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'[OT]: Dollar bill acceptor'
2000\08\10@075427 by Sujay Sirur (K3/EFS3)

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Hello Howard,

I have always wondered how these bill-acceptor machines are able to
distinguish between the bills of different values. Do you also make the
dollar-bill acceptor? Would you happen to know which sensor(s) is used and
how the machine distinguishes between the bills so accurately? I would
assume that there is some form of scanner which does an image-comparison,
but am wondering how it is able to take care of the image-noise (dirty,
folded bills) and at such high speeds (DSP?)?

PICers,
Normally I would have sent this mail only to Howard, but possibly the
answers would be interesting to others on the list too. I apologise to the
rest.

thank you
with best regards

Sujay Sirur

-----Ursprüngliche Nachricht-----
Von: Howard McGinnis [spam_OUThmcginniTakeThisOuTspamDIGITAL.NET]
Gesendet: Dienstag, 8. August 2000 17:37
Betreff: [PIC]:[OT]: Thin Film Heaters


I hope I got these prefixes right on the subject line.

Our 16F873 based controller (there's the PIC tie in) is attached to a
dollar bill acceptor. The dollar bill acceptor has a tendency to freeze up
(exposed somewhat to the elements) during the cold northern winter. Our
customer in the past has used a 40 watt light bulb to keep the interior
toasty to prevent icing and I am trying to locate a source of thin film
heaters that operate in the 24 VDC range.

Any sources?

Thanks,
Howard
Howard McGinnis
.....hmcginniKILLspamspam@spam@digital.net
Electronic Visions, Inc.
1650 Barrett Drive
Rockledge FL 32955
(321) 632-7530
http://ddi.digital.net/~hmcginni
mcginnisspamKILLspame-visions.com

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2000\08\10@105557 by Stephen B Webb

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> I have always wondered how these bill-acceptor machines are able to
> distinguish between the bills of different values. Do you also make the

Distinguishing between bills of different values is probably done in an
analagous fashion to how you or I differentiate bills.  The "real"
question is the machine distinguishes bills from high quality counterfeit
bills.

So, here's what I know:

The ink used to print US currency contains some sort of ferrite particles
in it.  The sensors in the bill changer don't look at the visible
spectrum, but instead at some magnetic spectral response.

> assume that there is some form of scanner which does an image-comparison,
> but am wondering how it is able to take care of the image-noise (dirty,
> folded bills) and at such high speeds (DSP?)?

Noise would be a problem, but I imagine a little bit of pre-processing of
the image can help thigs out quite a bit.  (contrast stretch + gaussian
smooth..)  Then do a convolution with certain features that you know you
are looking for (ie the 1 in the upper right corner, or whatever) and then
accept the bill if the response is high enough overall.  Else try  the
image features of the $5 bill, and eventually reject the bill alltogether.

As far as the high speed part, I imagine all of the image processing stuff
is implemented in hardware, making it fast enough.

-Steve

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2000\08\10@115844 by rottosen

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I don't know how the bill acceptors work. I do know that the Mars models
have a ROM that contains the information to recognize the bills. Each
time the US Treasury comes out with one of the new bills, the ROM must
be changed to know about them. It would be interesting to know how big
the ROM is to hold the data needed to do this. For instance, will they
hold enough data to recognize all of the old bills as well as all of the
new bills?

-- Rich


"Sujay Sirur (K3/EFS3)" wrote:
{Quote hidden}

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2000\08\10@125635 by Bob Ammerman

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The speed isn't really all the high, when compared to real-time image
processing of video signals. You will note that most changers appear to be
doing some scanning and deciding during the entire second or two that it
takes to 'swallow' the bill. You can tell this because they will often very
quickly kick out a bill they don't like.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\08\10@131125 by Dan Michaels

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Richard Ottosen wrote:
>I don't know how the bill acceptors work. I do know that the Mars models
>have a ROM that contains the information to recognize the bills. Each
>time the US Treasury comes out with one of the new bills, the ROM must
>be changed to know about them. It would be interesting to know how big
>the ROM is to hold the data needed to do this. For instance, will they
>hold enough data to recognize all of the old bills as well as all of the
>new bills?
>

This is probably pretty closely held information, as it gets
into the whole realm of counterfeiting. If the scheme is too
simplistic, then a xerox copy would pass. Wouldn't want that,
would we? [but maybe one of the echelon moles activated on words
like "US Treasury" and "recognize ... bills" might perchance come
forth and tell us - guys??????].

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2000\08\10@132127 by Howard McGinnis

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Surjay,

We do not make the dollar bill acceptor, only the controller that
interfaces to it.

What I have gathered from the documentation is that the validator has 3
optical sensors, right, center, and left and a magnetic sensor of some sort
to allow it to accept coupons.

Howard
Howard McGinnis
@spam@hmcginniKILLspamspamdigital.net
Electronic Visions, Inc.
1650 Barrett Drive
Rockledge FL 32955
(321) 632-7530
http://ddi.digital.net/~hmcginni
KILLspammcginnisKILLspamspame-visions.com

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2000\08\10@132130 by Mike Werner

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Dan Michaels wrote:
> Richard Ottosen wrote:
[bill acceptors recognition scheme]
>
> This is probably pretty closely held information, as it gets
> into the whole realm of counterfeiting. If the scheme is too
> simplistic, then a xerox copy would pass. Wouldn't want that,

Old change machines *did* accept Xerox copies.  There were quite a few of
'em here in town back about 15 years ago or so.  The arcade that used to be
downtown was one of the places that had 'em.  And no, I'm *not* going to
admit to how I know that it worked. ::grin::

> would we? [but maybe one of the echelon moles activated on words
> like "US Treasury" and "recognize ... bills" might perchance come
> forth and tell us - guys??????].

Either that or that new thing ... Carnivore I think it's called?
--
Mike Werner  KA8YSD   | He that is slow to believe anything and
                     | everything is of great understanding,
'91 GS500E            | for belief in one false principle is the
Morgantown WV         | beginning of all unwisdom.

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2000\08\10@180257 by Plunkett, Dennis

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It starts with mirco printing that is very hard for most copiers to
reproduce, then there is the plastic strip in the note itself, then there is
the properties of the ink


Dennis



> {Original Message removed}

2000\08\11@213033 by John Mullan

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I have some experience servicing bill validator equipment.....

Two major brands of BV equipment are MARS and JCM.  I have worked on the JCM
brands.

There are an array of IR emitter/detector pairs.  There is a microcontroller
and it is programmed with the information regarding each bill it is designed
to accept.  In my case, Canadian bills (even worse with the colors).

The program basically samples bills at various points along the length as it
is drawn in.  If you notice, after the bill is drawn in, it is held (called
escrow) while it compares the sampled data against a table.  The sampling is
analog and measures the IR light absorption of the colors and thickness, etc
of the bill.  The sensor pairs are typically arranged in groups of two.  One
pair with receiver on the top and the other with the receiver on the bottom.
Generally there are two pairs in the middle, two pairs on the right side,
two pairs on the left side. There are a couple of single pairs that sense
the bill entering the head and one pair for exit. They have "anti-fish"
rakes to stop people from pulling them back out.  There are timing
mechanisims and photo-interrupters in case it jams.

After acceptance the "transport" and "stacker" units take and store the
bill.  If the bill jams during storage procedures, the bill validator unit
will shut down and refuse further bills.

Some units also have a magnetic sensor for embedded strips (US bills).

The unit is fairly simple in it's interface.  There is power (of course),
and enable input, an accept/reject input and a pulse count output.

When power and enable on on, the head will accept bills.  If a valid bill is
accepted, a series of pulsed (1 for each $1) is sent out.  If the control
equipment wants the acceptor to accept the bill (via the accept/reject
signals) the bill is stored.  Otherwise it is rejected (another reason for
holding the bill in escrow).

In the case of change machines, the control equipment is typically uC
controller and will decide how much change to return if a valid bill is
accepted.

These companies are constantly updating their software to keep up with the
talents of counterfeiters.  YES, they have been known to accept very good
counterfeits, but they have to VERY VERY good.  The RCMP get involved (in
Canada anyway) when they are this good.

I have encountered situations where good bills get rejected.  Our $5 bill
was printed with a slightly different shade of blue in a serial number
series beginning with BJ and it drove us nuts until we noticed it was only
this series.

These units are typically calibrated using special colored papers.

I hope this helps you understand these gizmos.  Are you planning to make
one??

Whole units can be had for about $1200CDN, ready for mounting.  But you
would need some schematics to help in interfacing.

John Mullan

{Original Message removed}

2000\08\12@065307 by Howard McGinnis

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At 09:21 PM 8/11/00 -0400, you wrote:

>There are an array of IR emitter/detector pairs.  There is a microcontroller
>and it is programmed with the information regarding each bill it is designed
>to accept.  In my case, Canadian bills (even worse with the colors).
>

John's description appears to be very accurate with one little exception in
the magnetic reader. This, at least in the CoinCo unit we are interfacing
to, is used to read coupons. These are printed by the manufacturers using
magnetic ink.

We did some testing and found that our unit will not accept the new US
dollars. We did this test when we couldn't find a common strip for any
optic path (left, right or center) common to the old and new $5 bills.

For the coupons, CoinCo says that the units must be programmed to recognize
the "signature" of the coupon and I think that this is also true with the
bills.

Howard
Howard McGinnis
RemoveMEhmcginniTakeThisOuTspamdigital.net
Electronic Visions, Inc.
1650 Barrett Drive
Rockledge FL 32955
(321) 632-7530
http://ddi.digital.net/~hmcginni
spamBeGonemcginnisspamBeGonespame-visions.com

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