Infrared detection switching circuit
First Claim
1. A passive infrared detection and conversion circuit, comprising:
- a. a pyrosensorb. a current amplifier coupled with said pyrosensor;
c. a capacitor coupled with said amplifier;
d. a signal processor circuit coupled with said capacitor and being operable to charge said capacitor to a first voltage level and to measure a capacitor discharge time, said capacitor discharge time being the time required for said capacitor to discharge from said first voltage level to a second voltage level, and being further operable to generate an electrical control signal responsive to a variation in said capacitor discharge time which corresponds to a significant motion event.
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Accused Products
Abstract
A passive infrared detection and conversion circuit includes a pyrosensor, a current amplifier, a capacitor, and a signal processor circuit. The signal processor is operable to charge the capacitor to a first voltage level and to measure a capacitor discharge time, the time required for the capacitor to discharge from the first voltage level to a second voltage level. The signal processor is further operable to generate an electrical control signal responsive to a variation in the capacitor discharge time which corresponds to a significant motion event. When the pyrosensor is exposed to infrared motion, it generates a transient current, and the capacitor discharge time corresponds to the transient current. The signal processor circuit includes logic operable to compare the capacitor discharge time with a long-term average capacitor discharge time. The signal processor circuit generates the electrical control signal only when the capacitor discharge time deviates from the long-term average capacitor discharge time by exceeding a predetermined threshold margin and/or satisfying other timing and/or pulse sequence patterns. The logic of the signal processor circuit may be further operable to calculate and update the long-term average capacitor discharge time based on the capacitor discharge time such that the logic filters out unwanted background signals and component tolerance variations, thereby creating a dynamic threshold system for detecting significant motion.
19 Citations
13 Claims
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1. A passive infrared detection and conversion circuit, comprising:
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a. a pyrosensor b. a current amplifier coupled with said pyrosensor; c. a capacitor coupled with said amplifier; d. a signal processor circuit coupled with said capacitor and being operable to charge said capacitor to a first voltage level and to measure a capacitor discharge time, said capacitor discharge time being the time required for said capacitor to discharge from said first voltage level to a second voltage level, and being further operable to generate an electrical control signal responsive to a variation in said capacitor discharge time which corresponds to a significant motion event. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for selectively generating a control signal corresponding to motion of an infrared emitting body, comprising the steps of:
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a. charging a capacitor to a first voltage level; b. discharging said capacitor; c. measuring a capacitor discharge time, said capacitor discharge time being the time required for said capacitor to discharge from said first voltage level to a second voltage level; d. sensing a significant motion event by a pyrosensor and generating a transient current responsive thereto; e. transmitting said transient current through a current amplifier; f. delivering said amplified current to said capacitor causing a variation in said capacitor discharge time; and
,g. generating an electrical control signal responsive to said variation in said capacitor discharge time. - View Dependent Claims (8, 9, 10, 11)
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12. A method for selectively generating a control signal, comprising the steps of:
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a. charging a capacitor to a known first voltage level and allowing said capacitor to discharge to a second known voltage level at a known discharge rate; b. modifying the known discharge rate of said capacitor in proportion to a current output from an infrared motion detector; c. measuring said modified discharge rate of said capacitor; and d. generating a control signal corresponding to said modified discharge rate of said capacitor. - View Dependent Claims (13)
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Specification