Patent Publication Number: US-11647572-B2

Title: Lighting systems incorporating connections for signal and power transmission

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/911,586, filed Jun. 25, 2020, which is a continuation of U.S. patent application Ser. No. 16/683,514, filed Nov. 14, 2019, which is a continuation of U.S. patent application Ser. No. 16/420,299, filed May 23, 2019, which is a continuation of U.S. patent application Ser. No. 15/446,494, filed Mar. 1, 2017, which claims the benefit of and priority to U.S. Provisional Patent Application No. 62/302,434, filed Mar. 2, 2016, the entire disclosure of each of which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     In various embodiments, the present invention generally relates to electronic devices, and more specifically to array-based electronic devices. 
     BACKGROUND 
     Solid-state lighting is an attractive alternative to incandescent and fluorescent lighting systems for backlighting of translucent panels or materials and signs because of its relatively higher efficiency, robustness, and long life. A number of backlighting systems based on light-emitting diodes (LEDs) have been proposed, but these generally suffer from one or more deficiencies. It is often desirable to have the thickness of the panel or sign as small as possible, for example to fit within a restricted space, to provide a thin visual perspective, or to reduce cost. Various LED systems generally include LEDs that are operated at relatively high current, resulting in very bright light sources that must be mixed and diffused to provide even and low-glare illumination of the panel or sign. For systems having LEDs spaced several inches or more apart, this may result in an undesirably large spacing between the LEDs and the diffuser. The diffuser reduces the efficiency, and as the LEDs become brighter, more diffusion, with concomitant decreases in efficiency, is required to achieve a homogeneous luminance across the panel or sign. Furthermore, such systems often require relatively large heat sinks or thermal management systems, which also take up space and may require suitable ventilation, for example passive ventilation or active ventilation such as fans, to prevent deleterious heat buildup. These issues typically lead to undesirably large, thick, and potentially, complicated lighting systems. 
     In addition, many applications for backlighting and illuminated panels and signs require custom sizing to fit in a particular location. Systems having relatively few high-brightness LEDs on rigid circuit boards or systems employing edge-lit panels may be difficult to use cost effectively in a wide range of installations, e.g., installations requiring size customization while maintaining high illumination uniformity and high efficiency. 
     Accordingly, there is a need for solutions that provide lighting systems having a thin form factor with improved uniformity, high efficiency, and which are simple to install. 
     SUMMARY 
     Embodiments of the present invention relate to illumination systems based on flexible light sheets and that incorporate additional functionality that enables various different mechanical mounting and electrical and/or mechanical joining techniques. For example, illumination systems in accordance with embodiments of the invention incorporate rigid or semi-rigid mounting frames that may also provide electrical connectivity. In various embodiments, the illumination systems are modular and feature connection mechanisms (e.g., snap connectors) that mechanically and electrically interconnect individual light panels or light sheets together and/or to power-distribution systems and/or to mounting rails. 
     Additional details of lighting systems in accordance with embodiments of the present invention appear within U.S. patent application Ser. No. 13/799,807, filed Mar. 13, 2013 (the &#39;807 application), U.S. patent application Ser. No. 13/748,864, filed Jan. 24, 2013 (the &#39;864 application), and U.S. patent application Ser. No. 14/699,149, filed Apr. 29, 2015 (the &#39;149 application), the entire disclosure of each of which is incorporated by reference herein. 
     In an aspect, embodiments of the invention feature a lighting system that includes, consists essentially of, or consists of a first light panel, a second light panel, and a power distribution bus. The first light panel includes, consists essentially of, or consists of a first substrate, first and second spaced-apart power conductors disposed on the first substrate, a plurality of first light-emitting elements disposed on the first substrate and electrically connected to the first and second power conductors, a first connector electrically connected to the first power conductor, a second connector electrically connected to the second power conductor, and a third connector. The third connector may not be electrically connected to the first and/or second power conductors. The second light panel includes, consists essentially of, or consists of a second substrate, third and fourth spaced-apart power conductors disposed on the second substrate, a control conductor disposed on the second substrate, a plurality of second light-emitting elements disposed on the second substrate and electrically connected to the third and fourth power conductors, a fourth connector electrically connected to the third power conductor, a fifth connector electrically connected to the fourth power conductor, a sixth connector electrically connected to the third power conductor, a seventh connector electrically connected to the fourth power conductor, an eighth connector electrically connected to the control conductor, a ninth connector electrically connected to the control conductor, and a control connector electrically connected to the control conductor. The control conductor may be separate and/or spaced apart from the third and/or fourth power conductors. The power distribution bus includes, consists essentially of, or consists of first and second power distribution lines, a control distribution line, a tenth connector electrically connected to the first power distribution line, an eleventh connector electrically connected to the second power distribution line, and a twelfth connector electrically connected to the control distribution line. The control distribution line may be separate and/or spaced apart from the first and/or second power distribution lines. The first connector is configured for connection to the fourth connector, thereby electrically, coupling the first power conductor to the third power conductor. The second connector is configured for connection to the fifth connector, thereby electrically coupling the second power conductor to the fourth power conductor. The tenth connector is configured for connection to the sixth connector, thereby electrically coupling the third power conductor to the first power distribution line. The eleventh connector is configured for connection to the seventh connector, thereby electrically coupling the fourth power conductor to the second power distribution line. The third connector is configured for connection to the eighth control connector, thereby electrically coupling the first control connector to the control conductor. The ninth connector is configured for connection to the twelfth connector, thereby electrically coupling the control conductor to the control distribution line. The control connector is configured for at receipt and/or transmission of control and/or communication signals along the control conductor. 
     Embodiments of the invention may include one or more of the following in any of a variety of combinations. Connections between connectors may be direct connections (i.e., the connectors make a direct physical connection) or may be connections made via a jumper or other intermediate element (i.e., the connectors are electrically connected to each other via the jumper or other intermediate element but are not in direct physical contact). The control connector may be disposed on or over the second substrate. The control connector may be separate and spaced apart from the eighth and/or ninth connectors. The control connector may include, consist essentially of, or consist of one or more vertical connectors. The control connector may include, consist essentially of, or consist of one or more snap connectors. The control connector may include, consist essentially of, or consist of a wireless receiver and/or a wireless transmitter. The lighting system may include a controller configured to control an emission characteristic of at least a portion of the second light panel in response to control signals received via the control connector. The controller may be configured to control an emission characteristic of at least a portion of the first light panel. The emission characteristic may include, consist essentially of, or consist of a light intensity, an emission color, a spectral power distribution, and/or a spatial light distribution pattern. The second light panel may include a thirteenth connector electrically connected to the third power conductor and a fourteenth connector electrically connected to the fourth power conductor. The thirteenth and fourteenth connectors may be configured to provide power to an electronic device from the first and second power distribution lines when (a) the tenth connector is connected to the sixth connector and/or (b) the eleventh connector is connected to the seventh connector. The thirteenth connector may include, consist essentially of, or consist of one or more vertical connectors. The thirteenth connector may include, consist essentially of, or consist of one or more snap connectors. The fourteenth connector may include, consist essentially of, or consist of one or more vertical connectors. The fourteenth connector may include, consist essentially of, or consist of one or more snap connectors. The thirteenth connector may be disposed on or over the second substrate. The thirteenth connector may be separate and spaced apart from the fourth and/or sixth connectors. The fourteenth connector may be disposed on or over the second substrate. The fourteenth connector may be separate and spaced apart from the fifth and/or seventh connectors. The lighting system may include an electronic device electrically coupled to the thirteenth and fourteenth connectors. The electronic device may include, consist essentially of, or consist of a sensor, a receiver, a transmitter, a transceiver, a camera, a speaker, and/or a microphone. The first light panel may define one or more apertures (i.e., holes) therethrough. The second light panel may define one or more apertures (i.e., holes) therethrough. An electronic device may be electrically coupled to the control connector. The electronic device may include, consist essentially of, or consist of a sensor, a receiver, a transmitter, a transceiver, a camera, a speaker, and/or a microphone. The lighting system may include a first jumper and/or a second jumper. The first jumper may include, consist essentially of, or consist of (i) a first jumper connector configured for connection to the sixth connector and (ii) a second jumper connector configured for connection to the tenth connector. The second jumper may include, consist essentially of, or consist of (i) a third jumper connector configured for connection to the seventh connector and (ii) a fourth juniper connector configured for connection to the eleventh connector. The first jumper may include, consist essentially of, or consist of (i) a first jumper connector configured for connection to the ninth connector and (ii) a second jumper connector configured for connection to the twelfth connector. 
     In another aspect, embodiments of the invention feature a lighting system that includes, consists essentially of, or consists of a first light panel, a second light panel, and a power distribution bus. The first light panel includes, consists essentially of, or consists of a first substrate, first and second spaced-apart power conductors disposed on the first substrate, a plurality of first light-emitting elements disposed on the first substrate and electrically connected to the first and second power conductors, a first connector electrically connected to the first power conductor, and a second connector electrically connected to the second power conductor. The second light panel includes, consists essentially of, or consists of a second substrate, third and fourth spaced-apart power conductors disposed on the second substrate, a plurality of second light-emitting elements disposed on the second substrate and electrically connected to the third and fourth power conductors, a third connector electrically connected to the third power conductor, a fourth connector electrically connected to the fourth power conductor, a fifth connector electrically connected to the third power conductor, a sixth connector electrically connected to the fourth power conductor, a seventh connector electrically connected to the third power conductor, and an eighth connector electrically connected to the fourth power conductor. The power distribution bus includes, consists essentially of, or consists of first and second power distribution lines, a ninth connector electrically connected to the first power distribution line, and a tenth connector electrically connected to the second power distribution line. The first connector is configured for connection to the third connector, thereby electrically coupling the first power conductor to the third power conductor. The second connector is configured for connection to the fourth connector, thereby electrically coupling the second power conductor to the fourth power conductor. The ninth connector is configured for connection to the fifth connector, thereby electrically coupling the third power conductor to the first power distribution line. The tenth connector is configured for connection to the sixth connector, thereby electrically coupling the fourth power conductor to the second power distribution line. The seventh and eighth connectors are configured to provide power to an electronic device from the first and second power distribution lines when (a) the ninth connector is connected to the fifth connector and (b) the tenth connector is connected to the sixth connector. 
     Embodiments of the invention may include one or more of the following in any of a variety of combinations. Connections between connectors may be direct connections (i.e., the connectors make a direct physical connection) or may be connections made via a jumper or other intermediate element (i.e., the connectors are electrically connected to each other via the juniper or other intermediate element but are not in direct physical contact). The seventh and/or eighth connector may include, consist essentially of, or consist of one or more vertical connectors. The seventh and/or eighth connector may include, consist essentially of, or consist of one or more snap connectors. The seventh connector may be disposed on or over the second substrate. The seventh connector may be spaced apart from the third and fifth connectors. The eighth connector may be disposed on or over the second substrate. The eighth connector may be spaced apart from the fourth and sixth connectors. The lighting system may include an electronic device electrically coupled to the seventh and eighth connectors. The electronic device may include, consist essentially of, or consist of a sensor, a receiver, a transmitter, a transceiver, a camera, a speaker, and/or a microphone. The first light panel may define one or more apertures (i.e., holes) therethrough. The second light panel may define one or more apertures (i.e., holes) therethrough. The lighting system may include a first jumper and/or a second jumper. The first jumper may include, consist essentially of, or consist of (i) a first jumper connector configured for connection to the fifth connector and (ii) a second jumper connector configured for connection to the ninth connector. The second jumper may include, consist essentially of, or consist of (i) a third jumper connector configured for connection to the sixth connector and (ii) a fourth jumper connector configured for connection to the tenth connector. 
     In yet another aspect, embodiments of the invention feature a lighting system that includes, consists essentially of, or consists of a first light panel and a second light panel. The first light panel includes, consists essentially of, or consists of a first substrate, first and second spaced-apart power conductors disposed on the first substrate, a plurality of first light-emitting elements disposed on the first substrate and electrically connected to the first and second power conductors, a first connector electrically connected to the first power conductor, and a second connector electrically connected to the second power conductor. The second light panel includes, consists essentially of, or consists of a second substrate, first and second tabs extending from (and/or defined by) the second substrate, third and fourth spaced-apart power conductors disposed on the second substrate, a plurality of second light-emitting elements disposed on the second substrate and electrically connected to the third and fourth power conductors, a third connector electrically connected to the third power conductor and disposed on the first tab, and a fourth connector electrically connected to the fourth power conductor and disposed on the second tab. The first tab and/or the second tab may be planar and/or elongated. The first tab and/or the second tab may be flexible. The first connector is configured for connection to the third connector, thereby electrically coupling the first power conductor to the third power conductor. The second connector is configured for connection to the fourth connector, thereby electrically coupling the second power conductor to the fourth power conductor. The first tab may include one or more first strain-relief features that, e.g., increase compliance and/or flexibility of the lighting system when the first connector is connected to the third connector. The second tab may include one or more second strain-relief features that, e.g., increase compliance and/or flexibility of the lighting system when the second connector is connected to the fourth connector. 
     Embodiments of the invention may include one or more of the following in any of a variety of combinations. Connections between connectors may be direct connections (i.e., the connectors make a direct physical connection) or may be connections made via a jumper or other intermediate element (i.e., the connectors are electrically connected to each other via the jumper or other intermediate element but are not in direct physical contact). One or more of the first strain-relief features may include, consist essentially of, or consist of a cut (e.g., a slit) penetrating through only a portion of a dimension (e.g., width) of the first tab. One or more of the second strain-relief features may include, consist essentially of, or consist of a cut (e.g., a slit) penetrating through only a portion of a dimension (e.g., width) of the second tab. The one or more first strain-relief features may include, consist essentially of, or consist of two first strain-relief features extending inward into the first tab from opposite sides thereof. Each of the first strain-relief features may include, consist essentially of, or consist of a cut penetrating through only a portion of a dimension (e.g., width) of the first tab. The one or more second strain-relief features may include, consist essentially of, or consist of two second strain-relief features extending inward into the second tab from opposite sides thereof. Each of the second strain-relief features may include, consist essentially of, or consist of a cut penetrating through only a portion of a dimension (e.g., width) of the second tab. One or more of the first strain-relief features may include, consist essentially of, or consist of an elongated cut having a termination feature disposed at an end thereof. A dimension (e.g., a width anchor diameter) of the termination feature may be greater than a dimension (e.g., width) of the cut. One or more of the second strain-relief features may include, consist essentially of, or consist of an elongated cut having a termination feature disposed at an end thereof. A dimension (e.g., a width and/or diameter) of the termination feature may be greater than a dimension (e.g., width) of the cut. The first tab may include, consist essentially of, or consist of two or more layers of a material of the second substrate. At least one of the layers may be folded over at least another one of the layers (e.g., along one or more fold lines) to define at least a portion of the first tab. The third connector may extend through the two or more layers of the material of the second substrate. At least one of the first strain-relief features may extend only through one of the layers of the material of the second substrate. At least one of the first strain-relief features may not extend through all of the layers of the material of the second substrate. The second tab may include, consist essentially of, or consist of two or more layers of a material of the second substrate. At least one of the layers may be folded over at least another one of the layers (e.g., along one or more fold lines) to define at least a portion of the second tab. The fourth connector may extend through the two or more layers of the material of the second substrate. At least one of the second strain-relief features may extend only through one of the layers of the material of the second substrate. At least one of the second strain-relief features may not extend through all of the layers of the material of the second substrate. The second light panel may include a fifth connector electrically connected to the third power conductor, and a sixth connector electrically connected to the fourth power conductor. The lighting system may include a power distribution bus. The power distribution bus may include, consist essentially of, or consist of first and second power distribution lines, a seventh connector electrically connected to the first power distribution line, and an eighth connector electrically connected to the second power distribution line. The seventh connector may be configured for connection to the fifth connector, thereby electrically coupling the third power conductor to the first power distribution line. The eighth connector may be configured for connection to the sixth connector, thereby electrically coupling the fourth power conductor to the second power distribution line. 
     These and other objects, along with advantages and features of the invention, will become more apparent through reference to the following description, the accompanying drawings, and the claims. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations. Reference throughout this specification to “one example,” “an example,” “one embodiment,” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one example of the present technology. Thus, the occurrences of the phrases “in one example,” “in an example,” “one embodiment,” or “an embodiment” in various places throughout this specification are not necessarily all referring to the same example. Furthermore, the particular features, structures, routines, steps, or characteristics may be combined in any suitable manner in one or more examples of the technology. As used herein, the terms “about,” “approximately,” and “substantially” mean±10%, and in some embodiments, ±5%. The term “consists essentially of” means excluding other materials that contribute to function, unless otherwise defined herein. Nonetheless, such other materials may be present, collectively or individually, in trace amounts. 
     Herein, two components such as light-emitting elements and/or optical elements being “aligned” or “associated” with each other may refer to such components being mechanically and/or optically aligned. By “mechanically aligned” is meant coaxial or situated along a parallel axis. By “optically aligned” is meant that at least some light (or other electromagnetic signal) emitted by or passing through one component passes through and/or is emitted by the other. As used herein, the terms “phosphor,” “wavelength-conversion material,” and “light-conversion material” refer to any material that shifts the wavelength of light striking it and/or that is luminescent; fluorescent, and/or phosphorescent. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the present invention are described with reference to the following drawings, in which: 
         FIGS.  1 A- 1 E  are schematics of lighting panels in accordance with various embodiments of the invention; 
         FIG.  2 A  is a partial circuit diagram of a light sheet in accordance with various embodiments of the invention; 
         FIGS.  2 B and  2 C  are partial schematics of light sheets in accordance with various embodiments of the invention; 
         FIGS.  2 D and  2 E  are partial circuit topologies of light sheets in accordance with various embodiments of the invention; 
         FIG.  3    is a schematic of portions of a frame element in accordance with various embodiments of the invention; 
         FIGS.  4 A   4 E,  5 A, and  5 B are schematics of portions of a frame element in accordance with various embodiments of the invention; 
         FIGS.  5 C and  5 D  are schematics of a frame element in accordance with various embodiments of the invention; 
         FIGS.  6  and  7 A- 7 C  are schematics of illumination systems in accordance with various embodiments of the invention; 
         FIGS.  7 D- 7 F  are schematics of tiled lighting panels in accordance with various embodiments of the invention; 
         FIG.  8 A  is a perspective view of a frame element incorporating an insulation-displacement connector in accordance with various embodiments of the invention; 
         FIG.  8 B  is a cross-sectional view of a portion of the frame element of  FIG.  8 A ; 
         FIG.  8 C  is a schematic illustration of a lighting system incorporating four light panels in accordance with various embodiments of the invention; 
         FIGS.  9 A and  9 B  are cross-sectional schematics of conductive elements incorporated into frame elements in accordance with various embodiments of the invention; 
         FIG.  10 A  is a plan-view schematic of joined light panels in accordance with various embodiments of the invention; 
         FIG.  10 B  is a cross-sectional schematic of joined frame elements in accordance with various embodiments of the invention; 
         FIG.  11 A  is a partial circuit diagram of a portion of a system in accordance with various embodiments of the invention; 
         FIG.  11 B  is a plan-view schematic of a portion of a light sheet in accordance with various embodiments of the invention; 
         FIG.  11 C  is a cross-sectional schematic of the light-sheet portion of  FIG.  11 B ; 
         FIG.  11 D  is a cross-sectional schematic of the interior of a frame element in accordance with various embodiments of the invention; 
         FIGS.  12 A- 12 D  are cross-sectional schematics of frame elements in accordance with various embodiments of the invention; 
         FIG.  13 A  is a schematic diagram of an illumination system featuring two electrically connected light sheets in accordance with various embodiments of the invention; 
         FIG.  13 B  is a schematic cross-section of a clamping mechanism in accordance with various embodiments of the invention; 
         FIG.  14    is a schematic diagram of a lighting system in accordance with various embodiments of the invention; 
         FIGS.  15 A- 15 E  are schematic diagrams of light panels in accordance with various embodiments of the invention: 
         FIG.  16    is a cross-sectional schematic of a portion of a light panel in accordance with various embodiments of the invention; 
         FIGS.  17 A- 17 C  are schematic plan views of lighting systems in accordance with various embodiments of the invention; 
         FIGS.  18 A- 18 D  are cross-sectional schematics of light panels or light sheets incorporating electrical connectors in accordance with various embodiments of the invention; 
         FIGS.  18 E and  18 F  are cross-sectional schematics of light panels or light sheets joined via electrical connectors in accordance with various embodiments of the invention; 
         FIGS.  18 G and  18 H  are views of electrical connectors in accordance with various embodiments of the invention; 
         FIG.  19 A  is a perspective view of a light panel or light sheet incorporating tabs and electrical connectors in accordance with various embodiments of the invention; 
         FIGS.  19 B- 19 D  are magnified views of portions of light panels or light sheets that are folded and feature electrical connectors in accordance with various embodiments of the invention; 
         FIG.  19 E  is a perspective view of a light panel or light sheet having folded peripheral portions in accordance with various embodiments of the invention; 
         FIG.  19 F  is a schematic comparison of power conductor width of folded and unfolded light sheets or light panels in accordance with various embodiments of the invention; 
         FIG.  19 G  is a schematic of a portion of a light sheet or light panel incorporating multiple folds in accordance with various embodiments of the invention; 
         FIG.  19 H  is a perspective view of a light panel or light sheet having folded peripheral portions in accordance with various embodiments of the invention; 
         FIG.  19 I  is a schematic of a portion of a light sheet or light panel incorporating multiple folds in accordance with various embodiments of the invention; 
         FIGS.  19 J,  19 K, and  19 L  are schematics of power conductor configurations in accordance with various embodiments of the invention; 
         FIGS.  20 A and  20 B  are schematic plan views of light panels or light sheets in accordance with various embodiments of the invention; 
         FIGS.  20 C and  21 A   21 E are schematic plan views of lighting systems incorporating electrically connected light panels or light sheets in accordance with various embodiments of the invention; 
         FIG.  21 F  is a schematic side view of an installed lighting system in accordance with various embodiments of the invention; 
         FIGS.  22 A,  22 B,  23 A, and  23 B  are schematic plan views of lighting systems incorporating electrically connected light panels or light sheets in accordance with various embodiments of the invention; 
         FIGS.  24 A and  24 B  are perspective views of a light panel tab in accordance with various embodiments of the invention; and 
         FIG.  24 C  is a plan view of a multi-layer light tab panel in an unfolded configuration in accordance with various embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1 A  depicts an exemplary lighting panel  100  in accordance with embodiments of the present invention, although alternative systems with similar functionality are also within the scope of the invention. In various embodiments, lighting panel  100  includes or consists essentially of one or more flexible light sheets  110  and optionally one or more flexible, positionable, semi-rigid, substantially rigid, or rigid frame elements  120 . ( FIG.  1 A  depicts two such frame elements, frame elements  120 ,  120 ′.) Frame elements  120 ,  120 ′ may be disposed on all or portions of one or more edges of light sheet  110 . While  FIG.  1 A  shows lighting panel  100  having two frame elements  120 ,  120 ′ on opposite sides of light sheet  110 , this is not a limitation of the present invention, and in other embodiments lighting panel  100  may have frame elements  120  on one side of light sheet  110 , three sides of light sheet  110 , or four sides of light sheet  110  (i.e., one or more sides, or even all sides, of a polygonal light sheet  110 ). In various embodiments of the present invention lighting panel  100  may not include any frame elements. In various embodiments, one or more frame elements  120  may be disposed on a non-edge region of light sheet  110 , e.g., a center portion within the edges defining light sheet  110 , while in other embodiments one or more portions of a frame element  120  may be disposed such that a portion of the frame element  120  extends beyond one or more edges of light sheet  110 . 
     While  FIG.  1 A  shows frame elements  120  having a length about the same as the length of the side of light sheet  110  on which they are formed, this is not a limitation of the present invention, and in other embodiments frame elements  120  may be longer or shorter than the associated dimension of light sheet  110 .  FIG.  1 B  shows an example of frame element  120  having a length shorter than the associated dimension of light sheet  110 ; however, in other embodiments frame element  120  may have a length longer than the associated dimension of light sheet  110 . While  FIGS.  1 A and  1 B  show light sheet  110  as substantially square, this is not a limitation of the present invention, and in other embodiments light sheet  110  may be rectangular, triangular, wedge or pie-section shaped, rhombohedral, hexagonal, circular, ellipsoidal, or have any arbitrary shape.  FIGS.  1 C,  1 D, and  1 E  show examples of rectangular, triangular, and circular light sheets  110  respectively. 
     In various embodiments, light sheet  110  includes or consists essentially of an array of light-emitting elements (LEES) electrically coupled by conductive traces formed on a flexible substrate, for example as described in U.S. patent application Ser. No. 13/799,807, filed Mar. 13, 2013 (the &#39;807 application), or U.S. patent application Ser. No. 13/970,027, filed Aug. 19, 2013 (the &#39;027 application), the entire disclosure of each of which is herein hereby incorporated by reference. 
     In various embodiments, various elements such as frame elements, substrates, or light sheets are “flexible” in the sense of being pliant in response to a force and resilient, i.e., tending to elastically resume an original or substantially original configuration upon removal of the force. Such elements may have a radius of curvature of about 50 cm or less, or about 20 cm or less, or about 5 cm or less, or about 1 cm or less, or even about 0.5 cm or less. In various embodiments, flexible elements may have a Young&#39;s Modulus less than about 50×10 9  N/m 2 , less than about 10×10 9  N/m 2 , or even less than about 5×10 9  N/m 2 . In various embodiments, flexible elements may have a Shore A hardness value less than about 100; a Shore D hardness less than about 100; and/or a Rockwell hardness less than about 150. In various embodiments, such elements may permit folding and or creasing, for example folding of the element over on itself (e.g., folding a portion of the element through substantially 180°, such that the folded portion lays on and is substantially parallel to the non-folded portion) without substantially impairing the functionality of conductive traces on the substrate and/or the functionality of the substrate. For example, in various embodiments, the functionality of the conductive trace may include a resistance or conductance value; a reliability metric, a mechanical metric, or the like. In various embodiments, the functionality of the substrate may include a resistance value, a reliability metric, a mechanical metric, or the like. In various embodiments, a folded or creased element may have a radius of curvature of less than 2 mm, or less than 1 mm or less than 0.05 mm. In various embodiments of the present invention, the elements may be folded or creased without damage or substantial damage to the elements, for example to the substrate and/or conductive trace. In various embodiments of the present invention, the elements may be folded or creased without changing or substantially changing the electrical and/or mechanical and/or thermal and/or optical properties of the elements. 
     In various embodiments, various elements such as substrates, light sheets, or frame elements may be positionable, in the sense that they are pliant in response to a force, as with a flexible element, but upon removal of the force, retain or substantially retain the deformed shape. In various embodiments such positionable characteristics may be achieved by plastic deformation of the element; however, this is not a limitation of the present invention, and in other embodiments the positionable characteristic may be achieved without substantial plastic deformation of the element. Such elements may have essentially any radius of curvature, but in particular may have a radius of curvature of about 50 cm or less, or about 20 cm or less, or about 5 cm or less, or about 1 cm or less, or even about 0.5 cm or less. 
     In various embodiments, elements such as frame elements may be rigid or substantially rigid, in the sense that they are not pliant in response to a force, i.e., tending to break or crack in response to a force. In various embodiments, various elements such as substrates, light sheets, or frame elements are semi-rigid, i.e., having a deformation characteristic between that of a flexible element and a rigid or substantially rigid element. Such elements may have a radius of curvature greater than about 50 cm. 
       FIG.  2 A  depicts an exemplary circuit topology, in accordance with embodiments of the present invention, which features conductive traces  260 , at least two power conductors  210 ,  220 , multiple LEEs  230 , and optional control elements (CEs)  240 , In various embodiments, LEEs  230  may be configured in a regular periodic array, for example a substantially square or rectangular array, where LEEs  230  are separated by pitch (or “spacing”)  223  in the one direction (for example vertical direction) by pitch  225  in a substantially orthogonal direction (for example the horizontal direction; see  FIG.  2 C ). In various embodiments, pitch  225  is the same as or substantially the same as pitch  223 . 
       FIG.  2 A  shows two power conductors  210 ,  220 , which may be used to provide power to strings  250  of LEEs  230 . Each string  250  may include two or more electrically coupled LEEs  230 . LEEs  230  in string  250  may be electrically coupled in series, as shown in  FIG.  2 A ; however, this is not a limitation of the present invention, and in other embodiments other examples of electrical coupling may be utilized, for example LEEs in parallel or in any combination of series and parallel connections.  FIG.  2 A  shows CE  240  in series with string  250 ; however, this is not a limitation of the present invention, and in other embodiments CE  240  may have different electrical coupling between power conductors  210 ,  220 , or may be absent altogether. For example, in various embodiments CE  240  may be separately electrically coupled to power conductors  210 ,  220  and to the LEE string  250 , while in other embodiments each CE  240  may be electrically coupled to two or more strings. The number of strings electrically coupled to each CE  240  is not a limitation of the present invention. Combinations of structures described herein, as well as other electrical connections, all fall within the scope of the present invention. Power conductors  210 ,  220  may be used to provide power to strings  250 , for example AC power, DC power, or power modulated by any other means. Each control element  240  may be, for example electrically connected to at least one light-emitting string  250  and configured to utilize power supplied from the power conductors  210 ,  220  to control power (e.g., supply a substantially constant current) to the light-emitting string(s)  250  to which it is electrically connected. 
     Referring to  FIGS.  2 B and  2 C  that depict schematics of exemplary light sheets  110 , light sheet  110  features an array of LEEs  230  each electrically coupled between conductive traces  260 , and power conductors  210  and  220  providing power to conductive traces  260  and CEs  240 , all of which are disposed over a substrate  265 . As utilized herein, a “wiring board” refers to a substrate for LEEs with or without additional elements such as conductive traces or CEs. A wiring board may also be referred to as a light sheet or a circuit board.  FIG.  2 B  shows an enlarged portion of an exemplary light sheet  110 . In the exemplary embodiment depicted in  FIG.  2 B , power conductors  210 ,  220  are spaced apart from each other and light-emitting strings (or simply “strings”)  250  are connected in parallel across power conductors  210 ,  220 . In various embodiments, for example as shown in  FIG.  2 B , strings  250  do not cross (i.e., intersect) each other. In other words, power conductors  210 ,  220  are oriented in one direction and strings  250  are oriented such that they span power conductors  210 ,  220  in a different direction. As shown in  FIG.  2 B , strings  250  may be substantially perpendicular to power conductors  210 ,  220 . However, this is not a limitation of the present invention, and in other embodiments at least some segments (i.e., portions connecting two or more LEEs  230 ), or even the entire strings  250 , may define a line (not necessarily a straight line) that is not perpendicular to power conductors  210 ,  220  yet is (at least for an entire sting  250 ) not parallel to power conductors  210 ,  220 . In other embodiments strings  250  may intersect, for example one string  250  splitting into two or more strings  250 , or two or more strings  250  joining to form a reduced number of strings  250 . In various embodiments, conductive traces  260  may cross over each other without being electrically coupled to each other, and in various embodiments, strings  250  may cross over or under each other without being electrically coupled to each other. In various embodiments, all or a portion of one or more strings  250  may extend beyond the area disposed between the power conductors  210 ,  220 . Various examples of string geometries and conformations utilized in embodiments of the present invention are detailed in the &#39;807 and &#39;027 applications. 
     As shown in  FIGS.  2 B and  2 C , LEEs  230  may be positioned across substrate  265  in a regular periodic array, although this is not a limitation of the present invention, and in other embodiments LEEs  230  may occupy any positions on light sheet  110 . Power conductors  210  and  220  provide power to each LEE string, for example the string  250  encircled by the dashed line in  FIG.  2 B . Each LEE string  250  typically includes multiple conductive traces  260  that interconnect multiple LEEs  230 , as well as one or more CEs  240 , which in  FIG.  2 B  is in series with LEEs  230 . String  250  shown in  FIG.  2 B  is a folded string, i.e., a string that has three segments electrically coupled in series but positioned as three adjacent segments. A string segment is a portion of a string spanning all or a portion of the region between power conductors (e.g., power conductors  210  and  220  in  FIG.  2 B ). In light sheet  110 , some string segments may include LEEs  230  and others may not. However, in other embodiments, the distribution and position of LEEs  230  along conductive elements  260  and string segments may be different. In various embodiments, a string  250  may be a straight string, i.e., a string with no folds, as shown in  FIG.  2 C . (The example shown in  FIG.  2 C  does not include CEs  240 .) In a straight string, one end of string  250  is electrically coupled to power conductor  210 , while the other end of string  250  is electrically coupled to power conductor  220  with no turns or corners therebetween. As will be discussed, the number of segments in a string  250  is not a limitation of the present invention. Various examples of straight and folded strings utilized in embodiments of the present invention are detailed in the &#39;807 and &#39;027 applications. 
       FIGS.  2 A and  2 B  illustrate three aspects of various embodiments in accordance with embodiments of the present invention. The first is the multiple strings  250  that are powered by the set of power conductors  210 ,  220 . The second is the positional relationship between the locations of LEEs  230  and CE  240 , which is disposed between the conductive traces  260  and between power conductors  210 , 220 . The third is the inclusion of a CE  240  in each string of series-connected LEEs  230 . Combinations of these three aspects enable light sheet  110  to be economically manufactured in very long lengths, for example in a roll-to-roll process, and cut to specified lengths, forming light sheets, while maintaining the ability to tile, or place light sheets adjacent to each other (e.g., in the length direction), with no or substantially no change in pitch between LEEs  230  or in the optical characteristics across the joint between two adjacent light sheets, as discussed in more detail in the &#39;807 and &#39;027 applications. 
     In an exemplary embodiment, CE  240  is configured to regulate the current or maintain a constant or substantially constant current through LEEs  230  of string  250 . For example, in various embodiments, a constant or substantially constant voltage may be applied to power conductors  210 ,  220 , which may, under certain circumstances may have some variation, or the sum of the forward voltages of LEEs  230  in different strings may be somewhat different, for example as a result of LEE manufacturing tolerances, or the component and/or operational values of the element(s) within CE  240  may vary, for example as a result of manufacturing tolerances or changes in operating temperature, and CE  240  acts to maintain the current through LEEs  230  substantially constant in the face of these variations. In other words, in various embodiments the input to the light sheet is a constant voltage that is applied to power conductors  210 ,  220 , and CEs  240  convert the constant voltage to a constant or substantially constant current through LEEs  230 . As will be described herein, the design of CE  240  may be varied to provide different levels of control or variation of the current through LEEs  230 . In various embodiments, CEs  240  may control the current through LEEs  230  to be substantially constant with a variation of less than about +25%. In various embodiments, CEs  240  may control the current through LEEs  230  to be substantially constant with a variation of less than about ±15%. In various embodiments, CEs  240  may control the current through LEEs  230  to be substantially constant with a variation of less than about +10%. In various embodiments, CEs  240  may control the current through LEEs  230  to be substantially constant with a variation of less than about +5%. 
     In various embodiments, as described herein, CEs  240  may, in response to a control signal, act to maintain a constant or substantially constant current through LEEs  230  until instructed to change to a different constant or substantially constant current, for example by an external control signal. In various embodiments, as described herein, all CEs  240  on a sheet may act in concert, that is maintain or change the current through all associated LEEs  230 ; however, this is not a limitation of the present invention, and in other embodiments one or more CEs  240  may be individually controlled and/or energized. 
     While  FIG.  2 A  shows one exemplary circuit topology, this is not a limitation of the present invention, and in other embodiments other circuit topologies may be utilized. For example, in various embodiments the circuit may not include any CEs  240 . In various embodiments of the present invention, the electrical topology may include one or more cross-connecting elements, for example which may electrically couple conductive elements in in separate stings, for example as described in U.S. patent application Ser. No. 13/378,880, filed on Dec. 16, 2011, and U.S. patent application Ser. No. 13/183,684, filed on Jul. 15, 2011, the entirety of each of which is incorporated by reference herein.  FIGS.  2 D and  2 E  show two examples of such a cross-connection topology. In the circuit shown in  FIG.  2 D , each LEE  230  is cross-connected with adjacent LEEs  230 , while in  FIG.  2 E , only some of LEEs  230  are cross-connected with adjacent LEEs  230 . 
     In various embodiments of the present invention, frame elements  120  provide a rigid or semi-rigid support for light sheet  110 . In various embodiments, a frame element  120  may include or consist essentially of a plastic material, for example acrylic, acrylonitrile butadiene styrene (ABS), polyethylene, thermoplastic polyurethane (TPU), or the like. In various embodiments, frame element  120  may include or consist essentially of one or more metals, such as aluminum, copper, or the like, or silicone, wood or other materials. In various embodiments, frame element  120  may include or consist essentially of a combination of materials. 
     In various embodiments of the present invention, frame elements  120  provide a flexible support for light sheet  110 . In various embodiments of the present invention, frame elements  120  provide a positionable support for light sheet  110 . 
     In various embodiments, light sheet  110  has one or more openings (or “holes”), for example along the edge of light sheet  110 , that mate to frame element  120 , and frame element  120  has one or more corresponding locating pins over which the holes are positioned, to provide accurate and repeatable positioning of light sheet  110  in frame element  120 .  FIG.  3    shows a schematic of one embodiment that features locating pins  310  on frame element  120  and locating holes  320  in light sheet  110 .  FIG.  3    shows two light sheets,  110  and  110 ′. Light sheet  110  is positioned above frame element  120  while light sheet  110 ′ is positioned on frame element  120  such that locator pin  310  is at least partially inserted into locating hole  320 .  FIG.  3    shows one additional aspect of various embodiments of the present invention, in which a frame element  120  may be used to couple two or more light sheets  110  together into a single lighting system. While the structures shown in  FIGS.  3  and  4 A- 4 C  use pins and holes to align one or more light sheets  110  to one or more frame elements  120 , this is not a limitation of the present invention, and in other embodiments other techniques and/or structures may be utilized to align and/or hold light sheet  110  in frame element  120 . For example, light sheet  110  may be aligned to frame element  120  using alignment marks on light sheet  110  and/or frame element  120 , In various embodiments, light sheet  110  may be attached or fastened to frame element  120  by other means, for example screws, nuts and bolts, tape, adhesive, glue, external clamps, magnets, heat stakes, or the like. For example,  FIG.  4 D  shows a two-piece frame element  120  fastened to light sheet  110  using a clamp or spring clamp  450 .  FIG.  4 E  shows another example in which frame element  120  (having a hinge  430 ) is fastened to light sheet  110  using an adhesive  460 . In various embodiments, adhesive  460  may include or consist essentially of glue, tape, double-sided tape, or the like. The method of attaching light sheet  110  to frame element  120  is not a limitation of the present invention. 
     In various embodiments, frame element  120  has one or more hinges, such that the frame element  120  may be folded over and clamped to light sheet  110 . In various embodiments, the locating pins in frame element  120  may act as a fastener that keeps (or helps keep) frame element  120  closed around light sheet  110 .  FIGS.  4 A and  4 B  show a schematic of one embodiment of the present invention.  FIG.  4 A  shows an unfolded frame element  120  that includes or consists essentially of a hinge  430 , a locating pin  410  (that is composed of two or more protrusions), and a locating hole  420 . In the depicted embodiment, locating pin  410  is designed to be compressed before being inserted through locating hole  420  and then to spring open to lock frame element  120  in the folded or closed position, as shown in  FIG.  4 B . In various embodiments, locating pin  410  may, include or consist essentially of a snap hook instead of a compression element, as shown in  FIG.  5 A  (unfolded, or “open,” conformation) and  5 B (folded, or “closed,” conformation).  FIG.  4 B  shows light sheet  110  clamped into a folded frame element  120 , where locating pin  410  has been inserted through locating hole  320  in light sheet  110  and through locating hole  420  in frame element  120 . In various embodiments, frame element  120  and/or light sheet  110  may include holes that may be used for mounting frame element  120 .  FIG.  4 C  shows one example of such an embodiment, in which the light panel  100  has mounting hole  440  that goes through light sheet  110  and frame element  120 . As described herein, mounting hole  440  includes or consists essentially of mounting hole  441  in frame element  120  and mounting hole  442  in light sheet  110   FIGS.  5 C and  5 D  show schematic views of one embodiment of frame element  120  in the open and closed positions, respectively. 
     As described herein, light panel  100  may be designed to be cut to length, for example between strings  250 , such that at least one and optionally both sections are operable after separation. In various embodiments, light panel  100  includes locating pins  310  and/or locating pins and holes  410 ,  420  and/or mounting holes  441 ,  442 , to permit locating, clamping, and/or mounting of light panel  100  after light panel  100  (including or consisting substantially of one or more light sheets  110  and one or more frame elements  120 ) has been cut or separated into one or more portions.  FIG.  6    shows a schematic of one embodiment showing two strings  250  and  250 ′ and a separation or cut region  620  on frame element  120  and a separation or cut region  610  on light sheet  110 . As shown, the section including string  250  also includes mounting hole  440  and locating pin/fastener  410 , and the section including string  250 ′ also includes mounting hole  440 ′ and locating pin/fastener  410 ′. If lighting panel  100  is separated along cur regions  620  and  610 , each section has its own mounting hole and locating pin/fastener. In various embodiments, frame element  120  and light sheet  110  are designed to facilitate separation of lighting panel  100 , for example by incorporating identified separation lines or regions on frame element  120  and/or light sheet  110 . For example, in various embodiments separation line  610  may be formed on light sheet  110  by printing, or by a pattern in one or more conductive elements  260  and/or one or both power conductors  210 ,  220 . In various embodiments, cut region  610  may be free of or substantially free of conductive elements  265 . In various embodiments, light sheet  110  may include a coating over all or portions of substrate  265 , power conductors  210 ,  220  and conductive elements  265  and separation line  610  may be formed in the coating material, or by the absence of the coating material in separation region  610 . In various embodiments, separation line  620  on frame element  120  may include or consist essentially of markings on frame element  120 , for example that are formed in frame element  120  or printed on frame element  120 . In various embodiments, separation line  620  may include or consist essentially of a region engineered to separate more easily than adjacent regions of frame element  120 , for example by having a reduced thickness compared to adjacent regions of frame  120  and/or perforations defined therein. In various embodiments, light panel  100  may be separated by cutting through frame element  120  in region  620  and light sheet  110  in region  610 , for example with a scissors or knife or other cutting implement. The means of separation of light panel  100  is not a limitation of the present invention. 
     In various embodiments, light panel  100  may be mounted (e.g., to a mounting surface such as a wall, a ceiling, or a fixture), for example using screws or nails or other fasteners that may be inserted through mounting holes  440 ; however, this is not a limitation of the present invention, and in other embodiments light panel  100  may be mounted by other means, for example staples, tape, double-sided tape, magnets, a hook-and-loop fastener such as Velcro, or the like. In various embodiments, frame element  120  may include or incorporate mounting elements, for example double-sided tape or barbed pins that may be used to mount light panel  100  to a mounting surface. 
     In various embodiments, frame element  120  may be designed to have a width less than one-half of the pitch between LEEs  230  in the direction between frame elements  120  of adjacent light panels  100 , such that if two light panels  100  are positioned next to each other, the pitch between nearest neighbor LEEs  230  on adjacent light panels  100  may be the same or substantially the same as the pitch between nearest neighbor LEEs  230  on each light panel  100 .  FIG.  7 A  shows a schematic of one example of this embodiment, depicting two light panels  100  and  100 ′, each featuring frame elements  120  and light sheets  110 . As shown, a pitch  223  between LEEs  230  in the direction between frame elements is the same on light panels  100  and  100 ′ as it is between LEEs  230  on adjacent light sheets  110  and separated by frame elements  120 . For example, in various embodiments LEE pitch  223  may be about 30 mm and frame element  120  may have a width in the range of about 5 ram to about 14 ram. In various embodiments, the width  710  of frame element  120  may be less than about 0.95×(pitch  223 /2). In various embodiments, LEE pitch  223  may be about 20 mm and frame width  710  may be in the range of about 3 mm to about 9 mm. 
       FIG.  7 B  shows an example featuring four light panels  100  (one panel is encircled in a heavy dashed line), each panel  100  including two frame elements  120  on opposite sides of light sheet  110 . As shown, pitch  223  is the same on one sheet as it is across frame elements  120  on adjacent sheets. In this example LEE pitch  223  is about 30 mm and frame width  710  is about 10 mm. 
       FIG.  7 B  shows an additional feature that may be incorporated in various embodiments of the present invention, identified as connector  720 . Connector  720  may be utilized to join together two frame elements  120 . In various embodiments, connector  720  may be designed such that pitch  225  is the same between nearest-neighbor LEEs  230  on adjacent light sheets  110  as it is on a single light sheet  110 . In various embodiments, connector  720  may include or consist essentially of a portion of frame element  120  that extends beyond the length of light sheet  110  and includes a mechanism for attaching to an adjacent frame element  120 . For example in various embodiments, as shown in  FIG.  7 C , connector  720 ′ may include a locating hole  730 ′ in frame element  120 ′ and that fits over a locating pin  740  on an adjacent frame element  120 . In various embodiments, there may be a corresponding section  720  on the other end of frame element  120  (i.e., away from connector  720 ′, not shown in  FIG.  7 C ). Locating hole  730 ′ and locating pin  740  are preferably positioned such that pitch  225  between LEEs in the direction along frame elements  120 ,  120 ′ is the same between light panels  100  as on an individual light panel  100 , irrespective of the interface between the light panels  100 . In various embodiments, locating pin  740  may also be used to position light sheet  110 , similar to the approach discussed in reference to  FIG.  3   . In various embodiments, connector  720  may include a conventional electrical connector, such as a pin and jack system, where adjacent light sheets  120  are electrically coupled through the electrical connector. For example, a frame element may feature a connector electrically coupled to a power conductor on the light sheet, and the connector may be electrically coupled to a corresponding connector on an adjacent frame element. In various embodiments, the electrical connectors (or electrical portions of the connector) may mate directly, while in other embodiments a jumper wire may be used to electrically couple the two connectors. In various embodiments, such a system may be employed to electrically couple two or more light panels that are spaced apart from each other. 
     In various embodiments, the system shown in  FIG.  7 B  includes frame elements  120  that, when attached to light sheet  110 , have a width  710  of about 10 mm. In this example light sheet  110  has a square shape with a side length of about 300 mm, LEEs  230  have a pitch  223  of about 33 mm and a pitch  225  of about 30 mm. In this example connector  720  has a length beyond light sheet  110  in the range of about 5 mm to about 30 mm. These dimensions are exemplary and not limitations of the present invention. 
     The ability to tile light panels  100  in multiple directions provides a system that may be utilized to make arbitrarily large assemblies having uniform illuminance with no relatively darker areas in the joint regions between adjacent panels. 
     While the systems described in reference to  FIGS.  6  and  7 A- 7 C  pertain to rectilinear light panels, this is not a limitation of the present invention, and in other embodiments other light panel shapes may be used. For example  FIG.  7 D  shows a light panel system incorporating triangular light panels,  FIG.  7 E  shows a system incorporating diamond-shaped light panels, and  FIG.  7 F  shows a system incorporating hexagonal light panels. The shapes depicted in  FIGS.  7 D   7 F are meant to be exemplary and are not limitations of the present invention. 
     In various embodiments, frame elements  120  provide support for light sheets  110  and a means for providing electrical connections to light sheet  110 , for example to provide power to power conductors  210 ,  220 . In various embodiments, frame elements  120  enable electrical coupling of one or more control signals, for example to dim or change the intensity of one or more LEEs  230  on light sheet  110 , or to change the color of light emitted by LEEs  230 , to light sheet  110 . 
       FIG.  8 A  shows one embodiment of a frame element  120  that incorporates an insulation-displacement connector (IDC)  810  that is electrically coupled to one of power conductors  210 ,  220  on light sheet  110 . (As utilized herein, an IDC is an electrical connector designed to be connected to the conductor(s) of an insulated wire or cable by a connection process that forces a selectively sharpened blade or blades (or other cutting or piercing element) through the insulation, bypassing the need to strip the wire of insulation before connecting.) Note that  FIG.  8 A  shows two adjacent light panels. IDC  810  is formed or disposed into a hole in frame element  120 , permitting access to it when light sheet  110  is attached to frame element  120 . A wire  830 , preferably an insulated wire, is inserted in IDC  810 , which then provides electrical connection to power conductors  210 ,  220  on light sheet  110 .  FIG.  8 B  shows a cross-sectional schematic of such a structure, including a bottom portion  12013  of the frame element, a top portion  120 T of the frame element, and a hole  820  through which MC  810  is inserted. IDC  810  is electrically coupled to power conductor  210 , for example using solder, conductive adhesive, anisotropic conductive adhesive, or the like. Power conductor  210  is disposed on substrate  265 . Referring back to  FIG.  8 A , after frame  120  is attached to light sheet  110 , wire  830  is inserted into IDC  810  to electrically couple wire  830  to the underlying conductive element (not shown in  FIG.  8 A , and in  FIG.  8 B  is exemplified by power conductor  210 ). Optional cap  840  may be used to aid in insertion of wire  830  into IDC  810  and/or to provide a protective cover over IDC  810 . Optional guide elements  850  may be utilized to hold wire  830  into place on frame element  120 .  FIG.  8 A  also shows mounting holes  440 . In the depicted embodiment, frame element  120  is installed substantially parallel to and over power conductors  210 ,  220  on light sheet  110 . 
       FIG.  8 C  shows a schematic of a lighting system incorporating four light panels  100 . The lighting system is powered by a driver  860 , which is electrically coupled to light panels  100  through wires  830  and  830 ′. In various embodiments, this and similar arrangements permit the assembly of very large lighting systems without the need for the power conductors  210 ,  220  to have sufficient conductivity to support the entire assembly, because wires  830 ,  830 ′ have relatively larger conductivity and provide a low resistance shunt to power conductors  210 ,  220 , In various embodiments, for example where it may be desirable to separate the light panel into smaller sections (e.g., in reference to  FIG.  6   ), several IDCs  810  may be incorporated on light sheet  110  to permit separation into two or more portions, each of which has an IDC  810 . In various embodiments, one or more electrical conductors may be incorporated into frame element  120 . For example, in various embodiments, frame element  120  features a conductive element  910  that is attached to or embedded or partially embedded into frame element  120 , as shown in  FIG.  9 A . Frame element  120  is clamped onto light sheet  110 , forming an electrical and mechanical connection between conductive element  910  and power conductor  210 . In various embodiments, conductive element  910  may be mounted on a surface of frame element  120 , as shown in  FIG.  9 B . In various embodiments, conductive element  910  includes or consists essentially of one or more electrically conductive materials such as metals such as aluminum, copper, silver, gold, or the like. In various embodiments, conductive element  910  may include or consist essentially of a metal foil or metal strip. In various embodiments, conductive element  910  includes an electrically conductive tape, for example one that is conductive in both the lateral and z (i.e., through-thickness) directions, such that a low-resistance pathway forms between power conductor  210  and conductive element  910  and conductive element  910  forms a low-resistance pathway in parallel with power conductor  210 . In various embodiments, conductive element  910  includes or consists essentially of a combination of materials, for example a metal layer over which is disposed a conductive adhesive or a conductive tape. In various embodiments, IDC  810  may be replaced by a pin or a barbed pin that mates with a corresponding connector or pierces a conductive element  910  mounted in frame element  120 . 
     Electrical connection between adjacent light panels  100  and between light panels  100  and one or more power supplies or drivers may be formed through frame elements  120 . In various embodiments, magnets of the appropriate polarity may be mounted or formed within or at the ends of frame elements  120 , such that each frame may be mechanically and electrically connected through the magnets, for example as shown in  FIG.  10 A . In  FIG.  10 A , the opposing faces of magnets  1010  and  1020  have opposite polarities, so that the light panels may only be connected in one way. In various embodiments, this prevents incorrect connection of multiple light panels  100 . 
     In various embodiments, frame element  120  may include one or more connectors or mechanisms for electrical coupling. In various embodiments, conductive elements such as conductive elements  910 , as shown in  FIGS.  9 A and  9 B , may be used to electrically couple two frames.  FIG.  10 B  shows one example featuring the joining of frames  120  and  120 ′. In this example, the top portion  1201  of frame element  120  and conductive element  910  extend beyond the end of substrate  265 . In the second frame, the bottom portion  12013 ′ of frame element  120 ′ and conductive element  910 ′ extend beyond the edge of substrate  265 ′. Conductive elements  910  and  910 ′ are electrically coupled through a conductive element  1030 , which may be, for example, a metallic conductor or a conductive adhesive, conductive glue, or conductive tape.  FIG.  10 B  shows one embodiment of electrically coupling light panels  100 ; however, this specific method is not a limitation of the present invention, and in other embodiments other methods of electrically coupling light panels  100  may be employed. 
     In various embodiments, wires may be soldered or otherwise electrically coupled to power conductors  210 ,  220 , and multiple light panels  100  may be electrically coupled through standard wiring techniques, for example using connectors, wire nuts, soldering, or the like. For example, in various embodiments connectors may be formed on frame elements  120  and electrically conductive jumpers may be used to electrically couple adjacent light panels  100 . While much of the discussion herein has been related to lighting systems in which the light panels are butted up next to each other, this is not a limitation of the present invention, and in other embodiments one or more light panels in a system may be spaced apart from the others. In such embodiments, relatively longer jumpers may be used to connect the light panels together. 
     In various embodiments, a frame element  120  may include more than one conductive element  910 . For example, conductive elements in frame element  120  may be used, in addition to powering light panel  100 , to provide communication and control signals to and from light panel  100 . In various embodiments, conductive elements in or on frame  120  may be used to provide electrical crossovers, i.e., to permit additional circuitry complexity while still using only one layer of conductive elements  260  on substrate  265 . For example, FIG. HA shows an electrical schematic of a system having two different LEEs  230 ,  230 ′. In various embodiments, LEE  230  may have a different color than LEE  230 ′, or a different intensity, or a different light distribution pattern, or a difference in any other electrical and/or optical property. In various embodiments, LEEs  230  and  230 ′ may both emit white light, but with different color temperatures, and the color temperature of the light panel may be adjusted by changing the light intensity emitted by strings with different color-temperature LEEs. For example in various embodiments LEEs  230  may have a correlated color temperature (CCT) of about 2000K and LEEs  230 ′ may have a CCT of about 10,000K, and the CCT of the ensemble may be varied between about 2000K and about 10,000K by varying the power delivered to strings having LEEs  230  and  230 ′. In various embodiments, LEEs  230  may have a CCI of about 2700K and LEEs  230 ′ may have a CCT of about 6000K, and the CCT of the ensemble may be varied between about 2700K and about 6000K by varying the power delivered to strings having LEEs  230  and  230 ′. 
     In various embodiments, the lighting system is driven by a substantially constant voltage supply that is pulse-width modulated, that is the voltage is kept substantially the same during the “on” phase and the light intensity is varied by changing the duty cycle, or the ratio of “on” to “off” time of the power signal. The circuit of  FIG.  11 A  requires the power to the two different types of strings to be modulated separately, and thus requires three, or perhaps four (if separate returns are required) conductors. As shown in the schematic of  FIG.  11 A , this may require an electrical cross-over. While light sheets with multiple conductive layers may be manufactured, these are relatively more expensive. In various embodiments of the present invention, conductive elements within frame element  120  may form one or more electrical cross-overs, permitting circuits such as that shown in  FIG.  11 A  to be realized with a light sheet with only one conductive layer. 
       FIG.  11 B  shows one example of a pattern of power conductor traces for power conductors  220  and  220 ′, that, combined with the frame element of  FIG.  11 C , permit realization of circuits requiring crossovers with a light sheet having a single conductive layer.  FIG.  11 B  shows a portion of a light sheet, including substrate  265  on which power conductors  220  and  220 ′ as well as conductive elements  260  have been formed. Conductive elements  260  electrically couple LEEs  230 , such that LEEs  230 ′ are electrically coupled to power conductor  220 ′ and LEEs  230  are electrically coupled to power conductor  220 . However, as shown in  FIG.  11 B , power conductor  220  is discontinuous and requires a crossover in a region  1100  to form a complete circuit.  FIG.  11 C  shows a cross-section of the structure of  FIG.  11 B  through cut-line A-A′. As shown in  FIG.  11 C , conductive element  910  associated with power conductor  220  in top frame  120 T is formed such that it does not electrically couple with power conductor  220 ′. In various embodiments, this may be achieved by spacing conductive element  910  apart from power conductor  220 ′, while in other embodiments an insulating layer, for example plastic or insulating tape or paper may be positioned between power conductor  220 ′ and conductive element  910 . Not shown in  FIG.  11 C  is conductive element  910 ′, which is associated with power conductor  220 ′, in top frame element  120 T.  FIG.  11 D  shows a plan view of the inside of top frame element  1207 , showing both conductive elements  910  and  910 ′, where conductive element  910  has region  1100  that is designed to prevent electrical coupling to the underlying portion of power conductor  220 ′. 
     While  FIGS.  11 A- 11 D  show a system having one level of cross-over, this is not a limitation of the present invention, and in other embodiments more than one level of cross-over may be utilized. In various embodiments, two levels may be utilized, with a light panel having two frame elements, with each frame element having one level of cross-over. In various embodiments, more than one level of cross-over may be utilized in a single frame element  120 . It should be noted that the system shown in  FIG.  11 B  has three LEEs  230  in each string; however, this is not a limitation of the present invention, and in other embodiments more LEEs may be utilized in each string. While  FIG.  11 C  shows one form of cross-over, this is not a limitation of the present invention, and in other embodiments other types of cross-overs may be formed. For example, cross-overs may be formed using any of the approaches described herein for electrically coupling multiple frame elements together. 
     In various embodiments, additional elements may be added to frame element  120  to provide added functionality. For example, in various embodiments frame element  120  may include one or more spacers  1210  to space light panel  100  away from a mounting surface  1220 , as shown in  FIG.  12 A , In various embodiments, frame element  120  may include spacers to aid in maintaining a specific gap between the light sheet and an overlying optic, diffuser or translucent panel, and/or graphic panel  1240 . (Herein, a “graphic panel” is a panel overlying a lighting system that includes therein or thereon a pattern (e.g., words, images, graphics, etc.) for display when illuminated by the lighting system.) In various embodiments, such spacers may be fixed spacers  1230 , as shown in  FIG.  12 B , or they may be adjustable spacers  1250 , for example as shown in  FIG.  12 C  where the spacers  1250  screw into the frame element  120 , thereby controlling the offset distance. In various embodiments, diffuser  1240  may be positioned along the shaft of spacer  1250 , for example by using clamps, a threaded shaft and bolts, or by other means. In various embodiments, frame element  120  may include a track or slot  1260  to hold one or more overlying panels or diffusers, as shown in  FIG.  12 D . 
     While  FIGS.  12 B- 12 D  show one or more spacers  1230  attached to (or part of) frame element  120 , this is not a limitation of the present invention, and in other embodiments one or more spacers  1230  may be disposed on light sheet  110 , for example on light sheet  110  between LEEs  230 . In various embodiments, spacers  1230  may be positioned, shaped, or constructed of one or more materials to minimize the impact of the spacer on the spatial and/or spectral light distribution. For example, in various embodiments of the present invention, a spacer or a portion of a spacer may include or consist essentially of a transparent material. In various embodiments, a spacer or a portion of a spacer may be reflective to a wavelength of light emitted by LEEs  230 . For example, the spacer (or portion thereof) may have a reflectance greater than 75% to a wavelength of light emitted by LEEs  230 , In various embodiments of the present invention, a spacer or a portion of the spacer may have specular reflectance or a diffuse reflectance. In various embodiments, a spacer or a portion of a spacer may have a white surface or be coated with a white material having a diffuse reflectance to a wavelength of light emitted by LEEs  230 . In various embodiments, a portion of the conductive trace material may be removed from the substrate in one or more spacer regions, for example to aid in positioning of the spacer. In various embodiments, a portion of the substrate material may be removed in one or more spacer regions, for example to facilitate the mounting of the spacer to the underlying support structure. 
     In various embodiments, light sheets may be electrically connected together through an array of conductive elements mounted over the mounting surface.  FIG.  13 A  shows an example of such a system that includes or consists of power elements  1310  and  1320  to which one or more light sheets  110  may be electrically coupled and mechanically attached. Power elements  1310  and  1320  may be metallic conductors, for example wires, bare wires, or bus bars, that are mounted on the mounting surface. In this approach, the layout of power elements  1310  and  1320  in part determines the position of light sheets  100 , i.e., they determine the position in one direction, while the position in the orthogonal direction may be varied by moving the light sheet along the power elements. As shown in  FIG.  13 A , light sheets  110  may be spaced apart; however, this is not a limitation of the present invention, and in other embodiments they may be butted together to maintain LEE  230  pitch between adjacent light sheets  110 . In various embodiments, light sheet  110  may be electrically and mechanically coupled to power elements  1310 ,  1320  by a clamp mechanism, for example a clamp  1340 , as shown in  FIG.  13 B . Other methods for electrically coupling and mechanically attaching light sheet  110  to power elements  1310 ,  1320  include conductive tape, adhesive, screws, rivets, or the like. In various embodiments, a frame element may be combined with this approach to permit attachment and electrical coupling of the light panel to the power elements by an attachment in frame element  120 . One aspect of this approach is that length adjustment of light sheet  110  may be accomplished by cutting the light sheet itself and mounting it to power elements that have been previously fabricated to the desired length. In various embodiments, the features described with respect to  FIGS.  12 A- 12 D  may be incorporated into this embodiment featuring an array of power lines. In various embodiments, one or more signal or control lines may also be incorporated to provide a means for control and communication to one or more light panels or light sheets, or signals may be incorporated or modulated on the power supply lines. 
       FIG.  14    shows an example of a lighting system of the present invention, including power supply or driver  860  and four light panels  100 . While four light panels are shown in  FIG.  14   , this is not a limitation of the present invention, and in other embodiments fewer or more light panels may be incorporated. In some embodiments, a system may include more than 20 light panels or more than 100 light panels. In various embodiments, wires  830  and  830 ′ may be connected to the same edge of light panel  100 , as shown in  FIG.  14   , in contrast to the wiring schematic shown in  FIG.  8 C . In the system of  FIG.  14   , each light panel  100  includes power conductors  210 ,  220 . Power conductors  210  are electrically coupled to wire  830 , while power conductors  220  are electrically coupled to wire  830 . In this way, the array of light panels  100  may be energized from only one side of the array. (Not shown in  FIG.  14    for clarity, but discussed herein, are optional frame  120  and electrical connections between power conductors  210 ,  220  on adjacent sheets.) 
     In various embodiments, driver  860  is a substantially constant voltage supply, the output of which is pulse-width modulated to permit dimming of LEEs  230  on light panels  100 . In various embodiments, the lighting system is a UL class 2 system having an operating voltage not exceeding 60 V. 
     In various embodiments, light panel  100  is square, having a side dimension in the range of about 10 cm to about 100 cm. In various embodiments, LEE pitches  223  and  225  are each in the range of about 5 mm to about 50 mm. 
     While frame elements  120  in  FIGS.  5 A- 5 D   6 ,  7 A,  7 B,  8 A, and  8 C have been depicted as straight or substantially straight, this is not a limitation of the present invention, and in other embodiments frame elements may have more than one straight portions, as shown in  FIG.  15 A , or may be curved, as shown in  FIG.  15 B , or may include straight or curved elements, as shown in  FIG.  15 C , The shape or geometry of frame element  120  is not a limitation of the present invention. For example, the structure shown in  FIG.  15 B  may be used to form a free-standing or partially free-standing light panel structure as shown in  FIG.  15 D , or may be mounted to a shaped surface having substantially the same shape as the shaped light panel, as shown in  FIG.  15 E . In various embodiments, structures such as those shown in  FIGS.  15 D and  15 E  may also be formed using flexible or semi-rigid light panels. 
     In various embodiments of the present invention, the light panel may be positionable. In such embodiments, the light panel may be flexible, but when deformed, it retains the deformed position, or substantially the deformed position, after the deforming force is removed. Such embodiments may also be used to form structures such as those shown in  FIGS.  15 A- 15 E . In various embodiments, a positionable frame element  110  may include or consist essentially of a flexible material combined with a deformable but relatively inflexible material, such as a wire.  FIG.  16    depicts a cross-section of an exemplary positionable frame element including a flexible body  1610  surrounding a wire or positionable element  1620 ; however, this is not a limitation of the present invention, and in other embodiments other means may be utilized to construct a positionable frame element or a positionable light panel. 
     In various embodiments of the present invention, light panel  100  may be water-resistant or waterproof. In various embodiments, light panel  100  may meet IP65, IP66, IP67, or IP68 environmental ratings. (One method for rating different levels of environmental protection is an IP rating as specified by International Protection Marking in International Electrotechnical Commission (IEC) standard 60529, providing classification of degrees of protection provided by enclosures for electrical equipment, the entirety of which is hereby incorporated by reference herein. In general for an IP XY rating, “X” indicates the level of protection for access to electrical parts and ingress to solid foreign objects, while “Y” indicates the level of protection for ingress of harmful water. For example, an IP44 rating provides access and ingress protection for objects greater than about 1 mm and protection from water splashing on the system. In another example, an IP66 rating provides a dust-tight enclosure and protection from water jets incident on the system. Specific details of the requirements and test method are detailed within the IP specification.) In various embodiments, light sheet  110  may be encased or encapsulated in a waterproof or substantially waterproof coating, for example including or consisting essentially of silicone, polyurethane, or the like, as detailed in U.S. patent application Ser. No. 14/301,859, filed on Jun. 11, 2014, the entire disclosure of which is incorporated by reference herein. In various embodiments, the coating may be a conformal coating, for example having a thickness in the range of about 20 μm to about 1000 μm. In various embodiments, light sheet  110  may be potted, encased or encapsulated in a layer of waterproof or substantially waterproof material, for example silicone or polyurethane or the like. 
     In various embodiments of the present invention, a lighting system may include or consist essentially of multiple light panels  100 , as shown in  FIG.  17 A .  FIG.  171    shows six light panels  100 , arranged in a 2×3 array; however, this is not a limitation of the present invention, and in other embodiments other array geometries or layouts may be used. For example, light panels  100  in  FIG.  17 A  are tiled together such that the edges of adjacent light panels  100  meet or are relatively close together, for example such that the LEE pitch between two adjacent light panels  100  (that is the LEE pitch that spans across the edges of two adjacent light panels  100 ) is the same or substantially the same as the LEE pitch within a single light panel  100 . However, this is not a limitation of the present invention, and in other embodiments light panels  100  may be spaced apart, for example in a substantially regular pattern, for example as shown in  FIG.  1713    or in an arbitrary pattern, for example as shown in  FIG.  17 C . Electrical connections between light panels  100  are not shown for clarity in  FIGS.  17 A- 17 C . While  FIGS.  17 A   17 C depict light panels  100 , this is not a limitation of the present invention, and in other embodiments similar configurations may be formed using light sheets  110 . 
     In various embodiments of the present invention, the means for electrical coupling to or between light panels  100  or light sheets  110  may include or consist essentially of a vertical connector, in which the connection mechanism is activated or deactivated by movement of at least one connector component in a direction substantially perpendicular to the surface of the light panel in the region of the connector.  FIG.  18 A  shows one embodiment of a vertical connector that includes or consists essentially of a pin  1810  that mates with a socket  1820 . In various embodiments of the present invention, pin  1810  is electrically coupled and/or mounted on conductive trace  210 . Wire  1830  is electrically coupled to socket  1820  and may be used to provide electrical coupling (i.e., provide electrical power and/or communication and/or control signals) through socket  1820  and pin  1810  to one or more conductive traces  210  disposed over substrate  265 .  FIG.  1813    shows another embodiment of the present invention in which the vertical socket  1820  fits over pin  1810  and a portion of pin  1810  protrudes through and is visible over the socket  1820  when the socket  1820  is in place. Such connectors may include, for example the  400  series connectors available from Bender &amp; Wirth GmbH &amp; Co of Kierspe, Germany. 
       FIG.  18 C  shows another embodiment of the present invention that features a snap connector including or consisting essentially of at least two parts, identified in  FIG.  18 C  as a button  1840  and a button socket  1850 . Button  1840  and button socket  1850  are shown as disengaged in  FIG.  18 C  and engaged in  FIG.  18 D . In some embodiments of the present invention, button  1840  is electrically coupled and/or mounted on a conductive trace  210 . As with the vertical connector shown in  FIG.  18 A , button socket  1850  may be electrically coupled to one or more wires  1830 . In various embodiments, light panels may be electrically coupled by a jumper  1860  between two connectors, as shown in  FIG.  18 D . 
     In various embodiments of the present invention, button socket  1850  may be mounted on or to one light sheet  110 , and button  1840  may be mounted on or to a second light sheet  110 ′, permitting direct connection between two light panels, as shown in  FIG.  18 E . In various embodiments of the present invention, button  1840  and button socket  1850  may be formed on opposite sides of the two light sheets, for example either the button  1840  or button socket  1850  may be mounted on the front surface of one light sheet while the mating connector may be mounted on the back surface of a second light sheet. For example, in the structure shown in  FIG.  18 E , button  1840  is mounted on the front side of light sheet  110  and button socket  1850  is mounted on the back side of light sheet  110 ′. As shown in  FIG.  18 E , a via  1860  electrically couples button socket  1850  to conductive trace  210 ′ through substrate  265 ′. In various embodiments of the present invention, via  1860  may include or consist essentially of a rivet; a staple, a crimp or piercing connector, or the like. In various embodiments of the present invention, button  1840  and button socket  1850  may be formed on the same side of the light sheet; for example, as shown in  FIG.  18 F , button  1840  and button socket  1850  are formed on the same side (e.g., front side) of light sheets  110  and  110 ′, and a portion of light panel  110 ′ is folded over to facilitate connection of button socket  1850  to button  1840 . 
     In various embodiments of the present invention, the snap connector may include or consist essentially of a 9V battery connector. 9V battery connectors have male and, female components, as shown in  FIGS.  18 G and  18 H  respectively. 
     In various embodiments of the present invention, the snap connectors may be electrically coupled to conductive trace  210  and/or mechanically coupled to conductive trace  210  and/or substrate  265  using a variety of means; for example solder, conductive adhesive, anisotropic conductive adhesive, eyelets, rivets, crimp connectors, piercing connectors, or the like. The method of attachment of the snap connectors to a light sheet or light panel is not a limitation of the present invention. 
       FIG.  19 A  shows one embodiment of a light sheet  110  that features LEEs  230  and connectors  1910 ,  1910 ′,  1920 , and  1920 ′ disposed on substrate  265 . Conductive traces providing electrical coupling between LEEs  230  and current control elements and power conductors  1960  and  1970  are not shown for clarity in  FIG.  19 A . In various embodiments of the present invention, connectors  1910 ,  1910 ′,  1920 , and  1920 ′ may include, consist essentially of, or consist of vertical connectors or snap connectors; however, this is not a limitation of the present invention and in other embodiments other forms of connectors may be used. In various embodiments of the present invention, connectors  1910  and  1910 ′ may include or consist essentially of female 9V battery connectors as shown in  FIG.  18 H , and connectors  1920  and  1920 ′ may include or consist essentially of male 9V battery connectors as shown in  FIG.  18 G . In the embodiment shown in  FIG.  19 A , the connectors are all disposed on the same side of light sheet  110 ; however, this is not a limitation of the present invention, and in other embodiments various connectors may be formed on different sides of light sheet  110 , for example as discussed in reference to  FIG.  18 E . 
     In various embodiments, the connectors may be used to provide power to the light sheet. For example, in various embodiments of the present invention, power to light sheet  110  may be provided through connectors  1910 ′ and  1920 ′. For example, in various embodiments, connector  1910 ′ may be used for the positive power supply connection and connector  1920 ′ may be used for the negative or ground power supply connection; however, this is not a limitation of the present invention, and in other embodiments other configurations for powering the light sheet may be utilized. 
     In various embodiments of the present invention, for example as shown in  FIG.  19 A , connectors  1920 ′ and  1910  may be electrically coupled together by an electrical trace  1960  (shown in  FIG.  19 A  as a dashed line), and connectors  1910 ′ and  1920  may be electrically coupled together by a conductive trace  1970  (shown in  FIG.  19 A  as a dashed line). In various embodiments of the present invention, multiple light sheets  110  may be electrically coupled together, for example by connecting connector  1910  on a first light sheet to connector  1920 ′ on a second light sheet and by connecting connector  1920  on a first light sheet to connector  1910 ′ on a second light sheet. 
     In various embodiments of the present invention, one or more connectors may be positioned on a tab extending out from the main portion of the light sheet, for example tab  1930  as shown in  FIG.  19 A . In various embodiments of the present invention, a portion of tab  1930  may be folded over (see, e.g., folded portion  1931  in  FIG.  19 B ), for example as discussed in reference to  FIG.  18 F , to facilitate connection to another light sheet.  FIG.  19 B  shows a schematic of a portion of a tab  1930  containing connector  1920  disposed on a partially folded-over portion  1931 , while  FIG.  19 C  shows a schematic of a portion of tab  1930  containing connector  1920  in a completely or substantially completely folded-over position. In various embodiments of the present invention, the folded-over portion may be held in place by an adhesive, glue, tape or the like, for example adhesive  1980  in  FIG.  19 B , In various embodiments of the present invention, a portion of connector  1920  may extend through a portion of folded portion  1931  or portions of both tab  1930  and folded portion  1931 .  FIG.  19 D  shows an example of an embodiment of the present invention featuring light sheet  110  having a tab  1930  with a portion  1931  folded over prior to the connector being disposed on the sheet. In this example, the connector includes or consists essentially of two parts, identified as a back connector part  1921  and a front connector part  1922 , which are mated through a hole  1923 . In this example, hole  1923  is formed through both tab  1930  and the folded over portion of tab  1931  prior to completing formation of the connector. However, this is not a limitation of the present invention, and in other embodiments, one or both of back connector part  1921  and front connector part  1922  may pierce or otherwise form a hole in tab  1930  and/or folded portion of the tab  1931  during placement of the connector. In the example shown in  FIG.  19 D , mating of back connector part  1921  and front connector part  1922  may include mechanically bringing the two parts together and deforming a portion of one or both connector parts to bind the two portions together. The structure of the connector and/or the method of forming a connector from two or more connector parts are not limitations of the present invention. 
     In various embodiments of the present invention, a folded portion  1990  of the light sheet may be folded over, for example as shown in  FIG.  19 E . In various embodiments, all or a portion of power conductor  210  or  220 , for example as shown in  FIG.  2 C , may be disposed on or in the folded portion  1990 . In various embodiments, the placement of all or a portion of power conductor  210  or  220  on folded portion  1990  may be used to decrease the resistance per unit length of the power conductor, for a given width light sheet, by increasing the effective width of power conductor  210  or  220 . As shown in  FIG.  19 E , light sheet  100  has a width  1992 , not including folded portions  1990 . Folded portions  1990  each have a width  1997 .  FIG.  19 F  shows a detailed schematic of a portion of light sheet  110 , showing a comparison of light sheet  110  with and without a folded portion  1990 . Light sheet  110  without folded portion  1990  has power conductor  210  having a width  1994 . Light sheet  110  with folded portion  1990  has power conductor  210 ′ having an additional width  1996 , for a total width equal to the sum of width  1994  and width  1996 . For a power conductor  210  having a substantially constant thickness and resistivity, the resistance per unit length is inversely proportional to the width of power conductor  210 . For the example shown in  FIG.  19 E , the conductance of power conductor  210 ′ (including portions  1994  and  1996 ) is ( 1994 + 1996 )/ 1994  times that of power conductor  210  (having width  1994 ). In various embodiments of the present invention, folded portion  1990  may have a width  1996  in the range of about 2 ram to about 50 mm. In various embodiments of the present invention, power conductor  210  may have a width of  1994  of about 3 mm and power conductor  210 ′ may have a width ( 1994 + 1996 ) of about 9 mm, resulting in power conductor  210 ′ having a resistance about 3× lower than that of power conductor  210 . In various embodiments of the present invention, power conductor  210 ′ may have a resistance in the range of about 1.5 to about 10 times lower than that of power conductor  210 . While  FIG.  19 F  shows one folded portion  1990 , this is not a limitation of the present invention, and in other embodiments light sheet  110  may have multiple folded portions. For example  FIG.  19 G  shows light sheet  110  having two folded portions  1990  and  1990 ′. However, this is not a limitation of the present invention, and in other embodiments light sheet  110  may have more than two folded portions. While  FIG.  19 G  shows the folds in a fan-fold configuration, this is not a limitation of the present invention and in other embodiments the folding configuration may be different. For example in various embodiments the folds may be rolled-over or folded over, as shown in  FIG.  19 I , or may have other fold configurations or combinations of configurations. In various embodiments, the folded portions or parts of the folded portions may be adhered or fastened to each other or to the unfolded part of the light sheet, for example using glue, adhesive, tape, lamination, staples, rivets, or the like. 
     In various embodiments of the present invention, light sheets  110  having folded portions  1990  may be combined with frame elements, for example frame elements  120 ,  120 ′. In various embodiments of the present invention, folded portion  1990  of light sheet  110  may be folded or wrapped around a portion of frame element  120  or  120 ′ as shown in  FIG.  19 H ; however, this is not a limitation of the present invention, and in other embodiments folded portion  1990  of light sheet  110  may be disposed under or over frame element  120 ,  120 ′, or light sheet  110  with one or more folded portions  1990  may be utilized without any frame elements. 
     In various embodiments of the present invention, a portion of light sheet  110  may be adhered or attached to frame  120  or to a portion of frame  120 , for example using adhesive, glue, tape, double-sided tape, or the like. For example, in various embodiments a portion of light sheet  110  may be adhered to a portion of frame  120 , for example all, substantially all or a portion of the top and/or the bottom and/or the sides of frame  120  may be adhered to light sheet  110 . In various embodiments of the present invention, a lighting system may include or consist essentially of an assemblage of multiple light sheets  110  and/or light panels  100  and an associated connector system. In various embodiments of the present invention, the connector system utilizes the same type of connectors, or snap connectors or 9V battery connectors that are used on light sheets  110  and/or light panels  100 . 
     While  FIG.  19 F  shows portions  1994  and  1996  having the same or substantially the same shape, this is not a limitation of the present invention, and in other embodiments they may have different shapes. For example,  FIG.  19 J  shows an example of an embodiment of the present invention in which portion  1994  has a different shape than that of portion  1996 . While  FIG.  19 F  shows portions  1994  and  1996  as one contiguous area, this is not a limitation of the present invention, and in other embodiments portions  1994  and  1996  may have one or more spaces between them or gaps  1997  (areas not containing the electrically conductive trace material) in them, for example as shown in  FIGS.  19 K and  19 L . 
     In various embodiments the light panel, for example as shown schematically in  FIGS.  1 A,  2 B,  19 H , and other figures herein, may have a thickness in the range of about 0.25 mm to about 20 mm, or in the range of about 0.4 mm to about 5 mm. 
       FIGS.  20 A and  20 B  show two types of light sheets or light panels  2010  and  2020 , respectively, in accordance with embodiments of the present invention. Panel  2010  has tabs  1930 , each of which has a connector disposed thereon. Panel  2020  does not have tabs  1930 , and the connectors are disposed on the main panel body of the light panel or light sheet (e.g., near the periphery and/or corners of the panel or sheet). In this embodiment of the present invention, the connector system includes or consists essentially of two mating connectors  2030  and  2040 . (Physically similar or identical connectors, but formed in different locations on the light sheet or light panel are identified by one or more apostrophes, for example  2030  and  2030 ′ are the same physical type of connector, but disposed in different locations on the light sheet or light panel.) Connectors  2030  and  2040  mate to each other and in some embodiments of the present invention are polarized (e.g., one connector is male and the other is female) to prevent misconnection of the light panels or light sheets. However, this is not a limitation of the present invention, and in other embodiments connectors  2030  and  2040  may not be polarized. In the schematics of  FIGS.  20 A- 20 C , connectors  2030  are identified by the grey filled-in circles, and connectors  2040  are identified by the white filled-in circles. In various embodiments of the present invention, when multiple light sheets or light panels are connected, connector  2040  is electrically coupled to connector  2030 ′ and connector  2030  is electrically coupled to connector  2040 ′, for example as discussed in reference to  FIG.  19 A . This permits multiple light panels or light sheets to be electrically coupled through these connectors, for example as discussed in reference to  FIG.  20 C  below. 
     In various embodiments of the present invention, other connector configurations may be utilized, for example a portion of one sheet may overlap a portion of an adjacent sheet to permit alignment and mating of the electrical connectors. In various embodiments of the present invention, the electrical connectors may be mated by coupling in a direction parallel to or substantially parallel to the surface of the light sheet. 
       FIG.  20 C  shows an embodiment of a lighting system of the present invention that is partially assembled, and that includes or consists essentially of three panels  2010 ,  2010 ′, and  2010 ″ and one panel  2020 . Panels  2010 ′ and  2010 ″ have been electrically coupled together. Panel  2010  is awaiting assembly, which is completed by connecting connector  2040 ′ on panel  2010  to connector  2030 ′ on panel  2010 ′ and connecting connector  2030  on panel  2010  to connector  2040  on panel  2010 ′. Panel  2020  is awaiting assembly into the lighting system, which is completed using jumpers  2050 ,  2050 ′ (jumper  2050 ′ has already been connected) by connecting connector  2030 ′″ on jumper  2050  to connector  2040 ″ on panel  2010 ″ and connecting connector  2040 ′ on jumper  2050  to connector  2030 ″ on panel  2020 . Jumper  2050  may have any length and may be straight, as shown in  FIG.  20 C , or may be curved or have any shape. While jumper  2050  is shown in  FIG.  20 C  as connecting a  2010 -type panel to a  2020 -type panel, this is not a limitation of the present invention, and in other embodiments one or more jumpers  2050  may connect two  2010 -type panels (i.e., panels having one or more protruding tabs) or two  2020 -type panels (i.e., panels lacking protruding tabs) or any other style or configuration of panels. In various embodiments of the present invention, the connectors on the left side (top and bottom) of each light sheet or light panel are electrically coupled together and the connectors on the right side (top and bottom) of each light sheet or light panel are electrically coupled together, permitting multiple light sheets or light panels to be powered by connection from one end of the array of light panels or light sheets (i.e., from one end of the assembled lighting system). The order of assembly of the components with reference to  FIG.  20 C  (including but not limited to light sheets, light panels, and jumpers) is one example of how these components may be assembled. In other embodiments of the present invention, the assembly order may be different and/or other components may be utilized. 
     In various embodiments of the present invention, jumper  2050  may be constructed in a similar fashion to the light panel, while in other embodiments, jumper  2050  may have a different construction from that of the light panel. In various embodiments of the present invention, jumper  2050  may include or consist essentially of one or more wires or wire harnesses with connectors. In various embodiments of the present invention, jumper  2050  may include or consist essentially of a flexible substrate having conductive traces disposed on the substrate and connectors electrically coupled to the conductive traces (i.e., in the style of light sheets as described herein). 
     In various embodiments of the present invention, a light sheet or light panel may have one or more connector wires directly attached to one or more power conductors or other conductive elements. In such embodiments, the other end of the wire (the end not electrically coupled to a portion of the light sheet or light panel) may be a flying lead, i.e., just the wire, or may be terminated with a connector, or may be integrated into a wiring harness, or may be contacted by other means. 
     In various embodiments of the present invention, jumpers may be used to electrically couple one or more light panels or light sheets to a power bus or power supply.  FIG.  21 A  shows a lighting system including or consisting essentially of nine light panels or light sheets  2010 . The nine light panels have been connected into three vertically oriented groups of three panels each, and the system is ready for connection to a power supply. While the system of  FIG.  21 A  shows a lighting system including or consisting essentially of nine light sheets or light panels, this is not a limitation of the present invention, and in other embodiments the lighting system may have fewer or more light sheets or light panels. 
     In various embodiments of the present invention, a power bus or power wiring harness  2110  may include or consist essentially of one or more power conductors, for example power conductors  2120  and  2130 , and one or more connectors, for example connectors  2030 ′″ and  2040 ′″ (other connectors are shown in  FIG.  21 A , but not identified with separate identification numbers). In various embodiments, connector  2030 ′ is electrically coupled to power conductor  2120  and connector  2040 ′″ is electrically coupled to power conductor  2030  (other connectors are shown as electrically coupled, but not identified in  FIG.  21 A  with separate identification numbers). To continue assembly of the lighting system, connector  2030 ′″ on power bus  2110  is connected to connector  2040  on jumper  2050 ′, connector  2040 ′″ on power bus  2110  is electrically connected to connector  2030  on jumper  2050 , connector  2030 ′ on jumper  2050 ′ is electrically connected to connector  2040 ″ on panel  2010 ′, and connector  2040 ′ on jumper  2050  is electrically connected to connector  2040 ″ on panel  2010 ′. While the system shown in  FIG.  21 A  uses light panels or light sheets with protruding tabs, this is not a limitation of the present invention, and in other embodiments tab-less panels may be used or a mixture tabbed and tab-less panels may be used, or any other type or style of light sheets or panels may be used. While the system shown in  FIG.  21 A  shows panels  2010  as close coupled, i.e., all of the panels are connected together with relatively little space between each panel, both in the horizontal and vertical directions, this is not a limitation of the present invention, and in other embodiments, additional space between adjacent panels, for example in the horizontal direction or vertical direction or both directions may be part of the present invention. 
     In various embodiments of the present invention, the light sheets or light panels are configured and positioned such that the distance between adjacent LEEs between adjacent light sheets or light panels is the same or substantially the same as the distance between adjacent LEEs on one light sheet or light panel, i.e., the pitch between LEEs on a light panel or light sheet is the same or substantially the same as the pitch between adjacent LEEs across the joint or interface between two adjacent light sheets or light panels. In various embodiments of the present invention, the lighting system includes or consists essentially of multiple light panels or light sheets and the pitch or distance between adjacent LEEs is the same, independent of whether the LEEs are on one light sheet or light panel or on separate light panels or light sheets. In various embodiments of the present invention, the LEEs are spaced in a rectangular array on the light sheet or light panel with a first pitch in a first direction and a second pitch in a second direction that is substantially perpendicular to the first direction, and the system includes or consists essentially of multiple light sheets or light panels, and the pitch in the first direction between adjacent light sheets is the same as the first pitch on the light sheet or light panel, and the pitch in the second direction between adjacent light sheets is the same as the second pitch on the light sheet or light panel. For example, in various embodiments, the pitch between all LEEs in a system including multiple light panels, for example the system shown in  FIG.  21 A , is the same or substantially the same. 
     While the lighting system shown in  FIG.  21 A  includes nine light panels or light sheets  2010 , this is not a limitation of the present invention, and in other embodiments fewer or more light panels and/or light sheets  2010  may be utilized. In various embodiments of the present invention, a lighting system may include or consist essentially of at least 50 light panels and/or light sheets, or at least 100 light panels and/or light sheets, or at least 500 light sheets and/or light panels, or at least 5000 light sheets and/or light panels 
       FIG.  21 B  shows an embodiment of a lighting system of the present invention similar to that of the lighting system of  FIG.  21 A ; however, in the system of  FIG.  21 B , power bus or power wiring harness  2111  differs from power bus or power wiring harness  2110  by elimination of jumpers  2050 . Jumpers  2050  are replaced by tabs or extensions  2140  on which are disposed the connectors that connect to a connector on a light sheet or light panel. In various embodiments of the present invention, tabs or extensions  2140  may each include one connector; however, this is not a limitation of the present invention, and in other embodiments a tab or extension  2140  may include more than one connector, as shown by tab or extension  2150 . While tab or extension  2150  includes two connectors, this is not a limitation of the present invention, and in other embodiments tab or extension  2150  may include more than two connectors. In various embodiments of the present invention, power bus or power wiring harness  2111  does not include tabs or extensions  2140  or  2150 , and the connectors are formed on the body of power bus or power wiring harness  2111 , as shown in  FIG.  21 C . In various embodiments of the present invention the power bus or power wiring harness includes or consists essentially of one or more wires, optionally bundled together with connectors wired to the main power lines in the power bus. 
     In various embodiments of the present invention, the connectors on the left side (top and bottom) of each light sheet or light panel are electrically coupled together and the connectors on the right side (top and bottom) of each light sheet or light panel are electrically coupled together, permitting multiple light sheets or light panels to be powered by connection from one end of the array of light panels or light sheets. For example, in the lighting system of  FIG.  21 B , a power supply  2170  provides power through power bus  2111  to the bottom three light panels. This power is then conveyed through the bottom light sheet or light panel to the light sheet or light panel to which it is electrically coupled, and so on. For example, light panel  2010  is powered from power bus  2111 , light panel  2010 ′ is provided power from light panel  2010 , and light panel  2010 ″ is provided power from light panel  2010 ′. In various embodiments of the present invention, this permits powering or energizing of large linear assemblies of light panels or light sheets with only one power connection, and in some embodiments from only one end of the assembly. In various embodiments of the present invention, different configurations of connection of two or more connectors may be utilized. 
     In the example in  FIG.  21 B , power bus  2111  is electrically coupled to power supply  2170 . In various embodiments of the present invention, power supply  2170  provides power to energize light panels  2010 . In various embodiments of the present invention, power supply  2170  provides a constant voltage power to power bus  2111 ; however, this is not a limitation of the present invention, and in other embodiments power supply  2170  may provide constant current, AC-based power, or any other type of power. In various embodiments of the present invention, power supply  2170  is energized from a mains power supply, for example an AC mains power source; however, this is not a limitation of the present invention, and in other embodiments power supply  2170  may be energized from a battery or batteries, rechargeable battery or batteries, photovoltaic generation systems, wind generation systems, gas or other fuel based generator systems, energy harvesting systems, another power supply, or other power sources. In various embodiments of the present invention, power supply  2170  may provide a constant voltage that is modulated, for example using pulse-width modulation (PWM), to permit dimming of light-emitting elements on light panels  2010 ; however, this is not a limitation of the present invention, and in other embodiments dimming may be accomplished by other means, for example by modification of the current to each light panel, modification of the voltage to each light panel, or by other means. 
     In various embodiments of the present invention, a power bus or power wiring harness  2111  or  2112  may also support control or communication signals to the light sheets or light panels, or from the light sheets or light panels, for example to provide control and/or communication signals between a power source, for example power supply  2170  and light panels  2010 . In various embodiments, control or communication signals may be used to selectively energize or de-energize individual or groups of light panels or light sheets in a lighting system, or to selectively energize or de-energize portions of individual or groups of light panels or light sheets or to modify the intensity of light emitted by individual or groups of light panels or light sheets in a system, or to modify the intensity of light emitted by portions of individual or groups of light panels or light sheets, or to modify other optical characteristics of individual or groups of light panels or light sheets or portions of individual or groups of light panels or light sheets, for example correlated color temperature (CCI), color rendering index (CRI), R9, spectral power distribution, light distribution pattern, or the like. 
       FIG.  21 C  shows an embodiment of the present invention in which a power bus or power wiring harness  2112  without tabs or extensions  2140  or  2150  is connected to light panels or light sheets  2010 . In the lighting system of  FIG.  21 C , the vertical columns of light panels or light sheets are spaced apart from each other, in contrast to the system of  FIG.  2111   , in which the light panels or light sheets are positioned substantially next to each other. Furthermore, in the system of  FIG.  21 C , power bus or power wiring harness  2112  extends beyond the limits of the figure, and may provide power to one or more additional groups of light sheets or light panels. The number of groups of light sheets or light panels powered by the power bus or power wiring harness is not a limitation of the present invention. 
       FIG.  21 D  shows a schematic of another embodiment of the present invention in which power is supplied to multiple columns of light panels or light sheets from one end of the assembly. Power supply  2170  supplies power to light sheet  2010 , which provides power to light sheet  2010 ′. Power is then conveyed from light sheet  2010 ′ through power bus  2112  to light sheet  2010 ″, which provides power to light sheet  2010 ′″. Power is then conveyed from light sheet  2010 ′″ through power bus  2113  to the next array of light sheets (not shown). 
       FIG.  21 E  shows a schematic of another embodiment of the present invention in which the connectors are grouped on one tab, with each tab having multiple connectors. For example, power bus  2111  has one tab connecting to each light panel, for example tab  2141  connecting to panel  2010 . In various embodiments, one tab may include two or more connectors, while in other embodiments each connector may include or consist essentially of multiple separate electrical conductors. 
     Power buses or power wiring harnesses may incorporate one or more tabs or no tabs, and various types of power buses or power wiring harnesses as well as combinations of various types of power buses or power wiring harnesses are within the scope of this invention. 
     While the systems shown in  FIGS.  19 A,  19 H,  20 A- 20 C, and  21 A- 21 C  depict substantially square light panels or light sheets, this is not a limitation of the present invention, and in other embodiments light panels or light sheets may have other shapes, for example rectangular, hexagonal, triangular, parallelogram, or any arbitrary shape. While  FIGS.  21 A- 21 C  show square arrays of light sheets or light panels, this is not a limitation of the present invention, and in other embodiments the light sheets or light panels may be configured or positioned in a rectangular array, a hexagonal array, a triangular array, or any other array, whether periodic or not. 
       FIG.  21 F  shows an embodiment of a lighting system of the present invention including or consisting essentially of light panels  2010  attached to a support  2190  and covered or partially covered by an optic  2185  (the details of support  2190  and of optic  2185  are not shown for clarity, nor are they limitations of the present invention). As shown in  FIG.  21 F , optic  2185  is spaced apart from light panels  2010  by a spacing  2180 . In various embodiments of the present invention, optic  2185  may be in contact with light panel  2010  or substantially in contact with light panel  2010 , while in other embodiments optic  2185  may be in contact or substantially in contact with the LEEs on light panel  2010 , or may be spaced apart from light panel  2010  as shown in  FIG.  21 F . In various embodiments of the present invention, spacing  2180  may be in the range of about 0.5× to about 5×, or in the range of about 1× to about 2×, the spacing or pitch of LEEs on light panel  2010 . In various embodiments of the present invention, spacing  2180  may be in the range of about 5 mm to about 500 mm, or in the range of about 10 mm to about 100 mm. In various embodiments of the present invention, support  2190  may include or consist essentially of a wall, ceiling, floor, column, sub-structure, substrate, or other feature to which light panel or panels  2010  may be attached or mounted. In various embodiments of the present invention, optic  2185  may include or consist essentially of a lens, a diffuser, a refractive optic, a reflective optic, a Fresnel optic, a fabric, a translucent material such as plastic or stone, a graphic panel, a membrane or the like. In various embodiments of the present invention, optic  2185  may include or consist essentially of a plurality of optical elements, for example as described in U.S. patent application Ser. No. 13/693,632, filed on Dec. 4, 2012, the entire disclosure of which is incorporated by reference herein. In various embodiments of the present invention, optic  2185  may include or consist essentially of glass, stone, plastic, fabric, foam, paper, or the like. 
     In various embodiments of the present invention, the total thickness  2181  of the lighting system shown in  FIG.  21 F , i.e., the distance between the back of light panel  2010  to the front of optic  2185 , may be in the range of about 1× to about 5× the spacing or pitch of LEEs on light panel  2010 , or in the range of about 1.5× to about 4× the spacing or pitch of LEEs on light panel  2010 . In various embodiments of the present invention, a total thickness  2181  of the lighting system shown in  FIG.  21 F  may be in the range of about 1 cm to about 10 cm, or in the range of about 1.5 cm to about 5 cm. 
     As described herein, various embodiments of the present invention include columnar arrays of light panels in which each light panel includes power conductors that provide power to the light-emitting elements of each panel and also provide a means of transmitting power to adjacent light panels within the columns. In various embodiments of the present invention, multiple columns may be positioned next to each other, for example adjacent to but spaced apart from the adjacent column, or adjacent to and in contact with the adjacent column, to create very large illuminated surfaces or arrays. In various embodiments of the present invention; one or more columns of light panels may be energized from a power bus system electrically coupled to one or both ends of the column of light panels. 
     While the systems shown in  FIGS.  19 A,  19 H,  20 A- 20 C, and  21 A- 21 C  depict substantially square light panels or light sheets, this is not a limitation of the present invention, and in other embodiments light panels or light sheets may have other shapes, for example rectangular, hexagonal, triangular, parallelogram, or any arbitrary shape. While  FIGS.  21 A- 21 C  show square arrays of light sheets or light panels, this is not a limitation of the present invention, and in other embodiments the light sheets or light panels may be configured or positioned in a rectangular array, a hexagonal array, a triangular array, or any other array, whether periodic or not. For example,  FIG.  22 A  shows a schematic of another embodiment of the present invention that includes three different shaped light panels. Specifically, light panels  2010  and  2010 ′ have one shape, light panels  2010 ′ have a second shape, and light panel  2010 ′ has a third shape. In the example shown in  FIG.  22 A , light panels  2010 ,  2010 ′,  2020 ′″, and  2010 ″″ are all rectangular; however, this is not a limitation of the present invention, and in other embodiments the light panels may have other shapes. For example,  FIG.  22 B  shows an exemplary embodiment of the present invention similar to that of  FIG.  22 A , in which light panel  2010 ″″ is replaced by a light panel  2220  having a curved edge  2221 . 
     In various embodiments, each light panel may have a closed surface, i.e., a surface that does not define any holes or apertures within it; however, this is not a limitation of the present invention, and in other embodiments one or more light panels may define one or more openings or holes therein or therethrough. For example, a light panel may include a hole such that other elements or features of the surface may extend through the light panel surface, for example a head for a fire suppression system (for example a water sprinkler head, a chemical extinguisher dispenser head, or the like), a smoke or fire sensor or detector, a duct or vent for heating, air conditioning and ventilation (HVAC), an antenna or receiver for various one or two-way communication systems, a camera (for example, a video or still surveillance camera), a power outlet, a light source (for example, a spot light or down light to provide localized light), a stand-off or other support element for a diffuser, optic, or other material positioned in front of the light panel, a structural or other element that is part of the surface on which the light panel is mounted, or any element which is desired to protrude through the light panel.  FIG.  22 B  shows an example of a light panel  2030  defining a through-hole  2031  through the light panel  2030 . While  FIG.  22 B  shows hole  2031  having a circular or substantially circular shape, this is not a limitation of the present invention, and in other embodiments hole  2031  may be square, rectangular, hexagonal, octagonal or have any arbitrary shape and/or size. While  FIG.  22 B  shows light panel  2030  having one hole  2031 , this is not a limitation of the present invention, and in other embodiments a light panel may define more than one hole  2031 . While  FIG.  22 B  shows the lighting system having one light panel with a hole, this is not a limitation of the present invention, and in other embodiments a lighting system may include multiple light panels, with one or more light panels defining one or more holes. 
     In various embodiments, the shapes of light panels such as light panels  2010 ,  2010 ′,  2020 ′″, and  2010 ″″ may be pre-determined, for example they may be manufactured to one or more specific sizes, and a system may include multiple light panels, each having the same size and shape, or some or all light panels may have different shapes and sizes. In various embodiments, these light panels of one or more shape and size may be assembled together to achieve the final desired shape and size, while in other embodiments one or more light panels may be cuttable or separable in one or more directions to permit formation of assemblies of panels of different sizes and shapes by removal of a portion of a panel, for example as described in U.S. patent application Ser. No. 13/799,807, filed on Mar. 13, 2013, U.S. patent application Ser. No. 13/970,027, filed on Aug. 19, 2013, U.S. patent application Ser. No. 15/182,700, filed on Jun. 15, 2016, and U.S. patent application Ser. No. 15/182,704, filed on Jun. 15, 2016, the entire disclosure of each of which is incorporated by reference herein. 
     In various embodiments of the present invention, control signals and/or communication signals may be carried over one or more electrical conductors separate from power conductors  2120  and  2130 . For example,  FIG.  23 A  shows an example of an embodiment of the present invention in which power bus  2111  includes a control conductor  2310  as well as power conductors  2120  and  2130 . Similar to the distribution of power throughout a system of light panels described herein, control and/or communication signals may be distributed through all or a portion of a system of light panels over control conductor  2310 , which may electrically couple to one or more electrical lines or conductors disposed on or in one or more of the light panels in the lighting system. While  FIG.  23 A  shows one control conductor  2310 , this is not a limitation of the present invention, and in other embodiments more than one control conductor  2310  may be utilized. In various embodiments, a control or communication signal or signals may be transmitted to the light panels via control conductor  2310 . For example, in various embodiments control or communication signal  2320  may be sent over control conductor  2310  as shown in  FIG.  23 A , In various embodiments of the present invention, control or communication signal  2320  may be applied directly to control conductor  2310 , as shown in  FIG.  23 A ; however, this is not a limitation of the present invention, and in other embodiments control or communication signal  2320  may be applied to power supply  2170  and then to control conductor  2310  through power supply  2170 . In various embodiments, control or communication signal  2320  may be provided to control conductor  2310  through a wireless system, for example a radio- or light-transmission-based system. In various embodiments, control or communication signal  2320  may include, consist essentially of, or consist of one or more of a voltage or current signal (for example a 0-10 V signal), a modulated signal (for example a pulse-width-modulated signal), a digital signal, an analog signal, a signal based on various protocols used in the lighting and/or building industry (for example DALI, DMX, BacNET), and the like. The specific communication or control signal protocol is not a limitation of the present invention. 
     In various embodiments of the present invention, the lighting system may include or consist essentially of one or more master light panels  2350  and one or more slave light panels  2350 ′. In various embodiments of the present invention, one or more slave light panels  2350 ′ may be electrically coupled to one master light panel  2350  as detailed herein. In various embodiments of the present invention, master light panel  2350  may include one or more control or communication modules, for example capable of receiving a control or communication signal and modifying a characteristic of the master light panel  2350  and any slave light panels  2350 ′ that are electrically coupled to master light panel  2350 . For example, the control signal may represent (and/or direct a change in) a light intensity, a color, for example a CCT, a CRI, R9, spectral power distribution, spatial light distribution pattern, or the like. For example, in reference to the system of  FIG.  23 A , master light panel  2350  may include a communication or control module (or “controller,” not shown in  FIG.  23 A  for clarity) electrically coupled to control or communication line  2130 . For example as shown in  FIG.  23 A , control or communication line  2130  may be electrically coupled to master light panel  2350  through one or more snap connectors  2360 ; however, this is not a limitation of the present invention, and in other embodiments control or communication line  2130  line may be electrically coupled to master light panel  2350  by other means, for example by a wireless system (e.g., a wireless receiver incorporated onto the master light panel  2350 ). In various embodiments of the present invention, control or communication signal  2320  may incorporate and/or be configured for one-way or two-way transmission. For example, in a one-way transmission system control signals may be passed to the light panels, and in a two-way transmission system not only may control signals be passed to the light panels, but information may be transmitted from the light panels back to a control system and/or to the power bus  2111 . In various embodiments, such information may include data on light panel status, for example operational time, light panel operating status, or may also include other signals for example from sensors, for example signals from sensors such as fire, smoke, temperature, occupancy, light intensity (for example for daylight harvesting), light color or other parameters related to light panel operation or information about the ambient environment. In exemplary embodiments, the controller on master light panel  2350  may incorporate a wireless transmission system to communicate the information, and/or other transmission circuitry to communicate the information on communication line  2130 . 
     The control system (or “controller”) in accordance with embodiments of the present invention may include or consist essentially of a general-purpose computing device in the form of a computer including a processing unit (or “computer processor”), a system memory, and a system bus that couples various system components including the system memory to the processing unit. Computers typically include a variety of computer-readable media that can form part of the system memory and be read by the processing unit. By way of example, and not limitation, computer readable media may include computer storage media and/or communication media. The system memory may include computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements, such as during start-up, is typically stored in ROM. RAM typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit. The data or program modules may include an operating system, application programs, other program modules, and program data. The operating system may be or include a variety of operating systems such as Microsoft WINDOWS operating system, the Unix operating system, the Linux operating system, the Xenix operating system, the IBM AIX operating system, the Hewlett Packard UX operating system, the Novell NETWARE operating system, the Sun Microsystems SOLARIS operating system, the OS/2 operating system, the BeOS operating system, the MACINTOSH operating system, the APACHE operating system, an OPENSTEP operating system or another operating system of platform. 
     Any suitable programming language may be used to implement without undue experimentation the functions described herein. Illustratively, the programming language used may include assembly language, Ada, APL, Basic, C, C++, C*, COBOL, dBase, Forth, FORTRAN, Java, Modula-2, Pascal, Prolog, Python, REXX, Matlab, Labview, R, and/or JavaScript for example. Further, it is not necessary that a single type of instruction or programming language be utilized in conjunction with the operation of systems and techniques of the invention. Rather, any number of different programming languages may be utilized as is necessary or desirable. 
     The computing environment may also include other removable/nonremovable, volatile/nonvolatile computer storage media. For example, a hard disk drive may read or write to nonremovable, nonvolatile magnetic media. A magnetic disk drive may read from or write to a removable, nonvolatile magnetic disk, and an optical disk drive may read from or write to a removable, nonvolatile optical disk such as a CD-ROM or other optical media. Other removable/nonremovable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The storage media are typically connected to the system bus through a removable or non-removable memory interface. 
     The processing unit that executes commands and instructions may be a general-purpose computer processor, but may utilize any of a wide variety of other technologies including special-purpose hardware, a microcomputer, mini-computer, mainframe computer, programmed micro-processor, micro-controller, peripheral integrated circuit element, a. CSIC (Customer Specific Integrated Circuit), ASIC (Application Specific Integrated Circuit), a logic circuit, a digital signal processor, a programmable logic device such as an FPGA (Field Programmable Gate Array), PLD (Programmable Logic Device), PLA (Programmable Logic Array), MD processor, smart chip, or any other device or arrangement of devices that is capable of implementing the steps of the processes of embodiments of the invention. 
     In various embodiments, the control or communication signal may be distributed to all light panels in the lighting system, for example in a similar fashion to power transmission from panel to panel as described herein. For example,  FIG.  23 B  shows an exemplary system having three connectors on the side of each light panel, in which two are utilized for power transmission and one is utilized for a communication and/or control signal or signals. In  FIG.  23 B , power from power conductors  2120  and  2130  is supplied through jumpers  2140  and  2150 , respectively, to light panel  2370 , while control or communication signal  2310  is supplied through jumper  2360  to light panel  2370 . One or more (or even all) of the light panel  2370  may have three connectors on one or more sides, two for power and one for control/communication, and the control/communication signal is distributed to all sheets using a control/communication conductor on each sheet. For example, communication and control line  2310  may be electrically coupled through jumper  2360  to a connector  2380  (e.g., a snap connector or other vertical connector) on light sheet  2370 . Light sheet  2370  has a control conductor  2382 , shown as a dashed line, that electrically couples control line  2310  to connector  2384  and thus to the light panel attached to connector  2384 . In various embodiments, control conductor  2382  may have the same configuration as power conductors  210  and  220  on light panel  110 ; for example, control conductor  2382  may include or consist essentially of a conductive trace disposed on, over, or within the substrate of light panel  110 . In various embodiments of the present invention, a control or communication module may be included on or as a portion of light panel  2370 , which may utilize one or more signals from communication conductor  2380  to control operation of light panel  2370  or provide information regarding the status of light panel  2370  or any associated sensors or other connected elements. While  FIGS.  23 A and  23 B  show control or communication signal  2320  being transmitted on one wire or conductor  2310 , this is not a limitation of the present invention, and in other embodiments more than one wire or conductor  2310  may be utilized. In various embodiments, multiple conductor control lines  2310  may be coupled to multiple connectors or jumpers  2360  or to one connector having multiple contacts. 
     In various embodiments of the present invention, power bus or power wiring harness  2111  may include a substrate similar to that of substrate  265  used for light sheet or light panel  110 , e.g., a flexible planar substrate having one or more conductive traces and/or other elements defined thereon. In various embodiments of the present invention, power conductors  2120  and  2130  may each include or consist essentially of one or more conductive traces formed over or disposed over or on the substrate. In various embodiments of the present invention, the connectors on the power bus may include, consist essentially of, or consist of one or more snap connectors or other vertical connectors, for example a 9 volt battery connector or a pin connector, similar to the connectors on light sheet  110 , In various embodiments of the present invention, the power bus may have a thickness less than about 5 mm or less than about 2 mm or less than about 1 mm. 
     In various embodiments, control conductor  2382  may electrically couple to one or more control connectors  2383  (e.g., portions of a control system on the light panel) configured to provide connection to control conductor  2382 , for example to permit access to control conductor  2382 . In various embodiments, control conductor  2382  may be an electrical control conductor  2382 , and one or more control connectors  2383  may be electrically coupled to control conductor  2382 . In various embodiments, control connector  2383  may provide access to communication or control signals transmitted on control conductor  2382 . In various embodiments, one or more sensor devices, for example smoke sensors, fire sensors, occupancy sensor, light sensors, heat sensors, humidity sensors, pressure sensors or the like may be connected to control conductor  2382  through control connector  2383 . In various embodiments, one or more devices, for example still cameras, video cameras, speakers, microphones, or other devices may be connected to control conductor  2382  through control connector  2383 . In various embodiments, control conductor  2382  may provide for a network configuration, permitting access, control, and communication to a wide variety of networked sensors or other networked devices. In various embodiments, such a network may utilize Ethernet protocol, DALI, DMX or other protocols; the network protocol s not a limitation of the present invention. While  FIG.  23 B  shows one control connector  2383  on light panel  2370 , this is not a limitation of the present invention, and in other embodiments more than one control connector  2383  may be connected to control conductor  2382 , either on one light panel, for example light panel  2370 , or on multiple different light panels. 
     In various embodiments, a receiver, transmitter, or combination of a receiver and transmitter (e.g., a transceiver) may be electrically coupled to control conductor  2382 . Such a device may be configured to transmit and/or receive signals from various other devices, for example, computers, tablets, mobile phones, scanners, RFID tags, and the like. In various embodiments of the present invention, such receiving and/or transmitting functions may be radio-based and/or optically-based; however, the mode of receiving and/or transmitting is not a limitation of the present invention. In various embodiments, such receiving and/or transmitting functions may be used to provide information to and from the lighting system or the lighting control system; however, this is not a limitation of the present invention, and in other embodiments such receiving and/or transmitting functions may be used for other purposes, for example occupancy sensing, temperature sensing, advertising, tracking of people, equipment, or other items, inventory control, identification of items to be purchased, or any other purposes. 
     In various embodiments of the present invention, one or more additional connectors may be electrically coupled to power conductors  2391  and  2392  to provide access to power from power supply  2170 . In various embodiments, power conductor  2391  electrically couples connector  2030  to connector  2040 ′, and connector  2393  is a connector available for connection, and power conductor  2392  electrically couples connector  2040  to connector  2030 ′, and connector  2394  is a connector available for connection. In various embodiments, connectors  2393  and  2394  may be used to access power from power supply  2170  for, e.g., powering of other devices or components connected to the lighting system. Connectors  2393 ,  2394  may include or consist essentially of, for example, vertical connectors such as snap or pin connectors, or any other type of connector described herein. 
     In various embodiments, as shown in  FIG.  23 B , the lighting system may also provide access to other devices and/or sensors to control or communication signals or a network through one or more control connectors  2383  and access to power through one or more connectors  2393  and  2394 . 
     In various embodiments of the present invention, one or more tabs on light panel  110 , for example tab  1930 , may include a strain relief feature to provide some compliance or flexibility to the connections between light panels.  FIG.  24 A  shows an example of a tab  2410  that includes strain relief features  2430  and  2440  in accordance with various embodiments of the present invention. In various embodiments, each strain relief feature may include, consist essentially of, or consist of a perforation or cut (e.g., cut  2432 ) to permit independent or semi-independent movement of the portions of the sheet or substrate on either side of the strain relief feature. Such cuts may not penetrate through the entire width of the tab, and multiple cuts may terminate at different (e.g., opposite) sides of the tab. In various embodiments, the relative movement may include movement in a direction perpendicular or substantially perpendicular to the cut, within the plane of the cut, and/or out of the plane of the cut. In various embodiments, a strain relief feature may include a termination feature  2434  at one or both ends of the cut, for example to reduce the tendency of the cut to extend (e.g., extend its length) when the tab is deformed. For example, termination feature  2434  may include, consist essentially of, or consist of an aperture connected to the cut but having one or more dimensions (e.g., a width, length, or diameter) larger than that of the cut. In various embodiments, the termination feature  2434  may be at least partially curved (e.g., circular, elliptical, etc.) and may provide a larger radius of curvature than would be the case in which the cut simply terminated without termination feature  2434 . In various embodiments, cut  2432  may be straight or linear; however, this is not a limitation of the present invention, and in other embodiments cut  2432  may be curved or have any arbitrary path. In various embodiments, cut  2432  may have two ends (e.g., termination points), as shown in  FIG.  24 A ; however, this is not a limitation of the present invention, and in other embodiments a cut may have more than two ends and/or may define more than one linear or curved segment. While  FIG.  24 A  shows a tab  2410  having two strain relief features  2430  and  2440 ; this is not a limitation of the present invention, and in other embodiments tab  2410  may include only one strain relief feature or may include more than two strain relief features. As shown in  FIG.  24 A , tab  2410  includes two connectors  2450  (for; e.g., connection to another light panel); however, this is not a limitation of the present invention, and in other embodiments tab  2410  may include only one connector or more than two connectors. 
       FIG.  24 B  shows an example of a tab  2410  in accordance with embodiments of the present invention before connectors  2450  have been installed in holes  2452  in tab  2410 . In various embodiments, tab  2410  may include one layer of the material of the substrate  2460 ; as shown in  FIG.  24 B , while in other embodiments tab  2410  may include more than one layer of the material of the substrate  2460 , For example,  FIG.  24 C  shows an exemplary tab having two layers of the material of the substrate  2460 , the two layers being formed by folding one layer over and adjacent to another layer; for example folding tab portion  2411  over tab portion  2412  across fold line  2480 , In various embodiments, tab portion  2411  and tab portion  2412  may define holes therein of different shapes and/or sizes (e.g., different holes  2454  and  2456  respectively as shown in  FIG.  24 C ). In various embodiments of the present invention, portions of one or more conductive traces may be formed near or surrounding or partially surrounding holes  2452 ,  2454 , and/or  2456  to be electrically coupled to one or more connectors installed in such holes. 
     While a number of the examples described herein include or consist essentially of one or more flexible light sheets and one or more frame elements, this is not a limitation and in other embodiments frame elements may be eliminated, resulting in light panels including or consisting essentially of one or more flexible light sheets with no frame elements. 
     While a number of the examples described herein utilize a constant-voltage drive system for powering one or more light sheets or light panels, this is not a limitation of the present invention, and in other embodiments other modes of energizing one or more light sheets or light panels may be utilized, for example constant-current or AC drive or other modes. In some embodiments of the present invention, the mode of powering the light sheets or light panels may determine the type; number, or need for current control elements on each light sheet or light panel. For example, in some embodiments of the present invention, no current control elements may be required on the light panel or light sheet, for example if using a constant-current drive mode. 
     While a number of examples presented herein utilize 9V battery connectors for connectorized panels (i.e., panels having one or more connectors), this is not a limitation of the present invention and in other embodiments other types of connectors may be utilized. For example, such connectors may include commercially available plug and jack or male and female connectors, polarized or unpolarized connectors, or connectors which on one or more ends are connected to a light sheet or light panel by wires. 
     As utilized herein, the term “light-emitting element” (LEE) refers to any device that emits electromagnetic radiation within a wavelength regime of interest, for example, visible, infrared or ultraviolet regime, when activated, by applying a potential difference across the device or passing a current through the device. Examples of light-emitting elements include solid-state, organic, polymer, phosphor-coated or high-flux LEDs, laser diodes or other similar devices as would be readily understood. The emitted radiation of an LEE may be visible, such as red, blue or green, or invisible, such as infrared or ultraviolet. An LEE may produce radiation of a continuous or discontinuous spread of wavelengths. An LEE may feature a phosphorescent or fluorescent material, also known as a light-conversion material (or a wavelength-conversion material, or a phosphor), for converting a portion of its emissions from one set of wavelengths to another. In some embodiments, the light from an LEE includes or consists essentially of a combination of light directly emitted by the LEE and light emitted by an adjacent or surrounding light-conversion material. An LEE may include multiple LEEs, each emitting essentially the same or different wavelengths. In some embodiments, a LEE is an LED that may feature a reflector over all or a portion of its surface upon which electrical contacts are positioned. The reflector may also be formed over all or a portion of the contacts themselves. In some embodiments, the contacts are themselves reflective. Herein “reflective” is defined as having a reflectivity greater than 65% for a wavelength of light emitted by the LEE on which the contacts are disposed. In some embodiments, an LEE may include or consist essentially of an electronic device or circuit or a passive device or circuit. In some embodiments, an LEE includes or consists essentially of multiple devices, for example an LED and a Zener diode for static-electricity protection. In some embodiments, an LEE may include or consist essentially of a packaged LED, i.e., a bare LED die encased or partially encased in a package. In some embodiments, the packaged LED may also include a light-conversion material. In some embodiments, the light from the LEE may include or consist essentially of light emitted only by the light-conversion material, while in other embodiments the light from the LEE may include or consist essentially of a combination of light emitted from an LED and from the light-conversion material. In some embodiments, the light from the LEE may include or consist essentially of light emitted only by an LED. 
     One or more non-LEE devices such as Zener diodes, transient voltage suppressors (TVSs), varistors, etc., may be placed on each light sheet to protect the LEEs  230  from damage that may be caused by high-voltage events, such as electrostatic discharge (ESD) or lightning strikes. In one embodiment, conductive trace segments shown in  FIG.  2 B  between the LEE strings  250  may be used for placement of a single protection device per light sheet, where the device spans the positive and negative power traces, for example power conductors  210 ,  220 . These trace segments also serve to provide a uniform visual pattern of lines in the web direction, which may be more aesthetically pleasing than a light sheet with noticeable gaps between LEE strings  250 . In a more general sense, in addition to conductive traces  260  that are part of string  250 , additional conductive traces  260  that may or may not be electrically coupled to other strings  250  and/or power conductors  210 ,  220  may be formed on substrate  265 , for example to provide additional power conduction pathways or to achieve a decorative or aesthetically pleasing look to the pattern on the light sheet or to provide a communication pathway to one or more CEs  240 , for example to provide a control signal to the one or more CEs  240 . These trace segments also serve to provide a uniform visual pattern of lines in the web direction, which may be more aesthetically pleasing than a light sheet with noticeable gaps between LEE strings  250 . 
     In one embodiment, an LEE  230  includes or consists essentially of a bare semiconductor die (such as an LED), while in other embodiments LEE  230  includes or consists essentially of a packaged LEI). 
     In some embodiments, LEE  230  may include or consist essentially of a “white die” that includes an LED that is integrated with a light-conversion material (e.g., a phosphor) before being attached to the light sheet, as described in U.S. patent application Ser. No. 13/748,864, filed Jan. 24, 2013, or U.S. patent application Ser. No. 13/949,543, filed Jul. 24, 2013, the entire disclosure of each of which is incorporated by reference herein. 
     In some embodiments, LEEs  230  may emit light in a relatively small wavelength range, for example having a full width at half maximum in the range of about 20 nm to about 200 nm. In some embodiments, all LEEs  230  may emit light of the same or substantially the same wavelength, while in other embodiments different LEEs  230  may emit light of different wavelengths. In some embodiments LEEs  230  may emit white light, for example that is perceived as white light by the eye. In some embodiments, the white light may be visible light with a spectral power distribution the chromaticity of which is close to the blackbody locus in the CIE  1931  xy or similar color space. In some embodiments, white light has a color temperature in the range of about 2000 K to about 10,000 K. The emission wavelength, full width at half maximum (FWHM) of the emitted light or radiation or other optical characteristics of LEEs  230  may not be all the same and are not a limitation of the present invention. 
     In various embodiments, substrate  265  and/or the power bus substrate may include or consist essentially of a semicrystalline or amorphous material, e.g., polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, fiberglass, FR4, metal core printed circuit board, (MCPCB), and/or paper. Substrate  265  may include multiple layers, e.g., a deformable layer over a rigid layer, for example, a semicrystalline or amorphous material, e.g., PEN, PET, polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, and/or paper formed over a rigid substrate for example comprising, acrylic, aluminum, steel and the like. Depending upon the desired application for which embodiments of the invention are utilized, substrate  265  may be substantially optically transparent, translucent, or opaque. For example, substrate  265  may exhibit a transmittance or a reflectivity greater than 70% for optical wavelengths ranging between approximately 400 nm and approximately 700 nm. In some embodiments substrate  265  may exhibit a transmittance or a reflectivity of greater than 70% for one or more wavelengths emitted by LEE  230 . Substrate  265  may also be substantially insulating, and may have an electrical resistivity greater than approximately 100 ohm-cm, greater than approximately 1×10 6  ohm-cm, or even greater than approximately 1×10 10  ohm-cm. In some embodiments substrate  265  may have a thickness in the range of about 10 μm to about 500 μm. 
     In various embodiments, conductive elements, e.g., power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may be formed via conventional deposition, photolithography, and etching processes, plating processes, lamination, lamination and patterning, evaporation sputtering or the like or may be formed using a variety of different printing processes. For example, power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may be formed via screen printing, flexographic printing, ink-jet printing, and/or gravure printing. Power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may include or consist essentially of a conductive material (e.g., an ink or a metal, metal film or other conductive materials or the like), which may include one or more elements such as silver, gold, aluminum, chromium, copper, and/or carbon. Power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may have a thickness in the range of about 50 nm to about 1000 μm. In some embodiments, the thickness of power conductors  210 ,  220  and conductive traces  260  may be determined by the current to be carried thereby. While the thickness of one or more of power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may vary, the thickness is generally substantially uniform along the length of the trace to simplify processing. However, this is not a limitation of the present invention, and in other embodiments the thickness and/or material of power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may vary. In some embodiments, all or a portion of power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 , may be covered or encapsulated. In some embodiments, a layer of material, for example insulating material, may be formed over all or a portion of power conductors  210 ,  220  and conductive traces  260 , and/or power conductors  2120  and  2130 . Such a material may include, e.g., a sheet of material such as used for substrate  265 , a printed layer, for example using screen, ink jet, stencil or other printing means, a laminated layer, or the like. Such a printed layer may include, for example, an ink, a plastic and oxide, or the like. The covering material and/or the method by which it is applied is not a limitation of the present invention. 
     In various embodiments of the present invention, the substrate and conductive traces may have a thickness less than about 5 mm or less than about 2 mm or less than about 1 mm. 
     In various embodiments, the conductive traces  260  are formed with a gap between adjacent conductive traces  260 , and LEEs  130  and CEs  240  are electrically coupled to conductive traces  260  using conductive adhesive, e.g., an isotropically conductive adhesive and/or an ACA. ACAs may be utilized with or without stud bumps and embodiments of the present invention are not limited by the particular mode of operation of the ACA. For example, the ACA may utilize a magnetic field rather than pressure (e.g., the ZTACH ACA available from SunRay Scientific of Mt. Laurel, N.J., for which a magnetic field is applied during curing in order to align magnetic conductive particles to form electrically conductive “columns” in the desired conduction direction). Furthermore, various embodiments utilize one or more other electrically conductive adhesives, e.g., isotropically conductive adhesives, non-conductive adhesives, in addition to or instead of one or more ACAs. In other embodiments, LEEs  230  and CEs  240  may be attached to and/or electrically coupled to conductive traces  260  by other means, for example solder, reflow solder, wave solder, wire bonding, or the like. The method by which LEEs  230  and CEs  240  are attached to conductive traces  260  is not a limitation of the present invention. 
     CE  240  may be one component or multiple active and/or passive components. In one embodiment, power conductors  210 ,  220  provide a DC voltage or substantially DC voltage and CE  240  includes or consists essentially of a resistor, e.g. a current-limiting resistor. The choice of the resistance value may be a trade-off between a number of parameters and characteristics that may include, e.g., efficiency and current stability. In general, a larger resistance will result in reduced efficiency but greater current stability, while a smaller resistance will result in increased efficiency but reduced current stability. Variations in the current may result from variations in the input voltage (for example across power conductors  210 ,  220 ), variations in forward voltage of the LEEs  230  within the string, variations in the value of the current-limiting resistor, variations in current that may occur if one or more LEEs  230  in the string become short-circuited or the like. In the case of CE  240  including or consisting essentially of a resistor, in some embodiments CE  240  is a discrete resistor formed within or on conductive traces  260 , such as a chip resistor, a bare-die resistor or surface mount device (SMD) resistor. 
     As discussed above, in embodiments where CE  240  includes or consists essentially of a resistor, there may be trade-offs between efficiency and current stability. While such trade-offs may be acceptable in certain products, other products may require relatively better current stability at higher efficiencies, and in these cases CE  240  may include or consist essentially of multiple components or a circuit element, as discussed above. In some embodiments CE  240  includes or consists essentially of a field-effect transistor (FET) and a resistor. In another embodiment CE  240  includes or consists essentially of two bipolar junction transistors (BJTs) and two resistors. 
     In general, the efficiency and current stability increase with the number of components, as does the cost. In some embodiments where a CE  240  includes or consists essentially of multiple components, the components may be in discrete form (i.e., each component individually electrically coupled to conductive traces  260 ) or in hybrid form (where multiple separate components are mounted on a submount, which is then electrically coupled to conductive traces  260 ), or in monolithic form (where multiple components are integrated on a semiconductor chip, for example a silicon-based or other semiconductor-based integrated circuit), In some embodiments, CEs  240  may be in bare-die form, while in other embodiments CEs  240  may be packaged or potted or the like. In some embodiments, a CE  240  may include or consist essentially of a bare-die integrated circuit. In some embodiments, the integrated circuit includes or consists essentially of multiple active and/or passive devices that are fabricated on a common semiconductor substrate. 
     In other embodiments, power conductors  210 ,  220  may provide AC power, or power modulated at different frequencies and in these embodiments CEs  240  may be selected accordingly or may be omitted. In one embodiment, power conductors  210 ,  220  may provide a standard line voltage, for example about 120 VAC or about 240 VAC or about 277 VAC, for example at about 50 Hz or about 60 Hz. In some embodiments, CEs  240  may accommodate a plurality of input types, and thus be so-called “universal” CEs  240 , while in other embodiments different CEs  240  may be required for different input types. The actual component or components of CEs  240  are not limiting to this invention; however, in preferred embodiments of this invention, the positioning of CEs  240  does not disrupt the LEE pitch. In another embodiment of this invention, the positioning of CEs  240  is independent of LEE pitch. As discussed herein, CEs  240  and LEEs  230  may be electrically coupled to conductive traces  260  using a variety of means, for example solder, conductive adhesive or ACA; however, the method of electrical coupling of CEs  140  and LEEs  230  is not a limitation of the present invention. 
     The terms and expressions employed herein are used as terms and expressions of description and not of limitation, and there is no intention, in the use of such terms and expressions, of excluding any equivalents of the features shown and described or portions thereof. In addition, having described certain embodiments of the invention, it will be apparent to those of ordinary skill in the art that other embodiments incorporating the concepts disclosed herein may be used without departing from the spirit and scope of the invention. Accordingly, the described embodiments are to be considered in all respects as only illustrative and not restrictive.