Abstract:
An electronic faucet has a housing adapted to seat against a support surface and defining an internal barrel having a bottom wall, a side wall and an open top. There is at least one fluid inlet extending through the bottom wall into the barrel, a fluid outlet in the side wall of the barrel, and a valve cartridge seated in the barrel. The cartridge includes a main valve for controlling fluid flow between the at least one inlet and the outlet, a pilot valve and a solenoid operator for opening and closing the pilot valve. A faucet head removably mounted to the housing covers the open top of the barrel, the faucet head including an activator which produces an output signal of a selected duration when approached by a user, and a control circuit which responds to the signal by activating the solenoid operator so as to open the pilot valve which thereupon opens the main valve. The valve cartridge is removable from the barrel while the housing remains seated against the support surface by separating the faucet head from the housing.

Description:
This invention relates to an electronic metering faucet. It relates more particularly to a faucet of this type which is preferably activated by touch and/or proximity to the faucet and which has a consistent water delivery period over the life of the faucet. 
     BACKGROUND OF THE INVENTION 
     There are several different types of metering faucets in use today. Many are manually activated to turn on the water by pressing the faucet head and are hydraulically timed so that the water remains on for a set period of time after depression of the head. Some of these faucets have separate head allowing separate control over the hot and cold water. Other metering faucets mix the incoming hot and cold water streams and, when actuated, deliver a tempered output stream. 
     Also known is a manually activated metering faucet whose on-time is controlled electronically. Still other known faucets are activated electronically when the user positions a hand under the faucet. These faucets usually incorporate an infrared or ultrasonic transceiver which senses the presence of the user&#39;s hand and turns the faucet on so long is that the hand remains under the faucet. 
     The aforesaid hydraulically timed faucets are disadvantaged in that it is difficult to accurately control the on-time of the faucet over the long term because of mains pressure changes and foreign matter build up in the faucet which can adversely affect the hydraulic controls within the faucet. On the other hand, the known electronic faucets can not always discriminate between a user&#39;s hand and other substances and objects which may be brought into proximity to the faucet, e.g. a reflective object disposed opposite the faucet&#39;s infrared transceiver, soap build up on the faucet&#39;s proximity sensor, etc. Resultantly, those prior faucets may be turned on inadvertently and/or remain on for too long a time resulting in wastage of water. 
     Still other conventional metering faucets are relatively complicated and therefore costly to manufacture. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved electronic metering faucet. 
     Another object is to provide a faucet of this type which is electronically timed and maintains its timing accuracy over the life of the faucet. 
     A further object of the invention is to provide an electronic metering faucet which may be touch activated. 
     Still another object of the invention is to provide a self-contained battery operated electronic metering faucet which can operate for over three years between battery replacements. 
     Another object is to provide such a faucet which has a minimum number of moving parts. 
     A further object of the invention is to provide a touch activated electronic metering faucet which can be manufactured at relatively low cost. 
     Another object is to provide a faucet whose parts may be accessed quite easily for maintenance purposes. 
     Still another object of the invention is to provide a faucet of this general type which is activated by single touch sensor to produce a timed and tempered water stream. 
     Other objects will, in part, be obvious and will, in part, appear hereinafter. The invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the following detailed description, and the scope of the invention will be indicated in the claims. 
     Briefly, the metering faucet is a touch activated, electronically timed faucet that can deliver water at a selected temperature for a preset water delivery period which, unless reset, remains substantially constant, i.e. within 2%, over the faucet&#39;s life span. The faucet includes a simple non-water-contacting housing or encasement which is adapted to be secured to a sink or countertop. Supported in the housing is a single cartridge containing most of the hydraulic components of the faucet including a solenoid-actuated valve which controls the delivery of water from hot and cold water lines to a single outlet at the end of a faucet spout formed by the housing. The housing or encasement also supports a stationary faucet head which contains all of the electrical components necessary to actuate the valve for a selected period of time after a user&#39;s hand touches or is moved into close proximity to a selected target area on the head. 
     As we shall see, the faucet includes provisions for preventing inadvertent faucet activation by non-environmental factors such as soap build up, contact by paper towels, etc., as well as accidental human contact. This is accomplished by dynamically adjusting in real time the faucet&#39;s activation sensitivity depending upon the prevailing conditions. Once activated, the faucet will deliver a stream of water at a set temperature for a predetermined time period. At the end of that period, the faucet&#39;s internal controls will issue a shut-off command which positively shuts off the faucet&#39;s solenoid valve. 
     Further as we will come apparent, the faucet is designed so that its components can readily be made and assembled and be accessed quiet easily by maintenance personnel for repair purposes. Still, the faucet can be made in quantity at a relatively low cost. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a front elevational view with parts in section showing a faucet incorporating the invention installed on a countertop; 
     FIG. 2 is a sectional view on a larger scale taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a fragmentary sectional view on a still larger scale showing a portion of the FIG. 2 faucet in greater detail; 
     FIG. 4 is a similar view on an even larger scale of another portion of the FIG. 2 faucet; 
     FIG. 5 is a sectional view taken along the line of  5 — 5  of FIG. 2; 
     FIG. 6 is block diagram showing the control circuitry in the FIG. 1 valve, and 
     FIG. 7 is a flow chart showing the operation of the valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, the subject faucet  10  is shown mounted to countertop  12 . The faucet includes a housing or encasement  14  having a more or less semicircular flange  14   a  at its lower end. Fasteners  16  inserted through holes  18  in countertop  12  are threaded into holes  22  in flange  14   a  to secure the faucet to the countertop. Faucet  10  also includes flexible hot and cold water lines  24   a  and  24   b  which extend from the lower end of housing  14  through a large opening  26  in countertop  12 . These water lines adapted to be coupled to hot and cold water mains. 
     As shown in FIGS. 1 and 2, the faucet housing  14  actually consists of a shell-like part  32  forms an upright main body portion  32   a  (including flanges  14   a ) and the upper portion  32   b  of a spout extending out from the main body portion  32   a . The open front of main body portion  32   a  and the underside of the spout portion  32   b  are normally closed by a removable cover plate  36  clipped or otherwise secured to the edges of portions  34   a  and  34   b.    
     Faucet  10  also has a stationary head or up  38  mounted to the top of housing  14 . Head  38  incorporates a touch sensor shown generally at  42  which, when touched, activates faucet  10  so that a stream of tempered water issues from an outlet  44  centered in an opening  46  provided in the cover plate  36  near the end of spout  34 . 
     As best seen in FIG. 2, the upper end segment of the main body portion  32   a  has a thickened internally threaded wall forming a circular ledge  46  which functions as a stop for a cylindrical cartridge shown generally at  48 . Cartridge  48  includes a side wall  52   a , a bottom wall  52   b , the top of the cartridge being open. A circular flange  54  extends out from side wall  52   a  and that flange is adapted to seat against ledge  46 . The cartridge is held in place within the shell portion  32   a  by a bushing  56  which is screwed down into the open top of main body portion  32   a.    
     An opening  58  is provided in the side wall  52   a  of cartridge  48  and an exterior collar  62  surrounds that opening into which is press fit one end of a conduit  64  which extends within the upper spout portion  32   b . The other end of that conduit constitutes the faucet outlet  44 . Preferably, there is sufficient clearance between the outlet  44  and the edge of opening  46  in the cover plate  36  to permit a conventional aerator (not shown) to be installed at outlet  44 . 
     Referring to FIGS. 2 and 3, cartridge  48  includes a pair of side by side inlet conduits  72   a  and  72   b  which extend down from the cartridge bottom wall  52   b . Formed midway along each such conduit is an annular valve seat  74  for seating vertically moveable valve member  76 . Each valve member is biased against its seat by a coil spring  78  seated within a sleeve  82  extending up from a cartridge bottom wall  52   b  within the cartridge. Each spring  78  is compressed between the upper end of the corresponding valve member  76  and a stop  82   a  provided at the upper end of each sleeve  82 . 
     The lower end segment of the cartridge conduit  72   a  forms a female connector  84  which is arranged to receive a corresponding male connector  86  provided at the upper end of the water line  24   a . The illustrated connector  86  is a conventional quick release connector which is held in place by a C-clip  88  whose arms extend through slots  92  in the opposite sides of connector  84  and engage in a groove  86   a  in male connector  86 . 
     The cold water line  24   b  is connected in a similar fashion to conduit  72   b  of cartridge  48 . It is thus apparent from FIG. 3 that each of the hot and cold water lines  24   a ,  24   b  conducts water into cartridge  48  via a check valve so that water can flow into, but not out of, cartridge  48  via conduits  72   a  and  72   b.    
     The cartridge  48  contains an electromechanical valve assembly shown generally at  96  which controls the flow of hot and cold water from lines  24   a  and  24   b  to the faucet outlet  44 . As shown in FIGS. 2 to  4 , assembly  96  sits on the two sleeves  82  projecting up from the cartridge bottom wall  52   b . As specified in FIG. 4, the valve assembly  96  comprises lower filter housing shown generally at  98 , an upper valve housing in  102 , the two housings being releasably connected together by coupling  104 . The housing  98  is shaped generally like an inverted cup. It has a side wall  106  and a top wall  106   b . The open bottom of the housing is substantially closed by a circular metering plate  108  which is the part of the valve assembly that actually sits on the sleeves  82  extending up from the cartridge bottom wall  52   a . The metering plate  108  does have metering holes  110  which are aligned with sleeves  82  so that hot and cold water is conducted via those holes from the water lines  24   a  and  24   b  to the interior of housing  98 . As shown in FIG. 4, housing  98  contains a vertically oriented filter element  112  whose opposite ends are captured by an upstanding wall  114  formed in plate  108  and a second wall  116  which extend down from the housing top wall  106   b . There is also an opening  118  near the housing top wall  106   b  that is ?? to limitation with the interior of the tubular neck  122  extending up around the housing top wall  106   b.    
     The interior of housing  98  is configured so that hot and cold water entering the housing is conducted to the periphery of the filter element  112  whereupon the water flows into the interior of the filter element and out of the filter element through the large opening  118  and neck  122 . The flow rates of the hot and cold water into the housing is controlled by the relative sizes of the metering holes  110  and the metering plate  108 . The hot and cold water are mixed within housing  98  so that the water leaving the housing through the neck  122  has a selected temperature. That temperature may be changed by substituting different meter in plates  108  in the valve assembly. 
     Sown in FIG. 4, the upper end of neck  122  is shaped leftwardly extending circular valve seat  124 . When housing  98  is connection to housing  102  by coupling  104 , a valve member  126  in the form of a diaphragm is adapted to move and down with respect to valve seat  124  to control the flow of water out of the neck  122 . A valve member  126  is supported within the valve housing  102  as we will describe in further detail presently. 
     Still referring to FIG. 4, the upper valve housing  102  has a cylindrical side wall  102   a  and a relatively thick bottom wall  102   b  the top of the housing being open. A flange  104  encircles side wall  102   a  about a third of the way down on that wall. Also an upper end segment of the side wall is threaded as shown at  106 . 
     Housing  102  is arranged to contain a cylinder solenoid  110  having a exterially threaded neck  110   a  which is threaded into a collar  112  which extends up from the housing bottom wall  102   b . Solenoid  110  has an armature  120   b  which extends down through the housing bottom wall  102   b  and is connected to the valve member  126  which is part of a more or less conventional pilot valve assembly, e.g. of the type described in U.S. Pat. No. 5,125,621, the contents of which is hereby incorporated herein by references. When solenoid  110  is energized, its armature  110   b  is retracted thereby moving the valve member  126  away from valve seat  124  allowing water to flow from the filter housing  98  past the valve seat to the opening  58  (FIG. 3) in cartridge  48  and thence via conduit  64  to the faucet outlet  44  shown in FIG.  2 . On the other hand, when the valve member  126  is seated against valve seat  124 , no water flows from the faucet. 
     As shown in FIG. 2, the valve assembly  96  is positioned in cartridge  48  so that the meter in plate  108  sits on the sleeves  82  with the metering holes  110  in that plate is aligned with those sleeves. In this position of the cartridge, the flange  104  of the valve housing  102  seats on the upper edge of the cartridge. To retain the valve assembly in this position, an exterially threaded bushing  180  is screwed down into the upper end segment of the main body portion  32  of housing  32 . Bushing  180  has a radially inwardly extending flange  180   a  which bears down against the flange  104  of the valve housing  102  to hold the valve assembly in place within the cartridge  48 . As shown in FIG. 2, when seated, the upper end of bushing  108  is flush with the upper end of the housing main body portion  32   a  and the threaded upper end  106  of the valve housing  102  extends appreciably above the bushing. 
     Referring now to FIGS. 2 and 5, the faucet head or cap  38  is secured to the upper end of the valve housing  32 . Head  38  comprises a lower housing portion  184  comprising a bottom wall  184   a  and a side wall  184   b  which flares out and up above the faucet spout  34 . A large hole  186  is provided in bottom wall  184   a  so that the housing portion  184  can be seated on the top of the main body portion  32   a  and bushing  180 . A collar  108  surrounding opening  186  extends down between the side wall  102   a  of valve housing  102  and bushing  108  with the bottom of that collar resting on the flange  180   a  to help stabilize head  38 . The housing portion  184   b  is held in place by an internally threaded ring  192  which is turned down onto the threaded upper end  106  of the valve assembly housing  102   a.    
     Faucet head  38  also includes an upper housing portion  194  in the form of a cap. Portion  194  includes a top wall  194   a  and an all-around side wall  194   b  whose lower edge interfits with the upper edge of housing portion  184  so that the head form a hollow enclosure. Housing portion  194  is releasably secured to housing portion  84  by a set screw  196  which is screwed into a threaded hole  198  in the housing portion side wall  194   b  at the rear of the faucet. When tightened, the set screw  196  engages a detent  202  formed at the rear of the housing portion  184  as shown in FIG.  2 . 
     As noted above, the faucet head  38  contains the electrical components necessary to operate the faucet&#39;s valve assembly  96 . More particularly, as shown in FIGS. 2 and 5, a printed circuit board  206  is secured by threaded fasteners  208  to a pair of posts  210  extending down from the top wall  194   a  of the upper housing section  194 . Secured to the underside of the printed circuit board  206  is a battery holder  212  which supports a plurality of batteries B and electrically connects those batteries to terminals on the printed circuit board  206  so as to power the various electrical components on the printed circuit board to be described later. The batteries B may be releasably secured to the battery holder  212  by a strap  214  or other suitable means. 
     As best seen in FIG. 2, an electrically lead  216  extends up from circuit board  206  to a metal pad  218  incorporated into a top wall  194   a  of the upper housing section  194 . Pad  218  is surrounded by an electrically insulating ring  222  which electrically isolates the pad from the remainder of top wall  194   a . That pad  218  constitutes the faucet&#39;s touch sensor  42  described at the outset. It will be apparent from FIG. 2 that all of the electrical components in head  38  may be accessed simply by loosening the set screw  196  and separating the upper housing  194  from section  184 . 
     Referring now to FIG. 6 which shows the major electrical components on printed circuit board  206  which control the operation of faucet  10 . As shown there, a microcontroller  332  operates a driver  334  which powers the solenoid  110  of the valve assembly  96 . In some faucet embodiments, the microcontroller  332  may also receive an input from an object sensor  336  which is part of a proximity transceiver  338  mounted to the faucet spout cover plate  336  just above opening  46  therein as shown in phantom in FIG.  1 . Transceiver  338  may be of a known infrared type commonly found on automatic faucets and consisting of a light emitting diode which directs a beam of infrared light downward from the spout, and an infrared sensor which detects light reflected from a hand or other object positioned under the faucet spout. 
     The circuit in FIG. 6 also includes a D-type flip-flop  242  whose D input receives pulses from microcontroller  332  by way of a resistor  344 . That D input of the flip-flop is also connected via a capacitor  346  to the metal pad  218  comprising touch sensor  242 . The Q output of a D-type flip-flop is the value that it&#39;s D input had at the time of the last leading edge of a pulse train applied to the flip-flops&#39; CLOCK (CLK) input terminal. 
     Normally, when a user has placed his hand or finger in the vicinity of the touch sensor  42 , the Q output of flip-flop  342  remains asserted continuously for the following reasons. The microcontroller  332  produces a rectangular-wave clock signal which is applied via resistor  334  to the D input terminal of flip-flop  342 . That same signal is applied to a resistor  348  and an inverter  352  to the CLK input terminal of flip-flop  342 . However there is a delay in the transmission of that pulse from microcontroller  332  to the CLK input terminal of flip-flop  342  because of the presence of a plurality of capacitors  354   a  to  354   e  which capacitively load the input circuit of converter  352  as will be described in more detail below. The value at the D input port of flip-flop  342  therefor stabilizes at the higher level before the rising leading edge of the clock pulses from inverter  352  reach the flip-flop&#39;s CLK input terminal. Therefore, the Q output of the flip-flop is high. However this situation changes when a user&#39;s hand is very close to the touch sensor  42  or actually touches it. This hand contact or proximity has the effect of capacitively loading the D input terminal of flip-flop  342 ; it may typically result in a capacitance on the order of 300 pF between sensor  42  and ground. 
     The inverter input is also connected via a diode  356  and a resistor  358  to the D input terminal of flip-flop  342 . This imposes a delay at the D input  342  of flip flop affecting the pulse level to the extent that the edge of the clock signal applied to the clock input of the flip-flop now occurs before the D input has reached the high level. Therefore, the flip-flip&#39;s Q output remains low. The microcontroller receives the compliment of that Q output at its input  362  and thereby infers that a user has touched the sensor  42 . 
     However, various environmental factors can also load the touch sensor  42 . Therefore, in a preferred embodiment of the invention, the micorcontroller  332  so adjusts the circuit&#39;s sensitivity as to minimize the likelihood of erroneous human-contact indications. As does this by employing lines  364   a  to  364   e  to ground selected one of the capacitors  354   a  to  354   e , while allowing the others to float. By selectively grounding these capacitors, the microcontroller can choose among 16 different sensitivity levels. As will be seen presently, this sensitivity adjustment is done dynamically to account for changing environmental conditions or a user&#39;s nervousness or hesitancy for being considered as multiple inputs to the faucet&#39;s touch sensing circuitry. The microconrtoller  332  monitors the output of flip-flop  342  and changes the sensitivity level of the sensing circuit according to an adapting or dynamic sensing algorithm to be discussed in connection with FIG.  7 . 
     The microcontroller  332  operates, as many battery-operated do, in a sleep/wake sequence. Most of the time, the controller is “asleep”: it receives only enough power to maintain the state of certain volatile registers, but it is not being clocked or executing instructions. This sleep state is interrupted periodically, say, every 120 ms, with a “wake” state, in which it executes various subroutines before returning to its sleep state. The duration of the wake state is typically a very small fraction of the controller&#39;s sleep state duration. 
     One of the routines performed by the microcontroller  332  when it awakens is the sensitivity adjustment routine depicted in the FIG. 7 flow chart. In FIG. 7, block  400  represents the start of that routine and block  402  represents sampling the value of the signal applied to the microcontroller sense input  362  shown in FIG.  6 . If because of the operation just described, that input&#39;s level indicates that a user is touching the touch sensor  42 , the controller sets to zero a non-touch timer representing how long it has been since the faucet detected a person&#39;s touch at touch sensor  42 . Blocks  404  and  406  represent this subroutine. As will be explained presently, the non-touch timer is used to determine when to make a sensitivity adjustment. 
     Although a touch detection is usually the basis for causing the faucet valve to open, the system is sometimes in a mode in which it is used instead to determine when to adjust sensitivity. Block  408  represents reading a flag to determine whether a sensitivity adjustment or a touch cycle is currently in progress. If it is not, the routine proceeds to increment a touch timer if that timer has not already reached a maximum value. Blocks  410  and  412  represent that incrementing operation. 
     The touch timer indicates how long a touch detection has been reported more or less continuously. As will be seen presently, an excessive touch duration will cause the system to infer that the touch detection resulted from something other than a human user and that the system&#39;s sensitivity should therefore be reduced to avoid such erroneous detections. Before the system test that duration for that purpose, however, it first performs a de-bounce operation, represented by blocks  414  and  416 , in which it determines whether the number of successive touch detections exceeds three. If it has, then at block  418 , the system resets the touch count to zero and sets a flag that will tell other routines, not discussed here, to open the valve. If these three detections have not occurred in a row, on the other hand, the system does not yet consider the touch valid and that flag is not set. 
     The system then performs a test, represented by block  420  to determine whether it should reduce the system&#39;s sensitivity. If the touch timer represents a duration less than seconds, the routine simply ends at block  421 . Otherwise, it resets the flag that would otherwise cause other routines to open the valve. It also sets a flag to indicate that the system is in its sensitivity or adjustment mode and causes a decrease in sensitivity by one step. That is, it so changes the combination of capacitors  354   a  to  354   e  in the circuit of FIG. 6 that are connected to ground that the signal applied to the CLK input of flip-flop  342  is increased. Resultantly, a greater loading of the touch sensor  42  will be required for the flip-flop  342  to indicate that a touch has occurred. Block  422  represents taking those actions. 
     It may occur in some situations that the sensitivity was already as low as it could go. If that happens, the system is in an error condition, and subsequent circuitry should take appropriate action. This is determined at block  424 . If it has, then the routine sets an error flag as indicated at block  426  and the routine ends at block  421 . If the system is not in that error condition, the routine performs the steps at blocks  406  and  408  as before. This time, however, the sensitivity-adjustment flag is set so that the test at block  408  results in the routines jumping to the step at block  422  to repeat the sensitivity-reduction sequence just described. 
     Referring to the right hand side of FIG. 7, if the block  404  step yields an indication that no touch has been detected by the touch sensor  42 , the routine resets the touch counter to zero as indicated at block  432 . 
     As was described previously, an extended period of touch detection will cause the system to reduce its sensitivity, on the theory that detection for so long a period could not have been the result of a legitimate human contact. If contact absence has been indicated for an extended period, on the other hand, it is logical to conclude that the current capacitive loading provided by capacitors  354   a  to  354   e  (FIG. 6) is consistent with contact absence but that any greater capacitance is likely to be an indication of legitimate contact of the touch sensor  42 . The system therefore responds to an extended period of detection absence by increasing the sensitivity to a value just below one that would cause touch detection with the currently prevailing capacitance loading by capacitors  354   a  to  354   e  (FIG.  6 ). 
     To this end, the routine in FIG. 7 increments the non-touch timer if that timer has not exceeded a selective maximum value, e.g. 6 seconds. Blocks  434  and  436  represent that operation. Since this point in the routine is reached as a result of the indication of block  404  that no touch has been detected, it would seem logical to reset the touch timer to zero. However, to make the illustrated system more robust to noise that could cause a non-contact indication to occur momentarily in the midst of an extending contact, the illustrated arrangement instead merely decrements the touch timer towards zero if it has not yet reached that value. Blocks  438  and  440  represent the decrementing of that timer. 
     Now if such touch-timer decrementing has occurred enough times for that timer&#39;s value to have been reduced by a selected value, say, two seconds, the system can rule out the possibility that the lack of touch detection was simply caused by noise. Therefore, since the system has assumed the sensitivity-adjustment mode as a result of that timer having reached 15 seconds, its count having been decremented to 13 seconds, can be considered as an indication that contact with the touch sensor  42  has actually ended. The touch timer is therefore set to zero and the system leaves the sensitivity-adjustment mode as indicated by blocks  442 ,  444  and  446 . 
     At block  448 , the routine then tests the non-touch timer to determine whether the absence of touch detection has lasted long enough to justify trying a sensitivity increase. If not, the routine ends at block  421 . Otherwise, the routine makes a back-up-copy of the current sensitivity at block  450  and then proceeds to determine whether an increase in sensitivity will cause a touch detection. Of course, the sensitivity cannot be increased if it is already at its maximum value so at block  452 , the routine goes to END block  421 . However if the sensitivity is not yet at its maximum value, it is increased by one step as indicated at block  458 . This is part of the sensitivity-adjustment so that that step includes setting the sensitivity-adjustment mode flag. The microcontroller  332  (FIG. 6) then samples the output of flip-flop  342  again, as indicated at block  454  and, as block  456  indicates branches on the result. In particular, if a sensitivity increase has not resulted in an apparent touch detection, then the sensitivity is increased again (because it has not reached a maximum), and the output of flip-flop  342  is sensed again. 
     This continues until an apparent touch is detected. Since the sensitivity adjustment scheme is based on the assumption that there really is no valid contact at touch sensor  42 , the sensitivity is thus reduced back by one step so that it is at the highest level that yields no touch indication. Block  458  represents this operation. 
     Now that a sensitivity-adjustment has been made, the non-touch timer is reset to zero as indicate at block  460  so that the sensitivity will not be reset again on the next controller wake cycle. The routine then ends at block  421 .