Abstract:
A control device and signaling are provided to operate selected numbers of the ballasts in a multi-ballast, multi-lamp luminaire. The luminaire has a control input for receiving a control signal from a wall switch, for example. The number of ballasts operated by the luminaire increases or decreases sequentially in response to one of consecutive pulses, signal level transitions or interrupts in the control signal. The control device can be programmable or hard-wired to the relays (e.g., a counter and decoder) to allow for a more economical implementation. Different subsets of the ballasts can be selected via the programmable integrated circuit to distribute the burn times of the lamps.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to a control device for essentially any illumination device or system comprising multiple ballasts and multiple lamps. More particularly, the present invention relates to a dimming apparatus for gas discharge or incandescent luminaires having multiple ballasts and lamps therein that enables selected ones of the ballasts and their associated lamps to control the illumination level of a specific area  
         BACKGROUND OF THE INVENTION  
         [0002]    Different tasks require various levels of illumination. For example, an office worker may desire brighter illumination over his desk than a computer operator would want over his computer console.  
           [0003]    Dimming devices have been proposed to adjust the lumen level of light sources. For example, a wireless lighting control system can employ a radio frequency (RF) transmitter and receiver to adjust the illumination level of a light source(s) for a particular area. However, this type of RF control system has drawbacks. Specifically, the luminaires may not always receive the RF signaling from the transmitter, and so the lumen level may not be adjusted as desired. Accordingly, factors such as signal strength (e.g., the proximity of the transmitter to the receiver) becomes an issue for adjusting the illumination level. This can be a significant problem in a facility where the luminaires are suspended from the ceiling (e.g., on the order of thirty feet or more above the ground) and are difficult to reach to maintenance purposes. Many RF control systems employ sequential circuit operation and control signaling to benefit from the simplicity of only having to use one specific RF signal for the control command. Assuming a sequential control circuit is used, if one luminaire is unable to receive signals re-transmitted from the transmitter of another luminaire, and therefore does not extinguish or enable its lamps to adjust the lumen level as desired, that luminaire can become out of sequence with the other luminaires in the facility, causing improper lighting. To correct such a problem, all of the luminaires would have to be cycled off and then on, and the RF receiver(s) and transmitter(s) repositioned in order to obtain better reception within the RF control system of the luminaires. Accordingly, a need exists for a lighting control system that is hard-wired with respect to the luminaires and provides accurate and consistent lumen level adjustment within the operating area.  
           [0004]    In addition, existing lighting control systems are disadvantageous because they generally employ sequencing through predetermined steps to power up and power down selected ones of a plurality of lamps. Some lamps are therefore subjected to shorter burn times than other lamps. For example, in a luminaire having eight lamps that are controlled by four two-lamp ballasts, the typical cycle is operate none of the lamps, two of the lamps, four of the lamps, six of the lamps, or all eight of the lamps, depending on how may signals are sent by the radio transmitter. When only two lamps are desired, the same two lamps are typically powered on, while the remaining lamps are powered down. Similarly, when only four or six of the lamps are desired, the same subsets of lamps are selected, while the remaining lamps are subjected to less burn time. Using fixtures wherein some lamps age more rapidly than others presents maintenance problems. A need therefore exists for a lighting control system that rotates use of each of the lamps in a multiple-ballast and multiple-lamp luminaire to more evenly distribute their burn times.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with the present invention, a lighting control system is provided to selectively operate ballasts in a multi-ballast, multi-lamp luminaire via relays to control the lumen output level of the luminaire.  
           [0006]    In accordance with an aspect of the present invention, the lighting control system employs a sequential control device and signaling to operate selected numbers of the ballasts in a multi-ballast, multi-lamp luminaire.  
           [0007]    In accordance with another aspect of the present invention, the luminaire is provided with a control input for receiving a control signal. The control signal can be generated via a wall-mounted switch or other device operable to generate an output signal. The number of ballasts operated by the luminaire increases or decreases sequentially in response to one of consecutive pulses, signal level transitions or interrupts in the control signal.  
           [0008]    In accordance with another aspect of the present invention, the control device is hard-wired to the relays (e.g., a counter and decoder combination) to obviate the need for a programmable integrated circuit and allow for a more economical implementation.  
           [0009]    In accordance with yet another aspect of the present invention, the control device is a programmable integrated circuit that provides for operation of selected numbers of the ballasts in response to a control signal. Different subsets of the ballasts can be selected to distribute the burn times of the lamps.  
           [0010]    In accordance with still yet another aspect of the present invention, the lighting control system can arrange addressable luminaires in different zones and addresses for selected luminaires can be transmitted via the control signal. The programmable integrated circuit can also track actual burn times of luminaires and use this information to select which ballasts to operate.  
           [0011]    In accordance with an embodiment of the present invention, a luminaire having a plurality of ballasts connected to a plurality of lamps is provided which further comprises: (1) a plurality of relays connected to respective ones of the plurality of ballasts; (2) a control device connected to each of the plurality of relays; and (3) a control input for providing a control signal to the control device. The control device comprises a counter for counting and generating an output signal in response to the control signal, and a decoder configured to receive the output signal and sequentially select which of the plurality of relays to actuate, thereby operating the corresponding ones of the plurality of ballasts in response to the output signal. The control signal is a DC signal comprising pulses. The counter is operable to increment the output signal in response to each pulse. The decoder is configured to implement a truth table whereby all of the plurality of ballasts are powered on in response to a first one of the pulses, and then one or more subsets of the plurality of ballasts are powered down in response to subsequent ones of the pulses until all of the plurality of ballasts are powered down.  
           [0012]    In accordance with another embodiment of the present invention, the decoder is configured to implement a truth table whereby all of the plurality of ballasts are powered down in response to a first one of the pulses, and then one or more subsets of the plurality of ballasts are powered on in response to subsequent ones of the pulses until all of the plurality of ballasts are powered on.  
           [0013]    In accordance with another embodiment of the present invention, a luminaire having a plurality of ballasts connected to a plurality of lamps is provided and further comprises: (1) a plurality of relays connected to respective ones of the plurality of ballasts; (2) a control device connected to each of the plurality of relays; and (3) a control input for providing a control signal to the control device. The control device comprises a programmable controller that is programmed to sequentially select which of the plurality of relays to actuate and thereby operate the corresponding ones of the plurality of ballasts in response to the control signal. The programmable controller is operable to select which of the plurality of ballasts to operate to distribute the burn times of the plurality of lamps. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    These and other aspects, advantages and novel features of the invention will be more readily appreciated from the following detailed description when read in conjunction with the accompanying drawings, in which:  
         [0015]    [0015]FIG. 1 is a block diagram of a lighting control system constructed in accordance with an embodiment of the present invention;  
         [0016]    [0016]FIG. 2 is a block diagram of a ballast control device constructed in accordance with an embodiment of the present invention;  
         [0017]    [0017]FIG. 3 is a truth table employed by a ballast control device in accordance with an embodiment of the present invention;  
         [0018]    [0018]FIG. 4 is a schematic diagram of a ballast control device constructed to implement the truth table of FIG. 3 in accordance with an embodiment of the present invention;  
         [0019]    [0019]FIG. 5 is a truth table employed by a ballast control device in accordance with an embodiment of the present invention;  
         [0020]    [0020]FIG. 6 is a schematic diagram of a ballast control device constructed to implement the truth table of FIG. 5 in accordance with an embodiment of the present invention; and  
         [0021]    [0021]FIG. 7 is a block diagram of a ballast control device constructed in accordance with an embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]    [0022]FIG. 1 is a block diagram of a lighting control system  10  constructed in accordance with an embodiment of the present invention. The lighting control system  10  comprises a control device  12  for selectively operating a plurality of relays indicated generally at  14 . By way of an example, four relays  14   a ,  14   b ,  14   c  and  14   d  are connected to respective ballasts  16   a ,  16   b ,  16   c  and  16   d . The relays  14   a ,  14   b ,  14   c  and  14   d  are controllably actuated to selectively power up and power down respective ballasts  16   a ,  16   b ,  16   c  and  16   d  and, correspondingly, lamps connected to the ballasts. The lamps are indicated generally at  18  and can be incandescent lamps or gas discharge lamps such as fluorescent, metal halide or high pressure sodium lamps. The lamps  18  and ballasts  16  are preferably provided in a multiple-ballast and multiple-lamp luminaire  20 ; however, the ballasts can also be shared between two or more multiple-lamp luminaires. The lighting control system  10  can be used with any high intensity discharge or fluorescent lamp luminaire that uses multiple lamps and more than one ballast.  
         [0023]    With continued reference to FIG. 1, each luminaire  20  is provided with AC power, as indicated by the line (L), neutral (N) and ground (G) lines in this embodiment. It is to be understood, however, that the power supply can employ line (L 1 ), line (L 2 ) and ground (G). Each luminaire  20  is preferably also provided with a control input  24  which can be, for example, a single wire or a pair of wires. As will be described in more detail below, the control input transports a control signal (e.g., a DC signal) that indicates the desired illumination level to the control device  12  which, in turn, responds by actuating the relay(s)  14  corresponding to selected ballasts  16 .  
         [0024]    The control input  24  is connected to a user control interface  26  which can be, for example, a conventional wall-mounted light switch such as a toggle (ON/OFF) switch, a slide switch, or a dial. The user control interface can also be a clock or other device that generates an output signal. In the illustrated embodiment, the control signal generated by the user control interface  26  is a DC signal that is high or low, depending on the state of the user control interface. For example, the control signal can be high each time a toggle switch is placed in the ON position and low each time the toggle switch is placed in the OFF position. The control device  12  then interprets each change in the state of the control signal on the control input  24  as a request to power on or power down one or more of the ballast(s)  16 .  
         [0025]    As shown in FIG. 1, the relays  14  can be employed to switch power to the ballasts  16  to selectively power up and power down the ballasts. Alternatively, the ballasts  16  can be electronic-type ballasts, and the relays  14  can be employed to switch low voltage control signals to the ballasts  16  to selectively power up and power down their respective lamps  18 .  
         [0026]    As shown in FIG. 1, the luminaires  12  can be cascaded. In other words, the same control input  24  can be provided to more than one luminaire  12 . In addition, a control input  24  can be provided with more than one user control interface  26  such that activation of any of the user control interfaces  26  serves as an indication to power down or power up one or more of the ballasts in each of the luminaires  20  connected to that control input  24 . As described in more detail below, the control device  12  can be programmable such that each luminaire  20  is addressable within a group of luminaires via the control input  24 . Each luminaire can also be controlled as part of plural and addressable groups of luminaires. For example, luminaires can be arranged in zones and one luminaire can be a member of more than one zone of luminaires.  
         [0027]    For illustrative purposes, an exemplary luminaire  20  is described herein which has four ballasts  16  that each provide power to two lamps  18 . The luminaire  20  can therefore operate in one of five states, that is, all eight lamps are on, six lamps are on, four lamps are on, two lamps are on or none of the lamps are on. Rather than hardwiring four independent circuits into the luminaire  20 , the luminaire is provided with a single control device  12  and relays  14  to control which ballasts  16  are powered on via control logic.  
         [0028]    In accordance with one embodiment of the present invention, the control device  12  is implemented using a counter  30  and a decoder  32  to determine which of the ballasts  16  in a multi-ballast and multi-lamp luminaire  20  are to operate via a corresponding one of the relays  14 , as shown in FIG. 2. In the illustrated embodiment, the control signal has voltage pulses corresponding to the number of times a user toggled a wall switch  26 , for example. The control signal is provided to the counter  30 , which generates an output that can be decoded by the decoder  32 . A hexadecimal output from the counter  30  can be used, for example. The following table relates the hexidecimal output of the counter  30  to the states of the ballasts  16  and their corresponding lamps  18  in a sequential manner. “A” is the least significant bit. For example, if all of the lights are off and a user control interface  26  such as a toggle-type wall switch is switched ON and then OFF once, two lamps  18  are illuminated. A user can then toggle the switch one, two, and three more times to have four, six and then eight lamps powered on. Another operation of the toggle switch serves to power all of the lamps  18  down again.  
                                                                   Number of Ballasts   Number of Lamps       A   B   C   D   Powered   Operating                   0   0   0   0   0   0       1   0   0   0   1   2       0   1   0   0   2   4       1   1   0   0   3   6       0   0   1   0   4   8       1   0   1   0   0 (counter reset)   0 (counter reset)                  
 
         [0029]    A truth table for the required logic is shown in FIG. 3. Only counter outputs A, B and C are used since only four ballasts are being controlled in the illustrated example. A “0” in the truth table corresponds to an open relay and therefore to no power being provided to the lamps from the ballast. A “1” in the truth table corresponds to a closed relay and therefore to power being provided to the lamps from the ballast. As can be understood from FIG. 3, if Relay #4 is closed, then all of the other relays are closed. Further, if Relay #3 is closed, then Relay #2 and Relay #1 are also closed, but not Relay #4. This pattern of relay operation is the basis for the exemplary logic illustrated in FIG. 4.  
         [0030]    The sequence of switching can also be reversed in accordance with another embodiment of the present invention. The following table relates the hexidecimal output of the counter  30  to the states of the ballasts  16  and their corresponding lamps  18  in a sequential manner. “A” is the least significant bit.  
                                                                   Number of Ballasts   Number of Lamps       A   B   C   D   Powered   Operating                   0   0   0   0   0   0       1   0   0   0   4   8       0   1   0   0   3   6       1   1   0   0   2   4       0   0   1   0   1   2       1   0   1   0   0 (counter reset)   0 (counter reset)                  
 
         [0031]    A truth table for the required logic is shown in FIG. 5. As can be understood from FIG. 5, of Relay #1 is closed, then all of the other relays are closed. Further, if Relay #2 is closed, then Relay #3 and Relay #4 are also closed, but not Relay #1. This pattern of relay operation is the basis for the logic illustrated in FIG. 6 The decoder and counter combination depicted in FIGS. 4 and 6 can be implemented as a gate array burned into field programmable gate array (FPGA) or similar device. In any case, the logic for selecting which relay(s)  14  and corresponding ballast(s)  16  to operate in response to a change in a control signal (e.g., a pulse or interrupt in the control signal) that is exemplified in FIGS. 4 and 6 can be manufactured less expensively than employing the use of a programmable integrated circuit such as a microcontroller or microprocessor.  
         [0032]    The counter  30  and decoder  32  ate economical for lighting control applications that use fixed control of the ballasts  16  and their corresponding lamps  18 , that is, applications that select the same ballasts in the same order within each cycle of the control signals (e.g., in response to consecutive control signal pulses, power all ballasts on, then open the relay to ballast #3, then open the relay to ballast #2 and so on until all ballasts are off, then power all ballasts on again). The lighting control system  10 , however, can also provide more complex ballast control operations. For example, in the control devices  12  illustrated in FIGS. 4 and 6, some lamps age more rapidly than others (e.g., the first pair of lamps) and would therefore have to be replaced more frequently unless all of the lamps  18  are powered on whenever the luminaire  20  is used. In accordance with another embodiment of the present invention, the control device  12  is implemented using a programmable device  34  (e.g., a microprocessor or microcontroller) to determine which of the ballasts  16  in a multi-ballast and multi-lamp luminaire  20  to operate to illuminate the lamps connected thereto. The programmable device  34  can be programmed, for example, to alternate which of the lamps  18  are the primary pair of lamps that is operated when operation of only two of the lamps is desired. Further, the programmable device  34  can be programmed to alternate which of the lamps  18  are the secondary and third pairs of lamps that ate operated when operation of four and six of the lamps, respectively, is desired.  
         [0033]    As shown in FIG. 7, the control device  12  can comprise a microcontroller which can provide separate control outputs to respective ones of the relays  14 . As shown in the following table, the microcontroller can be programmed to operate a subset of three ballasts  16  and their corresponding lamps  18  on a particular day, or only one ballast and its lamps on a different day. Further, the microcontroller can be programmed to alternate which ballasts constitute the multiple ballast subset and which of the ballasts is to operate alone, as illustrated for Days  3  and  4  in the table below. As stated previously, the illustrated embodiment is described in connection with an exemplary luminaire comprising four ballasts and two lamps for each ballast. It is also to be understood that the present invention can be employed with different numbers of lamps, ballasts and luminaires, as well as different configurations such as the sharing of ballasts between lamps of different luminaires.  
                                   Initialization of Luminaire Operation   Ballast(s) Operating                   Day 1   #1, #2, #3       Day 2   #1       Day 3   #2, #3, #4       Day 4   #4                  
 
         [0034]    In accordance with the present invention, the control device  12  receives or generates control signals to operate selected relays  14  and, correspondingly, their respective ballasts  16  and lamps  18  in preferably a manner that rotates lamp usage to more evenly distribute lamp burn times. For example, the control device  12  can receive control signals from a user control interface  26  such as a wall-mounted light switch. The microcontroller  34  can be programmed to interpret each pulse, or high-to-low or low-to-high transition, or interrupt in the control signal transported via the control input  24  as an instruction to change the states of the ballasts  16  in the luminaire  20 . The microcontroller  34 , in turn, generates an output signal on or more of its pins connected to respective relays  14 .  
         [0035]    It is also to be understood that the microcontroller  34  can be programmed to select which ballasts to operate in response to the control signal on the control input  24 , as well as on the basis of other factors such as date and/or time of day, or in which of a number of zones the luminaire  20  operates, or which lamps have undergone the most burn time, and so on. For example, the microcontroller  34  can be programmed to vary which ballasts  16  are operated in response to changes in the control signal regardless of the actual burn times of the lamps. In other words, the ballasts #1, #2 and #3 in the previous example, can be powered on for a period of eight hours on Day 1 and then be powered on for only two hours on Day 5 in the next cycle, depending on a user&#39;s need for lighting. The microcontroller  34  can also be programmed to track the selection of ballasts  16  and the actual burn times of the lamps  18  and use this stored information when selecting ballasts  16  for operation. In addition, the microcontroller can be programmed to perform sequential operation of the ballasts in a manner similar to the counter and decoder described above, that is, to operate the same ballasts in the same order within each cycle of the control signal (e.g., power down all four ballasts in response a pulse, power up ballast  16   a  in response to the next pulse, power up ballast  16   b  in response to the next pulse, and so on until all ballasts are powered down again).  
         [0036]    When the control device  12  is implemented using programmable logic as exemplified in FIG. 7, the luminaires in the lighting control system  10  can be addressable in accordance with another aspect of the present invention. For example, each microcontroller  34  in a plurality of luminaires  20  can be assigned an address. A master controller, or distributed control among the microcontrollers  34 , can then be used to send commands including one or more addresses to the luminaires  20  via their control inputs  24 . Each microcontroller, in turn, can examine a received command and respond with programmed control of corresponding relay(s)  14  if the command is addressed to it. Thus, the luminaires can be arranged in different zones within a facility.  
         [0037]    Although several exemplary embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications ate possible in the exemplary embodiments without departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims.