EEVblog #525 - Bank Note Acceptor Teardown

[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?
Datasheets:
http://www.silonex.com/datasheets/specs/images/pdf/102136.pdf
http://pdf.datasheetcatalog.com/datasheets/134/157244_DS.pdf
http://www.ti.com/lit/gpn/tlv5629
http://www.mouser.com/ds/2/328/top242-250-9213.pdf
http://www.latticesemi.com/~/media/Documents/DataSheets/ispMACH4ADataSheetvL.ashx?document_id=1344
http://www.freescale.com/files/microcontrollers/doc/data_sheet/MC68HC11F1.pdf
http://pdf.datasheetcatalog.com/datasheet/AdvancedMicroDevices/mXwuvz.pdf

[c4757p]

Hmm... I wonder why it won't accept the bill. They're grumpy sometimes with crusty old money, but there's no trick to it...

...never mind...

[sync]

I guess it must be enabled from the vending machine controller. When the machine is not working the acceptor should not accept notes.

[mikeselectricstuff]

Centre sensor more likely to be shorter wavelength due to larger PD. May be looking for fluorescence on some of the inks. You should fire the LEDs up to see what colour(s) are visible.

As regards the poor mains  segregation - well it is only 110V, not like it's real mains  or anything...
 

[c4757p]

From Dave in the YT comments:

I got a $1 coin in the? US one time (from a machine?), and tried to spend it, I got the WTF face.

If you really want to get the WTF face, try spending a $2 bill... Fifty cent coins are good too. At least the $1 coins were pushed somewhat recently

[orion242]

Another great video.

That's a newer $5 bill that was introduced in ~06.

I second a followup video to power it up and figure out what spots in the bill they are looking at and with what wave lengths they are using.  Maybe dump the rom and poke at the firmware.

[gsstyle]

Oh, My i haven't though about a 2 dollar bill in a long time , have collected some .. and i think i gave them to my mom .. so i wouldn't spend them , but were talking mid 90's

[EEVblog]

Hmm... I wonder why it won't accept the bill. They're grumpy sometimes with crusty old money, but there's no trick to it...

Could be the firmware (becaue the note is 2006 I'm told), but could also just need a good clean.

[EEVblog]

If you really want to get the WTF face, try spending a $2 bill... Fifty cent coins are good too. At least the $1 coins were pushed somewhat recently

I've got a $200 Australian coin, try spending that!

[gxti]

Clearly, safety isolation was not required for this application. The layout is still baffling, though.

[NickS]

Hmm to beat this could you use some clear plastic (overhead projector) and just print a pattern in black to reproduce the signal that the reader is expecting?
Bonus points if you dump the ROM and use it to create the patterned image.

Sure it would only work on a single type of machine, but if it is common enough and you can get the plastic cheap enough it could be a fun exercise - pity about the illegal bit.

[DavidDLC]

No offense Dave, but can you clean your throat before you make a video ?

On the lates videos is kind of annoying that hoarseness on your voice, it almost stop me to go all the way to the end of the video.

David.

[EEVblog]

No offense Dave, but can you clean your throat before you make a video ?

The video is 40 minutes long, with over an hour of recorded material, recorded over several hours with 60 or so clips. I can't just "clear my throat before I make the video".
I do clear my throat if I hear it's getting a bit rough. Sometimes I stop the camera and do that and will reshoot that bit. But I'm not actively listening for that stuff while shooting. it's like trying to detect if you are speaking too loud, or too fast, or have repeated something, or have said something wrong. It's very difficult, you simply don't notice your own voice and what it's doing.
My voice sucks in so many way, and occasional hoarseness is simply part of that I'm afraid, it will happen.
I also generally cannot go back and re-shoot segments if I detect my voice is bit rough at the video editing stage.
So sorry, I do my best, but you get what you get.

[David_AVD]

Coin and not acceptors usually have an enable line from the host machine.  This is so they don't accept money before the machine is ready or if it's "out of stock".  That can be another reason for them not accepting the cash.

EDIT: Didn't see the reply from "sync" about the enable line.   

[ampdoctor]

I guess it must be enabled from the vending machine controller. When the machine is not working the acceptor should not accept notes.

That's exactly what's going on.  this makes sure your money doesn't get swallowed up by a machine that's empty or malfunctioning in some way or another. Otherwise these things are dead reliable electrically.  Their biggest issues as dave noted is that the mechanicals and optics get absolutely filthy. After you push maybe a thousand bills through it you need to just open the thing up clean off the feed belts and sensors and you're "money"

as an aside, these things aren't really about detecting counterfeits, there's really very little of that going on, but rather to make sure the bill is the right denomination.

[DavidDLC]

No offense Dave, but can you clean your throat before you make a video ?

The video is 40 minutes long, with over an hour of recorded material, recorded over several hours with 60 or so clips. I can't just "clear my throat before I make the video".
I do clear my throat if I hear it's getting a bit rough. Sometimes I stop the camera and do that and will reshoot that bit. But I'm not actively listening for that stuff while shooting. it's like trying to detect if you are speaking too loud, or too fast, or have repeated something, or have said something wrong. It's very difficult, you simply don't notice your own voice and what it's doing.
My voice sucks in so many way, and occasional hoarseness is simply part of that I'm afraid, it will happen.
I also generally cannot go back and re-shoot segments if I detect my voice is bit rough at the video editing stage.
So sorry, I do my best, but you get what you get.

Ok I really appreciate your answer. No problem at all.

[Orpheus]

Not having the bill chamber in place may affect it as well

[David_AVD]

Not having the bill chamber in place may affect it as well

Good point.  Otherwise the money would spill into the machine.

[lilshawn]

those milky white LED's are actually BI color LED's...I can see the 3 leads through the side.

I work as a service tech for arcade and vending machines. we don't use coin controls model of bill acceptor, but we do use their coin acceptors though. Money Controls is a popular company in North America, as is ICT (International Currency Technologies - the brand of bill acceptor we use has a far superior sensor system). Money controls has the better coin acceptor and ICT has a better note acceptor. I'm not real fond of Money Controls, and I'll tell you why...

Money Controls is a real bugger about their firmware. They make you buy a ridiculously expensive TTL to RS232 converter box (that retails for about $1500US) that you must use to update the firmware through the diagnostic port.

Then, to obtain the firmware, you must use their program to download the firmware data as a .zip file (not a big deal) but then they lock the zip files with a password that you have to know it in order to unzip it to obtain the raw BIN file.

then... (yeah, then) they make it so you have to pay a yearly subscription licence to run the program that updates firmware. A different program is used for each model of acceptor and you must buy a licence for each program. (IE if you have 4 different type of acceptors you need 4 different programs and 4 different licences)

ICT does not make you pay for updates. you buy a handheld programming device and then have ICT send you the firmware and you download it to the device and use the handheld device to dump the firmware to the acceptor. a much friendlier experience overall.

[EEVblog]

those milky white LED's are actually BI color LED's...I can see the 3 leads through the side.

Doh, yes, you are right, I should have looked at the pins on the bottom.

[Razor512]

The $1 bills have almost no security at all, though it is not likely that someone will make a fake $1 since they are likely to be more expensive to counterfeit.

The bill with the most security is the $20 bill as it is the most common one to be faked. (most businesses will not accept $100 bills)

The security on a $1 bill is just the paper used (reacts with those money testing pins)

then the images on the  money are printed with a special patter that identifies the money type to the machine (it is also why some scanners will detect if you are trying to scan in money. (even if it is just a partial scan.

(the security on the US paper money are similar to the digimarc watermarking method where it creates an extremely subtle grain pattern over the entire image (for a photo taken pretty much all cameras will have more noise native to the image than the digimarc so it is invisible in most cases.

(not sure how  good the security on a $100 bill  is, but for the $20 bill, it has the largest number of indicators that are easily visible since for most stores, ti is the most common bill used and workers need to be able to verify them quickly.

PS the bills above $1 also insert fibers  (though they are randomized) that react to UV light. due to the way they are placed, they must be added to the paper in the earliest stages when the paper it's self is being made.

I will try to take some pics of the security used on some different bills

[c4757p]

The security on a $1 bill is just the paper used (reacts with those money testing pins)

IIRC the Treasury has itself stated that these pens are unreliable.

My idea of $1 bill security is "it's real if it doesn't say 'Monopoly'", since as you said, nobody would be able to economically counterfeit them.

[EEVblog]

those milky white LED's are actually BI color LED's...I can see the 3 leads through the side.

Doh, yes, you are right, I should have looked at the pins on the bottom.

I can confirm the 4 LED's in the middle of the note are dual colour red and IR. Two outside ones are UV.

[EEVblog]

The bill with the most security is the $20 bill as it is the most common one to be faked. (most businesses will not accept $100 bills)

I remember getting many strange looks of suspicion when using $50 notes in the US, and a couple of refusals. And when questioned it wasn't because of a lack of change available. I've had tellers even check my $20 notes too.
That never happens here (unless they don't have the change). $50 notes are common as mud, and no one bats an eyelid at accepting a $100 note. Although ATM's don't give out $100 notes, so they aren't nearly as common.

[Alexei.Polkhanov]

I just realized that I have not used cash money at all for several months, not even once.
Month ago first time I got to the electronics supply store store and there was a sign "No cash please. Thank you for understanding". I guess they don't want to go to bank after hours