Abstract:
A wall-mountable electrical timer for controlling the delivery of power from an AC power source to an electrical load, such as a lamp or a fan motor, includes: a timer adjustment actuator for selecting a predetermined time period of operation for the load; a toggle actuator for starting the timer, turning off the timer, and placing the timer in a bypass mode of operation; a vertical linear array of light-emitting diode visual indicators for indicating the length of a predetermined time period, the time remaining, and whether the timer is in the bypass mode; a controllably conductive device for regulating the delivery of power from the AC source to the load; and a controller for receiving inputs from the timer adjustment actuator and the toggle actuator, and for transmitting outputs to the visual indicators and the controllably conductive device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of commonly-assigned U.S. patent application Ser. No. 11/521,234, filed Sep. 13, 2006, now U.S. Pat. No. 7,579,717, issued Aug. 25, 2009, entitled WALL-MOUNTABLE TIMER FOR AN ELECTRICAL LOAD, the entire disclosure of which is hereby 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 source of alternating-current (AC) power, and more particularly, to a wall-mountable electronic timer for supplying power to a connected electrical load for a predetermined amount of time selectable by a user. 
     2. Description of the Related Art 
     In response to increasing awareness of energy conservation, many lighting control devices, such as dimmers, electronic timers, occupancy sensors, and daylight sensors, provide means for energy management of lighting loads in commercial and residential installations. Specifically, electronic timers operate to turn off a connected electrical load after a predetermined amount of time after the electrical load is turned on. Typically, the electronic timer includes a switching device, such as a relay, coupled in series electrical connection between an AC power source and the electrical load. Often, electronic timers are adapted to be mounted in electrical wall-boxes and are used in rooms, such as bathrooms, where a light or an exhaust fan may be turned on when the room is first in use, and left on after the room is no longer in use. 
     One prior art wall-mounted electronic timer is the Decora® electronic timer (e.g., part number 6515M) manufactured by Leviton Manufacturing Co., Inc. The electronic timer comprises four buttons, each corresponding to a different timeout period, e.g., two minutes, five minutes, ten minutes, and fifteen minutes. The buttons are each labeled with the corresponding timeout period. Actuating one of the four buttons turns a connected electrical load on and begins a countdown with the corresponding timeout period. After this period of time expires, the electrical load is turned off. A visual indicator, e.g., a light-emitting diode (LED), is located next to or in each of the buttons and illuminates to indicate how much time is left in the timeout period. For example, if there are nine minutes left until the lighting load is turned off, the visual indicator corresponding to the timeout period of ten minutes will be illuminated. During the last few minutes, e.g., the last two (2) minutes, of the timeout period, the visual indicator next to the bottom button blinks quickly. Further, the electronic timer has an off button located below the other four buttons. When the off button is actuated, the electrical load is immediately turned off. 
     Another wall-mounted prior art electronic timer is an electronic in-wall countdown timer (part number EI210) manufactured by Intermatic Incorporated. This electronic timer has a single button and four visual indicators located in a linear array on a front surface of the timer. Selectable timeout periods are listed beside the visual indicators and include ten minutes, fifteen minutes, thirty minutes, and sixty minutes. Repeatedly pressing the single button cycles the electronic timer between the four different timeout periods and causes the corresponding visual indicator to illuminate. Pressing and holding the single button causes the electronic timer to enter a bypass mode, i.e., the timing function is disabled and the timer will supply power until manually turned off. A fifth visual indicator, which is located below the other four visual indicators, is illuminated when the electronic timer is in the bypass mode. 
     However, typical prior art electronic timers have user interfaces that provide limited functionality, require a high level of cognition to operate, and have an unsatisfactory aesthetic appearance. For example, the Leviton electronic timer does not offer a bypass mode. With the Intermatic electronic timer, a user must repeatedly press the single button to turn an electrical load on with a long timeout period or to turn off the lighting load. Further, the functional buttons and visual indicators of typical prior art electronic timers are not attractive, especially in a residential installation. Also, prior art electronic timers typically look much different than other lighting controls, such as switches and dimmers, that might be ganged next to the electronic timer. 
     Some electronic dimmers, such as, for example, the Maestro® smart dimmer, have offered a user interface that allows access to many features, is easy to use, and provides an attractive appearance. The Maestro® dimmer is described in greater detail in U.S. Pat. No. 5,248,919, issued Sep. 29, 1993, entitled LIGHTING CONTROL DEVICE, the entire disclosure of which is hereby incorporated by reference. 
     Therefore, there is a need for an electronic timer having a simple user interface that provides an attractive appearance, is easy to use, and allows access to many features. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a wall-mountable load control device for controlling the power delivered to an electrical load from an AC power source comprises a controllably conductive device, a controller, a toggle actuator, a timer adjustment actuator, and a plurality of visual indicators. The controllably conductive device has a control input and is adapted to be coupled in series electrical connection between the source and the load for controlling the delivery of power to the load. The controller includes a timer and is operatively coupled to the control input of the controllably conductive device to control the conductivity of the controllably conductive device. The toggle actuator, the timer adjustment actuator, and the plurality of visual indicators are operatively coupled to the controller. The controller is operable to select a preset timeout period in response to an actuation of the timer adjustment actuator, cause the visual indicators to display a representation of the preset timeout period, control the conductivity of the controllably conductive device so as to enable the delivery of power to the load in response to a first actuation of the toggle actuator, start the timer, which is initialized with the preset timeout period, in response to the first actuation of the toggle actuator, and control the conductivity of the controllably conductive device so as to prevent the delivery of power to the load when the preset timeout period has elapsed. 
     According to a second embodiment of the present invention, a wall-mountable electrical timer for controlling the power delivered to an electrical load from an AC power source comprises a toggle actuator for enabling delivery of power to the load, a countdown timer, and a plurality of visual indicators. The countdown timer is adapted to begin counting down for a predetermined period of time in response to an actuation of the toggle actuator. The electrical timer disables the delivery of power to the load in response to the countdown timer having counted down for the predetermined period of time. The plurality of visual indicators are operable to provide an animated visual feedback to indicate that the countdown timer is counting down for the predetermined time period. 
     According to another embodiment of the present invention, a wall-mountable electrical timer for controlling the power delivered to an electrical load from an AC power source comprises a toggle actuator operable to cause the electrical timer to turn on and enter a countdown mode in response to a first actuation of the toggle actuator. The load is turned off after a predetermined time period after the load is turned on. The toggle actuator is further operable to cause the electrical timer to enter a bypass mode in response to a second actuation of the toggle actuator. The load is indefinitely turned on in the bypass mode. The electronic timer further comprises a plurality of visual indicators operable to illuminate with a first color when the electrical timer is in the countdown mode and to illuminate with a second color when the electrical timer is in the bypass mode. 
     In addition, the present invention provides a two-wire wall-mountable electrical timer, which is operable to control the power delivered to an electrical load from an AC power source and comprises a toggle actuator for turning on the load and a plurality of visual indicators. The electrical timer is operable to turn off the load after a preset timeout period after the load is turned on. The visual indicators are operable to provide a visual feedback when the load is off. 
     According to yet another aspect of the present invention, a wall-mountable electrical timer for controlling the power delivered to an electrical load from an AC power source comprises a toggle actuator. The electrical timer is responsive to a single-tap actuation of the toggle actuation to only: (1) turn the load on for a predetermined time period in response to a first single-tap actuation of the toggle actuator; and (2) turn the load off in response to a second subsequent single-tap actuation of the toggle actuator. 
     The present invention further provides a load control device for controlling the state of an electrical load. The load control device comprises a user-actuable timer adjustment means for selecting a preset timeout period between a minimum preset timeout period and a maximum preset timeout period, and a single control switch, independent of said user-actuable timer adjustment means, for generating control signals in response to an input from a user. The load control device further comprises control means operatively coupled to said timer adjustment means and said control switch for causing the load to: (i) change from an off state to a countdown state when said input from a user causes a first single switch closure of transitory duration, the load turned on in the countdown state; (ii) change from the countdown state to the off state after the preset timeout period after the load is changed from the off state to the countdown state; (iii) change from the off state to a bypass state when said input from a user causes multiple switch closures of transitory duration occurring within a predetermined time interval, the load turned on indefinitely in the bypass state; and (iv) change from one of the countdown state and the bypass state to the off state when said input from a user causes a second single switch closure of transitory duration subsequent to said first single switch closure of transitory duration. 
     In addition, the present invention provides a user interface for a wall-mountable electrical timer operable to control the power delivered to an electrical load from an AC power source. The user interface comprises a timer adjustment actuator for adjustment of a preset timeout period of the electrical timer; a plurality of visual indicators operable to display a representation of the preset timeout period, and a toggle actuator for enabling power to be delivered to the load. The electrical timer is operable to discontinue delivering power to the load after the preset timeout period has elapsed. 
     The present invention further provides a method of controlling the power delivered to an electrical load from an AC power source with a wall-mountable load control device. The method comprises the steps of: (1) selecting a preset timeout period using a timer adjustment actuator; (2) displaying a representation of the preset timeout period using a plurality of visual indicators; (3) actuating a toggle actuator; (4) enabling the delivery of power to the load in response to the step of actuating the toggle actuator; (5) initializing a timer with the preset timeout period; (6) starting the timer in response to the step of actuating the toggle actuator; and (7) discontinuing the delivery of power to the load when the preset timeout period has elapsed. 
     According to another embodiment of the present invention, a method of controlling the power delivered to an electrical load from an AC power source with a wall-mountable load control device comprises the steps of: (1) actuating a toggle actuator; (2) enabling the delivery of power to the load in response to the step of actuating the toggle actuator; (3) initializing a countdown timer with a predetermined time period; (4) starting the countdown timer in response to the step of actuating the toggle actuator; (5) discontinuing the delivery of power to the load when the predetermined time period has elapsed; and (6) providing an animated visual feedback to indicate that the countdown timer is counting down for the predetermined time period after the step of starting the countdown timer and prior to the step of discontinuing the delivery of power. 
     According to yet another aspect of the present invention, a method of controlling the power delivered to an electrical load from an AC power source with a wall-mountable load control device comprises the steps of: (1) actuating a toggle actuator; (2) enabling the delivery of power to the load in response to the step of actuating the toggle actuator; (3) discontinuing the delivery of power to the load when a preset timeout period has elapsed; and (4) providing a visual feedback before the step of enabling of the delivery of power to the load and after the step of discontinuing the delivery of power to the load. 
     The present invention further provides a method of controlling the power delivered to an electrical load from an AC power source with a wall-mountable load control device, which comprises the steps of: (1) actuating a toggle actuator; (2) enabling the delivery of power to the load in response to the step of actuating the toggle actuator; (3) discontinuing the delivery of power to the load when a preset timeout period has elapsed; (4) illuminating a visual indicator with a first color after the step of enabling the delivery of power to indicate a time period remaining until the step of discontinuing the delivery of power; (5) entering a bypass mode in which power is indefinitely provided to the load; and (6) illuminating a visual indicator with a second color after the step of entering the bypass mode. 
     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 an electronic timer according to the present invention; 
         FIG. 2  is a simplified block diagram of the electronic timer of  FIG. 1 ; 
         FIG. 3  is a flowchart of a timer procedure executed by a controller of the electronic timer of  FIG. 1 ; 
         FIGS. 4A and 4B  are flowcharts of a button routine of the timer procedure of  FIG. 3 ; and 
         FIG. 5  is a flowchart of a visual indicator procedure of the timer procedure of  FIG. 3 . 
     
    
    
     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. 1  is a front view of an electronic timer  100  according to the present invention. The electronic timer  100  comprises a faceplate  110  and a bezel  112  received in an opening of the faceplate. The electronic timer  100  further comprises a toggle actuator  114  and a timer adjustment actuator  116 , i.e., a rocker switch. Actuations of the toggle actuator  114  toggle, i.e., turn off and on, a connected electrical load, for example, a lighting load  204  ( FIG. 2 ) or a motor load, such as an exhaust fan. Actuations of an upper portion  116 A or a lower portion  116 B of the timer adjustment actuator  116  respectively increase or decrease a preset timeout period of the electronic timer  100 . The electronic timer  100  is operable to turn off the lighting load  204  at the end of the preset timeout period after the lighting load is turned on. The operation of the electronic timer  100  in response to actuations of the toggle actuator  114  and the upper and lower portions  116 A,  116 B of the timer adjustment actuator  116  is described in greater detail below. 
     A plurality of visual indicators  118 , e.g., light-emitting diodes (LEDs), are arranged in a vertical linear array on the left side of the bezel  112 . The visual indicators  118  are illuminated to represent the present value of the preset timeout period, or to display the amount of time left until the lighting load  204  is turned off. Labels  120  are engraved into the toggle actuator  114  next to the visual indicators  118  and may comprise numerical representations of the possible preset timeout periods that the associated visual indicator  118  represents. The electronic timer  100  may further comprise a timer icon  122  above the linear array of visual indicators  118 . 
     When the lighting load  204  is off, i.e., the electronic timer  100  is in an off mode or an off state, a user of the electronic timer may determine a desired amount of time for the preset timeout period, i.e., the amount of time that the lighting load will remain on after the lighting load is turned on. Accordingly, the user may actuate the upper and lower portions  116 A,  116 B of the timer adjustment actuator  116  to select one of a plurality of predetermined values of the timeout period, e.g., five (5) minutes, ten (10) minutes, fifteen (15) minutes, thirty (30) minutes, forty-five (45) minutes, and sixty (60) minutes, as shown in  FIG. 1 . As the user actuates the timer adjustment actuator  116 , the electronic timer  100  offers a pre-on visual feedback by illuminating one of the visual indicators  118  to designate the present value of the timeout period. For example, if the middle visual indicator  118  next to the text ‘30’ is illuminated, the timeout period will be thirty (30) minutes. Note that actuation of the timer adjustment actuator  116  does not cause the lighting load  204  to turn on. 
     After selecting the desired timeout period, the user can turn on the lighting load  204  by actuating the toggle actuator  114 . At this time, the electronic timer  100  enters a countdown mode and starts a countdown timer having an initial value equal to the desired timeout period. The electronic timer  100  illuminates the visual indicator  118  that corresponds to the desired timeout period. As the countdown timer decreases, the electronic timer  100  illuminates one of the visual indicators  118  to represent the amount of time left until the lighting load  204  is turned off. For example, if there are ten (10) minutes left in the countdown timer, the electronic timer  100  illuminates the visual indicator  118  adjacent the text ‘10’ on the toggle actuator  114 . 
     As the countdown timer is counting down to zero, the electronic timer  100  preferably provides an animated visual feedback, i.e., the electronic timer illuminates the visual indicators  118  to show that the electronic timer  100  is actively counting down to zero. According to a preferred embodiment of the present invention, the electronic timer  100  cycles in a downward fashion the visual indicators below the visual indicator which represents the remaining time. For example, if there are forty-five (45) minutes left in the countdown timer, the visual indictor  118  next to the label  120  of ‘45’ is illuminated constantly, while the four visual indicators below the constantly illuminated visual indicator are turned on and off in a decreasing fashion at a first rate (or “frequency”). Specifically, the ‘30’ visual indicator is turned on for one second and then off. Next, the ‘15’ visual indicator is turned on for one second and then off. Next, the ‘10’ visual indicator is turned on for one second and then off. Finally, the ‘5’ visual indicator is turned on for one second and then off. When there are five (5) minutes or less remaining in the countdown timer, the bottom visual indicator  118  blinks at a rate substantially equal to the first rate (i.e., on for one second and off for one second). Alternatively, other implementations of the animation of the visual indicators  118  may be used to illustrate that the countdown timer is actively counting down to zero minutes. 
     When there is a small amount of time left in the countdown timer, e.g., one (1) minute, the electronic timer  100  provides a pre-off visual feedback by blinking the bottom visual indicator quickly, i.e., at a second rate faster than the first rate (e.g., on for one-fourth second and off for one-fourth second), to warn the user that the lighting load  204  is about to turn off. 
     When the electronic timer  100  is in the countdown mode, the user may actuate the upper portion  116 A and the lower portion  116 B of the timer adjustment actuator  116 . The countdown timer instantly changes to the preset timeout period that is selected by the timer adjustment actuator  116  and continues to count down from the newly selected timeout period. If the user selects the bypass mode by highlighting the top visual indicator  118  while the countdown timer is enabled, the electronic timer  100  changes to the bypass mode and disables the countdown timer. 
     When the countdown timer expires, i.e., after the desired timeout period has elapsed, the electronic timer  100  turns the lighting load  204  off. Before the countdown timer expires and the electronic timer  100  turns the lighting load  204  off, the user may actuate the toggle button  114  to manually turn the lighting load  204  off. Therefore, the toggle button  114  provides an override to turn off the lighting load  204  before the countdown timer expires. 
     According to the present invention, when the lighting load  204  is turned off, the electronic timer  100  remembers the last timeout period that was selected by the user, i.e., the preset timeout period, such that the electronic timer will use the preset timeout period when the toggle actuator  114  is subsequently actuated. Accordingly, the visual indicator  118  representing the preset timeout period is dimly illuminated when the lighting load  204  is off. The user may decide to keep the preset timeout period and simply turn the lighting load  204  on with the selected preset timeout period. Or the user may decide to adjust the timeout period using the timer adjustment actuator  116  to a different timeout period and then turn the lighting load  204  on. Thus, the electronic timer  100  according to the present invention provides a one-button recall of the preset timeout period, i.e., one actuation of the toggle button  114  when the lighting load  204  is off starts the countdown timer with the preset timeout period. 
     The electronic timer  100  is also operable to enter a bypass mode in which the countdown timer is disabled and power is continuously (i.e., indefinitely) provided to the lighting load  204 . The electronic timer  100  enters the bypass mode in response to a number of possible actuations of the toggle button  114  and the timer adjustment actuator  116 . First, when the lighting load  204  is off, the user may use the timer adjustment actuator  116  to highlight the top visual indicator  118  in the linear array (next to the ‘On’ label  120  as shown in  FIG. 1 ), and subsequently press the toggle actuator  114  once to enter the bypass mode. When the lighting load  204  is on and the countdown timer is enabled, the user may use the timer adjustment actuator  116  to highlight the top visual indicator  118  and the electronic timer instantly changes to the bypass mode. Finally, the electronic timer  100  is operable to enter the bypass mode in response to a double-tap of the toggle actuator  114 , i.e., two transitory actuations of the toggle actuator  114  in quick succession. To differentiate between when the electronic timer  100  is in the bypass mode rather than counting down for the timeout period, the top visual indicator  118  is preferably a different color than the other visual indicators of the linear array, for example, the top visual indicator may be green, while the other visual indicators may be orange. 
     When the electronic timer  100  is in the bypass mode, the user may actuate the toggle button  114  once to turn off the lighting load  204 . Actuation of the lower portion  116 B of the timer adjustment actuator  116  (i.e., to highlight the visual indicator  118  for 60 minutes) causes the electronic timer  100  to exit the bypass mode and to begin the countdown timer from 60 minutes. While in the bypass mode, the electronic timer  100  does not change the state of the lighting load  204  in response to either an actuation of the upper portion  116 A of the timer adjustment actuator  116  or a double tap of the toggle button  114 . However, the electronic timer  100  will store the bypass mode as the preset timeout period if the upper portion  116 A of the time adjustment actuator  116  is pressed when the electronic timer is in the bypass mode. 
     When the user double-taps the toggle button  114  to enter the bypass mode, the electronic timer  100  does not save the bypass mode as the preset timeout period. Accordingly, when the user presses the toggle button  114  (to turn off the lighting load  204 ) and then subsequently presses the toggle button  114  again (to turn on the lighting load  204 ), the electronic timer  100  uses the previously-stored preset timeout period (which is not necessarily the bypass mode). 
       FIG. 2  is a simplified block diagram of the electronic timer  100  of the present invention. The electronic timer  100  is coupled in series electrical connection between an AC power source  202  and the lighting load  204 . The electronic timer  100  comprises a controllably conductive device  210  for control of the power delivered to the lighting load  204 . The controllably conductive device  210  may comprise a relay, or any suitable type of bidirectional semiconductor switch, such as, for example, a triac, a field-effect transistor (FET) in a rectifier bridge, or two FETs in anti-series connection. The controllably conductive device  210  includes a control input coupled to a drive circuit  212 . The input to the control input renders the controllably conductive device  210  conductive or non-conductive, which in turn controls the power supplied to the lighting load  204 . 
     The drive circuit  212  provides control inputs to the controllably conductive device  210  in response to command signals from a controller  214 . The controller  214  is preferably implemented as a microcontroller, but may be any suitable processing device, such as a programmable logic device (PLD), a microprocessor, or an application specific integrated circuit (ASIC). The controller  214  receives inputs from the toggle actuator  114  and the timer adjustment actuator  116  and controls the visual indicators  118 . The controller  214  is operable to turn on (i.e., enabling power to be delivered to) the lighting load  204 , and to turn off (discontinue delivering power to) the lighting load in response to the input receives from the toggle actuator  114 . The controller  214  preferably comprises a timer, e.g., a countdown timer, for counting down the preset timeout period. The controller  214  is also coupled to a memory  216  for storage of the present value of the preset timeout period. A power supply  218  generates a direct-current (DC) voltage V CC  for powering the controller  214 , the memory  216 , and other low-voltage circuitry of the electronic timer  100 . 
     A zero-crossing detector  220  determines the zero-crossings of the input AC waveform from the AC power supply  202 . 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 and end of each half-cycle. The zero-crossing information is provided as an input to the controller  214 . The controller  214  provides the control inputs to the drive circuit  212  to operate the controllably conductive device  210  (i.e., to provide or block voltage from the AC power supply  202  to the lighting load  204 ) at predetermined times relative to the zero-crossing points of the AC waveform using a phase-control dimming technique as is well known in the art. Accordingly, the controller  214  is operable to gradually apply power to the lighting load  204  and to gradually remove power from the lighting load (i.e. to “fade” the lighting load  204  between the on state and the off state), which is described in greater detail in the &#39;919 patent. 
       FIG. 3  is a flowchart of a timer procedure  300  executed by the controller  214  according to the present invention. Preferably, the timer procedure  300  is run periodically, e.g., as part of a main control loop. The controller  214  uses a countdown timer to determine when the preset timeout period expires to turn off the lighting load  204 .  FIGS. 4A and 4B  are flowcharts of a button routine  310 , which is the first step of the timer procedure  300 . The button routine  310  checks for and processes inputs from the toggle actuator  114  and the timer adjustment actuator  116 . 
     Referring to  FIG. 4A , the button routine  310  begins by checking for inputs from the toggle actuator  114  and the timer adjustment actuator  116  at step  410 . If a press of the upper portion  116 A of the timer adjustment actuator  116  has been detected at step  412 , a determination is made at step  414  as to whether the present value of the preset timeout period is at the highest value, i.e., the bypass mode as described in the preferred embodiment of the present invention. If the present value of the preset timeout period is at the highest value at step  414 , then the button routine  310  simply exits. If the present value of the preset timeout period is not at the highest value at step  414 , the value of the preset timeout period is increased to the next possible value at step  416 . For example, if the present value is 30 minutes, the value of the preset timeout period is increased to 45 minutes at step  416 . If the electronic timer  100  is in the bypass mode at step  418  (i.e., as selected at step  416 ), the countdown timer is disabled, i.e., stopped, at step  420 . If the lighting load  204  is off at step  422 , the appropriate visual indicator  118  is dimly illuminated at step  424 . For example, the middle visual indicator is dimly illuminated if the present value of the preset timeout period is 30 minutes. If the lighting load is on at step  422 , the appropriate visual indicator  118  is illuminated to a bright level at step  426 . The present value of the preset timeout period (i.e., 5-60 minutes or bypass mode) is stored in the memory  216  at step  428  and the button routine  310  exits. 
     If a press of the upper portion  116 A of the timer adjustment actuator  116  has not been detected at step  412 , a determination is made at step  430  as to whether a press of the lower portion  116 B of the timer adjustment actuator  116  has been detected. If a press of the lower portion  116 B of the timer adjustment actuator  116  has been detected at step  430  and the present value of the preset timeout period is not at the lowest value (i.e., 5 minutes) at step  432 , the present value of the preset timeout period is decreased to the next possible value at step  434 . If the lighting load  204  is on at step  435  and the preset timeout period is now 60 minutes (i.e., the electronic timer  100  was previously in the bypass mode) at step  436 , the countdown timer is enabled at step  438 . Next, the appropriate visual indicator  118  is illuminated either to a dim level at step  424  or to a bright level at step  426 . The present value of the preset timeout period is stored in the memory  216  at step  428 , and the button routine  310  exits. If the present value of the preset timeout period is at the lowest value at step  432 , the button routine  310  simply exits. 
     Referring to  FIG. 4B , if a press of the upper portion  116 A and the lower portion  116 B of the timer adjustment actuator  116  have not been detected, a determination is made at step  440  as to whether a single tap of the toggle button  114  has occurred. If a single tap of the toggle button  114  has been detected at step  440  and the lighting load  204  is on at step  442 , the lighting load is turned off at step  444 . The countdown timer is stopped, i.e., disabled, at step  446  and the visual indicator  118  representing the present value of the preset timeout period is dimly lit at step  448 . If the lighting load is not on at step  442  and the top visual indicator  118  is not illuminated (i.e., the bypass mode is not selected) at step  450 , the lighting load  204  is turned on at step  452  and the countdown timer is started, i.e., enabled, at step  454 . 
     If the top visual indicator  118  is illuminated (i.e., the bypass mode is selected) at step  450 , the lighting load  204  is turned on at step  456  and the countdown timer is disabled at step  458 . If a single tap of the toggle button  114  is not detected at step  440 , but a double tap of the toggle button  114  is detected at step  460 , the electronic timer  100  enters the bypass mode by illuminating the top visual indicator  118  at step  462 , turning on the lighting load  204  at step  456 , and disabling the countdown timer at step  458 . 
     Referring back to  FIG. 3 , once the button routine  310  is completed, a determination is made at step  312  as to whether the countdown timer is enabled, i.e., counting down for the preset timeout period. If not, the timer procedure  300  simply exits. Accordingly, when the lighting load  204  is off and when the electronic timer  100  is in the bypass mode, the controller  214  will periodically execute only the button procedure  310 . 
     If the countdown timer is enabled at step  312  and the countdown timer is greater than zero (0) minutes, i.e., has not expired, at step  314 , a visual indicator routine  316  is executed.  FIG. 5  is a flowchart of the visual indicator routine  316 . Referring to  FIG. 5 , if the countdown timer is less than one (1) minute at step  510 , the controller  214  blinks the first visual indicator  118 , i.e., the bottom visual indicator in the linear array, at step  512 , and then exits the visual indicator routine  316 . Preferably, the first visual indicator  118  is blinked at the second rate, which is greater than the first rate, at step  512 . If the countdown timer is less than five (5) minutes at step  514 , the controller  214  blinks the first visual indicator  118  at the first rate at step  516 . If the countdown timer is less than ten (10) minutes at step  518 , less than fifteen (15) minutes at step  522 , less than thirty (30) minutes at step  526 , or less than forty-five (45) minutes at step  530 , the controller constantly illuminates, respectively, the second visual indicator at step  520 , the third visual indicator at step  524 , the fourth visual indicator at step  528 , or the fifth visual indicator at step  532 . In this manner, the illuminated one of the linear array of visual indicators  118  decreases as the countdown timer decreases, and the bottom visual indicator is blinked during the last minute before the countdown timer expires. 
     After steps  520 ,  524 ,  528 ,  530 , and  532 , the controller  214  animates the lower visual indicators  118  at step  534  to illustrate that the countdown timer is actively counting down. Accordingly, the controller  214  may execute a routine during step  534 , such that the visual indicators  118  in the linear array below the constantly illuminated visual indicator (i.e., illuminated in steps  520 ,  524 ,  528 , and  532 ) are cycled in a decreasing fashion. Alternatively, another animation could be implemented. For example, the visual indicators  118  in the linear array below the constantly illuminated visual indicator could each be turned on (rather than cycled) one-by-one in a decreasing fashion. Such animation routines are easily programmed by one skilled in the art and are not discussed in greater detail herein. 
     Referring back to  FIG. 3 , if the countdown timer has expired, i.e., is less than or equal to zero (0) minutes, at step  314 , the controller  214  turns off the lighting load  204  at step  318 . At step  320 , the countdown timer is disabled. The visual indicator  118  representative of the preset timeout period is dimly illuminated at step  322  and the timer procedure  300  exits. 
     The bypass mode may be disabled, for example, by using an advanced programming procedure of the electronic timer  100 . Accordingly, when the bypass mode is disabled, the user cannot cause the electronic timer  100  to enter the bypass mode by using the toggle button  114  or the timer adjustment actuator  116 . Further, the electronic timer  100  may be programmed to operate with a “locked” or “protected” preset timeout period, i.e., the preset timeout period cannot be changed, via the advanced programming mode. An exemplary advanced programming procedure is described in greater detail in U.S. patent application Ser. No. 10/892,510, filed Jul. 15, 2004, entitled PROGRAMMABLE WALLBOX DIMMER, the entire disclosure of which is hereby incorporated by reference. 
     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.