Coin-operated

A currency detector or currency validator is a device that determines whether banknotes or coins are genuine or counterfeit. These devices are used in many automated machines found in retail kiosks, self checkout machines, gaming machines, transportation parking machines, automatic fare collection machines, and vending machines.

The process involves examining the currency that has been inserted, and by using various tests, determining if the currency is counterfeit. Since the parameters are different for each coin or banknote, these detectors must be programmed for each item that they are to accept.

In operation, if the item is accepted it is retained by the machine and placed in a storage container for later collection. If the item is rejected, the machine returns the item. If a coin is rejected, it usually falls into a container or rolls out of a slot at the bottom where the customer can remove the coin. If a note is rejected, the machine ejects it and the customer must remove it from the slot into which it was inserted.

The basic principle for coin detection is to test the physical properties of the coin against known characteristics of acceptable coins. The detector evaluates the coin based on its weight, size, metal composition and/or magnetism, and then sends an appropriate electrical signal via its output connection. The next step is generally performed by the banknote-to-coins exchanger.

Today, sophisticated electronic coin acceptors are in use in some places that, in addition to validating weight and size, also scan the deposited coin using optics and match the image to a pre-defined list, or test the coin's "metallic signature" based on its alloy composition.

Normal coins harbour microscopic deposits of dirt, oil and grease from human fingers. When a coin acceptor is used long enough, thousands of coins rolling down a ramp will leave enough dirt, oil and grease to be visible. The coin acceptor must be cleaned on a frequent basis to prevent malfunctioning. Coin acceptors are modular, so a dirty acceptor can be replaced with a clean unit, preventing downtime. The old unit is then cleaned and refurbished.

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