How anti-theft tags work - magnetostriction
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- čas přidán 1. 08. 2024
- Anti-theft tags contain a tiny mechanical oscillator that is activated by a magnetic field. The detectors at a shop's doorway can detect the oscillation magnetically. The tag can be activated and deactivated by magnetizing or demagnetizing it, respectively.
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Matthew Hill
Erik Saathoff
Max Loutzenheiser
(better credits titlescreen in the next video!)
Support Applied Science: / appliedscience
Sources:
www.metglas.com/products/magne...
www.google.com/patents/WO1999...
patents.google.com/patent/WO2...
www.google.com/patents/US4510...
www.google.com/patents/US4298862
en.wikipedia.org/wiki/Magneto... - Věda a technologie
After watching this video I got a notification: "Your shoplifting skill increased to 21!" Nice.
I guess we should be carrying a strong magnet everywhere hahahah
@@orti1283 u obviously didn’t watch video u carry a magnet u ain’t stealing shit but ur own freedom
😂🤣🤣🤣🤣🤣
Wow this looks fantastic. One tip, when demonstrating objects as small as these, a closer camera angle would be great!
I had to stop watching. Too frustrating trying to make this out. The traces on the O’scope were also too difficult to see.
Need some closeup views.
This desperately needs close ups. Even if they are not live, just record the close up separately and overlay that video while you are explaining things.
Thanks for explaining how these little buggers work!
Even just a little closer on the whole video. Do we really need to see the wired and how it is hooked up after you are done explaining the setup? Having the oscilloscope square and straight to the camera would make a difference too.
Great video Content! Keep it up!
I guess he listened!
Your use of the CD tracks to measure the movement was brilliant! I loved that. Great video overall, although I would have liked at least one close-up shot of the strips near the beginning. I'm sure they're basically featureless, but when you first took them out and were handling them I found myself wishing you would show a good macro shot of them.
The lever solution is genius
+Barack Lasagna | Why not use a small mirror lever and have it deflect a laser? You see the results on the wall where the beam hits. You wouldn't even need a microscope.
+Nehmo Sergheyev great alternative
+Barack Lasagna Could have been done with a laser pointer instead, wouldn't need a microscope then and more sensitive too.
+Barack Lasagna Although I would be concerned about the field from the coil slightly attracting/repelling the hardware for the lever, causing movement that's confused with the magnetorestriction.
+Barack Lasagna I think you meant the lever solution is ingenious; Ben is Genius for sure. Only people can be genius. However people and things can be ingenious. All that to say, your screen name IS ingenious. Love it! He's been like a flat, wet noodle, covered in cheese as president.
Nice opening shot. Very clean.
But I like seeing a messy lab in the background just as much. I watch because it's about the science.
And I have always been curious. Will have to re-activate one of thee things and take it through a store to try this out!
+Matthias Wandel To deactivate them, it works the same as the old degaussing coils on arcade cabinets.
+Matthias Wandel I love how you comment on other channels Im subscribed to!
+Matthias Wandel Don't worry -- the messy lab is not going away! I like the junk chic as much as anyone.
+Applied Science Everyone knows that there is a positive correlation between the amount of shit on your bench and the accuracy of scientific data collected.
Matthias, just make a (woodworking) contraption that magnetizes and demagnetizes it, so that it's turning on and off every couple of seconds, and then enter a store. This can be quite funny.
And I'm wondering if it"s actually possible to set the alarm of from a big distance (50meters), it should be.
I always cut the tags open and save the loose metal strips, as they're perfect for shimming lock cylinders for rekeying.
Brandon Fesser I tried but they cut me
I've never come across ones with exceptionally sharp edges. Tap on the tag so the strips fall to one end. Use scissors to snip-off the opposite end. Pour the two free shims out. The third strip isn't worth salvaging.
Ironic, using anti-theft tags to pick locks.
You must be the Lock Picking Lawyer, but you are under cover conducting research for your next video to shame lock companies! My lips re sealed ( wink, wink ). HAHAHA
All my young years in retail I always wondered how those tags worked. Thanks Ben! Love the new lab diggs too... :-)
+DRC Paintball I've had some look at the internals of sensormatic stuff and from what I remember they have equipment to also rearm tags right? Not sure how they do that... I remember all the sensormatic boxes I had with huge 400v capacitors in them. I also remember that not all tags are even deactivated, the long clothes tag just has a special tool to remove it (that tool has two of the sticker alarm tags inside ironically) but stays armed. There was an electronic one as well with a battery inside that'd alarm if someone tried to remove the tag without using the special tool (I've got a test tag), did shops ever start using them?
+DRC Paintball What do you mean by "in phase"? Do you mean the alternating transmit and listen phases should be in step at all gates in the store? Since there is no network between the different gates of the store, how would syncronization work?
Also, what causes false alarming when the store is closed for the night?
+DRC Paintball Thank you. How often does the transmitter transmit? Do they get any sync help from the mains AC? Otherwise, it seems like you would need atomic clocks in each gate to have different gates independently keep in sync to the precision required.
+gluino This is what you call Job Security.
i hate retail. lol
Some anti-theft tags use an amorphous ribbon with a very square B-H loop and a very low coercivity, in fact the earths magnetic field is strong enough to magnetize them in one direction or the other. The transmitter coil generates a pair of fields at two different frequencies and the amorphous ribbon acts as a non-linear magnetic mixer generating fields at the sum and difference frequencies. Say the transmitter generates 5kHz and 8kHz then the sum and difference will be 13kHz and 3kHz respectively. The receiver coils pick up the 13kHz and sound the alarm. To deactivate the tags a small piece of steel adjacent to the ribbon is magnetised and that keeps the ribbon saturated.
The level of scientific intuition here is amazing, how you choose the right methods to investigate and validate set assumptions. Thumbs up!
Thanks! I really love your detailed explanations of stuff. I've watched your most recent videos since subscribing about 6 months ago, but still catching up on this older content. So, so nice and thorough. It isn't flashy or anything, just very clear explanations. Please keep it up.
Wow - These videos make me so happy! I studied electronics, electrical and telecommunications engineer for 10 years and you bring several concepts together in a very simple and beutiful way, like different sounds in a orchestra. Amazing!!! Congrats!
great video and analysis. love the spring jig.
Fascinating as always, Ben! I never knew how those strips worked (and I admit to opening them up to see what was inside). You gotta love all of the uses for Kapton tape...
Looks 😮 hi u😅😅hgh o qpp😅 No n to p
I guess I always assumed these were some kind of primitive RFID tag and never thought about it. Very interesting!
Love the new setup, and I really love the quality content you're putting out.
I check for updates daily and slightly bummed when there's non, but never disappointed by what you put out when you do upload something new :)
you just keep going deeper and deeper into it...some of the topics you explain in detail and some other you brush off... overall it's amazing... and like your original intentions, these videos motivate me to try my own experiments....
Your production quality is some of the best on CZcams, if not the best. Good work, great lesson.
Beautiful work (as always).
MANY thanks for taking the time and trouble to research this topic, construct the apparatus, eliminate the bugs, record the video, edit and post it.
That was totally awesome !! Never seen any object move such a minute distance ever and with just bits and pieces.to demonstrate it.Fantastic!!
Even though I don't understand half of what you're talking about, you present your findings in such a way that keeps me watching. Thank you for keeping me interested ;-)
This guy is clever! This channel is one of the most high level in the internet! Congratulations for this incredible work!
I just want to let you know that here in 2022, I am re-watching all of your content for probably the third time. Your videos could be 3 hours long and I would still be dismayed when they're over.
In the first minute you may think it;s not interesting, But you MUST SEE the complete lengh of the video,!! This guy is amazing, in his complete setup, Great setup and a great Research, Thanks for sharing !!!
Amazing video! I love your ingenuity in the testing setups. I learned a lot!
You are so cool Ben. I'm a computer engineer of '14 and I wish I could be a quarter as awesome as these videos. Your projects are inspiring.
Very thorough investigation! Those things are actually pretty ingenious, I'm impressed.
Wow your new lighting looks so pro!
Very interesting, I especially like the meter you made to measure such slight movements. I use the strips as shims in my home machine shop, because their thickness is between .0005 to .001, for example; when I have one of my lathes preoccupied with a four jaw set up, that I can't break down, I'll use another lathe that has a three jaw chuck, test run out with a workpiece in the jaws, and fill the high spots with two or three of those strips, to get as close to a four jaw reading, if at, times, even better. I was commissioned to build a micro wire straightener 2. Years ago, and, as you may know, the straightener parts had to mesh as perfect as a Swiss watch, suffice it to say, I placed at least ten of those strips through the machine, and when their assessor tested the little machine he certified it as passing, as a Swiss watch, not knowing of the security strips turned shims...rotfl 😃
The whole explanation showing the expansion is great.
Now this is a VERY in depth video on how the magnet strips work
It doesn't matter which is the subject, this guy makes an amazing video and explanation.
How in the world have I never found this channel before!? This is great!
Glad to see your video equipment improving, but more importantly I'm glad to see youre happy about it :)
And suddenly I spent a whole evening rewatching your videos. Much better than some silly discovery documentary ☺
Great videos.
I wish all youtube channels had this good sound!. Nice work, and informative video as always :)
Wow. The determination to measure it 👍🏻👍🏻 huge props.
This is exactly the detailed explanation I was hoping for, thanks!
Great content as always. Sound and lighting are greatly improved - nice job there too!
Hi Ben;
Many years ago, mid '80s, ASIR, I had a magnitostrictive delay line. It was from a mid '60s Friden calculator. Unfortunately I have lost track of it now.
This had a long steel wire carefully supported and coiled into a spiral. The transducers at each end had 2 tiny strips of the magnetostrictive material spot welded to the wire at right angles. There was a small coil around one of the strips and a small bias magnet in the coil.
Both ends were made the same.
When I pulsed the coil it would cause one strip to lengthan and the other to shrink. This applied a twist to the wore which propagated down the wire.
Of course, at the other end the strips were forced to stretch and shrink inducing a magnetic field in the coil.
You could easily see the delayed signal on a 'scope.
I speculated that it could dynamically hold about 8k bits of data. Maybe more, probably less.
I didn't have a micro yet so couldn't actually see if I could recirculate any data through it.
I have there been any amateur attempts at making such a device?
redrok
redrok.com
Yes! I immediately noticed the upgrades! So good to see you are making it :D
This is very cool and I appreciate you doing original research to investigate it. This is why I started watching CZcams
I've wanted to know this for a couple of years now, I've really wondered how these works.. Wow, Thanks for taking your time to investigate and share the results with us! =D Great video!
Very, very good video! Your test and observation methods are very creative! Thanks for your hard work and video!
+Applied Science, you're always answering the questions I didn't know that I wanted to ask! Thank you so much for your videos! I can't get enough of them!
Thank you for such a detailed explanation with excellent visualization
Fascinating video. I often wondered how this sort of tag worked. Of course everyone now knows how to defeat them. Like the upgrades.
Thanks for the videos! Congrats on the new setup, but as someone else pointed out, I am here for the science.
This is amazing! You've expose the beauty of the everyday. Thank you!
@6:06 this piece is called the "Bias Magnet" and it provides the Magnetic Bias to put the resonating Magnetorestrictive thin metal on the resonating point on the curve. If the magnet is not present (Deactivated Tag) then the Magnetorestrictive piece of metal is still the same but will be displaced to a non resonating state on the curve.
Makes absolutely no sense like most of your long winded comments.
Great, intelligent video! Thank you for increasing the quality of CZcams!
When i see titles of your video, i have no idea what it is about. But the moment i start playing, i m lost. Thanx Ben, keep videos coming.
These videos are so fun to watch. Oh, and informative, too.
Excellent video! Love the improvements!
A very interesting topic.
Nice practical experiment setup!
Excellent method for showing the change in length!
Thank you for being a great teacher. I learn a lot of things on this channel !
Brilliant apparatus, btw
the experimental setup was awesome
Great video! A quick note: While the maximum displacement under static field might be ~several microns, that is only under static field. Fluctuating the field at the resonant frequency of the metal plate will "ring the bell" and cause greater and greater displacements
I will apply this knowledge to my future shoplifting endeavours. Thank you.
excellent explanation and demonstration!
Great visualisation with lever and microscpoe!
Thank you for making these videos with so much care, I highly appreciate that you explain things so deeply! The video qualuty is also very good. Next improvement could be more close ups, I would like to see the small piece of metal, the graph and your measuring apparatus in more detail. If you have enough time to edit :)
Don’t let let ben fool you, *he’s so committed to accuracy he actually committed many counts of grand larceny just to get active tags for us*
You are a really, really good presenter! Awesome presentation!
Hi Ben.
Thanks for the video, it was enjoyable as always.
If your still interested in this topic you may want to try using a strain gauge to estimate the saturation magnetostriction.
If you glue the strain gauge directly to the ribbon surface with any brand of cyanoacrylate and then monitor the change in resistance via a wheatstone bridge configuration while slowly rotating the sample/applied field you can quite accurately estimate the saturation magnetostriction using the know gauge factor. We use this method in the lab I work in and so I can assure you its possible to achieve sub ppm resolution. I wish I could point you in the direction of a few papers on the topic but its very poorly documented in the literature.
If you have any questions about this, or on magnetic materials (especially nanocrystalline or amorphous materials) in general feel free to drop me a line.
Richard
+Capo Interesting thank you.
I can't believe the people who disliked your great video. I can only assume that those were the ones who wanted you to tell them how to defeat the anti-theft tags and have no science background to figure it out themselves.
Fun and informative experiment! This was really fun to watch you do. I had a good chuckle when you mentioned over-magnetizing one of the strips. Gotta experiment to learn. :D
love your detailed videos, explaining every-day physics!
I know your brother, dirty
Thank you for such an enlightening video! Technical details on AM tags do not abound in the web. A hug from Argentina.
Optimally used existing resources... Hats off sir
Thanks for this! I work in retail and have been wondering how those things work for a long time.
Thank you for an excellent experiment! Well done!
Another great video!
The curve of magnetic field vs mechanical output is the same as magnetic field vs recorded signal for audiotape. Tape recorders apply bias to the recorded signal to move the recordings into the linear portion of the curve. Some cheap cassette recorders use a magnet for DC bias, but most use AC bias around 45 khz.
If you don't stop hacking my Tennants you're going to jail
I learned about this by pranking shopping carts attaching the tags to the underside.
inademv it's a periodic pulse the energy was stored in the resonating metal strip which then continue to resonate in a dampened amplitude for a certain amount of time after the pulse ended. The anti-theft tag actually doesn't add any energy to the system it actually takes away from the energy transmitted in order to induce its own oscillation but the receiver isn't looking for that it's looking for the continued oscillation after each pulse goes quiet if the pulse stops and the receiver no longer hears anything and no tag is passing through but if the pulse stops and there is still a ringing coming out of the system then it must be from the tag
Wrong person sorry
Buahahaha genius
Definitely true.
That was a brilliant way of describing the anti theft device and a way to measure its movement. However even in it's simplicity, I don't think too many understood it. Great demonstration.:-)
He scienced the shit out of that.
dude ur amazing just dnt stop i know my generation is not interested in science and u deserve more
i learned on ur channel compared to school .
ur the best just keep it up.
You use the deserve more line on everyone
Very clever way to measure the movement of the metal.
thanks for explaining magnetostriction, very clear and concisely!
just noting that this is the most common tags used in retail. there are others, like the square ones with the metallic spiral. most made in China products will use the cheaper strip
Nice and clear explanation.
Thank you for making such a wonderful video . It cleared lots of doubt.
My understanding was that the use of a strong magnet would saturate the adjacent hard steel where its coercivity would leave it in a permanent magnet state that was just right for generating the ring-down pulse. To deactivate you had to de-magneitze the hard steel strip, so at the checkout counter is actually a zebra stripe type magnet that will de-magnetize the strip when the tag is swiped past it. The reason for this is that many ne'er-do-wells would think think they could defeat the tags by magnetizing them., but would in fact, make sure the tags were fully activated. Also another part of the design is the plastic separator between strips is slippery Teflon, so that the strip can resonate without being too quickly damped.
Fascinating, thanks Ben!
good video.. very detailed explanation.. clearly you have put in a lot of effort in making this video.. I appreciate your work..
One thing you forget to consider is that under the 58kHz excitation, the strip is resonating. The amplitude of displacement is roughly Q times the displacement under static (DC) excitation. Here Q is the quality factor of the resonator. From the ring down, Q is not small (most certainly more than 100, possibly more than 1000). So in the end, it is indeed theoretically possible for the strip to develop 0.1% strain (1/1000 inch over 1 inch) at its resonance frequency (12 ppm * 100 = 0.12%). These being said, the lever setup is quite neat for static test!
If you can't impress them with brilliance, baffle them with bs. 😉
Very interesting video. I never thought about how these worked.
It is important to note that metal strips are of two different ferrous alloys. One is a type of steel, as this becomes a ‘permanent’ magnet when subjected to a magnetic field. The other is iron, in that it responds to a magnetic field but resists becoming a permanent magnet. The plastic container is water proof to prevent corrosion of the metals strips within. The device is ingenious and the presentation in this video of how it works is pure genius.
Thanks for the wonderful video.before watching the video, Today i found one of this srtip and cut it apart to find what is inside. I found metal strip and three more strips i thought they were plastic but flame test confirmed that it is metal. I searched many videos but you explained the working principle. Thanks again ❤
Great Video ! keep it up with the good work, i liked a lot of the solution you have found to mesure the dilation
Great work, as always!
Good and informative as always. Keep it up!
Superb explanations !
Amorphous metals! Love that stuff. Have a piece of a Fe-B alloy that CSIRO were experimenting with in the early 90's...
These videos are just awesome & hope u keep making them
I Really enjoy your channel, I just wish I could understand what your doing. Most of what you do is way over my head, but I'll figure it out one day and your videos help!
Brilliant work as always!
Sir, you are fantastic! I learned something today.
when I have kids, they are watching this channel instead of cartoons.
that lever rig blew my mind. Genius!
+Jesse Guerrero The rig was awesome, but it may be flawed. He may have not been measuring expansion/contraction. What about sideways movement from the electromagnet pulling the tag around at 58kHz?
first time i have seen one of your video's. very very informative, have wondered for a long time exactly how those tags worked, now i know. keep up the good work, please ignore the slackers / idiots / thief's . i have subscribed.
5:26 The funny thing is: They are going for the inductor-cap combo a lot of the times, but they make it out of aluminium foil and between two plastic/canvas sheets and that's it. It's working, it's flexible and it's way cheaper than even these metal strips.
It's just some spiral shape with the ends folded over each other while keeping those insulated to form the inductor and capacitor.