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Registered Member #1405
Joined: Wed Mar 19 2008, 10:57AM
Location:
Posts: 5
I have surfed the net for information but I have not found even a basic idea of how this works. I think they weight, size and measure magnetically the coins, but I have no idea how and the lack of information is bugging me.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Its a combination. Size, weight, magnetically. Basically size is compared, weight compared, and then a magnet is used to pull any coins which are ferrous in nature. Very simple, but effective. There may be other sensors depending on the complexity, but for the most part, its a very simple mechanical discriminating device.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
Size is cheched by rolling the coin over a hole that it shouldn't fit through (if it drops through, it's too small) and then through a hole that's just bigger than it (an oversized coin won't fit). Weight is checked by roling it down a spring loaded slope. If it's too heavy or too light the spring doesnt flex to the right degree so the coin doesn't follow the right path. Sending the coin past a magnet will check if it's magnetic or not and (roughly) how magnetic it is.
Registered Member #1405
Joined: Wed Mar 19 2008, 10:57AM
Location:
Posts: 5
Wow, that's smart. And I guess that for electronical devices they have some kind of transductor so the machine gets a credit when the coin reaches the end, doesn't it?
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
Tim Hunkin has some information here:
Often there is no need for a complicated sensor for amateurs like us, unless the machine gives out something valuable that can be turned into money in a fast and simple operation there will not be many cheaters.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I made a coin slot mechanism for a college project. As the coin rolled down a chute, we used two magnetic sensors to measure the thickness and composition of it, a lamp and CCD line camera to measure the diameter, and a lookup table programmed into an EEPROM to figure out what kind of coin it was based on those three measurements.
It worked pretty well, and could recognise all of the UK coins, while rejecting foreign coins and washers. Of course it helped that we had a friend whose job was servicing coin-op machines, and he gave us some dead mechanisms to reverse engineer...
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How does a coin slot work?
