Abstract:
A modular light fixture specially adapted for flexible, cost-effective, and safe retrofit and maintenance, particularly in large commercial lighting applications. The light fixture preferably includes a frame with one or more lampholders and a detachable power pack with a ballast, with modular connectors used to provide an electrical connection between the detachable power pack and the lampholders. Other aspects of the invention relate to methods of redeploying lighting, and a modular light fixture kit, for example to be used in lighting retrofit and maintenance.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to energy management and utilization in large commercial buildings, and more particularly to a modular light fixture apparatus and method therefor. 
   BACKGROUND OF THE INVENTION 
   In large commercial buildings, recurring electricity costs for lighting can be more than half of the total energy budget. Consequently, there are considerable economic benefits to be obtained through more efficient lighting techniques. For example, simple devices such as motion sensor switches or light timers are often used to reduce wasted energy by reducing unnecessary lighting. 
   Long term energy and lighting management in large commercial lighting applications presents greater challenges. Lighting requirements in different areas of a store or manufacturing plant may change as departments move or reorganize. Lighting technologies change over time, delivering improved performance and efficiency. Thus, it may become necessary or desirable to replace obsolete lighting technology with newer technology, or to relocate, enhance, or maintain existing lighting fixtures. Especially as energy costs continue to rise, many existing commercial buildings will eventually consider some form of lighting retrofit or redeployment. 
   Existing commercial buildings vary widely in age, construction, and intended use, so the available electric power sources may have any of several different voltage levels, and access to that power may be provided using a variety of electrical connection types. Support and mounting techniques will vary. Further, lighting requirements, such as light level, spectrum, and timing, are as diverse as the range of intended uses. 
   Many large commercial lighting applications depend heavily on fluorescent light fixtures driven by a ballast. The type of ballast determines, for example, the power consumption and optimal type of lamp to be used in the fixture. Along with characteristics of the light fixture itself, such as the geometry of the fixture, heat management, and the shapes of the reflectors, the choice of ballast and lamp largely determine the gross light production, expected maintenance interval, and energy consumption of the fixture. Consequently, effective lighting redeployment may require changing the ballast and/or type of lamp used in the fixture. 
   Light fixtures having enhanced features are familiar to consumers. For example, light fixtures can include photodetectors or motion detectors. A light fixture can be continuously dimmable, or it may include two or more separately controllable light circuits for lighting that can be completely off, partially on, or fully on. A lighting redeployment may introduce or change the use of such enhanced features to help conserve electrical power. 
   In a typical prior art light fixture, the ballast and any enhanced features are usually hard wired inside the fixture, and the fixture is hard-wired to building power. So, except for changing the lamp, changes to a typical prior art light fixture may often require services of a relatively highly skilled worker, such as an electrician, and/or replacement of the entire fixture. 
   Thus, it can be costly to remove and replace existing light fixtures, or even to reposition existing light fixtures. It can also be costly to modify or enhance existing light fixtures with different ballast technology or enhanced features to improve their effectiveness or efficiency. Because of these economic barriers, existing light fixtures tend to remain in place even when they are obsolete or lighting requirements change, resulting in wasted electrical power and lost productivity due to ineffective lighting. 
   Thus, what is needed is a modular light fixture architecture specially adapted for flexible, cost-effective, and safe retrofit to existing commercial buildings. What is further needed is a modular light fixture architecture specially adapted for flexible, cost-effective, and safe long term maintenance and redeployment in response to changing lighting requirements and improvements in technology. 
   SUMMARY OF THE INVENTION 
   A first aspect of the invention relates to a modular light fixture having a fixture body with a lampholder mounted to a frame and electrically connected to a modular lampholder harness connector, and a detachable power pack with a ballast electrically connected to a modular ballast output connector, where the modular ballast output connector is adapted to engage the modular lampholder harness connector and provide an electrical connection between the ballast output wiring and the lampholder. 
   In preferred embodiments, the light fixture is at least partially formed of sheet aluminum, and the lampholder holds a fluorescent tube. 
   The modular light fixture may also include a modular power cord assembly connectable to a source of electrical power. The modular connections are preferably polarized, so the connections are engageable in only one orientation. 
   The modular light fixture may also include a reflector formed of a sheet material and mounted on the frame. The reflector is preferably made of sheet aluminum. 
   In another aspect, the invention relates to a method of redeploying lighting in a building, by providing a modular light fixture which has a detachable power pack, mechanically disengaging the detachable power pack from the fixture body, and electrically disengaging the power pack from the fixture body. 
   The method may also include providing a power supply line supplying electrical power to the light fixture. In preferred embodiments, the method includes breaking the supply of electrical power to the light fixture before performing any other steps, and/or restoring power to the light fixture after any other steps are performed. 
   The method may include replacing the entire detachable power pack. Alternatively, the ballast only can be replaced, so that the other components of the detachable power pack can be recycled. 
   The ballast can be replaced with a similar ballast, for repair, or with a ballast having a different ballast factor to adjust the energy consumption or light production from the light fixture. 
   A third aspect of the invention relates to a modular light fixture kit that includes a fixture body and a plurality of detachable ballast assemblies. Such a kit may be kept, for example, by a maintenance department at a particular installation, or it may be carried by a mobile crew on a truck, to allow flexible maintenance or redeployment of lighting with a rapid turnaround time. 
   The plurality of detachable ballast assemblies can be provided in a range of ballast factors, allowing the kit to be used for redeployment or adjustment of lighting in a commercial building. 
   The kit may also include a plurality of power cord assemblies. The plurality of power cord assemblies can be provided with a range of electrical connection types, allowing the kit to be used in a wide range of applications in buildings of varying ages and constructions, and with various sources of electrical power. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded perspective view of a preferred embodiment of a light fixture for use in an apparatus and method according to the invention; 
       FIG. 2  is an assembled perspective view of the light fixture of  FIG. 1 ; 
       FIG. 3  is an end view of the light fixture of  FIG. 1 ; 
       FIG. 4  is a perspective view from below the light fixture of  FIG. 1 , with the detachable power pack separated from the body of the light fixture; 
       FIG. 5  is a perspective view from the side of the light fixture of  FIG. 1 , with the detachable power pack separated from the body of the light fixture; 
       FIGS. 6(   a )- 6 ( c ) are circuit diagrams for light fixtures according to the invention having detachable ballast assemblies with hard-wired, armored whip, and modular connector input power configurations, respectively; 
       FIGS. 7(   a )- 7 ( e ) are circuit diagrams for light fixtures according to the invention having detachable ballast assemblies with normal ballast factor, low ballast factor, high ballast factor, dual switch/high ballast factor, and battery backup/high ballast factor configurations, respectively; 
       FIGS. 8(   a )- 8 ( c ) are perspective views of exemplary modular power supply cords for use according to the invention; 
       FIG. 9  presents plan views of the components of exemplary power input wiring for use according to the invention; 
       FIGS. 10(   a )- 10 ( j ) show exemplary pin assignments for the input power plug and socket connectors in various configurations for use according to the invention; and 
       FIG. 11  is a block diagram of a controller and related components in other embodiments of a light fixture according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-5  show various views of an exemplary fluorescent tube light fixture  10  for use in a method and apparatus according to the invention. As perhaps best shown in  FIGS. 4-5 , the fixture  10  consists generally of a fixture body  66  and a detachable power pack  64 . 
   The fixture body  66  preferably includes a pair of raceways  12  connected by a ballast channel  14  to form a generally I-frame configuration. Each raceway  12  is preferably enclosed with a raceway cover  16 , so that the raceway  12  and raceway cover  16  together form a raceway channel  18 , as shown in  FIGS. 2-3 . 
   Each end of each raceway  12  preferably includes a suspension point  68 , for suspending the light fixture  10  above an area to be illuminated, for example using one or more chains connected between the suspension points  68  and the ceiling. The suspension points  68  are preferably located at or near the corners of the fixture, to ensure that the suspension hardware does not interfere with maintenance of the light fixture including but not limited to replacement of the detachable power pack  64 . 
   One or more light reflectors  22  are secured to each of the raceways  12  such as by rivets, bolts, screws or the like. Six reflectors are shown in the drawings, however, it should be noted that any number of light reflectors can be used with the present invention. Each light reflector  22  can be fabricated from a single piece of material or can be fabricated of individual pieces of material. Any exposed edges of the light reflectors  22  are preferably folded back (hemmed) to reduce sharp edges and improve safety. In the exemplary embodiment of  FIG. 1 , each light reflector  22  defines a reflector channel  24  adapted to house a lamp  30  (not shown in  FIGS. 1-5 ), which is preferably a fluorescent tube lamp. However, a light fixture according to the invention could be used with other types of discharge lamps, such as a metal halide or sodium lamp. 
   The fixture body  66  includes lampholder harnesses  26  housed in the two raceway channels  18  at the opposite ends of the light fixture. Each lampholder harness  26  includes one or more lampholders (sockets)  28  and a lampholder harness connector  32 . Each lampholder  28  preferably extends through a corresponding aperture  34  in a raceway  12  adjacent to the end of a reflector channel  24 . In normal operation, a single fluorescent tube lamp extends between a pair of lampholders  28  at opposite ends of each reflector channel  24 . 
   As perhaps best shown in  FIG. 4 , the detachable power pack  64  of the light fixture  10  preferably includes a ballast channel cover  36 , one or more ballasts  48 , power input wiring  54 , a modular power input connector  56 , ballast output wiring  58 , and a modular ballast output connector  60 . The detachable power pack  64  is preferably detachable from the light fixture body  66  without the use of tools, and without any interference from the suspension hardware. 
   As perhaps best shown in  FIGS. 2 and 5 , the ballast channel cover  36  of the detachable power pack  64  engages the ballast channel  14  of the fixture body  66  to define a ballast chamber  38 . The ballast channel cover  36  preferably includes cover clip portions  41  which mate with corresponding body clip portions  40  to detachably attach the ballast channel cover  36  to the ballast channel  14 . The clips provide an interference or frictional fit that preferably can be separated without the use of tools. However, this is not required, and other means, such as screws, could be used to detachably attach the detachable power pack  64  to the fixture body  66 . 
   The ballast channel cover preferably includes a power line connector aperture  42  adapted to receive a modular power input connector  56 , and a feature connector aperture  43  adapted to receive a feature connector (not shown). The modular power input connector  56  is preferably a polarized modular power input socket  210  configured for the available electrical power supply voltage and configuration, as discussed in more detail below in reference to  FIGS. 9-10 . However, this is not required, and other methods can be used to supply electrical power to the fixture, as discussed in more detail below in reference to  FIGS. 6(   a )- 6 ( c ). 
   The exemplary detachable power pack  64  of the light fixture  10  includes two ballasts  48 , for example a model 49776 electronic ballast available from GE Lighting of Cleveland, Ohio. However, this is not required, and other makes and models of ballasts can be employed with the present invention. Further, while the exemplary light fixture  10  includes two ballasts  48 , a greater or lesser number of ballasts  48  can be used. 
   Each ballast  48  has a first (input) end  50  and a second (output) end  52 . Power input wiring  54  electrically connects the modular power input connector  56  to the first end  50  of each ballast  48 . As discussed in more detail below in reference to  FIGS. 9-10 , the modular power input connector  56  mates with a modular power cord assembly  180  supplying electrical power. The modular power cord assembly  180  is preferably quickly and easily disconnected from the modular power input connector  56  without the use of tools, in order to verifiably and positively remove electrical power from the fixture to reduce the risk of electrical shock during maintenance. 
   Ballast output wiring  58  electrically connects the second (output) end  52  of each ballast  48  to a modular ballast output connector  60 . The modular ballast output connector  60  mates with a corresponding lampholder harness connector  32 . The modular ballast output connector  60  is preferably quickly and easily disconnected from the lampholder harness connector  32  without the use of tools. 
   Each ballast  48  is fastened to the ballast channel cover  36 , for example using threaded fasteners to engage mounting ears  62  on each ballast  48  through holes in the ballast channel cover  36 . However, threaded fasteners are not required and other means can be utilized to fasten each ballast  48  to the ballast channel cover  36 , such as adhesives or interference mounting techniques. 
   When the ballast  48  is secured to the ballast channel cover  36 , the modular power input connector  56  preferably extends through the aperture  42  for connection to a modular power cord assembly  180  (not shown in  FIGS. 1-5 ). The ballast channel cover  36  is preferably positioned above the ballast  48 , with good thermal contact between the ballast  48  and ballast channel cover  36 , so waste heat generated by the ballast  48  conducts upwardly to the ballast channel cover  36 . The ballast channel cover  36  is preferably positioned at the top of the fixture  10 , and exposed to air circulation so waste heat from the ballast can radiate away from the light fixture. 
   In the embodiment of  FIG. 1 , when the detachable power pack is attached to the fixture body  66 , each ballast  48  is housed in the ballast chamber  38 , and oriented so that the modular ballast output connectors  60  of the power pack  46  can mate with the modular lampholder harness connectors  32  of the lampholder harnesses  26 . 
   When the modular ballast output connectors  60  mate with the modular lampholder harness connectors  32 , the ballasts  48  are electrically connected to deliver power to the lampholder harnesses  26 , the lampholders  28 , and the lamps  30  (not shown in  FIGS. 1-5 ). Suitable mating modular ballast output connectors  60  and modular lampholder harness connectors  32  are a male and female connector pair available as models 231-604 and 231-104/02600 from Wago Corp. of Germantown, Wis. However, this is not required and other types, makes and models of mating modular connectors can be used with the present invention. 
     FIGS. 4 and 5  are perspective views of the light fixture of  FIG. 1 , with the detachable power pack  64  separated from the fixture body  66  of the light fixture  10 . The following discussion of exemplary methods for modifying or servicing a light fixture according to another aspect of the invention is by way of explanation, and is not necessarily a limitation on the scope of the invention as defined by the claims. Replacing the detachable power pack  64  in a light fixture  10 , for example to change the ballast characteristics in response to changing light requirements or to service a failed ballast, is straightforward and does not necessarily require a high level of skill or the use of tools. 
   First, the modular power cord  180  is disconnected from the modular power input connector  56 , thereby positively and verifiably cutting off electrical power from the light fixture  10  to improve the safety of the procedure. Second, the old detachable power pack  64  is separated from the body  66  of the light fixture by uncoupling the cover clip portions  41  from the body clip portions  40 , and by disconnecting the modular ballast output connectors  60  from their corresponding lampholder harness connectors  32 . The old power pack  64  can then be set aside for eventual disposal or repair. 
   When reassembling the light fixture  10  with a new or replacement power pack  64 , the reverse of the above procedure is performed. First, the ballast output connectors  60  on the new power pack  64  are mated with their corresponding lampholder harness connectors  32 . Next, the new power pack  64  is detachably fastened to the body  66  of the light fixture by coupling the cover clip portions  41  with the body clip portions  40 . Finally, modular power cord  180  is reconnected to the modular power input connector  56  to restore power to the light fixture  10  for normal operation. 
   It should be noted that the present invention can be employed with other fixtures, and the invention is not limited to the light fixture shown and described herein. For example, another fluorescent tube light fixture embodiment in which the present invention can be employed is that shown and described in U.S. Pat. No. 6,585,396, which is hereby incorporated by reference. 
     FIGS. 6(   a )- 6 ( c ) are circuit diagrams for light fixtures according to the invention having detachable ballast assemblies with alternative input power configurations. A variety of alternative input power configurations are preferably provided to allow a light fixture according to the invention to be used with a variety of available power sources. These alternative input power configurations can be classified generally into “hard wire” configurations, and “modular” configurations. A light fixture according to the invention can include either input power configuration. 
     FIGS. 6(   a ) and  6 ( b ) show examples of hard wire input power configurations. The detachable power pack  64  of  FIG. 6(   a ) includes a hard wire power supply connector  152 . The hard wire power supply connector  152  represents a connection which is hard wired directly to a branch circuit in the building, for example by an electrician. The detachable power pack  64  of  FIG. 6(   b ) includes one type of hard wire power supply connector, an armored whip power supply line  154 . 
   The detachable power pack  64  of  FIG. 6(   c ) includes a modular wiring system power supply line  156 . An alternative, “daisy chain” modular wiring system power supply line is described, for example, in U.S. Pat. No. 6,746,274, the contents of which are incorporated by reference. 
   While the exemplary circuit diagrams of  FIGS. 6(   a )- 6 ( c ), and the disclosure of U.S. Pat. No. 6,746,274 show specific combinations of input power configurations with particular types of ballasts, these specific combinations are not required. It should be understood that any of these input power configurations can be used with a light fixture according to the invention, as appropriate for the environment in which the light fixture is to be installed. It should also be understood that any of these power supply configurations can be used with any type of ballast, not just the particular types of ballasts shown in  FIGS. 6(   a )- 6 ( c ). 
     FIGS. 7(   a )- 7 ( e ) are circuit diagrams for light fixtures according to the invention having detachable ballast assemblies with alternative ballast configurations. Advantageously, such a variety of alternative ballast configurations can allow a light fixture according to the invention to provide a wider variety of light levels at varying power consumption levels. 
   The detachable power pack of  FIG. 7(   a ) is a high ballast factor detachable power pack  160  that includes a high ballast factor ballast  162 . 
   The detachable power pack of  FIG. 7(   b ) is a normal ballast factor detachable power pack  164  that includes a normal ballast factor ballast  166 . 
   The detachable power pack of  FIG. 7(   c ) is a low ballast factor detachable power pack  168  that includes a low ballast factor ballast  170 . 
   The detachable power pack of  FIG. 7(   d ) is a dual switched detachable power pack  172  that includes two high ballast factor ballasts  162  that receive independent power on separate lines from the modular power input connector  56 . 
   The detachable power pack of  FIG. 7(   e ) is a battery backup detachable power pack  174  that includes battery backup circuitry  176 , a battery backup ballast  178 , and two high ballast factor ballasts  162 . The battery backup ballast  178  can supply lighting in the event of a failure of the main electrical supply, for example in the case of a natural disaster or fire. 
     FIG. 8(   a ) shows a modular power cord assembly  180  having a first end that terminates in a polarized modular power supply plug, and a second end that terminates in a conventional power plug  182 . 
   The modular power cord assembly  180  includes a suitable length of conventional insulated power cord  181  with 3 or 4 insulated conductors surrounded by an insulated jacket. The power cord  181  can be any standard electrical power cord having suitable power handling and other specifications, for example 18 gauge 3-conductor or 18 gauge 4-conductor power cord can be used. In a preferred embodiment of the invention, a variety of cord lengths, for example from 3′ to 35′ in length, are kept in stock, allowing the appropriate cord length to be chosen from stock at the time the light fixture is installed, without requiring any delay for custom manufacturing of a modular power supply cord having the appropriate length. 
   The polarized modular power supply plug is preferably a 6-pin “Mate-N-Lock” plug connector of the type sold by the AMP division of Tyco Electronics of Harrisburg, Pa. However, this is not required and other types, makes and models of modular power supply connectors can be used with the present invention. The polarized modular power supply plug preferably includes strain relief, for example two strain relief pieces  184  and a plastic insert  185  (such as AMP P/N 640715-1), and a plug body  188 . The strain relief  184 , plastic insert  185 , and plug body  188  can be held together with screws  186 , such as #6×⅝″ sheet metal screws. 
   In a preferred embodiment, the plug body  188  has six positions for holding electrical pins, although a plug body having a greater or lesser number of pin positions could be used. A short portion of the insulation is stripped from the end of each conductor in the electrical cord  181 , and an electrical pin is electrically and mechanically connected to the stripped portion. The electrical pins and attached conductors are then inserted into specific pin positions in the plug body  188  to form a polarized modular power supply plug, as discussed in more detail below in reference to  FIGS. 10(   a )- 10 ( j ). 
   The “extra long” electrical pin  190  used for the green (safety ground) line is preferably slightly longer than the “standard length” electrical pins  192  used for the black (power supply or “hot”), white (power return or neutral), and red (switched power) lines. This helps ensure that the safety ground connection is made first and broken last when the plug  158  is inserted into or removed from its corresponding socket. A suitable extra long electrical pin  190  for the safety ground would be AMP PN 350669, and a suitable standard length electrical pin  192  for the other lines would be AMP PN 350547-1. 
   The conventional power plug  182  can be any standard electrical plug configuration, such as a NEMA 5, NEMA L5, NEMA L7, NEMA 6, or NEMA L6 plug. In a preferred embodiment of the invention, a variety of plug configurations are kept in stock, allowing the appropriate plug configuration to be chosen from stock at the time the light fixture is installed, without requiring any delay for custom manufacturing of a modular power supply cord having the appropriate plug configuration. 
     FIG. 8(   b ) shows an alternative modular power cord assembly  198  having a first end that terminates in a polarized modular power supply plug, and a second end that terminates in stripped conductors  196 , preferably about ⅜″ in length. The modular power cord assembly  198  is similar in construction to the modular power cord assembly  180 , except that the modular power cord assembly  198  terminates in stripped conductors  196  that can be used, for example, to hardwire the fixture to building power, and the modular power cord assembly  198  is wired for “universal” application.  FIG. 8(   c ) shows a “dual switch” modular power cord assembly  199  that is otherwise similar in construction to the modular power cord assembly  198 . 
     FIG. 9  shows exemplary power input wiring  54  for a detachable power pack in a light fixture according to the invention. The exemplary power input wiring  54  includes at least 3 insulated conductors, including a safety ground (green) wire  200 , a power return (white) wire  202 , and a power supply (black) wire  204 . Depending on the application, the power input wiring  54  may also include a switched power (red) wire  206 , and a second power supply (black) wire  204 . Each conductor is made of a suitable length of insulated wire, for example UL 1015 18 AWG wire rated for 105° C. and 600V can be used. 
   One end of the power input wiring terminates in a modular power input connector  56 , which is preferably a polarized modular power input socket  210  such as a 6-pin “Mate-N-Lock” socket connector of the type sold by the AMP division of Tyco Electronics of Harrisburg, Pa. 
   In a preferred embodiment, the polarized modular power input socket  210  includes a socket body  208  having six positions for holding single conductor sockets, although a socket having a greater or lesser number of single conductor socket positions could be used. A short portion of the insulation is stripped from the end of each conductor, and a single conductor socket  193 , for example AMP PN 350550-1, is electrically and mechanically connected to the stripped portion, for example by crimping and/or soldering. The single conductor socket  193  and attached conductor are then inserted into a specific single conductor socket position in the socket body  208  to form the polarized modular power input socket  210 , as discussed in more detail below in reference to  FIGS. 10(   a )- 10 ( j ). 
     FIGS. 10(   a )- 10 ( j ) show exemplary pin assignments for the input power plug and socket connectors in various configurations of a detachable power pack for use in a light fixture according to the invention. However, these pin assignments are not required, and other pin assignments could be used.  FIGS. 10(   a ) and  10 ( b ) illustrate a convention for numbering the pins ( 1 - 6 ) in the input power plug and socket connectors. 
     FIGS. 10(   c ) and  10 ( d ) illustrate an exemplary 120V power supply configuration. The exemplary 120V power supply configuration uses a 120V modular power supply plug  212  along with a 120V modular power input socket  220 . The plug  212  and socket  220  each include at least a safety ground (green) wire  200 , a power return (white) wire  202 , and a power supply (black) wire  204  located at specific positions in plug head  188  and socket head  208 , respectively. When used in a 120V dual-switched configuration, the plug  212  and socket  220  also include a second power (red) wire  206 . 
     FIGS. 10(   e ) and  10 ( f ) illustrate an exemplary 277V power supply configuration. The exemplary 277V power supply configuration uses a 277V modular power supply plug  214  along with a 277V modular power input socket  222 . Like the 120V plug  212  and 120V socket  220 , the 277V plug  214  and the 277V socket  222  each include at least a safety ground (green) wire  200 , a power return (white) wire  202 , and a power supply (black) wire  204 . The safety ground (green) wire  200  and the power return (white) wire  202  of the 277V configuration are at the same pin positions as in the 120V configuration, however the power supply (black) wire  204  is at a different pin position. When used in a 277V dual-switched configuration, the plug  214  and socket  222  also include a second or switched power (red) wire  206 . 
     FIGS. 10(   g ) and  10 ( h ) illustrate an exemplary 347/480 V power supply configuration. The exemplary 347/480V power supply configuration uses a 347/480V modular power supply plug  216  along with a 347/480V modular power input socket  224 . Like the 120V and 277V configurations, the 347/480V plug  216  and the 347/480V socket  224  each include at least a safety ground (green) wire  200 , a power return (white) wire  202 , and a power supply (black) wire  204 . The safety ground (green) wire  200  and the power return (white) wire  202  of the 277V configuration are at the same pin positions as in the 120V and 277V configurations, however the power supply (black) wire  204  is at a different pin position. When used in a 347/480V dual-switched configuration, the plug  216  and socket  224  also include a second or switched power (red) wire  206 . 
     FIGS. 10(   i ) and  10 ( j ) illustrate an exemplary “UNV” or “universal” power supply configuration. The exemplary “UNV” or “universal” power supply configuration uses a UNV modular power supply plug  218  along with a UNV modular power input socket  226 . A light fixture wired with the UNV power supply socket configuration can be used with either a 120V supply cord or a 277V supply cord. A light fixture wired with the 120 v power supply socket configuration can be used with either a 120V supply cord or a UNV supply cord. A light fixture wired with the 277 v power supply socket configuration can be used with either a 277V supply cord or a UNV supply cord. 
   The UNV plug  218  and the UNV socket  226  each include at least a safety ground (green) wire  200  and a power return (white) wire  202 , in the same pin and socket positions as the 120V, 277V, and 347/480V configurations. However, the UNV plug  218  and the UNV socket  226  each include two power supply (black) wires  204 , one power supply (black) wire  204  at each of the two pin positions used for the power supply (black) wire  204  in the 120V and 277V configurations. When used in a 120V or 277V dual-switched configuration, the plug  218  and socket  226  also include a second or switched power (red) wire  206 . 
   As shown in  FIG. 11 , a modular light fixture according to the invention can include a controller  80 , for example a microprocessor or microcontroller of the types known in the art. The controller  80  may include suitable non-volatile program memory, for example read-only memory (ROM) such as an electrically programmable read only memory (EPROM or EEPROM). The controller  80  may also include suitable random access memory, for storage of dynamic state variables such as environmental signals and current day/time. 
   The light fixture preferably includes a power source  82 , such as an electrical connector which is connected to line voltage during normal operation, able to deliver electrical power to the controller  80  through a controller power supply line  84 . 
   The light fixture according to the invention preferably includes a plurality of independently controllable lamp circuits. For example, the block diagram of  FIG. 6  shows a light fixture with a first independently controllable lamp circuit that includes lamp one  102  and a second independently controllable lamp circuit that include lamp two  106 . However, this is not required and a single lamp circuit can be used. 
   Each independently controllable lamp circuit preferably includes a ballast and an optional switch. For example, lamp circuit for lamp one  102  includes a switch one  86  that receives electrical power from the power source  82  on a power supply line  88 . The switch one  86  delivers electrical power to a ballast one  94  on a switched power supply line  96 , and the ballast one  94  provides power to the lamp one  102  on a ballasted power supply line  104 . 
   The lamp circuit for lamp two  106  preferably includes a corresponding switch two  90  that receives electrical power from the power source  82  on a power supply line  92 . The switch two  90  delivers electrical power to a ballast two  98  on a switched power supply line  100 , and the ballast two  98  provides power to the lamp two  106  on a ballasted power supply line  108 . 
   Each switch in a lamp circuit, such as switch one  86  and switch two  90 , is preferably adapted to be placed into either an open condition (where the switch is an electrical open circuit through which no current flows) or in a closed condition (where the switch is an electrical closed circuit through which current can flow). To maximize efficiency, a mechanical relay switch, instead of a solid state switch, can be used so that essentially no trickle current passes through the switch when the switch is in an open condition. 
   The open or closed condition of each switch is preferably independently controllable by the controller  80 . For example, the controller  80  can be connected to switch one  86  by a switch control line  110 , whereby the controller can place switch one  86  into either a closed or an open condition. Similarly, the controller  80  can be connected to switch two  90  by a switch control line  112 , whereby the controller can place switch two  90  into either a closed or an open condition. 
   Each ballast in a lamp circuit, such as ballast one  94  and ballast two  98 , is preferably dimmable to allow the light output from its lamp to be adjusted by the controller  80 . For example, the controller  80  can be connected to ballast one  94  by a ballast control line  114 , so the controller can adjust the power output of ballast one  94  to adjust the light output from lamp one  102 . Similarly, the controller  80  can be connected to ballast two  98  by a ballast control line  116 , so the controller can adjust the power output of ballast two  98  to adjust the light output from lamp two  106 . 
   The light fixture can include one or more sensors to provide information about the environment in which the light fixture operates. For example, the fixture can include an ambient light sensor  120  providing an ambient light signal to the controller  80  on an ambient light signal line  122 . Using the ambient light signal, the controller  80  can adjust the light output from the fixture, for example to reduce the artificial light produced by the fixture on a sunny day when ambient light provides adequate illumination, or to increase the artificial light produced by the fixture on a cloudy day when ambient light is inadequate. The sensor can be mounted directly on the light fixture, or it can be mounted elsewhere, such as part of the incoming power cord. For example, in U.S. Pat. No. 6,746,274, the contents of which are incorporated herein by reference, teaches a motion detector built into a modular power cord. 
   The fixture can include a motion sensor  124  providing a motion signal to the controller  80  on an motion signal line  126 . Using the motion signal, the controller  80  can turn on the fixture when the motion signal indicates the presence of motion near the fixture. Similarly, the controller  80  can turn off the fixture when the motion signal indicates the absence of any motion near the fixture. 
   The fixture can include a temperature sensor  128  providing a temperature signal to the controller  80  on an temperature signal line  130 . The temperature signal can indicate, for example, the air temperature in the vicinity of the fixture. Alternatively, the temperature signal can indicate the temperature of the ballast or other components of the light fixture, so that any temperature rise resulting from abnormal operation or impending failure can be promptly detected to avoid ongoing inefficiency, the possibility of a fire, or a catastrophic failure of the ballast. 
   The fixture can include a proximity sensor  132  providing a proximity signal to the controller  80  on a proximity signal line  134 . Using the proximity signal, the controller  80  can turn on the fixture on or off when the proximity signal indicates the presence or absence of a person or other object near the fixture. 
   The fixture can also include a communicator  136  to allow communication between the controller  80  and an external system (not shown). The communicator can be, for example, of the type commonly known as X-10. For example, the communicator  136  can be connected to the controller  80  for bidirectional communication on a communicator signal line  138 . With bidirectional communication, the controller  80  can receive a command from an external system, for example to dim, turn on, or turn off a lamp, and the controller  80  can acknowledge back to the external system whether or not the command has been performed successfully. Similarly, the external system could request the current temperature of the ballast of the fixture, and the controller  80  could reply with that temperature. 
   However, bidirectional communication is not required and one-way communication could also be used. With one-way communication, the fixture could simply receive and execute commands from an external system without providing any confirmation back to the external system as to whether the command was executed successfully or not. Similarly, the fixture could periodically and automatically transmit its status information to an external system, without requiring any request from the external system for the status information. 
   The fixture can include a smoke detector  140  providing a smoke detector signal to the controller  80  on a smoke detector signal line  142 . Using the smoke detector signal, the controller  80  can provide a local alarm, for example with a flashing light or a siren, whenever the smoke detector signal indicates the presence of a fire or smoke. Similarly, the controller  80  can provide the smoke detector signal to an external system, for example through the communicator  136 , to a security office or fire department. 
   The fixture can include a camera and/or microphone  144  providing a camera/microphone signal to the controller  80  on a camera/microphone signal line  146 . The controller  80  can provide the camera/microphone signal to an external system, for example through the communicator  136 , to a security office, time-lapse recorder, or supervisory station. 
   The fixture can include an audio output device  148 , for example a speaker. The controller  80  can drive the audio output device  148 , for example with an audio signal on an audio signal line  150 , to provide an alarm, paging, music, or public address message to persons in the vicinity of the fixture. The alarm, paging, music, or public address message can be received by the controller  80  via the communicator  136  from an external system, although this is not required and the alarm, paging, music, or public address message may be internally generated. 
   Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limited. 
   The use of “including,” “comprising,” “supporting,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected,” “supported,” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting, supporting, and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. 
   Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and other alternative mechanical configurations are possible. 
   It is important to note that the construction and arrangement of the elements of the modular light fixture and other structures shown in the exemplary embodiments discussed herein are illustrative only. Those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, materials, transparency, color, orientation, etc.) without materially departing from the novel teachings and advantages of the invention. 
   Further, while the exemplary application of the device is in the field of fluorescent lighting, the invention has a much wider applicability. 
   The particular materials used to construct the exemplary embodiments are also illustrative. For example, although the reflectors in the exemplary embodiment are preferably made of aluminum, other materials having suitable properties could be used. All such modifications, to materials or otherwise, are intended to be included within the scope of the present invention as defined in the appended claims. 
   The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and/or omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present invention as expressed in the appended claims. 
   The components of the invention may be mounted to each other in a variety of ways as known to those skilled in the art. As used in this disclosure and in the claims, the terms mount and attach include embed, glue, join, unite, connect, associate, hang, hold, affix, fasten, bind, paste, secure, bolt, screw, rivet, solder, weld, and other like terms. The term cover includes envelop, overlay, and other like terms. 
   It is understood that the invention is not confined to the embodiments set forth herein as illustrative, but embraces all such forms thereof that come within the scope of the following claims.