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Frequency detector

  • US 4,800,508 A
  • Filed: 06/30/1986
  • Issued: 01/24/1989
  • Est. Priority Date: 06/30/1986
  • Status: Expired due to Term
First Claim
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1. Apparatus for controlling the speed of a variable speed motor comprising:

  • tachometer means for converting a rotational output from said motor into a sequences of pulses having a pulse repetition frequency related to the motor speed;

    set means for setting a base time period;

    timing means for timing an extended time period which includes said base time period, said timing means initiating said extended and base time periods upon receipt of an initial pulse from said tachometer means;

    said timing means for stopping said extended timing period upon the occurrence of the first pulse subsequent to the expiration of said base time period;

    counting means for counting the occurrence of tachometer pulses between said initial pulse and said first pulse subsequent to the expiration of said base time period;

    calculating means for determining a repetitive pulse frequency based upon the count of said counting means and the extended time period overwhich the count is determined; and

    motor control means coupled to said calculating means to adjust the speed of said motor by comparing a desired motor speed with a sensed motor speed as indicated by said calculated pulse frequency.

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