Rain responsive windshield wiper control

  • US 5,059,877 A
  • Filed: 08/20/1990
  • Issued: 10/22/1991
  • Est. Priority Date: 12/22/1989
  • Status: Expired due to Term
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First Claim
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1. In a vehicle of the type incorporating a windshield and at least one motor for operating a device on said vehicle, a control circuit for said motor for automatically activating same upon detection of moisture droplets on the exterior surface of said windshield, comprising:

  • (a) a housing secured to the inside surface of said windshield, said housing having means for mounting an array of radiant energy sources and an array of radiant energy sensors such that radiant energy emitted by said sources are directed to the plane of the exterior surface of said windshield and normally are directed back to said array of sensors when no moisture droplets are present on the portion of said windshield occupied by said housing;

    (b) driver means for periodically energizing said radiant energy sources with pulses of a predetermined duty cycle, the interval when said radiant energy sources are "on" defining a rain sense interval and the interval when said radiant energy sources are "off" defining an ambient light sense interval;

    (c) first means for sampling and holding the output of said radiant energy sensors during said rain-sense interval;

    (d) second means for sampling and holding the output of said radiant energy sensors during said ambient light sense interval, the sampling by said first and second means occurring successively within a time interval which is significantly less than the time required for changes in ambient light impinging on said windshield;

    (e) means for linearly rejecting signal components in said sensor output due to ambient light disturbances in successive samples taken by said first and second means to leave only a signal component due to sensing of moisture droplets on said windshield; and

    (f) activating means responsive to said signal component due to sensing of moisture droplets for activating said motor.

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