Search for coin rejecter or coin acceptor.  Asahi-Seiko in Japan and
National Rejecters in Germany are among the major manufacturers.  These
days the coins' profiles are "taught" or loaded into the coin mechanism
electronics rather than using a reference coin.  There are very cheap
mechanisms from China that use a reference coin, but they only accept
based on physical comparisons.

Regards/Roger, in Bangkok

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Bob Axtell
Sent: Tuesday, 29 July, 2003 1:25 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [EE]: Info on Coin-Comparators is needed.


The ones I am familiar with work primarily on physical effects. Its like
comparing the effect of a metallic object in an resonant
(oscillator) circuit. One coin is placed in a reference coil, and its
characteristics are learned (how much this coin changes the frequency
etc). The one to being tested falls through another coil; if its fall
causes effects identical (within limits) to the reference, the coin is
accepted. Most of the work is spent slowing the fall of the coin so the
effect can be carefully examined.

Having designed metal detectors in my youth (er.. day before yesterday)
I have always been fascinated by how they work so well.

US coins (like most coins) no longer have ANY precious metal, and in
order to obtain an effect similar to real coins, are layered with an
inner core of copper to more closely match the solid, precious-metal
coins they mimic.

Try looking up http://www.windtrax.com/featured_products/

--Bob


At 08:40 AM 7/29/2003 +0400, you wrote:
>Guys,
>has anybody good links to practical aspects of the coin-comparators
>design (schematic, theory etc.)? I googled, but didn't find anything.
>
>Thanks in advance.
>Mike.
>
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