Electric lamp and discharge devices: systems – With radiant energy sensitive control means
Reexamination Certificate
2000-09-15
2001-10-09
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
With radiant energy sensitive control means
C315S156000, C315S157000, C315S159000
Reexamination Certificate
active
06300721
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to outdoor lighting controls and, more particularly, to reducing electrical energy usage and increasing the life span and durability of such controls.
2. Description of the Related Art
A conventional photocontrol arrangement employs a photosensor for detecting outdoor ambient light and for converting the detected light into an analog electrical signal. A level detector converts the analog signal into a digital signal having high and low states corresponding to daylight and nighttime conditions, respectively. The digital signal is conducted to an electrical load switching relay which, in turn, switches the load, i.e., an outdoor lighting system, off during daylight, and on during nighttime.
The load relay used in all known photocontrol arrangements have a pair of contacts which are “electrically held”, that is the contacts are held apart in an open state as long as the load relay is electrically energized by an electrical current conducted to a coil of the load relay. When this electrical current is discontinued, the load relay is not energized, and the contacts return to the closed state. A reverse arrangement is also possible when the contacts are held closed when the relay is energized.
In either event, the load relay is using electrical energy to hold the contacts together or apart, either all day long during one of the states, or all night long during the other of the states. This is not only wasteful of energy, but also can cause overheating, particularly in small photocontrol enclosures.
Moreover, electrically held relays generally operate over a wide range of input voltages, for example, 105V to 285V and, as a result, a voltage regulator is needed. This regulator also consumes non-negligible power.
OBJECTS OF THE INVENTION
Accordingly, it is a general object of the present invention to reduce electrical energy expenditure in such photocontrol arrangements.
More particularly, it is an object of the present invention to prevent overheating in photocontrol enclosures.
Still another object of the present invention is to increase the life span and durability of such photocontrol arrangements.
It is yet another object of the present invention to eliminate the voltage regulator in such arrangements.
SUMMARY OF THE INVENTION
In keeping with the above objects and others which will become apparent hereafter, one feature of the present invention resides in a photocontrol arrangement for controlling an outdoor lighting system. The arrangement includes a photosensor circuit having a photosensor responsive to ambient outdoor light for generating an analog electrical signal, and a level detector operative for converting the analog signal to a digital level signal having a low state or “dark” signal when the ambient light is below a threshold light level, and a high state or “light” signal when the ambient light equals or exceeds the threshold level.
The arrangement further includes a pulse-actuated, electrically energizable, stepper relay, also known as a mechanical or ratchet relay, operatively connected to the lighting system and having a pair of electrical contacts that engage each other in a closed state to conduct an electrical current to the lighting system to illuminate the same, and that are spaced apart from each other in an open state to prevent the electrical current from reaching the lighting system to extinguish the same. The contacts are either mechanically held together in the closed state, or mechanically held apart in the open state, or both.
A pulse generator circuit is operatively connected between the photosensor circuit and the stepper relay, and generates a pulse to actuate the relay to the closed state when the dark signal is generated, and generates another pulse to actuate the relay to the open state when the light signal is generated. Each pulse has a limited time duration during which the state of the relay is changed. The stepper relay is electrically energized during the limited time duration of each pulse to reduce electrical energy usage.
Preferably, the pulse generator circuit includes a monitor circuit for monitoring the state of the contacts of the relay, and for generating a contact signal having an open value in the open state, and a closed value in the closed state. A logic circuit generates the pulse upon simultaneous generation of the dark signal and the open value of the contact signal, and generates the other pulse upon simultaneous generation of the light signal and the closed value of the contact signal.
In accordance with this invention, a relay having mechanically held contacts only uses electrical energy when it is changing state and only during the limited time duration of a pulse. This contrasts with the known electrical relays having electrically held contacts which are energized and consume electrical energy throughout the duration of each state, i.e., all night long, or all day long. Concomitantly, the energy efficient relay of this invention does not heat up as the prior art relays and contributes to increasing the life span and durability of the arrangement.
Moreover, the present invention enables the relay to be made with a higher contact force to move the contacts, because a large amount of energy can be applied to the contacts for a short period of time without overheating the relay. This feature enables a larger electrical current to be switched, again without overheating the relay. Since the electrical pulse is only applied for a short time, on the order of a fraction of a second, the voltage regulator can be eliminated, again without overheating the relay.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.
REFERENCES:
patent: 4451763 (1984-05-01), Sodini
Duve George
Mills John Edward
Area Lighting Research, Inc.
Kirschstein et al.
Vu David
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