WO1997047162A1

WO1997047162A1 - Miniature electrical switching apparatus

Info

Publication number: WO1997047162A1
Application number: PCT/US1997/009651
Authority: WO
Inventors: David P. Rhoades; Edward M. Buckley
Original assignee: Cmc Technology Partners, L.P.
Priority date: 1996-06-04
Filing date: 1997-06-03
Publication date: 1997-12-11
Also published as: AU3299297A

Abstract

Miniature electrical switching apparatus including a thin disk-shaped switching unit (10), positionable within a light bulb socket, and a thin film flexible electrical conductor (14) having one end attached to the switching unit (10), the conductor being extendable through the gap between the electrically conductive inner wall of the socket and the electrically conductive outer surface of the bulb base disposed in the socket, and terminating at its distal end in a detector (12) for sensing light or other properties and generating a small electrical current for controlling actuation of the switching unit. The switching unit has a first contact (18) on one side for engagement with the socket center terminal, and a second contact (32) on an opposing side for engagement with the center terminal of a light bulb or other electrical load. The unit includes a thin circuit board (15) having control circuitry (26) mounted thereon. The control circuitry (26) receives operating power from the electrical load through the first contact and is responsive to the current communicated through the flexible conductor (14) to turn the power to the second contact ON and OFF. The circuitry also has provision for gradually applying power to the bulb (slow start) to extend bulb life, and has a hysteresis response to the incoming sensor signal so as to eliminate turn-ON and turn-OFF cycling.

Description

Specification

MINIATURE ELECTRICAL SWITCHING APPARATUS

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to electrical switching apparatus responsive to light, motion, sound or other conditions for turning ON and OFF electric devices, and more particularly to a switching device of a configuration suitable for location within a light socket and having an external sensor, which may include additional control circuitry, connected by a flexible electrical conduit for conducting electricity from the sensor to the switching device.

Brief Description of the Prior Art There has long been a need for apparatus that can be used to turn conventional lighting fixtures ON and OFF as a function of external conditions. For example, in the home environment various forms of such apparatus have been used exteriorly of the house to light porches, walks and driveways, and in the interior as a means to ward off potential unauthorized intruders during evening hours. The prior art has addressed this problem by providing bulky "piggy-back" light bulb receptacle devices for receiving a bulb and for carrying suitable daylight, sound or motion responsive switching apparatus. The devices are adapted to screw into the light fixture socket with the bulb then being screwed into the device. However, such devices are not usable in some types of fixtures and are awkward to use in other types of fixtures. U.S. Patent No. 4,023,035 to Rodriquez discloses a device of the type described above, which includes a housing containing a light sensor and responsive switch apparatus to turn the light OFF and ON with ambient light conditions. The housing has a threaded portion for joining the lamp socket and an opposing socket to receive the bulb. The result is a significant displacement of the bulb position relative to the original lamp socket. This is a disadvantage because many lamp shade brackets and/or enclosures are not designed with enough clearance to accommodate the added length. Also, the location of the sensor inside the shade limits its effectiveness in detecting the ambient light. Furthermore, such apparatus is not available or even practical for use in the smaller candelabra style fixtures. Other prior art U.S. Patents of general interest include Bernheim (3,056,035), Bernheim (3,163,768), Shepard (3,341,71 1), Berlin (3,538,379), and Pitel et al. (4,568,826). These patents disclose related useful apparatus, but do not disclose or suggest a device that can be easily integrated into an existing lamp structure without significantly displacing the bulb. As to other patented prior art, Ratner et al. (U.S. Patent No. 4,988,921) discloses an apparatus including a sealed lamp (light bulb) assembly having a built-in photo sensitive switch. A disadvantage of this approach is the costly necessity of throwing away the photo switch when the bulb burns out. Johnson in U.S. Patent No. 5,030,890, although not disclosing an ambient light responsive unit, does disclose a means for gradually applying power to a bulb, implemented in a disc shaped apparatus that is installed in the lamp socket beneath the bulb. A disadvantage of the device is that it displaces the bulb to an extent requiring the use of an insulating ring to cover exposed bulb threads. Heretofore, the most practical solution to the problem was the device disclosed in Rhoades et al. U.S. Patent No. 5,455,488 which relates to a switching device adapted to be positioned in a lamp socket beneath a bulb and having a fiberoptic light conductor extending between the bulb base and socket to a light collector at the distal end of the conductor. However, the use of the fiberoptic light conductor and internal photodiode limit the gain achievable with this design, which may result in less than desired reliability with certain lighting conditions, environments and/or fixtures. Furthermore, the fiberoptic conductor limits the use of external sensors and external control circuitry. There thus still remains a need for a small, universally acceptable device that is rigid, highly responsive to low light levels, and yet incorporates the various necessary features in a way that does not detract from the functional and/or aesthetic aspects of lamp fixtures in general. SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a miniature switching unit that can be positioned in a bulb-receiving socket between a bulb or other device and a corresponding socket terminal and which includes a sensor that can be extended from the socket without interfering with the normal relationship of bulb and socket. Another object of the present invention is to provide a sensor controlled switching device that can be incorporated into a conventional lamp socket in a way that does not materially displace the bulb. A further object of the present invention is to provide a sensor controlled switching device of the type described, the control portion of which can be located wholly within the socket or may be distributed between internal and external socket parts. A further object of the present invention is to provide a sensor activated switch which can be inserted into an electrical connection, such as a lamp socket, and used to automatically make or break the electrical path as a function of a predetermined sensed condition. Another object of the present invention is to provide a novel sensor activated switch of the type described that does not significantly alter the lamp's aesthetic design. A still further object of the present invention is to provide a sensor activated switch that is positionable between a bulb and a corresponding socket and that also includes other useful features. Briefly, a preferred embodiment of the present invention configured as a light sensing device includes a thin disk-shaped switching unit, positionable within a light bulb socket, and a thin film flexible electrical conductor having one end attached to the switching unit, the conductor being extendable through the gap between the electrically conductive inner wall of the socket and the electrically conductive outer surface of the bulb base disposed in the socket, and terminating at its distal end in a photosensor for gathering ambient or other light and generating a small electrical current for controlling actuation of the switching unit. The switching unit has a first contact on one side for engagement with the socket center terminal, and a second contact on an opposing side for engagement with the center terminal of a light bulb. The unit includes a thin circuit board having control circuitry mounted thereon, such circuitry being positioned to occupy available space between the conically shaped bulb base and the circuit board. The control circuitry receives operating power from the lamp through the first contact and is responsive to the current communicated through the flexible conductor to turn the power to the second contact ON and OFF. The circuitry also has provision for gradually applying power to the bulb (slow start) to extend bulb life, and has a hysteresis response to the incoming light intensity so as to eliminate turn-ON and turn-OFF flicker. Alternative sensors responsive to heat, motion, sound or other conditions can also be used. An important advantage of the present invention is that its small size and design result in substantial "transparency" when in use with most types of lamps and other lighting fixtures. Other advantages of the present invention reside in its physical simplicity and low cost. A further advantage of the present invention is its ease of installation and use. A still further advantage of the present invention is its inclusion of slow start, hysteresis, and over-temperature features along with its ability to turn a bulb or other electrical device ON and OFF in response to a predetermined sensor output. Yet another advantage of the present invention is that it can include optional features such as the ability to time-out after a predetermined period of operation to save electricity, and the capability of being remotely adjusted or disabled by the momentary interruption of power applied thereto. Still another advantage of the present invention is that it may be used to control a wide variety of electrical devices plugged into an electrical receptacle inserted into a socket. Yet another advantage of the present invention is that it may be used as a means for facilitating the remote activation or deactivation of an electric device using a directional light beam. Yet another advantage of the present invention is that it may contain additional control circuitry, of any reasonable size, disposed outside of the socket, thereby allowing use of a motion sensor, sound sensor or other type of sensor and control circuitry to activate the switching unit. Still another advantage of the present invention is that various constructions are possible, depending on the type of sensor used, to avoid problems with heat, size or proximity constraints. These and other objects and advantages of the present invention will no doubt become apparent to those skilled in the art after having read the following detailed description of the preferred embodiment which is illustrated in the several figures of the drawing. IN THE DRAWING Fig. 1 is a pictorial view generally illustrating a preferred embodiment of the present invention; Fig. 2 is a schematic circuit showing the electrical components utilized in the embodiment of Fig. 1; Fig. 3 is a system block diagram showing the principal functional components of the controller chip of Fig. 2; Figs. 4 and 5 are plan views of the top and bottom of the circuit board of the embodiment of Fig. 1 ; Fig. 6 illustrates the make-up of the thin film conductors; Figs. 7 and 8 are respectively partially broken plan and side views illustrating the flexible thin film conductor and photosensor assembly used in the preferred embodiment; Fig. 9 is an exploded view illustrating assembly of the various components to the PC board and the mounting of the covering cap thereto; Fig. 10 is a cross-sectional view of a lamp socket illustrating insertion of the preferred embodiment between bulb and socket base; Fig. 11 is a schematic circuit illustrating an alternative embodiment of the present invention; Fig. 12 is a pictorial view generally illustrating the alternative embodiment of Fig. 11 ; and Fig. 13 is a block diagram illustrating another alternative embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to Fig. 1 of the drawing, a preferred embodiment of the present invention is shown to include a disk-shaped switching unit 10 and photosensor 12 interconnected by a flexible conducting strip assembly 14. The switching unit 10 is essentially comprised of a thin circular printed circuit board 15 upon which are formed conductive traces 16 which, as will be described below, connect an upper contact pad 18 and a lower contact pad (not shown) with a plurality of electrical components and switching circuit components 19 disposed around the perimeter of the board 15. The circuit board and its components are covered by an annular cap 20 or a suitable deposit of encapsulating material. The height and diameter of unit 10 are selected to be small enough to allow the unit to fit into the particular type of light socket with which the device is intended to be used. For example, for standard light fixtures the diameter might be on the order of 0.950 inch, whereas for candelabra or carriage light fixtures, and the like, the diameter might be approximately 0.375 inch. The recessed region 13 on the top side of the unit is made large enough and deep enough to accommodate the center contact structure of the bulb type with which the device is intended to be used. Contact pad 18 and the lower contact pad on the bottom side of unit 10 are made of a suitable conductive material and size to assure good ohmic contact with a bulb contact and socket center contact respectively. Their thickness is also made as thin as practical so that the combined thickness of the two contacts and the separating circuit board is as small as possible. Note that it is this thickness which determines the height to which the bulb is lifted in its socket with the subject device in use. In practice it is desirable that the thickness be no greater than 0.031 inch. The sensor 12 is a photodiode or other light-responsive means suitably affixed to one end of the assembly 14 and is operable to conduct electricity as a function of the light to which it is subjected. The opposite or distal end of assembly 14 extends into the cap 20 where, as will be described below, it interfaces with the circuit board 15. The assembly 14 is essentially a thin strip of plastic having embedded therein a pair of thin strips 21 and 22 of a conductive material, such as aluminum or copper, capable of conducting electricity to and from the photodiode 12. The conductors 21 and 22 may be configured to include current limiting fuse links 23 and 24, respectively, which can be formed of discrete fuse elements (not shown) or simply carefully sized segments of the conductive strips of which they are a part. The assembly 14 may be of any length varying from just long enough to suitably extend out of the socket to several times that length so that the photosensor can be placed in a position to have optimum exposure to ambient or other light yet not be influenced by the lamp it controls. Note that the vertically rising strip portion 25 of assembly 14 is thinner than the rightwardly extending portion 26. An explanation and further details of the assembly are given below. In Fig. 2 of the drawing, a schematic diagram is provided showing the principal electrical and electronic components included on the circuit board represented by the dashed lines 15'. It should of course be kept in mind that the circuit board 15 is actually circular rather than rectangular as depicted in Fig. 2. The principal operative component on circuit board 15 is an application- specific integrated circuit (ASIC) 26 which controls operation of the device. Attached to various inputs of ASIC 26 by circuit board traces 16 are various resistors and capacitors, a diode bridge 28 including four 1SS376 diodes, a TC404C4 TRIAC 30, and upper side and lower side bulb and socket contact pads 18 and 32. The photosensor 12 is connected to ASIC 26 via the conductors 21 and 22 of strip assembly 14. Resistor 32 is an amplifier gain resistor for photodiode 12; capacitor 34 is a filter capacitor for photodiode 12; resistor 36 is a bias current set resistor; capacitor 38 is a bypass capacitor; mode selector jumper contacts are indicated at 40 and 42; capacitor 44 is a phase control capacitor; capacitor 46 is a power supply capacitor; resistor 48 is a surge-limiting resistor; and the optional fuse links in conductors 21 and 22 are indicated at 23 and 24. By providing a jumper across both of contacts 40 and 42, the device will have a two-hour timing function; providing a jumper across contacts Al alone will cause the device to have a three-hour timing function; and by providing a jumper across the contacts 42, the device will have a five-hour timing function. If no jumper is provided across the contacts 40 and 42, once triggered, the device will operate continuously until a predetermined light level is sensed by photosensor 12. • The HV9501 ASIC is a custom integrated circuit which provides automated light sensing and control of an incandescent light bulb. The monolithic integrated circuit is built with a high voltage CMOS process which allows it to interface directly with the Ac line voltage at its terminals 29 and 31. The chip contains circuitry to control an incandescent lamp with a variety of features, including: • Input Hysteresis - prevents flickering. • Input Validation - internal timer verifies valid light transitions. • Manual Over-Ride - Short duration power interruptions (<3 seconds), supplied by the user "toggling" the power switch (lamp switch or wall switch), signal the chip to change the state of the bulb. • "Slow-Start"- extends bulb life by controlling the initial in-rush current. • Dual mode operation - Timer or non-timer modes. ^• Over-temperature sensing and control - for safety, limits maximum temperature. This dual purpose circuit is capable of working as a dusk-to-dawn controller sensing both light-to-dart and dark-to-light transitions, or as a timed controller where it is triggered only by the light-to-dark transition and then enables a fixed length timer. As a timer, the chip can be set to timer-out in 2, 3 or 5 hours. The different modes are not user accessible but are selected as wire bonding options. Internal over-temperature control circuitry limits maximum socket temperature. A more detailed block diagram showing the principal operative components of ASIC 26 is depicted in Fig. 3 of the drawing. Each of these components is briefly described as follows: INPUT OP AMP: The Input Opamp 100 operates as a zero-bias photovoltaic-mode amplifier for an external photodiode detector 12 (Fig. 2) connected across device pads 5 and 6. This mode of operation provides superior performance over a wide temperature range. The output signal, Vamp, is applied to the input of an Input Comparator 102. The Input Pads are: • (5) COM1 :Low noise common • (6) PD: Detector (photodiode) input • (7) CX: Filter capacitor 34 connection • (8) RC:Input Opamp gain resistor 32 connection INPUT COMPARATOR: The Input Comparator 102 monitors the Vamp signal and compares it to an internal reference value, 1.1 Vref. When Vamp is below 1.1 Vref, the comparator output goes low. The circuit also includes hysteresis to minimize flickering. The comparator output is converted to digital signals, LIGHT and LIGHT-BAR, and is synchronized with the internal clock, ZX. COLD START: The Cold Start circuit 104 generates a signal, RΛW-CS-BAR, used to reset internal circuits at initial power-up. It is also used to distinguish "cold starts" (initial power- up) from "warm starts" (power toggle). BANDGAP REFERENCE: The Bandgap Reference 106 provides an accurate voltage reference output, 1.1 Vref, over the specified temperature range. VBIAS GENERATOR: The Vbias Generator 108 produces two precision temperature- independent currents which are used throughout the chip. Input Pads are: • (4) RB:External current setting resistor 36 connection POWER INTERRUPT DETECTOR: This circuit 110 acts as a low-voltage detection comparator for recognizing when the power to the device has been toggled or interrupted by the user. Additionally, it includes power shut-off switches (not shown) which are large, pass transistors used to switch off power to all analog and selected digital circuits during the power interruption. It generates the digital clocking signals, ZX and ZX-BAR, and also generates the PWR-SW-BAR signal used to toggle the RUN circuit. HIGH VOLTAGE CIRCUIT: Two separate functions are included within the high voltage circuitry 112. The TRIAC gate driver function receives a digital trigger signal, T-DRV, from the TRIAC phase controller 114 and generates the required TRIAC gate drive signal, GATE, used to turn on the TRIAC. Also included is a high voltage interface which generates the initial 120 Hz clock signal, RAW-ZX, and provides voltage regulation for the low voltage supply, Vcci. Input Pads are: • (21 ) COM2 :High-current common • (22) COMSTC:Full-wave bridge common • (23) VCC Low voltage supply connection for external capacitor • (24) GATE:TRIAC gate drive • (26) RAWDC:High voltage input RAW DC from the bridge rectifier 28 is a full-wave rectified sine wave. This signal is sampled and divided down with a resistive divider (not shown) to generate RAW-SYNC. RAW SYNC is applied to one input of the sync comparator 116 while 1.1 Vref is applied to the other input. When RAW SYNC is equal to or greater than 1.1 Vref, the sync comparator output, SYNC, is high or true. The ratio of the resistor divider network is selected such that when RAW DC is equal to ! ₂ the peak full-wave rectified sine wave (85 Volts) then RAW SYNC will be equal to 1.1 Vref. Detection of the ^lΛ peak is equal to a 30° delay from zero-crossing for 120 VAC. The SYNC signal is used to initiate the firing of the TRIAC 30. The 30° TRIAC firing hold-off is necessary in this application in order to allow time to charge the ASIC's power supply. The ASIC requires a separate power supply and charging circuit because while the TRIAC is ON, the voltage across it and the ASIC drops to zero. 10 SYNC COMPARATOR: This circuit 116 takes the RAW-SYNC from HV Circuit 112 signal and generates a synchronization signal, SYNC, at 30° relative to 60Hz. Zero-crossing point is for use in the TRIAC phase control circuit 1 14. TEMPERATURE CONTROL: The temperature control circuitry 118 monitors the chip temperature and modulates (increases) the TRIAC phase control, PHASE-CON, as temperature increases. Increases in temperature increase the 30° phase delay to the TRIAC and reduce the power and temperature. SLOW START: This circuit 120 modulates the TRIAC phase control signal, PHASE- CON, during initial power-up (RUN) of the light bulb. This action controls the initial in-rush surge current to the bulb and thereby extends the life of the bulb. TRIAC PHASE CONTROL: This circuit 1 14 combines a precision voltage ramp generator with a comparator and precision one-shot to generate the TRIAC gate timing signal, T- DRV, during times when the bulb is on (RUN). The ramp can be externally adjusted by selection of a phase control capacitor at the PC pad (20). DIGITAL CONTROL LOGIC: The digital control logic 122 contains all the necessary logic to perform the required functions: • Initialization and synchronization (power-up) of the chip. The signal RAW-CS- BAR goes high when the analog voltages are within specification. This signal is clocked by ZX (zero crossing) and is used as a chip wide initial power-ON reset signal. RAW-ENABLE is also clocked by ZX and indicates, during the power interrupt sequence, that the chip DC supply provided by capacitor CI is within specification. • Light transition detection and pulse generation of control signals. The complimentary signals LIGHT and LIGHT-BAR are monitored by the digital control logic for changes of state. Transitions of LIGHT from high to low are used to generate a pulse, DuskP-Bar, indicating dusk. This signal is used to set the RUN flipflop and, if in timer mode (TM), to start the timer. A similar signal, DawnP-Bar, indicating dawn, is used to reset the RUN flipflop in dusk-to- dawn mode (DDM). • Timer control circuits. The timer control circuit is used to start and stop the timer at the required times. The timer control is composed mainly of a flipflop which is set or reset by the appropriate signals. While the timer flipflop is set, ZX generates TCLK which in turn clocks the timer. When the timer flipflop is reset, the TRST (timer reset) signal clears all timer stages. The timer flipflop is set following the detection of dusk or a power interrupt. It is reset by its terminal count, LTC-BAR. • RUN state flip-flop. The state of the light bulb is controlled by the RUN state flipflop. When RUN is true, the bulb is ON, and when RUN is false, the bulb is OFF. The flipflop can be set, reset or toggled. It is set by DuskP-Bar, cleared by LTC-BAR, and toggled by PWR- SW-BAR which indicates a power interrupt detection. TIMERS AND ADDRESS SELECTION: The timers section of circuit 124 contains all the counters necessary to count the line frequency and generate time delays of 2 hours, 3 hours and 5 hours. In addition, this section contains the address (external jumpers, AO (2) and Al (3)) decoding to select the appropriate time delay. Fig. 4 is a plan view of the circuit board 15 showing the conductive traces and pads formed thereon. Note the large bulb contact 18, the two flexible conductor contact pads 80 and 82, the ASIC pad 79, etc. Fig. 5 is a bottom plan view of circuit board 15 showing the socket center contact 32. In Fig. 6, construction of the conductive ribbon portion of strip assembly 14 is shown at 60 to include a first elongated strip of flexible plastic 62 having the conductive traces 21 and 22 screened or otherwise affixed to the upper surface thereof and running end to end. In the preferred embodiment, the strip 60 is typically 4" to 8" long, 0.200" wide, and 0.003" to 0.005" in thickness. The strip is constructed from a high performance plastic material such as Polyester, Polyimid, Kapton, Kaladex 2030, Melinex 238 or Ultem. These materials have excellent abrasion resistance, high temperature performance and good flexibility, which allow them to be successfully used in the harsh environment between a bulb and socket. The traces 21 and 22 are typically 0.040" wide on centers separated by 0.100". The traces 21 and 22 may be adhered to strip 62 by a 1 mil thickness of acrylic adhesive and may be made of R&A copper, A ounce. Overlaying the traces 21 and 22 and extending just short of each end is a second layer of flexible plastic strip 64 typically of material identical to that of strip 62 and adhered to strip 62 and traces 21, 22 with a 1 mil acrylic adhesive. In the preferred embodiment, at the device end 66, a trace length of approximately 0.08" is left uncovered, as is a trace length of approximately 0.20" at the photodetector end 68. The exposed trace ends are flash gold or solder plated to facilitate later connection thereto. If fusing resistors are to be used, they can either be constructed by narrowing the line width of the traces for a predetermined length, or a short break left in each trace can be joined by screen-printing it with a resistive material such as Minico M3014-1 or equivalent, so as to allow no more than 5 milliamps of current to flow through the traces. Turning now to Fig. 7 which is a top plan view, and Fig. 8 which is a longitudinal cross- section taken along the line 8-8 in Fig. 7, the completed strip assembly is illustrated in partially broken form and shown with the photodetector 70 soldered or otherwise connected to the exposed trace ends 20 and 24 at 71 and 72, respectively. Overlaying strip 60 is a metal strip or wire 74 which will serve as a stiffener allowing the assembly to be oriented in a selected direction and remain in such disposition until moved. The strip 60, supporting strip 74, and photodetector 70 are then overcoated with a suitable flexible heavy insulation 76 for all of its length except approximately 0.80" at the device end of strip 60. This molded insulative coating serves to both protect and form an integral light-directing shield for the assembly. Note that the molded coating has an opening 78 at the distal end for admitting light to photodetector 70. In the preferred embodiment, this overcoating material is made of silicone rubber. Referring now to Fig. 9, details of the attachment of the strip assembly 14 to the circuit board 15 are illustrated. As depicted, the uncovered end 66 of strip 60 is bent approximately 90° relative to the remainder of the strip, and the exposed traces (not shown) are soldered or otherwise conductively joined to a pair of circuit board pads 80 and 82 of the previously populated board 15. A cap 84 having a notch 85 formed therein is aligned with the strip 60 and board 15, lowered into place on the board, and glued or otherwise attached to the circuit board to form a protective housing enclosing the electrical and electronic components affixed to the upper surface of board 15. Note that a central opening 86 fits about bulb contact pad 18 leaving it exposed to be engaged by the center contact of the bulb. After the cap is secured to the board, a plug or suitable encapsulation material 88 is added as a final assembly step. As an alternative to the illustrated cap 84, a similar "shell" or cap-like device could be transfer-molded around the populated circuit board 15. In Fig. 10, installation of the assembled light-responsive switching device is illustrated. With the bulb 90 removed from the threaded metal socket 92 disposed within an insulative fixture 94, the switching unit 10 can be inserted into the socket as indicated so that the pad 32 engages the socket's center contact 96 and the strip 14 extends out of the socket. Note that the length of uncoated ribbon 60 extends upwardly approximately the same height as that of the socket 92. However, a short segment 98 of the heavily insulated portion of strip assembly 14, including the flexible stiffener strip 74 (Fig. 7), still resides within the fixture opening. Bulb 90 is then threaded into socket 92 in the usual fashion with the thin strip portion 60 being deformed between the bulb threads and socket wall. Once bulb 90 is threaded far enough into socket 92 for its center or base contact 99 to engage pad 18, the switching unit is fully installed, and one need do nothing more than ensure that strip 14 is bent so that photodetector 12 faces away from bulb 90 (and perhaps also away from any highly reflective shade surface or other reflector). So installed, and with the normal light switch (not shown) placed in the ON position, in daylight conditions photodiode 12, operating in the photovoltaic mode, will generate a current proportional to the ambient light level and cause the controller (ASIC 26) to in turn cause TRIAC 30 to be nonconductive, and bulb 90 will be held in a non-energized state until the ambient light level drops below a predetermined threshold, at which time the light-responsive photodiode 12 will generate substantially less current, signalling the controller to turn ON the TRIAC 30 (Figs. 2 and 3), thereby completing a circuit through the switching unit to energize bulb 90. Depending upon which of the contacts 40 and 42 have jumpers placed across them, the bulb will continue to be energized for two hours, three hours, five hours or all night. Referring now to Figs. 1 1 and 12, an alternative embodiment of the present invention is illustrated which, although using substantially the same components used in the previous embodiment, differs in that ASIC and associated circuit components are disposed at the distal end of the flexible strip assembly. More specifically, with the diode bridge 228, resistor 248, TRIAC 230 and contact pads 218 and 232 remaining on the socket-receiving encapsulated board 215, the sensor 212, the ASIC 226 and their associated resistors 232 and 236, capacitors 234, 238, 244, 246 and jumper contacts 240 and 242 are all affixed to a second PC board 217 attached to the distal end of a three-conductor strip assembly 214. The strip assembly 214 is made in the same way that strip 14 (Figs. 7-8) is constructed except that it includes three conductive strips 221, 222 and 223, each having a separate current- limiting fuse link (223, 224, 225). The flexible insulating material used to encapsulate the out-of- socket portion of the strip 214 is also used to encapsulate the "head" assembly 209. The principal advantage of this embodiment is that with the ASIC 226 disposed within the head 209, space within the socket is not a limiting factor and almost any type of sensor can be accommodated. Moreover, more than one type of sensor could be included in the head 209; for example, a particular application might require both a light level sensor for controlling ON/OFF cycles while an infrared motion sensor might be included to actuate an electrical fixture to signal the presence of an intruder. Among the advantages of this embodiment is that the photodiode can be made arbitrarily large due to virtually unlimited space outside the bulb base area to provide high gain at even low light levels. Fig. 13 illustrates one possible implementation of a motion sensor and power line interface of a type contemplated by the present invention. In this embodiment, which in all other details is similar to that of Fig. 12 and corresponding components bear corresponding call-out numbers, a pyroelectric infrared (PIR) sensor 250 and PIR motion detector 252 are substituted for the light- responsive sensor 212 (and its associated circuitry) of the Fig. 12 embodiment. A typical sensor would be an LHi 954 or 958 manufactured by EG&G Heimann. The LS6501 PIR Motion Detector 252, manufactured by LSI Computer Systems, Inc., is a single monolithic integrated circuit designed for detecting motion from PIR sensor 250 and initiating appropriate responses. The circuit contains all of the functions required to detect and process human motion for use in applications such as light control and intrusion alarm. The major functions are: amplification of the input signal, establishing switching thresholds, environmental conditions such as background interference and ambient light, timing functions and output drive. PIR sensor 250 and motion detector circuit 252 function to detect the presence of a human body within the detection range. An output signal from the detector 252 is coupled to the HV9501 controller 226. In this application the HV9501 is configured for the dusk-to-dawn mode of operation. This mode will disable the internal timing features and allow appropriate responses to the motion detector signals. The output of the HV9501 drives the gate of the TRIAC in the internal unit 215. The PIR sensor 250, PIR motion detector integrated circuit 252, and the HV9501 226 are all external to the socket. The thin flex strip 214 connects the external components to the diode bridge 228 and TRIAC 230 to be located internal to the socket. In accordance with the present invention is that the extremely thin strip portion placed between bulb base and socket does not in any way interfere with installation of the bulb yet allows sufficient current to flow through the conductive traces embedded therein to cooperate with the photodetector 12 or other sensor included in the external port. Another advantage of the present invention is that in normal use it rarely suffers from pointing/directional problems. With adequate gain, indoor timer units need only to "look down" at the floor to operate correctly. Moreover, the photodiode operates reliably in the cooler environment outside the bulb/socket area and thus is more sensitive and reliable than competing socket-mounted photocell apparatus. Furthermore, the flex strip of the present invention is very inexpensive and does not require any special lenses or other light-gathering mechanisms to augment the light-gathering capability of the photodiode. As suggested above, devices in accordance with the present invention may be made to suit any size or type of light socket, and with appropriate circuit modifications be adapted for use in DC-powered systems, for example to turn vehicle lights ON and OFF as a function of input or ambient light. Devices constructed in accordance with the present invention may utilize motion, sound or other sensors, in place of the photodetector, to activate the switching unit, for control of a light or other electrical device, including motors, alarms, etc. Although this invention has been described in terms of preferred embodiments, it will be appreciated that various alterations and modifications thereof may become apparent to those of ordinary skill in the art. For example, other circuitry, sizes, shapes, and/or constructions may be substituted for those shown herein. It is therefore intended that the appended claims cover all such alterations and modifications as fall within the true spirit and scope of the invention. What is claimed is:

Claims

1. An electrical switching apparatus for use in association with a socket into which a light bulb or other electrical device may be installed, which socket includes at least one socket contact aligned for engagement with a power supply contact of the light bulb or other device, comprising: a thin switching unit adapted for disposition within a socket and including a switching circuit having a first contact for engagement with the socket contact, and a second contact for engagement with the power supply contact of a light bulb or other device disposed in the socket; a photosensor; and a conductive assembly including an elongated strip of insulation material having current- carrying conductors therein and having first ends of said conductors connected to said switching circuit and second ends of said conductors connected to said photosensor, at least a portion of the length of said conductive assembly being thin enough to pass between the light bulb or other device and the socket, such that with the photosensor located outside of the socket, and with the switching circuit located inside the socket, a first state of the photosensor causes the switching circuit to complete a path for electrical energy between the socket contact and the power supply contact causing the bulb or other device to be turned ON, and in response to a second state of the photosensor, lo break the electrical path from the socket contact to the power supply contact causing the bulb or other device to be turned OFF.

2. An electrical switching apparatus as recited in claim 1 wherein said conductive assembly further includes stiffening means disposed along at least a portion of the length of said strip for maintaining said assembly in a selected configuration.

3. An electrical switching apparatus as recited in claim 2 wherein said stiffening means includes a length of metallic material affixed to said strip.

4. An electrical switching apparatus as recited in claim 3 wherein said conductive assembly further includes insulating means enveloping said strip, said stiffening means and at least a part of said photosensor.

5. An electrical switching apparatus as recited in claim 1 wherein said switching circuit generates a switching signal, and wherein said switching unit includes TRIAC means responsive to said switching signal and adapted for connection across said first and second contacts and in series with said socket means and an AC power source.

6. An electrical switching apparatus as recited in claim 5 wherein said switching circuit includes a slow-start circuit means for causing the duty cycle of said switching signal to change from a low value to a high value during a predetermined initial portion of each lamp turn-ON operation, thereby causing the power supplied to said lamp to ramp up from a first value to a second value during said initial portion.

7. An electrical switching apparatus as recited in claim 1 wherein said switching unit includes a printed circuit board having said first and second contacts respectively formed on opposite sides and covering the center portions thereof, said circuit board having a plurality of electronic circuit elements forming said switching circuit disposed on at least one side of said printed circuit board at locations surrounding said contacts.

8. An electrical switching apparatus as recited in claim 5 wherein said switching unit further includes timing means responsive to said switching signal and operative to disable said switching unit after a predetermined time has elapsed following turn-ON of said switching element.

9. An electrical switching apparatus as recited in claim 1 wherein said switching circuit generates a switching signal and said switching unit includes: an electronic, signal-responsive power switching element connected between said first contact and said second contact; and high voltage circuitry responsive to said switching signal and operative to develop a signal for causing said switching element to conduct and complete a conductive path between said first and second contacts.

10. An electrical switching apparatus as recited in claim 9 wherein said switching element is a TRIAC and means are provided for coupling said switching signal to the control gate of said TRIAC.

11. An electrical switching apparatus as recited in claim 10 wherein said high voltage circuitry includes rectifier means for converting AC line current applied to the socket to direct current, and a semiconductor driver device responsive to said switching signal and operative to apply said direct current to the gate of said TRIAC to cause it to conduct.

12. An electrical switching apparatus as recited in claim 11 wherein said switching signal alternates between a first state and a second state and wherein said switching circuit further includes a slow-start circuit means for causing the duty cycle of said switching signal to change from a low value to a high value during a predetermined initial portion of each lamp turn-ON operation.

13. An electrical switching apparatus as recited in claim 12 wherein said switching unit further includes timing means responsive to said switching signal and operative to disable said switching unit after a predetermined time has elapsed following turn-ON of said switching element.

14. An electrical switching apparatus as recited in claim 13 wherein said switching unit includes a printed circuit board having said first and second contacts respectively formed on opposite sides and covering the center portions thereof, said circuit board having a plurality of electronic circuit elements forming said switching circuit disposed on at least one side of said printed circuit board at locations around said contacts.

15. An electrical switching apparatus as recited in claim 1 wherein said switching unit includes a circular printed circuit board having said first and second contacts respectively formed on opposite sides and covering the center portions thereof, said circuit board having a plurality of electronic circuit elements forming said switching circuit disposed on at least one side of said printed circuit board at locations surrounding said contacts.

16. An electrical switching apparatus for use in association with a socket into which a light bulb or other electrical device may be installed, which socket includes at least one socket contact aligned for engagement with a power supply contact of the light bulb or other device, comprising: a thin switching unit adapted for disposition within a socket and including a switching circuit having a first contact for engagement with the socket contact, and a second contact for engagement with the power supply contact of a light bulb or other device disposed in the socket; sensor means for location outside of the socket; and a conductive assembly including an elongated strip of insulation material having current- carrying conductors therein and having first ends of said conductors connected to said switching circuit and second ends of said conductors connected to said sensor means, at least a portion of the length of said conductive assembly being thin enough to pass between the light bulb or other device and the socket, such that with said sensor means located outside of the socket, and with the switching circuit located inside the socket, a first state of said sensor means causes the switching circuit to complete a path for electrical energy between the socket contact and the power supply contact causing the bulb or other device to be turned ON, and in response to a second state of said sensor means, to break the electrical path from the socket contact to the power supply contact causing the bulb or other device to be turned OFF.

17. An electrical switching apparatus as recited in claim 16 wherein said sensor means includes a light level detector responsive to light in the vicinity of said apparatus and operative to influence current flow through said current-carrying conductors.

18. An electrical switching apparatus as recited in claim 17 wherein said sensor means includes a motion detector responsive to object movement in the vicinity of said apparatus and operative to influence current flow through said current-carrying conductors.

19. An electrical switching apparatus as recited in claim 17 wherein said sensor means includes a heat detector responsive to thermal energy in the vicinity of said apparatus and operative to influence current flow through said current-carrying conductors.

20 20. An electrical switching apparatus as recited in claim 17 wherein said sensor means includes a sound detector responsive to sonic energy in the vicinity of said apparatus and operative to influence current flow through said current-carrying conductors.

21. An electrical switching apparatus as recited in claim 16 wherein said sensor means includes a condition detector and logic circuit means responsive to output signals developed by said detector and operative to generate control signals for communication through said current-carrying conductors for controlling operation of said switching circuit.

22. An electrical switching apparatus as recited in claim 21 wherein said switching circuit generates a switching signal, and wherein said switching unit includes TRIAC means responsive to said switching signal and adapted for connection across said first and second contacts and in series with said socket means and an AC power source.

23. An electrical switching apparatus as recited in claim 22 wherein said switching circuit includes a slow-start circuit means for causing the duty cycle of said switching signal to change from a low value to a high value during a predetermined initial portion of each lamp turn-ON operation, thereby causing the power supplied to said lamp to ramp up from a first value to a second value during said initial portion.

24. An electrical switching apparatus as recited in claim 23 wherein said switching unit further includes timing means responsive to said switching signal and operative to disable said switching unit after a predetermined time has elapsed following turn-ON of said switching element.

25. An electrical switching apparatus as recited in claim 16 wherein said switching circuit generates a switching signal and said switching unit includes: an electronic, signal-responsive power switching element connected between said first contact and said second contact; and high voltage circuitry responsive to said switching signal and operative to develop a signal for causing said switching element to conduct and complete a conductive path between said first and second contacts.

26. An electrical switching apparatus as recited in claim 25 wherein said switching element is a TRIAC and means are provided for coupling said switching signal to the control gate of said TRIAC.

27. An electrical switching apparatus as recited in claim 26 wherein said high voltage circuitry includes rectifier means for converting AC line current applied to the socket to direct current, and a semiconductor driver device responsive to said switching signal and operative to apply said direct current to the gate of said TRIAC to cause it to conduct.

28. An electrical switching apparatus as recited in claim 16 wherein said switching signal alternates between a first state and a second state and wherein said logic circuit means further includes a slow-start circuit means for causing the duty cycle of said switching signal to change from a low value to a high value during a predetermined initial portion of each lamp turn-ON operation.

29. An electrical switching apparatus as recited in claim 28 wherein said logic circuit means further includes timing means responsive to said switching signal and operative to disable said switching unit after a predetermined time has elapsed following turn-ON of said switching element.