Abstract:
A lighting system includes at least one lighting apparatus having a light emitting element capable of emitting a controllably variable light output in a region. A position determination subsystem is capable of determining a position in three dimensions of at least one mobile entity within the region. A control subsystem is capable of variably controlling a light output of the at least one lighting apparatus according to the position of the mobile entity. The system may determine position by radio ranging with mobile electronic elements. The system may include multiple lighting elements and may determine light levels according to positions of multiple mobile entities. The system may include a database of information about lighting elements, mobile entities, and lighting plans that may be selected from mobile electronic elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This divisional application claims priority date under U.S. application Ser. No. 12/932,608 dated Feb. 28 th , 2011. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     BACKGROUND 
     Lighting usually is an integral part of an office, factory, store, supermarket, hospital, home, other building, parking lot, walkway, roadway, park or other improved location. Light fixtures most commonly are located in close proximity above or on the sides of locations that people tend to occupy. A typical building incorporates a range of fixtures to address occupants&#39; needs. For example, a building may use 2 foot, 4 foot, or 8 foot fluorescent light fixtures with different wattages, light angles and mounting requirements. Open spaces may use fixtures of differing size and power. 
     Commercial buildings and other lighting typically involves the use of lighting fixtures that can only be turned on or off, such as by a mechanical switch, a motion detector, a light sensor switch or a timer. Some offices and outdoor security lighting use motion detectors with light sensors to trigger the switching of lights. If the timer is set too long, it wastes energy. If timer is set too short, it annoys its occupants. (The term “occupant” is not intended to be limited to interior building occupants but to occupants of any lighted space.) Furthermore, if an obstruction blocks a motion sensor, or if an occupant is beyond sensor range, the lighting scheme may not work at all. Occupants are often annoyed by the automatic switching off the lights when an occupant remains in a space beyond the timer period, such as by sitting still using a computer or reading a book. 
     SUMMARY 
     An objective of the invention is to provide improved lighting fixtures and systems. A further objective is to provide lighting systems with enhanced intelligence. Yet another objective is to provide lighting fixtures and systems that better adapt to occupant needs and environmental factors to provide enhanced productivity, security, asset tracking, occupant health monitoring, and other goals. Other objectives include: 
     (A) providing lighting that is more efficient than incandescent and fluorescent lights; 
     (B) providing lighting fixtures suitable for retrofit to existing buildings or installation in newly-constructed buildings; and 
     (C) providing lighting fixtures suitable for stand-alone operation or operation that coordinates multiple fixtures; 
     These and other objects may be achieved by providing lighting fixtures and systems designed with light emitting diodes (LEDs) that may be more efficient than fluorescent lights. Preferred fixtures may have modules that are 22 inches in length and optional numbers of LEDs in strips with variable output wattages and color temperatures. The modules can be chained together to achieve longer lengths. LED light strips preferably have several segments which may be individually driven or commonly driven. In the event that LEDs in some but less than all segments should fail, the LEDs in the other segments would remain functional. This overcomes a draw back in incandescent and fluorescent light fixtures that may go totally dark upon failure of an individual bulb. Fixtures may provide different color lights for each individual LED segment. The use of Red, Blue and Green LEDs for each segment allows the fixture to provide a selectable color chromaticity. An output level and/or chromaticity will be referred to here as a light plan. Fixtures may include capability for performing some or all of the following functions: 
     a) Self reporting of power usage and power consumption histories and patterns. 
     b) Automatic control of light fixture usage due to:
         i) environment (e.g., ambient light, time of day, etc.),   ii) motion detectors sensing the presence and/or activity of people,   iii) behavior or pattern of occupants, and/or   iv) proximity of users and events;       

     and/or 
     c) Security and/or backup lighting for security and/or safety. 
     Lighting usage may be adjusted according to social behavior patterns. Social behavior may be captured by associating a wearable or otherwise portable device carried by occupants, such as a badge embedded with RFID devices, a cell phone, or other another electronic device that has a traceable unique identifier. Lighting fixtures may be assigned with a unique identifier and may communicate with portable devices to form a dynamic wireless network, such as a Zigbee network. A database may be provided to maintain information about portable devices, fixtures, and other information. 
     The early sections of the description below discuss lighting fixtures and their mechanical parts and assembly. Among other things, they describe a modular feature and a reflector that can adjust its angle to tailor light distribution to room requirements. The LEDs can cascade to various lengths according to room requirements while still powered by the same power source and drivers. 
     Then, circuit designs of LED drivers for lighting fixtures are shown with electrical details of how fixtures may be powered by one or more drivers under cascading conditions. The intensity of LED chains may be varied by a dimming capability of drivers and controllers. Alternative circuit configurations of drivers, jumpers and temperature controls are shown which facilitate LED function and longevity. LEDs can have 50,000 to 60,000 hours of lifetime compared to 8,000 to 10,000 hours for fluorescent lights. 
     Final sections discuss the use of microcontroller systems in the fixtures, portable devices worn by the users and network servers controlling, recording and coordinating lighting functions. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       Reference will be made to the following drawings, which illustrate preferred embodiments of the invention as contemplated by the inventor(s). 
         FIG. 1 . Light fixture parts assembly. 
         FIG. 2 . Type B ceiling support bracket. 
         FIG. 3 . Type C corner support bracket. 
         FIG. 4 . Type A flat surface support bracket. 
         FIG. 5 . Fixture back cover. 
         FIG. 6 . Detail features of a fixture back cover. 
         FIG. 7 . Light diffuser unit. 
         FIG. 8 . Light reflector unit. 
         FIG. 9 . Rotate block A. 
         FIG. 10 . Rotate block B. 
         FIG. 11 . LED light/reflector rotation system. 
         FIG. 12 . Type A end cover. 
         FIG. 13 . Type A end cover details. 
         FIG. 14 . Type B end cover. 
         FIG. 15 . Type B end cover details. 
         FIG. 16 . Cable rotate block side view 
         FIG. 17 . Cable rotate block front view. 
         FIG. 18 . Cable conduit. 
         FIG. 19 . LEDs light strip. 
         FIG. 20 . LEDs light strip circuit assembly. 
         FIG. 21 . LEDs strip circuit diagram with PTC components. 
         FIG. 22 . LEDs strip circuit diagram with shorting end jumpers. 
         FIG. 23 . Cascading of two fixture modules with end jumpers. 
         FIG. 24 . Triple LEDs chain driver circuit. 
         FIG. 25 . Single LED driver configuration. 
         FIG. 26 . Cascading of two LED fixtures with short end and driver front jumpers. 
         FIG. 27 . PTC regulatory circuit design. 
         FIG. 28 . End circuit jumpers for a 3 LED circuits. 
         FIG. 29 . The PTC regulation design in a three LED driver circuits. 
         FIG. 30 . PTC regulation design in a one LED driver circuit. 
         FIG. 31 . NTC regulatory circuit design. 
         FIG. 32 . NTC regulation design in a three LED driver circuits 
         FIG. 33 . NTC regulation design in one LED driver circuit. 
         FIG. 34 . Type A connector. 
         FIG. 35 . Type B connector. 
         FIG. 36 . Bracket Latch. 
         FIG. 37 . Illustration of an Intelligent Lighting network. 
         FIG. 38 . Wireless Network Map. 
         FIG. 39 . Brightness control feedback loop 
         FIG. 40 . Light Sensor Microcontroller control via an I2C communication. 
         FIG. 41 . A controller system with intelligence. 
         FIG. 42 . Light Illumination Plan A—Ultra Savings. 
         FIG. 43 . Light Illumination B—Moderate Savings. 
         FIG. 44 . Light Illumination C—Nominal Savings. 
         FIG. 45 . Light Illumination C—Nominal Savings with Walking. 
         FIG. 46 . MCU controlling a wireless RF Chip CC2500. 
         FIG. 47 . CC2500 Pin Configuration and Pin function 
         FIG. 48 . MSP430 Communication Pins. 
         FIG. 49 . CC2500 components values. 
         FIG. 50 . Flowchart for a Mobile Tag. 
         FIG. 51 . Distance measurements from RSSI. 
         FIG. 52 . Example Front view of mobile tag (End Device) 
         FIG. 53  Access point Flow Chart. 
         FIG. 54 . Master Network Server. 
         FIG. 55 . Master Network Server flow chart Part  1 . 
         FIG. 56 . Master Network Server flow chart Part  2 . 
         FIG. 57 . Master Network Server flow chart Part  3 . 
         FIG. 58 . Additional AC voltage and current sense IC interface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A need exists for intelligence in responding to lighting needs of the users or occupants of a building, walkway, or other indoor or outdoor places that people may occupy. Activities determine how bright a location may need to be. People occupying spaces where the light fixtures are installed often have unspoken social interactions and intentions. A light fixture output should respond to the needs and requirements of the occupants, their activities, and the environment. Environmental factors also influence lighting needs, such as interior or exterior location, proximity to windows (if interior), other light sources and time of day. Consider, for example, a person walking across a very large space, such as a conference room, long hallway, parking lot, or sidewalk. The person would expect good lighting conditions in the direction of travel. However, to light up an entire area equally with constant brightness would be energy inefficient. Therefore an automatic adaptation of the lighting conditions in the direction of travel would conserve energy. A janitor, who cleans the offices especially during the night would need the light levels to be high to perform a good job. A person working on a computer and looking at a screen would like to have the room light level to be less then for reading a book. The room lights should not cause glare or compete with the computer monitor brightness. Adjusting lights with the right level would not only save the lighting energy, it would save the computer monitor&#39;s energy too. It is useful to track positions occupants relative to lights sources. 
     Light fixtures preferably will be installed in fixed locations in every room throughout a building or at regular intervals in exterior spaces. Their locations preferably will be non-obstructive and strategically positioned where the occupants would use the light for carrying out their activities. Most likely these fixtures would be installed above people&#39;s heads and therefore provide a good planar arrangement defining the ground or floor level. Staircase lightings would appear as between levels. 
       FIG. 1  shows selected components of one embodiment of a preferred LED lighting fixture, referred to here as a “type B” fixture to distinguish it from other fixture types discussed further below. Such a fixture may include: a light diffuser  2 , a back cover  4 , a type B connector  6 , a type B end cover  8 , a rotate block A  10 , one or more type A support brackets  12 , one or more reflectors  14 , a cable conduit  16 , a cable rotate block  18 , one or more LED light strips  20 , a type A end cover  22 , a type A connector  24 , and a rotate block B  26 . 
       FIG. 2  shows a type B support bracket for alternate mounting of the fixture and adaptation to a choice of mounting methods. This may replace the type A bracket  12  shown in  FIG. 1 . This bracket supports the fixture from above through a hole  50  in chain bracket. Such a hole  50  allows the bracket to connect via either chain or other vertical architectural structure. It has a set of angle flaps  56  which connect to a back cover  4  ( FIG. 1 , item  4 ) of a fixture with a hooked edge at the ends that secures the fixture. The bracket first may be secured to a building support, and then the fixture may be snapped in place. 
     When two fixtures are joined together end-to-end, a bracket may be placed across the joining ends of the fixtures. A set of cut-out slots  54  preferably grips two fixture end covers and locks them in place. 
     Type C Corner Support Bracket 
       FIG. 3  shows a type C support bracket, which may be used for corner fixture mounting. This may replace the type A bracket  12  shown in  FIG. 1 . Two flaps  62  are similar to type B bracket flaps  56  except for holes  60 . These holes  60  may be used for screw mounting to a corner lighting location. Slots  64  may be used similarly to the two cut-out slots  54  in  FIG. 2  to join adjacent fixtures. 
     An outer surface of the bracket flaps  62  can also serve as a surface for a double sided tape or Velcro piece to secure the bracket to any surfaces. This would make mounting flexible for many surfaces. 
     Type A Flat Surface Support Bracket 
       FIG. 4  shows a type A support bracket, which may be used for mounting to a ceiling or other surface. This type of support bracket is also shown in  FIG. 1 . A hole  72  can be used to screw the fixture to any flat surface. A bracket surface  70  alternately may serve as a surface for a double-sided tape or Velcro piece to secure the bracket to many surfaces. This would make mounting flexible for many surfaces. 
     Flaps  76  may be similar to flaps  56  of the type B bracket shown in  FIG. 2 , except that that they may flare outwardly  74 , to accommodate the surface  70 . The lengths of the flaps  74 ,  76  may be varied to provide a desired height to the fixture. This bracket allows the fixture to be mounted within another fixture, such as within an existing fluorescent tube fixture where the tube may be absent. 
     Fixture Back Cover 
       FIG. 5  shows a preferred back cover ( FIG. 1 , item  4 ) as an angled piece  80  with two, generally-flat surfaces and a protruded lip on the long edges  84 . There may be two holes  82  on each short edge to secure triangular end cover pieces ( FIG. 1 , items  8 ,  22 ) with screws. Details of lips  84  are shown in  FIG. 6 . These lips may be used to secure a light diffuser  2  to a back cover  4 . A track allows a flat diffuser  2  to slide in from the ends. 
     Light Diffuser 
       FIG. 7  shows an exemplary light diffuser ( FIG. 1 , item  2 ) having a flat form. A diffuser may be made of transparent material  90  which has patterns to diffuse any spot appearance of LED lights. It preferably would be a light weight plastic, glass, or other material. The diffuser preferably lets light through efficiently but in a diffused manner. Diffusers such as those used in fluorescent light fixtures may be patterned plastic material, though they might not be the most efficient. A preferred, more efficient light diffuser would be a Fresnel diffuser. These diffusers may have transmission efficiencies greater than ninety-eight percent. The entire diffuser piece can be made of this Fresnel type. An example is a clear acrylic material with a DIFF_RDN_20_R/20 FWHM random diffuser finish on one side from Fresnel Technologies, Inc. Wide diffusion angles of twenty degrees or more are preferred if the spotty look is to be minimized. Alternately, a diffuser can have localized Fresnel pattern areas, such as circular patches  92  where the Fresnel random diffuser is aligned in front of each LED spot on a light strip  20 . Other areas beyond these patches can be either transparent or translucent. These diffusers may be fabricated from laser holography plastic cutting techniques on sheet plastic materials. 
     Light Reflector Unit 
       FIG. 8  shows an exemplary, curved light reflector ( FIG. 1 , item  14 ) with a body  100  and two guide rails  104 . Such a reflector has holes  102  to permit access to LED light sources. Guide rails  104  have fingers to secure an LED light strip  20 . Sandwiched between the LED light strip and the reflector may be a piece of thermally conductive elastomer with holes matching holes of the reflector. This elastomer piece may be electrically insulated or insulative. The reflector front preferably has a highly reflective surface  106  which may be an electroplated or plastic plated surface with a protective coating. A reflective adhesive foil would be one of many an alternate solutions. The reflector may be made of thermally conductive material. Preferably, it could be metallic or plastic material loaded with thermally conductive particles, such as barium titanate or strontium titanate. 
     Rotate Block A 
       FIG. 9  shows a first, A-type, rotate block ( FIG. 1, 10 ). It may be comprised of an LED light strip mounting body section  110 , a round disk section  114 , a rod rotation section  118 , and a rotate coupling connector  116 . Two screw holes  112  in the body section  110  may be used for mounting an LED light strip ( FIG. 1 , item  20 ). Screw holes  112  may be used to rigidly secure the rotate block to an aluminum plate  206  illustrated in  FIG. 20 . This block enables an LED light strip to rotate, either manually by a screw driver at the end or by an electrically controlled by a coupling stage. 
     Rotate Block B 
       FIG. 10  shows a B-type, rotate block ( FIG. 1  item  26 ). It may be similar to an A-type rotate block, except for the absence of a rotate coupling connector  116 . 
       FIG. 11  shows a detailed view of elements used in adjusting an angle of a light fixture. An end cover  160  has a hole  166  for receiving a rod  138  from rotate block B  164 . A spring  162  may be placed over the rod  138  to press against a disc of rotate block B ( FIG. 10 , item  136 ). An LED light/reflector assembly  168  may attach to rotate block B by screws through holes in rotate blocks A and B ( FIG. 9 , item  112  and/or  FIG. 10 , item  134 ). The spring tension at the disc  136  also pushes against a disc of block A ( FIG. 9 , item  114 ). The disc  114  also presses against a geared/rough surface ring  172  in end cover  174 . The disc  114  is in engaged mode and holds an angle for the reflector assembly. By fitting a screw driver through hole  176  into a slot  178  and pushing against the spring compression, the disc disengages from the fixed ring  172 . Turning the screw driver then freely rotates the reflector assembly  168 . A user may see the light corresponding to the adjusted angle in real-time. Once a desired angle is achieved, the user can withdraw the screw driver, and the disc  114  will once again press against ring  172  and hold the fixture engaged in the set angle. The spring maintains a pressure to hold the disc engaged with the ring  172 . 
     Type A End Cover 
       FIG. 12  shows an exemplary, Type A, end cover ( FIG. 1 , item  22 ). This cover may be a triangular-shaped end body piece  120  with three openings. This cover may be secured within the inside back cover of a light fixture ( FIG. 1 , item  4 ) via screw holes  126  on two sides of the cover. The back cover ( FIG. 1 , item  4 ) preferably retains a smooth surface. A circular opening  122  allows the rotate coupling connector ( FIG. 9 , item  116 ) of Rotate Block A ( FIG. 1 , item  10 ) to fit through. A rectangular opening  128  may allow access for an electrical connector (e.g.,  FIG. 1 , items  6 ,  24 ) to the next fixture module. A rectangle opening  124  may be included as a venting hole. 
       FIG. 13  shows an alternate view of Type A end cover  22 . The rotate block A  10  preferably fits through a circular hole  122  and stays within the front surface of the cover  22  having a lip  130  around its edge. 
     Type B End Cover 
       FIG. 14  shows an alternate, type B, end cover ( FIG. 1 , item  8 ). This cover has a concealed circular ring  194 , which may be a support for a rod rotation section ( FIG. 10 , item  138 ) in rotate block B and holds in place a curved reflector ( FIG. 1 , item  14 ) in a user-adjusted angle of rotation. A circular opening  196  allows cable rotate block ( FIG. 1 , item  18 ) to fit through from an outer surface. Similar to the Type A end cover, there may be screw holes  192  on two sides of the cover. A smaller rectangular opening  190  may be provided as a vent hole. 
       FIG. 15  shows an alternate view of Type B end cover ( FIG. 1 , item  8 ). A circular ring  194  in  FIG. 14  may be concealed from this outer view of the cover. If a hole through the circular ring  194  is opened, a rotation rod adapted to be turned with a screw driver may slide to a corresponding hole in the next module and engage with the rotation rod in the adjacent module to rotate the other module&#39;s reflector assembly. 
     Cable Rotate Block 
       FIG. 16  shows an exemplary cable rotate block ( FIG. 1 , item  18 ). This block has a body  180  with a power cable entrance path  182  that enters the fixture through a passage  184 . A rotate shaft  186  and a split coupler  188  preferably fit through a hole in a triangular end cover (e.g., FIG.  12 , item  122 ). 
       FIG. 17  shows an alternate view of the cable rotate block of  FIG. 16 . A cable enters from a cable conduit ( FIG. 1, 16 ), goes into a cavity  182 , makes a right turn into hole  184 , and feeds into the fixture. A split coupler  188  prevents the rotate block from slipping out of an end-cover hole (e.g.,  FIG. 15 , item  194 ). The block can rotate freely with respect to an end cover. 
     Cable Conduit 
       FIG. 18  shows a cable conduit ( FIG. 1 , item  16 ). It may be made of a hollow rod  140 , and it can be made of any appropriate length. In this manner, the cable may be shielded by the conduit. This conduit can be made of plastic or metal. 
     LED Light Strip 
       FIG. 19  shows an exemplary LED light strip ( FIG. 1 , item  20 ). Circular dots  152  represent LEDs mounted preferably on a flexible circuit  154 , which in turn may be mounted on aluminum bar  156 . The screw holes  150  on both ends of the bar allows rotate block A ( FIG. 1 , item  10 ) and rotate block B ( FIG. 1 , item  26 ) be mounted. 
       FIG. 20  shows an exemplary assembly of an LED light strip with reflector and heat sink. LEDs  200  may be soldered or otherwise attached onto a copper flex circuit  202 . The flex circuit substrate may be about 25 to 75 microns thick, which would allow heat to transfer easily in the Z direction orthogonal to the flexible circuit surface. The substrate material may be an insulator made preferably of one of the following materials, though other materials may be used: 
     a) Kapton™ (Polyimide film) 
     b) PEN (Polyethylene Naphthlate film such as Teonex, Teijin, Dupont) 
     c) PET (Polyethylene Terephthalate film from Dupont) 
     The flex circuit conductive traces may be two ounce copper, about 2.8 mils thick, for both low resistance and good thermal conductivity. Control signal traces may be low current circuits. Additive printed thick film technology (PTF), such as silver ink, can be used. Conductive traces may be routed with design rule to retain most of the conductive copper. An LED heat sink may be mounted on the copper pads with solder or heat sink compound to promote heat dissipation. The flexible circuit  202  may be attached to the aluminum block or plate  206  via a high temperature, double sided adhesive tape  204 . An aluminum heat sink plate may be formed into a one-dimensional parabolic shape and electroplated with a highly reflective coating to be used as the LED light reflector simultaneously. An example of an adhesive tape is the 3M #467MP tape. This tape has a thickness of approximately 50 microns and allows both surfaces come into good contact for good thermal transfer. A high temperature, thermally conductive, electrically insulative, silicone gasket  208  with holes for LED components to pass through may be used between the reflector  14  and the LED Flexible circuit  202 . 
       FIG. 21  shows an exemplary circuit diagram for a six-LEDs strip formed in three chains A, B, C. Paths A, B, C, D, E and F may be considered high current LED power circuits. D, E, and F may be used for LED current return. Two LEDs  210 ,  212  may be on Chain A, two LEDs  214 ,  216  may be on Chain B, and two LEDs  218 ,  220  may be on Chain C. This method may be applicable for other numbers of LEDs in each chain. Each chain preferably has an equal number of LEDs. Three paths D, E, F may be pass-through circuits without components. 
     Additional paths G, H, I, J, K, L, M, N and O may be part of the LED power regulation circuits. They may be low current circuits. One Positive Temperature Coefficient thermal conductive trace (PTC) may be in each of three circuits G, H and I. One PTC  222  may be in a first circuit G, one PTC  224  may be in a second circuit H, and one PTC  226  may be in a third circuit I. Each thermal conductive trace may be physically located in the proximity of one of the LEDs in each chain, such as the first LEDs  210 ,  214 ,  218  in each chain. Since the second LED in the same chain may be driven by the same current, it may be assumed to have a similar thermal dissipation characteristics and therefore similar temperature response. In this manner, a single PTC may be used for each circuit, which lowers the component count when compared to monitoring every LED. 
     There may be one resistance trace  228 ,  230  and  232  in each of the circuits, J, K and L respectively. These PTC thermal conductive traces and resistance traces may be used to control a current through the LED chains, A, B and C via a circuit shown in  FIG. 23 . This prevents the overheating of the LEDs and prolongs its working life. This LED temperature regulation method is discussed in further detail in following sections. 
     Three circuits M, N and O may be without components and may be used to bring electrical connections between pins of the right connector  236  and pins of the left connector  234 . 
       FIG. 22  shows an exemplary powering scheme for a six-LED fixture with a fifteen pin input connector  234  and a fifteen pin output connector  236 . The output connector shown has jumpers  250 ,  252 ,  254  for connecting each of three LED chains A, B, C to each of three return paths D, E, F respectively. Three other jumpers  256 ,  258  and  260  each connects two PTC circuits G, H, I, J, K, L to one return path (G and J to M; H and K to N; and I and L to O respectively). 
     Input pins P 1 , P 2 , P 3  each preferably supplies current to one of the LED chains A, B and C respectively and hence through jumpers  250 ,  252 ,  254  to three other pins P 4 , P 5 , P 6 . The input connector and the output connector are preferably of opposite gender. This choice allows the input connector of a second fixture be connected to a first fixture output connector without an intermediate piece. 
       FIG. 23  shows an example of such a two-fixture connection scheme. Jumpers  250 ,  252 ,  254 ,  256 ,  258  and  260  may be used at the output connector  236  for the second fixture. In this example, there would be twelve LEDs, six thermistors and six resistors in total. The power supply connection at the first input connector  234  would remain the same as for the circuit of  FIG. 22 . This connection scheme can be extended to cascade multiple fixtures in series. Six jumpers  250 ,  252 ,  254 ,  256 ,  258  and  260  may be used at the output connector  236  for the last fixture. 
     This circuit design and connection scheme allows fixtures to be modular. A long fixture can be composed of multiple shorter fixtures connected to the right hand side and terminated with a consistent jumper design. 
     Multi-Chain LED PLM Driver 
       FIG. 24  shows an exemplary LED driver circuit for a fixture for powering three chains A, B and C separately, each by a driver chip, U 1 A, U 1 B and U 1 C. An exemplary chip driver is a National Semiconductor integrated circuit LM3414HV or LM3414 with Pulse Level Modulation (PLM). Each driver circuit may have three resistors R 1 , R 2 , R 3 , one schottky diode D 1 , one inductor L 1 , one capacitor C 2 , one transistor Q 1 , and one printed thermally responsive resistance trace T 1 . One resistance R 1  preferably is a printed resistance trace. The suffixes A, B and C to each of these components signify an association to a corresponding one of the three driver chips U 1 A, U 1 B, and U 1 C. The maximum input voltage (Vin) for an LM3414HV may be 65V, and for an LM3414 it may be 42V. Thermally responsive traces T 1  and printed resistance traces R 1  may be discrete components instead of printed traces. 
     A printed thermal responsive resistance trace T 1  and a printed resistance trace R 1  also are shown as items  222 ,  224 ,  226  and items  228 ,  230 ,  232  respectively in  FIGS. 21 and 22 . The example shown in  FIG. 23  may have only two fixtures, in which case a single thermal responsive trace T 1 A and resistance R 1 A ( FIG. 24 ) may be a series of components shared across two fixtures. Such a thermal responsive trace T 1 B and resistance trace R 1 B also are shown as items  224  and  230  in  FIGS. 21 and 22 . A thermal responsive trace T 1 C and resistance trace R 1 C also are shown as items  226  and  232  in  FIGS. 21 and 22 . Where multiple fixtures may be used, multiple sets of these components may be repeated in each of the fixtures as shown in  FIG. 23 . 
     In  FIG. 24 , five circuit elements R 1 , R 2 , R 3 , T 1  and Q 1  (on the left hand side of integrated circuits U 1 A, U 1 B U 1 C) form a current control to an LED chain (on the right hand side of integrated circuits U 1 A, U 1 B, U 1 C). Resistances R 1  and thermal responsive traces T 1  form voltage dividers across a constant reference voltage Vcc. When a PTC thermal responsive trace T 1  increases in its resistance value due to rise in temperature, a voltage increases across a base-emitter of transistors Q 1 A, Q 1 B, Q 1 C. This results in increasing the emitter current flowing into I ADJ  input pin of U 1  and thereby decreases the LED current. A reduction of the LED current will reduce the dissipation of heat. The choice of values for thermal responsive traces and resistances T 1 , R 1 , R 2  and R 3  determines an operating temperature of the LED strip light. Capacitors C 2 A, C 2 B C 2 C may be bypass capacitors to ground and chosen for at least 1 uF capable of withstanding 6V or more. 
     LEDs  210  and  212  in  FIGS. 21, 22 and 23  are shown as LED 1 A and LED 1 B in  FIG. 24  respectively. LEDs  214  and  216  in  FIGS. 21, 22 and 23  are shown as LED 2 A and LED 2 B in  FIG. 24  respectively. LEDs  218 , and  220  in  FIGS. 21, 22 and 23  are shown as LED 3 A and LED 3 B in  FIG. 24  respectively. 
     A driver circuit regulates a current supplied to the LED chain and draws its power from a constant voltage source shown as +Vin and ground. A resistor R 4  sets a PWM frequency. An inductor L 1  reduces ripple across the LED chain. When three LED chains A, B and C are powered separately, an LED failure in one would not cause a failure in the other two chains. 
     In the absence of resistances R 1 , R 2 , RT 1  and transistors Q 1 , LED current may be determined by equation (1)
 
 I   LED =3.125×10 3   /R   3  mA  (1)
 
     Where, preferably, 0.35&lt;=I LED max&lt;1.0 amps, and 3125 ohms&gt;R 3 &gt;=8929 ohms 
     Incorporating elements R 1 , R 2 , RT 1  and Q 1 , the LED current I LED  may be modified to equation (2)
 
 I   LED =[((3.125×10 3   /R   3 )− I   EXT )×249×10 3 ] mA  (2)
 
     I EXT  may be a current of about 400 uA through resistor R 2 , and R 2  may be chosen to satisfy equation (3) after choosing R 3  from equation (1).
 
 I   EXT =( Vb−Vbe− 1.255)/ R   2 &lt;1.255/ R   3 =(˜400 uA)  (3)
 
since Vbe˜0.7V for a silicon bipolar transistor, and the I ADJ  pin of the integrated circuits U 1  may be internally biased at 1.255V.
 
     The emitter current I E , of transistors Q 1 , may be the same as I EXT . Transistor Q 1  base current I B  may be approximately: I EXT /β, where β is the current gain for transistor Q 1 . The base voltage Vb of transistor Q 1  may be given by equation (4).
 
 Vb =[( R   T1   ×R 1)/( R   T1   +R 1)]×[( Vcc/R 1)−( I   EXT /β)]volts  (4)
 
     Since preferably Vcc=5.4V, and for a typical small signal bipolar transistor with V CEO &gt;Vcc and current gain β greater than 100, the equation for the base voltage may be simplified to
 
 Vb =( R   T1   ×Vcc )/( R   T1   +R 1)  (5)
 
     Resistances R T1  and R 1  may be chosen to satisfy conditions (6)
 
 Vb &gt;( Vbe+ 1.255) volts and ( Vcc/[R   T1   +R 1])&gt;&gt;1.255/(β× R   3 ) uA  (6)
 
 Vb &gt;(0.7+1.255) volts and (5.4/[ R   T1   +R 1])&gt;&gt;4 uA
 
 Vb =(5.4× R 1)/[ R   T1   +R 1]&gt;1.955 volts and [ R   T1   +R 1]&lt;&lt;1.35×10 6  ohms
 
 R 1/[ R   T1   +R 1]&gt;0.362 and [ R   T1   +R 1]&lt;&lt;1.35×10 6  ohms  (7)
 
A load on Vcc preferably should be less than 2 mA, and 5.4/[ R   T1   +R 1]&lt;2×10 −3 .
 
     Therefore [R T1 +R 1 ] may be described by equation (8)
 
1.35×10 6   &gt;&gt;[R   T1   +R 1]&gt;2.7×10 3  ohms  (8)
 
Cascading Fixtures Deeping Voltage Divider Point, Vb Consistent.
 
       FIG. 23  illustrated two fixtures connected in series. For examples such as this, values of R 1  and R T1  used in equations (7) and (8) would be the series values of resistances R 1  and R T1  from fixture  1  and  2  respectively for each of the suffixes. For example:
 
 R   1 ( A )= R   1A (Fixture 1)+ R   1A (Fixture 2) for the “ A ” suffix and  R   T1 ( A )= R   T1A (Fixture1)+R T1A (Fixture 2)
 
 R   1 ( B )= R   1B (Fixture1)+ R   1B (Fixture2) for the “ B ” suffix and  R   T1 ( B )= R   T1B (Fixture1)+ R   T1B (Fixture2)
 
 R   1 ( C )= R   1C (Fixture 1)+ R   1C (Fixture 2) for the “ C ” suffix and  R   T1 ( C )= R   T1C (Fixture1)+ R   T1C (Fixture 2)
 
     A design as shown in  FIG. 23  allows multiple fixtures to be cascaded without changing the voltage divider point Vb. Resistance values R 1  and R T1  may stay consistent for each fixture. Therefore equations (1) through (8) define a range of values for components R 1 , R 2 , R 3 , RT 1 , Q 1  with suffixes A, B and C in  FIG. 24 . 
     The resistor R 4  preferably determines a switching frequency fsw, 250 KHz&lt;fsw&lt;=1 MHz
 
20&gt; R 4=20×10 6   /fsw&gt; 80 k ohms  (9)
 
     The driver circuit preferably operates in Continuous Conduction Mode operation (CCM) with LED ON time less than 400 ns. The minimum LED switched ON time preferably would satisfy
 
 VLED&gt;= 400 ns× fsw×V in  (10)
 
     Resistance R 4  may be selected to satisfy this condition. 
     An inductor L 1  may be part of the Pulse Level Modulation circuit. A minimum inductance L 1  may be used to maintain less than 600/o of the defined average output ripple current. Inductor L 1  preferably satisfies equation (11) 
     
       
         
           
             
               
                 
                   
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     Where I LED =I L average=Mid point of I L 1  during t ON    
     Schottky diode D 1  preferably would withstand the peak LED current and 1.6Vin. 
     Single LED Driver Configuration 
     A fixture circuit as shown in  FIG. 21  can also be powered by using only one integrated circuit driver U 1 . Such a design is shown in  FIG. 25 , which is similar to that of  FIG. 24 . The component count is reduced by ⅔. Component suffices “A”, “B” and “C” are omitted other than for the LED chain. 
     Such an LED chain may be connected in series to drive all six LEDs all at the same time by a single integrated circuit driver U 1 . Components R 1 , R 2 , R 3 , R 4 , Q 1 , C 2 , D 1 , L 1  still may be selected using equations (1) through (11) except that the equivalent resistance value of thermally responsive traces T 1  shown in  FIG. 25  may be the series of thermally responsive traces  228 ,  230  and  232  of fixture  1  and  228 ,  230  and  232  of fixture  2 . The equivalent resistance of resistance R 1  may be the series resistances of  222 ,  224  and  226  of fixture  1  and  222 ,  224  and  226  of fixture  2 . For a preferred embodiment as in  FIG. 25 :
 
 R 1(equivalent)=[ R (222)+ R (224)+ R (226)] fixture 1   +[R (222)+ R (224)+ R (226)] fixture 2   (12)
 
 RT 1(equivalent)=[ R (228)+ R (230)+ R (232)] fixture 1   +[R (228)+ R (230)+ R (232)] fixture 2   (13)
 
Such a cascade series of fixtures each having six LEDs is shown in  FIG. 26 . This arrangement may be achieved by having the same jumpers  250 ,  252  and  254  at the last output connector  236  as in  FIG. 23 . In addition, there may be additional jumpers  270  and  272  at the first input connector  234 .
 
     The thermally responsive traces may be connected in series across the fixtures. The jumpers at the last output connector would be items  262 ,  264 ,  266 ,  268 . The jumpers at the first input connector  234  would be items  274 ,  276  and  278 . 
     Input Connector Pin Reduction Circuit 
       FIG. 27  shows a circuit diagram with six LEDs formed in three chains A, B and C but with a lower pin count to both input connector  280  and output connector  282  when compared to the circuit of  FIG. 21 . The connector pin counts may be reduced from fifteen to ten. The circuits that form the LED paths would be A, B, C, D, E and F. Circuits D, E, and F would be used for the LED current return path. 
     PTC Regulatory Circuit Design 
     In  FIG. 27 , paths H and J may be low current return signal paths. Positive Temperature Coefficient (PTC) thermal traces  290 ,  292 ,  294  may be connected in series in trace G. Each PTC trace may be located in proximity to one LED in each chain. Since the second LED in the same chain may be driven by the same current, it may be assumed to have the similar thermal dissipation characteristics and therefore similar temperature response. An arrangement such as this lowers component count compared to monitoring every LED. Three printed resistance traces  300 ,  302 ,  304  may be connected in series in signal path  1 . Both PTC traces and resistance traces may be used to control a current through the LED chains A, B, C via a circuit as shown in  FIG. 25 . Such current regulation prevents the LEDs from overheating and prolongs their working lives. 
       FIG. 28  shows circuit jumpers  250 ,  252 ,  254  for connector  282  for three LED circuits which may be similar to jumpers for connector  236  in  FIGS. 22 and 23 . However, other circuit jumpers  310 ,  312  for connector  282  would be different from jumpers  256 ,  258 ,  260 , for connector  236  in  FIGS. 22 and 23 . 
       FIG. 29  shows an alternate LED driver circuit embodiment using three drivers. Each of three PTC traces may be located near a first LED for each respective chain. For example, a first PTC trace  290  may be located near LED  210  for Chain A; PTC trace  292  may be located near LED  214  for Chain B; and PTC trace  294  may be located near LED  218  for Chain C respectively. In this manner, the corresponding PTC trace may be used to control the temperature in each chain by controlling the current flow through the chain. 
     Three transistors Q 1 A, Q 1 B and Q 1 C may use a common reference voltage Vcc. If each driver chip U 1 A, U 1 B, U 1 C generates a separate reference, the three reference voltages may be “diode-OR&#39;d” to form the single reference voltage Vcc for the three transistors. In this way, if any of the three driver chips U 1 A, U 1 B or U 1 C should fail, another of the driver chips will maintain the reference voltage Vcc. 
       FIG. 30  shows an alternate design which uses only one integrated circuit U 1  to drive all LEDs using pin connections P 1  through P 10  (connectors shown in  FIG. 28 ). The number of LEDs driven by this circuit may be governed by the maximum output voltage of driver, which may be 65V for LM3414HV and 42V for LM3414. The circuit scheme in  FIG. 29  will be able to drive three times as many LEDs as  FIG. 30 . 
     NTC Regulatory Circuit Design 
     A light fixture regulatory circuit can also be design with negative thermal coefficient printed (NTC) traces.  FIG. 31  shows one such configuration that uses three NTC traces  350 ,  352 ,  354 . These three components may be connected in series in circuit G. Similarly to the arrangement of  FIG. 28 , jumper  310  may be used across circuits G and H, and jumper  312  may be used across circuits I and J. 
     The LED driver circuit shown in  FIG. 29  can be modified to drive a fixture design as in  FIG. 32  using NTC traces. In  FIG. 29  the positive thermal coefficient traces RT 1 A, RT 1 B, RT 1 C are on the ground side of the resistances R 1 A, R 1 B, R 1 C in the voltage divider. In  FIG. 32 , the negative thermal coefficient traces RT 2 A, RT 2 B, RT 2 C are on the power side of the resistances R 1 A, R 1 B, R 1 C in the voltage divider. Since these six traces may be within a fixture, a design such as shown in  FIG. 32  may be achieved by switching connected Pins P 7 , P 10  at the input connector  280 . Because NTC traces RT 2 , RT 2 B, RT 2 C decrease in resistance as temperature rises, a rise in temperature in a fixture increases the base voltage of transistors Q 1 A, Q 1 B, Q 1 C. The currents through resistors R 2 A, R 2 B and R 2 C increase, and the PLM currents driving the LEDs in each chain would be reduced accordingly. 
     In a multiple fixture cascade mode, the equivalent values of the traces may be connected in series and would be as follows.
 
 RT 2 A  equivalent value= RT 2 A (fixture 1) and  RT 2 A (fixture 2)
 
 RT 2 B  equivalent value= RT 2 B (fixture 1) and  RT 2 B (fixture 2)
 
 RT 2 C  equivalent value= RT 2 C (fixture 1) and  RT 2 C (fixture 2)
 
 R 1 A  equivalent value= R 1 A (fixture 1) and  R 1 A (fixture 2)
 
 R 1 B  equivalent value= R 1 B (fixture 1) and  R 1 B (fixture 2)
 
 R 1 C  equivalent value= R 1 C (fixture 1) and  R 1 C (fixture 2)
 
       FIG. 33  illustrates an alternate LED driver circuit embodiment that is similar to the single driver circuit design shown  FIG. 30 . The embodiment of  FIG. 30  may be modified to drive an LED fixture circuit design as in  FIG. 31  but with NTC traces. PTC traces RT 1 A, RT 1 B and RT 1 C in  FIG. 30  may be replaced by NTC traces RT 2 A, RT 2 B and RT 2 C and switched in position with resistances R 1 A, R 1 B and R 1 C. The principle of LED current regulation may be similar to that shown in  FIG. 32 . 
     Both PTC and NTC traces may be applied to the circuits of both  FIG. 32  and  FIG. 33 . In such cases, the resistances R 1 A, R 1 B and R 1 C in these figures may be replaced with PTC traces RT 1 A, RT 1 B, RT 1 C and leaving the NTC traces RT 2 A, RT 2 B, RT 2 C in place as shown in the figures. With this modification, the voltages at the bases of transistors P 8  or P 9  would rise at a much faster rate when LED temperature rises. This can be thought of as a “push and pull” effect. 
     Type A Connector 
       FIG. 34  shows a preferred, type A connector ( FIG. 1 , item  24 ). This may be a female connector  160  with holes  162  and a connector guide  164 . The connector may be used for interconnection between fixtures. The number of pins for this connector would depend on the choice of the driver circuit selected. Other connectors may be used. 
     Type B Connector 
       FIG. 35  shows a preferred, type B connector  170 . This may be a male connector with pins  172  that mate with pins of a female connector (e.g.,  FIG. 34 , item  160 ). Other connectors may be used. 
     Bracket Latch 
       FIG. 36  shows a preferred bracket ( FIG. 1 , item  12 ) which may support a fixture and/or secure two fixtures at their joints. Other brackets may be used. 
     Intelligent Lighting Fixtures 
       FIG. 37  shows a concept of intelligent lighting. The concept will be discussed here in the context of a building, but it may also apply to other location, including outdoor spaces, and the use of a building as a descriptive example is not intended to limit applicability. 
     People in a lighted region would wear devices for sensing location, such as wireless RFID badges or chain tags  602 ,  604 ,  606 ,  608 ,  610 . Some may carry intelligent personal devices  638 ,  640 , such as cell phones, personal digital assistants, remote controls, or other devices not yet invented with capability for performing location determination functions as discussed further below. Intelligent lighting fixtures  612 ,  614 ,  616 ,  618 ,  620 ,  622 ,  624 ,  626 ,  628 ,  630 ,  632  each preferably has a unique identifier. Fixtures may be connected to one or more power distribution centers  634 , which in turn may receive power from any source, such as a utility power grid  642  or local source. Local sources may include generators, photo-voltaic panels, wind turbines, batteries or other sources now in existence or not yet invented. A computer  636  may be connected to the power distribution controller  634 , such as by Ethernet or other connection. The computer  636  may store and process information obtained from and/or used in the system, including but not limited to information pertaining to, or received from, lighting fixtures, badges, intelligent personal devices, power distribution centers, etc. 
       FIG. 38  shows elements of a room layout which will be used as an example for discussing a theory of operation for implementing intelligent lighting. (The use of a room as an example is not intended to limit applicability of the intelligent lighting concept.) Light fixtures  700 ,  702  and occupants  704 ,  706 ,  708  form a network which collects occupant location information, such as time-stamped measurements of occupant position. In an illustrative example shown in  FIG. 38 , two lighting fixtures  700 ,  702  are spaced a known distance “R” apart. Beneath fixtures  700 ,  702 , three persons  704 ,  706 ,  708  are shown, which for this discussion may be assumed to be on the same floor or other level. The relative distances K, O between light fixtures  700 ,  702  and a first occupant  704  preferably are measured in real time as will be discussed further below. Absolute positions of fixtures  700 ,  702  preferably are known. Triangle RKO defines an absolute location of the first occupant  704  relative to a frame of reference of the fixtures. Similarly, triangle RPQ defines the absolute location of a second occupant  706  with respect to the two light fixtures  700  and  702 . In this way, positions may be determined for all occupants with direct communications to any two fixtures. 
     For occupants that do not have direct communications with two fixtures, such as because of obstruction or interference, position may be determined with reference to any other occupant having a known location. For purposes of illustration, assume in  FIG. 38  that an obstruction blocks a direct signal path from a third occupant  708  to a lighting fixture  702 . The position of the third occupant  708  can be determined indirectly through either triangle KLM or triangle MNQ. When absolute positions of the first two occupants  704 ,  706  are known; the absolute position of the third occupant  708  may be also obtained. 
     Once a position determination network is established and occupants&#39; locations are defined, occupant movements may be determined. One way would be to update a time-dependent network map and calculate rates of change in the triangles defined by the network map. Such method of motion detection using two-way radio determination may be more accurate and useful than using traditional infra red (IR) detectors that only detect motion. Such detectors typically “time out” if they do not detect motion for a period of time and shut off their light, even though an occupant may be present. 
     A network map allows for coordination of multiple light fixtures to provide improved light coverage for all occupants. In the example above, occupant  708  does not have direct sensing path with light fixture  702 , which implies that light from this fixture might be blocked from reaching that occupant. The system may control other fixtures to achieve desired lighting levels for that occupant. For a very large space, such as a conference room or exterior space, all the lights may not turn on if only a small section of the space is occupied. For example, if a company receptionist assigns a badge to visitor and enters into the system a destination location, the badge and the lighting fixture can form part of a system for navigating the visitor to the destination, such as by raising illumination on the path ahead of the visitor, and lowering illumination along diversionary paths. 
     In the past, traditional light sensors may have been combined with IR motion sensors with settings for a light threshold level, turn-on time for a timer, and motion sensitivity level. In such combinations, the power circuits would have been switched completely off if the ambient light exceeded a threshold or motion was not detected during the turn-on timer setting. In comparison, an improved, intelligent lighting fixture offers continuous level control of room brightness in real-time with one of the following methods:
         a) Brightness information on the occupant may be collected from wireless badges with photo sensors, cameras in cell phones, portable smart devices with a brightness calibration application, or other sensors. This information may be fed back to the lighting system through an information network and may be a more accurate way for measuring the light level needed by occupants rather than measuring at fixed wall sensors. The network can determine a level in lumens needed for each occupant and coordinate all lights in the vicinity to provide improved lighting.   b) Wall photo sensors may be wired directly to a fixture dimming circuit or indirectly using a network, such as a power line network, to provide light level information from wall sensors to be fed back to the light fixture controller.
 
In a scenario where no light sensors are present, the lighting system can estimate its light level by estimating a light output power required for known distances between the occupants and the light fixtures.
       

       FIG. 39  illustrates an exemplary control algorithm for light brightness. A light fixture  720  and ambient light both may illuminate a light sensor  728 . A comparator  726  may determines one or more light threshold levels, such as a minimum and maximum level, or a desired average level. If the light level increases beyond a threshold, a light dimmer may be activated. There may be a time delay  724  between the light dimmer control  722  and the light sensor comparator  726 . 
       FIG. 40  shows an example of a light sensor circuit, which may use an Intersil ISL29001 sensor  742  sensor, which has a light sensing range of about 0.3 lumens to 10,000 lumens, with infrared filtering and 50/60 Hz rejection. Such a sensor has light measurement range from about 0.3 Lux to about 10,000 Lux. It also has infrared rejection and rejection of light fluctuations in the range of about 50/60 Hz. Other sensors may be used. The sensor preferably reports to a master microcontroller  740  through an I2C bidirectional serial communication port. I2C communication uses two open drain lines: a serial clock line  746  and a serial data line  744 . Each line may be pulled to the line voltage Vdd via resistors  750 ,  752 . A microcontroller example may be the Texas Instrument MSP430FG4619. Such a controller has 120 KB of Flash RAM and 4 KB of ROM and has General Purpose ports for driving LCD displays, I2C communication devices and switches. Other devices can be used, including but not limited to a smaller capacity microcontroller MSP430F2013. 
     Powering A Light Sensor 
     In the example of  FIG. 40 , the illustrated microcontroller  740  has an output port  748  which may be optional if the light sensor is to be powered all the time. A resistor  754  may tie the Power Down Pin PD to ground to ensure the light sensor is ON. However, if the light sensor is to be turned off for power savings, then the port  748  may be pulled high. 
     Communicating With A Light Sensor 
     Once the light chip is in an “ON” state, the microcontroller serial clock port  746  may drive the serial clock line SCL. An ISL29001&#39;s I2C address may be hardwired internally as “1000100”. I2C transactions begin with the Master asserting a start condition (SDA falling while SCL remaining high). The master drives the following byte to provide a slave address and read/write bit. This particular light sensor requires a minimum of 100 ms for each bit and therefore determines its fastest update time. Other devices and protocols may be used. 
     IR Rejection 
     A light sensor may be used with a wide spectral response, such as from 400 nm to 1000 nm. IR rejection may be a consideration since many light sources have high presence of IR and these IR sources can give an apparent brightness to which the human eye does not respond. The ISL29001 light sensor may be capable of performing IR rejection because: it has two photodiodes D 1  and D 2 . One diode D 1  may be sensitive to both visible and IR light (400 nm to 1000 nm), while the other diode D 2  may be mostly sensitive to only IR light. For sensors such as this, a light measurement may be made for the visible range if the light level readings from both photodiodes are used according to the following equation:
 
 D 3=1.85*( D 1−7.5* D 2)
 
       FIG. 41  illustrates an intelligent light fixture controller system with two types of network capability: power-line network and wireless network. A power-line network links together smart devices connected to a common power line. A wireless network connects both portable and other wireless devices within its RF range or proximity. A power line network potentially has a longer range than a wireless network. 
     Power-Line Communication 
     Since light fixtures usually draw power from a shared AC power source, power-line networking may be suitable for controlling intelligent lighting fixtures. A power-line network may be based on the concept that the power source itself is a communication channel for the network. In  FIG. 41 , a PT/CT transformer  552  may be a signaling power-line impedance matching transformer. It may be the gateway for a low power controller block  580  to communicate with another power-line network device using the same AC source. 
     A preferred low power controller block  580  draws its power from an energy efficient AC/DC Power Supply  578 , which may be directly connected to an AC power source  556  that preferably is powered at all times regardless of whether the LED lights of the fixture are powered. A preferred controller block  580  has a programmable microcontroller at its core with EEPROM  536  storing a unique ID, a program, a Micro-database  598 , and a Real-Time Clock  592 . It may have several additional functional blocks, such as: Analog to Digital Converter (ADC)  590 ; Digital to Analog Converter (DAC)  538 ; Power control with output transistor  544  capable of driving a relay  558 ; Digital I/O ports  596  for driving an LED driver  568 ; wireless Digital I/O ports for a Wireless Network interface  546 ; Digital I/O ports for a Sensor Network  548 ; and ports for a 2-way Power-line network  594 . This micro-controller system preferably performs some or all of the following functions:
         a) Line Current Measurements—The micro-controller may sense the current in the AC source circuit mains  556  through an Isense port  542  by measuring the voltage across a sensing resistor Rsense  554  through the Analog to Digital Converter  590 .   b) Line Voltage Measurements—The micro-controller may sense the voltage across the AC source circuit mains  556  through an accurate voltage divider resistor network  550  and picked up by the controller&#39;s Vsense port  540 .   c) Line Power Measurements—The micro-controller may sense both incoming voltage and current in real-time, which allows power consumption to be computed. In the United States, the power system frequency is 60 Hz. If the sampling is performed on both current and voltage at least once every 131 uS, which is faster than 4.32 kHz, the real and apparent power can be calculated within an accuracy of 10 degree of the phase.       

     
       
         
           
             
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             d) Power-line Communications—The micro-controller may have a bidirectional ability to communicate with other power line network devices and a central control system through two-way Power-line network ports  594 . The power line network sends data via a Transmit TX driver  572 , and receives commands via a receive driver RX  574 . The power line network modem may be isolated electrically and protected by blocking capacitors  576  and PT/CT transformer  552 . 
             e) Fixture Power Control—The micro-controller may have an output  544  that controls a power relay  558 , which in turn controls the AC input power to drive the LED fixture  570  via a rectified power bridge  564 . The rectifier in turn provides power to an LED Power Supply  566  and a subsequent LED driver  568 , which has driver controls directly controlled by controller  580 . Examples of LED driver integrated circuits are LM3414HV, LM3464, LM3445, all from National Semiconductor. Other drivers may be used. 
             f) Temperature regulation—The micro-controller may have a sensor control port  548  that allows temperature sensors  582  to monitor the temperatures of the LEDs mounted on the LED light strip  570 . 
             g) Real-Time Clock—The micro-controller may have a real-time clock RTC  592  that runs independently to keep track of time. It may synchronize occasionally with a central clock through the power line-network. In addition, the power distribution center/Power line network center and controller ( FIG. 37 , item  634 ) may synchronize with an external reference clock, such as atomic clock time, time zone, daylight savings time and weather information from its internet access URL sites to anticipate times for which a location may be getting ambient light. 
             h) Wired sensors—The micro-controller may have sensor control ports  548  which allow input from wired sensors  562 , such as an ambient light sensor circuit illustrated in  FIG. 40 . The interface shown in  FIG. 40  may be serial I2C communication. These wired sensors may be programmed as slave devices, and the micro-controller may be programmed as the master device. The I2C communication architecture allows many devices to share a common bus. Each device may be distinguished by a unique device address. Other wired sensors, such as motion sensors, can share this bus. A temperature sensor  582  for a lighting fixture can be added to this sensor control for dimming the light with closed loop feedback. This improves the life of the lighting system. 
             i) Wireless network controller—The micro-controller may have a wireless network port  546  which may be connected to an optional wireless module  560  that has six connections similar to those shown in  FIG. 46  and runs a program flowchart similar to the one illustrated in  FIG. 52 . Such a wireless module  560  may be implemented with a wireless network stack, which allows a flexible dynamic multilink broadcast network scheme described further below. Such a network scheme overcomes a limitation of end devices not being able to communicate directly with other end devices, and it has freedom to join a very large network, such as a Zigbee network. Such a scheme may be implemented using a modified SimpliciTI network stack, and this device may be assigned as an “Access point.” It preferably would be powered at all times. 
             j) Wireless portable Devices—Portable wireless devices may have input buttons (switches)  588 , screen (optionally a touch screen), and input sensors  586 . A portable device can have a form factor as simple as a name tag (mobile tag) similar to one illustrated in  FIG. 50 , with a program flowchart such as one shown in  FIG. 49 . An exemplary circuit diagram is illustrated in  FIG. 46 . That example uses a six-connection interface that allows a portable controller  584  to communicate wirelessly with the micro-controller  580  via a wireless module  560 . There can be one or more portable wireless controllers, and they all preferably would have unique addresses and may be assigned as “End devices” similar to a Zigbee network. They may communicate with each other automatically and establish a network by a join-network command and executing a program flowchart, such as one illustrated in  FIG. 49 . A portable controller can be larger, like a handheld remote controller, and be more sophisticated to include a large touch screen and keyboard entry. It could include a network interface with cell phones, iphones, etc. Under such an arrangement, the cell phones and iphones could be used to communicate with the controller  580  running a custom application program designed for lighting control. In this case, users could use their cell phones, iphones, ipads, etc. to be their portable light controller.
 
Situation Awareness Dynamic Lighting Illumination Plan
 
           
         
       
    
     The ability to identify occupants and their activities allows cost-saving illumination plans, especially in large rooms with several light fixtures and open spaces.  FIG. 42  illustrates an example where an occupant  768  may be stationary under, and illuminated only by, a single light fixture  762  with an exemplary illumination light level of three hundred (300) lux in the vicinity of the occupant. The other three light fixtures  760 ,  764  and  766  may not be turned on. The light level would be lower at locations away from the occupant. 
       FIG. 43  illustrates an alternate plan where the occupant can choose a moderate savings light illumination plan B. In this example, the two neighboring lights  780  and  784  are illuminated at light level of two hundred (200) lux, slightly dimmer than the immediate light fixture  782  above occupant  788  illuminating at light level of three hundred lux. This allows the occupant to feel not as lonely or isolated. A fixture  786  farther away may remain off to provide energy savings. 
       FIG. 44  illustrates an alternate plan where the occupant can choose a nominal savings light illumination plan. In this case, the two neighboring lights  800 ,  804  are illuminated at light level of three hundred (300) lux, just as bright as the immediate light fixture  802  above occupant  808  illuminating. This allows the occupant to feel good. Fixture  806  remains off as to provide energy savings 
       FIG. 45  illustrates an alternate plan where the occupant has chosen a nominal savings light illumination plan C as he/she begins to walk in a direction to the right. In this case, a neighboring light fixture  820  behind the occupant may be reduced to a two hundred (200) lux light level, and light fixtures  822 ,  824  above and immediately in front of the occupant  828  may be illuminated at a light level of three hundred (300) lux. A light fixture  826  farther ahead but removed from the occupant  828  may turn on to a light level of two hundred and fifty (250) lux. This would allow the occupant to see clearly in the direction where to walk and still provide energy savings 
     The use of two kinds of communication networks, a power line and a wireless network, allows long distance remote control and interactive response to mobile occupants of the room.  FIG. 46  illustrates elements of one exemplary embodiment using a Texas Instruments CC2500 wireless low power 2.4 GHz RF transceiver chip  902 , which operates in a frequency band 2400-2483.5 MHz ISM (Industrial, Scientific and Medical) and SRD (Short Range Device) Frequency Band. It allows sixty four (64) byte transmit/receive FIFOs and can be controlled via a  4 -wire SPI interface (SI, SO, SCLK and CSn) serial communication protocol with SPI addresses from 0x00 to 0x2E. Such an interface may be used to read and write buffered data. A 16 bit RISC CPU  900  from an MSP430 family of microcontrollers may be used that provides two additional connections to the transceiver chip  902  GD02 (an Optional Digital output pin for Clear Channel Indicator), GDO0 (Atest, A digital output pin for test signals), CSn and SI for the I2C. The microcontroller  900  preferably operates in a master mode while the RF transceiver chip  902  operates in a slave mode. The transceiver may use a 26-27 MHz crystal  904  in a parallel mode oscillation. Typical values for the two crystal loading NPO capacitors  906 ,  908  may be 15 pF˜27 pF connected one end to ground. There may be two RF balun/matching capacitors  910 ,  918  with values of 1.0 pF+/−0.25 pF respectively. There may be two RF balun/matching inductors  912  and  914  with values 1.2 nH+/−0.3 nH. There may be one RF LC filter inductor  916  with a value 1.2 nH+/−0.3 nH. There may be two RF LC filter/matching capacitors  922 ,  924  with values 1.8 pF+/−0.25 pF and 1.5 pF+/−0.25 pF respectively. There may be two RF balun DC blocking NPO capacitors  926 ,  928  with values 100 pF+/−5%. A 1% resistor  932  with typical value of 56K ohms may be used for an internal bias current reference.  FIGS. 47, 48 and 49  illustrate exemplary pin and port assignments for the circuit if  FIG. 46 . 
     Multilink Broadcast Wireless Network 
       FIG. 50  shows an exemplary flowchart for a microcontroller program in a mobile Tag unit. When a tag is powered on, the tag may first initialize a radio  1000 . Then it may initialize a wireless network  1002 . The wireless network may depend on the network protocol stack that is loaded. A SimpliciTI stack is preferred because a Zigbee stack may be much larger, and EEPROM memory space may be limited. All mobile tags may be assigned as end devices, and the devices at the light fixtures may be fully powered access points. Once a stack is established, the mobile tag broadcasts its presence and listens for a link  1004 . The broadcast command allows all devices within the reception range to respond with a link action. If there is an access point within its range, the mobile tag will join the network  1006 . This may be a typical network join. The access point should generate a member list of all devices in the network. Unlike a traditional join in a Zigbee network, a broadcast may also allow a multi-link broadcast network in which end devices (mobile tags) can communicate with other end devices and access points. Such a broadcast capability may be supported by SimpliciTI. An advantage would be that the network can grow to any size and dynamically be formed without all the limitations in Zigbee or SimpliciTI. It would allow all mobile tags and all access points in lighting fixtures to form a fully functional network. It preferably would allow a network formation in the absence of an access point. Mobile tags can detect each other&#39;s presence when they become members of this network. 
     Databases and Proximity Map 
     Each tag should exchange its unique ID  1008  with each other tag and with access points. An access point preferably will record the ID and the join time  1010  of a the mobile tag based on a Real-Time Clock (RTC) in its local micro database and also record the same event in the tag&#39;s micro database. In turn, the access point in the light fixtures may utilize Received Signal Strength Indicator (RSSI) information to calculate new proximity (“vector distance”) map information with each of the mobile tags present. The access point then preferably sends this information to the central network server through either a power-line connection or a wired/wireless Ethernet network. The server preferably will aggregate and consolidate new information into a global proximity map in a SQL or other database. 
     A proximity map in matrix format stored in mobile tags and global proximity map generation is described in detail in the U.S. Pat. No. 7,598,854. Member&#39;s IDs, join times, and proximities may be recorded in the sever database. The server may use other databases to perform additional functionalities such as:
         a) Implement personalized lighting plan preferences. The ability for devices to respond is discussed in patent application USP 20090327245.   b) Maintain time clocks for hours employees worked at each location. This facilitates workflow processes and improves productivity.   c) Update a program, such as Microsoft Outlook (tm) program, of the present location in the building of a tag. This could, for example, facilitate the calling of an impromptu meeting.   d) Retrieve identities of individuals who come in contact with each other and allow a trace back to implement disease surveillance intervention policy especially in a flu season, such as illustrated in U.S. Pat. No. 7,598,854.   e) Allow real-time asset tracking and management for items bearing a tag and prevent critical items leaving the building. Lights may turn on and alarm sound if items are moved. This improves security. Asset management and inventory status notification is also discussed in U.S. Pat. No. 6,816,074.   f) Provide building security, track visitors, and issue alerts of unauthorized movements.   g) Provide automated directions for visitors or new employees with a building floor plan, which is also discussed in US patent application, USP 20090327245.
 
Lighting Plan
       

     With continued reference to  FIG. 50 , a mobile tag may call upon an access point to update its light plan preference (if selected on the buttons of the tag) or to retrieve a preset preference in the master database  1012 . Then a tag may request an access points to regulate LED lights according to the chosen light plan  1014 . A light level plan may be selected based on one or more of several parameters, including but not limited to distance of the tag from a light, time of day, calendar date (including daylight savings), light sensor values (fixed and/or mobile), and positions of lights relative to one another, electricity tariffs (which may change with time of day), etc. Other parameters may be used. Distance measurements may be computed from RSSI values, which may be the measured RF input signal levels in the channel based on transmission gains in the RX chain at the transceiver. In RX mode, an RSSI value may be read continuously from the RSSI status register until the demodulator detects a sync word. 
       FIG. 51  illustrates an exemplary space, such as a room, hallway, sidewalk, street, etc. where there may be two light fixtures  850 ,  854 ; and a calibrating wireless unit  856 . If the distance BC between the two fixtures is known, and if the calibrating unit  856  is positioned at a known location relative to the fixtures (i.e., BD and CD), then the corresponding RSSI values obtained for the fixtures may be used as a reference. Once the RSSI values are calibrated, a person&#39;s location  852  can determined from the RSSI values using the geometrical relation AB 2 =BC 2 +AC 2 −2×BC×AC cos (Angle BCA). 
     In addition, if there is a light sensor on the tag, the tag may report the light level to an access point ( FIG. 50 , item  1016 ). Access points may update their respective LED light output levels according to the received light sensor reading  1018 . A tag may check for RSSI value changes with respect to an access point  1020 . A change in RSSI value would indicate motion, and an access point may determine whether the tag is still within a range, such as within the room confines  1022  or if the space is outdoors, within some other range limit. If a tag is still within range, the tag may request an access point to recalculate its lighting plan  1024 . The process of  FIG. 50  would return to step  1014  to request an updated light output according to the applicable plan. If it is determined that the tag has left the room  1030  or relevant space, then the access point may record the tag&#39;s disjoin time from the network and update the database  1032 . The access point may return to a periodic broadcast mode and listen to the link  1004  for the presence of any tags. In the specific case of an indoor space, a tag&#39;s leaving one room and entering another room presents another network formation event, and steps described above may be repeated at a different access point. (The same may occur in outdoor spaces.) A network from which the tag departed may alert a network to which the tag enters as to that tags lighting plan so that the person will have continuous and agreeable light upon passing through a doorway or otherwise transitioning location. 
       FIG. 52  illustrates a mobile name tag, which may be an end device. A tag may be implemented with active RF technology as shown in  FIG. 46 , though other implementations may be used. A tag may bear the name of a person to whom it is assigned, such as “Amy Lee”  1202 . A light plan  1204 , such as “P 3 ,” may be displayed on a screen  1206 , which allows user to know the current light plan. This display  1206  can be implemented using LCD technology, LED technology, E-Ink technology, or another technology. E-Ink technology has relatively low power consumption since it consumes power only during switching. A tag may have various buttons  1208  used for selecting a light plan and other operations. A selected light plan  1204  may be called a “light preference”. Above the screen  1206  may be an opening  1200  through which a light sensor may measure ambient light. A strip antenna  1210  may be implemented using a flexible circuit technology and may be embedded in the plastic cover film of the tag. 
       FIG. 53  shows a flow chart for an exemplary access point in a light fixture. In a nominal circumstance, the microcontroller and the radio preferably are switched on in a low power or occasionally a sleep mode. If the unit has never been powered up before, or after a power failure, it may go through an initialization step  1100  for the radio and an initialization step  1102  for the network. The radio may be listening  1104  for someone to enter the access point&#39;s service area, such as a room, corridor, sidewalk, street way, etc. An initial condition may be for the mobile tag to be in a broadcast mode. Upon detecting a tag, an access point preferably would provide a link ID  1106  for the new tag to join the network. In a broadcast mode, mobile tags may communicate with each other and join into a network among themselves. Each tag and access point preferably exchanges its ID  1108 , captures all the IDs in its vicinity, and records these events in real-time. The information may be saved in a proximity map in matrix format in one or more micro databases. Another copy of the information may be sent to a network server and merged into a master database  1110 . Mobile tags each may retain a condensed version of portions of the proximity map. 
     An access point preferably then checks for any new preference selected by a mobile tag  1112 . If yes, the access point preferably updates a preference database at the network server  1118 . Otherwise, the access point may retrieve a preference or a default choice from a network server database  1114  if the tag does not have an existing one. 
     An access point may read ambient light levels from existing tags that have sensors  1120 . A fixture may then update the light output levels according to a lighting plan and optimize the output to measured light levels  1122 . This dynamic lighting control may be capable of responding to changes in the lighting due to external environment. 
     An access point may monitor changes in RSSI with the mobile tags  1124  in order to detect movement of occupants. In the absence of RSSI value changes  1124 , the access point may optionally go into a low power sleep mode  1134  for a time until waking up  1136  and returning to a step  1104  of listening for new tags. But if an RSSI value changes, the access point may evaluate the movement. For example, the microcontroller may determine whether a mobile tag is leaving the room  1126  or service area. If a tag did not leave the service area, then the microcontroller may continue to coordinate with other vicinity lights to output a more desirable light level for the occupant  1128 . An access point may continue to monitor for changes until the occupant leaves the service area. When a tag leaves the service area  1130 , the link ID may be removed to indicate a disjoin of the network. The disjoin event may also be recorded and entered into the network server database  1132 . The access point may then return to the step for looking for a new mobile tag entering the room  1104 . 
     If there are existing mobile tags in the room and there are no movements, an access point may check for any change in request for a light plan  1116 . In this manner, the light fixture may be controlled to respond to requests from the occupant. 
     It should be noted that the access point also may report the energy consumption and time of usage  1110 . 
     Master Network Server 
       FIG. 54  shows an exemplary circuit for a master network server, which draws power from AC power source  1250 . Such a server may use a personal computer, a laptop, an embedded PC, or other computing machine. It may through a USB bus or other interface control lighting fixtures, and it may be used to program portable controls or wireless tags. A preferred server may communicate with all lighting fixtures through a power-line network and wireless network. Such a server may maintain databases of lighting plans, lighting preferences, and proximity maps, as well as histories of network events and energy usage. One exemplary master network server may be comprised of the following components:
         a) Controller system  1258 . One exemplary system may be based on a Texas Instruments MSP430 family of controllers with higher performance than controllers in lighting fixtures. It may measure its own power/energy consumption and that of an associated PC via an Analog to Digital Converters (ADC)  1262  with high voltage differential ports  1260 ,  1264  for measuring voltages across known resistances, Rsense 1   1252  and Rsense 2   1254 . A Power-line network  1276  may include an analog to digital converter (ADC) to receive analog signals through receiver  1272 . It also may transmit Pulse Width Modulation (PWM) signals using a Digital to Analog Converter (DAC)  1270  through a transmitter  1274 . A stored memory EEPROM  1268  preferably is sufficiently large to maintain a micro-database, keep its unique ID, store a wireless program stack, and store its program. A stable crystal may be included to provide an accurate, on-chip clock signal  1286  and timing for a USB controller  1320 . A Real-Time-Clock program  1266  preferably maintains time for the controller and all its network members. A higher accuracy clock may be achieved via synchronization with the PC, which in turn synchronizes with an atomic clock on-line via the Internet or other communication channel. In addition, the power distribution center/Power line network center and controller ( FIG. 37 , item  634 ) may collect information about the local time zone, daylight savings time and weather information from its internet access URL sites to anticipate the times for which a location may be receiving ambient sun or sky light. This is beneficial for designing an appropriate lighting plan and also anticipating future power demand. If a facility uses solar panels and a battery storage system to power its lighting system, an appropriate energy savings plan can be chosen to reduce power draw during peak or other critical times. Alternately, it can formulate a light plan that eliminates energy needs from the power grid by not depleting all the stored battery energy. Such a controller preferably draws its power from an isolated AC/DC power supply  1256 .   b) A personal computer or laptop or an embedded PC, preferably with a USB2.0 or above port  1308  drawing its power from a power adapter  1306  and AC power connector  1304 . In addition, the computer USB2.0 serial port communicates with a USB Controller  1320  via a USB receptacle Type B  1296  via a transient port suppressor  1302 .   c) USB Controller  1320  communicating serially with micro controller  1258  via signal lines SIN, SOUT, BRXDI and BTXDI, and a UART  1284 . The USB controller  1320  and voltage regulator  1290  may be reset by a reset signal  1292 .   d) EEPROM  1288  expands the size of the controller memory. The EEPROM may be a Catalyst part CAT24FC32V1.   e) USB Port transient suppressor  1302  prevents voltage surges on the USB port. The USB Port suppressor may be a Texas Instruments part SN75240PW.   f) Voltage regulator  1290  preferably regulates the voltage from the USB bus from the computer to a voltage  1294 , Vcc=+3.6 volts. It draws its power from the USB2.0 port via a VBus  1310 , which is connected to the USB2.0 receptacle  1296 . The voltage regulator may be a Texas Instruments part TPS77301DGK.       

     A wireless network may be constructed from a wireless network module  1280  similar to  FIG. 46  with its TX port ( FIG. 46  item  942 ) and RX port ( FIG. 46  item  944 ) communicating with the I/O ports  1278  on the microcontroller  1258 . 
     Master Network Server Flow Chart 
       FIG. 55  shows an exemplary Master Network Server flow chart. The server may first initialize a Radio  1400 , along with a wireless network and a power-line network  1402 . Initialization may involve the stack loading. Next, the server preferably communicates with all the devices currently active in the network  1404 . It may then determine whether there is a discrepancy in the network devices compared to its last known database record  1406 . If there is a discrepancy, the server may determine whether the discrepancy involves portable devices  1408 . In step  1410 , the server may determine whether the current number of devices is greater than or less than the prior number recorded in the database. If the current number of portable devices is less, then the server attempts to determine to what other location the device may have moved  1412 . If the device is found in another room or other location, the server updates the network table  1416 . If the device is not found  1418 , the server attempts to determine whether the device may have left the service area through an exit at the last location where the device was detected. (This step may be modified according to service area, e.g., if the service area is outdoors.) If that location has an exit, the server may place device on a list of devices that have left the service area  1420 . This list is not a list of missing/failed devices, but may be a list of devices assumed to be active and awaiting return to the service area. If there was no exit from the devices last registered location, the device may be placed on a list of missing/failed devices  1422 . The missing/failed list is kept, and an alert may initiated for a service manager to check whether the battery is dead or the device is inoperative. At this point, the program may return to point “A”, which is found in  FIG. 56  and which is part  2  of the Master Network Server flow chart. 
     In step  1416 , after the network table has been updated, the process may proceed to step  1424  to check for any new requests for changes to a lighting plan. If a change has been requested, the process may proceed to step  1426  to implement the requested change. After implementing the requested change, or if no change was requested, the process may update the server database in step  1430 . (If no request for a change was made, the server may nevertheless update the database with a time stamp and other information, such as the location of the employee, etc.) The process may return to point “A”, which is found in  FIG. 56 . 
     In  FIG. 56 , point “A” is a real-time time synchronizing step  1450 . This synchronization preferably is carried with all non-wireless devices through the server power-line network. Wireless portable devices preferably synchronize through the wireless intercommunication. In step  1452 , the server may communicate and update a measurement of energy usage for some or all of the devices on its network and store the updated information in a master database. In step  1454 , the server may update and consolidate proximity maps in the database. In step  1456 , the server may carry out any service requests made by any devices on its network list. For example in step  1458 , the server may update an energy usage chart according to a timetable. The server may update employees&#39; actual time clocks and work dates for accounting purposes. (This may be a more accurate way of recording work hours based on both location and building. Sometimes, an employee may have different jobs in different buildings, and they can clock for different rates automatically by this system.) The server may analyze light preference statistics and energy consumption patterns, and the server may correlate the actual daylight of the season. This capability allows behavioral patterns to be identified and energy savings policies to be implemented. Worker efficiency studies can also be performed, and lighting policies may be adjusted for productivity rather than energy savings if this should be the policy of the building operator. Compromise workflow solutions can also be found with this kind of system, such as optimizing for performance during some time periods and for energy efficiency during other periods. 
     In step  1460 , the server may update reports. Upon completion, the server network may enter a low power sleep mode  1462  and wake up upon request or after a pre-determined time. Wake up upon request may be initiated upon installation of a new device. Step  1464  allows for installation of a new device. Step  1466  allows for new device registration. In the absence of new devices, the program can return to point “A.” 
     In  FIG. 55 , a step  1408  labeled “B” identified a situation where a new device has entered the system, but the device is not a portable device. This could be, for example, a situation where a new light fixture has been installed. However, this new fixture may be added to the system according to steps illustrated in  FIG. 57 . A step  1500  may determine whether the new device is a power-line device. If it is, the device may be registered  1508  in the master database, and the server process may return to point “A” in  FIG. 55 . If there was no new power-line device, but if a device was removed, the server may determine whether a device is to be decommissioned  1502 . If the device is to be decommissioned, the server may remove it from the database. If the device is not to be decommissioned, then the server may identify it in the database as missing and initiate an alert to a supervisor of the building or other person for resolution. The process may then return to point “A” in  FIG. 55 . 
     Alternate AC Voltage and Current Measurement Solution 
       FIG. 58  illustrates an alternate circuit to the one shown in  FIG. 41 . In the circuit of  FIG. 41 , a microcontroller system  580  measured both AC voltage and AC current. In contrast,  FIG. 58  shows that a circuit may use a dedicated Maxim integrated circuit MaxQ3183  1554  for both AC voltage and current measurements and communicating measured values back to a microcontroller system  1560 . In this arrangement, the microcontroller need not directly interface to the power-line voltages and be subject to complications associated with voltage spikes and demands for isolated power and ground. The Maxim IC may also provide various power measurements, such as apparent and real power, which the microcontroller system  1560  would no longer need to compute. This arrangement would free the micro-controller system to perform other functions. Similar implementation can be for the Master network server shown in  FIG. 54 . 
     In the circuit of  FIG. 58 , the Maxim chip  1554  measures AC line voltage  1550  through voltage dividing resistors  1558  The chip  1554  may measure current and power factor through a transformer  1556  connected to its Vcomm, ION and IOP pins. The chip may communicate with the microcontroller  1560  via an I2C bidirectional serial communication port. Power-line communications in the circuit of  FIG. 58  preferably are the same as in the circuit of  FIG. 41 . The circuit of  FIG. 58  would increase the capacity of the microcontroller to perform other functions. 
     The embodiments described above are intended to be illustrative but not limiting. Various modifications may be made without departing from the scope of the invention. The breadth and scope of the invention should not be limited by the description above, but should be defined only in accordance with the following claims and their equivalents.