Electric lamp and discharge devices: systems – With radiant energy sensitive control means – Electric switch controlled by the radiant energy responsive...
Reexamination Certificate
1999-12-30
2001-05-01
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
With radiant energy sensitive control means
Electric switch controlled by the radiant energy responsive...
C315S157000, C315S158000, C340S555000
Reexamination Certificate
active
06225748
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to passive infrared (PIR) motion detectors of the type used in residential outdoor lighting fixtures, for example, to illuminate a walkway or driveway when a person or automobile approaches. The invention is more particularly directed to electronic circuitry for energizing a light at a dim background level in the absence of motion and at a brighter level in response to motion.
PIR motion detectors are commonly used in conjunction with outdoor light fixtures and indoor light switches to turn on a light in response to a person moving in the field of view monitored by the motion detector. The motion detector typically causes the light to remain on for a pre-set duration after motion has been detected. Thus, for example, when a person enters the motion detector's field of view, a light comes on and remains on typically for five to fifteen minutes. The light is then automatically extinguished at the end of the pre-set period unless further motion is detected. In the earlier motion-activated light fixtures, either the light was on at its full-brightness level or it was off. Thus, at night the area remained dark until motion was detected and then the light only remained on for the pre-set duration after the motion ceased before returning to its dark state. These light fixtures also typically included a daylight sensor for disabling the motion detector during the daytime so that the light would not turn on during daylight hours, as well as a manual override feature by which a user could manually turn the light on at full brightness at any time by toggling a wall switch quickly between the on and off positions.
In a parallel development independent of motion-activated lighting, lighting fixtures providing background illumination at a low level were used in landscape and architectural design to focus attention on such features as walkways and garden paths, trees and prominent shrubbery, statuary and garden art, and ornamental building elements. Such lighting is commonly referred to as accent lighting and typically provides illumination at levels significantly less than full brightness.
The next development was the combination of motion-activated lighting with accent lighting. A number of companies introduced PIR motion detectors that provided for more than one level of illumination. Nippon Ceramic Company, Ltd. introduced a so-called stepped PIR motion detector that provided stepped dimming for use in lighting fixtures. The Nippon motion detector activated the light at full power in response to motion and partially activated the light to an accent level of only 25 percent power in the absence of motion. The daylight sensor disabled the unit in daylight hours so that the accent lighting would turn off automatically in the daytime. Such stepped-dimming PIR motion detecting light fixtures were also available from such companies as Ruud Lighting, Inc., Universal Energy Control, Inc., and Regent lighting Corporation.
An example of electrical circuitry for a stepped dimming motion-activated lighting fixture is disclosed in U.S. Pat. Nos. 5,598,066 and 5,747,93. This circuitry relies on a sensing technique known as zero-crossing detection to control the dimming and has the disadvantage that it is complex and calls for many electronic components, which increases cost, makes greater demands on quality control, and is potentially subject to greater failure rates.
SUMMARY OF THE INVENTION
The present invention provides a circuit arrangement for use in a PIR motion detector that is not only simple, but also provides for,an adjustable dimming level with only a comparatively few additional electronic components. With this circuit arrangement the user may set the accent background illumination level according to personal preference as appropriate for the particular installation.
Briefly, a circuit arrangement according to the invention is intended to be used in a PIR motion-activated lighting fixture of the type that includes a triac for energizing the light from the AC power mains and a triac firing circuit for firing the triac in response to motion. To provide the accent lighting level and to control the magnitude of that level, the circuitry includes a window comparator, in which the thresholds are set to define a dimming window, and a filter circuit responsive to the AC power line and providing an input signal to the window comparator. The filter circuit includes a circuit arrangement for shifting the phase of the input signal with respect to the AC power line and for contemporaneously scaling the amplitude of the input signal with respect to the AC power line such that the peak amplitude of the input signal diminishes as the phase shift of the input signal increases. That is to say, the amplitude and the phase shift of the window comparator input signal are scaled together. The magnitude of the phase shift and concomitant amplitude scaling may be set by the user. The circuitry further triggers the triac firing circuit in the absence of motion at the phase angle at which the input signal exceeds the dimming window. With this arrangement the light is energized during a fraction of the AC cycle determined by the magnitude of the input signal phase angle that may be adjusted over a continuous range by the user at the installation site.
The circuitry also includes a novel mechanism for disabling the background accent lighting during daylight.
Other aspects, advantages, and novel features of the invention are described below or will be readily apparent to those skilled in the art from the following specifications and drawings of illustrative embodiments.
REFERENCES:
patent: 3684919 (1972-08-01), Cramer
patent: 4225808 (1980-09-01), Saraceni
patent: 4450384 (1984-05-01), Krokaugger
patent: 5598066 (1997-01-01), Wiesemann et al.
patent: 5747937 (1998-05-01), Wiesemann et al.
Evans Scott T.
Lee Wade
Cordelia Lighting Inc.
Feng Paul Y.
Fulwider Patton Lee & Utecht LLP
Vu David
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