Abstract:
A low cost method and apparatus for indicating when to replace a water filter in a water and ice delivery system for a refrigerator. The invention uses a low cost microprocessor and senses the operational condition of an ice maker water valve, a water dispenser valve to monitor and track water usage. The microprocessor has a built-in memory to retain water usage and other data during a power outage, The invention also senses the status of a door switch to permit user input of a reset message indicating that the filter has been changed as well as an input indicating a different type of filter has been installed. The microprocessor controls a tri-color light emitting diode to display the status of the filter as “good”, “order” or “change” which is determined based on the selection of the type of filter system, the amount of time since the last filter change, and the amount of water usage since the last filter change.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/141,693, filed Jun. 30, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a water filtration system for a refrigerator and more particularly to an indicator for notifying a user when to change the filter. 
     2. Description of the Related Art 
     Many refrigerators, and especially those using a side-by-side configuration wherein the fresh food compartment is located to one side of the frozen food compartment, include integrated ice and water delivery systems. Typically, such systems deliver water and ice through the door of the frozen food compartment to an ice and water station recessed in the door. 
     Increasingly such systems incorporate a filtration system with a replaceable filter element or cartridge so as to improve the quality of the ice and water delivered to the user of the refrigerator. 
     Examples of such systems can be seen in U.S. Pat. No. 5,907,958 issued Jun. 1, 1999 to Coates, et al. and entitled “Refrigerator water filter”; U.S. Pat. No. 5,813,245 issued Sep. 29, 1998 to Coates, et al. and entitled “Pressure relief circuit for refrigerator contained water filter”; U.S. Pat. No. 5,715,699 issued Feb. 10, 1998 to Coates, et al. and entitled “Refrigerator water filter”; U.S. Pat. No. 5,707,518 issued Jan. 13, 1998 to Coates, et al. and entitled “Refrigerator water filter”; U.S. Pat. No. 5,135,645 issued Aug. 4, 1992 to Sklenak, et al. and entitled “Refrigerator water filter”; and U.S. Pat. No. 3,982,406 issued Sep. 28, 1976 to Hanson, et al. and entitled “Refrigerator water storage and dispensing system with water filter”. 
     Since the filters must be periodically replaced to maintain the quality of the water, various methods and apparatus could be used to notify the user of the need to change the filter. However, such many potential approaches would be costly, complex and inflexible as to substitution of different types of filters having different useful lives. Furthermore, in an effort to such reduce cost, many such approaches fail to give the user advance warning that the filter will soon need to be replaced. Additionally, the controls might be used on more than one model of refrigerator in conjunction with more than one type of filtration media. 
     What is needed, therefore, is a filter monitoring and indicating system that is flexible enough to permit its use with different types of filters. It would be most beneficial if the system doesn&#39;t add the cost of requiring an additional switch or sensor for detecting the type of filter being used but instead relies on existing components, where possible. 
     What is further needed is an inexpensive filter monitoring and indicating system that not only informs the user that a filter needs to be replaced, but provides earlier warning that the filter will need to be replaced soon and therefore a new filter needs to purchased. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a low cost method and apparatus for monitoring the operation of a water and ice delivery system for a refrigerator and indicating when to replace a water filter used in the water and ice delivery system. 
     The water filter monitoring and indicating method and apparatus of the present invention relies on components existing in many conventional water and ice delivery systems and refrigerators to reduce complexity and number of components. It senses the operational condition of the fresh food compartment door and the valves regulating the water flow into the ice maker and the water dispenser of the refrigerator. The method and apparatus monitors and tracks the duration of valve openings to estimate water consumption since the filter has been changed. Furthermore, it tracks the amount of time that has passed since the last time the filter has been changed. The method and apparatus further tracks user inputs to the fresh food compartment door switch to determine when a filter has been replaced. 
     The water filter monitoring and indicating method and apparatus of the present invention determines when the filter needs to be changed by comparing the water usage and filter age data with a first set of pre-selected standards for the type of filter being used and further determines when a new filter should be ordered by comparing the water usage and filter age data with a second set of pre-selected standards for the type of filter being used, the second set of pre-selected standards being more stringent than the first set. The method and apparatus then uses a tri-color light emitting diode to display one color when the filter should be replaced, a second color when a filter should be ordered and a third when the filter is good. 
     In the preferred embodiment of the present invention, the water filter monitoring and indicating system uses a low cost microprocessor to compare the water usage and filter age data with the first and second sets of pre-selected standards, to generate and track a conclusion of a status of “good”, “order” (or alternatively, “warn”) or “change” (or alternatively, “used”) for the filter based on such comparison, and to illuminate the light emitting diode in pre-selected color corresponding to that conclusion of status. 
     The microprocessor of the water filter monitoring and indicating system of the present invention preferably includes a built-in memory to retain water usage and other data during a power outage. 
     The light emitting diode of the water filter monitoring and indicating system preferably is illuminated green for a filter status of “good”, yellow for a filter status of “order” or “warn” and red for a filter status of “change” or “used”. 
     In the preferred embodiment, the indicator warns the user that the filter will soon be past its rated capacity and therefore that a new filter should be ordered when the filter has reached 90% of its rated age or rated water capacity. This increases the likelihood that a user will have a filter available when one is needed and increased the likelihood that the filter will be replaced in a timely manner. Typical settings for filters may be 400 gallons or 200 gallons capacity and warn at 360 gallons or 180 gallons, respectively. 
     In the preferred embodiment, the microprocessor further tracks the time that the filter has been installed and compares that with the rated life of the filter, which could be typically between 6 months and 12 months. The user will be warned to replace the filter when it has been installed in the refrigerator for more than 90% of its maximum rated installation life or age. The indicator will therefore illuminate green for a status of “good” if the filter is newer than 90% of its maximum rated age and has been used to deliver less than 90% of its rated capacity and will illuminate red for a status of change if it has exceeded 100% of either limit. Otherwise, it will illuminate yellow, for warn, indicating that it is between 90% and 100% for either age or capacity and will shortly need to be replaced. 
     The water filter monitoring and indicating system preferably further tracks user inputs to the fresh food compartment door switch to determine what type of filter is being used and utilizes a different first and second set of pre-selected standards for each type of filter selectable by the user. This can be accomplished within the microprocessor by changing the age and or capacity limits or by altering the speed of the internal counter. 
     The microprocessor is provided with programing to detect a first predetermined rapid sequence of depressions of the door switch as a request by the user to reset the age and usage counters to zero because the filter has been changed. The sequence of pulses is selected to be numerous and rapid enough to be unlikely to be accidentally sent during normal door openings and closings. The microprocessor further interprets a second predetermined sequence of depressions of the door switch as a sign that a different type of filter is being used 
     The light emitting diode of the water filter monitoring and indicating system is preferably located within the fresh food compartment of the refrigerator near the fresh food compartment door switch of the refrigerator to ease use of the indicator and to function aesthetically with the door switch in a control console that can also include the fresh food and frozen food temperature controls. The control console is preferably located on the upper front face of the fresh food compartment so as to minimize access by children. 
     It is therefore an object of the present invention to provide the consumer with a reliable measure of the filter cartridge end of life condition. 
     It is a further object of the present invention to provide an inexpensive filter monitoring and indicating system that informs the user that the filter needs to be replaced, by illuminating red and further provides early warning that the filter will need to be replaced soon and therefore a new filter needs to purchased by illuminating yellow. 
     It is another object of the present invention to provide a filter monitoring and indicating system that is flexible enough to permit its use with different types of filters yet doesn&#39;t add the cost of requiring an additional switch or sensor for detecting the type of filter being used by utilizing manual user input to the existing fresh food compartment door switch at a rate which would be unlikely to occur in normal door openings and closings. 
     These and other advantages of the present invention will become apparent to those skilled in the art when the following detailed description of the preferred embodiment is read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a refrigerator apparatus having a water filtration and filter control and indicator system embodying the present invention; 
     FIG. 2 is a schematic diagram of the ice and water assembly of the refrigerator apparatus of FIG. 1; 
     FIG. 3 is a fragmentary enlarged front view of the refrigerator control console of the refrigerator of FIG. 1; 
     FIG. 4 is a schematic electrical diagram illustrating the electrical circuitry of the filter control and indicator system of FIG. 1; 
     FIG. 4 b  is a table indicating specifications of preferred components of the filter control and indicator system of FIG. 4; 
     FIG. 5 is a flow chart illustrating the programming and logic of the filter control and indicator system of FIGS. 1 and 4 and more particularly illustrates the power-up and main subroutines of the filter control and indicator system; 
     FIG. 6 is a flow chart illustrating the filter status subroutine of the main subroutine of FIG. 5, comprising FIG.  6 A and FIG. 6B; 
     FIG. 7 is a flow chart illustrating the indicator subroutine of the main subroutine of FIG. 5, including the indicator subroutine and the diagnostics subroutine; and 
     FIG. 8 is a flow chart illustrating the reset subroutine of the main subroutine of FIG.  5 ; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Refrigerator 
     In the illustrative embodiment of the invention as shown in FIG. 1 a refrigerator  10 , comprising a side-by-side fresh food/freezer configuration, is provided having a cabinet  12  forming fresh food compartment  14  and freezer compartment  16 . 
     The fresh food compartment  14  is provided with an access opening  18  and a fresh food door  20  hingedly mounted to the cabinet  12  for selectively closing the access opening  18 . The access opening  18  has a back wall  18   a , side walls  18   b  and  18   c , top wall  18   d , and a bottom wall  18   e . The refrigerator  10  also has a partial front wall  22  disposed around the perimeter of the access opening  18  parallel to and selectively engageable with the fresh food door  20  for sealing the access opening  18 . 
     The fresh food compartment  14  is further provided with a light  24  which is connected in series with a light switch  26 . The light switch  26  is a reciprocable switch actuated to selectively connect the light  24  with a source of electrical power, not shown, when the door  20  is in an open position and to disconnect the light  24  from the source of electrical power when the fresh food door  20  is in the closed position. In the preferred embodiment, the light switch is located in portion of the partial front wall  22  above the top wall  18   d  of the access opening. 
     Similarly, the freezer compartment  16  is provided with an access opening  28  and a freezer door  30  hingedly mounted to the cabinet  12  for selectively closing the access opening  28 . The access opening  28  has a back wall  28   a , side walls  28   b  and  28   c , top wall  28   d , and a bottom wall  28   e . The refrigerator  10  also has a partial front wall  32  disposed around the perimeter of the access opening  28  parallel to and selectively engageable with the freezer door  30  for sealing the access opening  28  . The freezer compartment  14  is farther provided with a rocker-type light switch  34  which is connected in series with a light  36  functionally similar to the light  24  and light switch  26  in the fresh food compartment  14 . 
     As is farther well known in the art, the refrigerator  10  is provided with a water and ice supply system  40 , shown schematically in FIG. 2 for delivering water from an external source  42  through a filter  44  to an ice and water delivery system  46 . 
     The filter  44  may be mounted to the refrigerator below the bottom wall  28   e  of the access opening  28  and accessed for servicing by selective removal through an opening through the lowermost portion of the partial front wall  32 , as shown in FIG.  1 . The ice and water delivery system  46  includes an ice making assembly  48  mounted within the freezer compartment  16  and an ice and water dispensing system  46  mounted in the freezer door  30 . 
     The ice making assembly  48  is mounted to the inside surface of the back wall  28   a  of the freezer compartment  16 . The ice and water dispensing system  46  is provided below the ice making assembly  48  for receiving ice pieces therefrom as well as for receiving cool water from a water supply system  40 . As shown in FIG. 2, the water and ice supply system  40  includes electrically operable water valves  52  and  54  for supplying water, respectively, to the ice making assembly  48  and the ice and water dispensing system  46 . 
     The ice and water dispensing system  46  includes an ice storage receptacle or bin not shown. When operated, the ice and water dispensing system  46  transfers ice pieces from the ice storage receptacle or bin through the freezer door  30  whereby ice pieces may be dispensed through a conventional, forwardly exposed ice dispenser station or external ice service area not shown. 
     In the preferred embodiment of the present invention, a refrigerator control console  60  is defined on an upper portion of the partial front wall  22  of the fresh food compartment  16  in the vicinity of the light switch  26 . The refrigerator control console  60 , which is shown integral with the front wall  22 , includes a fresh food compartment temperature control switch  62 , a freezer compartment temperature control switch  64 , the light switch  26 . In the vicinity of the light switch  26 , the refrigerator control console also includes a filtration system status indicator  66 , described later in detail. The refrigerator control console  60  further incorporates a consumer label  67  surrounding the switch  26  and the indicator  66  on which is printed the following written matter describing the operation of the filter  44  and the meaning of the status indicator  66 : 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 “EZ-CHANGE SIGNAL 
                 FILTER INDICATOR RESET 
               
               
                   
                   
               
             
             
               
                   
                 Green = Good Filter 
                 Push the light switch 
               
               
                   
                 Yellow = Order Filter 
                 5 times in 10 seconds to reset 
               
               
                   
                 Red = Change Filter 
                 filter indicator to green.” 
               
               
                   
                   
               
             
          
         
       
     
     Components of The Water Filter Status Monitoring and Indicating System 
     Referring now to the FIG. 4, the Refrigerator  10  includes a water filter status monitoring and indicating system  70 . The water filter status monitoring and indicating system  70  includes a power supply  72  comprising resistor  74 , capacitors  76 ,  78  and  80  and diodes  82 ,  84 , and  86  in a conventional capacitive drop design with capacitor  76  as the charge pump device, diode  82  as the rectifier. Diode  84  provides noise suppression and functions as a clamping diode. Diode  86  is a zener diode used as a simple voltage regulator. Capacitor  80  functions as the reservoir capacitor and capacitor  78  provides high frequency bypass. Resistor  74  is critical to line surge performance of the overall circuit since it absorbs most of the pulse energy. 
     The water filter status monitoring and indicating system  70  has an input connector  90  with three identical discrete digital inputs  94 ,  96  and  98 . Input  94  monitors the operational status of light switch  26 . Input  96  monitors the operational status of the electrical input of water valve  54  associated with the water dispenser of the ice and water dispensing system  46 . Input  98  monitors the operational status of the electrical input of water valve  52  associated with the ice making apparatus  48 . These inputs are designed for 120V (RMS) signals directly from the monitored loads. Each of these inputs  92 ,  94  and  96  has an identical input resistive divider network respectively comprised of pairs of resistors  114   a ,  114   b ,  116   a ,  116   b ,  118   a  and  118   b . Each resistor pair,  114 ,  116  and  118 , can also be viewed as a series device to limit current into the microprocessor input pins  107 ,  108  and  109 , respectively, to the microprocessor device  140  described later, and a shunt device to provide input pull-down to a known state when the associated load is not activated. 
     The input connector  90  further has inputs  100  and  106  respectively connected to the neutral and the hot lines of the AC power supplied to the refrigerator  10 . Inputs  92 ,  102  and  104  of the input connector  90  are not used. 
     The water filter status monitoring and indicating system  70  also has a power-on reset circuit  120  comprised of resistors  122 ,  124  and  126 , transistor  128 , and capacitor  130 . Resistors  122  and  126  set the reset threshold voltage and provide base drive for the transistor  128 , and, in turn provides a pull-up voltage to master clear input  147 . Resistor  124  is a passive pull-down to the master clear input  147  of the microprocessor device  140  when VDD is low which establishes a valid logic low when VDD is below the threshold. Capacitor  130  provides filtering for high frequency noise and transients. 
     The water filter status monitoring and indicating system  70  further includes the filtration system status indicator  66 , which in the preferred embodiment consists of a bi-color device  110  containing a red LED die  132  and a green LED die  134 . 
     The microprocessor device  140  provides all logic functionality and memory. In addition to red and green, the color amber can be achieved by alternating resistors  136  and  138  by providing alternating signals from microprocessor output pins  144  and  146 . 
     Microprocessor device  140  is preferably a Microchip PIC 12CE518 device, which contains 512 words of program ROM (implemented as OTP EPROM) and includes a 16 by 16 EEPROM. 
     The specifications of the preferred components of the water filter status monitoring and indicating system  70  are as indicated on Table 1 on FIG. 4 b.    
     Programming Logic of The Water Filter Status Monitoring and Indicating System 
     FIG.  5  through FIG. 8 illustrate the programming and logic of the water filter status monitoring and indicating system  70  which is programmed into the microprocessor device  140 . The Logic is intended to provide programming for alternative models, such as an A model refrigerator a B model refrigerator or a C model refrigerator, each having different functionality. The various models may have different replacement criteria for the filters depending on the gallon rating and the useful life of the filter. 
     Referring to FIG. 5, when the power is first supplied to the microprocessor device  140 , a Power-up Subroutine  200  is initiated. At step  202 , the microprocessor device reads the stored memory. At Step  204 , the microprocessor device  140  sends a signal to the indicator  66  to flash red if the refrigerator is a Model A and green if it is a model B. 
     The microprocessor device  140  then enters a continuously repeated main subroutine  206 . Within each repetition of main subroutine  206 , microprocessor device  140  updates its clock at step  208  and, once every 18 hours, stores the time and water used in the non-volatile memory at step  210 . At steps  212  and  214 , respectively, the amount of water used is incremented if the ice valve  52  is open or if the fresh water valve  54  is open. The open time for each valve  52  and  54  is weighted for the normal water flow rate associated with the valve. At steps  216 ,  218  and  220 , respectively, the microprocessor calls the filter status subroutine  250 , the control subroutine  300  and the reset subroutine  350 , after which the main subroutine  206  repeats. 
     Referring to FIG. 6, the filter status subroutine  250  determines at steps  252  and  254  whether refrigerator  10  is a model A, B or C and directs the program to one of water usage comparison subroutines  256   a ,  256   b  and  256   c , respectively for the appropriate model. In each respective water usage comparison subroutine  256   a ,  256   b , and  256   c , at respective steps  258   a ,  258   b  and  258   c , the status of the filter is designated as “good” if less than a first predetermined time period has passed and less than a first predetermined quantity of water has been consumed, as indicated by the information stored in memory since the last reset. In each respective water usage comparison subroutine  256   a ,  256   b , and  256   c , at respective steps  260   a ,  260   b  and  260   c , the status of the filter is designated as “used” if more than a second predetermined time period of usage or more than a second predetermined quantity of water has been consumed since the last reset. In each respective water usage comparison subroutine  256   a ,  256   b , and  256   c , at respective steps  262   a ,  262   b  and  262   c , the status of the filter is designated as “warn” if the status has been set as neither “good” or “used”. 
     Finally, at step  270 , the time and water used is stored in non-volatile memory if the status of the filter has not been changed by the water usage comparison subroutine  256   a ,  256   b  or  256   c . The status is not restored if it hasn&#39;t changed so as to maximize the useful life of the EEPROM non-volatile memory. 
     Referring to FIG. 7, the control subroutine  300  determines at step  302  if the fresh food door  20  is open by monitoring the voltage across the fresh food light switch  26 . 
     If the fresh food door  20  is detected as open, then indicator subroutine  310  is run. At step  312 , the green LED die  134  is illuminated if the status of the filter has been saved as “warn” or as “good”. At step  314 , the red LED die  132  is illuminated if the status of the filter has been saved as “warn” or as “used”. Thus, if the status has been saved as “warn”, both LED die are illuminated and the status indicator  66  appears amber in color. 
     The alternating signal of red and green is created by step  312  always turning off the green die, off if it is on, and, after a built-in time delay by having step  314  always turn off the red die, if it is on. 
     If the fresh food door  20  is detected as closed, then diagnostic subroutine  320  is run. At step  322 , the green LED die is illuminated if the fresh water dispenser valve  54  is open. At step  324 , the red LED die is illuminated if the water valve  52  to the ice making apparatus  48  is open. If both valves  52  and  54  are open, both LED die are illuminated and the status indicator  66  appears amber. The diagnostic subroutine  320  permits detection of malfunctions of the water valves  52  and  54  or the water filter status monitoring and indicating system  70  by a service technician manually be depressing the light switch  26  and selectively operating the valves  52  or  54 , the service technician can isolate faults in the system. 
     Referring to FIG. 8, the reset subroutine  350  determines at steps  352  if the light switch  26  has been depressed 5 times in less than ten seconds, indicating the user is sending a reset instruction to the microprocessor device  140 . The user should do this when the filter is replaced. If a reset instruction has been detected at step  352 , then the time and water usage counters are reset to zero at step  356  and stored at step  358 . However, if the system has already been reset, within the last 10 seconds, that is, a reset instruction has been sent twice, then, at step  354 , the microprocessor device reads the input as an instruction that a different type of filter is being used and changes the model setting from a model A to a model B. Finally, at step  360 , the indicator is illuminated red or green to indicate the model setting. 
     The following details are offered to provide with even more particularly details of the best mode contemplated by the inventors at the time of filing for implementing the control described above. 
     
       
         
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Inputs/Outputs 
                 Active: 
                 Inactive: 
               
               
                   
                   
               
             
             
               
                   
                 Ice Valve Input 
                 60 Hz Input 
                 Logic Level Low 
               
               
                   
                 Water Valve Input 
                 60 Hz Input 
                 Logic Level Low 
               
               
                   
                 Light Switch Input 
                 60 Hz Input 
                 Logic Level Low 
               
               
                   
                 Red LED 
                 High Logic Level 
               
               
                   
                 Green LED 
                 High Logic Level 
               
               
                   
                   
               
             
          
         
       
     
     The filter counter (not illustrated) is a 16 bit counter in that is incremented as the ice and water valves are used. The counter is incremented once every time the valve on time reaches 2.5 seconds for the ice valve and 1.5 seconds for the water valve. These above values are determined by the flow rates of the valves actually used in the preferred embodiment and the resolution of the 8 bit timers that count the on time of the valves and may vary. Valve usage is recorded in 10 ms increments; therefor the maximum on time that can be recorded in 8 bits is 2.55 seconds. 
     Each increment of the filter counter represents the passage of 0.0125 gallons of water. A filter count value of 40,000 represents 500 gallons used and a filter count of 36,000 represents 450 gallons used. A filter count of 32,000 represents 400 gallons used and a filter count of 28,800 represents 360 gallons used. To minimize the code the software only checks the upper byte of this counter. Therefore the closest HEX values give trip points of 40,192 (0×9D00) and 36,096 (0×8D00) for normal mode and 32,000 (0×7D00) and 28,672 (0×7000) for cyst mode. The trip points in gallons are then 502.4 and 451.2 for normal mode and 400 and 358.4 for cyst mode. 
     The Real Time Counter is a 24-bit counter that is incremented every second. This counter is used to keep track of times up to 6 months in length. When 6 months is reached the counter is cleared and a flag is set to indicate that 6 months has passed. When a second 6 months has passed the timer is then frozen. 
     Time is kept using the internal RC oscillator. Using the preprogrammed oscillator calibration, 6 months can be timed to within +/−1 week. 
     In a Model A or B control the real time counter is incremented every 0.5 seconds. Therefore the timer resets when 3 months of actual time has passed. The six-month flag is then a 3-month flag. 
     Operation of the Water Filter Status Monitoring and Indicating System Components 
     The purpose of the water filter indicator is to provide the consumer with a reliable measure of the filter cartridge end of life condition. There are two criteria for end of life, namely a prescribed number of gallons or a fixed period of real time. In order to monitor the water flow, the electrical inputs to both the ice maker valve and the dispenser valve are monitored by the WFI. Since the processor “knows” that the valves have flow rates of 0.3 and 0.5 gallons per minute, the flow can be computed from the amount of time which each is energized. It is in this fashion that the usage in gallons is accumulated. 
     Real time is simply accumulated by a divider from the processor clock. Since the clock used in this case is the internal RC oscillator, it is subject to more inaccuracy than would be experienced with a crystal controlled or 60 Hz based time keeping scheme. The Microchip literature guarantees this tolerance to be about 7.0% over voltage and temperature variations. Also included in the microprocessor is an EEPROM device, which provides non-volatile retention of flow as well as real time. In the preferred embodiment there is pre-programmed OSCCAL (oscillator calibration) value described in Sec. 8.2.5, pg. 32 of the PIC12CE5XX Data Sheet. This tightens up the tolerance so that we can guarantee 6 mo. +/−1 week (˜4%). 
     The state of the water filter is indicated on a bi-color LED incorporating a red and a green die in the same package. By activating both die at a 50% duty cycle an amber color is obtained. Up to 90% life the indicator is green, from 90% to just less than 100% it is amber, and at end of life it shows red. User reset of the accumulated flow and time variables is effected by activating the door switch five times within 5 seconds. 
     In order to facilitate factory test as well as servicing in the field, the LED displays usage status only when the door is open. When the door is closed, the LED is off unless one or both of the valve inputs is active. The LED indicates red for the ice maker valve, green for the dispenser valve and amber if both valves are active. 
     The present invention therefore provide the consumer with a reliable measure of the filter cartridge end of life condition. 
     The present invention further provides an inexpensive filter monitoring and indicating system that informs the user that filter needs to be replaced, by illuminating red and further provides early warning that the filter will need to be replaced soon and therefore a new filter needs to purchased by illuminating yellow. 
     The present invention additionally provides a filter monitoring and indicating system that is flexible enough to permit its use with different types of filters yet doesn&#39;t add the cost of requiring an additional switch or sensor for detecting the type of filter being used by utilizing manual user input to the existing fresh food compartment door switch at a rate which would be unlikely to occur in normal door openings and closings. 
     The above constitutes a detailed description of the best mode of the present invention as contemplated by the inventors at the time of filing. It is further contemplated that changes and modifications may be made from the best mode described herein within without departing from the spirit of the present invention or the intended scope of the claims below.