Abstract:
Towel dispensing methods and automatic towel dispensers permitting conservation of the overall amount of towel dispensed. The towel dispensing methods and towel dispensers limit the amount of towel dispensed in dispense cycles which occur shortly after an initial dispense cycle. The user is provided with sufficient towel to meet the user&#39;s needs while reducing overall towel usage and limiting towel waste.

Description:
FIELD 
     The field relates generally to the field of controls and, more particularly, to methods and apparatus for controlling towel dispenser operation and the amount of towel dispensed therefrom. 
     BACKGROUND 
     Automatic towel dispensers are well-known devices used to provide towel to users for many purposes including personal hygiene, food preparation and general maintenance of cleanliness. Automatic towel dispensers typically use a motor-powered dispensing mechanism to dispense the towel from the dispenser to a user. Automatic towel dispensers may be used with a range of materials but are commonly used to dispense paper towel in the form of web. The term “towel” as used herein is intended to be expansive in meaning and is intended to include paper and other types of materials. Examples of other materials capable of being dispensed from an automatic dispenser are kraft paper, plastic food wrap and toilet tissue. The specific type of material comprising the towel is not critical provided that the material can be dispensed from an automatic dispenser. 
     One important issue facing manufacturers of automatic towel dispensers is the need to provide the user with a length of towel sufficient to meet the user&#39;s needs while at the same time avoiding the dispensing of excessive and wasteful amounts of towel. Typically, this objective is achieved by controlling the dispensing mechanism during a dispense cycle so that towel is dispensed in an amount estimated to be sufficient to meet the needs of the average user. A further control is typically provided to impose a delay between dispense cycles to prevent immediate cycling of the dispenser and dispensing of excessive lengths of towel. The delay prevents a subsequent dispense cycle from being initiated immediately after completion of a preceding dispense cycle. The delay is typically in the range of about one to four seconds in duration. 
     For some users, the length of towel dispensed in the dispense cycle may be insufficient. With a conventional dispenser, the user would be required to initiate a new dispense cycle to obtain additional towel. However, the length of towel dispensed in two dispense cycles may be more than that needed by the user and may amount to waste. And, a user might find it inconvenient to wait as much as four seconds for initiation of a subsequent dispense cycle. 
     There is a need for improvement in these and other aspects of automatic dispenser design and operation. 
     SUMMARY 
     Methods for controlling operation of an automatic towel dispenser to provide towel sufficient to meet the user&#39;s needs yet conserve the overall amount of towel dispensed and automatic dispensers so controlled are described herein. This result is achieved by limiting the length of towel dispensed from the automatic dispenser in a dispense cycle or cycles occurring shortly after an initial dispense cycle. The user receives a full length of towel in an initial dispense cycle and a partial length of towel in each subsequent dispense cycle or cycles occurring shortly after the initial dispense cycle. The user is able to obtain enough towel to meet the user&#39;s needs by triggering dispenser operation as many times as needed to obtain the desired amount of towel. 
     To the extent that a partial length of towel is sufficient to meet the user&#39;s needs, the difference between the partial towel length dispensed and the full towel length is conserved for use by another user. A significant amount of towel is conserved over the useful life of the dispenser thereby limiting waste and reducing the cost to operate the dispenser. 
     Many dispenser embodiments may be controlled according to the methods described herein and there is no single form of dispensing apparatus which is required. In certain embodiments, a suitably controlled automatic towel dispenser may include a housing adapted to receive a roll of towel, an electrically-powered dispensing mechanism adapted to dispense the towel from the dispenser and a controller operable to control the dispensing mechanism. 
     In preferred embodiments, the controller controls the dispensing mechanism to dispense a full length of towel in a dispense cycle responsive to a user request from the user. If a further user request is made within a preset time following initiation of such dispense cycle, the controller further controls the dispensing mechanism to dispense a partial length of towel in the subsequent dispense cycle. On the other hand, if the further user request is made after the preset time, then the controller controls the dispensing mechanism to dispense a full length of towel in the subsequent dispense cycle. 
     In preferred embodiments, the controller comprises a processor, a memory and a set of instructions programmed to control the dispensing mechanism. Various other features, such as a proximity detector, may be included as desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the accompanying drawings: 
         FIG. 1  is a simplified diagram of an automatic paper towel dispenser in accordance with one embodiment of the present invention; 
         FIG. 2  is a simplified block diagram of a motor controller in accordance with the present invention and which may be used with the dispenser of  FIG. 1 ; 
         FIGS. 3A ,  3 B, and  3 C are graphs illustrating motor current during different motor operating intervals; 
         FIGS. 4A ,  4 B, and  4 C are simplified flow diagrams of the general logic implemented by the motor controller to control the motor of  FIG. 1 ; 
         FIGS. 5A and 5B  are simplified flow diagrams of the logic implemented by the motor controller to control the motor in accordance with a first embodiment based on pulse counts while the motor is operating; 
         FIGS. 6A and 6B  are simplified flow diagrams of the logic implemented by the motor controller to control the motor in accordance with a second embodiment based on pulse counts while the motor is operating and pulse counts while the motor is coasting after motor deactivation; and 
         FIGS. 7A ,  7 B, and  7 C are simplified flow diagrams of the logic implemented by the motor controller to control the motor in accordance with a third embodiment based on pulse counts while the motor is operating, pulse counts while the motor is coasting after motor deactivation, and estimated pulse counts occurring during a period of low motor current. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Methods and apparatus for controlling operation of an automatic towel dispenser in accordance with the invention will be described in connection with automatic towel dispenser embodiment  100 . Dispenser  100  is of a type useful in dispensing paper towel  105  which is in the form of a web. Embodiments include dispensers suitable for dispensing materials other than paper towel including, kraft paper, plastic food wrap, toilet tissue and other materials. 
     Advantageously, the invention may be implemented with any type of automatic towel dispenser capable of being controlled to lengthen or shorten the towel dispensed in a dispense cycle. Examples of automatic towel dispensers in which the invention may be implemented are described in related U.S. Pat. No. 7,084,592 the entire content of which is incorporated by reference. Further exemplary automatic towel dispensers capable of implementing the invention are described in commonly owned U.S. Pat. Nos. 6,903,654 and 6,977,588 and in co-pending U.S. Patent Application Ser. No. 60/749,139, the contents of each of which are incorporated herein by reference in their entirety. Many other types of automatic towel dispensers may be controlled according to the improvement and the specific type of dispenser embodiment utilized is not critical. The present invention represents an improvement and enhancement to operation of automatic towel dispensers, such as those referenced above, wherein the dispenser is controlled to provide sufficient towel to meet the user&#39;s needs yet conserve the overall amount of towel dispensed over the useful life of the dispenser. 
     Referring then to  FIG. 1 , a simplified diagram of an automatic towel dispenser  100  in accordance with one embodiment of the present invention is provided. The automatic towel dispenser  100  includes a roll  105   r  of paper towel  105  material supported in a housing  110 . The paper towel  105  is in the form of a web. Roll  105   r  is mounted on roll holders (not shown) and rotates as towel  105  is unwound from roll  105   r.    
     An electrically-powered dispensing mechanism  107  is provided to dispense the towel  105  from the dispenser  100 . In the example shown, dispensing mechanism  107  includes rollers  115   a ,  115   b , motor  120 , shaft  125  and gear  130 . The paper  105  passes through rollers  115   a  and  115   b . Roller  115   a  is a drive roller and roller  115   b  is a tension roller. Tension roller  115   b  is urged tightly against drive roller  115   a , typically by a spring-loaded mechanism (not shown), to form a nip  115   n  between rollers  115   a  and  115   b . A DC motor  120  has a shaft  125  mechanically linked to, and in power-transmission relationship with, at least one of the rollers  115   a  through a gear  130  or some other type of linkage. Paper is pulled from roll  105  and through nip  115   n  by motor-powered  120  rotation of drive roller  115   a . Paper towel  105  is dispensed through a slot  135  in the housing  110 . One edge  140  of slot  135  may have a serrated surface to cut the paper as a user grasps the paper extending beyond slot  135 . 
     A motor controller  145  receives an input from a proximity sensor  150  and controls the motor  120  to dispense either a full length of towel  105  or a partial length of towel in a dispense cycle. A “full length” means or refers to a selected towel length estimated by the dispenser manufacturer or operator to be sufficient to meet the needs of the user. A “partial length” means or refers to a towel length which is less than that of the full length. Length simply refers to the amount of towel dispensed, measured end-to-end. A length of towel is measured from the leading end  105   e  of the towel  105  protruding from the dispenser  100  (also referred to in industry as a “tail”) to the trailing end  105   t  of the towel  105  defining a single portion or sheet of towel. A “dispense cycle” means or refers to an operational cycle of the dispenser resulting in dispensing of a length of the towel responsive to a request for a towel by a user. 
     Typically, a full towel length is about 8 to 12 inches in length with 10 to 12 inches being preferred. A partial towel length would preferably be about half the full length, or about 4 to 6 inches with 5 to 6 inches being preferred. It should be clearly understood that any particular length is approximate only and that the actual length of towel dispensed may vary from dispense cycle to dispense cycle. Motor controller  145  may be preset by the manufacturer to control motor  120  to dispense the desired lengths of towel or may be provided with a control permitting the operator to set the lengths of towel to be dispensed. 
     An electrical power source, preferably in the form of battery  155 , is provided for powering components, such as the motor  120 , motor controller  145 , and proximity sensor  150 . Other electrical power sources, such as a DC transformer (not shown), may be used to supply electrical power to automatic towel dispenser  100 . The arrangement of the components in the paper towel dispenser  100  illustrated in  FIG. 1  is merely exemplary and is not intended to represent an actual physical implementation. 
     A human user initiates operation of the dispenser  100  in a dispense cycle by placing his or her body, typically the user&#39;s hand, proximate the dispenser  100  in order to trigger detection by proximity detector  150 . A signal is generated by proximity detector  150  and is communicated to motor controller  145  indicating the user&#39;s presence at dispenser  100 . This user-initiated operation of dispenser  100  is referred to herein as a “user request.” Any suitable proximity detector may be utilized. Examples of proximity detectors suitable for use in dispenser  100  are described in previously-identified U.S. Pat. Nos. 6,903,654 and 6,977,588 and co-pending U.S. Patent Application Ser. No. 60/749,139. 
     It is not necessary that a user request be communicated to dispenser  100  motor controller  145  by means of proximity detector  150 . Any suitable control may be utilized to communicate the user request to motor controller  145 . For instance, a simple contact switch in the form of a push button (not shown) on the dispenser  100  may be provided in combination with, or in place of, proximity detector  150 . A user could make the user request simply by pressing the button of the contact switch, closing the switch and sending a signal to the motor controller  145 . 
     Turning now to  FIG. 2 , a simplified block diagram of motor controller  145  is provided. Motor controller  145  includes a processing device in the form of microcontroller  200  programmed with software instructions for implementing the functions described in greater detail below. Microcontroller  200  includes an integrated analog-to-digital (A/D) converter  205  that measures the motor current digitally. 
     Microcontroller  200  employs the data collected by A/D converter  205  to detect the pulses in the motor current (Im) and control motor  120  accordingly. An exemplary microcontroller suitable for performing the functions described herein is a model number MSP430F1122IPW offered commercially by Texas Instruments, Inc. of Dallas, Tex. As described in greater detail below, microcontroller  200  may be configured to implement differing pulse counting techniques depending on the particular characteristics of the automatic dispenser in which it is employed (e.g., the paper towel dispenser  100 ). 
     Motor controller  145  includes a field effect transistor  210 , connected to an activation output terminal  215  of microcontroller  200  for activating motor  120 . A resistor  220  is provided to ensure that transistor  210  is deactivated after a reset of microcontroller  200  before its I/O ports are initialized. A resistor  225  limits short-term oscillation that may occur at the input of transistor  210  when it is activated. A capacitor  230  is coupled across the terminals of motor  120  to reduce radiation of RF energy due to brush noise (commutator switching noise) in motor  120 . A diode  235  is also provided across the motor terminals to suppress a voltage spike that may occur when motor  120  is turned off. 
     A first current sensing resistor  240  is provided to generate a voltage proportional to motor current Im when motor  120  is activated through transistor  210 . A second resistor  245  bypasses transistor  210  and generates a voltage proportional to motor current Im when motor  120  is turned off, and first current sensing resistor  240  is isolated by transistor  210 . The resistors  245 ,  250  and capacitor  255  are provided to act as a low-pass anti-aliasing filter on the motor current Im input signal. 
     The operation of motor controller  145  with respect to control of motor  120  to provide towel sufficient to meet the user&#39;s needs yet conserve the overall amount of towel dispensed is described in connection with  FIGS. 4A through 7C . Before describing the towel-conserving logic implemented in these embodiments of dispenser  100 , a digital pulse-counting system for towel-length control using digital signal techniques is discussed. Three different embodiments of such digital pulse-counting system are presented later in this document. 
       FIGS. 3A ,  3 B, and  3 C illustrate graphs of motor current Im during different motor operating intervals as follows:  FIG. 3A  illustrates a typical motor operating cycle during which a length of towel is dispensed by dispenser  100 ;  FIG. 3B  represents an expanded view of motor current Im during the startup portion of the operating cycle; and  FIG. 3C  represents an expanded view of motor current Im after motor  120  is deactivated. The data in  FIGS. 3A ,  3 B, and  3 C represents the output of A/D converter  205 , expressed in counts, over the cycle. In the illustrated embodiments, each count represents approximately 10 ma (milliamperes). However, the scaling of A/D converter  205  and the current levels in motor  120  may vary depending on the particular implementation. 
     Referring to  FIG. 3A , the operating cycle includes a “motor on” interval  300  and a “motor off” interval  305 . During a start portion  310  of motor  120  on interval  300 , it is evident that motor current Im is at its highest level within “motor on” interval  300 , and the pulses are readily discernible. In the illustrated embodiments, motor controller  145  measures pulses by comparing measured motor current Im, represented by the signal  312 , to a reference current (Im_REFERENCE), represented by the signal  313  (both shown in  FIG. 3B ). A pulse is detected, as represented by the signal  314 , when measured motor current Im drops below reference current Im_REFERENCE by a predetermined threshold (e.g., 2 counts or 20 ma). 
     As seen in  FIG. 3A , as motor  120  approaches steady state, motor current Im drops, and the magnitude of the pulses also decreases, as indicated by a low pulse signal interval  315 . In  FIG. 3B , it is evident that the bottom peaks of the motor current pulses approach reference current Im_REFERENCE such that the difference may be less than the threshold.  FIG. 3B  illustrates a missed pulse  316 , during which motor current Im failed to drop sufficiently below reference current Im_REFERENCE. 
     As described in greater detail below, motor controller  145  may detect low pulse signal interval  315  and use a pulse approximation technique to calculate the pulses that occur during the interval. To implement the approximation, motor controller  145  measures the pulse rate of pulses occurring immediately after motor  120  is turned off, as represented by the speed pulses  320  in  FIGS. 3A and 3C . The measured pulse rate is used to approximate the number of pulses that occurred during low pulse signal interval  315 . 
     Returning to  FIG. 3A , during “motor off” interval  305 , motor  120  and towel roll  105   r  coast until frictional loading causes motor  120  to stop. After motor  120  is disabled, the output of A/D converter  205  drifts up to the 6V power supply voltage (e.g., around 900 A/D counts). 
     The motor cycle represented by  FIGS. 3A ,  3 B, and  3 C depicts a motor that has relatively light loading at steady-state speed and a significant coast period (no braking). This cycle is typical for paper towel dispenser  100  of  FIG. 1 . Paper roll  105   r  has considerable inertia that results in lower values of motor current Im once roll  105   r  is in motion. Also, for cost reasons, paper towel dispenser  100  is not equipped with a braking device, resulting in an appreciable coast period. In other applications, where motor  120  is sufficiently loaded, motor current Im may not drop significantly, and a low pulse signal interval  315  may not be present. Also, if motor  120  includes a braking device, the length of “motor off” interval  305  may be decreased significantly, since minimal coasting may be present. 
     The operation of motor controller  145 , in its different embodiments, is now described in detail.  FIGS. 4A ,  4 B, and  4 C represent general logic for motor controller  145  that applies to each embodiment further detailed in  FIGS. 5A through 7C . Each of these three embodiments illustrates the towel-conserving features of the present invention. Referring first to  FIG. 4A , a 50-millisecond (50-msec) interrupt timer operating independently within motor controller  145  generates an interrupt event with a period of 50 msec. In the examples, the 50-msec timer provides an interrupt event which triggers the interrupt logic of  FIG. 4A  which in turn uses the “preset time” to establish whether such preset time has been reached following the initiation of a full length dispense cycle. After initiation of an initial (full towel length) dispense cycle, a subsequent user request made within the preset time results in dispensing of a partial towel length while a subsequent user request made after the preset time results in dispensing of a full towel length. The preset time in the embodiments described in  FIGS. 4A-7C  is 3 seconds (60×50 msec) as shown in decision blocks  409 ,  501 ,  601 , and  701 . 
     Preset time refers to an interval establishing a threshold of time used to determine whether a full or partial length of towel is to be dispensed to the user. In the examples described herein, the value of the preset time is hard-coded within the program of motor controller  145 . Alternatively, the preset time could be loaded as a constant during motor controller  145  initialization which occurs in logic block  404  in  FIG. 4B . Motor controller  145  could also be configured to allow selection among a set of preset times to be selected by an operator using an appropriate control. Examples of such a control could include switches or jumpers within motor controller  145  circuitry. 
     During operation, block  401  is entered when a 50-msec interrupt event occurs. In decision block  409 , if a variable TimeSinceFullDispense is not equal to the preset time (e.g., 60 counts or 3 seconds), motor controller  145  increments TimeSinceFullDispense by one count. If TimeSinceFullDispense is equal to the preset time (e.g., 60 counts or 3 seconds) in block  409 , the variable TimeSinceFullDispense is not incremented. Microcontroller  200  returns from the 50-msec interrupt in block  403 . 
     The combined effect of the 50-msec interrupt timer, decision block  409  and block  411  is to update the time (represented as a counter value TimeSinceFullDispense) since initiation of a “full length” towel dispense cycle as triggered by a user request. As shown in  FIG. 4A , the variable TimeSinceFullDispense is a count of 50-msec time periods, and this variable is incremented in block  411  every 50 msec until it reaches a value of 3 seconds (preset time=3 seconds=60×50 msec) in this example. When the variable TimeSinceFullDispense reaches the preset time in counts, it remains at that value until it is reset to 0 in subsequent parts of the logic of motor controller  145 . 
     Referring next to  FIG. 4B , block  400  is entered when microcontroller  200  is reset. The I/O pins are configured in block  402 , and A/D converter  205  is initialized in block  404  to generate a periodic A/D interrupt (e.g., every 200 microseconds). The 50-millisecond (msec) software-programmed interrupt timer illustrated in  FIG. 4A  is also initialized in block  404 . 
     A CONTROL_STATE variable is initialized to a READY state in block  406 . If CONTROL_STATE is not in a READY state in decision block  408  and not in a MOTOR_ON state in decision block  410 , motor controller  145  loops back to a loop marker L. If CONTROL_STATE is not in a READY state in decision block  408  and is in a MOTOR_ON state in decision block  410 , motor controller  145  transitions to motor marker M. If the CONTROL_STATE is in a READY state in decision block  408 , then motor controller  145  transitions to ready marker R. The subsequent logic at markers R and M are discussed in greater detail below since they depend on the particular embodiment. 
     Referring now to  FIG. 4C , block  412  is entered following an A/D interrupt (according to the interval initialized in block  404 ). A TIME variable (e.g., a rolling counter) is incremented in block  414 . If the difference between the reference current Im_REFERENCE and the motor current Im is less than 2 A/D counts (e.g., approximately 20 ma in the illustrated embodiment) in decision block  416 , a pulse is detected. Of course, other detection thresholds or equations may be used depending on the particular characteristics of the system employed. After detecting a pulse in decision block  416 , a PULSE_LEVEL variable is set to 1 in block  418 . If a PREVIOUS_LEVEL variable equals 0 in decision block  420  indicating that this is the first detection for the current pulse, a MOTOR_PULSES variable is incremented in block  422 , and a TIME_OF_PULSE variable is set to the current TIME in block  424 . The PREVIOUS PULSE variable is set to the PULSE_LEVEL in block  426 , and the Im_REFERENCE value for the next iteration is calculated in block  428  using the low pass filter equation Im_REFERENCE=(Im_REFERENCE*15+Im)/16. Of course, other equations, such as other averaging equations, may be used to generate the Im_REFERENCE value for the next iteration. Microcontroller  200  returns from the A/D interrupt in block  430 . 
     The interrupt frequency of the A/D converter  205  should be set such that a given pulse spans numerous interrupts (i.e., to avoid missing pulses). If the PREVIOUS_LEVEL equals 1 in block  420 , indicating that the current pulse has already been detected, the motor controller  145  transitions to block  426  and continues as described above to complete the interrupt. 
     If the pulse is not detected in decision block  416 , motor controller  145  determines if the difference between Im_REFERENCE and motor current Im is less than 0 in decision block  432  (i.e., representing motor current Im rising back above the reference current Im_REFERENCE after the downward spike and the end of the pulse). If the end of the pulse is detected in decision block  432 , the PULSE_LEVEL is set back to 0 in block  434 , and motor controller  145  continues in block  426  to complete the interrupt. 
     In a first embodiment, detailed in  FIGS. 5A and 5B , motor controller  145  is configured to control motor  120  without a significant coasting period. Hence, the motor pulses are only counted during “motor on” interval  300  of  FIG. 3A .  FIG. 5A  represents the logic implemented by motor controller  145  in the READY state of  FIG. 4B  at marker R, and  FIG. 5B  represents the logic implemented in the MOTOR_ON state at marker M. 
     In decision block  500 , motor controller  145  detects a transition of the control signal provided by proximity sensor  150  of  FIG. 1  indicating that a user request has been made and that an activation of paper towel dispenser  100  is desired. If no control signal is detected, motor controller  145  transitions back to loop marker L. 
     After detection of the control signal corresponding to the user request, decision block  501  determines whether the user request has been made within or after the preset time which, in the examples, is 3 seconds. In block  501 , if the variable TimeSinceFullDispense is equal to the preset time of 3 seconds (60 counts) then a variable PaperLength is set to a value FullLength in block  503  and the variable TimeSinceFullDispense is reset to 0 in block  505 . A value of 3 seconds (60 counts) for TimeSinceFullDispense indicates that at least 3 seconds have elapsed (at least 60 counts have occurred) since the preceding full-length dispense cycle by virtue of the fact that the variable TimeSinceFullDispense is not incremented past this value of 60 counts. 
     In a typical embodiment, FullLength has a value of around 480 pulses and this value represents the number of pulses required to deliver a full length of towel of approximately 12 inches. Of course, this number is dependent on numerous particular specifications of motor  120 , any gearing employed such as gear  130 , and the dimensions of rollers  115   a  and  115   b  used to drive towel  105  during a dispense cycle. If, for example, 480 pulses are required to deliver a 12-inch length of towel, then any other length is linearly related to this value. Thus an 6-inch towel would require a value of 240 for the variable PaperLength. 
     At decision block  501 , if TimeSinceFullDispense is not equal to the preset time, then the variable PaperLength is set at a value PartialLength in block  507 . The PartialLength setting may be, for example, 240 pulses which represents the number of pulses needed to dispense a 6 inch length of towel from the dispenser. Any length less than the full length represents a partial length. A TimeSinceFullDispense value of less than the preset 3 seconds of this example would indicate that less than 3 seconds has elapsed since initiation of the preceding full dispense cycle. In the examples, a time interval less than the preset time is referred to herein as being within the preset time while a time interval equal to the preset time is referred to herein as being after the preset time. In the exemplary embodiments, the value of the preset time in blocks  501 ,  601  and  701  is 3 seconds. Other arrangements are possible. 
     After either setting PaperLength to FullLength or PartialLength, motor controller  145  proceeds to change the CONTROL_STATE to MOTOR_ON in block  602 . In block  604 , the MOTOR_PULSES, PULSE_LEVEL, and PREVIOUS_LEVEL variables are initialized to zero, and the Im_REFERENCE variable is initialized to 250. The initialization value for Im_REFERENCE may vary depending on the particular implementation. Motor activation output terminal  215  of  FIG. 2  is set at a logic high state in block  506  to activate transistor  210  and start motor  120 . Motor controller  145  then transitions back to loop marker L. 
     On the next iteration, the CONTROL_STATE will be MOTOR_ON in block  410  of  FIG. 4B , and motor controller  145  transitions to MOTOR_ON marker M, detailed in  FIG. 5B . In decision block  508 , motor controller  145  determines if the number of MOTOR_PULSES equals PaperLength (the required number of pulses for a complete motor cycle dispensing either the full or partial length of towel). If the required number of pulses (PaperLength) has not been counted, motor controller  145  transitions back to loop marker L and motor  120  continues to operate. If the required number of pulses (PaperLength) has been counted, the CONTROL_STATE is set back to READY in block  510 , and motor  120  is turned off in block  512  by deasserting the signal (i.e., setting to a logic low state) at activation output terminal  215  to turn off transistor  210 . Motor controller  145  then returns to loop marker L on  FIG. 4B  to await another activation. The result is that the dispenser provides the user with either a partial length of towel or a full length of towel based on whether the user request occurred within or after the preset time. 
     In a second embodiment, detailed in  FIGS. 6A and 6B , motor controller  145  is configured to control a motor  120  with an appreciable coasting period. Hence, the motor pulses are counted during “motor on” interval  300  of  FIG. 3A  and during “motor off” interval  305  while motor  120  is coasting. 
       FIG. 6A  represents the logic implemented by motor controller  145  in the READY state of  FIG. 4B  at marker R, and  FIG. 6B  represents the logic implemented in the MOTOR_ON state at marker M. 
     In decision block  600 , motor controller  145  detects a transition of the control signal provided by proximity sensor  150  of  FIG. 1  indicating that a user request has been made and that an activation of paper towel dispenser  100  is desired. If no control signal is detected, motor controller  145  transitions back to loop marker L. 
     After detection of the control signal corresponding to the user request, decision block  601  determines whether the user request has been made within or after the exemplary preset time of 3 seconds since the preceding full dispense cycle. If TimeSinceFullDispense is equal to the 3 second preset time (i.e, after the preset time), then a variable PaperLength is set a value FullLength in block  603  and the variable TimeSinceFullDispense is reset to 0 in block  605 . This decision indicates that 3 or more seconds have elapsed since initiation of the preceding full towel length dispense cycle. At decision block  601 , if the TimeSinceFullDispense variable is not equal to the preset time, then the variable PaperLength is set to a value PartialLength in block  607 . This decision indicates that less than 3 seconds have elapsed since initiation of the preceding full towel length dispense cycle. The values FullLength and PartialLength are the same as those discussed in the first embodiment described above. 
     After either setting PaperLength to FullLength or PartialLength, motor controller  145  proceeds to change the CONTROL_STATE to MOTOR_ON in block  602 . In block  604 , the MOTOR_PULSES, PULSE_LEVEL, and PREVIOUS_LEVEL variables are initialized to zero, and the Im_REFERENCE variable is initialized to 250. The initialization value for Im_REFERENCE may vary depending on the particular implementation. An OFF variable is set to the current value of a RUN_PULSES variable in block  606 . In general, the OFF variable represents the number of pulses that motor controller  145  counts during “motor on” interval  300  prior to turning motor  120  off. The RUN_PULSES variable is a feedback variable that is set from a previous iteration that is adjusted based on the total number of pulses counted during the “motor off” interval  305 , as will become evident later in the logic flow. Motor activation output terminal  215  of  FIG. 2  is set at a logic high state in block  608  to activate transistor  210  and start motor  120 . Motor controller  145  then transitions back to the loop marker L. 
     On the next iteration, the CONTROL_STATE will be MOTOR_ON in block  410  of  FIG. 4B , and motor controller  145  transitions to the MOTOR_ON marker M, detailed in  FIG. 6B . In decision block  610 , motor controller  145  determines if motor  120  is on. If motor  120  is on, motor controller  145  determines if the counted MOTOR_PULSES is equal to the value of the OFF variable (i.e., initialized in block  606 ) in decision block  612 . If the required number of pulses has not been counted, motor controller  145  transitions back to loop marker L and motor  120  continues to operate. If the required number of pulses during “motor on” interval  300  of  FIG. 3A  has been counted, motor  120  is turned off in block  614  by deasserting the signal at the activation output terminal  215  to turn off the transistor  210 . An OFF_TIME variable is set to the current value of the TIME counter in block  616 , and motor controller  145  then returns to loop marker L on  FIG. 4B . 
     On the next iteration, the CONTROL_STATE is still MOTOR_ON, but the motor is off in block  610 . In decision block  618 , motor controller  145  determines the time that motor  120  has been coasting by subtracting the OFF_TIME from the current TIME and comparing that time to a Coast_Time variable. The Coast_Time variable is a predetermined constant that is set depending on the expected coast time of the motor, as illustrated by “motor off” interval  305  in  FIG. 3A . 
     If the predetermined coast time has been reached in decision block  618 , the CONTROL_STATE is returned to READY in block  620 . The number of COAST_PULSES is calculated in block  622  by subtracting the value of the OFF variable from the total MOTOR_PULSES. In block  624 , the value for RUN_PULSES is updated by subtracting the number of COAST_PULSES from PaperLength (the total number of required pulses to dispense the desired length of towel as set in the logic described in  FIG. 6A ). Hence, if the coasting characteristics of motor  120  change over time, the number of pulses that are counted during “motor on” interval  300  are adjusted to compensate such that the total number of pulses remains close to variable PaperLength. Motor controller  145  transitions back to loop marker L on  FIG. 4B  to await another activation. 
     In a third embodiment, detailed in  FIGS. 7A ,  7 B, and  7 C, motor controller  145  is configured to control a motor  120  with an appreciable coasting period and a period where motor current Im drops to a level where it is difficult to detect pulses (e.g., at steady state). Hence, the motor pulses are counted during at least a portion of “motor on” interval  300  of  FIG. 3A  and during “motor off” interval  305  while the motor is coasting. The speed pulses  320  are counted to determine a motor pulse rate for the immediately previous low pulse signal interval  315  to approximate the pulses that occurred therein.  FIG. 7A  represents the logic implemented by motor controller  145  in the READY state of  FIG. 4B  at marker R, and  FIGS. 7B and 7C  represent the logic implemented in the MOTOR_ON state at marker M. 
     In decision block  700 , the motor controller  145  detects a transition of the control signal provided by proximity sensor  150  of  FIG. 1  indicating that a user request has been made and that an activation of paper towel dispenser  100  is desired. If no control signal is detected, motor controller  145  transitions back to loop marker L. After detection of the control signal, decision block  701  determines if the variable TimeSinceFullDispense is equal to the preset time of 3 seconds. If TimeSinceFullDispense is equal to the preset time (i.e, 3 seconds in these example embodiments), then a variable PaperLength is set a value FullLength in block  703  and the variable TimeSinceFullDispense is reset to 0 in block  705 . As with the preceding examples, this represents a user request occurring after the preset time. At decision block  701 , if TimeSinceFullDispense is not equal to the preset time (i.e., within the preset time), then the variable PaperLength is set at a value PartialLength in block  707 . The values FullLength and PartialLength are the same as those discussed in the first embodiment described above. 
     After either setting PaperLength to FullLength or PartialLength, motor controller  145  proceeds to change the CONTROL_STATE to MOTOR_ON in block  702 . In block  704 , the MOTOR_PULSES, PULSE_LEVEL, and PREVIOUS_LEVEL variables are initialized to zero, and the Im_REFERENCE variable is initialized to 250. The initialization value for Im_REFERENCE may vary depending on the particular implementation. 
     In block  706 , a STOP_TIME variable is set to the current value of an ON_TIME variable, the TIME counter is set to zero, and a START_PULSES variable is set to 0. The STOP_TIME variable represents the time included in “motor on” interval  300  of  FIG. 3A . As detailed below, the STOP_TIME is adjusted as feedback is collected regarding the number of coast pulses and pulses occurring during the low pulse signal interval  315 . The initial value of the STOP_TIME variable (prior to any iterations) may be set during microcontroller  200  reset based on the expected characteristics of the particular implementation. Motor activation output terminal  215  of  FIG. 2  is set at a logic high state in block  708  to activate transistor  210  and start motor  120 . Motor controller  145  then transitions back to loop marker L. 
     On the next iteration, the CONTROL_STATE will be MOTOR_ON in block  410  of  FIG. 4B , and motor controller  145  transitions to MOTOR_ON marker M, detailed in  FIG. 7B . In decision block  710 , motor controller  145  determines if motor  120  is on. If motor  120  is on, motor controller  145  determines if the variable START_PULSES equals its initialized value of zero in decision block  712  (i.e., a low pulse signal interval has not been detected). If the START_PULSES value is zero in decision block  712 , the Im_REFERENCE value is compared to a Required Level threshold value (e.g., 67 counts or 0.67 amps in the illustrated embodiment) in decision block  714 . If the Im_REFERENCE value is less than the threshold, motor controller  145  sets the START_PULSES variable to the number of counted MOTOR_PULSES and sets the START_TIME to the current TIME in block  716 . 
     After completing either decision block  712  or block  716 , motor controller  145  determines if the STOP_TIME equals the current TIME in decision block  718 . If the STOP_TIME has not been reached, motor controller  145  returns to loop marker L. If the STOP_TIME has been reached, the variable ON_PULSES is set to the total number of counted MOTOR_PULSES in block  720  and motor  120  is turned off in block  722  by deasserting the signal at activation output terminal  215  to turn off transistor  210 . 
     Returning back to decision block  710 , if the motor is off (i.e., coasting), motor controller  145  transitions to marker M 1  shown in  FIG. 7C . After motor  120  is turned off, motor controller  145  counts speed pulses  320  in  FIG. 3A  to approximate the speed of motor  120  during low pulse signal interval  315 . In decision block  724 , the current TIME is compared to the STOP_TIME that motor  120  was turned off plus the Speed Time, a predetermined time interval for counting pulses after motor  120  is turned off. If the Stop Time has elapsed, the variable SPEED_COUNT is calculated in block  726  by subtracting the ON_PULSES from the total number of MOTOR_PULSES, and the SPEED_TIME is calculated by subtracting the STOP_TIME from the time of the last pulse, TIME_OF_PULSE. 
     After completing either decision block  724  or block  726 , motor controller  145  determines if the coast time has elapsed in decision block  728  by comparing the current TIME to the STOP_TIME plus the predetermined Coast Time. If the coast time has not elapsed, motor controller  145  returns to loop marker L. If the coast time has elapsed, the CONTROL_STATE is returned to READY in block  730 . The number of COAST_PULSES is determined by subtracting the ON_PULSES from the total MOTOR_PULSES in block  732 . Motor controller  145  determines if no START_PULSES were determined in decision block  734 . If START_PULSES still equals its initialization value of zero, low pulse signal interval  315  was never entered, and motor controller  145  was able to count all of the pulses during “motor on” interval  300 . If the START_PULSES equals zero, motor controller  145  determines a time adjustment factor in block  736  based on the calculated speed and the counted motor pulses using the equation TIME_ADJUST=(PaperLength−MOTOR_PULSES)*(SPEED_TIME/SPEED_COUNT). The difference between the PaperLength and the counted MOTOR_PULSES represents a pulse error. Multiplying the pulse error by the inverse of the pulse rate determined by counting the speed pulses  320  yields a time adjustment. If too many pulses are counted, the time adjustment factor will be negative, and the ON_TIME of the motor will be decreased. Similarly, if too few pulses are counted, the time adjustment factor will be positive, and the on time of the motor will be increased. 
     If the number of START_PULSES does not equal zero (i.e., a low pulse signal interval  315  was detected), motor controller  145  determines a time adjustment factor in block  738  based on the calculated speed and the counted motor pulses using the equation TIME_ADJUST=(PaperLength−START_PULSES−COAST_PULSES)*(SPEED_TIME/SPEED_COUNT)−(STOP_TIME−START_TIME). Subtracting the START_PULSES and the COAST_PULSES from the PaperLength yields the desired number of pulses for low pulse signal interval  315 . Multiplying the desired number of pulses by the inverse of the pulse rate calculated using the speed pulses  320  yields a calculated time that should have elapsed during the low pulse signal interval  315 . The actual time that occurred in low pulse signal interval  315  is subtracted from the calculated time to generate the time adjustment factor. Hence, if motor  120  is coasting faster than previously determined based on the pulse rate calculated from the speed pulses  320 , the difference between the calculated time and the actual time in block  738  will be negative and the ON_TIME of motor  120  will be decreased. 
     The equation of block  738  is mathematically equivalent to calculating the number of pulses that occurred in low pulse signal interval  315  based on the determined pulse rate, subtracting the Coast Pulses and the pulses counted during the “motor on” interval  300  prior to the low pulse signal interval  315  from the PaperLength to get a pulse error, and dividing the pulse error by the calculated pulse rate to generate the time adjustment factor. That is, the equation may be rewritten as:
 
TIME_ADJUST=(PaperLength−START_PULSES−COAST_PULSES−(STOP_TIME−START_TIME)* (SPEED_COUNT/SPEED_TIME))/(SPEED_COUNT/SPEED_TIME).
 
     After calculating the TIME_ADJUST in either block  736  or block  738 , the ON_TIME is adjusted by adding half of the TIME_ADJUST value to the current ON_TIME in block  740 , and motor controller  145  transitions back to loop marker L. In this third illustrated embodiment, only half of the adjustment is used to update the ON_TIME to avoid overcompensation. Of course, a different adjustment function may be employed depending on the particular implementation. 
     Motor controller  145  described herein has numerous advantages. Because motor controller  145  is implemented using software-controlled microcontroller  200 , it can be easily configured to accommodate a wide variety of motor applications. If motor  120  does not exhibit an appreciable coast time, motor controller  145  may be configured to implement the embodiment of  FIGS. 5A and 5B . If motor  120  has a coast period but is sufficiently loaded such that motor current Im does not drop below a level suitable for detecting pulses, motor controller  145  may be configured to implement the embodiment of  FIGS. 6A and 6B . Finally, if motor  120  does have a coast period and potential low pulse signal intervals, motor controller  145  may be configured to implement the embodiment of  FIGS. 7A ,  7 B, and  7 C. 
     According to the foregoing logic, it is assumed that user requests occurring 3 seconds or more apart likely represent requests from different users. A user request occurring within 3 seconds after initiation of a dispense cycle in which a full length of towel is dispensed likely represents user requests from a single user. Again, selection of a 3-second preset time is arbitrary and any time increment could be utilized. It is further assumed that the needs of a single user can be met with less than two full sheets of towel. 
     The logic controls the operation of dispenser  100  so that the different users represented by the user requests made 3 seconds or more apart are each provided with a full length of towel, thereby meeting each user&#39;s needs. Motor controller  145  controls electrical power to motor  120  so that the motor is on for the number of counted and/or calculated pulses required to dispense the full length of towel (e.g., 480 pulses). 
     And, the logic controls the operation of dispenser  100  so that the single user can, if necessary, conveniently obtain a partial length of towel after the initial full length of towel is dispensed. In this situation, motor controller  145  controls electrical power to motor  120  so that the motor is on for the number of counted and/or calculated pulses required to dispense the partial length of towel (e.g., 240 pulses). The number of pulses for the partial length of towel is fewer than the number of pulses required to dispense the full length of towel. 
     The difference between the partial length of towel dispensed and the full length of towel that would have been dispensed without the control as described herein represents towel that is conserved for use by another user. Conservation of towel is environmentally desirable and reduces the cost of dispenser operation over the lifetime of the dispenser. 
     The particular embodiments disclosed above are illustrative only; the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.