Abstract:
An automatic temperature control system which limits the total number of valve cycles for the cold and hot water valves to, for example, a total of ten cycles yet also provides the desired temperature control of water supplied to the wash tub is described. To limit the number of valve cycles, and in one embodiment, the automatic temperature control (ATC) system includes a microprocessor which integrates the temperature of the water provided to the wash tub over time to predict the length of the time period required for the next water valve cycle. The integration balances the energy input on the “OFF” cycle with the energy input during the “ON” cycle. Such balancing limits the number of valve cycles thereby reducing the possibility for premature valve failure and facilitating reduced noise. The ATC control system also provides a pre-treater function. When the pre-treater function is selected, e.g., by depressing a momentary switch mounted on the control panel, and provided that the lid is open, the control system energizes the cold water valve for 7 seconds. As a result, cold water flows into the wash tub. The system provides temperature control yet limits the number of valve cycles during a fill even with extreme water temperatures. Even with such cycle limitations, the control provides the desired temperature control.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/091,266 filed Jun. 30, 1998. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to clothes washing machines and more particularly, to control of the temperature of water supplied to the washing machine tub. 
     BACKGROUND OF THE INVENTION 
     In at least some known washing machines, water is supplied to the machine from sources of hot and cold water such as household faucets. The washing machine includes conduits which extend from the faucets to a mixing valve, and solenoids control the mixing of water. For example, when the solenoid associated with the hot water conduit is energized, hot water flows to the mixing valve. When the solenoid associated with the cold water conduit is energized, cold water flows to the mixing valve. By selective alternate or concurrent energization of the solenoids, the passage of hot, cold, and warm water from the mixing valve to the tub is controlled. 
     The known mixing control described above provides acceptable water temperature if the incoming water temperature is within an acceptable range. The range for cold water typically is from 50 to 80° F., and the range for hot water typically is from 120 to 140° F. However, and due to temperature variations and seasonal changes depending upon geographic location, the temperature of the cold water input can drop to near freezing. In this extremely cold temperature, the detergent will not dissolve in the wash water, which can degrade performance and leave detergent residue on the clothes. 
     One known attempt to overcome problems associated with variations in the cold water temperature includes using an analog electronic control with a temperature sensor to control the water temperature by cycling the water valves during the fill cycle. While such cycling control provides adequate temperature control, the analog control does not limit the number of valve cycles. Unlimited cycling of the valves can cause water hammer (noise) and premature valve failure. For example, and with the known analog control, a water valve can cycle more than 40 times for a large fill with extreme water temperatures. 
     It would be desirable to provide a water temperature control that limits the number of valve cycles during a fill even with extreme water temperatures. Of course, even with such cycle limitation, the control should still provide the desired temperature control. 
     SUMMARY OF THE INVENTION 
     These and other objects may be attained by an automatic temperature control system which limits the total number of valve cycles for the cold and hot water valves to, for example, a total of ten cycles yet also provides the desired temperature control of water supplied to the wash tub. Particularly, and to limit the number of valve cycles, an automatic temperature control board includes a microprocessor which integrates the temperature of the water provided to the wash tub over time to predict the length of the time period required for the next water valve cycle. The integration balances the energy input on the “OFF” cycle with the energy input during the “ON” cycle. Such balancing limits the number of valve cycles thereby reducing the possibility for premature valve failure and facilitating reduced noise. 
     In one specific embodiment, the automatic temperature control (ATC) function is operator selectable by a toggle switch mounted to the control panel. When the switch is active, the ATC system cycles either the hot and/or cold water valves to control the water temperature in the tub to within the specified range. When the ATC selector switch is deactivated, then the ATC system is disabled and the clothes washer functions in the normal mode. 
     The ATC control system also includes a pre-treater function. When the pre-treater function is selected, e.g., by depressing a momentary switch mounted on the control panel, and provided that the lid is open, the control system energizes the cold water valve for 7 seconds. As a result, and if COLD or WARM is selected, cold water flows into the wash tub. If HOT is selected, warm water flows into the wash tub. 
     In an exemplary embodiment, the automatic temperature control system includes a logic board having a microprocessor and a power supply. Generally, the board is configured to provide automatic temperature control (ATC) with the well-known electromechanical control system used in commercially available washing machines. The ATC system also includes a cold control solenoid (COLD) and a hot control solenoid (HOT). These solenoids are coupled to the valves which control the flow of hot and cold water into the washing machine tub. The system further includes a temperature sensor for sensing the temperature of water in the mixer nozzle. 
     Other inputs to the board include an ATC signal, a PRE-TREATER signal, a C-IN signal, and a H-IN signal. The ATC Signal is a 120 VAC signal that is active when the ATC control is selected on the control panel. When ATC is active, the system operates to regulate the inlet water temperature by controlling the water valves to achieve the desired water temperature in the tub. The PRE-TREATER signal is a 120 VAC signal which indicates whether the system should activate the pre-treater cycle. When the PRE-TREATER signal is active, the system is powered-up and remains active for 7 seconds from the time that the PRE-TREATER signal was received. 
     The H-IN signal is a 120 VAC signal which indicates that either the hot water or warm water setting has been selected by the operator. Warm water is selected when both the H-IN and C-IN signals are present. The C-IN signal is a 120 VAC signal which indicates that either the cold water or warm water setting has been selected. The H-IN and C-IN signals are supplied to the logic board from the control panel. 
     The temperature sensor input is supplied from the temperature control thermistor for measuring the temperature of the water in the washing machine mixing nozzle. Particularly, the microprocessor includes an analog-to-digital converter, and the processor reads a signal from the thermistor. The magnitude of the signal is representative of the temperature in the mixing nozzle. 
     With respect to the outputs from logic board, the HOT water output is a feed through of the H-IN signal to the hot water valve. The COLD water output controls the cold water valve. If the ATC signal is not active, then the C-IN signal feeds through the board to the cold control valve. When the ATC signal is active, then the ATC interrupts the C-IN signal. 
     Generally, the system controls the temperature of the water in the tub by regulating the inlet water flow between the hot and cold water valves. The ATC board is de-energized until the wash cycle is started and the machine is calling for water. Power is provided through the ATC select signal. On power-up, the system determines if the pre-treater or ATC function is selected. If the ATC function is selected, then the system checks the C-IN signal and the H-IN signal to determine the desired water temperature range. The system then controls the valves so that the desired water temperature is achieved. 
     The pre-treater function enables the operator to activate the cold water valve for a fixed duration of time while the lid is in the up position. The lid position is sensed by a lid switch which is in an open state with the lid is down and a closed state when the lid is open. When the pre-treater switch is pressed, a first relay is energized to latch on the power to the control for a period of 7 seconds. A second relay is then energized to power the cold water valve for 7 seconds. At the end of the 7 second period, the relays are de-energized to turn off the cold water valve. 
     To limit the number of valve cycles, the time period during which the ATC function is active is limited by a timer. Particularly, the microprocessor includes a timer, and regardless of the water temperature, the ATC function is not enabled for a timed period. When the timed period expires, the ATC function may be enabled and continue controlling the water temperature. 
     The microprocessor also includes an accumulator which determines how much heat, or energy, has been added above or below a desired a set point. The microprocessor controls the valve cycling based on the accumulator value, i.e., when the accumulator value is zero then the water temperature is equal to the set point temperature. 
     By limiting the number of valve cycles and controlling the valve cycling based on the accumulated value above or below the set point, the automatic temperature control system provides temperature control yet limits the number of valve cycles during a fill even with extreme water temperatures. Even with such cycle limitations, and as described below in more detail, the control provides the desired temperature control. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a washing machine. 
     FIG. 2 is a schematic diagram illustration of an automatic temperature control in accordance with one embodiment of the present invention. 
     FIG. 3 is a flow chart illustrating process steps associated with the main module. 
     FIG. 4 is a flow chart illustrating process steps associated with the zero crossing module. 
     FIG. 5 is a flow chart illustrating process steps associated with the start module. 
     FIG. 6 is a flow chart illustrating process steps associated with the pre-treat module. 
     FIG. 7 is a flow chart illustrating process steps associated with the 1 second flag module. 
     FIG. 8 is a flow chart illustrating process steps associated with the pre-treat flag module. 
     FIG. 9 is a flow chart illustrating process steps associated with the analog-to-digital converter module. 
     FIG. 10 is a flow chart illustrating process steps associated with the ATC fill control algorithm module. 
     FIG. 11 is a flow chart illustrating process steps associated with the first pass management routine. 
     FIG. 12 is a flow chart illustrating process steps associated with the initial management routine. 
     FIGS. 13A and 13B are a flow chart illustrating process steps associated with the active management routine. 
     FIG. 14 is a flow chart illustrating process steps associated with the hot select module. 
     FIG. 15 is a flow chart illustrating process steps associated with the warm select module. 
     FIG. 16 is a flow chart illustrating process steps associated with the cold select module. 
     FIG. 17 is a flow chart illustrating process steps associated with the field test routine. 
     FIG. 18 is a flow chart illustrating process steps associated with the factory test routine. 
     FIG. 19 is a flow chart illustrating process steps associated with relay management. 
     FIG. 20 is a flow chart illustrating process steps associated with status initialization. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 is a perspective view of an exemplary washing machine  20 . Washing machine  20  is shown for illustrative purposes only and not by way of limitation. Washing machine  20  includes a cabinet  22  having a washer cover  24 , and a lid  26  is pivotally mounted to washer cover  24 . Supports  28  are secured to cabinet. Machine  20  also includes a control panel  30  having washing control knobs  32 ,  34 ,  36  and  38  and a timer knob  40 . A wash tub is mounted within cabinet  22 , and the wash tub is supported by a suspension system. Washing machine  20  may, for example, be a washing machine commercially available from General Electric Company, Appliance Park, Louisville, Ky. 40225. 
     The automatic temperature control described below in detail could be utilized in connection with many different types of washing machines and is not limited to practice in connection with any one particular washing machine. In one specific embodiment, the automatic temperature control system includes a logic board with a microprocessor, relays, and a thermistor temperature sensor mounted in the water-inlet stream provided to the washing machine tub. Washing machine  20  may be modified to include such system. 
     Still referring to FIG. 1, the ATC function may be operator selectable by a toggle, push-button, or rotary switch  42  mounted on panel  30 . When switch  42  is active, the ATC system will cycle either the hot and/or cold water valves to control the water temperature in the tub to within the specified range. When ATC selector switch  42  is deactivated, then the ATC system is disabled and the clothes washer will function in the normal mode. The ATC control system also may provide a pre-treater function. When selected, e.g., by depressing a momentary switch  44  mounted on control panel  30 , and provided that lid  26  is open (as sensed by a lid sensor), the control system energizes the cold water valve for 7 seconds. 
     When the ATC function is selected, the water temperature in the tub typically should be maintained within the ranges specified in Table 1 for the different wash/rinse settings. 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Temperature Ranges 
               
             
          
           
               
                   
                 WASH/RINSE 
                 TEMP RANGE 
                   
               
             
          
           
               
                   
                 SETTING 
                 WASH 
                 RINSE 
               
               
                   
                   
               
               
                   
                 HOT/COLD 
                 120-130° F. 
                 COLD 
               
               
                   
                 WARM/WARM 
                  80-100° F. 
                 80-100° F. 
               
               
                   
                 WARM/COLD 
                  80-100° F. 
                 COLD 
               
               
                   
                 COLD/COLD 
                 60-80° F. 
                 COLD 
               
               
                   
                   
               
             
          
         
       
     
     The minimum fill is 9 (US) gallons and the maximum fill is 22 (US) gallons. Generally, there should not be more than a total of ten cycles between the two valves (i.e., cold and hot valves) for each fill. Limiting the number of cycles facilitates minimizing the noise and extending the life of the valves. The ATC control system also should satisfy applicable agency standards. Well known standards are UL 244A Solid State Controls for Appliances, and UL560 Electric Home-Laundry Equipment 
     FIG. 2 is a schematic block diagram of an exemplary automatic temperature control system  50  in accordance with one embodiment of the present invention. System  50  includes an automatic temperature control logic board  52 . Logic board  52  may, for example, be mounted behind control panel  30  of washer  20 . Generally, board  52  is configured to provide an automatic temperature control (ATC) option with the well-known electromechanical control system used in commercially available washing machines. Board  52  may include a microprocessor, microcontroller, and/or logic circuitry to perform the functions described below in more detail. The terms microprocessor, processor and microcontroller as used herein refer to a processor (which may, for example, be a microprocessor, a processor, a microcontroller, an application specific integrated circuit, or logic circuitry) mounted on board  52  and programmed to perform at least some of the ATC functions as described below in more detail. 
     System  50  also includes a cold control solenoid (COLD) and a hot control solenoid (HOT). These solenoids are coupled to the valves which control the flow of hot and cold water into the washing machine tub. Generally, water flows through the valves and through a mixer nozzle before flowing into the tub. More particularly, washing machines typically include conduits adapted to be connected to sources of hot and cold water, such as household faucets. The respective conduits extend into a mixing valve having solenoids. Selecting alternative or concurrent energization of the solenoids opens and closes the water inlets into the mixing valve to provide the passage of hot, cold, and warm water from the mixing valve to the mixer nozzle. The water flows through the mixer nozzle to the tub. The water valves typically operate at 120 VAC 60 Hz at 10 watts pilot duty. Further details regarding the valves and mixer are set forth, for example, in U.S. Pat. No. 4,031,911, which is assigned to the present assignee. 
     System  50  further includes temperature sensor  54  for sensing temperature of water in the mixer nozzle. Temperature sensor  54  may, for example, be a thermistor molded into a housing that is mounted in the water stream. The time constant of the thermistor can be determined empirically. Temperature sensor  54  typically must meet UL requirement for 120 VAC isolation if system  50  does not include an isolation transformer. 
     Power is supplied to board  52  by power line L 1 . Board  52  generally operates from a power source of 120 VAC +10%, −15% 50/60 Hz. Board  52  also could be configured, for example, to operate on a 2-wire, 240 VAC +10%, −15%. Board  52  should not exceed a maximum input power of 500 milliwatts, at 120 VAC during operation, and less than 500 milliwatts in the standby or idle modes. 
     Other inputs to board  52  include an ATC signal, a PRE-TREATER signal, a C-IN signal, and a H-IN signal. The ATC signal is a 120 VAC signal that is active when the ATC control is selected, e.g., by toggling a toggle switch  53  on control panel  30 , and the machine is filling. Rather than being positioned as shown in FIG. 2, switch  53  may be in series with thermistor  54 . When switch  53  is located in this alternate position, and in an open condition, thermistor  54  will have a value which is outside a valid range and ATC control is not enabled. If switch  53  is closed and thermistor  54  is operating properly, then ATC control is enabled by toggling switch  53 . 
     When ATC is active, system  50  operates to regulate the inlet water temperature by controlling the water valves to achieve the desired water temperature in the tub. The PRE-TREATER signal is a 120 VAC signal which indicates whether system  50  should activate the pre-treater cycle. System  50  is powered-up when the PRE-TREATER signal is active. The microcomputer pulls in relay K 3 , and pulling in relay K 3  latches power to the system. Relay K 1  is pulled in to activate the cold solenoid, and the system remains active for 7 seconds from the time that the PRE-TREATER signal was received. 
     The H-IN signal is a 120 VAC signal which indicates that either the hot water or warm water setting is selected. Warm is selected when both the H-IN and C-IN signals are present. The C-IN signal is a 120 VAC signal which indicates that either the cold water or warm water setting is selected. The H-IN and C-IN signals are supplied to logic board  52  from control panel  30 . 
     The temperature sensor input is supplied from the temperature control thermistor for measuring the temperature of the water in the washing machine mixing nozzle. Particularly, the microprocessor on ATC board  52  includes an analog-to-digital converter, and the processor reads the signal from sensor  54 . The magnitude of the signal is representative of the temperature in the mixing nozzle. Temperature sensor  54  is powered by a signal supplied from an output port of the microprocessor. 
     A signal indicative of whether the washing machine tub is full is supplied to board  52  by line FULL. The state of the signal on line FULL is indicative of the machine still filling. A water level sensor  56  in flow communication with the wash tub generates the signal. 
     A lid switch  58  also provides an input to board  52 . Switch  58  indicates whether the wash machine lid is open (switch  58  is closed) or closed (switch  58  is open). 
     With respect to the outputs from logic board  52 , the HOT water output is a feed through of the H-IN signal to the hot water valve. The COLD water output controls the cold water valve. Note that if the ATC signal is not active, then the C-IN signal will feed through to the cold control valve. When the ATC signal is active, then the processor interrupts the C-IN signal. 
     Generally, system  50  controls the temperature of the water in the washtub by regulating the inlet water flow between the hot and cold water valves. ATC board  52  is de-energized until the wash cycle is started and the machine is calling for water. On power-up, system  50  determines if the pre-treater or ATC function is selected. If the ATC function is selected, then the processor checks the C-IN signal and the H-IN signal to determine the desired water temperature range. 
     Set forth below in Table 2 are possible scenarios for the different selections. 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Control Scenario 
               
             
          
           
               
                   
                 VALVES 
                 RELAYS 
               
             
          
           
               
                 SELECTION 
                 HOT 
                 COLD 
                 K1 
                 K2 
                 K3 
               
               
                   
               
               
                 HOT WASH 
                 ON 
                 CYCLE 
                 CYCLE 
                 OFF 
                 OFF 
               
               
                 WARM 
                 ON 
                 CYCLE 
                 OFF 
                 CYCLE 
                 OFF 
               
               
                 WASH 
               
               
                 WARM 
                 ON 
                 CYCLE 
                 OFF 
                 CYCLE 
                 OFF 
               
               
                 RINSE 
               
               
                 COLD WASH 
                 CYCLE 
                 ON 
                 ON 
                 CYCLE 
                 OFF 
               
               
                   
               
             
          
         
       
     
     The pre-treater function enables the operator to activate the cold water valve for a fixed duration of time while the lid is in the up position. When the pre-treater switch is pressed, relay K 3  latches on the power for a period of 7 seconds. Relay K 1  is then energized to power the cold water valve for 7 seconds. At the end of the 7 second period, relays K 1  and K 3  are de-energized to turn off the cold water valve and power down control  52 . 
     The washing machine also includes a main motor having a motor start winding START as shown in FIG.  2 . The main motor also includes a high speed run winding HIGH and a low speed run winding LOW. The HIGH winding is always in the circuit for motor starting but is switched off after starting if the slow speed is selected. The LOW winding is switched on by the motor centrifugal switch after starting. The START winding is turned off by the centrifugal switch after the motor starts. The direction in which the motor runs is controlled by switches S 1  and S 2 . A speed select switch SPEED SEL SW controls the speed at which the motor operates. Switch S 3  controls the motor speed during wash operations, and switch S 4  controls the motor speed during spin operations. 
     The washing machine also includes a pump motor PUMP and timer motor TIMER. The pump motor PUMP discharges water from the machine. The timer motor TIMER drives the cam which actuates the switches, e.g., switches S 5 , S 6 , S 7 , S 8 , S 9 , S 10 , and S 11 . 
     Set forth below are flow charts describing process steps executed by the microprocessor on ATC board  52  in carrying out the various operations to provide ATC and pre-treater control. It should be understood, of course, that the present invention is not limited to the specific process steps and sequences set forth in the flow charts. In addition, the routines could be stored in a read only memory (ROM) associated with processor, or such routines could be implemented in the microprocessor firmware. 
     Specifically, FIG. 3 is a flow chart  70  illustrating process steps associated with a main execution module. As shown in FIG. 3, when executing the main module, the processor calls a zero crossing synchronization routine  72 . The zero crossing routine is described below in detail in connection with FIG.  4 . After executing the zero crossing routine, then the microprocessor reads  74  the user selections from control panel  30  and lid switch  58 . The microprocessor then checks the status of a  1  second trigger flag and a phase time trigger flag  76 . The  1  second trigger flag, as described below in more detail, is used in connection with updating the microprocessor timers. The microprocessor also reads the signal from the temperature sensor in the mixing nozzle, and the analog signal from the sensor is converted from an analog signal to a digital signal. A sensor diagnostic routine is then executed  78 . The sensor diagnostic routine checks whether the value of thermistor  54  is out of a valid range. If the thermistor is not within the valid range, then ATC operations are suspended, i.e., a sensor error flag is set to on and relays K 1 , K 2 , and K 3  are set to off, as described below in more detail in connection with FIG.  19 . Also, and if enabled, field diagnostic  80  and factory diagnostic  82  routines are executed. These routines are described below in more detail in connection with FIGS. 17 and 18. 
     The ATC fill control algorithm is then executed  84  using the received inputs. The microprocessor then executes a relay management routine  86 . Upon completion of the relay management routine processing returns to executing the zero crossing synchronization routine  72 . 
     FIG. 4 is a flow chart  90  illustrating process steps associated with the zero crossing module. Particularly, the microprocessor checks whether the ATC input signal is “HIGH”  92 . Such a HIGH state exists when an operator selects the ATC function on the control panel using, for example, a push button type switch. Once a HIGH state is detected, the microprocessor then checks whether the ATC input signal is in the HIGH state for at least 1 ms  94 . This check is done for noise filtering. If the ATC input signal is in the HIGH state for at least 1 ms, then the routine is exited  96 . As illustrated in FIG. 3, once the zero crossing synchronization module is exited, the microprocessor then proceeds in executing other process steps associated with ATC control. 
     FIG. 5 is a flow chart  110  illustrating process steps associated with reading the user selections and the state of the lid switch (step  74  in FIG.  3 ), sometimes referred to herein as the start module. In executing the start module, the microprocessor reads the user selections from control panel  30 , and sets relays K 1 , K 2 , and K 3  to an OFF state  112 . If the lid is up, the ATC input is off (or not active), and the hot and cold inputs are off  114 , then the pre-treat function, or module, is executed  116 . If these conditions are not satisfied, and if the ATC input is on and either the hot input or the cold input is on  118 , then the processor calls the main module  120 . Otherwise, processing returns to reading the user selections and setting relays K 1 , K 2 , and K 3  to the OFF state  112 . 
     FIG. 6 is a flow chart  130  illustrating process steps associated with the pre-treat module. Once the pre-treat module is called, the microprocessor then sets relays K 1  and K 3  to the ON state and sets a timer equal to zero  132 . Once the timer has counted 7 seconds  134 , then microprocessor  54  sets relays K 1  and K 3  to the OFF state  136 . Power is then removed from the ATC board  138 . 
     FIG. 7 is a flow chart  160  illustrating process steps associated with the 1 second flag module. The module is utilized for setting timers and flags used in other modules. Particularly, when the TIME_MAINS module is called  162 , TIME_MAINS is decremented and if the main timer goes to zero  164 , then TIME_MAINS is set to equal 60 Hz and the TRIGGER_ 1  SEC FLAG is set to ON  166 . The processor then exits the module  168 . If the module is called and if TIME_MAINS does not go to zero  164 , then the processor exits  168  the module without setting the flag. 
     FIG. 8 is a flow chart  180  illustrating process steps associated with the PHASE TIME flag module. This module is used for setting the PHASE TIME flag. Particularly, when the TIMER  1  module is called  182 , the phase time (PT) timer is decremented and if TIMER  1  goes to zero  184 , TIMER  1  is set to equal phase time and the TRIGGER_PT is set to ON  186 . The processor then exits the module. If the module is called and if TIMER  1  does not go to zero  184 , processor  54  exits the module  188  without setting the flag. 
     FIG. 9 is a flow chart  200  illustrating process steps associated with the analog-to-digital converter module. Generally, the processor controls the charging and discharging of a capacitor coupled to sensor  54 , and measures the decay rate of the capacitor. The decay rate is a function of the temperature sensed by temperature sensor  54 . More particularly, when the processor converts the analog temperature sensor signal to a digital signal, the processor causes the capacitor to discharge  202 . Then, the processor enables the capacitor to be charged through a calibration resistor and the charge time is measured  204  by the processor. The processor then enables the capacitor to discharge  206  and to be charged through sensor  54 . The charge time is measured  208  by the processor. The processor then determines the resistance at the sensor by multiplying the time to charge the capacitor through the sensor resistor by the magnitude of the calibration resistor, and then dividing the resulting value by the time to charge the capacitor through the calibration resistor  210 . The determined resistance value of the sensor is then stored in memory. The above described process is then repeated multiple times, e.g., four times, to obtain four resistance values of the sensor. These values are then averaged to provide a filtered value for the resistance of the sensor  212 . This resistance value is representative of the temperature of the water at sensor  54 . 
     FIG. 10 is a flow chart  220  illustrating process steps associated with the ATC fill control algorithm module. Generally, the processor checks the status of the algorithm  222 . If it is the first pass  224  through the module, then a first pass management routine (e.g., initializing counters) is executed  226 . If it is the initial complete pass through the module  228 , then an initial management routine (e.g., for purging the lines of water and measuring the temperature of the water) is executed  230 . If it is an active pass through the module  232 , then an active management routine (e.g., for controlling cycling of the valves) is executed  234 . The module is then exited after executing the appropriate routine  236 . 
     FIG. 11 is a flow chart  240  illustrating process steps associated with the first pass management routine. As shown in FIG. 11, relays K 1 , K 2 , and K 3  are set to OFF, and the cycle timer is set to equal zero. The cycle time also is set to equal the start cycle, phase is set to OFF, and an accumulator is set to equal the temperature of the temperature sensor, which initially is zero. Also, timer  2  is set to equal the purge time, and the status is set to INITIAL  242 . Then, based on the user selection of COLD, WARM, or HOT  244 , the phase time flag is set to equal DTC  246 , DTW  248 , or DTH  250 , respectively. DTC corresponds to a flow rate of 60% maximum, DTW corresponds to a flow rate of 100% maximum, and DTH corresponds to a flow rate of 40% maximum. The processor then exits the first pass management routine  260 . 
     FIG. 12 is a flow chart  280  illustrating process steps associated with the initial management routine. In this routine, the processor first checks the status of the phase time flag  282 , and if the flag status in ON, then the temperature difference (DELTA_TEMP) is set to SET_POINT−TEMPERATURE (i.e., the temperature sensed by sensor  54 ), and the accumulator is increased by ACCUM=ACCUM+DELTA TEMP. If the PT flag is not ON, or after making the settings indicated at step  284 , processing continues by determining whether TIMER  2  is equal to zero  286 . If TIMER  2  is not equal to zero, then the routine is exited  288 . If TIMER  2  is equal to zero, then TIMER  2  is set to equal 1 second  290 . Processor  54  then continues by determining whether the COLD  292 , WARM  294 , or HOT  296  selections have been made at the control panel. 
     If COLD is selected  292 , then relay K 1  is set to ON  298 , and if the measured temperature is not less than or equal to a preset LOW LIMIT  300 , the routine is exited  302 . If the measured temperature is less than the preset LOW LIMIT  300 , processor sets relay K 2  ON, phase is set ON, the PT flag is set to DTW, timer  2  is set to PHASE_TIME, and the STATUS is set to ACTIVE  304 . The processor then exits the routine  306 . 
     If WARM is selected  294 , and if the measured temperature is not less than or equal to a preset LOW LIMIT  308 , the routine is exited  310 . If the measured temperature is less than the preset LOW LIMIT  308 , the processor sets relay K 2  ON, phase is set ON, the PT flag is set to DTH, timer  2  is set to PHASE_TIME, and the STATUS is set to ACTIVE  312 . Processor  54  then exits the routine  306 . 
     If HOT is selected  296 , and if the measured temperature is not greater than or equal to a preset HIGH LIMIT  314 , the routine is exited  310 . If the measured temperature is greater than the preset HIGH LIMIT  314 , the processor sets relay K 1  ON, phase is set ON, the pre-treat flag is set to DTW, timer  2  is set to PHASE_TIME, and the STATUS is set to ACTIVE  316 . The processor then exits the routine  306 . 
     FIGS. 13A and 13B are a flow chart  320  illustrating process steps associated with the active management module. In this routine, the processor first checks the status of the 1 second flag  322 . If the flag is on, then the processor checks whether TIMER  2  equals zero  324 . If TIMER  2  does not equal zero, then TIMER  2  is decremented  326 . After decrementing TIMER  2 , or if the 1 second flag is not active, or if TIMER  2  is equal to zero, then processing proceeds to checking whether the phase time flag is active  328 . If the phase time flag status is ON, then the temperature difference (DELTA_TEMP) is set to the SET_POINT TEMPERATURE minus the current temperature and DELTA_TEMP is added to the accumulator  330 . If the PHASE TIME flag status is not ON, or after making the settings indicated at step  330 , processing continues by determining whether WARM SEL is active and whether the lid is open  332 . If WARM SEL is active and the lid is open, then the phase time is set to equal DTC, phase is set to off, TIMER  2  is set to zero, and relay K 2  is set off  334 . Routine  320  is then exited  336 . Such control facilitates preventing a user from coming into direct contact with hot water flowing into the wash tub. 
     If WARM is not selected or if the lid is not open, then the processor  25  checks whether phase is set to OFF  338 . If phase is set to OFF, and if TIMER  2  is not set to zero  340 , then the processor exits the routine  342 . If TIMER  2  is set to zero  340 , and if the number of cycles is not less than or equal to a predetermined number of cycles (e.g., 10 cycles)  344 , then the processor exits the routine  346 . If the number of cycles is less than or equal to the predetermined number of cycles  344 , then the processor sets TIMER  2  equal to PHASE_TIME  348 . The processor then determines whether COLD or WARM has been selected  350 . If COLD or WARM is not selected, and if the ACCUMULATOR value is greater than or equal to zero  352 , then the routine is exited  354 . If COLD or WARM is selected  350 , and if the ACCUMULATOR value is greater than zero  356 , then processing proceed to step  360 . Processing also proceeds to step  360  if COLD or WARM are not selected  350  and the ACCUMULATOR value is less than zero  352 . At step  360 , the switch value routine is called, phase is set to on, cycle is set to cycle +1, MAX_TIME_ON is set to equal MAX_TIME_ON+5, and TIMER  2  is set to equal MAX_TIME_ON. Routine  320  is then exited  362 . 
     At step  338 , if phase is not set to OFF, then the processor determines whether TIMER  2  is equal to zero  364 . If TIMER  2  is not equal to zero, the processor determines whether COLD or WARM has been selected  366 . If COLD or WARM is selected, and if the accumulator value is greater than or equal to zero  368 , then routine  320  is exited  370 . 
     The following operations limit the time that hot water is provided to the tub. Limiting the time period for the flow of hot water to the tub enables better control of the temperature of the water in the tub. Particularly, and still referring to FIGS. 13A and 13B, if COLD or WARM is selected and if the accumulator value is not greater than zero  372 , routine  320  is exited  358 . If the accumulator value is less than zero  368  or greater than zero  372 , then the processor determines  374  whether TIMER  2  is greater than MAX_TIME_ON−2. If no, then routine  320  is exited. If yes, then the SWITCH VALVE routine is called, phase is set to off, cycle time is set to cycle time+increment cycle time value (5 sec.) and TIMER  2  is set to equal cycle time  376 . Step  376  also is executed if at step  364 , processor determines that Timer  2  is equal to zero. After executing step  376 , the processor exits the routine  378 . 
     FIG. 14 is a flow chart  360  illustrating process steps associated with the hot select module. Once the hot selection module is called  362 , processor  54  checks whether DELTA_TEMP is greater than zero  364 . If DELTA_TEMP is not greater than or equal to zero, then processor  54  sets K 1  to ON, PHASE to ON, and PT equal to DTW  386 . If DELTA_TEMP is greater than zero  384 , then processor  54  sets K 1  to OFF, PHASE to OFF, and PT equal to DTH  388 . Processor  54  then exits the routine  390 . 
     FIG. 15 is a flow chart  400  illustrating process steps associated with the warm select module. Once the warm selection module is called  402 , processor  54  checks whether DELTA_TEMP is greater than zero  404 . If DELTA_TEMP is not greater than or equal to zero, then processor  54  sets K 2  to OFF, PHASE to OFF, and PT equal to DTW  406 . If DETLA_TEMP is greater than zero, then processor  54  sets K 1  to ON, PHASE to ON, and PT equal to DTH  408 . Processor  54  then exits the routine  410 . 
     FIG. 16 is a flow chart  420  illustrating process steps associated with the cold select module. Once the cold selection module is called  422 , processor  54  checks whether DELTA_TEMP is greater than zero  424 . If DELTA_TEMP is not greater than or equal to zero, then processor  54  sets K 2  to OFF, PT equal to DTC, and PHASE to OFF  426 . If DETLA_TEMP is greater than zero, then processor  54  sets K 2  to ON, PT equal to DTW, and PHASE to ON  428 . Processor  54  then exits the routine  430 . 
     The following values can be used for the variables referenced in the control algorithm described above. 
     HOT SEL: SET POINT=130° F. 
     HOT HIGH LIMIT TEMPERATURE=135° F. 
     WARM SEL: SET POINT=95° F. 
     WARM LOW LIMIT TEMPERATURE=85° F. 
     COLD SEL: SET POINT=70° F. 
     COLD LOW LIMIT TEMPERATURE 65° F. 
     TIMING 
     DTW=1 SEC 
     DTC=1 SEC 
     DTH=2 SEC 
     PURGE_TIME=30 SEC 
     PHASE_TIME=20 SEC 
     INCREMENT_CYCLE_TIME=5 SEC 
     FIG. 17 is a flow chart illustrating process steps associated with a field test, or diagnostic, routine  440  referenced at step  80  in FIG.  3 . Once called, or started,  442 , the processor checks whether TIMER_SEC is less than 5 seconds  444 . If the value of TIMER_SEC is not less than 5 seconds, then SEL_STATUS is disabled  446  and processing returns to the main routine  448 . If TIMER_SEC is less than 5 seconds, then the processor determines whether LAST_SEL equals hot and SEL_STATUS equals zero  450 , LAST_SEL equals warm and SEL_STATUS equals one  452 , or LAST_SEL equals hot and SEL_STATUS equals 2  456 . If none of these conditions are met, processing returns to the main routine. If LAST_SEL equals hot and SEL_STATUS equals zero  450 , then the processor determines if SELECTION equals warm  458 . If SELECTION equals warm, then LAST_SEL is set to equal warm and SEL_STATUS is set to equal one  460 , and processing returns to the main routine  462 . If SELECTION is not equal to warm, then processing returns directly to the main routine  462 . 
     If LAST_SEL equals warm and SEL_STATUS equals 1  452 , then the processor determines if SELECTION equals hot  464 . If SELECTION equals hot, then LAST_SEL is set to equal hot and SEL_STATUS is set to equal 2  466 , and processing returns to the main routine  462 . If SELECTION does not equal hot, then processing returns directly to the main routine  462 . 
     If LAST_SEL equals hot and SEL_STATUS equals 2  456 , then the processor checks whether an error sensor flag is on  468 . If an error sensor flag is on, then the cold valve is cycled on for 3 seconds  470 . If an error sensor flag is not on, then the cold valve is cycled on for 10 seconds  472 . Processing then returns to the main routine  462 . 
     To perform the field test, and in accordance with the routines described in connection with FIGS. 17 and 20, the technician selects Hot fill water from the selector switch. Then, the technician selects Wash on the timer and pulls the timer knob to start the washer. Within three seconds, the technician switches the water temperature select to Warm and back to Hot. If the board is good, the Cold valve is switched ON by the control within 4 to 5 seconds. Then, if the control senses a good sensor, the Cold valve will remain ON for 10 seconds. Or, if the control senses a bad sensor, the COLD valve will switch to OFF after three seconds. 
     FIG. 18 is a flow chart illustrating process steps associated with a factory test, or diagnostic, routine  480  referenced at step  82  in FIG.  3 . After starting  482  the routine, the processor checks whether TIMER_SEC has a value less than 3 seconds  484 . If no, processing returns to the main routine  488 . If yes, then the processor checks whether LAST_SEL equals warm and SEL_STATUS equals zero  490 , or if LAST_SEL equals cold and SEL_STATUS equals 1  492 . If none of these conditions are met, then processing returns to the main routine. If LAST_SEL equals warm and SEL_STATUS equals zero  490 , then the processor checks whether SELECTION equals cold  494 . If no, then processing returns to the main routine  496 . If yes, then LAST_SEL is set to equal cold and SEL_STATUS is set to equal one  498 . 
     If LAST_SEL equals cold and SEL_STATUS equals one  492 , then the processor checks whether the error sensor flag is on  500 . If yes, then processing returns to the main routine  496 . If no, then the cold valve is cycled on for 3 seconds  502 . Processing then returns to the main routine  496 . 
     To perform the factory test, and in accordance with the routines described in connection with FIGS. 18 and 20, the technician selects Warm fill water from the selector switch. Then, the technician selects Wash on the timer and pulls the timer knob to start the washer. Within fifteen seconds, with the lid up, the technician switches the water temperature select to Cold. The Hot valve will turn OFF when Cold is selected. After a two second delay, the Hot valve will switch back ON for three seconds if lid-up is sensed and the board and sensor are good. 
     FIG. 19 is a flow chart illustrating process steps associated with a relay management routine  510  referenced at step  80  in FIG.  3 . Once called, the processor checks whether the sensor error flag is on  512 , and if the error flag is on, then relays K 1 , K 2 , and K 3  are set to off. If the error flag is not on, or after setting relays K 1 , K 2 , and K 3  off, then the processor drives the out port  516 . Relays K 1 , K 2 , and K 3  are then set to K 1  output, K 2  output, and K 3  output. 
     FIG. 20 is a flow chart illustrating process steps associated with status initialization routine  530 . Upon power up of the ATC board  532 , the processor checks to determine whether SELECTION equals hot  534 . If SELECTION equals hot, then processor sets LAST_SEL equal to hot and SEL_STATUS equal to zero  536 , and processing continues with the main routine  538 . If SELECTION is not equal to hot, then the processor checks whether SELECTION equals warm  540 . If SELECTION is not equal to warm, then SEL_STATUS is set to disable  542  and processing continues with the main routine  538 . If SELECTION is equal to warm, then the processor sets LAST_SEL equal to warm and SEL_STATUS equal to zero, and processing continues with the main routine  538 . 
     From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.