>>I need to build a controller for a coin operated machine, which has
>>to recognize the different coin values.  Plus, it has to be capable
>>of being set-up for other countries' coins.  Does anybody know if
>>such a detector exists, and how it can be connected to a PIC?

>There are several different brands of coin mechanisms that will do
>what you want.  You pop the coin in and the box checks it thoroughly
>to make sure it's not a slug or counterfit, then closes an appropriate
>contact to tell you what kind of coin it was.  They're not too
>expensive - most video games have two of them inside.

I once opened one such mechanism that come from a one arm bandit slot
machine.   It works on a metal detector principle with two separate,
but similiar search coils.  A fixed coin gets permanently installed
over one of the coils, and the deposited coin then gets compared to
this fixed coin.  But this only lets you recoginise one particular
coin.  I presume the way to recognise several different types of
coins would be to use one such coil, and store a footprint lookup
table for each different coin that needs to be recognised.  That way
you can teach the device which coins to accept.

The mechanical problems to overcome would probably the most difficult
part of your design.

--
Werner Terreblanche   Tel +27 21 7102251   Fax +27 21 721278
wterreb@plessey.co.za (work)  OR  werner@aztec.co.za  (home)
Plessey SA, PO Box 30451, Tokai 7966, Cape Town, South Africa