Timed photocell switch circuit
First Claim
Patent Images
1. A timed photosensitive power switching circuit comprising:
- a photosensor biasing network, including a photosensor and a resistive biasing network, the photosensor biasing network generating an output signal indicative of ambient lighting conditions;
a light-to-dark pulse generator connected to the output signal of the photosensor biasing network, the light-to-dark pulse generator generating a trigger pulse signal when the output signal of the photosensor biasing network reaches a threshold voltage level;
a timer circuit including at least one output clock signal;
a power switch connected to the at least one output clock signal of the timer circuit; and
a set-reset latch, including a set input connected to the trigger pulse signal of the light-to-dark pulse generator, and having a Q output and a Q-bar output, the Q output being connected to the power switch and the Q-bar output being connected to the timer circuit.
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Abstract
A timed photocell switching circuit is disclosed which senses a light-to-dark transition and applies power to a lamp load for a preset period of time. After the preset period has expired the timed photocell circuit turns the lamp load off for the remainder of the night until a dark-to-light transition resets the circuit after which it can be triggered for another timing cycle. Once the light-to-dark transition triggers the timing cycle the ambient light level cannot disrupt the circuit. In addition, the circuit can be reset regardless of its timing position by momentarily cycling power to the circuit.
70 Citations
20 Claims
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1. A timed photosensitive power switching circuit comprising:
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a photosensor biasing network, including a photosensor and a resistive biasing network, the photosensor biasing network generating an output signal indicative of ambient lighting conditions; a light-to-dark pulse generator connected to the output signal of the photosensor biasing network, the light-to-dark pulse generator generating a trigger pulse signal when the output signal of the photosensor biasing network reaches a threshold voltage level; a timer circuit including at least one output clock signal; a power switch connected to the at least one output clock signal of the timer circuit; and a set-reset latch, including a set input connected to the trigger pulse signal of the light-to-dark pulse generator, and having a Q output and a Q-bar output, the Q output being connected to the power switch and the Q-bar output being connected to the timer circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A timed photocell switch circuit that senses a light-to-dark transition and applies power to a lamp load for a preset period of time, the circuit comprising:
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a photosensor biasing network for sensing the ambient lighting condition; a light-to-dark pulse generator connected to the photosensor biasing network for generating a pulse indicative of a light-to-dark transition; a latch connected to the pulse generator, wherein the latch is triggered by the pulse generator to create a trigger signal; a timer connected to the trigger signal, wherein the timer is triggered to count for a preset period of time in response to the trigger signal; and a switch connected to the timer and the trigger signal, wherein the switch applies power to a load in response to the trigger signal, and wherein the switch is opened at the end of the preset period of time by the timer; wherein the trigger signal includes a Q output and a Q-bar output of the latch, said Q output connected to the switch and the Q-bar output connected to the timer. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification