Study On Coin Testing Technology For An Automatic Coin-wrapping Machine

Since the RMB coins circulate with huge quantity in bank, bus companies,and other financial institutions, the circulation of false coins will greatly disturbthe normal financial order, and will result in a huge loss, study on identificationof false coins become urgent. In the departments above, coins need to be packedfor convenience of counting and storage, therefore it is necessary to detect andreject false coins before wrapping. However the detecting of RMB coin isdifficult. Try solve this problem, a method of identifying false coins viaprinciple of eddy current has been presented based on the property of coinmaterials firstly; then another method via image recognition technology todetect coin has also been given; finally the combined method has also beenstudied.The testing system design and the control system have been developed todetect coins based on eddy current method. The testing system includes theLRC measurement circuit, the rectifier circuit, and the RC low pass filter circuit;while the control system consists of a single-chip microcomputer and therelevant circuits. When a coin arrives at the testing area, the output voltage onboth ends of inductance varies with the property of the coin materials, and thisvoltage could be captured by the single-chip microcomputer via the transferringcircuit. The microcomputer can judge the coin to be true or false by contrastingthe measured signal with that of standard value, which is stored in computer. Ifit is false, the microcomputer sends an order to drive the electromagnet andreject the false coin.The image recognition method has also been studied, and a imageprocessing system has been configurated, which include the hardware systemand the software system. An image of a coin can be captured with a CCD camera, and this image is transferred into an image processing system, which isdeveloped with MATLAB software. The image features of a coin can beextracted and compared with that of standard one, and then such judgment as“true or not” will be given.The experimental result shows that the eddy current technology can beeffectively applied to detecting false coin. Because this method is directlyconnected with the properties of coin material, it is the fundamental method fortesting coin，while the image identification method provides the supplementarymeans.