Abstract:
An apparatus and method for providing dimming control of an electronic ballast circuit that includes a electronic ballast circuit that is electrically connected to a plurality of input voltage terminals that can receive alternating current and the electronic ballast circuit is electrically connected to the plurality of fluorescent lamp terminals. There is at least one light sensor that is electrically connected to the electronic ballast circuit so that the electrical power applied at the plurality of fluorescent lamp terminals can be proportionally modified in relationship to the ambient light received by the at least one light sensor. Also, there is a plurality of switches that are electrically connected in one-to-one corresponding relationship to a plurality of resistive loads so that the electrical power applied at the plurality of fluorescent lamp terminals can be set at a plurality of predetermined lighting levels.

Description:
BACKGROUND OF INVENTION  
       [0001]     One significant problem is that the energy costs for lighting appear to be increasing. This is due to the significant expenditures required for electricity generation plants and the associated environmental problems. The Energy Policy Act of 2002 as well as efficiency standards such as ASHRAE/IESNA 90.1 and California Title 24 now mandate significant lighting power reductions. A major issue is that there still needs to be sufficient lighting to promote safety and avoid excessive strain on the eyes. The amount of ambient lighting that is currently available is typically not considered when determining the amount of energy to utilize in supplying electrical lighting. Also, there are environmental issues associated with the disposal of burnt-out fluorescent lamps. It would be very beneficial to increase the life of a fluorescent lamp to lessen this environmental problem. Also, organizations that do not attempt to reduce their energy consumption are at a competitive disadvantage with respect to organizations that reduce their energy use due to the tax credits that are now currently available.  
         [0002]     The present invention is directed to overcoming one or more of the problems set forth above.  
       SUMMARY OF INVENTION  
       [0003]     In one aspect of this invention, an apparatus for providing dimming control of an electronic ballast circuit is disclosed. This apparatus includes a plurality of input terminals that can receive alternating current, a plurality of fluorescent lamp terminals, an electronic ballast circuit, wherein the electronic ballast circuit is electrically connected to the plurality of input terminals that can receive alternating current and the electronic ballast circuit is electrically connected to the plurality of fluorescent lamp terminals, at least one light sensor that is electrically connected to the electronic ballast circuit so that the electrical power applied at the plurality of fluorescent lamp terminals can be proportionally modified in relationship to the ambient light received by the at least one light sensor, and a plurality of switches that are electrically connected in one-to-one corresponding relationship to a plurality of resistive loads, wherein the plurality of switches and the plurality of resistive loads are electrically connected to the electronic ballast circuit so that the electrical power applied at the plurality of fluorescent lamp terminals can be set at a plurality of predetermined lighting levels.  
         [0004]     In another aspect of this invention, a method for providing dimming control of an electronic ballast circuit is disclosed. This method includes applying alternating current to a plurality of input terminals that are electrically connected to an electronic ballast circuit, receiving ambient light with at least one light sensor that is electrically connected to the electronic ballast circuit, and altering an amount of electrical power applied to the electronic ballast circuit through selective activation of at least one of a plurality of switches that are electrically connected in one-to-one corresponding relationship to a plurality of resistive loads and to the electronic ballast circuit, wherein the electronic ballast circuit is electrically connected to a plurality of fluorescent lamp terminals that are capable of lighting at least one fluorescent lamp.  
         [0005]     These are merely some of the innumerable aspects of the present invention and should not be deemed an all-inclusive listing of the innumerable aspects associated with the present invention. These and other aspects will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0006]     For a better understanding of the present invention, reference may be made to the accompanying drawings in which:  
         [0007]      FIG. 1  is an electrical schematic of a dimmable ballast circuit, a light sensor and a plurality of switches in accordance with the present invention;  
         [0008]      FIG. 2  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned off, the second switch is turned off and the third switch is turned off to provide a one hundred percent (100%) lighting level in accordance with the present invention;  
         [0009]      FIG. 2A  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned on, the second switch is turned off and the third switch is turned off to provide a ninety percent (90%) lighting level in accordance with the present invention;  
         [0010]      FIG. 2B  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned off, the second switch is turned on and the third switch is turned off to provide an eighty percent (80%) lighting level in accordance with the present invention;  
         [0011]      FIG. 2C  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned off, the second switch is turned off and the third switch is turned on to provide a seventy percent (70%) lighting level in accordance with the present invention;  
         [0012]      FIG. 2D  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned on, the second switch is turned on and the third switch is turned off to provide a sixty percent (60%) lighting level in accordance with the present invention;  
         [0013]      FIG. 2E  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned off, the second switch is turned on and the third switch is turned on to provide a fifty percent (50%) lighting level in accordance with the present invention;  
         [0014]      FIG. 2F  is a enlarged representation of three (3) illustrative switches, e.g., dual in-line package switches, where the first switch is turned on, the second switch is turned on and the third switch is turned on to provide a forty percent (40%) lighting level in accordance with the present invention;  
         [0015]      FIG. 3  is a basic electrical schematic that includes a ballast circuit in relationship to an outline of a fluorescent lighting fixture with wiring connections for receiving electrical power and providing electrical power to at least one fluorescent lamp, a light sensor and a representation of three (3) illustrative switches in accordance with the present invention;  
         [0016]      FIG. 4  is a perspective view of a light sensor, e.g., photocell, mounted on a recessed fixture in accordance with the present invention; and  
         [0017]      FIG. 5  is a perspective view of a light sensor, e.g., photocell, mounted on a surface fixture in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures and compartments have not been described in detail so as to obscure the present invention.  
         [0019]     For the present invention, there are a wide variety of ballast circuits that can suffice. Nonlimiting and illustrative examples can include those manufactured by STMicroelectronics having a place of business at 39, Chemin du Champ des Filles, C. P. 21, CH 1228 Plan-Les-Ouates, Geneva, Switzerland.  
         [0020]     Referring now to  FIG. 1 , an illustrative, but nonlimiting, the ballast circuit and associated components of the present invention are generally indicated by numeral  10 . The voltage supply is preferably, but not necessarily, one hundred and twenty (120) volts. The first input voltage terminal  12  supplies voltage via a first inductor  20 , e.g., 10 mH, which is electrically connected to a first input  24  for a rectifying bridge that is generally indicated by numeral  36 . The second input voltage terminal  14  supplies voltage via a fuse  18 , e.g., rated at 3 amperes and 300 volts. This fuse  18  is electrically connected to a second inductor  22 , e.g., 10 mH, which electrically connected to a second input  26  for the rectifying bridge  36 . The rectifying bridge  36  includes a series of four diodes including a first diode  28 , a second diode  30 , a third diode  32  and a fourth diode  34 , respectively, e.g., 1N4007.  
         [0021]     The ground or neutral as indicated by numeral  16  is connected to the first input  24  for the rectifying bridge  36  via a first capacitor  38 , e.g., 1,000 pF. Also, the ground  16  is connected to the second input  26  for the rectifying bridge  36  via a second capacitor  40 , e.g., 1,000 pF. Positioned between the two input voltage terminals  12  and  14  and after the output of the first inductor  20  and the output of the second inductor  22  is a third capacitor  42 , e.g., 0.33 μF. The first output  44  for the rectifying bridge  36  is connected to ground  16  and the second output  46  for the rectifying bridge  36  is connected to a first resistor  48 , e.g., 1,000 Ω, and a third inductor  50 , e.g., 1 mH. The first resistor  48  and the third inductor  50  are electrically connected in parallel to each other.  
         [0022]     Voltage is supplied from the rectifying bridge  36  to driver and control circuits for a power factor corrector circuit  52  via voltage input  54  through a first pair of resistors  56 , e.g., 100,000 Ω, which are electrically connected in series. An illustrative, but nonlimiting example of a power factor corrector circuit  52  includes an integrated circuit designated by “L6561” manufactured by STMicroelectronics having a place of business at 39, Chemin du Champ des Filles, C. P. 21, CH 1228 Plan-Les-Ouates, Geneva, Switzerland. The voltage input  54  is also connected to ground  16  via a fourth capacitor  58 , e.g., 22 μF.  
         [0023]     A rectified voltage signal is that is proportional to the rectified voltage from the rectifying bridge  36  is applied as the input  60  to the multiplier stage of the power factor corrector circuit  52 . Voltage is supplied from the rectifying bridge  36  to a second pair of resistors  62 , e.g., 910,000 Ω, which are electrically connected in series. The input  60  to the multiplier stage of the power factor corrector circuit  52  is also connected to ground  16  via a second resistor  64 , e.g., 8,200 Ω, and a fifth capacitor  66 , e.g., 0.015 μF. The second resistor  64  and the fifth capacitor  66  are electrically connected in parallel. Input  68  to the power factor corrector integrated circuit  52  is electrically connected directly to ground  16 .  
         [0024]     There is a zero current detector input  70  for the power factor corrector circuit  52  that is connected in series to a third resistor  72 , e.g., 22,000 Ω. The third resistor  72  is then electrically connected in series to an inductive dual coil transformer  74 , e.g., 1.1 mH. The other input  71  to the inductive dual coil transformer  74  is electrically connected to ground  16 . When there is zero current flowing into the zero current detector input  70 , this will shut down the power factor corrector circuit  52 .  
         [0025]     There is an output for the error amplifier  78  and an inverting input for the error amplifier  76  associated with the power factor corrector circuit  52 . A feedback circuit is located between the output of the error amplifier  78  and an inverting input for the error amplifier  76 , which includes a sixth capacitor  80 , e.g., 0.47 μF.  
         [0026]     There is a gate driver output  82  from the power factor corrector circuit  52  that provides current to the gate  90  of a n-channel metal oxide semiconductor field effect transistor  88 , e.g., 1RF840A, through a fourth resistor  84 , e.g., 1,000 Ω, and a small signal diode  86 , e.g., 1N4148. The fourth resistor  84  and the small signal diode  86  are electrically connected in parallel.  
         [0027]     The output or source  94  from the a n-channel metal oxide semiconductor field effect transistor  88  can provide current to the input  98  to the comparator of the control loop for the power factor corrector circuit  52 . The output or source  94  from the a n-channel metal oxide semiconductor field effect transistor  88  is connected to ground  16  via a third pair of resistors  96 , e.g., 0.7 Ω, where the third pair of resistors  96  are electrically connected to each other in parallel.  
         [0028]     The previously referenced inductive dual coil transformer  74  provides voltage to a circuit to drive and control fluorescent lighting  100  via a series of three resistors  102 , e.g., 24,000 Ω, which are electrically connected in series. A nonlimiting, but illustrative example of this type of monolithic integrated circuit includes “FM2822” manufactured by Shanghai Fudan Microelectronics Co., Ltd. having a place of business at Floor 7th, Building C No. 668, Eastern Beijing Road, Shanghai, Peoples Republic of China. The series of three resistors  102  is electrically connected to the supply current input  104  for the drive and control circuit  100 . Also, the series of three resistors  102  is electrically connected to a planar zenor diode  101 , e.g., 2CW37−15A, Vz=13.8−14.9 V and Iz=5 mA. The planar zenor diode  101  is also connected to ground  16 . The supply current input  104  for the drive and control circuit  100  operates to limit voltage and prevent undervoltage with a lockout function. There is a sixteenth capacitor  238 , e.g., 0.22 μF, that is electrically connected to the supply current input  104  for the drive and control circuit  100  at one end and the other end is electrically connected to ground  16 . There are two opposing rectifiers  252  and  254 , e.g., 1N4007, respectively, electrically connected between the voltage input  54  to the multiplier stage of the power factor corrector circuit  52  and the supply current input  104  for the drive and control circuit  100 .  
         [0029]     There is a first external capacitor output  106  for the drive and control circuit  100  that is electrically connected to a seventh capacitor  108 , e.g., 0.47 μF. This seventh capacitor  108  is electrically connected to ground  16  and sets a preheat timing wherein a small current is used to charge the first external capacitor output  106  so that the voltage on the first external capacitor output  106  increases gradually from 0 volts to 4 volts. When the voltage reaches 4 volts, the preheat timing is over. There is a multiplier, e.g., five (5) times, of the amount of current that is applied to discharge the seventh capacitor  108 , then the voltage sweeps down gradually to the point where a fluorescent lamp will be ignited. This period of time is called ignition time. At the end of ignition, the voltage at the first external capacitor output  106  is set to zero. A second function is to use the first external capacitor output  106  to set the stop timing duration when the open circuit lamp voltage exceeds a predetermined level during the ignition time. The stop timing duration is equal to a predetermined percentage, e.g., one-half, of the preheat time. This function only becomes active when the ignition voltage sweeps end but remains active after that point in time.  
         [0030]     There is an external resistor output  110  for the drive and control circuit  100  that is electrically connected to a fifth resistor  112 , e.g., 62,000 Ω. This fifth resistor  112  is electrically connected to ground  16 . The fifth resistor  112  is electrically connected to the external resistor output  110  to set the preheat current. During preheat period, the voltage applied to this external resistor output  110  remains at 4 volts. After preheating, the voltage will sweep down to zero at a predetermined rate.  
         [0031]     There is a second external capacitor output  114  for the drive and control circuit  100  that is electrically connected to a eighth capacitor  116 , e.g., 100 pF. This eighth capacitor  116  is electrically connected to ground  16 . The eighth capacitor  116  is precharged to a predetermined voltage during the start-up state.  
         [0032]     There is an inductor current monitoring input  118  that is electrically connected to a sixth resistor  120 , e.g., 18,000 Ω. The sixth resistor is connected in series to both the seventh resistor  122 , e.g., 1 Ω and an eighth resistor  124 , e.g., 1 Ω. The seventh resistor  122  and the eighth resistor  124  are electrically connected to each other in parallel and are both electrically connected to ground  16 .  
         [0033]     The sixth resistor  120  is also connected via a twenty-seventh capacitor  368 , e.g., 0.01 μF, to a tri-coil transformer  126 , e.g., MX2426 and 2.5 mH, to provide current to both a first fluorescent lamp  128  at a first fluorescent lamp terminal  130  for the a first fluorescent lamp  128  and a second fluorescent lamp  134  at a second fluorescent lamp terminal  138  for the second fluorescent lamp terminal  134 . An illustrative, but nonlimiting, example of a first fluorescent lamp  128  and a second fluorescent lamp  134  includes a T8, four (4) foot fluorescent lamps that operate at 120 volts. However, numerous other types of fluorescent lamps may suffice for the present invention including, but not limited to, T12 fluorescent lamps.  
         [0034]     There is a first electrical conductor  131  that is electrically connected between the first fluorescent lamp terminal  130  for the first fluorescent lamp  128  and a first coil  125  for the tri-coil transformer  126 . This first electrical conductor  131  is electrically connected in parallel with a first combination inductor and capacitor  140 , e.g., 50 T/50 T, 3.14 mH and 0.47 μF., that is electrically connected in series.  
         [0035]     There is a second electrical conductor  133  that is electrically connected between the second fluorescent lamp terminal  138  for the second fluorescent lamp  134  and a third coil  129  for the tri-coil transformer  126 . This second electrical conductor  133  is electrically connected in parallel with a second combination inductor and capacitor  142 , e.g., 50 T/50 T, 3.14 mH and 0.47 μF., that is electrically connected in series.  
         [0036]     Current that either flows from the third coil  129  for the tri-coil transformer  126  into the second fluorescent lamp terminal  138  for the second fluorescent lamp  134  and/or current that flows from the first coil  125  for the tri-coil transformer  126  into the first fluorescent lamp terminal  130  for the first fluorescent lamp  128  induces a current to flow from the second coil  127  for the tri-coil transformer  126  into a first differential input for sensing fluorescent lamp current  147  for the drive and control circuit  100  via a thirty-fourth resistor  199 , e.g., 5,600 Ω. There is a thirty-fifth resistor  201 , e.g., 12 Ω, that is electrically connected in series with the thirty-fourth resistor  199  and ground  16  and is electrically connected in parallel with the second coil  127  for the tri-coil transformer  126 .  
         [0037]     There is a lamp power output  144  that provides a current that represents the fluorescent lamp power into an external capacitor and resistor network  146 . An illustrative, but nonlimiting example of an external capacitor and resistor network  146  includes a twenty-third capacitor  344 , e.g., 0.022 μF, that is electrically connected in parallel with a thirty-sixth resistor  338 , e.g., 12,000 Ω. The combination of twenty-third capacitor  344  and the thirty-sixth resistor  338  is electrically connected in parallel with a thirty-seventh resistor  340 , e.g., 5,600 Ω. The combination of the twenty-third capacitor  344 , the thirty-sixth resistor  338  and the thirty-seventh resistor  340  is electrically connected in parallel with a thirty-eighth resistor  342 , e.g., 750 Ω, and a twenty-fourth capacitor  346 , e.g., 0.68 μF. The thirty-eighth resistor  342  and the twenty-fourth capacitor  346  are electrically connected to each other in series. One end of the thirty-seventh resistor  340 , the twenty-third capacitor  344 , the twenty-fourth capacitor  346  and the thirty-eighth resistor  342  is connected to ground  16  while the other end of the thirty-seventh resistor  340  is electrically connected to a second differential input for sensing lamp current  148  for the drive and control circuit  100 .  
         [0038]     There is a first lamp driver output  150  for the drive and control circuit  100  that provides voltage via a first primary terminal  363  to a first lamp driver transformer  152 , e.g., 50 T/50 T, 3.14 mH. The second primary terminal  364  of the first lamp driver transformer  152  is electrically connected in series to a ninth capacitor  154 , e.g., 0.47 μF, and then to ground  16 .  
         [0039]     There is a ninth resistor  156 , e.g., 22 Ω, connected in series between a first secondary terminal  348  for the first lamp driver transformer  152  and a gate  160  for a first lamp driver, metal-oxide-semiconductor, field effect transistor  158 , e.g., IRF 830A. The drain  162  for the first lamp driver, metal-oxide-semiconductor, field effect transistor  158  is electrically connected via a first rectifier  164 , e.g., HER  206 , to the inductive dual coil transformer  74 .  
         [0040]     Voltage from the second secondary terminal  349  for the a first lamp driver transformer  152  and voltage from the source  166  of the a first lamp driver, metal-oxide-semiconductor field effect transistor  158  are provided to a lamp driver power transformer  168  via a pair of dual inductors  170 , e.g., 5 mH, which are electrically connected in parallel. There is a twenty-fifth capacitor  366 , e.g., 1.00 μF, that is electrically connected between the second secondary terminal  349  for the a first lamp driver transformer  152  and the two opposing rectifiers  252  and  254 .  
         [0041]     There is a first secondary terminal  172  for the lamp driver power transformer  168  that is electrically connected in series to a fourth pair of series connected resistors  174 , e.g., 56,000 Ω each. There is a tenth capacitor  176 , e.g., 0.1 μF, which is electrically connected in parallel with the fourth pair of series connected resistors  174 . The fourth pair of series connected resistors  174  and the tenth capacitor  176  are then electrically connected directly to a first terminal  136  for the second fluorescent lamp  134  via a third electrical conductor  135 . The third electrical conductor  135  is in parallel with a third inductor and capacitor series combination  178 , e.g., 2.5 mH and 0.47 μF.  
         [0042]     There is a second secondary terminal  173  for the lamp driver power transformer  168  that is electrically connected in series to a fifth pair of series connected resistors  180 , e.g., 56,000 Ω and an eleventh capacitor  182 , e.g. 0.1 μF. The fifth pair of series connected resistors  180  and the eleventh capacitor  182  are electrically connected in parallel to each other. The fifth pair of series connected resistors  180  and the eleventh capacitor  182  are electrically connected directly to a second terminal  132  for the first fluorescent lamp  128  via a fourth electrical conductor  137 . The fourth electrical conductor  137  is in parallel with a fourth inductor and capacitor series combination  184 , e.g., 2.5 mH and 0.47 μF.  
         [0043]     There is a second lamp driver output  186  for the drive and control circuit  100  that provides voltage to a gate  188  for a second lamp driver, metal-oxide-semiconductor, field effect transistor  190 , e.g., IRF  830 , via a tenth resistor  192 , e.g., 22 Ω that is electrically connected in series. The drain  194  for the second lamp driver, metal-oxide-semiconductor field effect transistor  190  is electrically connected to the source  166  for the first lamp driver, metal-oxide-semiconductor field effect transistor  158 . The source  196  for the second lamp driver, metal-oxide-semiconductor field effect transistor  190  is electrically connected to ground  16 .  
         [0044]     There is a voltage load input  198  for the drive and control circuit  100  that has the dual purpose of detecting an overvoltage condition for the first and the second fluorescent lamps  128  and  134 , respectively, during ignition, removal or failure as well sensing the voltage for the first and the second fluorescent lamps  128  and  134 , respectively, during normal use.  
         [0045]     Voltage from the second terminal  132  of the first fluorescent lamp  128  is electrically connected in series to an eleventh resistor  202 , e.g., 120,000 Ω and the first terminal  136  of the second fluorescent lamp  134  is electrically connected in series to a twelfth resistor  204 , e.g., 120,000 Ω. The eleventh resistor  202  and the twelfth resistor  204  are electrically connected in parallel to each other and electrically connected in series to a thirteenth resistor  206 , e.g., 200,000 Ω, which in turn is electrically connected in series to a fourteenth resistor  208 , 12,000 Ω. The fourteen resistor  208  is electrically connected to ground  16 . The voltage across the fourteenth resistor  208  is applied to a second rectifier  218 , e.g., RGP10J, that is electrically connected in parallel to a fourteenth capacitor  220 , e.g., 0.22 μF. The current then passes in series through a fifteenth resistor  214 , e.g., 150,000 Ω, into the voltage load input  198  for the drive and control circuit  100 . The voltage load input  198  is also connected to ground  16  via a fifteenth capacitor  222 , e.g., 0.015 μF.  
         [0046]     When the voltage load input  198  for the drive and control circuit  100  receives an input current that exceeds a predetermined value, a stop timer is activated. If at the end of the timing period, if the predetermined input current is exceeded, the drive and control circuit  100  is switched into a standby state with the first lamp driver output  150  turned off and the second lamp driver output  186  turned on. The drive and control circuit  100  remains in the standby state when the input current to the voltage load input  198  drops below a predetermined valve. If the input current exceeds a predetermined value, then the drive and control circuit  100  is switched into a standby state immediately. The current into voltage load input  198  is a filtered DC signal with a maximum value that corresponds to the maximum voltage for the first fluorescent lamp  128  and the second fluorescent lamp  134  in a dimming state.  
         [0047]     There is a ground function  230  and a end-of-life input  232  (which is a function that is not utilized) for the drive and control circuit  100  that are both electrically connected to ground  16 . There is a external resistor input  234  for the drive and control circuit  100  that is electrically connected to an eighteenth resistor  236 , e.g., 30,000 Ω, which is then electrically connected to ground  16 .  
         [0048]     There is a sixth pair of series connected resistors  240 , e.g., 430,000 Ω and 430,000 Ω, that is electrically connected between the first rectifier  164  and the sixth capacitor  80 . The sixth capacitor  80  is also electrically connected to a nineteenth resistor  242 , e.g., 430,000 Ω, which is electrically connected to ground  16 .  
         [0049]     Also, there is a twentieth resistor  244 , e.g., 510,000 Ω, and a seventeenth capacitor  246 , e.g., 47 μF, that are electrically connected in parallel at one end to the first rectifier  164  and at the other end are electrically connected to a twenty-first resistor  248 , e.g., 510,000 Ω, and an eighteenth capacitor  250 , e.g., 47 μF. The twenty-first resistor  248  and the eighteenth capacitor  250  are both electrically connected in parallel and to ground  16 .  
         [0050]     Dimming control is provided by applying voltage to the dimming input  256  for the drive and control circuit  100 . A voltage above a predetermined upper level, e.g., four (4) volts, will be clamped down and maintained at that predetermined level for full brightness and above a predetermined lower level will also be kept at that lower predetermined level for full dim status while the altering of the voltage between the predetermined lower level and the predetermined upper level is directly proportionate to a desired amount of dimming.  
         [0051]     The dimming input  256  for the drive and control circuit  100  is electrically connected to a twenty-second resistor  258 , e.g., 100,000 Ω, and a nineteenth capacitor  260 , e.g., 0.22 μF. The nineteenth capacitor  260  is electrically connected to ground  16 . The twenty-second resistor  258  is electrically connected to a twenty-third resistor  262 , e.g., 62,000 Ω. The twenty-third resistor  262  is electrically connected to ground  16 . Moreover, the twenty-second resistor  258  is electrically connected to a twentieth capacitor  266 , e.g., 0.22 μF. The twentieth capacitor  266  is electrically connected to a twenty-sixth resistor  268 , e.g., 62,000 Ω. This twenty-sixth resistor  268  is electrically connected to ground  16 . Moreover, this twenty-sixth resistor  268  is electrically connected in series to a twenty-seventh resistor  272 , e.g., 330,000 Ω. The twenty-seventh resistor  272  is electrically connected in series to a twenty-eighth resistor  274 , e.g., 330,000 Ω. The twenty-eighth resistor  274  is electrically connected to the first rectifier  164  and the drain  162  for the first lamp driver, metal-oxide-semiconductor, field effect transistor  158 .  
         [0052]     Dimming voltage is provided to dimming input  256  for the drive and control circuit  100  via the twenty-fifth resistor  268 , the twentieth capacitor  266 , the twenty-third resistor  262  and the twenty-second resistor  258  and the nineteenth capacitor  260  via a dimming voltage transformer  276 , e.g., 10.5 mH and 30 T/30 T. The voltage from the dimming voltage transformer  276  passes through a second small signal diode  278 , e.g., 1N4448. The second small signal diode  278  is electrically connected to the twentieth capacitor  266 , the twenty-third resistor  262  and the twenty-second resistor  258 . Furthermore, the second small signal diode  278  is electrically connected to a twenty-ninth resistor  280 , e.g., 120,000 Ω and a twenty-first capacitor  282 , e.g., 0.1 μF. The twenty-ninth resistor  280  and the twenty-first capacitor  282  are both electrically connected to ground  16 .  
         [0053]     Also, electrically connected to the first secondary output terminal  277  for the dimming voltage transformer  276  is the voltage from the drain  92  of a n-channel, metal oxide semiconductor, field effect transistor  88  that passes through a twenty-second capacitor  284 , e.g., 1,000 pF, which is electrically connected in series with a thirtieth resistor  286 , e.g., 120,000 Ω. The thirtieth resistor  286  is directly and electrically connected to the first secondary output terminal  277  for the dimming voltage transformer  276 . The second secondary output terminal  279  for the dimming voltage transformer  276  is electrically connected to ground  16 .  
         [0054]     There is a light sensor  288  that provides voltage to the first primary input terminal  290  for the dimming voltage transformer  276  and to a second primary input terminal  292  for the dimming voltage transformer  276  via a third small signal diode  294 , e.g., 1N4148. Current can be diverted to a series of switches  296 . The preferred illustrative, but nonlimiting, example of a series of switches  296  includes three (3) dual-in-line package switches. A dual-in-line package switch or DIP switch is a group of subminiature switches mounted in a package compatible with standard integrated-circuit sockets and usually include rocker or slide-type switches. The slide type switches are preferred.  
         [0055]     An illustrative, but nonlimiting, example of a light sensor  288  can be obtained from Shanghai Fudan Microelectronics Co., Ltd. having a place of business at Floor 7th, Building C, No. 668 Eastern Beijing Road, Shanghai, People&#39;s Republic of China. There are also numerous other devices that can be utilized to provide a voltage that is proportional to the ambient light. This includes, but is not limited to, a photocell, a photoresistor, a photodiode, a phototransistor, a bipolar phototransistor, a photosensitive field-effect transistor and a light activated silicon-controlled rectifier.  
         [0056]     The series of switches  296  includes a first switch  302  that is electrically connected in series to a thirty-first resistor  304 , e.g., 8,200 Ω. The first switch  302  is electrically connected to the first primary input terminal  290  for the dimming voltage transformer  276  and the thirty-first resistor  304  is electrically connected to the second primary input terminal  292 , via the a third small signal diode  294 , for the dimming voltage transformer  276  to divert current from the primary of the dimming voltage transformer  276 .  
         [0057]     The series of switches  296  also includes a second switch  306  that is electrically connected in series to a thirty-second resistor  308 , e.g., 6,200 Ω. The second switch  306  is electrically connected to the first primary input terminal  290  for the dimming voltage transformer  276  and the thirty-second resistor  308  is electrically connected to the second primary input terminal  292 , via the a third small signal diode  294 , for the dimming voltage transformer  276  to divert current from the primary of the dimming voltage transformer  276 .  
         [0058]     Moreover, the series of switches  296  also includes a third switch  310  that is electrically connected in series to a thirty-third resistor  312 , e.g., 4,700 Ω. The third switch  310  is electrically connected to the first primary input terminal  290  for the dimming voltage transformer  276  and the thirty-third resistor  312  is electrically connected to the second primary input terminal  292 , via the a third small signal diode  294 , for the dimming voltage transformer  276  to divert current from the primary of the dimming voltage transformer  276 . However, numerous switches can be utilized for the series of switches  296  and the number of switches does not need to be limited to three (3).  
         [0059]     Referring now to  FIG. 2  and the series of switches  296 , when the first switch  302  is turned off, the second switch  306  is turned off and the third switch  310  is turned off, then all current will flow into the dimming voltage transformer  276  for one hundred percent (100%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0060]     Referring now to  FIG. 2A  and the series of switches  296 , when the first switch  302  is turned on, the second switch  306  is turned off and the third switch  310  is turned off, then some current will flow through the first switch  302  and the thirty-first resistor  304  rather than the dimming voltage transformer  276  for ninety percent (90%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0061]     Referring now to  FIG. 2B  and the series of switches  296 , when the first switch  302  is turned off, the second switch  306  is turned on and the third switch  310  is turned off then some current will flow through the second switch  306  and the thirty-second resistor  308  rather than the dimming voltage transformer  276  for eighty percent (80%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0062]     Referring now to  FIG. 2C  and the series of switches  296 , when the first switch  302  is turned off, the second switch  306  is turned off and the third switch  310  is turned on then some current will flow through the third switch  310  and the thirty-third resistor  312  rather than the dimming voltage transformer  276  for seventy percent (70%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0063]     Referring now to  FIG. 2D  and the series of switches  296 , when the first switch  302  is turned on, the second switch  306  is turned on and the third switch  310  is turned off then some current will flow through the first switch  302  and the thirty-first resistor  304  as well as the second switch  306  and the thirty-second resistor  308  rather than the dimming voltage transformer  276  for sixty percent (60%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0064]     Referring now to  FIG. 2E  and the series of switches  296 , when the first switch  302  is turned off, the second switch  306  is turned on and the third switch  310  is turned on then some current will flow through the second switch  306  and the thirty-second resistor  308  as well as the third switch  310  and the thirty-third resistor  312  rather than the dimming voltage transformer  276  for fifty percent (50%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0065]     Referring now to  FIG. 2F  and the series of switches  296 , when the first switch  302  is turned on, the second switch  306  is turned on and the third switch  310  is turned on then some current will flow through the first switch  302  and the thirty-first resistor  304 , the second switch  306  and the thirty-second resistor  308  as well as the third switch  310  and the thirty-third resistor  312  rather than the dimming voltage transformer  276  for forty percent (40%) of full light output from the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively.  
         [0066]     The series of switches  296  are preferably DIP switches located within a molded housing, e.g., plastic, as shown in  FIG. 3 . Preferably, the molded housing  357  is of a “teardrop” shape. The series of switches  296 , e.g., DIP switches, are preferably electrically attached to a small circuit board (not shown). The interior of the top section of the molded housing  357  preferably allows the series of switches  296  to snap in place for quick assembly with tabs (not shown) to guide a first electrical connector  314 . The top section of the molded housing  357  has an opening  359  for providing access to the series of switches  296 . The series of switches  296  provides manual ballast factor adjustment that is used to “tune” the output from the first fluorescent lamp  128  and the second fluorescent lamp  134 .  
         [0067]     Although the preferred range of predetermined light levels is from forty percent (40%) of full light output to about one hundred percent (100%) of full light output. However, the lower range can extend down to ten percent (10%) or less.  
         [0068]     An advantage to the present invention is that each ballast circuit  10  can be individually controlled rather than having to collectively control the light level in the entire room. This means that the fluorescent lighting fixtures close to windows dim the same as the fluorescent fixtures in the back of a room. This will create uneven lighting. The present invention addresses this problem by dimming each fluorescent lighting fixture individually. Further, since each individual fluorescent lighting fixture can be pre-set, one or two fixtures in a room can be individually dimmed to a desired predetermined level, which is something that cannot be accomplished with whole-room controllers.  
         [0069]     Referring again to  FIG. 3 , the overall wiring diagram for a fluorescent lighting fixture is generally indicated by numeral  2 . This includes the previously described ballast circuit  10  with an electrical power conduits  361  that connect to of input voltage terminals  12  and  14 , as shown in  FIG. 1 , that can receive alternating current. As shown in  FIG. 3 , there are electrical connectors  362  and  364  that electrically connect to the first fluorescent lamp  128  and the second fluorescent lamp  134 , respectively, as shown in  FIG. 1 . There is also the first electrical connector  314  to the series of switches  296 , e.g., DIP switch and a second electrical connector  316  to the light sensor  288 , as shown in  FIG. 3 . A fluorescent light fixture is generally indicated by numeral  370 . The first edge for a fluorescent light fixture is indicated by numeral  318  and a second edge for a fluorescent light fixture is indicated by numeral  320 . The first edge for an internal cover for a fluorescent light fixture is indicated by numeral  322  and a second edge for an internal cover for a fluorescent light fixture is indicated by numeral  324 .  
         [0070]     Referring now to  FIG. 4 , the light sensor  288 , e.g., photocell, can be mounted to a recessed fluorescent light fixture  370 , shown in  FIG. 3 , with the light sensor housing  326  extending through an acoustic tile  328 . This is a flange nut  334  sealing the front of the light sensor housing  326  against the acoustic tile  328  with a washer  330  secured against the back of the acoustic tile  328  with a spring clip  332 . This is to hold the light sensor housing  326  in a fixed position extending from the acoustic tile  328 .  
         [0071]     Referring now to  FIG. 5 , the light sensor  288 , e.g., photocell, can be mounted to a fluorescent light surface with the light sensor housing  326  extending through a fixture housing  336  for the fluorescent light fixture  370 , shown in  FIG. 3 . There is a flange nut  334  sealing the front of the light sensor housing  326  against the fixture housing  336  with a washer  330  secured against the back of the fixture housing  336  with a spring clip  332 . This is to hold the light sensor housing  326  in a fixed position extending from the fixture housing  336 .  
         [0072]     As shown in  FIG. 3 , the preferred, but nonlimiting, light sensor  288 , e.g., photocell, includes a molded construction, e.g., molded plastic, with a removable dome lens  352 , which is secured to a body  354 . Preferably the light sensor  288  is secured within the dome lens  352  and the body  354  with a waterproof sealant, e.g., silicone (not shown). The shape of the dome lens  352  is designed for optimum spatial distribution for a cosine-corrected distribution of light to the light sensor  288 . This is to maximize sensing accuracy of room light levels. The light sensor  288  responds to artificial and natural light sources with continuously responsive dimming.  
         [0073]     The light sensor  288  measures light contribution available from natural sunlight entering the room and signals the ballast circuit  10  to dim to reduce artificial light output. Light levels are maintained by balancing natural light contribution with artificial light output. This technology is defined as “daylight harvesting,” which is a helpful feature in reducing energy expenses associated with fluorescent lighting.  
         [0074]     Although the preferred embodiment of the present invention and the method of using the same has been described in the foregoing specification with considerable details, it is to be understood that modifications may be made to the invention which do not exceed the scope of the appended claims and modified forms of the present invention incorporated by others skilled in the art to which the invention pertains will be considered infringements of this invention when those modified forms fall within the claimed scope of this invention.