| 摘要 |
<p>In a coin validation system a coin 1 passes between conductive plates 7, 9 which form a capacitor, which provides part of the frequency controlling capacitance of an LC tuned oscillator circuit 23. The presence of a coin 1 between the conductive plates 7, 9 alters the capacitance, and consequently the output frequency of the circuit 23. The oscillator output is supplied via a frequency divider 27 counter 31 and shift register 33 to a microprocessor 35 which subtracts the count value from a pre-stored reference value, and supplies the difference to a look-up table stored in a memory 37. The output of the look-up table 47 determines whether a coin is valid, and if so, what its denomination is. Preferably, while no coin is present the microprocessor 39 monitors the count values obtained from the counter 31, and updates the stored reference value so that it tracks drift in the frequency of the oscillator 23. The validator may also include optical sensors determining coin diameter. <IMAGE></p> |
