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Resonant coil coin detection apparatus

  • US 5,273,151 A
  • Filed: 03/23/1992
  • Issued: 12/28/1993
  • Est. Priority Date: 03/23/1992
  • Status: Expired due to Term
First Claim
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1. A coin detection apparatus, comprising:

  • a detector coil arranged so that a coin deposited into the apparatus passes through the detector coil to thereby increase losses in the coil due to induced eddy currents in the coin when the coil is energized;

    a resonant circuit incorporating the detector coil which outputs a damped, time-limited cyclic signal in response to an impulse input;

    a drive circuit for generating an impulse input to the resonant circuit to thereby produce a cyclic output signal from the resonant circuit, the damping of the cyclic output signal being increased when a coil is present within the detector coil to thereby indicate the coin'"'"'s presence;

    means for counting the cycles of the resonant circuit output in response to the impulse input, the number of cycles counted being indicative of whether or not a coin is present within the detector coil, said counting means counting the resonant circuit output cycles for a predetermined length of time after application of the impulse input signal, the counting means counting only those output cycles exceeding an amplitude threshold;

    said amplitude threshold varying depending on changes in environmental conditions including temperature and aging; and

    ,means for varying the number of cycles counted to indicate the presence of a coin to compensate for such changes in the environmental conditions.

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