EEVblog

What's inside an old style bank note/bill accptor/validator for vending machines and the like?
How does it detect genuine notes from dodgy ones?
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[@edwardbyard6540]

Oh it won't accept the note because the enable line wasn't pulled low, so it just rejects everything. Depending how you interface to the units (ccTalk/serial) needs a command to be sent to it, to enable the unit, or parallel you just hold one of the pins low to enable. The reason is that you don't want a note to be accepted before the host controller is ready...else people could lose their money! I should send you a pokie machine controller to teardown...

[@DaBoaringDragon]

"Yanks are laughing at me" We're only laughing out of a mix of sympathy and misery, from having too many of those things spit out our bills, for whatever reason. A crease, a speck of dust, we looked at it funny, we didn't speak politely to it, our political views are different, our religious beliefs are different...

[@rich1051414]

LOL. I always wondered if these machines have something against us Americans or if they are such a pain in the ass to every currency.

[@sonbrother6167]

its just our stupid monochromatic until recently linen currency.

[@tracyscott3261]

Oh I'm sorry you took that personal but honestly I have no idea who you are.

[@pratya1982]

Da Boaring Dragon ผ

[@diontarrant5805]

lol

[@WarpRulez]

I bet the symmetry of the leds and detectors is there solely to allow the bill to be inserted either way, rather than to add extra security. In other words, only half of the sensors actually do the detection (which half depends on which side up you insert the bill).

[@jonandersonmd7994]

Excellent (and non-obvious) point!

[@aladaris]

-"In God we Trust" -"Hmmmrrr" xDD

[@scotshabalam2432]

It always freaks me out a bit when Dave goes from a shot where it's powered up on 120V and he goes to the next shot of him taking it apart, touching contacts, and not showing him disconnecting the power.

[@christurnblom4825]

On a side note: has anyone of y'all who know about American history ever noticed that almost every president on U.S. notes are the presidents who fought hardest to prevent the banking system that runs the U.S.? I have wondered if they decided to put them on their bank notes as a kind of "fuck you" to the "useless eaters". The only one or two presidents that are on the bills that didn't fight against a central bank are on the high dollar bills that are rarely even used.

[@dudeguy242]

18:15 anyone else notice the NSA chip directly to the left of the Lattice? made me chuckle lol

[@RocRizzo]

NSA is ALWAYS watching!

[@SteveM45]

No its a LDO Regulator.

[@fadecutmike]

it’s not a chip..

[@WillOnSomething]

I love when people see the word "NSA" on something they assume it's a surveillance program. Someone found a file inside the Windows XP registry named "_NSAKEY" and the fake news started spreading that Microsoft "installed a NSA backdoor" in Windows

[@PaulJosephdeWerk]

I used to design systems with similar units. By themselves they don't accept the money. What happens is they send a set of codes (good/bad bill, denomination, etc) to the program monitoring the bill acceptor, and the program sends back another code to accept or reject. It allows the main system to decide what denominations to accept, and what to do with counterfeit bills.

[@naseweisz]

Maybe it pukes the note back out because it cannot tell anything that it has eaten a dollar note. Imagine if the controller of a vending machine dies and the note acceptor still has power and eats all the notes without the money actually being accessible.

[@arcadeuk]

Thanks Dave, this video was right up my street as an interesting tear down to cover :)

[@cjbeckersf]

I still haven't figured out how he knows my Uncle Bob.

[@mrbluenun]

An absolutely fascinating video, thank you so much.

[@KB1UIF]

As always, good job Dave. Thanks.

[@JohnDoe-gm5qr]

Look ALL over that 5 dollar bill with a GOOD magnifying glass, there a lots of micro printing.

[@EEVblog]

Yes, huge benefit!

[@whuffo]

The encoder wheel on the drive is part of the bill verification; there's a magnetic head the bill runs over and the number of pulses / frequency is checked. The encoder wheel insures that the frequency detection matches the bill speed.

[@vjk889]

Even though the sensor mechanism looks simple, I don't think it would be all that easy to fool. The LED / phototransistor pairs around the edge measure the light transmission profile through the bill at at least 2 wavelengths. The LED / photodiode arrangement in the middle looks like a fluorescence detector, one for each side. The way they're arranged, they probably also measure transmission down the center of the bill. Taken all together, I think it would be extremely difficult to produce the same sequence of signals that a real bill would give off

[@MarkFunderburk]

I won't get butt-hurt over the funny-money comments. I and many other Americans I know have ripped on other countries notes before, so it's fair enough. And I think your money looks pretty cool actually.

[@morelenmir]

Fascinating as ever Dave! Thumbs up.

[@heavymentalkings]

Very informative video though. I must admit you did a great job of explaining the circuitry. Thanks.

[@birminghamreefer2733]

You used to be able to spray saltwater into bill readers and short them out and the machine would spit out all the contents, the vending machines outside of where I used to work were always robbed of their contents, change money and goods. But I'm sure that new modern machines are better designed. Love your blog keep em coming.

[@dinkc64]

Yet again - love the video and the humor, great job Dave! :)

[@thysonsacclaim]

I will say, that for cotton money it is pretty sophisticated at certain denominations. The biggest thing is that for a while, we really didn't care that much about bills below $20. What's really cool that many people don't know is that we also had $500, $1,000, $5,000, $10,000, and (only for internal banking transfers), $100,000 bills. Now yeah that might not be impressive compared to countries suffering inflation (poor Venezuela), but is a lot for a country's normal bills.

[@rsmith155]

Adam Lawson thats dumb

[@thysonsacclaim]

Randall Smith wow such comment. Thanks for bringing intelligence to the discussion.

[@rsmith155]

Adam Lawson explain how making denominations that large isn't dumb. The idea doesn't need a detailed explanation from my end..... It's clearly a dumb idea

[@thysonsacclaim]

All of the denominations above $100 were used in the days before electronic banking. Making large denominations before the days of credit cards and ubiquitous banking was extremely common. They were mainly used for large transactions between banks and other institutions. You also don't seem to realize the other reason for needing large denomination currency, and that's the effect of inflation. In Venezuela for example, the currency has lost so much value that people are literally weighing it instead of counting it. It's currently trading at 1,000 Bolivars per Dollar. In other words, a 100 Bolivar note is now worth 10 US cents. In times of prolonged inflation, it's very common for governments to monetize large denomination bills to avoid people having to carry around trash bags of cash to go out to eat.

[@vinnie4g63]

I'm a vend technician in the us. Cool video, Ive never gone that far into a validator before. The reason it didn't accept your bill there is because a lot of times the validator requires a response from the vender (vending machine) whether it acknowledges its input. Nothing worse than putting your bill in and not getting your food. As you say across the pond Cheers mate

[@oorcinus]

The second optical sensor and the tab might be for detecting if the bill stack casette is full or not, methinks.

[@ncrdisabled]

I worked for NCR for 10 years . I have 10 different models of those. I had to replace and rebuild them in ATMS . I also had to work on the whole ATM and a weird way I had to do diebold . NCR was trying to take business from them. I have rebuilt over 500 atms from the wiring harness to the safe. I still have the complete schematics for all NCR and diebold ATMs. You should see the schematic for the bill acceptor I also worked on a whole lot of of other ones like in a self serve cash registers

[@1Bonehed]

You're a very smart man & I've learned so much from your vids, so please don't take this in a derogatory manner, but for future references, the storage area of a bill acceptor/validator is referred to as a cash/stacker box. I've worked on many of these & that was a brilliant guess on stacker capacity, those usually advertise to hold 500 bills (maybe clean crisp bills). The ink used on U.S. bills use magnetic ink strategically to create specific patterns at specific points on the bill. There's allot of timing involved for it to validate the bill, dirty/slick belts & dust on sensors is the problem 90% of the time. Majority of the time...99% of them are set to pulse 4:1 (4 quarters per $1. Allot of the equipment also accepts quarters) Those are actually pretty reliable little bill acceptors, used in allot of equipment. JCM is the big boy of Bill Acceptors/Validators & you'd prob find their publications online quite interesting. Anyway, great vid as always. Cheers

[@EEVblog]

The US adopted it as their "official motto" in 1956 to counter the perceived thread of the big red Soviet atheist hoard!

[@fdutrey]

I know a guy who once dated the flatmate of a friend of the PCB designer. He now refills vending machines.

[@FyberOptic]

I haven't heard that one before. It's always fun to learn new sayings from other countries.

[@AndyPhu]

that is one of the nicest five dollar bank notes i have ever seen

[@vortimemes]

Your right considering that we put lots of cocaine (and fold it) (and drop it into sewers) (and trample it).

[@XYR42point98]

Fantastic video!

[@mrdanker6756]

MEI (Adopted by Crane National) is the most reputable bill validator manufacturer, for reasons of reliable product. I personally give kudos to CoinCo for making the most modern communication protocol which is a lot better than the older stuff, though their validators seem to break a lot. The LED status table is usually for a light on back underneath the bill stacker. Older ones that use high or low level pulse protocol (24v = low, 120v = high) you'll likely need to upgrade to accept newer bills. That may be why it's not isolated, it used to use 120v for communication. The tab you were looking at is probably for the back of the large rectangle (looking at the part the dollar slides over when inserted). That part moves forward to push the bill into the stacker, then moves back. Usually it'll take the bill in, hold it in "escrow position" while it calculates, then either stack it or return it. Usually flashing the EPROM they want you to use some weird device they got that hooks up to it externally.

[@miguelash886]

Sir, even though you don't really need it, you have earn my respect.

[@DrEnginerd1]

That's so awesome! We programmed the mc68hc11 in school, so cool

[@EEVblog]

Polymer notes last longer (about 2.5 times). A Bank of Canada study showed polymer notes have a 29 per cent to a 60 per cent reduction in environmental impact vs cotton notes.

[@KPPMt1n7]

Having worked on the bill acceptors, "BVs" as we called them in the casino, the first thing that hit me was it needed to be cleaned and calibrated. I do not remember but I think those types required special calibration paper. You had to put it in a learning mode with the DIP switches. The paper was longer size than a bill with timing marks on it and also an area that calibrated the LED sensors. And this might have been the type that you also had to insert the bill into for it to learn the patterns from. Most of the newer BVs are simply reprogrammed with a small black box you hook you to a jack inside a press a button. The reprogrammed chip comes from the BV manufacturer. Oh and the cash stacker box looked like a 200 bill size. What saved the casinos' butt from counterfeit bills being accepted into the slot machines was that most were bleached $1 bill then ran through a printer to look like $20s (Rarely larger because a larger bill will be looked at closer) but they would not go to the trouble of buying the magnetic ink to print them with. And that can actually be purchased at office supply stores for companies that print their own checks. Most of our counterfeits came from the pit because the dealers are under pressure to deal as fast as possible they do not take the time to scrutinize the bills as closely as they should. The other source was the gift shop and finally the cage.

[@EEVblog]

Maybe, but it was supplied with the cable from the unit, and that's just mains and currency detect plus pulse output. No feedback line.

[@obiwanjacobi]

What a nice colorful money they've got there down-under! Reminds me of the pre-euro Dutch money.

[@JohnDoe-gm5qr]

I think why it won't accept it is there is no change dispenser. I guess that if the change dispenser or something to give it some kind of signal is missing, it will reject the currency rather than take it and give you nothing. That is because sometimes there is no attendant around to open it up and give you your money back and that can upset people if the machine takes their money.

[@theandnewman]

The notes are 2006 edition (says that on both), of course a validating firmware from 2002 will reject them.

[@jonas.gruska]

Just noticed those exposed screws on banana plugs carrying mains from your AC power source :P Wouldn't wanna accidental stick my finger there.

[@EEVblog]

We continue to get the odd report here too, people try, but it's not a big deal. It's usually pretty trivial for most people to instantly recognise any fakes. They don't last long in the system before they are spotted.

[@salahzayouna]

This system scans the stamp of the note, provided by the sensor, not only reading specific points. Each note value will provide different scan stamp which compared with the stored stamp. The stamp is like a chart for a start and end position. No need to focus the light reflected. When a new note used, they just scan it and save its scan stamp in the firmware with related info to make the machine capable of recognizing the new note.

[@GadgetUK164]

Great vid!

[@pessimistmaximus5731]

252 triggered yanks and counting.

[@AdamAus85]

I previously worked for Wilson Parking and part of that was getting around to pay machines for maintenance. This device here looks a lot like what you'd find in the guts of Skidata pay machines.

[@WhitentonMike]

I found immeasurable respect for Daniel Dennit when he unhinged one of WLC's arguments. He referred to WLC's debate technique as "..cantilevering logic into uncharted territory where it cannot at this time be verified to agree with reality." My mouth literally fell open on that one.

[@angusbradley797]

Good one. Unique one. BTW, with all the plastic boxes and plastic gears and a trace of electronics, it reminded me of an old camera.

[@serbianhero1389]

Probably should have closed the back side while testing it, I guess it's why it keeps refusing the note.

[@reverse_thursday]

When that 'hi' hits just right 👌👌👌👌

[@jaaasgoed]

Ah, the beautiful 50 guilder note, with it's rich yellow/orange glow and it's big bright sunflower. I remember it well.

[@EEVblog]

Oh, completely missed that, will have to check...

[@king65462]

listen to this fuckin ausie bash americans

[@Mostlyharmless1985]

pretty sure he's bashing our money.

[@king65462]

Mostlyharmless1985 we got money you sure obama aint spent it

[@Mostlyharmless1985]

That wasn't even a coherent idea, let alone relevant. What does Obama have to do with our bills not being terribly resistant to counterfeiting?

[@Mostlyharmless1985]

Second, Obama doesn't set the budget or spending, congress does. You need a civics class, mate.

[@madjimms]

Mostlyharmless1985 +1 for you good sir.

[@EEVblog]

We used to have $1 and $2 notes, but also abandoned them a long time ago.

[@edwardbyard6540]

Money Controls! I've written device drivers for these units in the past, for parallel, binary, serial and ccTalk modes. Fun stuff.

[@TheMrKeksLp]

Cool! :O

[@5thDragonDreamCaster]

An interesting feature is that the $5 bill has a few marks on it only visible in the near-infrared spectrum. There are some neat pictures of it.

[@steve1978ger]

aren't these things always a major pain in the ass... how many trains have I missed because these fricking things had a grumpy day and did not accept my perfectly valid money. I'd really enjoy seeing one blown up :)

[@GadgetBoy]

I'd love to see an australian bill acceptor teardown

[@Nathan0A]

that;s normal operation for our bill rejectors! You have to look at the plus side, helps curb the obesity problem as most of these are fitted to vending machines!

[@richfiles5056]

They built that PC board like a badly balanced RPG skill sheet! They spent all their organization skill points in prettying up those SMD resistors, and had nothing left for the rest of the design! XD

[@frac]

Canada has a nice touch for that. Besides raised ink, it also has Braille-like bumps in the corner of each bill. It's not really Braille, just a raised pattern on each bill, but it's pretty neat.

[@mtootm]

As an american. I want plastic money too!

[@newton3010]

14:41 This tab is to detect if the bill pusher plate is at start position. Once the bill is validated it is pushed into the holding box. this detects when the plate is and is not at start position.

[@simcop2387]

Watching it not accept the bill and you being flustered at it makes me as a yank feel better. There are lots of in-service vending machines that do the same thing here in the US.

[@JakeSucky]

This channel is awesome

[@squelchedotter]

I don't know if dave will say this, but the soldering around 25:50 is pure gore

[@BigTechie24]

One major thing about us money is there are magnetic strips in all us bills except the $1. The strips are in different places depending on the denomination.

[@666alikat]

Awesome! Your Cosmic Father will be pleased.

[@buddhaman001]

I know I'm later to the party BUT, I'm thinking two cameras, and because of the way they are offset, it is so you can put a bill in right side up or upside down and it will still read.

[@AlecKristi]

The milky leds are probably 2 color red/green or something like that, the blue leds are probably i.r., I don't see any uv leds on this board, those would have either clear cases or metal cans. uv detectors are usually ccd or very large photodiodes like the can in the middle (except the middle led doesn't look uv), gotta be strong enough to pick up fluorescence, there would also likely be a filter over them. i've seen a detector with a cold cathode uv source before too.

[@sysghost]

Aha. I'm not sure, but here's my guess on how the bill value detection works: The metal strip in the bills has a specific position for each value, measured from the edge. When a bill is fed into the machine, it measures how long the bill have to travel before it detects the embedded metal strip, once the distance it determined, it knows the value. Other than that it just detects ultraviolett and/or infrared reflection from the bill. Not too much and not too little. Simple device.

[@TiagoTiagoT]

Would it have the processing power to scan and analyze strips of several pixels with those optical sensors by scrolling the bill thru or does it really just look for specific points?

[@alexandrumarzenco6998]

It's so funny to spot a blown up chip while dave doesn't notice a thing even when he pokes that specific part with his plastic poking device

[@derekc423]

Saw an article today saying that the new polymer bills can melt in cars and dryers. I have never torn my "paper" bills. But I sure have put them through the drier more than a few times. I'd hate to think the polymer notes might not make it through that. You're right, Australia did win something, "Best New Currency Website".

[@DerekMartell]

yank here. That looks like an older model that we would see on vending machines. These days there are modules that accept them in any orientation. It looks like that unit is defective, you put the money in correctly the first time.

[@williamsquires3070]

Note @ 16:20, there appears to be a solder bridge on the right side of the uP! Also, at about 14 minutes in, look at the chip right there above the two filter caps; at the right angle, the light reflects off what looks like a crack or burn mark.

[@NickStallman]

Btw the Aussie notes are different sizes to assist blind people, where as the US ones are all the same size. Probably why this one doesn't have any size detection where as our Aussie detectors would. Power up some of the LEDs? And perhaps it was rejecting the bills because of some anti-tamper protection which prevents it from working outside of a machine?

[@SayWhatNow92]

It detects the pattern of the yellow dots, that are in clusters on both side of the note. the UK notes have them too, some scanner software will display a warning if they detect this pattern in an image.

[@switchstarboard]

Don't see that anyone pointed out that the bill is the newer style and the date on that unit is 1998. The $5 was completely changed in 2000 to add those security features so it's likely it has no idea what that bill is.

[@richg491]

That bill validator was probably pulled as it did not read the newer 5 dollar note. the uv/magnetic signature was updated. that probably reads the older notes.

[@phoenixrestorations315]

there is also micro printing. on the front of that 5 dollar bill in the boarders at the left and right in the tear drop shaped design that goes all the way up and down it in each bubble or drop the tiny horizontal line going through the middle of each drop that is actually tiny print that says five dollars. it is really cool to look at the bills with a good magnifying glass.

[@MirekHeikkila]

Canadian Bills are the best! And purrty :) .. one cool thing is if you shine a laser through the transparent part it'll display the number on the wall via a diffraction grating!

[@-taz-]

That's a relatively new $5 design. It's probably been 5 years or so, but I haven't even taken a close look at one of those myself. What's really strange is that they've designed a new orange $100 note in 2009 and not a single one has been released yet.

[@AsbjornGrandt]

"In god we trust **loud snort*"* That made me laugh, thanks for a dose of reality :D

[@Eric-ue5mm]

Asbjørn Grandt Hahaha, my mouse went straight to the subscribe button.

[@guilherm502]

I laughed loudly hard

[@HelloKittyFanMan.]

+Asbjørn Grandt The *opposite* of reality, actually. Without that there wouldn't be any point to this inconclusive life of being born, doing a bunch of stuff, and then doing the opposite of being born. There's gotta be some bigger reason we're going through all of this.

[@AsbjornGrandt]

MaxxFordham No, there really don't. It would be nice to be able to blame some other entity for the shit we go through, but in reality all we can blame are other people. Live exists for the sole purpose of living, procreating. Life is a glorious accident, but that doesn't mean it's pointless.

[@HelloKittyFanMan.]

No, not an accident, Asbjørn Grandt. Why would we care how much joy we could get from it if there wasn't any existence for us to take away any of the good from this after it's over and we move onto another phase? That's just it: because *without* something to look forward to this, it would *not* be glorious, and it *would* be pointless. Without that it would not make sense for us to be here living. Why must you guys be so senselessly stubborn about that? It doesn't make sense.

[@synaesthesia2010]

youtube captions are so much fun. 17:15 - 'measure summit the yatch since a star so i will have to'

[@the_eminent_Joshua_E_Hrouda]

Captions show perfectly for me

[@rokinskis11]

when i watch your teardown videos i dont need to watch a review video :D

[@ferlgazi]

I don't work with them directly, but I do work in an industry that utilizes them. They have programmable sensitivities and other settings that would allow any direction and specific levels of it confirming if its counterfeit or not. We live in an area with *ahem* not the brightest of people, so our service tech usually sets our validators loose so people don't get caveman angry with them.

[@ryankelzenberg3453]

As you mentioned depending when the last time that bill acceptor was flashed, it may not have been updated for the "new" $5 bills.

[@Brony22]

when you tried to put the money in, did you have the back on it?

[@aptsys]

The first step to recovery is admitting you have a problem. Congrats!

[@kspooon]

the constant reject is a very common thing. most of our funny money here is rejected and we deal with the same frustration and more due to the fact we want something and provide good funny money and it shits on us 20 times before it takes it. coins are easier.

[@WafflesASAP]

The machine probably only accepts the old $5 bill design. It does look like an older module =P

[@TheXelaNet]

The firmware can be updated....

[@WafflesASAP]

But a firmware update won't compensate if the scanner itself doesn't have the hardware to read the specific type of metal in the new bills' strips. That said, I'm not a currency expert (nor an electrical engineer). I could be a wrong. ::shrug::

[@moleculardescriptor]

I bet the machine did not accept these bills because Dave removed the collection box. I further bet that "funny looking second opt detector" sensed the box's presence.

[@dos541]

Unless it needs confirmation from the vending machine to take the currency incase someone puts in money and decides not to buy anything

[@lsrx101]

That is exactly why. It will not accept the bill until the machine that it is installed in basically says "I'm waiting for money". I don't know exactly how it works, but that's it in a nutshell.

[@EEVblog]

No, they don't do it because it's very very difficult, and is one of the reasons why countries have switched to polymer notes. The US have a big counterfeit problem because their currency is relatively easy to counterfeit.

[@EEVblog]

I wonder if that's a bell shaped curve?

[@squidinkRC]

Yeah, were still waiting for those plastic bills. Not even going to argue that your melt in the wash...

[@monosurge]

Oh.. I was just taking your entire post out of context. Returning the favor ya know ;)

[@jackwhite3820]

What are the brown parts at 20:04 that look like ceramic capacitors? I am confused by the four solder points on them.

[@JohnGuillorykf5qeo]

The $5 is rather old, as they've had the embroidered 5 on the bottom right corner for quite some time now. As far as the rejecting it, that's pretty much how the vending machines and casino games reject it. I find if you have a corner folded up, you have to straighten it out before it will accept it.

[@WhitentonMike]

One of the soda machines when I was back in college had a flaw in the coin accepter. If you flung a coin into it, it would not only kick the coin out the return shoot, it would register full payment and give you a free soda. I love that machine. The crappy bill validators are just payback for all the free sodas I drank back then. :( :) :(

[@ronnies07]

Did you have the cashbox off when trying to feed it a note? Does it have some sort of interlock? Wouldn't want money floating around the inside of the vending machine.