Comparitor likes this dime but not that one??

[BCD11]

Recently I replaced the capacitor in a CMI CC-16E comparitor that would not reliably sort dimes. After the replacement, results improved slightly when using a 2007 dime as the sample coin. However, when I used a high % silver (1956) the comparitor performed flawlessly. No matter what post-'64 dime I used the comparitor was inconsistent but the silvers worked perfectly.

I'm slowly getting up to speed on the workings of the CMI comparitor but this quirk has me baffled. Anyone have any ideas as to why the 16E likes silver as the sample but not a clad?

 

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[madwest]

The principle of operation of your comparator is . . .

If . . . there is a winner. If they differ, . . .

The signals that come in on . . . is simply a transfer function of . . . That transfer function is determined by . . .

The . . . coil . . . via . . . Those induced currents then cause . . . The explanation for why one alloy of coin makes a better reference . . . Those metals just aren't useful for magnetics . . .

 

[BCD11]

Thanks madwest! I figured if a forum member would come up with an answer it would be you.

I'm still wading through my Electronics-to-English dictionary, getting the explanation to terms I can understand, but thanks to you I now have a good idea of how a CMI comparitor works.

Changing topics, a while back you were working on arranging the parts & pieces of a comparitor so coin jams would be a thing of the past. A shorter while back you posted videos of a comparitor with a clear plastic front. Your posts got me to thinking about ways to alter a comparitor in hopes of reducing clogs and I came up with something that has worked so far for $600 worth of pennies and $1500 of dimes. I removed the case holding the circuit board and let it hang by its wires ( I know, not the best idea but it works for now). I then added a piece of plexiglass that is 1/2" high and spans the inside width of the comparitor holster. The plexi is located just above the rake and is intended to keep the coins on their vertical trajectory as they exit the coil. Finally, a small paperboard enclosure was attached such that it would direct any coins to the "accept" bin if they are hit by the rake when it returns to the reject position. These alterations prevent coins from getting pinned between the rake and the backside of the circuit board case.

I ran $25 worth of pennies through the comparitor and then hand sorted them looking for "accepts" and "rejects" that ended up in the wrong bin due to the rake hitting the coin. There was not one misdirected coin in the batch. So far (fingers crossed) this has allowed me to run the sorter on 24VDC at a speed of 375 coins/minute WITHOUT jams.

Again, thank you for the explanation why the comparitor works better with one alloy sample than another AND the videos that lead to my altered comparitors.

 

[madwest]

BCD11:

Thanks for discussing your mods to fight the jam issue. I think the ultimate answer is along the lines of what you have set up. I am working on an arrangement in which the rake is just part of the coin slide and cannot result in a "pinned" coin. It sounds like your approach is somewhat similar. Nice.