we also add an LED and a capacitor to the antenna as shown in Figure 3 (we use a different form factor of the capacitor here just to illustrate the alternative options).

Testing the tilt-sensitive tag
We can now use our Sonmicro RFID reader again to test our new tilt-sensitive RFID tag. The tag is activate while in a horizontal position as in Figure 5, and is inactive when in a vertical position as in Figure 6.

Using RFID chips
We can now replace the connected capacitor and LED from our tag with an RFID chip (e.g., the MIFARE 1k shown in Figure 7). By doing this, the activity of our tag is no longer visible through the LED, but our tag is then readable by the RFID reader and responds with the unique ID number of the chip.

Step 5: Variations

This section concludes our instructable of how to build custom RFID tags. Here are a few additional tags to show the possible variations.

- Variable length of the tag antenna, and therefore also variable reading distance of the tag (Figure 1).
- Experiments with the tag size and material (Figure 2)
- Switching between the LED and an RFID chip (Figure 3)
- Light-sensitive tag: the tag is active in daylight, and inactive in darkness (Figure 4)
- Touch-sensitive: tag is active when someone touches the tag with a finger (Figure 5)
- Different material for antenna by using conductive silver ink (Figure 6)
- Stamped layout of an RFID tag antenna (Figure 7) that is in fact working!

Many other variations of RFID tags are feasible... Happy DIY!

Comments

author
PenelopeS7 (author)2017-04-18

hi i think you might be able to help me. i need to make a set of wristbands that have leds that light up with the wristbands are in extremely close proximity to each other. both wristbands would need a tag and a reader. is this possible? and how would i do it? and what would i need? please respond ASAP

author
AnaF40 made it! (author)2016-06-23

Made the reader part. The LED glows very softly, but it works!

Photo on 6-23-16 at 12.33 PM.jpg
author
JohnathanW15 (author)AnaF402017-03-30

if you still have this/ever try it again.... I think non conducting tape over the first layer except for one little edge then another layer of coper joined to that exposed tap and laid over the insulator layer (connected spiral of copper tape > insulator tape) vertically would work a bit better. dont bother with inward spiral as author of tutorial showed. The coils in the devices are usually vertical stacks. If you do EE stuff semi regularly you should pick up a roll of whats called "kapton tape" insulates and can with stand the heat of a soldering iron(like under the copper tape...solder doesnt actually stick to it.) If you have ever seen the transparent yellow orange tape on a lipo pack or inside electronics you probably respect this adhesive already, every time i see it (even in old devices) it looks new and is still stuck where it should be. Nasa likes it as well if that means anything.

author
gdps67g (author)2016-07-19

Is there any way we can use a custom number in the RFID chip? Like, if I want to clone my office card into this? or will I have to go through some other methods?

author
JohnathanW15 (author)gdps67g2017-03-30

your first message about "testing purposes" and unique id tells anyone who knows the answer to this question that you intend to clone a card. you can make a tag from a single IC not intended for RFID/your proxi card and 1 to 2 other components for about 2 bucks. The not intended part means there are no limitations on what you can and cant program into it*. Usually it means you have to figure a bunch of shit out to do that but I know for a fact there is a tutorial online. The only hint i will give you is regarding the mcu/chip you need...its not where its from, its where its At. I guess some would say its the smallest of Mel's family. If you cant figure out what to search from that, you need to do a lot of homework before you will pull this off. programming will require a special but cheap board as well...maybe like 5 bucks for the programmer and then 2 bucks per tag u want...most people dont set out to make just one so the 5 dollar part is considered nice to have. Normaly id be more helpful but I dont know u and I dotn want to let script potential kiddies into places they shouldnt be..esp if they just copied and pasted someone else work to get in, nothing learned. Like i said, info is all out there, i know that for a fact.

*within the bounds of communication protocol for the flavor of tag you are pretending to be. aka send the reader french isnt going to work when it was expecting english. heck, french barely works when the french are expecting french but hear canadian

author
凯文校 (author)2016-08-15

Very Interesting!

author
gdps67g (author)2016-07-19

Can we make a custom RFID tag? or even a dynamic tag in which we could enter the unique ID ourself for testing purpose?

author
taifur (author)2015-09-18

Interesting work

author
perfo (author)2015-08-11

nice project thanks.

How forgiving are these antennae with resonant frequencies. Can the size be adjusted without much adverse effect or do you have to recalucate turns dependent on air core size etc? I would like to make an antenae that is about 2cm by 2cm. would that seem doable.

author
lazyafternoon (author)2014-06-05

Great project. Thank you for documenting and posting it. I would like to make one and have a few questions for anyone who might know....

1. Does it matter how the LED is oriented when attached to the antenna (anode/cathode)?

2. Do you know of any common stores that use 13.56MHz RFID readers where it would be easy to test without needing to purchase a reader?

3. Can the NFC in a cell phone (mine is a Galaxy S4) be used to test as a reader? Is it strong enough?

4. Does anyone have plans for a 125KHz version?

5. If you don't have an 82pF cap, can you group a couple 333s with a few 103s and be 'close enough'?

6. How important is the spacing between the copper strips?

Any help is appreciated. Thanks!

author
Iron MikeH (author)lazyafternoon2015-06-06

are you a pet stealer?

author
Iron MikeH (author)2015-06-06

why do you want to disable RFID tag? to steal something not yours?

author
JohnA15 (author)2015-03-25

what is the process of data transmission from tag to reader.

is there any boud rate consideratiion??

author
beyondal (author)2014-11-17

How do you determine the loops?

author
beyondal (author)2014-11-17

How do you calculate the windings for the flat planar coils?

author
djjrb313 (author)2014-10-20

I am new to RFID technology, but really enjoyed this! It is finally making some sense to me. I am going to try to do this project on my own, but one of the materials you listed does not seem to be still at the same product number as before. As I said, I am new to this and don't know the difference between the other products available when I search for similar ones. Could you provide a link that would replace or is the same product as this material:

Capacitor 82 pF (picofarad) (e.g., order number 1138852 at www.farnell.com)

Thanks!

author
mx28 (author)2014-03-24

hi. I am new to electronics. I have some basic knowledge of some things work but nothing about radio frequencys. would this light up or react to a cell phones rf? or something such as WiFi? I'm trying to make something that will light up or react when my cellphone goes off or I receive a text.

author
suilenrock (author)2013-09-08

Thanks for this great post! Can't wait to do it myself on my next weekend project.

author
dspecht2 (author)2013-06-09

This is a nice tutorial but it would also be interessting to see how you connect your antenna to the mifare RFID Chip. Is there also a tutorial for? Thanks!

author
dipenkhatri15 (author)2013-03-18

Hello,

I want to make UHF tag with 865 to 868 MHz . what you should i have to change in above material to make RFID tag?

author
bluestreak101 (author)2013-01-11

Hi,

Nice RFID instructable! I have a project in mind for an RFID reader, I have a specific requirement for the antenna's placement and wondered what I need to take into consideration. What materials are suitable power requirements number of loops etc etc. Are you able to help me?

Thanks

author
ScottSEA (author)2010-11-29

You should change "stripes" to "strips"... otherwise, a very nice instructible.

author
mcmchris (author)ScottSEA2012-11-11

"Instructable"

author
Electron229 (author)ScottSEA2011-08-04

Who cares.

author
DoctorDv (author)2012-04-28

I am new to electronics and RFID, but how does the LED get the power to light up? Thanks for the great post!

author
AJMansfield (author)DoctorDv2012-10-07

Magic.

In this particular instance, it takes the form of a series of ripples in the fabric of the universe that can propagate across space. This form of magic is commonly referred to as an 'electromagnetic field'. The RFID reader creates an electromagnetic field nearby it that induces (induction is the process through which a changing electromagnetic field creates voltage across metal objects) a voltage (a term used to refer to the total difference in the amount of positive and negative magical energy between points) along the length of the antenna. The LED then allows the positive and negative magical energies on either side of it to pass through it, annihilating each other in the middle, and creating another type of magical ripple (commonly called electromagnetic radiation) that you observe as light..

That is also the same reason that metal sparks when you put it in the microwave (I have personal experience doing this...), because the microwaves induce a (pretty high) voltage across the metal, enough to make sparks jump.

author
DoctorDv (author)AJMansfield2012-10-07

Wow! Thanks!

-Doctordv

author
Dave Kruschke (author)2012-08-21

I used some of the information here to successfully design and create a RFID Reader Detector that operates at a very low standard frequency, 125 kHz. SparkFun and others sell devices that operate at 125 kHz.
Because of this much lower frequency, my antenna coil and capacitor have much large values that the device described here. My Instructable also includes the math that underlies the selection of coil and capacitor sizes. You can find more about this if you can successfully go to
https://www.instructables.com/id/RFID-Reader-Detector-Easy-to-Build/.
Also, it is important to remember that a RFID Reader is a completely different device than a RFID Reader DECTECTOR. My device merely lights up if it is close enough to a Reader that is using/emitting a 125 kHz signal...

author
LurkyTheHatMan (author)2012-07-25

This is a fascinating project. I've been looking for a way to build a (very) cheap RFID reader, and I was wondering, have you tested this as an aerial for a reader?

author
oshe (author)2012-07-07

i would like to know about the RFID reader if it is universal..
or it can read any tag...

this is so nice...it really helps...

thank you..

author
francisroan (author)2012-05-31

do you know how to make an rfid "reader"?

author
Maknum (author)2012-05-21

Can you make the antenna as big as anyone would want it to be? For example: half a metre? I am making an gramophone-like player for kids. Where they can place cubes that represent different tones on the "installation". But all RFID antenna's that are for sale are to small for the radius.

author
DoctorDv (author)2012-05-11

You should enter this in the kit challenge.
-Doctordv

author
jnandakumar (author)2012-03-01

Please tell me why the tilt switches are required?

author
dhruvil_shah (author)2012-02-03

Can you please tell me the dimensions of the antenna you have made along with the spacing between two loops?

Thanks!

author
yaly (author)2012-01-10

can i use nickel tape instead of copper?

author
robertrunyon (author)2011-12-19

Would it be possible to use clear nail polish, instead of the insulating tape, to cover the the antenna loop where the antenna lead crosses?

Also, would it b epossible to use a "zig-zag" or "back and forth" pattern instead? This way it would be to possible prevent the crossings in the first place.

author
kgee (author)2011-09-12

Nate Marquardt? lol

author
pentagon123 (author)2011-06-11

Cool :)

author
i805 (author)2008-11-18

i very much enjoyed this inscrutable and very educated too. would it possible to use a thin copper wire(0.1-0.5 mm) i pulled out of a small mooter ? from my understanding if i were to be near a shop with RF reader(those that prevent stealing)will it light?

author
nmarquardt (author)i8052008-11-18

Yes, this is absolutely possible. You can use thin copper wire for the antenna; in fact, most commercially available RFID tags use this material for their small integrated antennas. I've added a small image that shows such a tag and the thin wire of the antenna. However, if you create such an antenna by yourself, you have to do a few experiments with the length of the antenna wire as well as the number of loops. About your second question: you're right, a few of the security systems in stores use the 13.56 MHz RFID technology, so the LED of our simple detector would light up (I tested it :). However, quite many stores use different (sometimes proprietary) technology, that also uses a different frequency and protocols. In this case, the detector in its current form would not work, but you can modify the design (antenna, capacitor) to work with different RFID hardware and frequencies.

RFID-wire-antenna.jpg
author
i805 (author)nmarquardt2008-11-22

thanks if you say I'll have to try different lengths and loops than i give up cause i don't think it will be appropriate doing this near the RFID reader in the shop. another Q if the led will light will the RFID reader will beep too(in the shop)?

author
nmarquardt (author)i8052008-11-22

No, these simple RFID detectors (via inductive coupling) are usually invisible for the RFID readers in shops. Furthermore, the RFID readers for security in shops usually respond to a specific signature on the chips. However, sometimes they are tuned very badly, which means they give a lot of false alarms, and then they might also give alarm when only this simple circuit is near the RFID reader. In all cases where I tested it, the security RFID readers in shops never gave alarm.

author
i805 (author)nmarquardt2008-11-28

thanks i went down the mall to a clothing shop and saw a rectangular plastic attached to a clothe,only the cashier can separate it with a sort of a device, do you know what is the technology of the this(-the separation- i know there is RFID chip inside the plastic). for education purpose only .

author
larryd2241 (author)i8052010-11-28

There is a magnet in the device that releases the little fingers in the tag

author
nmarquardt (author)i8052008-11-28

I know what you mean, but to be honest: I don't know how this mechanism works. As you mentioned, the 'security' part of this inside works with RFID technology as well. But for the 'separation' part of this, I have no idea of how it is implemented (and I'm sure the company that is producing these security parts is happy about keeping their secret :-). I could imagine it is some kind of a special electromagnetic field that is releasing the security tag (with a specific pulse pattern?). But this is just a guess; maybe someone else has an idea of how this could work.

author
i805 (author)nmarquardt2008-11-29

thanks anyway for your kindness and taking the time for answering :)

author
el greeno (author)i8052009-01-14

I believe its just a magnetic catch, which can be seperated using a strong magnet. I saw it on a police programme in the UK where they caught a shoplifter with a massive magnet in his pocket.

author
zimmemic25 (author)nmarquardt2008-11-29

there are some rfid stickers which have just 3 different shaped metal sheets laying on each other, how do they work?

author
cooldog (author)2008-11-11

if you add more conductive boxes to the RFID tag reader will i work at farther ranges

About This Instructable

282,599views

526favorites

License:

More by nmarquardt:RFID Reader Detector and Tilt-Sensitive RFID Tag
Add instructable to: