Comments on: How Does A Vending Machine Detect The Denominaton Of Coins?

By: therealc

therealc — Wed, 21 Oct 2009 04:38:10 +0000

by the weight of the coin

By: Bunts

Bunts — Wed, 21 Oct 2009 04:38:10 +0000

The guy talking about the speed doesn’t know anything. Objects fall at the same rate, regardless of mass. 9.8m/s or 32ft/s

By: Daxi

Daxi — Wed, 21 Oct 2009 04:38:10 +0000

Some work on the diameter/shape, some work on the weight, and some work on both. Although some coins may appear at first glance similar, they are deliberately designed to be different in weight and size precisely to make it easier for automated machines like this to work.

By: Graham I

Graham I — Wed, 21 Oct 2009 04:38:10 +0000

by the weight of the coin

By: char

char — Wed, 21 Oct 2009 04:38:10 +0000

weight and size

By: spiko

spiko — Wed, 21 Oct 2009 04:38:10 +0000

By the weight of the coin.

By: JOHNNIE B

JOHNNIE B — Wed, 21 Oct 2009 04:38:10 +0000

Don’t things falling accelerate at 9.8 m/s^2 (acceleration due to gravity) until they reach there terminal velocity due air fiction. Not fall at 9.8 m/s.
As for the coin issue they probably use different methods due to size, shape and weight as each coin has different values for each.

By: theadven

theadven — Wed, 21 Oct 2009 04:38:10 +0000

weight all coins are a different weight

By: john s

john s — Wed, 21 Oct 2009 04:38:10 +0000

Vending machines employ a series of tests to identify the denomination of coin and to detect forgeries, in older machines there were a series of “analogue” tests. One test is to check for magnetism Sterling and Euro 1,2 & 5 denomination are steel / copper alloy and therefore magnetic.
Theres also “the bounce” of the coin, effectively its a weight test- as the coin goes through the system, it reaches a drop. At the bottom of the drop, theres a rubber mat which the coin bounces off and the hight of the bounce measured.
There were also a series of slots that “filtered” the coins, smaller holes gradually increasing takes out the 1,2,5, 10, 20, 50 etc, in turn.
It’s not infalliable, theres a (Latvian?) coin that is almost identical to the 2 Euro coin in appearance, weight, composition etc. And due to the regionallity of the Euro (French coins are different to Irish, German, Italian etc) can be difficult to spot in a large amount of change.

By: Efnissie

Efnissie — Wed, 21 Oct 2009 04:38:10 +0000

There are many ways and as technology improves so do the technique.
1) the coins mass
2) since all coins are made of metals and all metals have resistance. An ohm-meter checks the coins resistance. If the resistance is within parameters, the coin must be the correct value!
3) in some denominations, different value coins have different sizes. e.g. dime (10 cents) is smaller than a quarter (25 cents)! so “WITHIN” the machine the quarter is not going to fit in the dime slot!
So a simple circuit using logic AND gate: If all three of the above values are TRUE then Coin is of correct value, if 1 value is FALSE the coin is rejected. In other words:
THREE INPUT AND GATE, 1 = TRUE, 0 = FALSE:
* = multiplication
1 * 1 * 1 = 1 Correct Value
0 * 1 * 1 = 0 Rejected
1 * 0 * 1 = 0 Rejected
1 * 1 * 0 = 0 Rejected
Many other techniques can be used!