| Economy is developing and population is increasing in today's world, the currency is growing in circulation. Particularly, the small denomination coins have large usage rates in the currency circulation, with its features of wear and easy use. With the emergence of some automatic equipment such as vending machines, pay phones, automatic ticketing system and public transportation in life, we have more and more opportunities to use coins. However, the emergence of a large number of counterfeit money makes installing coin identification device become indispensable technology tool in these equipments.This paper describes the design of a low-cost, high-accuracy and fast coin identification system. The system uses a high-frequency reflection sensor and a low-frequency transmission sensor to detect coins'material, thickness, diameter and other information. The high-frequency reflection sensor detects material, surface texture of coins, the low-frequency transmission sensor detects coins'thickness, diameter and other dimensions information. By low-frequency sensor conditioning circuits and high-frequency sensor conditioning circuit, the information of coins was converted as power units, and these units were collected and processed by collection system. The system signal acquisition circuit uses FPGA as its core to collect and process the coin features fastly and effectively, relying on high-speed, high-precision features of FPGA. After acquisition and processing, characteristic data of the coin was sent into MCU. Coin identification was completed by comparing characteristic value of the coin and characteristic value of the real coin.This system has the function of online learning, it can learn the characteristic values of those real coins in currency circulation. These characteristic values were stored in EEPROM of MCU as the coin identification standards. As long as a sort of coins were issued by the state bank, this system can identify these new coins through the function of learning. |
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