Patent Publication Number: US-7896674-B2

Title: Flexible connector assembly for a load control device

Description:
RELATED APPLICATIONS 
     This application is a divisional application of commonly-assigned, U.S. patent application Ser. No. 12/105,667, filed Apr. 18, 2008, entitled LOAD CONTROL DEVICE HAVING A FLEXIBLE CONNECTOR, which claims priority from U.S. Provisional Application No. 60/925,821, filed Apr. 23, 2007, entitled LOAD CONTROL DEVICE HAVING A MODULAR ASSEMBLY. The entire disclosures of both applications are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to load control devices for controlling the amount of power delivered to an electrical load from a power source. More specifically, the present invention relates to a wall-mountable dimmer having a flexible connector allowing for easy installation of a user interface module and alignment of the user interface module in an opening of a faceplate. 
     2. Description of the Related Art 
     A conventional two-wire dimmer has two terminals: a “hot” terminal for connection to an alternating-current (AC) power supply and a “dimmed hot” terminal for connection to a lighting load. Standard dimmers use one or more semiconductor switches, such as triacs or field effect transistors (FETs), to control the current delivered to the lighting load and thus to control the intensity of the light. The semiconductor switches are typically coupled between the hot and dimmed hot terminals of the dimmer. 
     Smart wall-mounted dimmers include a user interface typically having a plurality of buttons for receiving inputs from a user and a plurality of visual indicators for providing feedback to the user. These smart dimmers typically include a microcontroller or other processing device for providing an advanced set of control features and feedback options to the end user. An example of a smart dimmer is described in greater detail in commonly assigned U.S. Pat. No. 5,248,919, issued on Sep. 28, 1993, entitled LIGHTING CONTROL DEVICE, the entire disclosure of which is hereby incorporated by reference. 
       FIG. 1  is a front view of a user interface of a prior art smart dimmer switch  10  for controlling the amount of power delivered from a source of AC power to a lighting load. As shown, the dimmer switch  10  includes a faceplate  12 , a bezel  14 , an intensity selection actuator  16  for selecting a desired level of light intensity of a lighting load (not shown) controlled by the dimmer switch  10 , and a control switch actuator  18 . Actuation of the upper portion  16 A of the intensity selection actuator  16  increases or raises the light intensity of the lighting load, while actuation of the lower portion  16 B of the intensity selection actuator  16  decreases or lowers the light intensity. The intensity selection actuator  16  may control a rocker switch, two separate push switches, or the like. The control switch actuator  18  may control a push switch or any other suitable type of actuator and typically provides tactile and auditory feedback to a user when pressed. 
     The smart dimmer  10  also includes an intensity level indicator in the form of a plurality of visual indicators  20 , which are illuminated by a plurality of light sources such as light-emitting diodes (LEDs) located inside the dimmer  10 . The visual indicators  20  may be arranged in an array (such as a linear array as shown) representative of a range of light intensity levels of the lighting load being controlled. The intensity level of the lighting load may range from a minimum intensity level, which is preferably the lowest visible intensity, but which may be zero, or “full off,” to a maximum intensity level, which is typically “full on.” Light intensity level is typically expressed as a percentage of full intensity. Thus, when the lighting load is on, light intensity level may range from 1% to 100%. 
     However, in order to change the color of the dimmer  10 , specifically, the color of the bezel  14 , the intensity selection actuator  16 , and the control switch actuator  18 , the dimmer must be replaced with another dimmer, which has the desired color. Since the LEDs that illuminate the visual indicators  20  are located inside the dimmer  10 , the prior art dimmer is typically only offered having a single choice for the color of the visual indicators. The entire dimmer must be replaced to change the color of the LEDs. 
     Therefore there is a need for a load control device, which allows for easy adjustment of the color of the plastics of the user interface and the color of the visual indicators after the load control device is installed. 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, a flexible connector assembly comprises an enclosure adapted to house an electrical circuit, a main printed circuit board, a flexible cable, a connector printed circuit board, and a movable connector having a mating end adapted to be connected to a mating connector. The flexible cable has a first end and a second end opposite the first end. The first end of the flexible cable is electrically connected to the electrical circuit and is fixed in location with reference to the enclosure. The electrical circuit is mounted to the main printed circuit board, and the movable connector is connected to the connector printed circuit board, such that the movable connector is electrically and mechanically coupled to the second end of the flexible cable and is slidably captured by the enclosure. The enclosure has an opening defining a longitudinal axis and a lateral axis. The mating end of the flexible connector is provided in the opening of the enclosure and is adapted for movement along the longitudinal axis and the lateral axis to allow for alignment of the mating end of the flexible connector. 
     According to another embodiment of the present invention, a load control device for controlling the amount of power delivered to an electrical load from an AC power source comprises a load control printed circuit board, a flexible cable, a connector printed circuit board, and a connector. The flexible cable has a first end electrically and mechanically coupled to the printed circuit board, and a second end opposite the first end. The connector printed circuit board is electrically and mechanically coupled to the second end of the flexible cable. The connector is mounted on the connector printed circuit board, such that the connector is electrically coupled to a second end of the flexible cable, and thus to the printed circuit board. The connector is adapted to move along a longitudinal axis and a lateral axis of the load control device to allow for alignment of the connector. 
     According to yet another embodiment of the present invention, a load control device for controlling the amount of power delivered from an AC power source to an electrical load comprises a faceplate having an opening and a user interface module having an actuator adapted be provided in the opening of the faceplate in order to receive a user input. The load control device further comprises a load control printed circuit board, a flexible cable having a first end electrically and mechanically coupled to the printed circuit board, and a connector electrically and mechanically coupled to a second end of the flexible cable, such that the connector is electrically coupled to the printed circuit board. The user interface module is electrically and mechanically coupled to the connector. The connector is adapted to move along the longitudinal axis and the lateral axis of the load control device to align the actuator within the opening of the faceplate. 
     Other features and advantages of the present invention will become apparent from the following description of the invention that refers to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a user interface of a prior art dimmer; 
         FIG. 2  is a perspective view of a dimmer according to the present invention; 
         FIG. 3  is an exploded perspective view of the dimmer of  FIG. 2  showing a user interface module and a base module; 
         FIG. 4  is a rear perspective view of the user interface module of the dimmer of  FIG. 2 ; 
         FIG. 5A  is a front view of the dimmer of  FIG. 2  with the user interface module installed on the base module; 
         FIG. 5B  is a right side view of the dimmer of  FIG. 2  with the user interface module installed on the base module; 
         FIG. 5C  is a bottom cross-sectional view of the user interface module; 
         FIG. 6  is a right side cross-sectional view of the dimmer of  FIG. 2 ; 
         FIG. 7A  is a front perspective view of a user interface module printed circuit board of the user interface module of  FIG. 3 ; 
         FIG. 7B  is a rear perspective view of the user interface module printed circuit board of  FIG. 7A ; 
         FIG. 8  is another right side cross-sectional view of the dimmer of  FIG. 2 ; 
         FIG. 9  is a top cross-sectional view of the dimmer of  FIG. 2 ; 
         FIG. 10  is a front cross sectional view of the dimmer of  FIG. 2 ; 
         FIG. 11  is an exploded view of the assembly of a flexible base module connector of the base module of  FIG. 3 ; 
         FIG. 12  is a simplified block diagram of the electrical circuitry of the dimmer of  FIG. 2 ; 
         FIG. 13A  and  FIG. 13B  are simplified schematic diagrams of a stabilizing circuit and a usage detection circuit of the electrical circuitry of  FIG. 12 ; 
         FIG. 14  is a simplified schematic diagram of an audible sound generator of the electrical circuitry of  FIG. 12 ; 
         FIG. 15  is a flowchart of a actuation procedure executed by a controller of the dimmer of the electrical circuitry of  FIG. 12 ; 
         FIG. 16  is a flowchart of an Idle procedure of the actuation procedure of  FIG. 15 ; 
         FIGS. 17A and 17B  are flowcharts of an ActiveHold procedure of the actuation procedure of  FIG. 15 ; and 
         FIG. 18  is a flowchart of a Release procedure of the actuation procedure of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The foregoing summary, as well as the following detailed description of the preferred embodiments, is better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings an embodiment that is presently preferred, in which like numerals represent similar parts throughout the several views of the drawings, it being understood, however, that the invention is not limited to the specific methods and instrumentalities disclosed. 
       FIG. 2  is a perspective view of a dimmer  100  according to the present invention. The dimmer  100  includes a thin touch sensitive actuator  110  comprising an actuation member  112  having first and second portions  112 A,  112 B. The actuation member  112  extends through a bezel  114  to contact a touch sensitive device  150  ( FIG. 6 ) inside the dimmer  100  as will be described in greater detail below. The dimmer  100  is operable to control the intensity of a connected lighting load  208  ( FIG. 12 ) in response to actuations of the actuation member  112  and thus the touch sensitive device  150 . 
     The dimmer  100  further comprises a faceplate  116 , which has a non-standard opening  118  and mounts to an adapter  120 . The bezel  114  is housed behind the faceplate  116  and extends through the opening  118 . The adapter  120  connects to a yoke  122  ( FIG. 3 ), which is adapted to mount the dimmer  100  to a standard electrical wallbox via two mounting holes  124  ( FIG. 3 ). The dimmer  100  further comprises an enclosure  126 , which comprises a ring portion  128  and a back portion  129  ( FIG. 6 ). An air-gap actuator  190  allows for actuation of an internal air-gap switch  219  ( FIG. 12 ) by pulling the air-gap actuator down. 
     The bezel  114  comprises a break  125 , which separates the upper portion  112 A and the lower portion  112 B of the actuation member  112 . Upon actuation of the lower portion  112 B of the actuation member  112 , the dimmer  100  causes the connected lighting load  208  to toggle from on to off (and vice versa). Actuation of the upper portion  112 A of the actuation member  112 , i.e., above the break  125 , causes the intensity of the lighting load  208  to change to a level dependent upon the position of the actuation along the length of the actuation member  112 . 
     A plurality of visual indicators, e.g., a plurality of light-emitting diodes (LEDs)  152  ( FIG. 6 ), are arranged in a linear array adjacent a rear surface of the actuation member  112 . The actuation member  112  is substantially transparent, such that the LEDs  152  are operable to illuminate portions of a front surface of the actuation member. For example, two different color LEDs  152  may be located behind the lower portion  112 B, such that the lower portion is illuminated with blue light when the lighting load  208  is on and with orange light with the lighting load is off. The LEDs  152  behind the upper portion  112 A may be blue and illuminated, for example, as a bar graph to display the intensity of the lighting load  208  when the lighting load is on. The operation of the LEDs  152  is described in greater detail in U.S. patent application Ser. No. 11/472,246, filed Jun. 20, 2006, entitled LIGHTING CONTROL HAVING AN IDLE STATE WITH WAKE-UP UPON ACTUATION, the entire disclosure of which is hereby incorporated by reference. 
     As described herein, the dimmer  100  has a modular assembly and comprises a user interface module  130  and a base module  140 .  FIG. 3  is an exploded perspective view of the dimmer  100  without the faceplate  116  shown.  FIG. 4  is a rear perspective view of the user interface module  130 . The touch sensitive device  150  and the LEDs  152  are included within the user interface module  130 , while the base module  140  houses the load control circuitry of the dimmer  100 , which will be described in greater detail with reference to  FIG. 12 . 
     The bezel  114  serves as a front enclosure portion of the user interface module  130  and defines a substantially flat front surface  115 . The user interface module  130  includes a metal backplate  132 , which serves as a rear enclosure portion of the user interface module and defines a substantially flat rear surface. The metal backplate  132  provides the user interface module  130  with a rigid structure. Alternatively, the backplate  132  could be made from a different rigid material, for example, Rynite® FRS43 resin, which is 43% glass reinforced polyethylene. A plurality of posts  134  may be heat-staked to attach the bezel  114  to the metal backplate  132 . The user interface module  130  is adapted to be captured between the base module  140  and the faceplate  116  such that the touch sensitive actuator  110  is provided in the opening  118 . Accordingly, the user interface module  130  does not attach to the base module  140  using screws or snaps. 
     The user interface module  130  includes a user interface module connector  135  operable to be coupled to a base module connector  142  of the base module  140 . The user interface module connector  135  has a mating end, e.g., a plurality of pins  136 , which are received by a mating end, e.g., a plurality of holes  144 , of the base module connector  142  to provide a plurality of electrical connections (e.g., 20 connections) between the user interface module and the base module. The pins  136  are surrounded by walls  138 , which are received in an opening  145  of the yoke  122 . 
     The user interface module  130  further comprises two posts  139 , which are received in openings  146 ,  148  in the adapter  120 . The posts  139  assist in aligning the user interface module  130  during installation of the user interface module on the base module  140 . The second opening  148  is slightly elongated to allow for adjustment of the user interface module  130  to ensure that the touch sensitive actuator  110  is aligned within the opening  118  of the faceplate  116 . The adapter  120  further comprises two indentations  149 , which allow the fingers of a user to grasp the user interface module  130  to remove (i.e., uninstall) the user interface module from the base module  140 . 
     The user interface module  130  is cantilevered over the mounting holes  124  and thus the mounting screws (not shown) when the dimmer  100  is installed in an electrical wallbox. The periphery of the user interface module  130  extends beyond the periphery of the wallbox opening. Therefore, the touch sensitive actuator  110  extends beyond the periphery of the wallbox opening. 
       FIG. 5A  is a front view and  FIG. 5B  is a right side view of the dimmer  100  with the user interface module  130  installed on the base module  140 , but without the faceplate  116  present.  FIG. 5C  is a bottom cross-sectional view of the user interface module  130  taken through one of the posts  134  as shown in  FIG. 5A .  FIG. 6  is a right side cross-sectional view of the dimmer  100  taken along the center-line of the dimmer  100 . 
     As previously mentioned, the touch sensitive device  150  and the LEDs  152  are housed within the user interface module  130 . Referring to  FIG. 6 , the LEDs  152  are mounted to a user interface module PCB  154  and are arranged in a linear array immediately behind the actuation member  112 .  FIGS. 7A and 7B  are front and rear perspective views, respectively, of the user interface module PCB  154 . A blue LED  155 A and a orange LED  155 B are mounted to the user interface PCB  154  behind the lower portion  112 B of the actuation member  112  to alternately illuminate the lower portion blue and orange, respectively. Alternatively, other colors of LEDs  152  may be used. 
     The actuation member  112  includes a plurality of actuation posts  156 , which contact the front surface of the touch sensitive device  150  and are arranged in a linear array along the length of the actuation member. The posts  156  act as force concentrators to concentrate the force from an actuation of the actuation member  112  to the touch sensitive device  150 . The user interface module PCB  154  includes a plurality of holes  159 , which the actuation posts  156  extend through to contact the touch sensitive device  150 . Accordingly, the LEDs  152  are located above the touch sensitive device  150 . The touch sensitive actuator  110  is described in greater detail in co-pending commonly-assigned U.S. patent application Ser. No. 11/471,908, filed Jun. 20, 2006, entitled TOUCH SCREEN ASSEMBLY FOR A LIGHTING CONTROL, the entire disclosure of which is hereby incorporated by reference. 
     The bezel  114  is clamped to the backplate  132  of the user interface module  130 , such that the touch sensitive device  150  is sandwiched (i.e., compressed) between the bezel and the backplate. For example, the pins  134  are heat-staked to clamp the bezel  114  to the backplate  132  as shown in  FIG. 5C . The user interface PCB  154  is retained, but not compressed, between the bezel  114  and the backplate  132 . The actuation member  112  is captured between the bezel  114  and the user interface PCB  154 , and the posts  156  extend through the holes  159  of the user interface PCB, such that the posts are operable to contact the touch sensitive device  150  when the actuation member  112  is actuated. The posts  156  do not exert force on the touch sensitive device  150  when the touch sensitive actuator  110  is not being actuated. A distance X between the front surface of the actuation member  112  and the rear surface of the user interface module  130  is approximately 0.298 inch. Further, a distance Y between the front surface  115  of the bezel  114  and the rear surface of the user interface module  130  is approximately 0.178 inch. 
     Since the bezel  114  is clamped to the backplate  132  with the touch sensitive device  150  compressed between the bezel and the backplate, a distance D between the posts  156  and the touch sensitive device  150  may be minimized while still preventing the posts from undesirably actuating the touch sensitive device  150 . The distance D is determined by the tolerances on a distance D 112  between a surface  112 A of the actuation member  112  and the ends of the posts  156 , and a distance D 114  between a surface  114 A and a surface  114 B of the bezel  114  as shown in  FIG. 5C . The tolerances of the touch sensitive device  150  and the user interface PCB  154  do not affect the distance D. Minimizing the distance D provides for an improved aesthetic design and prevents the actuation member  112  from having a loose and sloppy feeling when the touch sensitive actuator  110  is actuated, thus providing a high quality fit, finish, and feel. 
     The touch sensitive device  150  may comprise, for example, a resistive touch pad. Alternatively, the touch sensitive device  150  may comprise a capacitive touch pad or any other type of touch responsive element, which are well known to those of ordinary skill in the art. The touch sensitive device  150  is coupled to the user interface module PCB  154  via a connector  158 . As will be described below in greater detail, the touch sensitive device  150  provides a control signal representative of the position where the touch sensitive device was actuated along the longitudinal axis of the touch sensitive device. A controller  214  ( FIG. 12 ) of the dimmer  100  receives the control signal from the touch sensitive device and controls the lighting load  208  accordingly. 
     The internal circuitry of the dimmer  100  (i.e., the load control circuitry of  FIG. 12 ) is mounted to a main (or load control) printed circuit board (PCB)  160 . The main PCB  160  is held in place between the ring portion  128  and the back portion  129  of the enclosure  126  as shown in  FIG. 6 . The ring portion  128  defines an opening of the enclosure  126 , which is essentially covered by the yoke  122 . 
       FIG. 8  is a right side cross-sectional view and  FIG. 9  is a top cross-sectional view of the dimmer  100  taken through the middle of the base module connector  142  of the base module  140 .  FIG. 10  is a front cross sectional view of the dimmer  100  showing the base module connector. 
     To facilitate the installation of the user interface module  130  on the base module  140 , the base module connector  142  is operable to move slightly along a longitudinal axis (i.e., the Y-axis as shown in  FIG. 5A ) and along a lateral axis (i.e., along the X-axis) of the base module. In other words, the base module connector  142  moves in a plane that is substantially parallel with the plane of the front surface of the faceplate  116  and that is substantially coincident with the plane of the opening of enclosure  126  (i.e., as defined by the ring portion  128 ). When the user interface module  130  is installed on the base module  140 , the freedom of movement of the base module connector  142  allows the touch sensitive actuator  110  to be easily aligned in the opening  118  of the faceplate  116 . Therefore, opening  118  of the faceplate  116  can be sized such that there is a minimal distance between the sides of the opening and surface of the touch sensitive actuator  110 . This provides a clean, seamless appearance of the dimmer  100 . 
       FIG. 11  is an exploded view of the assembly of the flexible base module connector  142 . The base module connector  142  is mounted to a connector PCB  162 , which is connected to the main PCB  160  via a flexible ribbon cable  164 . Alternatively, other types of flexible connectors may be used. The ribbon cable  164  has a first end connected to a first ribbon connector  165  (e.g., a right-angle ribbon connector) mounted to the main PCB  160  and fixed in location with reference to the enclosure  126 . The ribbon cable  164  also has a second end, which is opposite the first end and is connected to a second ribbon connector  166  (e.g., a right-angle ribbon connector) mounted to the connector PCB  162 . The ribbon cable  164  wraps around (e.g., in a U -shape, i.e., a 180° bend, as shown in  FIGS. 9-11 ), such that the connector PCB  162  rests on a support rail  168  of the ring portion  128  of the enclosure  126 . Accordingly, the connector PCB  162  is slidably captured by the enclosure  126  and is free to translate across the support rail  168  to allow for movement of the base module connector  142  along the longitudinal and lateral axes. Alternatively, the first ribbon connector  165  may comprise a straight ribbon connector and the ribbon cable  164  may curve down in an L-shape (i.e., a 90° bend) from the second ribbon connector  166  to the first ribbon connector. 
     A frame  170  is provided over the base module connector  142  and connects to the connector PCB  162  via snaps  172 . The base module connector  142  is provided through an opening  174  in the frame  170 . The opening  174  comprises notches  175  that receive alignment rails  176  of the user interface module connector  135 . The notches  175  and the alignment rails  176  help to align the pins  136  of the user interface module connector  135  with the holes  144  of the base module connector  142 . 
     The user interface module  130  of the present invention allows for easily changing the color of the dimmer  100  and the colors of the LEDs  152  after the dimmer  100  is installed. For example, the multiple user interface modules  130  may be available with different colors of the bezel  114  and the LEDs  152 . While the dimmer  100  is installed in an electrical wallbox and is powered, the user first removes the presently-installed user interface module  130  having LEDs having a first color (e.g., blue). The user then acquires a new user interface module  130  having LEDs of a different color (e.g., green), and connects the user interface module connector  135  to the base module connector  142  of the base module  140  to energize the LEDs of the user interface. 
       FIG. 12  is a simplified block diagram of the dimmer  100 . The dimmer  100  has a hot terminal  202  connected to an AC voltage source  204  and a dimmed hot terminal  206  connected to a lighting load  208 . The user interface module  130  comprises the touch sensitive device  150  and the LEDs  152 . The base module comprise a controllably conductive device (e.g., a bidirectional semiconductor switch  210 ), a gate drive circuit  212 , the controller  214 , a zero-crossing detect circuit  216 , a power supply  218 , a stabilizing circuit  220 , a usage detection circuit  222 , an audible sound generator  224 , and a non-volatile memory  225 . The user interface module connector  136  connects to the base module connector  142  to electrically connect the user interface module  130  and the base module  140 . 
     The bidirectional semiconductor switch  210  is coupled between the hot terminal  202  and the dimmed hot terminal  206  to control the current through, and thus the intensity of, the lighting load  208 . The semiconductor switch  210  has a control input (or gate), which is connected to the gate drive circuit  212 . The input to the gate renders the semiconductor switch  210  selectively conductive or non-conductive, which in turn controls the power supplied to the lighting load  208 . The gate drive circuit  212  provides a control input to the semiconductor switch  210  in response to a control signal from the controller  214 . The controller  214  may be any suitable controller, such as a microcontroller, a microprocessor, a programmable logic device (PLD), or an application specific integrated circuit (ASIC). 
     The zero-crossing detect circuit  216  determines the zero-crossing points of the AC source voltage from the AC power supply  204 . A zero-crossing is defined as the time at which the AC supply voltage transitions from positive to negative polarity, or from negative to positive polarity, at the beginning of each half-cycle. The zero-crossing information is provided as an input to the controller  214 . The controller  214  generates the gate control signals to operate the semiconductor switch  210  to thus provide voltage from the AC power supply  204  to the lighting load  208  at predetermined times relative to the zero-crossing points of the AC waveform. 
     The power supply  218  generates a direct-current (DC) voltage V CC , e.g., 5 volts, to power the controller  214  and other low voltage circuitry of the dimmer  100 . For example, the power supply  218  may comprise an isolated power supply, such as a flyback switching power supply, and the zero crossing detect circuit  216  and the gate drive circuit  212  include optocouplers, such that the controller  214 , the base module connector  142 , and the circuitry of the user interface module  130  are electrically isolated from mains voltage, i.e., the AC power source  204 . 
     The touch sensitive device  150  is coupled to the controller  214  through the stabilizing circuit  220  and the usage detection circuit  222 . The stabilizing circuit  220  is operable to stabilize the voltage output of the touch sensitive device  150 . Accordingly, the voltage output of the stabilizing circuit  220  is not dependent on the magnitude of the force of the point actuation on the touch sensitive device  150 , but rather is dependent solely on the position of the point actuation. The usage detection circuit  222  is operable to detect when a user is actuating the touch sensitive actuator  110  of the dimmer  100 . The controller  214  is operable to control the operation of the stabilizing circuit  220  and the usage detection circuit  222  and to receive control signals from both the stabilizing circuit and the usage detection circuit. The stabilizing circuit  220  has a slow response time, while the usage detection circuit  222  has a fast response time. Thus, the controller  214  is operable to control the semiconductor switch  210  in response to the control signal provided by the stabilizing circuit  220  when the usage detection circuit  222  has detected an actuation of the touch sensitive device  150 . 
     If the user interface module  130  is disconnected from the base module  140 , the controller  214  controls of the semiconductor switch  210  to maintain the intensity of the lighting load  208  at the last level to which the lighting load was controlled. Also, the controller  214  is operable to control the semiconductor switch  210  appropriately in the event of a fault condition (e.g., an overcurrent condition through the semiconductor switch  210  or overvoltage condition across the dimmer  100 ) when the user interface module  130  is disconnected from the base module  140 . Additionally, the user interface module  130  may comprise a communication circuit (not shown) adapted to be coupled to a communication link (e.g., a wired communication link or a wireless communication link, such as a radio-frequency (RF) or infrared (IR) communication link), such that the controller  214  is operable to transmit and receive digital messages via the communication link. Accordingly, the controller  214  may control the semiconductor switch  210  in response to a received digital message even when the user interface module  130  is disconnected from the base module  140 . 
     The controller  214  is operable to drive the LEDs  152  to display a representation of the amount of power being delivered to the lighting load  208 . The controller  214  is operable to cause the audible sound generator  224  to produce an audible sound in response to an actuation of the touch sensitive actuator  110 . 
     The memory  225  is coupled to the controller  214  and is operable to store control information of the dimmer  100 . The control information of the dimmer may comprise an advanced programming feature, such as a protected preset, or a fade rate. A user of the dimmer  100  may adjust the control information stored in the memory  225  using an advanced programming mode, which is described in greater detail in commonly-assigned U.S. Pat. No. 7,190,125, issued Mar. 13, 2007, entitled PROGRAMMABLE WALLBOX DIMMER, the entire disclosure of which is hereby incorporated by reference. Since the memory  225  is located in the base module  140 , the memory  225  is operable to retain the control information if the user interface module  130  is replaced, e.g., to change the colors of the LEDs  152 . 
     The user interface module  130  may also comprise a non-volatile memory (not shown). The memory of the user interface module  130  could store control information specific to the operation of the user interface module, for example, the type of touch sensitive member  150  or the number of LEDs  152 . Further, the memory of the user interface module  130  could also store the function of the user interface module, for example, whether the touch sensitive actuator  110  provides dimming functionality (to adjust the intensity of the lighting load  208 ), switching functionality (to toggle the lighting load on and off), radio-frequency communication functionality, infrared -receiving functionality (to receive wireless remote control signals), timer functionality (to control the lighting load off after a predetermined amount of time), or occupancy sensor functionality (to control the lighting load in response to a space near the dimmer  100  being occupied). The controller  214  could read the memory of the user interface module  130  at startup and then operate with the desired functionality. Alternatively, the user interface module  130  could comprise a passive circuit (not shown), for example, a resistor network, coupled to the controller  214 , such that the controller is responsive to the voltage generated across (and thus, the resistance of) the resistors of resistor network. Accordingly, the resistors of the passive circuit could differ in resistance (between user interface modules  130  having different functionalities) depending upon the desired functionality of the user interface module. 
       FIG. 13A  and  FIG. 13B  are simplified schematic diagrams of the circuitry between the touch sensitive device  150  and the controller  214 , i.e., the stabilizing circuit  220  and the usage detection circuit  222 . As shown in  FIGS. 13A and 13B , the touch sensitive device  150  has four connections, i.e., electrodes, and provides two outputs: a first output representative of the position of a point actuation along the Y-axis, i.e., the longitudinal axis of the dimmer  100  a shown in  FIG. 5B , and a second output representative of the position of the point actuation along the X-axis, i.e., an axis perpendicular to the longitudinal axis. The touch sensitive device  150  provides the outputs depending on how the DC voltage V CC  and circuit common are connected to the touch sensitive device. The stabilizing circuit  220  is operatively coupled to the first output and the usage detection circuit  222  is operatively coupled to the second output. 
     The controller  214  controls three switches  260 ,  262 ,  264  to connect the touch sensitive device  150  to the DC voltage V CC  and circuit common. When the switches  260 ,  262 ,  264  are connected in position A as shown in  FIG. 13A , the DC voltage V CC  is coupled across the Y-axis resistor, and the X-axis resistor provides the output to the stabilizing circuit  220 . When the switches  260 ,  262 ,  264  are connected in position B as shown in  FIG. 13B , the DC voltage V CC  is coupled across the X-axis resistor, and the Y-axis resistor provides the output to the usage detection circuit  222 . 
     The stabilizing circuit  220  comprises a capacitor C 230 , has a substantially large value of capacitance, e.g., 10 μF. When the switches  260 ,  262 ,  264  are connected in position A as shown in  FIG. 13A , the capacitor C 230  of the stabilizing circuit  220  is coupled to the output of the touch sensitive device  150 , such that the output voltage is filtered by the capacitor C 230 . When a touch is present on the actuation member  112 , the voltage on the capacitor C 230  will be forced to a steady-state voltage representing the position of the touch on the actuation member  112 . When no touch is present, the voltage on the capacitor will remain at a voltage representing the position of the last touch. When a light or transient press is applied to the touch sensitive device  150 , the capacitor C 230  will continue to hold the output at the voltage representing the position of the last touch. The output of the stabilizing circuit  220  is representative of only the position of the point of actuation of the touch sensitive device  150 . 
     The usage detection circuit  222  comprises a resistor R 234  and a capacitor C 236 . When the switches  260 ,  262 ,  264  are connected in position B as shown in  FIG. 13B , the parallel combination of the resistor R 234  and the capacitor C 236  is coupled to the output of the touch sensitive device  150 . The capacitor C 236  may have a substantially small capacitance C 236 , such that the capacitor C 236  charges substantially quickly in response to all point actuations on the touch sensitive actuator  110 . The resistor R 234  allows the capacitor C 236  to discharge quickly when the switch  260  is in position A. Therefore, the output of the usage detection circuit  222  is representative of the instantaneous usage of the touch sensitive device  150 . 
     The controller  214  controls the switches  260 ,  262 ,  264  to position B for a short period of time t USAGE  once every half-cycle of the voltage source  204  to determine whether the user is actuating the touch sensitive actuator  110 . For example, the short period of time t USAGE  may be approximately 100 μsec or 1% of the half-cycle (assuming each half-cycle is 8.33 msec long). For the remainder of the time, the switches  260 ,  262 ,  264  are in position A, such that the capacitor C 230  is operable to charge to a voltage representing the position of the touch on the actuation member  112  when the touch sensitive device  110  is presently being actuated. When the switches  260 ,  262 ,  264  are in position B, the controller  214  determines whether the touch sensitive device  150  is presently being actuated using the usage detection circuit  222 , and the capacitor C 230  of the stabilizing circuit  220  is unable to discharge at a significant rate, such that the voltage developed across the capacitor C 230  does not change significantly. The operation of the stabilizing circuit  220 , the usage detection circuit  222 , and the switches  260 ,  262 ,  264  is described in greater detail in co -pending, commonly-assigned U.S. patent application Ser. No. 11/471,914, filed Jun. 20, 2006, entitled FORCE INVARIANT TOUCH SCREEN, the entire disclosure of which is hereby incorporated by reference. 
       FIG. 14  is a simplified schematic diagram of the audible sound generator  224  of the dimmer  100 . The audible sound generator  224  uses an audio power amplifier integrated circuit (IC)  240 , for example, part number TPA721 manufactured by Texas Instruments, Inc., to generate a sound from a piezoelectric or magnetic speaker  242 . The amplifier IC  240  is coupled to the DC voltage V CC  (pin  6 ) and circuit common (pin  7 ) to power the amplifier IC. A capacitor C 244  (e.g., having a capacitance of 0.1 μF) is coupled between the DC voltage V CC  and circuit common to decouple the power supply voltage and to ensure the output total harmonic distortion (THD) is as low as possible. 
     The audible sound generator  224  receives a SOUND ENABLE signal  246  from the controller  214 . The SOUND ENABLE signal  246  is provided to an enable pin (i.e., pin  1 ) on the amplifier IC  240 , such that the audible sound generator  224  will be operable to generate the sound when the SOUND ENABLE signal is at a logic high level. 
     The audible sound generator  224  further receives a SOUND WAVE signal  248  from the controller  214 . The SOUND WAVE signal  248  is an audio signal that is amplified by the amplifier IC  240  to generate the appropriate sound at the speaker  242 . The SOUND WAVE signal  248  is first filtered by a low-pass filter comprising a resistor R 250  and a capacitor C 252 . For example, the resistor R 250  has a resistance of 1 kΩ and the capacitor C 252  has a capacitance of 0.1 nF. The filtered signal is then passed through a capacitor C 254  to produce an input signal V IN . The capacitor C 254  allows the amplifier IC to bias the input signal V IN  to the proper DC level for optimum operation and has, for example, a capacitance of 0.1 μF. The input signal V IN  is provided to a negative input (pin  4 ) of the amplifier IC  240  through a input resistor R I . A positive input (pin  3 ) of the amplifier IC  240  and a bypass pin (pin  2 ) are coupled to circuit common through a bypass capacitor C 256  (e.g., having a capacitance of 0.1 μF). 
     The output signal V OUT  of the amplifier IC  240  is produced from a positive output (pin  5 ) to a negative output (pin  8 ) and is provided to the speaker  242 . The negative input (pin  4 ) is coupled to the positive output (pin  5 ) through an output resistor R F . The gain of the amplifier IC  240  is set by the input resistor R I  and the feedback resistor R F , i.e.,
 
Gain= V   OUT   /V   IN =−2·( R   F   /R   I ).
 
For example, the input resistor R I  and the output resistor R F  both have resistances of 10 kΩ, such that the gain of the amplifier IC  240  is negative two (−2).
 
       FIG. 15  is a flowchart of an actuation procedure  300  executed by the controller  214  of the dimmer  100  according to the present invention. The actuation procedure  300  is called from the main loop of the software of the controller  214 , for example, once every half-cycle of the AC voltage source  204 . The actuation procedure  300  selectively executes one of three procedures depending upon the state of the dimmer  100 . If the dimmer  100  is in an “Idle” state (i.e., the user is not actuating the touch sensitive device  150 ) at step  310 , the controller  214  executes an Idle procedure  400 . If the dimmer  100  is in an “ActiveHold” state (i.e., the user is presently actuating the touch sensitive device  150 ) at step  320 , the controller  214  executes an ActiveHold procedure  500 . If the dimmer  100  is in a “Release” state (i.e., the user has recently ceased actuating the touch sensitive device  150 ) at step  330 , the controller  214  executes a Release procedure  600 . 
       FIG. 16  is a flowchart of the Idle procedure  400  according to the present invention. The controller  114  uses a “sound flag” and a “sound counter” to determine when to cause the audible sound generator  224  to generate the audible sound. The purpose of the sound flag is to cause the sound to be generated the first time that the controller  214  executes the ActiveHold procedure  500  after being in the Idle state. If the sound flag is set, the controller  214  will cause the sound to be generated. The sound counter is used to ensure that the controller  214  does not cause the audible sound generator  224  to generate the audible sound too often. The sound counter has a maximum sound counter value S MAX , e.g., approximately 425 msec. Accordingly, there is a gap of approximately 425 msec between generations of the audible sound. The sound counter is started during the Release procedure  600  as will be described in greater detail below. Referring to  FIG. 16 , upon entering the Idle state, the controller  214  sets the sound flag at step  404  if the sound flag is not set at step  402 . 
     An “LED counter” and an “LED mode” are used by the controller  214  to control the visual indicators  114  (i.e., the LEDs  152 ) of the dimmer  100 . The controller  214  uses the LED counter to determine when a predetermined time t LED  has expired since the touch sensitive device  150  was actuated. When the predetermined time t LED  has expired, the controller  214  will change the LED mode from “active” to “inactive”. When the LED mode is “active”, the visual indicators  114  are controlled such that one or more of the visual indicators are illuminated to a bright level. When the predetermined time t LED  expires, the LED mode is changed to “inactive”, i.e., the visual indicators  114  are controlled such that one or more of the visual indicators are illuminated to a dim level. Referring to  FIG. 16 , if the LED counter is less than a maximum LED counter value L MAX  at step  410 , the LED counter is incremented at step  412  and the process moves on to step  418 . However, if the LED counter is not less than the maximum LED counter value L MAX , the LED counter is cleared at step  414  and the LED mode is set to inactive at step  416 . Since the actuation procedure  300  is executed once every half-cycle, the predetermined time t LED  is equal to
 
 t   LED   =T   HALF   ·L   MAX ,
 
where T HALF  is the period of a half-cycle.
 
     Next, the controller  214  samples the output of the usage detection circuit  222  to determine if the touch sensitive device  150  is being actuated. For example, the usage detection circuit  222  may be monitored once every half-cycle of the voltage source  204 . At step  418 , the controller  214  controls the switches  260 ,  262 ,  264  to position B to couple the resistor R 234  and the capacitor C 236  to the output of the touch sensitive device  150 . The controller  214  samples the DC voltage of the output of the usage detection circuit  222  at step  420  by using, for example, an analog-to-digital converter (ADC). Next, the controller  214  controls the switches  260 ,  262 ,  264  to position A at step  422 . 
     At step  424 , if there is activity on the touch sensitive actuator  110  of the dimmer  100 , i.e., if the DC voltage sampled at step  420  is above a predetermined minimum voltage threshold, then an “activity counter” is incremented at step  426 . Otherwise, the activity counter is cleared at step  428 . The activity counter is used by the controller  214  to determine if the DC voltage determined at step  420  is the result of a point actuation of the touch sensitive device  150  rather than noise or some other undesired impulse. The use of the activity counter is similar to a software “debouncing” procedure for a mechanical switch, which is well known to one having ordinary skill in the art. If the activity counter is not less than a maximum activity counter value A MAX  at step  430 , then the dimmer state is set to the ActiveHold state at step  432 . Otherwise, the process simply exits at step  434 . 
       FIGS. 17A and 17B  are flowcharts of the ActiveHold procedure  500 , which is executed once every half-cycle when the touch sensitive device  150  is being actuated, i.e., when the dimmer  100  is in the ActiveHold state. First, a determination is made as to whether the user has stopped using, i.e., released, the touch sensitive device  150 . The controller  214  controls the switches  260 ,  262 ,  264  to position B at step  510 , and samples the output of the usage detection circuit  222  at step  512 . At step  514 , the controller  214  controls the switches  260 ,  262 ,  264  to position A. If there is no activity on the touch sensitive actuator  110  of the dimmer  100  at step  516 , the controller  214  increments an “inactivity counter” at step  518 . The controller  214  uses the inactivity counter to make sure that the user is not still actuating the touch sensitive device  150  before entering the Release mode. If the inactivity counter is less than a maximum inactivity counter value IMAX at step  520 , the process exits at step  538 . Otherwise, the dimmer state is set to the Release state at step  522 , and then the process exits. 
     If there is activity on the touch sensitive device  150  at step  516 , the controller  214  samples the output of the stabilizing circuit  220 , which is representative of the position of the point actuation on the touch sensitive actuator  110  of the dimmer  100 . Since the switches  260 ,  262 ,  264  are in position A, the controller  214  determines the DC voltage at the output of the stabilizing circuit  220  at step  524  using, for example, the analog-to-digital converter. 
     Next, the controller  214  uses a buffer to “filter” the output of stabilizing circuit  220 . When a user actuates the touch sensitive device  150 , the capacitor C 230  will charge across a period of time sampled by the first time constant τ 1  to approximately the steady-state voltage representing the position of the point actuation on the actuation member  112  as previously described. Since the voltage across the capacitor C 230 , i.e., the output of the stabilizing circuit  220 , is increasing during this time, the controller  214  delays for a predetermined period of time at step  525 , e.g., for approximately three (3) half-cycles. 
     When a user&#39;s finger is removed from the actuation member  112 , subtle changes in the force and position of the point actuation occur, i.e., a “finger roll-off” event occurs. Accordingly, the output signal of the touch sensitive device  150  is no longer representative of the position of the point actuation. To prevent the controller  214  from processing samples during a finger roll-off event, the controller  214  saves the samples in the buffer and processes the samples with a delay, e.g., six half-cycles later. Specifically, when the delay is over at step  525 , the controller  214  rotates the new sample (i.e., from step  524 ) into the buffer at step  526 . If the buffer has at least six samples at step  528 , the controller  214  averages the samples in the fifth and sixth positions in the buffer at step  530  to produce the touch position data. In this way, when the user stops actuating the touch sensitive device  150 , the controller  214  detects this change at step  516  and sets the dimmer state to the Release state at step  522  before the controller processes the samples saved in the buffer near the transition time of the touch sensitive device. 
     At step  532 , the controller  114  determines if the touch position data from step  530  is in a keepout region, i.e., near the notch  125 . If the touch position data is in the keepout region, the ActiveHold procedure  500  simply exits at step  538 . Otherwise, a determination is made at step  534  as to whether the sound should be generated. Specifically, if the sound flag is set and if the sound counter has reached a maximum sound counter value S MAX , the controller  214  drives the SOUND ENABLE signal  246  high and provides the SOUND WAVE signal  248  to the audible sound generator  224  to generate the sound at step  535 . Further, the sound flag is cleared at step  536  such that the sound will not be generated as long as the dimmer  100  remains in the ActiveHold state. 
     If the touch position data is in the toggle area, i.e., the lower portion  112 B of the actuation member  112 , at step  540 , the controller  214  processes the actuation of the touch sensitive device  150  as a toggle. If the lighting load  208  is presently off at step  542 , the controller  214  turns the lighting load on. Specifically, the controller  214  illuminates the lower portion  112 B of the actuation member  112  with the blue LED  155 A at step  544  and dims the lighting load  208  up to the preset level, i.e., the desired lighting intensity of the lighting load, at step  546 . If the lighting load is presently on at step  542 , the controller  214  turns on the orange LED  155 B at step  548  and fades the lighting load  208  to off at step  550 . 
     If the touch position data is not in the toggle area at step  540 , the controller  214  scales the touch position data, i.e., the sample of the output of the stabilizing circuit  220 , at step  552 . The output of the stabilizing circuit  220  is a DC voltage between a maximum value, e.g., substantially the DC voltage V CC , and a minimum value, which corresponds to the DC voltage provided by the touch sensitive device  150  when a user is actuating the lower end of the upper portion  112 A of the actuation member  112 . The controller  214  scales this DC voltage to be a value between off (i.e., 1%) and full intensity (i.e., 100%) of the lighting load  208 . At step  554 , the controller  214  dims the lighting load  208  to the scaled level produced in step  552 . 
     Next, the controller  214  changes the LEDs  152  located behind the actuation member  112 . As a user actuates the touch sensitive device  150  to change intensity of the lighting load  208 , the controller  214  decides whether to change the LED  152  that is presently illuminated. For example, the controller  214  may use hysteresis to control the LEDs  152  such that if the user actuates the upper portion  112 A of the actuation member  112  at a boundary between two of the regions of intensities described above, consecutive visual indicators do not toggle back and forth. 
     Referring to  FIG. 17B , a determination is made as to whether a change is needed as to which LED  152  is illuminated at step  556 . If the present LED  152  (in result to the touch position data from step  530 ) is the same as the previous LED, then no change in the LED is required. The present LED  152  is set the same as the previous LED at step  558 , a hysteresis counter is cleared at step  560 , and the process exits at step  570 . 
     If the present LED  152  is not the same as the previous LED at step  556 , the controller  214  determines if the LED should be changed. Specifically, at step  562 , the controller  214  determines if present LED  152  would change if the light level changed by 2% from the light level indicated by the touch position data. If not, the hysteresis counter is cleared at step  560  and the process exits at step  570 . Otherwise, the hysteresis counter is incremented at step  564 . If the hysteresis counter is less than a maximum hysteresis counter value H MAX  at step  566 , the process exits at step  570 . Otherwise, the LEDs  152  are changed accordingly based on the last sample of the output of the stabilizing circuit  220  at step  568 . 
       FIG. 18  is a flowchart of the Release procedure  600 , which is executed after the controller  214  sets the dimmer state to the Release state at step  522  of the ActiveHold procedure  500 . First, a save flag is set at step  610 . Next, the sound counter is reset at step  612  to ensure that the sound will not be generated again, e.g., for 18 half-cycles. At step  618 , a determination is made as to whether the dimmer  100  is presently executing a fade-to-off. If not, the present level is saved as the preset level in the memory  225  at step  620 . Otherwise, the desired lighting intensity is set to off at step  622 , the long fade countdown in started at step  624 , and the preset level is saved as off in the memory  225  at step  626 . 
     Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.