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AUTOMATIC ILLUMINATION CONTROL SYSTEM RESPONSIVE TO TOTAL ILLUMINATION

  • US 3,609,451 A
  • Filed: 02/16/1968
  • Issued: 09/28/1971
  • Est. Priority Date: 02/16/1968
  • Status: Expired due to Term
First Claim
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1. An automatic illumination control system for maintaining substantially constant the total illumination in an area wherein the illumination is derived from controlled and uncontrolled sources comprising a source of alternating power connected to said controlled source by a common terminal and a tap variable in position across said source for selecting a voltage corresponding to a predetermined total illumination level, a rectifier connected to said tap and common terminal to have a unidirectional voltage on its output leads directly related to the voltage between said variable tap and common terminal, a resistor having an adjustable tap connected across the output leads of said rectifier, a photocell positioned in the area to sense the total illumination therein, said adjustable tap being at the junction of two legs of a bridge circuit, one of said legs including said photocell, said bridge circuit further having intermediate junctions respectively connected between the positive and negative terminals of a unidirectional voltage source, and an opposite junction, the photocell sensing signal between said junction and said opposite junction being in opposition to the voltage at one of said rectifier output leads, said signal being the algebraic sum of the sensing signal and the adjusted voltage from said rectifier means, and means responsive to said signal for controlling the position of said variable tap, said means being connected between said junction and said one of said rectifier output leads.

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