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Photoelectric lamp control with sun-synchronized timer

  • US 4,237,377 A
  • Filed: 05/23/1979
  • Issued: 12/02/1980
  • Est. Priority Date: 05/23/1979
  • Status: Expired due to Term
First Claim
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1. A light-responsive control circuit comprisinga light-responsive switch which distinguishes daytime from nighttime by representing the light intensity of the daytime sky and the relatively low light intensity of the nighttime sky as binary voltage levels,a pulse-generating circuit whose output is a train of pulses having a first fixed frequency when said light-responsive switch signals the occurrence of daytime and whose output is a train of pulses having a second fixed frequency, said second fixed frequency being twice the frequency of said first fixed frequency, when said light-responsive switch signals the occurrence of nighttime,a turn-off time controlling means which is settable by a user to a solar time of night, at which turn-off time every night a load is to be disconnected from an electrical power source, whose output is an electrical representation of said turn-off time,an encoder which has an input the output of said turn-off time controlling means and produces an output, the turn-off time setting, which is a set of electrical states presenting the settings of said turn-off time controlling means as a digital number,a counter that counts the number of pulses emanating from said pulse-generating circuit between the time said light-responsive switch signals the occurrence of dawn and said turn-off time set on said turn-off time controlling means, such that, when said turn-off time set on said turn-off time controlling means occurs, the states of the latter stages of said counter, said latter stages constituting the outputs of said counter, constitute a digital number equal to said turn-off time setting,a counter reset means which enables said counter to count from zero beginning when said light-responsive switch signals the arrival of dawn,a comparator which signals the occurrence of said turn-off time when said outputs of said counter become equal to said turn-off time setting,a latch for controlling said counter by allowing counting by said counter between the occurrence of a dawn signal from said light-responsive switch and the occurrence of a signal from said digital comparator indicating the occurrence of said turn-off time, and for maintaining said counter in a reset state between the occurrence of said turn-off time signalled by said digital comparator and the occurrence of a dawn signal from said light-responsive switch,a first gate circuit which monitors the state of said latch and the state of said light-responsive switch, so that, when said light-responsive switch indicates the occurrence of darkness, and at the same time said latch indicates the counter is counting, then the output of said first gate circuit constitutes a signal commanding that said load be connected to said electrical power source, anda power switching means which, in response to said signal from said first gate circuit, connects said electrical power source to said load.

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