Design and implementation for a coin identification system

摘要

This paper proposes two methods to implement a coin identification system. The proposed methods have several advantages, such as good identification accuracy, simple hardware configuration, and easy extension. Method 1 uses a single winding high-frequency sinusoidal voltage exciting method. By injecting a fixed-amplitude, fixed-frequency sinusoidal voltage, the exciting current, which is related to the impedance of the winding, can be detected. By measuring the amplitude and phase between the input voltage and current, the coin feature can be identified and then a `true' or `fake' coin can be determined. Method 2 uses a square-wave voltage exciting method. Two windings are used. The primary winding is connected to the square-wave voltage, and the second winding is used to measure the induced voltage. The induced voltage waveform of the secondary winding is varied as a coin passes through. By using Fourier analysis, the proposed system can determine the coin as a `true' or `fake' coin. The performance of these two methods is compared and discussed. Finally, a normalization technique of method 2 is discussed. By using the normalization technique, the accuracy rate of method 2 can reach 90%, which is better than the accuracy rate of method 1.