Abstract:
The present invention is directed to an electrical wiring device that includes a variable control mechanism configured to regulate power to the at least one electrical load by way of a control knob being user settable between a first adjustment stop and a second adjustment stop. A regulation circuit is configured to establish a pre-determined load power setting when the calibration button is actuated when the regulation circuit is in the calibration mode.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to electrical wiring devices, and particularly to power control wiring devices such as dimmer and fan speed control devices. 
         [0003]    2. Technical Background 
         [0004]    In most residences, a simple ON/OFF switch may be the primary way people control lighting fixtures or air-circulating fan fixtures. One obvious drawback to using simple ON/OFF switches to control these devices is experienced when it comes time to pay the electric bill—a given light (or fan) is either ON or OFF—a simple switch is thus unable to vary the amount of light (and hence the amount of power consumed). Stated differently, by controlling light intensity or fan speed in accordance with needed or desired parameters, electricity usage is reduced, saving money and natural resources. In accordance with the present invention, therefore, a power control device refers to an electrical control device that may be employed to adjust the amount of current delivered to any variable electrical load, such as a light or motor. The adjustment is achieved by sliding a lever or rotating a dial. 
         [0005]    When the electric load is a lighting device, the power control device is commonly referred to as a dimmer. For example, when a light is dimmed 25%, a dimmer saves about 20% of the electricity required. When dimmed by 50%, it saves 40% of the electricity. Second, a dimmer greatly extends lamp life because it reduces strain on the filament. When dimmed 20%, a lamp lasts 4 times longer than it would at full power, and dimmed by 50%, it will last as much as 20 times longer. If the power control device is configured to control a motor, such as a fan motor, the power control device is configured to control a motor, such as a fan motor, the power control device is referred to as a motor speed control. Motor speed controllers are also used to control the speed of machinery, such as power tools, electrical drills, chair lifts, stationary machinery, and other such variable motor driven elements. 
         [0006]    Power control devices are typically packaged in a wiring device form factor for installation in a wall outlet box. The wiring device may include one or more power control devices within the device housing. For example, wiring devices that are equipped with both fan motor and lighting control features are ubiquitous. The wiring device may include another power control device such as a switch, protective device, ground fault circuit interrupter (GFCI), arc fault circuit interrupter (AFCI), surge protective device (SPD), occupancy sensor, or receptacle. When a switch is included, it may be wired in series with the dimmer or fan speed control to allow the load to be switched ON or OFF. The conventional wiring device form factor provides a user accessible interface that includes one or more switch mechanisms such as buttons, levers, dials, slide switches, and other such input control mechanisms that permit a user to vary the power to a load or turn it ON/OFF. 
         [0007]    Prior to device installation, wiring from the AC power source and wiring to the load(s) are disposed inside the outlet box. The outlet box is usually located proximate to the load being controlled. The device is installed by connecting the wiring inside the outlet box to the appropriate wiring device terminals disposed on the exterior of the wiring device. The power control wiring device is then inserted into the outlet box and attached to the outlet box using one or more fasteners. A cover plate is installed to complete the installation. 
         [0008]    Turning now to so-called “green” issues, the public has developed an increased awareness of the impact that energy generation has on the environment. Moreover, as the economics of countries such as Brazil, India, China, etc. improve and develop, their need for energy resources increases accordingly. As such, the global demand for energy has risen sharply, while the supply of planet earth&#39;s resources remains fixed. In light of the pressures of supply and demand, the cost of energy resources will only increase. There is thus a need to use limited energy resources more wisely and more efficiently. More efficient light sources and electrical fixtures have been developed to replace the conventional incandescent lighting devices in response to this need. For example, compact fluorescent lights (CFL) and light emitting diode (LED) devices are far more efficient than conventional incandescent lights and thus provide homeowners/tenants with an acceptable level of service while using less energy and incurring lower costs. This may complicate matters somewhat since incandescent lights, fluorescent lights, MLV lighting, CFL devices and LED lighting may have different electrical operating characteristics. 
         [0009]    Thus, one of the drawbacks of a conventional dimmer device is that it may not be compatible with all of the types of lighting devices currently available. The minimum range of adjustment of the dimmer may be fine for one type of light source but cause another type to flicker. The maximum range of adjustment of a conventional dimmer may satisfactorily limit the energy usage for one type of light source but not for another. Conventional fan motor controls have similar issues in that they are not compatible with all the various fan motors currently on the market. 
         [0010]    Moreover, the typical user may want to adjust the operating range of his fan motor or dimmer in accordance with their personal needs and preferences. Some conventional dimmers and fan speed controls have calibration devices that allow the user to set the minimum range of adjustment or the maximum range of adjustment using a trim potentiometer, but not both. Conventional dimmers cannot calibrate both the high end and the low end because trim potentiometers are expensive and bulky; fitting in two potentiometers, one each for the high and low calibration is prohibitive from both a cost and space standpoint. Furthermore, trim potentiometers require large access holes through the device&#39;s heat sink and, thus, the effectiveness of the heat sink is diminished. Once again, using two trim pots is prohibitive, this time from a safety standpoint. 
         [0011]    Accordingly, a need exists for a safe, cost-effective and economic power control device that lets the user calibrate the dimmer device to a variety of electrical loads over a wide range of power settings. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention addresses the needs described above by providing an economical power control device that lets the user calibrate the device to a variety of electrical loads over a wide range of power settings. 
         [0013]    One aspect of the present invention is directed to an electrical wiring device that includes a housing assembly having a plurality of terminals at least partially disposed therein, the plurality of terminals being configured to be coupled to an AC power source and at least one electrical load, the plurality of terminals being configured to provide the electrical wiring device with regulated AC power in a device energized state. At least one variable control mechanism is coupled to the housing assembly, the at least one variable control mechanism being configured to regulate power to the at least one electrical load by way of a control knob being user settable between a first adjustment stop and a second adjustment stop. A user accessible calibration button is included. At least one series pass element coupled to the at least one variable control mechanism, the at least one series pass element being configured to provide load power to the at least one electrical load in accordance with a user setting of the control knob. A regulation circuit is coupled to the user accessible calibration button and the at least one series pass element, the regulation circuit being configured to enter a calibration mode when the control knob is at or near the first adjustment stop or the second adjustment stop and the user manually actuates the calibration button, the regulation circuit establishing at least one pre-determined load power setting when the calibration button is actuated when the regulation circuit is in the calibration mode. 
         [0014]    Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
         [0015]    It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIGS. 1A and 1B  are diagrammatic depictions of three-way switch arrangements in accordance with the present invention; 
           [0017]      FIGS. 2A and 2B  are detailed block diagrams of the present invention in the three-way switch arrangements depicted in  FIGS. 1A and 1B ; 
           [0018]      FIG. 3  is a detailed circuit diagram in accordance with one embodiment of the present invention; 
           [0019]      FIG. 4  is an exploded view of the power control device depicted in  FIGS. 1-3 ; 
           [0020]      FIG. 5A  and  FIG. 5B  are isometric views of a power control device in accordance with another embodiment of the present invention; 
           [0021]      FIG. 6  is a flow chart illustrating a method for calibrating the present invention; and 
           [0022]      FIG. 7  is a flow chart illustrating another method for calibrating the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the power control device of the present invention is shown in  FIG. 1 , and is designated generally throughout by reference numeral  10 . 
         [0024]    As embodied herein and depicted in  FIGS. 1A and 1B , diagrammatic depictions of a three-way switch arrangement in accordance with the present invention are disclosed.  FIG. 1A  shows a typical three-way switch arrangement wherein the AC line voltage (e.g., 120 VAC) is connected to the pole of a first SPDT switch S 1  and the load is connected to the power control device  10  of the present invention. Specifically, the traveler wires of the three-way wiring installation are connected between the two throws of the conventional switch S 1  and the terminals W 1  and W 2 . The load LD is connected between the remaining two terminals of power control device  10 , W 3  and W 4 . Note that in  FIG. 1B , the positions of the switches/power control devices are reversed. Accordingly, the power control device  10  of the present invention may be employed in either position of a three-way switch arrangement. 
         [0025]    Referring to  FIGS. 2A and 2B , detailed block diagrams of the present invention in the three-way switch arrangements depicted in  FIGS. 1A and 1B  are disclosed.  FIG. 2A  is a detail diagram of the arrangement depicted in  FIG. 1A . As before, the pole of the SPDT external switch is connected to AC power and the two traveler wires are connected between the two throws of the SPDT switch and the terminals W 1  and W 2 . Moreover, the load LD, characterized in  FIG. 2A  as a lighting load, is connected between terminals W 3  and W 4 . Terminal W 4  is always connected to the neutral wire of the premise wiring installation. In reference to the interior of the device  10 , terminals W 1 , W 2 , and W 3  are coupled to power supply  100 - 1 . In particular, each terminal (W 1 , W 2 , and W 3 ) is connected to its respective diode (D 1 , D 2 , and D 3 ). The output of the power supply  100 - 1  is provided to the linear regulator circuit  100 - 2 , which is configured to provide +5 VDC to the circuitry that requires a DC power supply (e.g., microprocessor  100 - 10 ). The terminals W 1  and W 2  are connected to the throws of SPDT switch S 2 , which is controlled by the user via a switch actuator (i.e., see switch  30  at  FIG. 4  or switch at  FIG. 5 ). To be clear, the external switch (S 1 ) and the switch S 2  provide the three-way switching functionality. In any event, the pole of the SPDT switch S 2  is connected to the dimmer  100 - 4 . The output of the dimmer, i.e., the regulated power, is provided to the load LD via terminal W 3 . Note that the pole of the SPDT switch S 2  is also connected to the zero-cross (ZC) detector  100 - 3 . The ZC detector  100 - 3  provides the microprocessor  100 - 10  with a ZC detection signal that indicates the 0° and 180° phase position of the AC signal. 
         [0026]      FIG. 2B  is a detail diagram of the arrangement depicted in  FIG. 1B . Here, the pole of the SPDT external switch is connected to the load LD and the two traveler wires are connected between the two throws of the SPDT switch and the terminals W 1  and W 2 . The AC power source is connected between terminals W 3  and W 4 . Terminal W 4  is again connected to the neutral wire of the premise wiring installation. In this arrangement, the AC power is provided to the dimmer  100 - 4  via terminal W 3  and diode D 3 . The regulated power is provided to the load via terminal W 1 . The user can actuate switch S 2  to turn the power off (by directing the regulated power to terminal W 2 ). At the other end of the three-way switching arrangement, if one actuates switch S 1  (Ext. S/W) after switch S 2  is actuated, regulated power is again provided to the load LD. 
         [0027]    As embodied herein and depicted in  FIG. 3 , a detailed circuit diagram in accordance with one embodiment of the present invention is disclosed. The power supply  100 - 1  includes diodes D 1 -D 3  are disposed in parallel with each other such that the AC power signal may be provided to the power supply via terminals W 1 , W 2  or W 3 . The power control device  10  may therefore be placed in either switch position of a retrofit three-way switch arrangement. The rectified signal is then provided to the regulator circuit  100 - 2  comprising transistor T 2  and zener diode D 4  which is configured to provide a+5 VDC power supply for the digital components. 
         [0028]    A slide potentiometer  40 - 3  is coupled to the +5 VDC supply and is used in conjunction with the internal calibration switch S 1  and the locator LED to effect the HIGH/LOW calibration routine. These routines are described in detail below and depicted in  FIGS. 6 and 7 . 
         [0029]    The zero cross detector  100 - 3  is also coupled to the power supply  100 - 1  and provided with a half-wave rectified DC signal via diode D 5  (terminals W 1  or W 2 ) or diode D 9  (W 3 ) such that the zero cross detector  20 - 2  provides a zero cross (ZC) signal to the microprocessor  100 - 10 . The zero cross signal (ZC) is paired with the ZC VREF circuit  100 - 5  to provide a differential input to a differential comparator disposed inside the microcomputer  100 - 10 . The differential signal eliminates common-mode noise to prevent any false zero cross detections by the microcomputer  100 - 10 . 
         [0030]    Before discussing the dimmer circuit, the reader should take note of the phase selection switch S 3 . This switch S 3  is employed by the user to place the device  10  in a forward phase mode or reverse phase mode, depending on the type of load LD being used in the three-way arrangement. As those skilled in the art will appreciate, forward phase control is appropriate for conventional incandescent lighting, magnetic low voltage (MLV) lighting fixtures, conventional fluorescent lighting fixtures employing electronic ballasts (EFL), and halogen lighting. Reverse phase control is generally appropriate for electronic low voltage (ELV) lighting. Bulbs designed as higher efficiency 120V incandescent replacements, including LED bulbs and compact florescent lights (CFL) typically perform better with forward phase control. 
         [0031]    As described above, the dimmer circuit  100 - 4  is coupled between the pole of the SPDT switch S 2  and the hot/load terminal W 3 . The microcomputer  100 - 10  controls the dimmer circuit  30  by providing a pulse width modulation (PWM) signal to the gate of transistor T 1 . The PWM signal propagates at logic levels (+5V, GND) and controls the operation of transistor T 1 ; at least one pulse is provided for each AC line cycle. The width of the PWM pulse is varied to control the amount of power provided to the load, whether a lamp load or a motor load. The use of PWM in conjunction with switch S 3 , allows device  10  to control any type of lighting load by varying the duty cycle of the pulse. In operation, when the PWM signal is high, the transistor T 1  conducts through the OK 1  to turn transistors Q 1  and Q 2  ON in accordance with the timing provided by the PWM signal. For the MOSFET implementation shown herein, two transistors (Q 1 , Q 2 ) are required for operation. This is due to the internal body diode inherent in MOSFET technology; one MOSFET blocks a portion of the positive AC half cycle, and the other blocks a portion of the negative half-cycle to the load. 
         [0032]    The timing of the PWM pulse is of course controlled by the microcomputer  100 - 10  and it is timed relative to the zero crossing of the AC cycle. As noted above, dimming is accomplished in the forward phase by switching the load current ON sometime after the zero-crossing of the AC half-cycle and turned OFF at the next zero-crossing of the AC waveform. Conversely, in reverse phase control, the load current is turned ON when the zero-crossing is detected and turned OFF sometime before the next zero-crossing is detected. Based on the switch S 3  setting, the dimmer circuit  100 - 4  can operate in forward phase when the load LD is implemented by ELV, CFL and LED devices. In one embodiment, the microcontroller  100 - 10  transmits the PWM signal at a very low duty cycle until the I SNS AMP OUT signal (from the load current detector  112 ) indicates that there is a load current being drawn. If the fixture is an incandescent one, the load current in this region is substantially linear with respect to the PWM duty cycle. If the fixture is an LED fixture, the load current will not be present until the duty cycle has been increased to a certain threshold. Stated differently, the present invention employs a control loop that optimizes the PWM duty cycle for any given lighting load. 
         [0033]    Device  10  may include a load sensor detection circuit  100 - 6  that includes a load sensor SNS 1 - 2  coupled to an Op Amp IC 1 . Circuit  100 - 6  provides the L_SNS signal to the microprocessor  100 - 10 . In one embodiment, the detector  100 - 6  is configured as a threshold detector that compares the I SNS signal from the SNS sensor with a predetermined threshold value and provides a logic one (+5V) or a logic zero (0 V) signal to processor  100 - 10 . For example, if the load current is greater than about 10 mA, the detector  112 - 1  is configured to provide a logic one (+5V) signal. If the load current is below the threshold a logic zero (0 V) is provided. Those skilled in the art will appreciate that the threshold level is adjustable and depends on the level of sensitivity desired and the type of load. 
         [0034]    The processor circuit  100 - 10  is implemented using a microcomputer which is selected based on a combination of characteristics including performance, cost, size and power consumption. In other words, the present invention contemplates a variety of models that provide the consumer with options that are closely suited to the consumers&#39; needs and desires. The term “microcomputer performance” refers to an optimal combination of processing speed, memory size, I/O pin capability, and peripheral set capabilities (e.g., A/D converter, comparators, timers, serial bus, etc). As those skilled in the art will appreciate, any suitable processing device may be employed. In one embodiment of the present invention, the microcomputer is implemented by a device known as the “ATtiny44a”, which is manufactured by the Atmel Corporation. In another embodiment that includes more features, the microcomputer is implemented using Atmel&#39;s “ATtiny84a” because the latter device offers more program memory than the former (i.e., 44a). Specifically, the ATtiny 84a includes 8 kB of program memory whereas the ATtiny 44a includes 4 kB of program memory. In one embodiment, the central processing unit (CPU) is operated at a clock frequency that is well below its rated frequency to thereby minimize power consumption. 
         [0035]    It will be apparent to those of skilled in the pertinent art that modifications and variations can be made to the processor circuit  100 - 10  of the present invention depending on the amount and sophistication of features that are provided to the user. As noted previously, any suitable arrangement of hardware and/or software may be employed given the constraints of being disposed in an electrical wiring device. Thus, processor circuit  110  may be implemented using general purpose processors, signal processors, RISC computers, application specific integrated circuits (ASICs), field programmable gate array (FPGA) devices, customized integrated circuits and/or a combination thereof. With respect to the microcomputer  110 - 1  depicted in  FIG. 3 , any suitable microcomputer may be employed including, but not limited to those selected from the Microchip PIC12F family, the Freescale HCO8 family, the Texas Instruments MSP430 family, or the ST Micro STM8 family. 
         [0036]    As embodied here and depicted in  FIG. 4 , an exploded view of the power control device  10  in accordance with the present invention is disclosed. Device  10  includes a device housing  20  that includes back body  20 - 1 , middle housing  20 - 2 , and a heat sink  50 . Mounting screws are used to connect the heat sink (and hence device  10 ) to a wall box (not shown.) The body assembly  20  is connected together by fasteners  2 . An aesthetic cover assembly  60  is provided above the heat sink  50 . The aesthetic cover assembly  60  includes a switch paddle cover  60 - 1  that is configured to snap into frame member  60 - 2 . The frame  60 - 2  includes snap elements that are configured to be inserted into corresponding apertures in the heat sink  50 . Once the aesthetic cover assembly  60  is disposed over the power regulation components ( 30 ,  40 ) and the device is installed, a cover plate (not shown) may be positioned over the interchangeable cover assembly  60  and fastened to heat sink  50  to complete the installation. 
         [0037]    The back body includes openings at each corner thereof to accommodate the wiring terminals  12 - 18 . (The reader should note that the wiring terminals are denoted as W 1 -W 4  in  FIGS. 1-3 ). The terminals  12 - 18  are used to connect the device  10  to the traveler wires and the hot and neutral wires from the electrical distribution system. The terminals  12 - 18  are coupled to their respective wires by the screw and pressure plate assemblies  11 . The filed wires may be wired to these terminals using back wiring or side wiring techniques. The ground terminal comprises a wire  15  that is electrically connected to heat sink  50 . 
         [0038]    A switch controller  30  is provided to turn power to the load LD ON or OFF. The switch controller  30  includes a paddle switch  30 - 1  that is coupled to the switch contacts on traveler terminals  12  and  14  (W 1  and W 2 ) by a toggle element  30 - 3  and a switch spring  30 - 2 . The toggle member  30 - 3  is free to rotate in the cradle formed in the middle frame  20 - 2 . The paddle switch  30 - 1 , of course, is configured to drive the toggle member between ON and OFF positions. The spring  30 - 2  is at greatest compression when the toggle member is half way between the ON and OFF positions to create a saddle point. Note that the switch itself is comprised of the contacts disposed on the toggle member  30 - 3  and the terminals  12  and  14  (W 1  and W 2 , respectively). The switch is configured as a “three way switch” when the toggle member  30 - 3  includes contacts on either side. Although a paddle switch has been disclosed, the invention may be used in combination with other switch configurations including push button switches, magnetically operable switches, toggle switches, test switches, reset switches, and the like. As alluded to above, the switch paddle  30 - 1  is covered by the aesthetic switch cover  60 - 1  when the aesthetic cover assembly is installed over the heat sink  50 . The paddle switch  30 - 1  has a decorative actuator  50 - 2  disposed in aperture  20 - 20  of frame  20 - 10 . 
         [0039]    The dimmer control  40  provides variable power to the electrical load LD. The aesthetic cover assembly  60  includes an aesthetic slider component  60 - 3  that is coupled to the potentiometer  40 - 3  by way of linkage  40 - 1  and  40 - 2 . The aesthetic slider component  60 - 3  is, of course, accessible to the user by way of an elongated opening in frame  60 - 2 . In an alternate embodiment of the invention (not shown), power controller  40  employs a rotary potentiometer instead of a linear potentiometer. 
         [0040]    A printed circuit board (PCB) assembly  100  is disposed in the back body member  20 - 1  under the middle frame  20 - 2 . The PCB assembly  100  may include several PCBs. The main PCB  100 - 1  accommodates the cradle formed in the middle frame  20 - 2 . The capacitors C 1 , C 4 , switches S 1  and S 2  and the potentiometer  40 - 3  are mounted on, and electrically connected to PCB  100 - 1  as shown. Switch S 1  is a push button switch whereas switch S 3  is a slide switch. Both switches are coupled to actuators that are accessible to the user when the cover plate is removed. The actuators are inserted through apertures formed in the heat sink  50 . The S 1  aperture is less than about 0.15 inches in length whereas the S 3  aperture is less than about 0.30 inches in length. The apertures are typically less than about 0.15 inches wide. The apertures are limited in size so that the heat dissipation properties of heat sink  50  are unaffected by the apertures. Lamp LED  1  is disposed on PCB  100 - 1  and is aligned with a light pipe  100 - 2 . Series pass elements Q 1 , Q 2  are thermally coupled to heat sink  50  by way of electrical insulators  100 - 3  and the screw/insulated shoulder assembly  50 - 2 . The microprocessor  100 - 10  is disposed on PCB  100 - 4  which is substantially normal to PCB  100 - 1 . 
         [0041]    Reference is made to U.S. patent Ser. No. 13/332,948 filed on Dec. 21, 2011, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of a power control device having a switch mechanism  30 , power regulation circuit  40 , heat sink  50  and an aesthetic cover  60  as described herein. 
         [0042]    As embodied herein and depicted in  FIGS. 5A and 5B , isometric views of a power control device  10  in accordance with another embodiment of the present invention are disclosed. Device  10  includes a switch cover  204  disposed on heat sink assembly  202 . As before, the power handling PCB  10 - 1  is disposed under the heat sink  202  and within the back body member  200 .  FIG. 5B  is a rear isometric view of the power control device depicted in  FIG. 20  and shows the back body member  200  and the heat sink  202 . 
         [0043]    In this embodiment, the microcomputer  100 - 10  is connected to three user-operated buttons (i.e., an ON/OFF switch plate  204 , a down button “−”, and an up button “+”). Each button circuit is pulled to a logic high (+5V) by a 100K pull-up resistor. When a user depresses a button, its corresponding switch in the device is closed to ground the circuit such that the microcomputer  100 - 10  reads a logic zero (0 V) to indicate that the user has made a command. With respect to the ON/OFF button  204 , if the current state of the wiring device is “OFF,” an actuation of the button  204  directs the microcontroller to actuate a relay that turns the load “ON.” When the user depresses the button again, the same sequence plays out and the relay turns the load “OFF.” The “down button” circuit and the “up button” circuit operate in the same identical way that the ON/OFF button operates. Obviously, the difference is in the way that the microcomputer  100 - 10  interprets the commands. An actuation of the up-button is interpreted as a command to increase the power delivered to the load, and an actuation of the down-button is just the opposite. 
         [0044]    In particular, when the down-button is depressed, the software in the microcontroller changes the PWM signal such that the dimmer circuit  100 - 4  causes the lighting load to be incrementally dimmed (Of course, the circuit may be used to slow an electric motor, e.g., a fan motor). Conversely, when the up-button is depressed, the software in the microcontroller changes the PWM signal such that the dimmer circuit  100 - 4  causes the lighting load to be incrementally raised. The programming header  100 - 7  ( FIG. 3 ) allows a person having the appropriate skill level to reprogram and/or debug the microcomputer  100 - 10  when the up and/or down buttons are depressed in a predetermined sequence. As described below, these buttons are also employed to perform the manual calibration routines described herein. 
         [0045]      FIG. 5A  also shows a linear array of LEDs disposed between the + button and the − button. In this embodiment, the microcontroller  100 - 10  is connected to a display circuit by a serial clock signal (SCL) and a serial data signal to provide a serial bit stream that corresponds to the appropriate device display settings. The display settings are transmitted to the display circuit when the settings are changed by a user input command and refreshed periodically. In one embodiment of the present invention, the microcomputer refreshes the settings every 300 msec, or at a 3.3 Hz rate. Of course, any suitable refreshing rate may be selected depending on the processor load. 
         [0046]    The display circuit  130  may be implemented by an I/O expander circuit that is configured to receive the serial bit stream from the microcomputer  100 - 10  and convert it into a parallel data output for use by the display LEDs. In the embodiment of  FIG. 5A , seven (7) bar graph LEDs are provided that provide the user with an indication of the dimmer setting. For example, if one LED is ON and the other six LEDs are OFF, the bar graph indicates to the user that the light level setting is at its lowest setting. Conversely, if all seven (7) LEDs in the bar graph  130 - 2  are illuminated, the dimmer is at its highest setting. 
         [0047]    Reference is made to U.S. patent Ser. No. 13/792,566, filed on Mar. 11, 2013, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of a push button switch mechanism. 
         [0048]    Referring to  FIGS. 6 and 7 , a method for setting maximum and minimum output voltage levels for a power control device is described. This method may be employed in the potentiometer-controlled device shown in  FIGS. 1-4  or the pushbutton-controlled device depicted in  FIG. 5 . As described below, the following controls are present (and referred to in  FIG. 6  and &amp;) in potentiometer-controlled devices: (1) a potentiometer which sets output voltage; a (2) a calibration pushbutton (S 1 ); a forward/reverse phase switch is provided; and at least one visual indicator is present, such as the locator LED shown in  FIG. 3  (used to locate the device in a dark room). For the pushbutton-controlled devices disclosed herein the following controls are used in the calibration process: the up pushbutton that turns output voltage up; the down pushbutton that turns output voltage down; a calibration pushbutton as described above (Optionally either the up button or the down button can be used via the embedded firmware of the device); a forward/reverse phase switch is provided (if this feature is implemented in the device); a locator LED used to locate the device in a dark room; the bar graph display illustrating output voltage level; an LED illuminating the up pushbutton; and an LED illuminating the down pushbutton. 
         [0049]    Referring to  FIG. 6 , a flow chart illustrating a method for calibrating in accordance with the present invention is disclosed. Specifically, the procedure below is used to set the maximum output voltage for the potentiometer controlled devices depicted in  FIGS. 1-4 . In step  602 , the user is instructed to slide the potentiometer control  60 - 3  to its maximum level. The user is further instructed to press and hold the calibration button S 1  until the locator LED starts blinking. When this occurs, the manual trim mode is now initialized. In step  604 , the user taps the calibration pushbutton S 1  to cycle through the preset settings to get a feeling for the available light levels for the type of lighting load installed in his home. Once the maximum allowed setting is reached, the next tap causes the cycle to repeat. The user can repeat this cycle as many times as he likes. In step  606 , the user slides the potentiometer down to lock-in the desired maximum output voltage. In step  610 , the user can continue on and do the minimum calibration routine or he can end the calibration process. 
         [0050]    When the user calibrates the pushbutton device of  FIGS. 5A-B , the user presses the up pushbutton until the up and down LEDs start to flash or blink. Once he releases the up button, the device is in maximum calibration mode. As before, the user taps the calibration pushbutton (or the up button) to cycle through the preset settings for maximum output voltage. When the maximum allowed setting is reached, the next tap of the calibration button returns to the minimum allowed setting for maximum output voltage to repeat the cycle ( 604 ). In steps  606 - 608 , once the desired maximum output voltage is reached, the user can tap either the up or down pushbutton to lock in this setting. IF the up button is being used to calibrate, then a tap on the down button locks in the desired setting. 
         [0051]      FIG. 7  is a flow chart illustrating another method for calibrating the present invention. Specifically,  FIG. 7  illustrates the procedure for calibrating the minim setting. In step  702 , the user is instructed to slide the potentiometer control  60 - 3  to its minimum level. The user is further instructed to press and hold the calibration button S 1  until the locator LED starts blinking. When this occurs, the manual trim mode is now initialized. In step  704 , the user taps the calibration pushbutton S 1  to cycle through the preset settings to get a feeling for the available minimum light levels for the type of lighting load installed in his home. Once the maximum allowed setting is reached, the next tap causes the cycle to repeat. The user can repeat this cycle as many times as he likes until he settles on one he prefers. In step  706 , the user slides the potentiometer down to lock-in the desired minimum output voltage. In step  710 , the user can continue on and do the maximum calibration routine described above or he can end the calibration process. 
         [0052]    When the pushbutton device of  FIGS. 5A-B  is being calibrated, the user presses and holds the down pushbutton until the up and down LEDs start to flash. Manual trim mode is now initialized. Tap the CAL pushbutton to cycle through the preset settings for minimum output voltage. In step  704 , when the maximum allowed setting is reached, the next tap returns to the minimum allowed setting for minimum output voltage, and the cycle can be repeated. When the desired minimum output voltage is reached in steps  706 - 708 , the user taps either the UP or DOWN pushbutton to lock in this setting. In addition to locking in the minimum voltage level, a current sensor reading is established which is later used for determining whether the load is turned ON or OFF. 
         [0053]    In another embodiment of the invention, the bar graph display will light at max level before the up and down LEDs start to flash. If the down button is released at this point, the system will initiate a reset and the device will perform a manual calibration. 
         [0054]    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0055]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. 
         [0056]    The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
         [0057]    All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. 
         [0058]    No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0059]    It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.