Abstract:
A system for displaying a temperature of a refrigerator compartment including at least one temperature sensor is provided that emulates the function and behavior of a thermostat to control and display refrigerator compartment temperature in a simple and intuitive manner. The system includes a controller including a processor and a memory and operatively coupled to the temperature sensor. A human machine interface board includes a display and is coupled to the controller and configured for receiving user input of a refrigerator compartment setting. The controller is configured to accept a set temperature of the at least one compartment, monitor actual temperature of the compartment; and display a damped temperature value based on operating conditions of the refrigerator.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to refrigerators and, more particularly, to an apparatus and method for displaying a temperature of a refrigerator compartment.  
           [0002]    Known refrigeration appliances typically include one or more refrigeration compartments for the storage of fresh food and for frozen food storage. Conventionally, temperature settings for fresh food compartments and freezer compartments are adjustable through manipulation of an electromechanical mechanism, such as a dial or sliding switch. Depending on a user selected position of the electromechanical mechanism or mechanisms, refrigerator controls regulate the temperature of the respective refrigerator compartments to a temperature corresponding to the temperature position. However, because with these systems there is no apparent way to determine an actual temperature of the departments, operating temperature settings are often determined by user trial and error. In addition, excessive deviation from selected temperature settings indicative of a refrigerator malfunction are difficult to detect.  
           [0003]    The proliferation of electronic controls in appliances offer enhanced control schemes for appliances, including, for example, feedback displays to the user indicative of temperature settings. Thus, the displays provide visual confirmation of selected settings as well as confirmation that selected temperatures are being maintained. However, electronic controls can sometimes be confusing to, operate, and further can mislead users to believe that the appliance is not operating properly because the system does not respond like conventional electromechanical systems. Thus, for example, indication of rapid temperature changes or apparently unstable temperature displays may cause a user to place a service call when the refrigerator is otherwise working normally. As another example, when a new temperature setting does not produce immediate change in refrigerator behavior, (as will be the case when the new temperature setting is below the actual temperature of the compartment) a user may believe that the refrigerator is not working.  
           [0004]    It would be desirable to provide an easy to use electronic control system for a refrigerator that includes temperature displays while avoiding behavior inconsistent with conventional systems.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    In an exemplary embodiment of the invention, a system for displaying a temperature of a refrigerator compartment including at least one temperature sensor is provided that emulates the function and behavior of a thermostat to control and display refrigerator compartment temperature in a simple and intuitive manner. The system includes a controller including a processor and a memory, and is operatively coupled to the temperature sensor. A human machine interface board includes a display and is coupled to the controller and configured for receiving user input of a refrigerator compartment setting. The controller is configured to accept a set temperature of the compartment, monitor an actual temperature of the compartment; and display a damped temperature value based on operating conditions of the refrigerator.  
           [0006]    In one embodiment, the controller damps the temperature value for one of several fixed time constants depending on a mode of operation of the refrigerator and conditions in the refrigerator compartment. Alternatively, the controller calculates a damped temperature value based upon a rolling average of actual temperature and the set temperature, or upon a rolling average of actual temperature and a current display register value in the controller memory. Therefore, displayed temperature values are adjusted in a stable manner.  
           [0007]    Moreover, the controller is configured to respond appropriately to user settings where a response is not otherwise necessary to confirm to the user that the system is operating. Thus, for example, if a temperature setting is lowered to a point above the operating temperature of the compartment, fans are energized briefly in accordance with user expectations that the adjusted setting should cause the fans to be turned on. User confusion and possible associated service calls due to a non-responsive refrigerator is therefore avoided. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a perspective view of a refrigerator;  
         [0009]    [0009]FIG. 2 is a block diagram of a refrigerator controller in accordance with one embodiment of the present invention;  
         [0010]    [0010]FIG. 3 is a block diagram of the main control board shown in FIG. 2;  
         [0011]    [0011]FIG. 4 is a block diagram of the main control board shown in FIG. 2;  
         [0012]    [0012]FIG. 5 illustrates an interface for a refrigerator the refrigerator shown in FIG. 1;  
         [0013]    [0013]FIG. 6 illustrates a second interface for the refrigerator shown in FIG. 1;  
         [0014]    [0014]FIG. 7 illustrates a second embodiment of an interface for a refrigerator;  
         [0015]    [0015]FIG. 8 is a state diagram for fresh food temperature display; and  
         [0016]    [0016]FIG. 9 is a state diagram for freezer temperature display; 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    [0017]FIG. 1 illustrates a side-by-side refrigerator  100  in which the present invention may be practiced. It is recognized, however, that the benefits of the present invention apply to other types of refrigerators, freezers, and refrigeration appliances wherein frost free operation is desirable. Consequently, the description set forth herein is for illustrative purposes only and is not intended to limit the invention in any aspect.  
         [0018]    Refrigerator  100  includes a fresh food storage compartment  102  and a freezer storage compartment  104 . Freezer compartment  104  and fresh food compartment  102  are arranged side-by-side. A side-by-side refrigerator such as refrigerator  100  is commercially available from General Electric Company, Appliance Park, Louisville, Ky. 40225.  
         [0019]    Refrigerator  100  includes an outer case  106  and inner liners  108  and  110 . A space between case  106  and liners  108  and  110 , and between liners  108  and  110 , is filled with foamed-in-place insulation. Outer case  106  normally is formed by folding a sheet of a suitable material, such as pre-painted steel, into an inverted U-shape to form top and side walls of case. A bottom wall of case  106  normally is formed separately and attached to the case side walls and to a bottom frame that provides support for refrigerator  100 . Inner liners  108  and  110  are molded from a suitable plastic material to form freezer compartment  104  and fresh food compartment  102 , respectively. Alternatively, liners  108 ,  110  may be formed by bending and welding a sheet of a suitable metal, such as steel. The illustrative embodiment includes two separate liners  108 ,  110  as it is a relatively large capacity unit and separate liners add strength and are easier to maintain within manufacturing tolerances. In smaller refrigerators, a single liner is formed and a mullion spans between opposite sides of the liner to divide it into a freezer compartment and a fresh food compartment.  
         [0020]    A breaker strip  112  extends between a case front flange and outer front edges of liners. Breaker strip  112  is formed from a suitable resilient material, such as an extruded acrylo-butadiene-styrene based material (commonly referred to as ABS).  
         [0021]    The insulation in the space between liners  108 ,  110  is covered by another strip of suitable resilient material, which also commonly is referred to as a mullion  114 . Mullion  114  also preferably is formed of an extruded ABS material. It will be understood that in a refrigerator with separate mullion dividing a unitary liner into a freezer and a fresh food compartment, a front face member of mullion corresponds to mullion  114 . Breaker strip  112  and mullion  114  form a front face, and extend completely around inner peripheral edges of case  106  and vertically between liners  108 ,  110 . Mullion  114 , insulation between compartments, and a spaced wall of liners separating compartments, sometimes are collectively referred to herein as a center mullion wall  116 .  
         [0022]    Shelves  118  and slide-out drawers  120  normally are provided in fresh food compartment  102  to support items being stored therein. A bottom drawer or pan  122  partly forms a quick chill and thaw system (not shown) and selectively controlled, together with other refrigerator features, by a microprocessor (not shown in FIG. 1) according to user preference via manipulation of a control interface  124  mounted in an upper region of fresh food storage compartment  102  and coupled to the microprocessor. A shelf  126  and wire baskets  128  are also provided in freezer compartment  104 . In addition, an ice maker  130  may be provided in freezer compartment  104 .  
         [0023]    A freezer door  132  and a fresh food door  134  close access openings to fresh food and freezer compartments  102 ,  104 , respectively. Each door  132 ,  134  is mounted by a top hinge  136  and a bottom hinge (not shown) to rotate about its outer vertical edge between an open position, as shown in FIG. 1, and a closed position (not shown) closing the associated storage compartment. Freezer door  132  includes a plurality of storage shelves  138  and a sealing gasket  140 , and fresh food door  134  also includes a plurality of storage shelves  142  and a sealing gasket  144 .  
         [0024]    In accordance with known refrigerators, refrigerator  100  also includes a machinery compartment (not shown) that at least partially contains components for executing a known vapor compression cycle for cooling air. The components include a compressor (not shown in FIG. 1), a condenser (not shown in FIG. 1), an expansion device (not shown in FIG. 1), and an evaporator (not shown in FIG. 1) connected in series and charged with a refrigerant. The evaporator is a type of heat exchanger which transfers heat from air passing over the evaporator to a refrigerant flowing through the evaporator, thereby causing the refrigerant to vaporize. The cooled air is used to refrigerate one or more refrigerator or freezer compartments via fans (not shown in FIG. 1). Collectively, the vapor compression cycle components in a refrigeration circuit, associated fans, and associated compartments are referred to herein as a sealed system. The construction of the sealed system is well known and therefore not described in detail herein, and the sealed system is operable to force cold air through the refrigerator and to maintain selected temperatures. Compartment temperatures are set by user manipulation of interface  124  and compartment temperature feedback is displayed to the user according to the control scheme set forth below.  
         [0025]    [0025]FIG. 2 illustrates a controller  160  in accordance with one embodiment of the present invention. Controller  160  can be used, for example, in refrigerators, freezers and combinations thereof, such as, for example side-by-side refrigerator  100  (shown in FIG. 1).  
         [0026]    Controller  160  includes a diagnostic port  162  and a human machine interface (HMI) board  164  coupled to a main control board  166  by an asynchronous interprocessor communications bus  168 . An analog to digital converter (“A/D converter”)  170  is coupled to main control board  166 . A/D converter  170  converts analog signals from a plurality of sensors including one or more fresh food compartment temperature sensors  172 , a quick chill/thaw feature pan (i.e., pan  122  shown in FIG. 1) temperature sensors  174 , freezer temperature sensors  176 , external temperature sensors (not shown in FIG. 2), and evaporator temperature sensors  178  into digital signals for processing by main control board  166 .  
         [0027]    In an alternative embodiment (not shown), A/D converter  170  digitizes other input functions (not shown), such as a power supply current and voltage, brownout detection, compressor cycle adjustment, analog time and delay inputs (both use based and sensor based) where the analog input is coupled to an auxiliary device (e.g., clock or finger pressure activated switch), analog pressure sensing of the compressor sealed system for diagnostics and power/energy optimization. Further input functions include external communication via IR detectors or sound detectors, HMI display dimming based on ambient light, adjustment of the refrigerator to react to food loading and changing the air flow/pressure accordingly to ensure food load cooling or heating as desired, and altitude adjustment to ensure even food load cooling and enhance pull-down rate of various altitudes by changing fan speed and varying air flow.  
         [0028]    Digital input and relay outputs correspond to, but are not limited to, a condenser fan speed  180 , an evaporator fan speed  182 , a crusher solenoid  184 , an auger motor  186 , personality inputs  188 , a water dispenser valve  190 , encoders  192  for set points, a compressor control  194 , a defrost heater  196 , a door detector  198 , a mullion damper  200 , feature pan air handler dampers  202 ,  204 , and a quick chill/thaw feature pan heater  206 . Main control board  166  also is coupled to a pulse width modulator  208  or controlling the operating speed of a condenser fan  210 , a fresh food compartment fan  212 , an evaporator fan  214 , and a quick chill system feature pan fan  216 .  
         [0029]    [0029]FIGS. 3 and 4 are more detailed block diagrams of main control board  166 . As shown in FIGS. 3 and 4, main control board  166  includes a processor  230 . Processor  230  performs temperature adjustments/dispenser communication, AC device control, signal conditioning, microprocessor hardware watchdog, and EEPROM read/write functions. In addition, processor executes many control algorithms including sealed system control, evaporator fan control, defrost control, feature pan control, fresh food fan control, stepper motor damper control, water valve control, auger motor control, cube/crush solenoid control, timer control, and self-test operations.  
         [0030]    Processor  230  is coupled to a power supply  232  which receives an AC power signal from a line conditioning unit  234 . Line conditioning unit  234  filters a line voltage which is, for example, a 90-265 Volts AC, 50/60 Hz signal. Processor  230  also is coupled to an EEPROM  236  and a clock circuit  238 .  
         [0031]    A door switch input sensor  240  is coupled to fresh food and freezer door switches  242 , and senses a door switch state. A signal is supplied from door switch input sensor  240  to processor  230 , in digital form, indicative of the door switch state. Fresh food thermistors  244 , a freezer thermistor  246 , at least one evaporator thermistor  248 , a feature pan thermistor  250 , and an ambient thermistor  252  are coupled to processor  230  via a sensor signal conditioner  254 . Conditioner  254  receives a multiplex control signal from processor  230  and provides analog signals to processor  230  representative of the respective sensed temperatures. Processor  230  also is coupled to a dispenser board  256  and a temperature adjustment board  258  via a serial communications link  260 . Conditioner  254  also calibrates the above-described thermistors  244 ,  246 ,  248 ,  250 , and  252 .  
         [0032]    Processor  230  provides control outputs to a DC fan motor control  262 , a DC stepper motor control  264 , a DC motor control  266 , and a relay watchdog  268 . Watchdog  268  is coupled to an AC device controller  270  that provides power to AC loads, such as to water valve  190 , cube/crush solenoid  184 , a compressor  272 , auger motor  186 , a feature pan heater  206 , and defrost heater  196 . DC fan motor control  266  is coupled to evaporator fan  214 , condenser fan  210 , fresh food fan  212 , and feature pan fan  216 . DC stepper motor control  266  is coupled to mullion damper  200 , and DC motor control  266  is coupled to one of more sealed system dampers. These functions are performed under the control of firmware implemented as small independent state machines.  
         [0033]    Control interface  124  (shown in FIG. 1) is split into one or more human machine interface (HMI) boards including displays. For example, FIG. 5 illustrates an HMI board  300  for a refrigerator including dispensers. Board  300  includes a plurality of touch sensitive keys or buttons  302  for selection of various options, and accompanying LED&#39;s  304  to indicate selection of an option.  
         [0034]    [0034]FIG. 6 illustrates an exemplary HMI board  320  for a refrigerator including electronic cold control, such as refrigerator  100  (shown in FIG. 1). Board  320  also includes a plurality of touch sensitive keys or buttons  322  including LEDs to indicate activation of a selected control feature, a fresh food compartment actual temperature display  324 , a freezer compartment actual temperature display  326 , and respective warmer/up slew keys  328  and colder/down slew keys  330  for adjusting temperature settings of fresh food compartment  102  and freezer compartment  104  (shown in FIG. 1).  
         [0035]    [0035]FIG. 7 illustrates yet another embodiment of a cold control HMI board  340  including a plurality of touch sensitive keys or buttons  342  including LEDs  344  to indicate activation of a selected control feature, temperature zone displays  346  for fresh food and freezer compartments, and slew keys  348  for adjusting temperature settings.  
         [0036]    The temperature setting system is substantially the same for each HMI user interface  320 ,  340 . When fresh food door  134  (shown in FIG. 1) is closed, the HMI displays are off. When fresh food door  134  is opened, the displays turn on and operate according to the following scheme.  
         [0037]    Referring to FIG. 6, the freezer compartment temperature is set in one embodiment as follows. In normal operation the current freezer temperature is displayed. When one of the freezer slew keys  326  is depressed, the LED next to “SET” (located just below slew keys  326  in FIG. 6) is illuminated, and controller  160  (shown in FIGS.  2 - 4 ) waits for operator input. Thereafter, for each time the freezer colder/slew-down key  330  is depressed, the display value on freezer temperature display  326  will decrement by one, and for each time the user presses the warmer/slew-up key  328  he display value on freezer temperature display  326  will increment by one. Thus, the user may increase or decrease the freezer set temperature using the freezer slew keys  328  and  330  on board  320 .  
         [0038]    Once the SET LED is illuminated, if freezer slew keys  328 ,  330  are not pressed within a few seconds, such as one to ten seconds, the SET LED will turn off and the current freezer set temperature will be maintained. After this period the user will be unable to change the freezer setting unless one of freezer slew keys  328 ,  330  is again pressed to re-illuminate the SET LED.  
         [0039]    If the freezer temperature is set to a predetermined lower temperature outside of a standard operating range of freezer compartment, such as 7° F. in an exemplary embodiment, both fresh food and freezer displays  324 ,  326  will display an “off” indicator, and controller  160  shuts down the sealed system. The sealed system may be reactivated by pressing the freezer colder/slew-down  330  key so that the freezer temperature display is a predetermined temperature within the standard operating range, such as 6° F. or lower.  
         [0040]    In one embodiment, freezer temperature may be set only in a range between −6° F. and 6° F. In alternative embodiments, other setting increments and ranges are contemplated in lieu of the exemplary embodiment described above.  
         [0041]    In a further alternative embodiment, such as that shown in FIG. 7, temperature indicators other than actual temperature are displayed, such as a system selectively operable at a plurality of levels, e.g., level “1” through level “9” where one of the extremes, e.g., level “1” is a warmest setting and the other extreme, e.g., level “9” is a coldest setting. The settings are incremented or decremented accordingly between the two extremes on temperature zone or level displays  346  by pressing applicable warmer/slew-up or colder/slew-down keys  348 . The freezer temperature is set using board  340  substantially as described above.  
         [0042]    Similarly, and referring back to FIG. 6, fresh food compartment temperature is set in one embodiment as follows. In normal operation, the current fresh food temperature is displayed. When one of the fresh food slew keys  328 ,  330  is depressed, the LED next to “SET” (located just below refrigerator slew keys  328 ,  330  in FIG. 6) is illuminated and controller  160  waits for operator input. The displayed value on refrigerator temperature display  324  will decrement by one for each time the user presses the colder/slew-down key  330 , and the display value on refrigerator temperature display  324  will increment by one for each time the user presses the warmer/slew-up key  328 .  
         [0043]    Once the SET LED is illuminated, if the fresh food compartment slew keys  328 ,  330  are not pressed within a predetermined time interval, such as one to ten seconds in an exemplary embodiment, the SET LED will turn off and the current fresh food set temperature will be maintained. After this period the user will be unable to change the fresh food compartment setting unless one of slew keys  328 ,  330  is again pressed to re-illuminate the SET LED.  
         [0044]    If the user attempts to set the fresh food temperature above a normal operating range, such as 46° F., both fresh food and freezer displays  322 ,  324  will display an “off” indicator, and controller  160  shuts down the sealed system. The sealed system may be reactivated by pressing the colder/slew-down key so that the set fresh food compartment set temperature is within the normal operating range, such as 45° F. or lower.  
         [0045]    In one embodiment, freezer temperature may be set only in a range between 34° F. and 45° F. In alternative embodiments, other setting increments and ranges are contemplated in lieu of the exemplary embodiment described above.  
         [0046]    In a further alternative embodiment, such as that shown in FIG. 7, temperature indicators other than actual temperature are displayed, such as a system selectively operable at a plurality of levels, e.g., level “1” through level “9” where one of the extremes, e.g., level “1” is a warmest setting and the other extreme, e.g., level “9” is a coldest setting. The settings are incremented or decremented accordingly between the two extremes on temperature zone or level displays  346  by pressing the applicable warmer/slew-up or colder/slew-down key  348 , and the fresh food temperature may be set as described above.  
         [0047]    Once fresh food compartment and freezer compartment temperatures are set, actual temperatures (for the embodiment shown in FIG. 6) or temperature levels (for the embodiment shown in FIG. 7) are monitored and displayed to the user. To avoid undue changes in temperature displays during various operational modes of the refrigerator system that may mislead a user to believe that a malfunction has occurred, the behavior of the temperature display is altered in different operational modes of refrigerator  100  to better match refrigerator system behavior with consumer expectations. In one embodiment, for ease of consumer use control boards  320 ,  340  and temperature displays  324 ,  326 ,  246  are configured to emulate the operation of a thermostat.  
         [0048]    Normal Operation Display  
         [0049]    For temperature settings, and as further described below, a normal operation mode is defined as closed door operation after a first state change cycle, i.e., a change of state from “warm” to “cold” or vice versa, due to a door opening or defrost operation. Under normal operating conditions, HMI board  320  (shown in FIG. 6) displays an actual average temperature of fresh food and freezer compartments  102 ,  104 , except that HMI board  320  displays the set temperature for fresh food and freezer compartments  102 ,  104  while actual temperature fresh food is and freezer compartments  102 ,  104  is within a dead band for the freezer or the fresh food compartments.  
         [0050]    Outside the dead band, however, HMI board  320  displays an actual average temperature for fresh food and freezer compartments  102 ,  104 . For example, for a 37° F. fresh food temperature setting and a dead band of +/−2° F., actual and displayed temperature is as follows.  
                                                                                   Actual   34   34.5   35   36   37   38   39   39.5   40   40.5   41   42       Temp.       Display   35   36   37   37   37   37   37   38   39   40   41   42       Temp.                  
 
         [0051]    Thus, in accordance with user expectations, actual temperature displays  324 ,  326  are not changed when actual temperature is within the dead band, and the displayed temperature display quickly approaches the actual temperature when actual temperatures are outside the dead band. Freezer settings are also displayed similarly within and outside a predetermined dead band. The temperature display is also damped, for example, by a 30 second time constant if the actual temperature is above the set temperature and, for example, by a 20 second time constant if the actual temperature is below the set temperature.  
         [0052]    Door Open Display  
         [0053]    A door open operation mode is defined as time while a door is open and while the door is closed after a door open event until the sealed system has cycled once (changed state from warm-to-cold, or cold-to-warm once), excluding a door open operation during a defrost event. During door open events, food temperature is slowly and exponentially increasing. After door open events, temperature sensors in the refrigerator compartments determine the overall operation and this is to be matched by the display.  
         [0054]    Fresh Food Display  
         [0055]    During door open operation, temperature display for the fresh food compartment is modified as follows depending on actual compartment temperature, the set temperature, and whether actual temperature is rising or falling.  
         [0056]    When actual fresh food compartment temperature is above the set temperature and is rising, the fresh food temperature display damping constant is activated and dependent upon a difference between the actual and set temperature. In an exemplary embodiment, the damping constant is five minutes for a set temperature versus actual temperature difference of, for example, 2° F. to 4° F., ten minutes for a set temperature versus actual temperature difference of, for example, 4° F. to 7° F., and is, for example, twenty minutes for a set temperature versus actual temperature difference of, for example, greater than 7° F.  
         [0057]    When actual fresh food compartment temperature is above the set temperature and falling, the fresh food temperature display damping delay constant is, for example, three minutes.  
         [0058]    When actual fresh food compartment temperature is below the set temperature and rising, the fresh food temperature display damping delay constant is, for example, three minutes.  
         [0059]    When actual fresh food compartment temperature is below the set temperature and falling, the damping delay constant is, for example, five minutes for a set temperature versus actual temperature difference of, for example, 2° F. to 4° F., ten minutes for a set temperature versus actual temperature difference of, for example, 4° F. to 7° F., and is, for example, 20 minutes for a set temperature versus actual temperature difference of, for example, greater than 7° F.  
         [0060]    In alternative embodiments, other settings and ranges are contemplated in lieu of the exemplary embodiment described above.  
         [0061]    Freezer Display  
         [0062]    During door open operation, the temperature display for the freezer compartment is modified as follows depending on actual freezer compartment temperature, the set freezer temperature, and whether actual temperature is rising or falling.  
         [0063]    When actual freezer compartment temperature is above the set temperature and rising, the damping delay constant is, for example, five minutes for a set temperature versus actual temperature difference of, for example, 2° F. to 8° F., ten minutes for a set temperature versus actual temperature difference of, for example, 8° F. to 15° F., and is, for example, twenty minutes for a set temperature versus actual temperature difference of greater than 15° F.  
         [0064]    When actual freezer compartment temperature is above the set temperature and falling, the damping delay constant is, for example, three minutes.  
         [0065]    When actual freezer compartment temperature is below the set temperature and increasing, the damping delay constant is, for example, three minutes.  
         [0066]    When actual freezer compartment temperature is below the set temperature and falling, the damping delay constant is, for example, five minutes for a set temperature versus actual temperature difference of, for example, 2° F. to 8° F., ten minutes for a set temperature versus actual temperature difference of, for example, 8° F. to 15° F., and is, for example, twenty minutes for a set temperature versus actual temperature difference of, for example, greater than 15° F.  
         [0067]    In alternative embodiments, other settings and ranges are contemplated in lieu of the exemplary embodiment described above.  
         [0068]    Defrost Mode Display  
         [0069]    A defrost operation mode is defined as a pre-chill interval, a defrost heating interval and a first cycle interval. During a defrost operation, freezer temperature display  326  shows the freezer set temperature plus, for example, 1° F. while the sealed system is on and shows the set temperature while the sealed system is off, and fresh food display  324  shows the set temperature. Thus, defrost operations will not be apparent to the user.  
         [0070]    Defrost Mode, Door Open Display  
         [0071]    A mode of defrost operation while a door  132 ,  134  (shown in FIG. 1) is open is defined as an elapsed time a door is open while in the defrost operation. Freezer display  326  shows the set temperature when the actual freezer temperature is below the set temperature, and otherwise it displays a damped actual temperature with a delay constant of twenty minutes. Fresh food display  324  shows the set temperature when the fresh food temperature is below the set temperature, and otherwise it displays a damped actual temperature with a delay constant of ten minutes.  
         [0072]    User Temperature Change Display  
         [0073]    A user change temperature mode is defined as a time from which the user changes a set temperature for either the fresh food or freezer compartment until a first sealed system cycle is completed. If the actual temperature is within a dead band and the new user set temperature also is within the dead band, one or more sealed system fans are turned on for a minimum amount of time when the user has lowered the set temperature so that the sealed system appears to respond to the new user setting as a user might expect.  
         [0074]    If the actual temperature is within the dead band and the new user set temperature is within the dead band, no load is activated if the set temperature is increased. If the actual temperature is within the dead band and the new user set temperature is outside the dead band, then action is taken as in normal operation.  
         [0075]    Referring now specifically to FIGS. 8 and 9, FIG. 8 is a state diagram  380  for an alternative embodiment of a fresh food temperature display scheme, and FIG. 9 is a state diagram  400  of an alternative embodiment of a freezer temperature display scheme. It may be seen from FIGS. 8 and 9 that several time constants are expressed as fractional values (assuming time is in hour increments) to calculate weighted averages or damped temperature values to display based on set points, average compartment temperatures and the most current display register value (stored in a display register in controller  160  (shown in FIGS.  2 - 4 ). These time constants are considered, in an exemplary embodiment, as variables that may be changed to provide different response times for different refrigeration appliances. Alternatively, the time constants are set to the same value for different refrigerators. A one minute tick (shown in FIGS. 8 and 9) can also be adjusted in the event that a quicker response time is required for a particular system.  
         [0076]    An algorithm embodied in state diagrams  698 ,  700  can be expressed by the rules below for different refrigerator modes and door open events.  
                                                                                                                                 One Minute Tick                Request Filtered Avg_FF_Temp   /*FF is fresh food*/           Request Filtered FZ_Temp   /*FZ is freezer*/           Request Last SS On Time   /*SS is sealed system*/                SS_Buff = SSOnTime * 1 / (60 * 24) + SS_Buf * (1 − (1 / (60 *24)))           /* SS_Buf is a rolling average of the SS on time over the last 24           hours*/           Request Prechill, Dwell and Defrost State            On Fresh Food Door Open To Close                Setup and Start FF_Timer for Duration of SS_Buf           /* Set up a decay time for the display to drop back toward the set           point*/            On Freezer Door Open To Close                Setup and Start FZ_Timer for Duration of SS_Buf           /* Set up a decay time for the display to drop back toward the set           point*/            If (FFDoor = Open) Display_Register_FF = Avg_FF_Temp * (1 / 7) +       Display_Register_FF * (1 − 1 / 7)                /*Display_Register receives damped value*/           Else if (FF_Timer = Running) Display_Register_FF = FF_Set_Point * (1 / 7)           + Display_Register_FF * (1 − 1 / 7)           Else Display_Register_FF = Avg_FF_Temp * (1 / 60) + Display_Register_FF           * (1 − 1/60))            If (FZDoor = Open) Display_Register_FZ = FZ_Temp * (1 / 7) +       Display_Register_FZ * (1 − 1 / 7)                Else if (FZ_Timer = Running) Display_Register_FZ = FZ_Set_Point * (1 / 7)           + Display_Register_FZ * (1 − 1/ 7)           Else if (Prechill or Defrost or Dwell) Display_Register_FZ =           Display_Register_FZ            Else Display_Register_FZ = Avg_FZ_Temp * (1 / 60) + Display_Register_FZ       * (1 − 1/60)                  
 
         [0077]    High Temperature Display  
         [0078]    If the averaged temperature of both the fresh food and freezer compartment temperatures is above a predetermined temperature that is outside of a normal operating range of refrigerator  100  (shown in FIG. 1), such as 50° F. in an exemplary embodiment, then the display of both the fresh food and freezer compartment actual temperature is synchronized to the fresh food compartment actual temperature. In an alternative embodiment, the display of both the fresh food and freezer compartment actual temperature is synchronized to the freezer compartment actual temperature.  
         [0079]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.