Patent Publication Number: US-9895148-B2

Title: Monitoring speed control and precision incrementing of motor for powered surgical instruments

Description:
BACKGROUND 
     The present disclosure relates to surgical instruments and, in various circumstances, to surgical stapling and cutting instruments and staple cartridges therefor that are designed to staple and cut tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the present disclosure, and the manner of attaining them, will become more apparent and the present disclosure will be better understood by reference to the following description of the present disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a surgical instrument that has an interchangeable shaft assembly operably coupled thereto; 
         FIG. 2  is an exploded assembly view of the interchangeable shaft assembly and surgical instrument of  FIG. 1 ; 
         FIG. 3  is another exploded assembly view showing portions of the interchangeable shaft assembly and surgical instrument of  FIGS. 1 and 2 ; 
         FIG. 4  is an exploded assembly view of a portion of the surgical instrument of  FIGS. 1-3 ; 
         FIG. 5  is a cross-sectional side view of a portion of the surgical instrument of  FIG. 4  with the firing trigger in a fully actuated position; 
         FIG. 6  is another cross-sectional view of a portion of the surgical instrument of  FIG. 5  with the firing trigger in an unactuated position; 
         FIG. 7  is an exploded assembly view of one form of an interchangeable shaft assembly; 
         FIG. 8  is another exploded assembly view of portions of the interchangeable shaft assembly of  FIG. 7 ; 
         FIG. 9  is another exploded assembly view of portions of the interchangeable shaft assembly of  FIGS. 7 and 8 ; 
         FIG. 10  is a cross-sectional view of a portion of the interchangeable shaft assembly of  FIGS. 7-9 ; 
         FIG. 11  is a perspective view of a portion of the shaft assembly of  FIGS. 7-10  with the switch drum omitted for clarity; 
         FIG. 12  is another perspective view of the portion of the interchangeable shaft assembly of  FIG. 11  with the switch drum mounted thereon; 
         FIG. 13  is a perspective view of a portion of the interchangeable shaft assembly of  FIG. 11  operably coupled to a portion of the surgical instrument of  FIG. 1  illustrated with the closure trigger thereof in an unactuated position; 
         FIG. 14  is a right side elevational view of the interchangeable shaft assembly and surgical instrument of  FIG. 13 ; 
         FIG. 15  is a left side elevational view of the interchangeable shaft assembly and surgical instrument of  FIGS. 13 and 14 ; 
         FIG. 16  is a perspective view of a portion of the interchangeable shaft assembly of  FIG. 11  operably coupled to a portion of the surgical instrument of  FIG. 1  illustrated with the closure trigger thereof in an actuated position and a firing trigger thereof in an unactuated position; 
         FIG. 17  is a right side elevational view of the interchangeable shaft assembly and surgical instrument of  FIG. 16 ; 
         FIG. 18  is a left side elevational view of the interchangeable shaft assembly and surgical instrument of  FIGS. 16 and 17 ; 
         FIG. 18A  is a right side elevational view of the interchangeable shaft assembly of  FIG. 11  operably coupled to a portion of the surgical instrument of  FIG. 1  illustrated with the closure trigger thereof in an actuated position and the firing trigger thereof in an actuated position; 
         FIG. 19  is a schematic of a system for powering down an electrical connector of a surgical instrument handle when a shaft assembly is not coupled thereto; 
         FIG. 20  is an exploded view of one aspect of an end effector of the surgical instrument of  FIG. 1 ; 
         FIGS. 21A-21B  is a circuit diagram of the surgical instrument of  FIG. 1  spanning two drawings sheets; 
         FIG. 22  illustrates one instance of a power assembly comprising a usage cycle circuit configured to generate a usage cycle count of the battery back; 
         FIG. 23  illustrates one aspect of a process for sequentially energizing a segmented circuit; 
         FIG. 24  illustrates one aspect of a power segment comprising a plurality of daisy chained power converters; 
         FIG. 25  illustrates one aspect of a segmented circuit configured to maximize power available for critical and/or power intense functions; 
         FIG. 26  illustrates one aspect of a power system comprising a plurality of daisy chained power converters configured to be sequentially energized; 
         FIG. 27  illustrates one aspect of a segmented circuit comprising an isolated control section; 
         FIG. 28 , which is divided into  FIGS. 28A and 28B , is a circuit diagram of the surgical instrument of  FIG. 1 ; 
         FIG. 29  is a block diagram the surgical instrument of  FIG. 1  illustrating interfaces between the handle assembly  14  and the power assembly and between the handle assembly  14  and the interchangeable shaft assembly; 
         FIG. 30  is a plan view of a speed sensor assembly for a surgical instrument power train; 
         FIG. 31  is a longitudinal cross section through plane A of  FIG. 30 ; 
         FIG. 32  is a perspective view of a speed sensor assembly for a brushless motor; 
         FIG. 33  is a transverse cross section through plane B of  FIG. 32 ; 
         FIG. 34  illustrates a feedback indicator of a feedback system in accordance with one aspect; 
         FIG. 35  illustrates a feedback indicator of a feedback system in accordance with one aspect; and 
         FIG. 36  illustrates a feedback indicator of a feedback system in accordance with one aspect. 
     
    
    
     DESCRIPTION 
     Applicant of the present application owns the following patent applications that were filed on Mar. 6, 2015 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/640,746, entitled POWERED SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2016/0256184;   U.S. patent application Ser. No. 14/640,795, entitled MULTIPLE LEVEL THRESHOLDS TO MODIFY OPERATION OF POWERED SURGICAL INSTRUMENTS; now U.S. Patent Application Publication No. 2016/0256185;   U.S. patent application Ser. No. 14/640,832, entitled ADAPTIVE TISSUE COMPRESSION TECHNIQUES TO ADJUST CLOSURE RATES FOR MULTIPLE TISSUE TYPES, 2016/0256154;   U.S. patent application Ser. No. 14/640,935, entitled OVERLAID MULTI SENSOR RADIO FREQUENCY (RF) ELECTRODE SYSTEM TO MEASURE TISSUE, now U.S. Patent Application Publication No. 2016/0256071;   U.S. patent application Ser. No. 14/640,859, entitled TIME DEPENDENT EVALUATION OF SENSOR DATA TO DETERMINE STABILITY, CREEP, AND VISCOELASTIC ELEMENTS OF MEASURES, now U.S. Patent Application Publication No. 2016/0256187;   U.S. patent application Ser. No. 14/640,817, entitled INTERACTIVE FEEDBACK SYSTEM FOR POWERED SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2016/0256186;   U.S. patent application Ser. No. 14/640,844, entitled CONTROL TECHNIQUES AND SUB-PROCESSOR CONTAINED WITHIN MODULAR SHAFT WITH SELECT CONTROL PROCESSING FROM HANDLE, 2016/0256155;   U.S. patent application Ser. No. 14/640,837, entitled SMART SENSORS WITH LOCAL SIGNAL PROCESSING, now U.S. Patent Application Publication No. 2016/0256163;   U.S. patent application Ser. No. 14/640,780, entitled SURGICAL INSTRUMENT COMPRISING A LOCKABLE BATTERY HOUSING, now U.S. Patent Application Publication No. 2016/0256161;   U.S. patent application Ser. No. 14/640,765, entitled SYSTEM FOR DETECTING THE MIS-INSERTION OF A STAPLE CARTRIDGE INTO A SURGICAL STAPLER, now U.S. Patent Application Publication No. 2016/0256160; and   U.S. patent application Ser. No. 14/640,799, entitled SIGNAL AND POWER COMMUNICATION SYSTEM POSITIONED ON A ROTATABLE SHAFT, 2016/0256162.       

     Applicant of the present application owns the following patent applications that were filed on Feb. 27, 2015, and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/633,576, entitled SURGICAL INSTRUMENT SYSTEM COMPRISING AN INSPECTION STATION;   U.S. patent application Ser. No. 14/633,546, entitled SURGICAL APPARATUS CONFIGURED TO ASSESS WHETHER A PERFORMANCE PARAMETER OF THE SURGICAL APPARATUS IS WITHIN AN ACCEPTABLE PERFORMANCE BAND;   U.S. patent application Ser. No. 14/633,576, entitled SURGICAL CHARGING SYSTEM THAT CHARGES AND/OR CONDITIONS ONE OR MORE BATTERIES;   U.S. patent application Ser. No. 14/633,566, entitled CHARGING SYSTEM THAT ENABLES EMERGENCY RESOLUTIONS FOR CHARGING A BATTERY;   U.S. patent application Ser. No. 14/633,555, entitled SYSTEM FOR MONITORING WHETHER A SURGICAL INSTRUMENT NEEDS TO BE SERVICED;   U.S. patent application Ser. No. 14/633,542, entitled REINFORCED BATTERY FOR A SURGICAL INSTRUMENT;   U.S. patent application Ser. No. 14/633,548, entitled POWER ADAPTER FOR A SURGICAL INSTRUMENT;   U.S. patent application Ser. No. 14/633,526, entitled ADAPTABLE SURGICAL INSTRUMENT HANDLE;   U.S. patent application Ser. No. 14/633,541, entitled MODULAR STAPLING ASSEMBLY; and   U.S. patent application Ser. No. 14/633,562, entitled SURGICAL APPARATUS CONFIGURED TO TRACK AN END-OF-LIFE PARAMETER.       

     Applicant of the present application owns the following patent applications that were filed on Dec. 18, 2014 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/574,478, entitled SURGICAL INSTRUMENT SYSTEMS COMPRISING AN ARTICULATABLE END EFFECTOR AND MEANS FOR ADJUSTING THE FIRING STROKE OF A FIRING;   U.S. patent application Ser. No. 14/574,483, entitled SURGICAL INSTRUMENT ASSEMBLY COMPRISING LOCKABLE SYSTEMS;   U.S. patent application Ser. No. 14/575,139, entitled DRIVE ARRANGEMENTS FOR ARTICULATABLE SURGICAL INSTRUMENTS;   U.S. patent application Ser. No. 14/575,148, entitled LOCKING ARRANGEMENTS FOR DETACHABLE SHAFT ASSEMBLIES WITH ARTICULATABLE SURGICAL END EFFECTORS;   U.S. patent application Ser. No. 14/575,130, entitled SURGICAL INSTRUMENT WITH AN ANVIL THAT IS SELECTIVELY MOVABLE ABOUT A DISCRETE NON-MOVABLE AXIS RELATIVE TO A STAPLE CARTRIDGE;   U.S. patent application Ser. No. 14/575,143, entitled SURGICAL INSTRUMENTS WITH IMPROVED CLOSURE ARRANGEMENTS;   U.S. patent application Ser. No. 14/575,117, entitled SURGICAL INSTRUMENTS WITH ARTICULATABLE END EFFECTORS AND MOVABLE FIRING BEAM SUPPORT ARRANGEMENTS;   U.S. patent application Ser. No. 14/575,154, entitled SURGICAL INSTRUMENTS WITH ARTICULATABLE END EFFECTORS AND IMPROVED FIRING BEAM SUPPORT ARRANGEMENTS;   U.S. patent application Ser. No. 14/574,493, entitled SURGICAL INSTRUMENT ASSEMBLY COMPRISING A FLEXIBLE ARTICULATION SYSTEM; and   U.S. patent application Ser. No. 14/574,500, entitled SURGICAL INSTRUMENT ASSEMBLY COMPRISING A LOCKABLE ARTICULATION SYSTEM.       

     Applicant of the present application owns the following patent applications that were filed on Mar. 1, 2013 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 13/782,295, entitled ARTICULATABLE SURGICAL INSTRUMENTS WITH CONDUCTIVE PATHWAYS FOR SIGNAL COMMUNICATION, now U.S. Patent Application Publication No. 2014/0246471;   U.S. patent application Ser. No. 13/782,323, entitled ROTARY POWERED ARTICULATION JOINTS FOR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0246472;   U.S. patent application Ser. No. 13/782,338, entitled THUMBWHEEL SWITCH ARRANGEMENTS FOR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0249557;   U.S. patent application Ser. No. 13/782,499, entitled ELECTROMECHANICAL SURGICAL DEVICE WITH SIGNAL RELAY ARRANGEMENT, now U.S. Patent Application Publication No. 2014/0246474;   U.S. patent application Ser. No. 13/782,460, entitled MULTIPLE PROCESSOR MOTOR CONTROL FOR MODULAR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0246478;   U.S. patent application Ser. No. 13/782,358, entitled JOYSTICK SWITCH ASSEMBLIES FOR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0246477;   U.S. patent application Ser. No. 13/782,481, entitled SENSOR STRAIGHTENED END EFFECTOR DURING REMOVAL THROUGH TROCAR, now U.S. Patent Application Publication No. 2014/0246479;   U.S. patent application Ser. No. 13/782,518, entitled CONTROL METHODS FOR SURGICAL INSTRUMENTS WITH REMOVABLE IMPLEMENT PORTIONS, now U.S. Patent Application Publication No. 2014/0246475;   U.S. patent application Ser. No. 13/782,375, entitled ROTARY POWERED SURGICAL INSTRUMENTS WITH MULTIPLE DEGREES OF FREEDOM, now U.S. Patent Application Publication No. 2014/0246473; and   U.S. patent application Ser. No. 13/782,536, entitled SURGICAL INSTRUMENT SOFT STOP, now U.S. Patent Application Publication No. 2014/0246476.       

     Applicant of the present application also owns the following patent applications that were filed on Mar. 14, 2013 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 13/803,097, entitled ARTICULATABLE SURGICAL INSTRUMENT COMPRISING A FIRING DRIVE, now U.S. Patent Application Publication No. 2014/0263542;   U.S. patent application Ser. No. 13/803,193, entitled CONTROL ARRANGEMENTS FOR A DRIVE MEMBER OF A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0263537;   U.S. patent application Ser. No. 13/803,053, entitled INTERCHANGEABLE SHAFT ASSEMBLIES FOR USE WITH A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0263564;   U.S. patent application Ser. No. 13/803,086, entitled ARTICULATABLE SURGICAL INSTRUMENT COMPRISING AN ARTICULATION LOCK, now U.S. Patent Application Publication No. 2014/0263541;   U.S. patent application Ser. No. 13/803,210, entitled SENSOR ARRANGEMENTS FOR ABSOLUTE POSITIONING SYSTEM FOR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0263538;   U.S. patent application Ser. No. 13/803,148, entitled MULTI-FUNCTION MOTOR FOR A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0263554;   U.S. patent application Ser. No. 13/803,066, entitled DRIVE SYSTEM LOCKOUT ARRANGEMENTS FOR MODULAR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0263565;   U.S. patent application Ser. No. 13/803,117, entitled ARTICULATION CONTROL SYSTEM FOR ARTICULATABLE SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0263553;   U.S. patent application Ser. No. 13/803,130, entitled DRIVE TRAIN CONTROL ARRANGEMENTS FOR MODULAR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0263543; and   U.S. patent application Ser. No. 13/803,159, entitled METHOD AND SYSTEM FOR OPERATING A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0277017.       

     Applicant of the present application also owns the following patent application that was filed on Mar. 7, 2014 and is herein incorporated by reference in its entirety:
         U.S. patent application Ser. No. 14/200,111, entitled CONTROL SYSTEMS FOR SURGICAL INSTRUMENTS, now U.S. Patent Application Publication No. 2014/0263539.       

     Applicant of the present application also owns the following patent applications that were filed on Mar. 26, 2014 and are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/226,106, entitled POWER MANAGEMENT CONTROL SYSTEMS FOR SURGICAL INSTRUMENTS;   U.S. patent application Ser. No. 14/226,099, entitled STERILIZATION VERIFICATION CIRCUIT;   U.S. patent application Ser. No. 14/226,094, entitled VERIFICATION OF NUMBER OF BATTERY EXCHANGES/PROCEDURE COUNT;   U.S. patent application Ser. No. 14/226,117, entitled POWER MANAGEMENT THROUGH SLEEP OPTIONS OF SEGMENTED CIRCUIT AND WAKE UP CONTROL;   U.S. patent application Ser. No. 14/226,075, entitled MODULAR POWERED SURGICAL INSTRUMENT WITH DETACHABLE SHAFT ASSEMBLIES;   U.S. patent application Ser. No. 14/226,093, entitled FEEDBACK ALGORITHMS FOR MANUAL BAILOUT SYSTEMS FOR SURGICAL INSTRUMENTS;   U.S. patent application Ser. No. 14/226,116, entitled SURGICAL INSTRUMENT UTILIZING SENSOR ADAPTATION;   U.S. patent application Ser. No. 14/226,071, entitled SURGICAL INSTRUMENT CONTROL CIRCUIT HAVING A SAFETY PROCESSOR;   U.S. patent application Ser. No. 14/226,097, entitled SURGICAL INSTRUMENT COMPRISING INTERACTIVE SYSTEMS;   U.S. patent application Ser. No. 14/226,126, entitled INTERFACE SYSTEMS FOR USE WITH SURGICAL INSTRUMENTS;   U.S. patent application Ser. No. 14/226,133, entitled MODULAR SURGICAL INSTRUMENT SYSTEM;   U.S. patent application Ser. No. 14/226,081, entitled SYSTEMS AND METHODS FOR CONTROLLING A SEGMENTED CIRCUIT;   U.S. patent application Ser. No. 14/226,076, entitled POWER MANAGEMENT THROUGH SEGMENTED CIRCUIT AND VARIABLE VOLTAGE PROTECTION;   U.S. patent application Ser. No. 14/226,111, entitled SURGICAL STAPLING INSTRUMENT SYSTEM; and   U.S. patent application Ser. No. 14/226,125, entitled SURGICAL INSTRUMENT COMPRISING A ROTATABLE SHAFT.       

     Applicant of the present application also owns the following patent applications that were filed on Sep. 5, 2014 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/479,103, entitled CIRCUITRY AND SENSORS FOR POWERED MEDICAL DEVICE;   U.S. patent application Ser. No. 14/479,119, entitled ADJUNCT WITH INTEGRATED SENSORS TO QUANTIFY TISSUE COMPRESSION;   U.S. patent application Ser. No. 14/478,908, entitled MONITORING DEVICE DEGRADATION BASED ON COMPONENT EVALUATION;   U.S. patent application Ser. No. 14/478,895, entitled MULTIPLE SENSORS WITH ONE SENSOR AFFECTING A SECOND SENSOR&#39;S OUTPUT OR INTERPRETATION;   U.S. patent application Ser. No. 14/479,110, entitled USE OF POLARITY OF HALL MAGNET DETECTION TO DETECT MISLOADED CARTRIDGE;   U.S. patent application Ser. No. 14/479,098, entitled SMART CARTRIDGE WAKE UP OPERATION AND DATA RETENTION;   U.S. patent application Ser. No. 14/479,115, entitled MULTIPLE MOTOR CONTROL FOR POWERED MEDICAL DEVICE; and   U.S. patent application Ser. No. 14/479,108, entitled LOCAL DISPLAY OF TISSUE PARAMETER STABILIZATION.       

     Applicant of the present application also owns the following patent applications that were filed on Apr. 9, 2014 and which are each herein incorporated by reference in their respective entireties:
         U.S. patent application Ser. No. 14/248,590, entitled MOTOR DRIVEN SURGICAL INSTRUMENTS WITH LOCKABLE DUAL DRIVE SHAFTS, now U.S. Patent Application Publication No. 2014/0305987;   U.S. patent application Ser. No. 14/248,581, entitled SURGICAL INSTRUMENT COMPRISING A CLOSING DRIVE AND A FIRING DRIVE OPERATED FROM THE SAME ROTATABLE OUTPUT, now U.S. Patent Application Publication No. 2014/0305989;   U.S. patent application Ser. No. 14/248,595, entitled SURGICAL INSTRUMENT SHAFT INCLUDING SWITCHES FOR CONTROLLING THE OPERATION OF THE SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0305988;   U.S. patent application Ser. No. 14/248,588, entitled POWERED LINEAR SURGICAL STAPLER, now U.S. Patent Application Publication No. 2014/0309666;   U.S. patent application Ser. No. 14/248,591, entitled TRANSMISSION ARRANGEMENT FOR A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0305991;   U.S. patent application Ser. No. 14/248,584, entitled MODULAR MOTOR DRIVEN SURGICAL INSTRUMENTS WITH ALIGNMENT FEATURES FOR ALIGNING ROTARY DRIVE SHAFTS WITH SURGICAL END EFFECTOR SHAFTS, now U.S. Patent Application Publication No. 2014/0305994;   U.S. patent application Ser. No. 14/248,587, entitled POWERED SURGICAL STAPLER, now U.S. Patent Application Publication No. 2014/0309665;   U.S. patent application Ser. No. 14/248,586, entitled DRIVE SYSTEM DECOUPLING ARRANGEMENT FOR A SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2014/0305990; and   U.S. patent application Ser. No. 14/248,607, entitled MODULAR MOTOR DRIVEN SURGICAL INSTRUMENTS WITH STATUS INDICATION ARRANGEMENTS, now U.S. Patent Application Publication No. 2014/0305992.       

     Applicant of the present application also owns the following patent applications that were filed on Apr. 16, 2013 and which are each herein incorporated by reference in their respective entireties:
         U.S. Provisional Patent Application Ser. No. 61/812,365, entitled SURGICAL INSTRUMENT WITH MULTIPLE FUNCTIONS PERFORMED BY A SINGLE MOTOR;   U.S. Provisional Patent Application Ser. No. 61/812,376, entitled LINEAR CUTTER WITH POWER;   U.S. Provisional Patent Application Ser. No. 61/812,382, entitled LINEAR CUTTER WITH MOTOR AND PISTOL GRIP;   U.S. Provisional Patent Application Ser. No. 61/812,385, entitled SURGICAL INSTRUMENT HANDLE WITH MULTIPLE ACTUATION MOTORS AND MOTOR CONTROL; and   U.S. Provisional Patent Application Ser. No. 61/812,372, entitled SURGICAL INSTRUMENT WITH MULTIPLE FUNCTIONS PERFORMED BY A SINGLE MOTOR.       

     The present disclosure provides an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these aspects are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting examples. The features illustrated or described in connection with one example may be combined with the features of other examples. Such modifications and variations are intended to be included within the scope of the present disclosure. 
     Reference throughout the specification to “various aspects,” “some aspects,” “one aspect,” or “an aspect”, or the like, means that a particular feature, structure, or characteristic described in connection with the aspect is included in at least one aspect. Thus, appearances of the phrases “in various aspects,” “in some aspects,” “in one aspect”, or “in an aspect”, or the like, in places throughout the specification are not necessarily all referring to the same aspect. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more aspects. Thus, the particular features, structures, or characteristics illustrated or described in connection with one aspect may be combined, in whole or in part, with the features structures, or characteristics of one or more other aspects without limitation. Such modifications and variations are intended to be included within the scope of the present disclosure. 
     The terms “proximal” and “distal” are used herein with reference to a clinician manipulating the handle portion of the surgical instrument. The term “proximal” referring to the portion closest to the clinician and the term “distal” referring to the portion located away from the clinician. It will be further appreciated that, for convenience and clarity, spatial terms such as “vertical,” “horizontal,” “up,” and “down” may be used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and/or absolute. 
     Various example devices and methods are provided for performing laparoscopic and minimally invasive surgical procedures. However, the person of ordinary skill in the art will readily appreciate that the various methods and devices disclosed herein can be used in numerous surgical procedures and applications including, for example, in connection with open surgical procedures. As the present Detailed Description proceeds, those of ordinary skill in the art will further appreciate that the various instruments disclosed herein can be inserted into a body in any way, such as through a natural orifice, through an incision or puncture hole formed in tissue, etc. The working portions or end effector portions of the instruments can be inserted directly into a patient&#39;s body or can be inserted through an access device that has a working channel through which the end effector and elongated shaft of a surgical instrument can be advanced. 
       FIGS. 1-6  depict a motor-driven surgical cutting and fastening instrument  10  that may or may not be reused. In the illustrated examples, the instrument  10  includes a housing  12  that comprises a handle assembly  14  that is configured to be grasped, manipulated and actuated by the clinician. The housing  12  is configured for operable attachment to an interchangeable shaft assembly  200  that has a surgical end effector  300  operably coupled thereto that is configured to perform one or more surgical tasks or procedures. As the present Detailed Description proceeds, it will be understood that the various unique and novel arrangements of the various forms of interchangeable shaft assemblies disclosed herein also may be effectively employed in connection with robotically-controlled surgical systems. Thus, the term “housing” also may encompass a housing or similar portion of a robotic system that houses or otherwise operably supports at least one drive system that is configured to generate and apply at least one control motion which could be used to actuate the interchangeable shaft assemblies disclosed herein and their respective equivalents. The term “frame” may refer to a portion of a handheld surgical instrument. The term “frame” also may represent a portion of a robotically controlled surgical instrument and/or a portion of the robotic system that may be used to operably control a surgical instrument. For example, the interchangeable shaft assemblies disclosed herein may be employed with various robotic systems, instruments, components and methods disclosed in U.S. patent application Ser. No. 13/118,241, entitled SURGICAL STAPLING INSTRUMENTS WITH ROTATABLE STAPLE DEPLOYMENT ARRANGEMENTS, now U.S. Patent Application Publication No. US 2012/0298719. U.S. patent application Ser. No. 13/118,241, entitled SURGICAL STAPLING INSTRUMENTS WITH ROTATABLE STAPLE DEPLOYMENT ARRANGEMENTS, now U.S. Patent Application Publication No. US 2012/0298719, is incorporated by reference herein in its entirety. 
     The housing  12  depicted in  FIGS. 1-3  is shown in connection with an interchangeable shaft assembly  200  that includes an end effector  300  that comprises a surgical cutting and fastening device that is configured to operably support a surgical staple cartridge  304  therein. The housing  12  may be configured for use in connection with interchangeable shaft assemblies that include end effectors that are adapted to support different sizes and types of staple cartridges, have different shaft lengths, sizes, and types, etc. In addition, the housing  12  also may be effectively employed with a variety of other interchangeable shaft assemblies including those assemblies that are configured to apply other motions and forms of energy such as, for example, radio frequency (RF) energy, ultrasonic energy and/or motion to end effector arrangements adapted for use in connection with various surgical applications and procedures. Furthermore, the end effectors, shaft assemblies, handles, surgical instruments, and/or surgical instrument systems can utilize any suitable fastener, or fasteners, to fasten tissue. For instance, a fastener cartridge comprising a plurality of fasteners removably stored therein can be removably inserted into and/or attached to the end effector of a shaft assembly. 
       FIG. 1  illustrates the surgical instrument  10  with an interchangeable shaft assembly  200  operably coupled thereto.  FIGS. 2 and 3  illustrate attachment of the interchangeable shaft assembly  200  to the housing  12  or handle assembly  14 . As shown in  FIG. 4 , the handle assembly  14  may comprise a pair of interconnectable handle housing segments  16  and  18  that may be interconnected by screws, snap features, adhesive, etc. In the illustrated arrangement, the handle housing segments  16 ,  18  cooperate to form a pistol grip portion  19  that can be gripped and manipulated by the clinician. As will be discussed in further detail below, the handle assembly  14  operably supports a plurality of drive systems therein that are configured to generate and apply various control motions to corresponding portions of the interchangeable shaft assembly that is operably attached thereto. 
     Referring now to  FIG. 4 , the handle assembly  14  may further include a frame  20  that operably supports a plurality of drive systems. For example, the frame  20  can operably support a “first” or closure drive system, generally designated as  30 , which may be employed to apply closing and opening motions to the interchangeable shaft assembly  200  that is operably attached or coupled thereto. In at least one form, the closure drive system  30  may include an actuator in the form of a closure trigger  32  that is pivotally supported by the frame  20 . More specifically, as illustrated in  FIG. 4 , the closure trigger  32  is pivotally coupled to the housing  14  by a pin  33 . Such arrangement enables the closure trigger  32  to be manipulated by a clinician such that when the clinician grips the pistol grip portion  19  of the handle assembly  14 , the closure trigger  32  may be easily pivoted from a starting or “unactuated” position to an “actuated” position and more particularly to a fully compressed or fully actuated position. The closure trigger  32  may be biased into the unactuated position by spring or other biasing arrangement (not shown). In various forms, the closure drive system  30  further includes a closure linkage assembly  34  that is pivotally coupled to the closure trigger  32 . As shown in  FIG. 4 , the closure linkage assembly  34  may include a first closure link  36  and a second closure link  38  that are pivotally coupled to the closure trigger  32  by a pin  35 . The second closure link  38  also may be referred to herein as an “attachment member” and include a transverse attachment pin  37 . 
     Still referring to  FIG. 4 , it can be observed that the first closure link  36  may have a locking wall or end  39  thereon that is configured to cooperate with a closure release assembly  60  that is pivotally coupled to the frame  20 . In at least one form, the closure release assembly  60  may comprise a release button assembly  62  that has a distally protruding locking pawl  64  formed thereon. The release button assembly  62  may be pivoted in a counterclockwise direction by a release spring (not shown). As the clinician depresses the closure trigger  32  from its unactuated position towards the pistol grip portion  19  of the handle assembly  14 , the first closure link  36  pivots upward to a point wherein the locking pawl  64  drops into retaining engagement with the locking wall  39  on the first closure link  36  thereby preventing the closure trigger  32  from returning to the unactuated position. See  FIG. 18 . Thus, the closure release assembly  60  serves to lock the closure trigger  32  in the fully actuated position. When the clinician desires to unlock the closure trigger  32  to permit it to be biased to the unactuated position, the clinician simply pivots the closure release button assembly  62  such that the locking pawl  64  is moved out of engagement with the locking wall  39  on the first closure link  36 . When the locking pawl  64  has been moved out of engagement with the first closure link  36 , the closure trigger  32  may pivot back to the unactuated position. Other closure trigger locking and release arrangements also may be employed. 
     Further to the above,  FIGS. 13-15  illustrate the closure trigger  32  in its unactuated position which is associated with an open, or unclamped, configuration of the shaft assembly  200  in which tissue can be positioned between the jaws of the shaft assembly  200 .  FIGS. 16-18  illustrate the closure trigger  32  in its actuated position which is associated with a closed, or clamped, configuration of the shaft assembly  200  in which tissue is clamped between the jaws of the shaft assembly  200 . Upon comparing  FIGS. 14 and 17 , the reader will appreciate that, when the closure trigger  32  is moved from its unactuated position ( FIG. 14 ) to its actuated position ( FIG. 17 ), the closure release button  62  is pivoted between a first position ( FIG. 14 ) and a second position ( FIG. 17 ). The rotation of the closure release button  62  can be referred to as being an upward rotation; however, at least a portion of the closure release button  62  is being rotated toward the circuit board  100 . Referring to  FIG. 4 , the closure release button  62  can include an arm  61  extending therefrom and a magnetic element  63 , such as a permanent magnet, for example, mounted to the arm  61 . When the closure release button  62  is rotated from its first position to its second position, the magnetic element  63  can move toward the circuit board  100 . The circuit board  100  can include at least one sensor configured to detect the movement of the magnetic element  63 . In at least one aspect, a magnetic field sensor  65 , for example, can be mounted to the bottom surface of the circuit board  100 . The magnetic field sensor  65  can be configured to detect changes in a magnetic field surrounding the magnetic field sensor  65  caused by the movement of the magnetic element  63 . The magnetic field sensor  65  can be in signal communication with a microcontroller  1500  ( FIG. 19 ), for example, which can determine whether the closure release button  62  is in its first position, which is associated with the unactuated position of the closure trigger  32  and the open configuration of the end effector, its second position, which is associated with the actuated position of the closure trigger  32  and the closed configuration of the end effector, and/or any position between the first position and the second position. 
     As used throughout the present disclosure, a magnetic field sensor may be a Hall effect sensor, search coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, magnetostrictive/piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic, and microelectromechanical systems-based magnetic sensors, among others. 
     In at least one form, the handle assembly  14  and the frame  20  may operably support another drive system referred to herein as a firing drive system  80  that is configured to apply firing motions to corresponding portions of the interchangeable shaft assembly attached thereto. The firing drive system may  80  also be referred to herein as a “second drive system”. The firing drive system  80  may employ an electric motor  82 , located in the pistol grip portion  19  of the handle assembly  14 . In various forms, the motor  82  may be a DC brushed driving motor having a maximum rotation of, approximately, 25,000 RPM, for example. In other arrangements, the motor may include a brushless motor, a cordless motor, a synchronous motor, a stepper motor, or any other suitable electric motor. The motor  82  may be powered by a power source  90  that in one form may comprise a removable power pack  92 . As shown in  FIG. 4 , for example, the power pack  92  may comprise a proximal housing portion  94  that is configured for attachment to a distal housing portion  96 . The proximal housing portion  94  and the distal housing portion  96  are configured to operably support a plurality of batteries  98  therein. Batteries  98  may each comprise, for example, a Lithium Ion (“LI”) or other suitable battery. The distal housing portion  96  is configured for removable operable attachment to a control circuit board assembly  100  which is also operably coupled to the motor  82 . A number of batteries  98  may be connected in series may be used as the power source for the surgical instrument  10 . In addition, the power source  90  may be replaceable and/or rechargeable. 
     As outlined above with respect to other various forms, the electric motor  82  can include a rotatable shaft (not shown) that operably interfaces with a gear reducer assembly  84  that is mounted in meshing engagement with a with a set, or rack, of drive teeth  122  on a longitudinally-movable drive member  120 . In use, a voltage polarity provided by the power source  90  can operate the electric motor  82  in a clockwise direction wherein the voltage polarity applied to the electric motor by the battery can be reversed in order to operate the electric motor  82  in a counter-clockwise direction. When the electric motor  82  is rotated in one direction, the drive member  120  will be axially driven in the distal direction “DD”. When the motor  82  is driven in the opposite rotary direction, the drive member  120  will be axially driven in a proximal direction “PD”. The handle assembly  14  can include a switch which can be configured to reverse the polarity applied to the electric motor  82  by the power source  90 . As with the other forms described herein, the handle assembly  14  can also include a sensor that is configured to detect the position of the drive member  120  and/or the direction in which the drive member  120  is being moved. 
     Actuation of the motor  82  can be controlled by a firing trigger  130  that is pivotally supported on the handle assembly  14 . The firing trigger  130  may be pivoted between an unactuated position and an actuated position. The firing trigger  130  may be biased into the unactuated position by a spring  132  or other biasing arrangement such that when the clinician releases the firing trigger  130 , it may be pivoted or otherwise returned to the unactuated position by the spring  132  or biasing arrangement. In at least one form, the firing trigger  130  can be positioned “outboard” of the closure trigger  32  as was discussed above. In at least one form, a firing trigger safety button  134  may be pivotally mounted to the closure trigger  32  by pin  35 . The safety button  134  may be positioned between the firing trigger  130  and the closure trigger  32  and have a pivot arm  136  protruding therefrom. See  FIG. 4 . When the closure trigger  32  is in the unactuated position, the safety button  134  is contained in the handle assembly  14  where the clinician cannot readily access it and move it between a safety position preventing actuation of the firing trigger  130  and a firing position wherein the firing trigger  130  may be fired. As the clinician depresses the closure trigger  32 , the safety button  134  and the firing trigger  130  pivot down wherein they can then be manipulated by the clinician. 
     As discussed above, the handle assembly  14  can include a closure trigger  32  and a firing trigger  130 . Referring to  FIGS. 14-18A , the firing trigger  130  can be pivotably mounted to the closure trigger  32 . The closure trigger  32  can include an arm  31  extending therefrom and the firing trigger  130  can be pivotably mounted to the arm  31  about a pivot pin  33 . When the closure trigger  32  is moved from its unactuated position ( FIG. 14 ) to its actuated position ( FIG. 17 ), the firing trigger  130  can descend downwardly, as outlined above. After the safety button  134  has been moved to its firing position, referring primarily to  FIG. 18A , the firing trigger  130  can be depressed to operate the motor of the surgical instrument firing system. In various instances, the handle assembly  14  can include a tracking system, such as system  800 , for example, configured to determine the position of the closure trigger  32  and/or the position of the firing trigger  130 . With primary reference to  FIGS. 14, 17, and 18A , the tracking system  800  can include a magnetic element, such as permanent magnet  802 , for example, which is mounted to an arm  801  extending from the firing trigger  130 . The tracking system  800  can comprise one or more sensors, such as a first magnetic field sensor  803  and a second magnetic field sensor  804 , for example, which can be configured to track the position of the magnet  802 . 
     Upon comparing  FIGS. 14 and 17 , the reader will appreciate that, when the closure trigger  32  is moved from its unactuated position to its actuated position, the magnet  802  can move between a first position adjacent the first magnetic field sensor  803  and a second position adjacent the second magnetic field sensor  804 . 
     Upon comparing  FIGS. 17 and 18A , the reader will further appreciate that, when the firing trigger  130  is moved from an unfired position ( FIG. 17 ) to a fired position ( FIG. 18A ), the magnet  802  can move relative to the second magnetic field sensor  804 . The sensors  803  and  804  can track the movement of the magnet  802  and can be in signal communication with a microcontroller on the circuit board  100 . With data from the first sensor  803  and/or the second sensor  804 , the microcontroller can determine the position of the magnet  802  along a predefined path and, based on that position, the microcontroller can determine whether the closure trigger  32  is in its unactuated position, its actuated position, or a position therebetween. Similarly, with data from the first sensor  803  and/or the second sensor  804 , the microcontroller can determine the position of the magnet  802  along a predefined path and, based on that position, the microcontroller can determine whether the firing trigger  130  is in its unfired position, its fully fired position, or a position therebetween. 
     As indicated above, in at least one form, the longitudinally movable drive member  120  has a rack of teeth  122  formed thereon for meshing engagement with a corresponding drive gear  86  of the gear reducer assembly  84 . At least one form also includes a manually-actuatable “bailout” assembly  140  that is configured to enable the clinician to manually retract the longitudinally movable drive member  120  should the motor  82  become disabled. The bailout assembly  140  may include a lever or bailout handle assembly  14  that is configured to be manually pivoted into ratcheting engagement with teeth  124  also provided in the drive member  120 . Thus, the clinician can manually retract the drive member  120  by using the bailout handle assembly  14  to ratchet the drive member  120  in the proximal direction “PD”. U.S. Patent Application Publication No. US 2010/0089970, now U.S. Pat. No. 8,608,045 discloses bailout arrangements and other components, arrangements and systems that also may be employed with the various instruments disclosed herein. U.S. patent application Ser. No. 12/249,117, entitled POWERED SURGICAL CUTTING AND STAPLING APPARATUS WITH MANUALLY RETRACTABLE FIRING SYSTEM, U.S. Patent Application Publication No. 2010/0089970, now U.S. Pat. No. 8,608,045, is hereby incorporated by reference in its entirety. 
     Turning now to  FIGS. 1 and 7 , the interchangeable shaft assembly  200  includes a surgical end effector  300  that comprises an elongated channel  302  that is configured to operably support a staple cartridge  304  therein. The end effector  300  may further include an anvil  306  that is pivotally supported relative to the elongated channel  302 . The interchangeable shaft assembly  200  may further include an articulation joint  270  and an articulation lock  350  ( FIG. 8 ) which can be configured to releasably hold the end effector  300  in a desired position relative to a shaft axis SA-SA. Details regarding the construction and operation of the end effector  300 , the articulation joint  270  and the articulation lock  350  are set forth in U.S. patent application Ser. No. 13/803,086, filed Mar. 14, 2013, entitled ARTICULATABLE SURGICAL INSTRUMENT COMPRISING AN ARTICULATION LOCK, now U.S. Patent Application Publication No. 2014/0263541. The entire disclosure of U.S. patent application Ser. No. 13/803,086, filed Mar. 14, 2013, entitled ARTICULATABLE SURGICAL INSTRUMENT COMPRISING AN ARTICULATION LOCK, now U.S. Patent Application Publication No. 2014/0263541, is hereby incorporated by reference herein. As shown in  FIGS. 7 and 8 , the interchangeable shaft assembly  200  can further include a proximal housing or nozzle  201  comprised of nozzle portions  202  and  203 . The interchangeable shaft assembly  200  can further include a closure tube  260  which can be utilized to close and/or open the anvil  306  of the end effector  300 . Primarily referring now to  FIGS. 8 and 9 , the shaft assembly  200  can include a spine  210  which can be configured to fixably support a shaft frame portion  212  of the articulation lock  350 . See  FIG. 8 . The spine  210  can be configured to, one, slidably support a firing member  220  therein and, two, slidably support the closure tube  260  which extends around the spine  210 . The spine  210  can also be configured to slidably support a proximal articulation driver  230 . The articulation driver  230  has a distal end  231  that is configured to operably engage the articulation lock  350 . The articulation lock  350  interfaces with an articulation frame  352  that is adapted to operably engage a drive pin (not shown) on the end effector frame (not shown). As indicated above, further details regarding the operation of the articulation lock  350  and the articulation frame may be found in U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541. In various circumstances, the spine  210  can comprise a proximal end  211  which is rotatably supported in a chassis  240 . In one arrangement, for example, the proximal end  211  of the spine  210  has a thread  214  formed thereon for threaded attachment to a spine bearing  216  configured to be supported within the chassis  240 . See  FIG. 7 . Such an arrangement facilitates rotatable attachment of the spine  210  to the chassis  240  such that the spine  210  may be selectively rotated about a shaft axis SA-SA relative to the chassis  240 . 
     Referring primarily to  FIG. 7 , the interchangeable shaft assembly  200  includes a closure shuttle  250  that is slidably supported within the chassis  240  such that it may be axially moved relative thereto. As shown in  FIGS. 3 and 7 , the closure shuttle  250  includes a pair of proximally-protruding hooks  252  that are configured for attachment to the attachment pin  37  that is attached to the second closure link  38  as will be discussed in further detail below. A proximal end  261  of the closure tube  260  is coupled to the closure shuttle  250  for relative rotation thereto. For example, a U shaped connector  263  is inserted into an annular slot  262  in the proximal end  261  of the closure tube  260  and is retained within vertical slots  253  in the closure shuttle  250 . See  FIG. 7 . Such an arrangement serves to attach the closure tube  260  to the closure shuttle  250  for axial travel therewith while enabling the closure tube  260  to rotate relative to the closure shuttle  250  about the shaft axis SA-SA. A closure spring  268  is journaled on the closure tube  260  and serves to bias the closure tube  260  in the proximal direction “PD” which can serve to pivot the closure trigger into the unactuated position when the shaft assembly is operably coupled to the handle assembly  14 . 
     In at least one form, the interchangeable shaft assembly  200  may further include an articulation joint  270 . Other interchangeable shaft assemblies, however, may not be capable of articulation. As shown in  FIG. 7 , for example, the articulation joint  270  includes a double pivot closure sleeve assembly  271 . According to various forms, the double pivot closure sleeve assembly  271  includes an end effector closure sleeve assembly  272  having upper and lower distally projecting tangs  273 ,  274 . An end effector closure sleeve assembly  272  includes a horseshoe aperture  275  and a tab  276  for engaging an opening tab on the anvil  306  in the various manners described in U.S. patent application Ser. No. 13/803,086, filed Mar. 14, 2013, entitled ARTICULATABLE SURGICAL INSTRUMENT COMPRISING AN ARTICULATION LOCK, now U.S. Patent Application Publication No. 2014/0263541, which has been incorporated by reference herein. As described in further detail therein, the horseshoe aperture  275  and tab  276  engage a tab on the anvil when the anvil  306  is opened. An upper double pivot link  277  includes upwardly projecting distal and proximal pivot pins that engage respectively an upper distal pin hole in the upper proximally projecting tang  273  and an upper proximal pin hole in an upper distally projecting tang  264  on the closure tube  260 . A lower double pivot link  278  includes upwardly projecting distal and proximal pivot pins that engage respectively a lower distal pin hole in the lower proximally projecting tang  274  and a lower proximal pin hole in the lower distally projecting tang  265 . See also  FIG. 8 . 
     In use, the closure tube  260  is translated distally (direction “DD”) to close the anvil  306 , for example, in response to the actuation of the closure trigger  32 . The anvil  306  is closed by distally translating the closure tube  260  and thus the shaft closure sleeve assembly  272 , causing it to strike a proximal surface on the anvil  360  in the manner described in the aforementioned reference U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541. As was also described in detail in that reference, the anvil  306  is opened by proximally translating the closure tube  260  and the shaft closure sleeve assembly  272 , causing tab  276  and the horseshoe aperture  275  to contact and push against the anvil tab to lift the anvil  306 . In the anvil-open position, the shaft closure tube  260  is moved to its proximal position. 
     As indicated above, the surgical instrument  10  may further include an articulation lock  350  of the types and construction described in further detail in U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541, which can be configured and operated to selectively lock the end effector  300  in position. Such arrangement enables the end effector  300  to be rotated, or articulated, relative to the shaft closure tube  260  when the articulation lock  350  is in its unlocked state. In such an unlocked state, the end effector  300  can be positioned and pushed against soft tissue and/or bone, for example, surrounding the surgical site within the patient in order to cause the end effector  300  to articulate relative to the closure tube  260 . The end effector  300  also may be articulated relative to the closure tube  260  by an articulation driver  230 . 
     As was also indicated above, the interchangeable shaft assembly  200  further includes a firing member  220  that is supported for axial travel within the shaft spine  210 . The firing member  220  includes an intermediate firing shaft portion  222  that is configured for attachment to a distal cutting portion or knife bar  280 . The firing member  220  also may be referred to herein as a “second shaft” and/or a “second shaft assembly”. As shown in  FIGS. 8 and 9 , the intermediate firing shaft portion  222  may include a longitudinal slot  223  in the distal end thereof which can be configured to receive a tab  284  on the proximal end  282  of the distal knife bar  280 . The longitudinal slot  223  and the proximal end  282  can be sized and configured to permit relative movement therebetween and can comprise a slip joint  286 . The slip joint  286  can permit the intermediate firing shaft portion  222  of the firing drive  220  to be moved to articulate the end effector  300  without moving, or at least substantially moving, the knife bar  280 . Once the end effector  300  has been suitably oriented, the intermediate firing shaft portion  222  can be advanced distally until a proximal sidewall of the longitudinal slot  223  comes into contact with the tab  284  in order to advance the knife bar  280  and fire the staple cartridge positioned within the channel  302  As can be further seen in  FIGS. 8 and 9 , the shaft spine  210  has an elongate opening or window  213  therein to facilitate assembly and insertion of the intermediate firing shaft portion  222  into the shaft frame  210 . Once the intermediate firing shaft portion  222  has been inserted therein, a top frame segment  215  may be engaged with the shaft frame  212  to enclose the intermediate firing shaft portion  222  and knife bar  280  therein. Further description of the operation of the firing member  220  may be found in U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541. 
     Further to the above, the shaft assembly  200  can include a clutch assembly  400  which can be configured to selectively and releasably couple the articulation driver  230  to the firing member  220 . In one form, the clutch assembly  400  includes a lock collar, or sleeve  402 , positioned around the firing member  220  wherein the lock sleeve  402  can be rotated between an engaged position in which the lock sleeve  402  couples the articulation driver  360  to the firing member  220  and a disengaged position in which the articulation driver  360  is not operably coupled to the firing member  200 . When lock sleeve  402  is in its engaged position, distal movement of the firing member  220  can move the articulation driver  360  distally and, correspondingly, proximal movement of the firing member  220  can move the articulation driver  230  proximally. When lock sleeve  402  is in its disengaged position, movement of the firing member  220  is not transmitted to the articulation driver  230  and, as a result, the firing member  220  can move independently of the articulation driver  230 . In various circumstances, the articulation driver  230  can be held in position by the articulation lock  350  when the articulation driver  230  is not being moved in the proximal or distal directions by the firing member  220 . 
     Referring primarily to  FIG. 9 , the lock sleeve  402  can comprise a cylindrical, or an at least substantially cylindrical, body including a longitudinal aperture  403  defined therein configured to receive the firing member  220 . The lock sleeve  402  can comprise diametrically-opposed, inwardly-facing lock protrusions  404  and an outwardly-facing lock member  406 . The lock protrusions  404  can be configured to be selectively engaged with the firing member  220 . More particularly, when the lock sleeve  402  is in its engaged position, the lock protrusions  404  are positioned within a drive notch  224  defined in the firing member  220  such that a distal pushing force and/or a proximal pulling force can be transmitted from the firing member  220  to the lock sleeve  402 . When the lock sleeve  402  is in its engaged position, the second lock member  406  is received within a drive notch  232  defined in the articulation driver  230  such that the distal pushing force and/or the proximal pulling force applied to the lock sleeve  402  can be transmitted to the articulation driver  230 . In effect, the firing member  220 , the lock sleeve  402 , and the articulation driver  230  will move together when the lock sleeve  402  is in its engaged position. On the other hand, when the lock sleeve  402  is in its disengaged position, the lock protrusions  404  may not be positioned within the drive notch  224  of the firing member  220  and, as a result, a distal pushing force and/or a proximal pulling force may not be transmitted from the firing member  220  to the lock sleeve  402 . Correspondingly, the distal pushing force and/or the proximal pulling force may not be transmitted to the articulation driver  230 . In such circumstances, the firing member  220  can be slid proximally and/or distally relative to the lock sleeve  402  and the proximal articulation driver  230 . 
     As shown in  FIGS. 8-12 , the shaft assembly  200  further includes a switch drum  500  that is rotatably received on the closure tube  260 . The switch drum  500  comprises a hollow shaft segment  502  that has a shaft boss  504  formed thereon for receive an outwardly protruding actuation pin  410  therein. In various circumstances, the actuation pin  410  extends through a slot  267  into a longitudinal slot  408  provided in the lock sleeve  402  to facilitate axial movement of the lock sleeve  402  when it is engaged with the articulation driver  230 . A rotary torsion spring  420  is configured to engage the boss  504  on the switch drum  500  and a portion of the nozzle housing  203  as shown in  FIG. 10  to apply a biasing force to the switch drum  500 . The switch drum  500  can further comprise at least partially circumferential openings  506  defined therein which, referring to  FIGS. 5 and 6 , can be configured to receive circumferential mounts  204 ,  205  extending from the nozzle halves  202 ,  203  and permit relative rotation, but not translation, between the switch drum  500  and the proximal nozzle  201 . As shown in those Figures, the mounts  204  and  205  also extend through openings  266  in the closure tube  260  to be seated in recesses  211  in the shaft spine  210 . However, rotation of the nozzle  201  to a point where the mounts  204 ,  205  reach the end of their respective slots  506  in the switch drum  500  will result in rotation of the switch drum  500  about the shaft axis SA-SA. Rotation of the switch drum  500  will ultimately result in the rotation of eth actuation pin  410  and the lock sleeve  402  between its engaged and disengaged positions. Thus, in essence, the nozzle  201  may be employed to operably engage and disengage the articulation drive system with the firing drive system in the various manners described in further detail in U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541. 
     As also illustrated in  FIGS. 8-12 , the shaft assembly  200  can comprise a slip ring assembly  600  which can be configured to conduct electrical power to and/or from the end effector  300  and/or communicate signals to and/or from the end effector  300 , for example. The slip ring assembly  600  can comprise a proximal connector flange  604  mounted to a chassis flange  242  extending from the chassis  240  and a distal connector flange  601  positioned within a slot defined in the shaft housings  202 ,  203 . The proximal connector flange  604  can comprise a first face and the distal connector flange  601  can comprise a second face which is positioned adjacent to and movable relative to the first face. The distal connector flange  601  can rotate relative to the proximal connector flange  604  about the shaft axis SA-SA. The proximal connector flange  604  can comprise a plurality of concentric, or at least substantially concentric, conductors  602  defined in the first face thereof. A connector  607  can be mounted on the proximal side of the connector flange  601  and may have a plurality of contacts (not shown) wherein each contact corresponds to and is in electrical contact with one of the conductors  602 . Such an arrangement permits relative rotation between the proximal connector flange  604  and the distal connector flange  601  while maintaining electrical contact therebetween. The proximal connector flange  604  can include an electrical connector  606  which can place the conductors  602  in signal communication with a shaft circuit board  610  mounted to the shaft chassis  240 , for example. In at least one instance, a wiring harness comprising a plurality of conductors can extend between the electrical connector  606  and the shaft circuit board  610 . The electrical connector  606  may extend proximally through a connector opening  243  defined in the chassis mounting flange  242 . See  FIG. 7 . U.S. patent application Ser. No. 13/800,067, entitled STAPLE CARTRIDGE TISSUE THICKNESS SENSOR SYSTEM, filed on Mar. 13, 2013, now U.S. Patent Application Publication No. 2014/0263552, is incorporated by reference in its entirety. U.S. patent application Ser. No. 13/800,025, entitled STAPLE CARTRIDGE TISSUE THICKNESS SENSOR SYSTEM, filed on Mar. 13, 2013, now U.S. Patent Application Publication No. 2014/0263551, is incorporated by reference in its entirety. Further details regarding slip ring assembly  600  may be found in U.S. patent application Ser. No. 13/803,086, now U.S. Patent Application Publication No. 2014/0263541. 
     As discussed above, the shaft assembly  200  can include a proximal portion which is fixably mounted to the handle assembly  14  and a distal portion which is rotatable about a longitudinal axis. The rotatable distal shaft portion can be rotated relative to the proximal portion about the slip ring assembly  600 , as discussed above. The distal connector flange  601  of the slip ring assembly  600  can be positioned within the rotatable distal shaft portion. Moreover, further to the above, the switch drum  500  can also be positioned within the rotatable distal shaft portion. When the rotatable distal shaft portion is rotated, the distal connector flange  601  and the switch drum  500  can be rotated synchronously with one another. In addition, the switch drum  500  can be rotated between a first position and a second position relative to the distal connector flange  601 . When the switch drum  500  is in its first position, the articulation drive system may be operably disengaged from the firing drive system and, thus, the operation of the firing drive system may not articulate the end effector  300  of the shaft assembly  200 . When the switch drum  500  is in its second position, the articulation drive system may be operably engaged with the firing drive system and, thus, the operation of the firing drive system may articulate the end effector  300  of the shaft assembly  200 . When the switch drum  500  is moved between its first position and its second position, the switch drum  500  is moved relative to distal connector flange  601 . In various instances, the shaft assembly  200  can comprise at least one sensor configured to detect the position of the switch drum  500 . Turning now to  FIGS. 11 and 12 , the distal connector flange  601  can comprise a magnetic field sensor  605 , for example, and the switch drum  500  can comprise a magnetic element, such as permanent magnet  505 , for example. The magnetic field sensor  605  can be configured to detect the position of the permanent magnet  505 . When the switch drum  500  is rotated between its first position and its second position, the permanent magnet  505  can move relative to the magnetic field sensor  605 . In various instances, magnetic field sensor  605  can detect changes in a magnetic field created when the permanent magnet  505  is moved. The magnetic field sensor  605  can be in signal communication with the shaft circuit board  610  and/or the handle circuit board  100 , for example. Based on the signal from the magnetic field sensor  605 , a microcontroller on the shaft circuit board  610  and/or the handle circuit board  100  can determine whether the articulation drive system is engaged with or disengaged from the firing drive system. 
     Referring again to  FIGS. 3 and 7 , the chassis  240  includes at least one, and preferably two, tapered attachment portions  244  formed thereon that are adapted to be received within corresponding dovetail slots  702  formed within a distal attachment flange portion  700  of the frame  20 . Each dovetail slot  702  may be tapered or, stated another way, be somewhat V-shaped to seatingly receive the attachment portions  244  therein. As can be further seen in  FIGS. 3 and 7 , a shaft attachment lug  226  is formed on the proximal end of the intermediate firing shaft  222 . As will be discussed in further detail below, when the interchangeable shaft assembly  200  is coupled to the handle assembly  14 , the shaft attachment lug  226  is received in a firing shaft attachment cradle  126  formed in the distal end  125  of the longitudinal drive member  120  as shown in  FIGS. 3 and 6 , for example. 
     Various shaft assemblies employ a latch system  710  for removably coupling the shaft assembly  200  to the housing  12  and more specifically to the frame  20 . As shown in  FIG. 7 , for example, in at least one form, the latch system  710  includes a lock member or lock yoke  712  that is movably coupled to the chassis  240 . In the illustrated example, for example, the lock yoke  712  has a U-shape with two spaced downwardly extending legs  714 . The legs  714  each have a pivot lug  716  formed thereon that are adapted to be received in corresponding holes  245  formed in the chassis  240 . Such arrangement facilitates pivotal attachment of the lock yoke  712  to the chassis  240 . The lock yoke  712  may include two proximally protruding lock lugs  714  that are configured for releasable engagement with corresponding lock detents or grooves  704  in the distal attachment flange  700  of the frame  20 . See  FIG. 3 . In various forms, the lock yoke  712  is biased in the proximal direction by spring or biasing member (not shown). Actuation of the lock yoke  712  may be accomplished by a latch button  722  that is slidably mounted on a latch actuator assembly  720  that is mounted to the chassis  240 . The latch button  722  may be biased in a proximal direction relative to the lock yoke  712 . As will be discussed in further detail below, the lock yoke  712  may be moved to an unlocked position by biasing the latch button the in distal direction which also causes the lock yoke  712  to pivot out of retaining engagement with the distal attachment flange  700  of the frame  20 . When the lock yoke  712  is in “retaining engagement” with the distal attachment flange  700  of the frame  20 , the lock lugs  716  are retainingly seated within the corresponding lock detents or grooves  704  in the distal attachment flange  700 . 
     When employing an interchangeable shaft assembly that includes an end effector of the type described herein that is adapted to cut and fasten tissue, as well as other types of end effectors, it may be desirable to prevent inadvertent detachment of the interchangeable shaft assembly from the housing during actuation of the end effector. For example, in use the clinician may actuate the closure trigger  32  to grasp and manipulate the target tissue into a desired position. Once the target tissue is positioned within the end effector  300  in a desired orientation, the clinician may then fully actuate the closure trigger  32  to close the anvil  306  and clamp the target tissue in position for cutting and stapling. In that instance, the first drive system  30  has been fully actuated. After the target tissue has been clamped in the end effector  300 , it may be desirable to prevent the inadvertent detachment of the shaft assembly  200  from the housing  12 . One form of the latch system  710  is configured to prevent such inadvertent detachment. 
     As can be most particularly seen in  FIG. 7 , the lock yoke  712  includes at least one and preferably two lock hooks  718  that are adapted to contact corresponding lock lug portions  256  that are formed on the closure shuttle  250 . Referring to  FIGS. 13-15 , when the closure shuttle  250  is in an unactuated position (i.e., the first drive system  30  is unactuated and the anvil  306  is open), the lock yoke  712  may be pivoted in a distal direction to unlock the interchangeable shaft assembly  200  from the housing  12 . When in that position, the lock hooks  718  do not contact the lock lug portions  256  on the closure shuttle  250 . However, when the closure shuttle  250  is moved to an actuated position (i.e., the first drive system  30  is actuated and the anvil  306  is in the closed position), the lock yoke  712  is prevented from being pivoted to an unlocked position. See  FIGS. 16-18 . Stated another way, if the clinician were to attempt to pivot the lock yoke  712  to an unlocked position or, for example, the lock yoke  712  was in advertently bumped or contacted in a manner that might otherwise cause it to pivot distally, the lock hooks  718  on the lock yoke  712  will contact the lock lugs  256  on the closure shuttle  250  and prevent movement of the lock yoke  712  to an unlocked position. 
     Attachment of the interchangeable shaft assembly  200  to the handle assembly  14  will now be described with reference to  FIG. 3 . To commence the coupling process, the clinician may position the chassis  240  of the interchangeable shaft assembly  200  above or adjacent to the distal attachment flange  700  of the frame  20  such that the tapered attachment portions  244  formed on the chassis  240  are aligned with the dovetail slots  702  in the frame  20 . The clinician may then move the shaft assembly  200  along an installation axis IA that is perpendicular to the shaft axis SA-SA to seat the attachment portions  244  in “operable engagement” with the corresponding dovetail receiving slots  702 . In doing so, the shaft attachment lug  226  on the intermediate firing shaft  222  will also be seated in the cradle  126  in the longitudinally movable drive member  120  and the portions of pin  37  on the second closure link  38  will be seated in the corresponding hooks  252  in the closure yoke  250 . As used herein, the term “operable engagement” in the context of two components means that the two components are sufficiently engaged with each other so that upon application of an actuation motion thereto, the components may carry out their intended action, function and/or procedure. 
     As discussed above, at least five systems of the interchangeable shaft assembly  200  can be operably coupled with at least five corresponding systems of the handle assembly  14 . A first system can comprise a frame system which couples and/or aligns the frame or spine of the shaft assembly  200  with the frame  20  of the handle assembly  14 . Another system can comprise a closure drive system  30  which can operably connect the closure trigger  32  of the handle assembly  14  and the closure tube  260  and the anvil  306  of the shaft assembly  200 . As outlined above, the closure tube attachment yoke  250  of the shaft assembly  200  can be engaged with the pin  37  on the second closure link  38 . Another system can comprise the firing drive system  80  which can operably connect the firing trigger  130  of the handle assembly  14  with the intermediate firing shaft  222  of the shaft assembly  200 . 
     As outlined above, the shaft attachment lug  226  can be operably connected with the cradle  126  of the longitudinal drive member  120 . Another system can comprise an electrical system which can signal to a controller in the handle assembly  14 , such as microcontroller, for example, that a shaft assembly, such as shaft assembly  200 , for example, has been operably engaged with the handle assembly  14  and/or, two, conduct power and/or communication signals between the shaft assembly  200  and the handle assembly  14 . For instance, the shaft assembly  200  can include an electrical connector  1410  that is operably mounted to the shaft circuit board  610 . The electrical connector  1410  is configured for mating engagement with a corresponding electrical connector  1400  on the handle control board  100 . Further details regaining the circuitry and control systems may be found in U.S. patent application Ser. No. 13/803,086, the entire disclosure of which was previously incorporated by reference herein. The fifth system may consist of the latching system for releasably locking the shaft assembly  200  to the handle assembly  14 . 
     Referring again to  FIGS. 2 and 3 , the handle assembly  14  can include an electrical connector  1400  comprising a plurality of electrical contacts. Turning now to  FIG. 19 , the electrical connector  1400  can comprise a first contact  1401   a , a second contact  1401   b , a third contact  1401   c , a fourth contact  1401   d , a fifth contact  1401   e , and a sixth contact  1401   f , for example. While the illustrated example utilizes six contacts, other examples are envisioned which may utilize more than six contacts or less than six contacts. 
     As illustrated in  FIG. 19 , the first contact  1401   a  can be in electrical communication with a transistor  1408 , contacts  1401   b - 1401   e  can be in electrical communication with a microcontroller  1500 , and the sixth contact  1401   f  can be in electrical communication with a ground. In certain circumstances, one or more of the electrical contacts  1401   b - 1401   e  may be in electrical communication with one or more output channels of the microcontroller  1500  and can be energized, or have a voltage potential applied thereto, when the handle  1042  is in a powered state. In some circumstances, one or more of the electrical contacts  1401   b - 1401   e  may be in electrical communication with one or more input channels of the microcontroller  1500  and, when the handle assembly  14  is in a powered state, the microcontroller  1500  can be configured to detect when a voltage potential is applied to such electrical contacts. When a shaft assembly, such as shaft assembly  200 , for example, is assembled to the handle assembly  14 , the electrical contacts  1401   a - 1401   f  may not communicate with each other. When a shaft assembly is not assembled to the handle assembly  14 , however, the electrical contacts  1401   a - 1401   f  of the electrical connector  1400  may be exposed and, in some circumstances, one or more of the contacts  1401   a - 1401   f  may be accidentally placed in electrical communication with each other. Such circumstances can arise when one or more of the contacts  1401   a - 1401   f  come into contact with an electrically conductive material, for example. When this occurs, the microcontroller  1500  can receive an erroneous input and/or the shaft assembly  200  can receive an erroneous output, for example. To address this issue, in various circumstances, the handle assembly  14  may be unpowered when a shaft assembly, such as shaft assembly  200 , for example, is not attached to the handle assembly  14 . 
     In other circumstances, the handle  1042  can be powered when a shaft assembly, such as shaft assembly  200 , for example, is not attached thereto. In such circumstances, the microcontroller  1500  can be configured to ignore inputs, or voltage potentials, applied to the contacts in electrical communication with the microcontroller  1500 , i.e., contacts  1401   b - 1401   e , for example, until a shaft assembly is attached to the handle assembly  14 . Even though the microcontroller  1500  may be supplied with power to operate other functionalities of the handle assembly  14  in such circumstances, the handle assembly  14  may be in a powered-down state. In a way, the electrical connector  1400  may be in a powered-down state as voltage potentials applied to the electrical contacts  1401   b - 1401   e  may not affect the operation of the handle assembly  14 . The reader will appreciate that, even though contacts  1401   b - 1401   e  may be in a powered-down state, the electrical contacts  1401   a  and  1401   f , which are not in electrical communication with the microcontroller  1500 , may or may not be in a powered-down state. For instance, sixth contact  1401   f  may remain in electrical communication with a ground regardless of whether the handle assembly  14  is in a powered-up or a powered-down state. 
     Furthermore, the transistor  1408 , and/or any other suitable arrangement of transistors, such as transistor  1410 , for example, and/or switches may be configured to control the supply of power from a power source  1404 , such as a battery  90  within the handle assembly  14 , for example, to the first electrical contact  1401   a  regardless of whether the handle assembly  14  is in a powered-up or a powered-down state. In various circumstances, the shaft assembly  200 , for example, can be configured to change the state of the transistor  1408  when the shaft assembly  200  is engaged with the handle assembly  14 . In certain circumstances, further to the below, a magnetic field sensor  1402  can be configured to switch the state of transistor  1410  which, as a result, can switch the state of transistor  1408  and ultimately supply power from power source  1404  to first contact  1401   a . In this way, both the power circuits and the signal circuits to the connector  1400  can be powered down when a shaft assembly is not installed to the handle assembly  14  and powered up when a shaft assembly is installed to the handle assembly  14 . 
     In various circumstances, referring again to  FIG. 19 , the handle assembly  14  can include the magnetic field sensor  1402 , for example, which can be configured to detect a detectable element, such as a magnetic element  1407  ( FIG. 3 ), for example, on a shaft assembly, such as shaft assembly  200 , for example, when the shaft assembly is coupled to the handle assembly  14 . The magnetic field sensor  1402  can be powered by a power source  1406 , such as a battery, for example, which can, in effect, amplify the detection signal of the magnetic field sensor  1402  and communicate with an input channel of the microcontroller  1500  via the circuit illustrated in  FIG. 19 . Once the microcontroller  1500  has a received an input indicating that a shaft assembly has been at least partially coupled to the handle assembly  14 , and that, as a result, the electrical contacts  1401   a - 1401   f  are no longer exposed, the microcontroller  1500  can enter into its normal, or powered-up, operating state. In such an operating state, the microcontroller  1500  will evaluate the signals transmitted to one or more of the contacts  1401   b - 1401   e  from the shaft assembly and/or transmit signals to the shaft assembly through one or more of the contacts  1401   b - 1401   e  in normal use thereof. In various circumstances, the shaft assembly  200  may have to be fully seated before the magnetic field sensor  1402  can detect the magnetic element  1407 . While a magnetic field sensor  1402  can be utilized to detect the presence of the shaft assembly  200 , any suitable system of sensors and/or switches can be utilized to detect whether a shaft assembly has been assembled to the handle assembly  14 , for example. In this way, further to the above, both the power circuits and the signal circuits to the connector  1400  can be powered down when a shaft assembly is not installed to the handle assembly  14  and powered up when a shaft assembly is installed to the handle assembly  14 . 
     In various examples, as may be used throughout the present disclosure, any suitable magnetic field sensor may be employed to detect whether a shaft assembly has been assembled to the handle assembly  14 , for example. For example, the technologies used for magnetic field sensing include Hall effect sensor, search coil, fluxgate, optically pumped, nuclear precession, SQUID, Hall-effect, anisotropic magnetoresistance, giant magnetoresistance, magnetic tunnel junctions, giant magnetoimpedance, magnetostrictive/piezoelectric composites, magnetodiode, magnetotransistor, fiber optic, magnetooptic, and microelectromechanical systems-based magnetic sensors, among others. 
     Referring to  FIG. 19 , the microcontroller  1500  may generally comprise a microprocessor (“processor”) and one or more memory units operationally coupled to the processor. By executing instruction code stored in the memory, the processor may control various components of the surgical instrument, such as the motor, various drive systems, and/or a user display, for example. The microcontroller  1500  may be implemented using integrated and/or discrete hardware elements, software elements, and/or a combination of both. Examples of integrated hardware elements may include processors, microprocessors, microcontrollers, integrated circuits, application specific integrated circuits (ASIC), programmable logic devices (PLD), digital signal processors (DSP), field programmable gate arrays (FPGA), logic gates, registers, semiconductor devices, chips, microchips, chip sets, microcontrollers, system-on-chip (SoC), and/or system-in-package (SIP). Examples of discrete hardware elements may include circuits and/or circuit elements such as logic gates, field effect transistors, bipolar transistors, resistors, capacitors, inductors, and/or relays. In certain instances, the microcontroller  1500  may include a hybrid circuit comprising discrete and integrated circuit elements or components on one or more substrates, for example. 
     Referring to  FIG. 19 , the microcontroller  1500  may be an LM 4F230H5QR, available from Texas Instruments, for example. In certain instances, the Texas Instruments LM4F230H5QR is an ARM Cortex-M4F Processor Core comprising on-chip memory of 256 KB single-cycle flash memory, or other non-volatile memory, up to 40 MHz, a prefetch buffer to improve performance above 40 MHz, a 32 KB single-cycle serial random access memory (SRAM), internal read-only memory (ROM) loaded with StellarisWare® software, 2 KB electrically erasable programmable read-only memory (EEPROM), one or more pulse width modulation (PWM) modules, one or more quadrature encoder inputs (QEI) analog, one or more 12-bit Analog-to-Digital Converters (ADC) with  12  analog input channels, among other features that are readily available. Other microcontrollers may be readily substituted for use with the present disclosure. Accordingly, the present disclosure should not be limited in this context. 
     As discussed above, the handle assembly  14  and/or the shaft assembly  200  can include systems and configurations configured to prevent, or at least reduce the possibility of, the contacts of the handle electrical connector  1400  and/or the contacts of the shaft electrical connector  1410  from becoming shorted out when the shaft assembly  200  is not assembled, or completely assembled, to the handle assembly  14 . Referring to  FIG. 3 , the handle electrical connector  1400  can be at least partially recessed within a cavity  1409  defined in the handle frame  20 . The six contacts  1401   a - 1401   f  of the electrical connector  1400  can be completely recessed within the cavity  1409 . Such arrangements can reduce the possibility of an object accidentally contacting one or more of the contacts  1401   a - 1401   f . Similarly, the shaft electrical connector  1410  can be positioned within a recess defined in the shaft chassis  240  which can reduce the possibility of an object accidentally contacting one or more of the contacts  1411   a - 1411   f  of the shaft electrical connector  1410 . With regard to the particular example depicted in  FIG. 3 , the shaft contacts  1411   a - 1411   f  can comprise male contacts. In at least one example, each shaft contact  1411   a - 1411   f  can comprise a flexible projection extending therefrom which can be configured to engage a corresponding handle contact  1401   a - 1401   f , for example. The handle contacts  1401   a - 1401   f  can comprise female contacts. In at least one example, each handle contact  1401   a - 1401   f  can comprise a flat surface, for example, against which the male shaft contacts  1401   a - 1401   f  can wipe, or slide, against and maintain an electrically conductive interface therebetween. In various instances, the direction in which the shaft assembly  200  is assembled to the handle assembly  14  can be parallel to, or at least substantially parallel to, the handle contacts  1401   a - 1401   f  such that the shaft contacts  1411   a - 1411   f  slide against the handle contacts  1401   a - 1401   f  when the shaft assembly  200  is assembled to the handle assembly  14 . In various alternative examples, the handle contacts  1401   a - 1401   f  can comprise male contacts and the shaft contacts  1411   a - 1411   f  can comprise female contacts. In certain alternative examples, the handle contacts  1401   a - 1401   f  and the shaft contacts  1411   a - 1411   f  can comprise any suitable arrangement of contacts. 
     In various instances, the handle assembly  14  can comprise a connector guard configured to at least partially cover the handle electrical connector  1400  and/or a connector guard configured to at least partially cover the shaft electrical connector  1410 . A connector guard can prevent, or at least reduce the possibility of, an object accidentally touching the contacts of an electrical connector when the shaft assembly is not assembled to, or only partially assembled to, the handle. A connector guard can be movable. For instance, the connector guard can be moved between a guarded position in which it at least partially guards a connector and an unguarded position in which it does not guard, or at least guards less of, the connector. In at least one example, a connector guard can be displaced as the shaft assembly is being assembled to the handle. For instance, if the handle comprises a handle connector guard, the shaft assembly can contact and displace the handle connector guard as the shaft assembly is being assembled to the handle. Similarly, if the shaft assembly comprises a shaft connector guard, the handle can contact and displace the shaft connector guard as the shaft assembly is being assembled to the handle. In various instances, a connector guard can comprise a door, for example. In at least one instance, the door can comprise a beveled surface which, when contacted by the handle or shaft, can facilitate the displacement of the door in a certain direction. In various instances, the connector guard can be translated and/or rotated, for example. In certain instances, a connector guard can comprise at least one film which covers the contacts of an electrical connector. When the shaft assembly is assembled to the handle, the film can become ruptured. In at least one instance, the male contacts of a connector can penetrate the film before engaging the corresponding contacts positioned underneath the film. 
     As described above, the surgical instrument can include a system which can selectively power-up, or activate, the contacts of an electrical connector, such as the electrical connector  1400 , for example. In various instances, the contacts can be transitioned between an unactivated condition and an activated condition. In certain instances, the contacts can be transitioned between a monitored condition, a deactivated condition, and an activated condition. For instance, the microcontroller  1500 , for example, can monitor the contacts  1401   a - 1401   f  when a shaft assembly has not been assembled to the handle assembly  14  to determine whether one or more of the contacts  1401   a - 1401   f  may have been shorted. The microcontroller  1500  can be configured to apply a low voltage potential to each of the contacts  1401   a - 1401   f  and assess whether only a minimal resistance is present at each of the contacts. Such an operating state can comprise the monitored condition. In the event that the resistance detected at a contact is high, or above a threshold resistance, the microcontroller  1500  can deactivate that contact, more than one contact, or, alternatively, all of the contacts. Such an operating state can comprise the deactivated condition. If a shaft assembly is assembled to the handle assembly  14  and it is detected by the microcontroller  1500 , as discussed above, the microcontroller  1500  can increase the voltage potential to the contacts  1401   a - 1401   f . Such an operating state can comprise the activated condition. 
     The various shaft assemblies disclosed herein may employ sensors and various other components that require electrical communication with the controller in the housing. These shaft assemblies generally are configured to be able to rotate relative to the housing necessitating a connection that facilitates such electrical communication between two or more components that may rotate relative to each other. When employing end effectors of the types disclosed herein, the connector arrangements must be relatively robust in nature while also being somewhat compact to fit into the shaft assembly connector portion. 
     Referring to  FIG. 20 , a non-limiting form of the end effector  300  is illustrated. As described above, the end effector  300  may include the anvil  306  and the staple cartridge  304 . In this non-limiting example, the anvil  306  is coupled to an elongate channel  198 . For example, apertures  199  can be defined in the elongate channel  198  which can receive pins  152  extending from the anvil  306  and allow the anvil  306  to pivot from an open position to a closed position relative to the elongate channel  198  and staple cartridge  304 . In addition,  FIG. 20  shows a firing bar  172 , configured to longitudinally translate into the end effector  300 . The firing bar  172  may be constructed from one solid section, or in various examples, may include a laminate material comprising, for example, a stack of steel plates. A distally projecting end of the firing bar  172  can be attached to an E-beam  178  that can, among other things, assist in spacing the anvil  306  from a staple cartridge  304  positioned in the elongate channel  198  when the anvil  306  is in a closed position. The E-beam  178  can also include a sharpened cutting edge  182  which can be used to sever tissue as the E-beam  178  is advanced distally by the firing bar  172 . In operation, the E-beam  178  can also actuate, or fire, the staple cartridge  304 . The staple cartridge  304  can include a molded cartridge body  194  that holds a plurality of staples  191  resting upon staple drivers  192  within respective upwardly open staple cavities  195 . A wedge sled  190  is driven distally by the E-beam  178 , sliding upon a cartridge tray  196  that holds together the various components of the replaceable staple cartridge  304 . The wedge sled  190  upwardly cams the staple drivers  192  to force out the staples  191  into deforming contact with the anvil  306  while a cutting surface  182  of the E-beam  178  severs clamped tissue. 
     Further to the above, the E-beam  178  can include upper pins  180  which engage the anvil  306  during firing. The E-beam  178  can further include middle pins  184  and a bottom foot  186  which can engage various portions of the cartridge body  194 , cartridge tray  196  and elongate channel  198 . When a staple cartridge  304  is positioned within the elongate channel  198 , a slot  193  defined in the cartridge body  194  can be aligned with a slot  197  defined in the cartridge tray  196  and a slot  189  defined in the elongate channel  198 . In use, the E-beam  178  can slide through the aligned slots  193 ,  197 , and  189  wherein, as indicated in  FIG. 20 , the bottom foot  186  of the E-beam  178  can engage a groove running along the bottom surface of channel  198  along the length of slot  189 , the middle pins  184  can engage the top surfaces of cartridge tray  196  along the length of longitudinal slot  197 , and the upper pins  180  can engage the anvil  306 . In such circumstances, the E-beam  178  can space, or limit the relative movement between, the anvil  306  and the staple cartridge  304  as the firing bar  172  is moved distally to fire the staples from the staple cartridge  304  and/or incise the tissue captured between the anvil  306  and the staple cartridge  304 . Thereafter, the firing bar  172  and the E-beam  178  can be retracted proximally allowing the anvil  306  to be opened to release the two stapled and severed tissue portions (not shown). 
     Having described a surgical instrument  10  ( FIGS. 1-4 ) in general terms, the description now turns to a detailed description of various electrical/electronic components of the surgical instrument  10 . Turning now to  FIGS. 21A-21B , where one example of a segmented circuit  2000  comprising a plurality of circuit segments  2002   a - 2002   g  is illustrated. The segmented circuit  2000  comprising the plurality of circuit segments  2002   a - 2002   g  is configured to control a powered surgical instrument, such as, for example, the surgical instrument  10  illustrated in  FIGS. 1-18A , without limitation. The plurality of circuit segments  2002   a - 2002   g  is configured to control one or more operations of the powered surgical instrument  10 . A safety processor segment  2002   a  (Segment 1) comprises a safety processor  2004 . A primary processor segment  2002   b  (Segment 2) comprises a primary processor  2006 . The safety processor  2004  and/or the primary processor  2006  are configured to interact with one or more additional circuit segments  2002   c - 2002   g  to control operation of the powered surgical instrument  10 . The primary processor  2006  comprises a plurality of inputs coupled to, for example, one or more circuit segments  2002   c - 2002   g , a battery  2008 , and/or a plurality of switches  2058   a - 2070 . The segmented circuit  2000  may be implemented by any suitable circuit, such as, for example, a printed circuit board assembly (PCBA) within the powered surgical instrument  10 . It should be understood that the term processor as used herein includes any microprocessor, microcontroller, or other basic computing device that incorporates the functions of a computer&#39;s central processing unit (CPU) on an integrated circuit or at most a few integrated circuits. The processor is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and provides results as output. It is an example of sequential digital logic, as it has internal memory. Processors operate on numbers and symbols represented in the binary numeral system. 
     In one aspect, the main processor  2006  may be any single core or multicore processor such as those known under the trade name ARM Cortex by Texas Instruments. In one example, the safety processor  2004  may be a safety microcontroller platform comprising two microcontroller-based families such as TMS570 and RM4x known under the trade name Hercules ARM Cortex R4, also by Texas Instruments. Nevertheless, other suitable substitutes for microcontrollers and safety processor may be employed, without limitation. In one example, the safety processor  2004  may be configured specifically for IEC 61508 and ISO 26262 safety critical applications, among others, to provide advanced integrated safety features while delivering scalable performance, connectivity, and memory options. 
     In certain instances, the main processor  2006  may be an LM 4F230H5QR, available from Texas Instruments, for example. In at least one example, the Texas Instruments LM4F230H5QR is an ARM Cortex-M4F Processor Core comprising on-chip memory of 256 KB single-cycle flash memory, or other non-volatile memory, up to 40 MHz, a prefetch buffer to improve performance above 40 MHz, a 32 KB single-cycle SRAM, internal ROM loaded with StellarisWare® software, 2 KB EEPROM, one or more PWM modules, one or more QEI analog, one or more 12-bit ADC with  12  analog input channels, among other features that are readily available for the product datasheet. Other processors may be readily substituted and, accordingly, the present disclosure should not be limited in this context. 
     In one aspect, the segmented circuit  2000  comprises an acceleration segment  2002   c  (Segment 3). The acceleration segment  2002   c  comprises an acceleration sensor  2022 . The acceleration sensor  2022  may comprise, for example, an accelerometer. The acceleration sensor  2022  is configured to detect movement or acceleration of the powered surgical instrument  10 . In some examples, input from the acceleration sensor  2022  is used, for example, to transition to and from a sleep mode, identify an orientation of the powered surgical instrument, and/or identify when the surgical instrument has been dropped. In some examples, the acceleration segment  2002   c  is coupled to the safety processor  2004  and/or the primary processor  2006 . 
     In one aspect, the segmented circuit  2000  comprises a display segment  2002   d  (Segment 4). The display segment  2002   d  comprises a display connector  2024  coupled to the primary processor  2006 . The display connector  2024  couples the primary processor  2006  to a display  2028  through one or more display driver integrated circuits  2026 . The display driver integrated circuits  2026  may be integrated with the display  2028  and/or may be located separately from the display  2028 . The display  2028  may comprise any suitable display, such as, for example, an organic light-emitting diode (OLED) display, a liquid-crystal display (LCD), and/or any other suitable display. In some examples, the display segment  2002   d  is coupled to the safety processor  2004 . 
     In some aspects, the segmented circuit  2000  comprises a shaft segment  2002   e  (Segment 5). The shaft segment  2002   e  comprises one or more controls for a shaft  2004  coupled to the surgical instrument  10  and/or one or more controls for an end effector  2006  coupled to the shaft  2004 . The shaft segment  2002   e  comprises a shaft connector  2030  configured to couple the primary processor  2006  to a shaft PCBA  2031 . The shaft PCBA  2031  comprises a first articulation switch  2036 , a second articulation switch  2032 , and a shaft PCBA EEPROM  2034 . In some examples, the shaft PCBA EEPROM  2034  comprises one or more parameters, routines, and/or programs specific to the shaft  2004  and/or the shaft PCBA  2031 . The shaft PCBA  2031  may be coupled to the shaft  2004  and/or integral with the surgical instrument  10 . In some examples, the shaft segment  2002   e  comprises a second shaft EEPROM  2038 . The second shaft EEPROM  2038  comprises a plurality of algorithms, routines, parameters, and/or other data corresponding to one or more shafts  2004  and/or end effectors  2006  which may be interfaced with the powered surgical instrument  10 . 
     In some aspects, the segmented circuit  2000  comprises a position encoder segment  2002   f  (Segment 6). The position encoder segment  2002   f  comprises one or more magnetic rotary position encoders  2040   a - 2040   b . The one or more magnetic rotary position encoders  2040   a - 2040   b  are configured to identify the rotational position of a motor  2048 , a shaft  2004 , and/or an end effector  2006  of the surgical instrument  10 . In some examples, the magnetic rotary position encoders  2040   a - 2040   b  may be coupled to the safety processor  2004  and/or the primary processor  2006 . 
     In some aspects, the segmented circuit  2000  comprises a motor segment  2002   g  (Segment 7). The motor segment  2002   g  comprises a motor  2048  configured to control one or more movements of the powered surgical instrument  10 . The motor  2048  is coupled to the primary processor  2006  by an H-Bridge driver  2042  and one or more H-bridge field-effect transistors (FETs)  2044 . The H-bridge FETs  2044  are coupled to the safety processor  2004 . A motor current sensor  2046  is coupled in series with the motor  2048  to measure the current draw of the motor  2048 . The motor current sensor  2046  is in signal communication with the primary processor  2006  and/or the safety processor  2004 . In some examples, the motor  2048  is coupled to a motor electromagnetic interference (EMI) filter  2050 . 
     In some aspects, the segmented circuit  2000  comprises a power segment  2002   h  (Segment 8). A battery  2008  is coupled to the safety processor  2004 , the primary processor  2006 , and one or more of the additional circuit segments  2002   c - 2002   g . The battery  2008  is coupled to the segmented circuit  2000  by a battery connector  2010  and a current sensor  2012 . The current sensor  2012  is configured to measure the total current draw of the segmented circuit  2000 . In some examples, one or more voltage converters  2014   a ,  2014   b ,  2016  are configured to provide predetermined voltage values to one or more circuit segments  2002   a - 2002   g . For example, in some examples, the segmented circuit  2000  may comprise 3.3V voltage converters  2014   a - 2014   b  and/or 5V voltage converters  2016 . A boost converter  2018  is configured to provide a boost voltage up to a predetermined amount, such as, for example, up to 13V. The boost converter  2018  is configured to provide additional voltage and/or current during power intensive operations and prevent brownout or low-power conditions. 
     In some aspects, the safety segment  2002   a  comprises a motor power interrupt  2020 . The motor power interrupt  2020  is coupled between the power segment  2002   h  and the motor segment  2002   g . The safety segment  2002   a  is configured to interrupt power to the motor segment  2002   g  when an error or fault condition is detected by the safety processor  2004  and/or the primary processor  2006  as discussed in more detail herein. Although the circuit segments  2002   a - 2002   g  are illustrated with all components of the circuit segments  2002   a - 2002   h  located in physical proximity, one skilled in the art will recognize that a circuit segment  2002   a - 2002   h  may comprise components physically and/or electrically separate from other components of the same circuit segment  2002   a - 2002   g . In some examples, one or more components may be shared between two or more circuit segments  2002   a - 2002   g.    
     In some aspects, a plurality of switches  2056 - 2070  are coupled to the safety processor  2004  and/or the primary processor  2006 . The plurality of switches  2056 - 2070  may be configured to control one or more operations of the surgical instrument  10 , control one or more operations of the segmented circuit  2000 , and/or indicate a status of the surgical instrument  10 . For example, a bail-out door switch  2056  is configured to indicate the status of a bail-out door. A plurality of articulation switches, such as, for example, a left side articulation left switch  2058   a , a left side articulation right switch  2060   a , a left side articulation center switch  2062   a , a right side articulation left switch  2058   b , a right side articulation right switch  2060   b , and a right side articulation center switch  2062   b  are configured to control articulation of a shaft  2004  and/or an end effector  2006 . A left side reverse switch  2064   a  and a right side reverse switch  2064   b  are coupled to the primary processor  2006 . In some examples, the left side switches comprising the left side articulation left switch  2058   a , the left side articulation right switch  2060   a , the left side articulation center switch  2062   a , and the left side reverse switch  2064   a  are coupled to the primary processor  2006  by a left flex connector  2072   a . The right side switches comprising the right side articulation left switch  2058   b , the right side articulation right switch  2060   b , the right side articulation center switch  2062   b , and the right side reverse switch  2064   b  are coupled to the primary processor  2006  by a right flex connector  2072   b . In some examples, a firing switch  2066 , a clamp release switch  2068 , and a shaft engaged switch  2070  are coupled to the primary processor  2006 . 
     In some aspects, the plurality of switches  2056 - 2070  may comprise, for example, a plurality of handle controls mounted to a handle of the surgical instrument  10 , a plurality of indicator switches, and/or any combination thereof. In various examples, the plurality of switches  2056 - 2070  allow a surgeon to manipulate the surgical instrument, provide feedback to the segmented circuit  2000  regarding the position and/or operation of the surgical instrument, and/or indicate unsafe operation of the surgical instrument  10 . In some examples, additional or fewer switches may be coupled to the segmented circuit  2000 , one or more of the switches  2056 - 2070  may be combined into a single switch, and/or expanded to multiple switches. For example, in one example, one or more of the left side and/or right side articulation switches  2058   a - 2064   b  may be combined into a single multi-position switch. 
     In one aspect, the safety processor  2004  is configured to implement a watchdog function, among other safety operations. The safety processor  2004  and the primary processor  2006  of the segmented circuit  2000  are in signal communication. A microprocessor alive heartbeat signal is provided at output  2096 . The acceleration segment  2002   c  comprises an accelerometer  2022  configured to monitor movement of the surgical instrument  10 . In various examples, the accelerometer  2022  may be a single, double, or triple axis accelerometer. The accelerometer  2022  may be employed to measures proper acceleration that is not necessarily the coordinate acceleration (rate of change of velocity). Instead, the accelerometer sees the acceleration associated with the phenomenon of weight experienced by a test mass at rest in the frame of reference of the accelerometer  2022 . For example, the accelerometer  2022  at rest on the surface of the earth will measure an acceleration g=9.8 m/s 2  (gravity) straight upwards, due to its weight. Another type of acceleration that accelerometer  2022  can measure is g-force acceleration. In various other examples, the accelerometer  2022  may comprise a single, double, or triple axis accelerometer. Further, the acceleration segment  2002   c  may comprise one or more inertial sensors to detect and measure acceleration, tilt, shock, vibration, rotation, and multiple degrees-of-freedom (DoF). A suitable inertial sensor may comprise an accelerometer (single, double, or triple axis), a magnetometer to measure a magnetic field in space such as the earth&#39;s magnetic field, and/or a gyroscope to measure angular velocity. 
     In one aspect, the safety processor  2004  is configured to implement a watchdog function with respect to one or more circuit segments  2002   c - 2002   h , such as, for example, the motor segment  2002   g . In this regards, the safety processor  2004  employs the watchdog function to detect and recover from malfunctions of the primary processor  2006 . During normal operation, the safety processor  2004  monitors for hardware faults or program errors of the primary processor  2004  and to initiate corrective action or actions. The corrective actions may include placing the primary processor  2006  in a safe state and restoring normal system operation. In one example, the safety processor  2004  is coupled to at least a first sensor. The first sensor measures a first property of the surgical instrument  10  ( FIGS. 1-4 ). In some examples, the safety processor  2004  is configured to compare the measured property of the surgical instrument  10  to a predetermined value. For example, in one example, a motor sensor  2040   a  is coupled to the safety processor  2004 . The motor sensor  2040   a  provides motor speed and position information to the safety processor  2004 . The safety processor  2004  monitors the motor sensor  2040   a  and compares the value to a maximum speed and/or position value and prevents operation of the motor  2048  above the predetermined values. In some examples, the predetermined values are calculated based on real-time speed and/or position of the motor  2048 , calculated from values supplied by a second motor sensor  2040   b  in communication with the primary processor  2006 , and/or provided to the safety processor  2004  from, for example, a memory module coupled to the safety processor  2004 . 
     In some aspects, a second sensor is coupled to the primary processor  2006 . The second sensor is configured to measure the first physical property. The safety processor  2004  and the primary processor  2006  are configured to provide a signal indicative of the value of the first sensor and the second sensor respectively. When either the safety processor  2004  or the primary processor  2006  indicates a value outside of an acceptable range, the segmented circuit  2000  prevents operation of at least one of the circuit segments  2002   c - 2002   h , such as, for example, the motor segment  2002   g . For example, in the example illustrated in  FIGS. 21A-21B , the safety processor  2004  is coupled to a first motor position sensor  2040   a  and the primary processor  2006  is coupled to a second motor position sensor  2040   b . The motor position sensors  2040   a ,  2040   b  may comprise any suitable motor position sensor, such as, for example, a magnetic angle rotary input comprising a sine and cosine output. The motor position sensors  2040   a ,  2040   b  provide respective signals to the safety processor  2004  and the primary processor  2006  indicative of the position of the motor  2048 . 
     The safety processor  2004  and the primary processor  2006  generate an activation signal when the values of the first motor sensor  2040   a  and the second motor sensor  2040   b  are within a predetermined range. When either the primary processor  2006  or the safety processor  2004  to detect a value outside of the predetermined range, the activation signal is terminated and operation of at least one circuit segment  2002   c - 2002   h , such as, for example, the motor segment  2002   g , is interrupted and/or prevented. For example, in some examples, the activation signal from the primary processor  2006  and the activation signal from the safety processor  2004  are coupled to an AND gate. The AND gate is coupled to a motor power switch  2020 . The AND gate maintains the motor power switch  2020  in a closed, or on, position when the activation signal from both the safety processor  2004  and the primary processor  2006  are high, indicating a value of the motor sensors  2040   a ,  2040   b  within the predetermined range. When either of the motor sensors  2040   a ,  2040   b  detect a value outside of the predetermined range, the activation signal from that motor sensor  2040   a ,  2040   b  is set low, and the output of the AND gate is set low, opening the motor power switch  2020 . In some examples, the value of the first sensor  2040   a  and the second sensor  2040   b  is compared, for example, by the safety processor  2004  and/or the primary processor  2006 . When the values of the first sensor and the second sensor are different, the safety processor  2004  and/or the primary processor  2006  may prevent operation of the motor segment  2002   g.    
     In some aspects, the safety processor  2004  receives a signal indicative of the value of the second sensor  2040   b  and compares the second sensor value to the first sensor value. For example, in one aspect, the safety processor  2004  is coupled directly to a first motor sensor  2040   a . A second motor sensor  2040   b  is coupled to a primary processor  2006 , which provides the second motor sensor  2040   b  value to the safety processor  2004 , and/or coupled directly to the safety processor  2004 . The safety processor  2004  compares the value of the first motor sensor  2040  to the value of the second motor sensor  2040   b . When the safety processor  2004  detects a mismatch between the first motor sensor  2040   a  and the second motor sensor  2040   b , the safety processor  2004  may interrupt operation of the motor segment  2002   g , for example, by cutting power to the motor segment  2002   g.    
     In some aspects, the safety processor  2004  and/or the primary processor  2006  is coupled to a first sensor  2040   a  configured to measure a first property of a surgical instrument and a second sensor  2040   b  configured to measure a second property of the surgical instrument. The first property and the second property comprise a predetermined relationship when the surgical instrument is operating normally. The safety processor  2004  monitors the first property and the second property. When a value of the first property and/or the second property inconsistent with the predetermined relationship is detected, a fault occurs. When a fault occurs, the safety processor  2004  takes at least one action, such as, for example, preventing operation of at least one of the circuit segments, executing a predetermined operation, and/or resetting the primary processor  2006 . For example, the safety processor  2004  may open the motor power switch  2020  to cut power to the motor circuit segment  2002   g  when a fault is detected. 
     In one aspect, the safety processor  2004  is configured to execute an independent control algorithm. In operation, the safety processor  2004  monitors the segmented circuit  2000  and is configured to control and/or override signals from other circuit components, such as, for example, the primary processor  2006 , independently. The safety processor  2004  may execute a preprogrammed algorithm and/or may be updated or programmed on the fly during operation based on one or more actions and/or positions of the surgical instrument  10 . For example, in one example, the safety processor  2004  is reprogrammed with new parameters and/or safety algorithms each time a new shaft and/or end effector is coupled to the surgical instrument  10 . In some examples, one or more safety values stored by the safety processor  2004  are duplicated by the primary processor  2006 . Two-way error detection is performed to ensure values and/or parameters stored by either of the processors  2004 ,  2006  are correct. 
     In some aspects, the safety processor  2004  and the primary processor  2006  implement a redundant safety check. The safety processor  2004  and the primary processor  2006  provide periodic signals indicating normal operation. For example, during operation, the safety processor  2004  may indicate to the primary processor  2006  that the safety processor  2004  is executing code and operating normally. The primary processor  2006  may, likewise, indicate to the safety processor  2004  that the primary processor  2006  is executing code and operating normally. In some examples, communication between the safety processor  2004  and the primary processor  2006  occurs at a predetermined interval. The predetermined interval may be constant or may be variable based on the circuit state and/or operation of the surgical instrument  10 . 
       FIG. 22  illustrates one example of a power assembly  2100  comprising a usage cycle circuit  2102  configured to monitor a usage cycle count of the power assembly  2100 . The power assembly  2100  may be coupled to a surgical instrument  2110 . The usage cycle circuit  2102  comprises a processor  2104  and a use indicator  2106 . The use indicator  2106  is configured to provide a signal to the processor  2104  to indicate a use of the battery back  2100  and/or a surgical instrument  2110  coupled to the power assembly  2100 . A “use” may comprise any suitable action, condition, and/or parameter such as, for example, changing a modular component of a surgical instrument  2110 , deploying or firing a disposable component coupled to the surgical instrument  2110 , delivering electrosurgical energy from the surgical instrument  2110 , reconditioning the surgical instrument  2110  and/or the power assembly  2100 , exchanging the power assembly  2100 , recharging the power assembly  2100 , and/or exceeding a safety limitation of the surgical instrument  2110  and/or the battery back  2100 . 
     In some instances, a usage cycle, or use, is defined by one or more power assembly  2100  parameters. For example, in one instance, a usage cycle comprises using more than 5% of the total energy available from the power assembly  2100  when the power assembly  2100  is at a full charge level. In another instance, a usage cycle comprises a continuous energy drain from the power assembly  2100  exceeding a predetermined time limit. For example, a usage cycle may correspond to five minutes of continuous and/or total energy draw from the power assembly  2100 . In some instances, the power assembly  2100  comprises a usage cycle circuit  2102  having a continuous power draw to maintain one or more components of the usage cycle circuit  2102 , such as, for example, the use indicator  2106  and/or a counter  2108 , in an active state. 
     The processor  2104  maintains a usage cycle count. The usage cycle count indicates the number of uses detected by the use indicator  2106  for the power assembly  2100  and/or the surgical instrument  2110 . The processor  2104  may increment and/or decrement the usage cycle count based on input from the use indicator  2106 . The usage cycle count is used to control one or more operations of the power assembly  2100  and/or the surgical instrument  2110 . For example, in some instances, a power assembly  2100  is disabled when the usage cycle count exceeds a predetermined usage limit. Although the instances discussed herein are discussed with respect to incrementing the usage cycle count above a predetermined usage limit, those skilled in the art will recognize that the usage cycle count may start at a predetermined amount and may be decremented by the processor  2104 . In this instance, the processor  2104  initiates and/or prevents one or more operations of the power assembly  2100  when the usage cycle count falls below a predetermined usage limit. 
     The usage cycle count is maintained by a counter  2108 . The counter  2108  comprises any suitable circuit, such as, for example, a memory module, an analog counter, and/or any circuit configured to maintain a usage cycle count. In some instances, the counter  2108  is formed integrally with the processor  2104 . In other instances, the counter  2108  comprises a separate component, such as, for example, a solid state memory module. In some instances, the usage cycle count is provided to a remote system, such as, for example, a central database. The usage cycle count is transmitted by a communications module  2112  to the remote system. The communications module  2112  is configured to use any suitable communications medium, such as, for example, wired and/or wireless communication. In some instances, the communications module  2112  is configured to receive one or more instructions from the remote system, such as, for example, a control signal when the usage cycle count exceeds the predetermined usage limit. 
     In some instances, the use indicator  2106  is configured to monitor the number of modular components used with a surgical instrument  2110  coupled to the power assembly  2100 . A modular component may comprise, for example, a modular shaft, a modular end effector, and/or any other modular component. In some instances, the use indicator  2106  monitors the use of one or more disposable components, such as, for example, insertion and/or deployment of a staple cartridge within an end effector coupled to the surgical instrument  2110 . The use indicator  2106  comprises one or more sensors for detecting the exchange of one or more modular and/or disposable components of the surgical instrument  2110 . 
     In some instances, the use indicator  2106  is configured to monitor single patient surgical procedures performed while the power assembly  2100  is installed. For example, the use indicator  2106  may be configured to monitor firings of the surgical instrument  2110  while the power assembly  2100  is coupled to the surgical instrument  2110 . A firing may correspond to deployment of a staple cartridge, application of electrosurgical energy, and/or any other suitable surgical event. The use indicator  2106  may comprise one or more circuits for measuring the number of firings while the power assembly  2100  is installed. The use indicator  2106  provides a signal to the processor  2104  when a single patient procedure is performed and the processor  2104  increments the usage cycle count. 
     In some instances, the use indicator  2106  comprises a circuit configured to monitor one or more parameters of the power source  2114 , such as, for example, a current draw from the power source  2114 . The one or more parameters of the power source  2114  correspond to one or more operations performable by the surgical instrument  2110 , such as, for example, a cutting and sealing operation. The use indicator  2106  provides the one or more parameters to the processor  2104 , which increments the usage cycle count when the one or more parameters indicate that a procedure has been performed. 
     In some instances, the use indicator  2106  comprises a timing circuit configured to increment a usage cycle count after a predetermined time period. The predetermined time period corresponds to a single patient procedure time, which is the time required for an operator to perform a procedure, such as, for example, a cutting and sealing procedure. When the power assembly  2100  is coupled to the surgical instrument  2110 , the processor  2104  polls the use indicator  2106  to determine when the single patient procedure time has expired. When the predetermined time period has elapsed, the processor  2104  increments the usage cycle count. After incrementing the usage cycle count, the processor  2104  resets the timing circuit of the use indicator  2106 . 
     In some instances, the use indicator  2106  comprises a time constant that approximates the single patient procedure time. In one example, the usage cycle circuit  2102  comprises a resistor-capacitor (RC) timing circuit  2506 . The RC timing circuit comprises a time constant defined by a resistor-capacitor pair. The time constant is defined by the values of the resistor and the capacitor. In one example, the usage cycle circuit  2552  comprises a rechargeable battery and a clock. When the power assembly  2100  is installed in a surgical instrument, the rechargeable battery is charged by the power source. The rechargeable battery comprises enough power to run the clock for at least the single patient procedure time. The clock may comprise a real time clock, a processor configured to implement a time function, or any other suitable timing circuit. 
     Referring still to  FIG. 22 , in some instances, the use indicator  2106  comprises a sensor configured to monitor one or more environmental conditions experienced by the power assembly  2100 . For example, the use indicator  2106  may comprise an accelerometer. The accelerometer is configured to monitor acceleration of the power assembly  2100 . The power assembly  2100  comprises a maximum acceleration tolerance. Acceleration above a predetermined threshold indicates, for example, that the power assembly  2100  has been dropped. When the use indicator  2106  detects acceleration above the maximum acceleration tolerance, the processor  2104  increments a usage cycle count. In some instances, the use indicator  2106  comprises a moisture sensor. The moisture sensor is configured to indicate when the power assembly  2100  has been exposed to moisture. The moisture sensor may comprise, for example, an immersion sensor configured to indicate when the power assembly  2100  has been fully immersed in a cleaning fluid, a moisture sensor configured to indicate when moisture is in contact with the power assembly  2100  during use, and/or any other suitable moisture sensor. 
     In some instances, the use indicator  2106  comprises a chemical exposure sensor. The chemical exposure sensor is configured to indicate when the power assembly  2100  has come into contact with harmful and/or dangerous chemicals. For example, during a sterilization procedure, an inappropriate chemical may be used that leads to degradation of the power assembly  2100 . The processor  2104  increments the usage cycle count when the use indicator  2106  detects an inappropriate chemical. 
     In some instances, the usage cycle circuit  2102  is configured to monitor the number of reconditioning cycles experienced by the power assembly  2100 . A reconditioning cycle may comprise, for example, a cleaning cycle, a sterilization cycle, a charging cycle, routine and/or preventative maintenance, and/or any other suitable reconditioning cycle. The use indicator  2106  is configured to detect a reconditioning cycle. For example, the use indicator  2106  may comprise a moisture sensor to detect a cleaning and/or sterilization cycle. In some instances, the usage cycle circuit  2102  monitors the number of reconditioning cycles experienced by the power assembly  2100  and disables the power assembly  2100  after the number of reconditioning cycles exceeds a predetermined threshold. 
     The usage cycle circuit  2102  may be configured to monitor the number of power assembly  2100  exchanges. The usage cycle circuit  2102  increments the usage cycle count each time the power assembly  2100  is exchanged. When the maximum number of exchanges is exceeded the usage cycle circuit  2102  locks out the power assembly  2100  and/or the surgical instrument  2110 . In some instances, when the power assembly  2100  is coupled the surgical instrument  2110 , the usage cycle circuit  2102  identifies the serial number of the power assembly  2100  and locks the power assembly  2100  such that the power assembly  2100  is usable only with the surgical instrument  2110 . In some instances, the usage cycle circuit  2102  increments the usage cycle each time the power assembly  2100  is removed from and/or coupled to the surgical instrument  2110 . 
     In some instances, the usage cycle count corresponds to sterilization of the power assembly  2100 . The use indicator  2106  comprises a sensor configured to detect one or more parameters of a sterilization cycle, such as, for example, a temperature parameter, a chemical parameter, a moisture parameter, and/or any other suitable parameter. The processor  2104  increments the usage cycle count when a sterilization parameter is detected. The usage cycle circuit  2102  disables the power assembly  2100  after a predetermined number of sterilizations. In some instances, the usage cycle circuit  2102  is reset during a sterilization cycle, a voltage sensor to detect a recharge cycle, and/or any suitable sensor. The processor  2104  increments the usage cycle count when a reconditioning cycle is detected. The usage cycle circuit  2102  is disabled when a sterilization cycle is detected. The usage cycle circuit  2102  is reactivated and/or reset when the power assembly  2100  is coupled to the surgical instrument  2110 . In some instances, the use indicator comprises a zero power indicator. The zero power indicator changes state during a sterilization cycle and is checked by the processor  2104  when the power assembly  2100  is coupled to a surgical instrument  2110 . When the zero power indicator indicates that a sterilization cycle has occurred, the processor  2104  increments the usage cycle count. 
     A counter  2108  maintains the usage cycle count. In some instances, the counter  2108  comprises a non-volatile memory module. The processor  2104  increments the usage cycle count stored in the non-volatile memory module each time a usage cycle is detected. The memory module may be accessed by the processor  2104  and/or a control circuit, such as, for example, the control circuit  200 . When the usage cycle count exceeds a predetermined threshold, the processor  2104  disables the power assembly  2100 . In some instances, the usage cycle count is maintained by a plurality of circuit components. For example, in one instance, the counter  2108  comprises a resistor (or fuse) pack. After each use of the power assembly  2100 , a resistor (or fuse) is burned to an open position, changing the resistance of the resistor pack. The power assembly  2100  and/or the surgical instrument  2110  reads the remaining resistance. When the last resistor of the resistor pack is burned out, the resistor pack has a predetermined resistance, such as, for example, an infinite resistance corresponding to an open circuit, which indicates that the power assembly  2100  has reached its usage limit. In some instances, the resistance of the resistor pack is used to derive the number of uses remaining. 
     In some instances, the usage cycle circuit  2102  prevents further use of the power assembly  2100  and/or the surgical instrument  2110  when the usage cycle count exceeds a predetermined usage limit. In one instance, the usage cycle count associated with the power assembly  2100  is provided to an operator, for example, utilizing a screen formed integrally with the surgical instrument  2110 . The surgical instrument  2110  provides an indication to the operator that the usage cycle count has exceeded a predetermined limit for the power assembly  2100 , and prevents further operation of the surgical instrument  2110 . 
     In some instances, the usage cycle circuit  2102  is configured to physically prevent operation when the predetermined usage limit is reached. For example, the power assembly  2100  may comprise a shield configured to deploy over contacts of the power assembly  2100  when the usage cycle count exceeds the predetermined usage limit. The shield prevents recharge and use of the power assembly  2100  by covering the electrical connections of the power assembly  2100 . 
     In some instances, the usage cycle circuit  2102  is located at least partially within the surgical instrument  2110  and is configured to maintain a usage cycle count for the surgical instrument  2110 .  FIG. 22  illustrates one or more components of the usage cycle circuit  2102  within the surgical instrument  2110  in phantom, illustrating the alternative positioning of the usage cycle circuit  2102 . When a predetermined usage limit of the surgical instrument  2110  is exceeded, the usage cycle circuit  2102  disables and/or prevents operation of the surgical instrument  2110 . The usage cycle count is incremented by the usage cycle circuit  2102  when the use indicator  2106  detects a specific event and/or requirement, such as, for example, firing of the surgical instrument  2110 , a predetermined time period corresponding to a single patient procedure time, based on one or more motor parameters of the surgical instrument  2110 , in response to a system diagnostic indicating that one or more predetermined thresholds are met, and/or any other suitable requirement. As discussed above, in some instances, the use indicator  2106  comprises a timing circuit corresponding to a single patient procedure time. In other instances, the use indicator  2106  comprises one or more sensors configured to detect a specific event and/or condition of the surgical instrument  2110 . 
     In some instances, the usage cycle circuit  2102  is configured to prevent operation of the surgical instrument  2110  after the predetermined usage limit is reached. In some instances, the surgical instrument  2110  comprises a visible indicator to indicate when the predetermined usage limit has been reached and/or exceeded. For example, a flag, such as a red flag, may pop-up from the surgical instrument  2110 , such as from the handle, to provide a visual indication to the operator that the surgical instrument  2110  has exceeded the predetermined usage limit. As another example, the usage cycle circuit  2102  may be coupled to a display formed integrally with the surgical instrument  2110 . The usage cycle circuit  2102  displays a message indicating that the predetermined usage limit has been exceeded. The surgical instrument  2110  may provide an audible indication to the operator that the predetermined usage limit has been exceeded. For example, in one instance, the surgical instrument  2110  emits an audible tone when the predetermined usage limit is exceeded and the power assembly  2100  is removed from the surgical instrument  2110 . The audible tone indicates the last use of the surgical instrument  2110  and indicates that the surgical instrument  2110  should be disposed or reconditioned. 
     In some instances, the usage cycle circuit  2102  is configured to transmit the usage cycle count of the surgical instrument  2110  to a remote location, such as, for example, a central database. The usage cycle circuit  2102  comprises a communications module  2112  configured to transmit the usage cycle count to the remote location. The communications module  2112  may utilize any suitable communications system, such as, for example, wired or wireless communications system. The remote location may comprise a central database configured to maintain usage information. In some instances, when the power assembly  2100  is coupled to the surgical instrument  2110 , the power assembly  2100  records a serial number of the surgical instrument  2110 . The serial number is transmitted to the central database, for example, when the power assembly  2100  is coupled to a charger. In some instances, the central database maintains a count corresponding to each use of the surgical instrument  2110 . For example, a bar code associated with the surgical instrument  2110  may be scanned each time the surgical instrument  2110  is used. When the use count exceeds a predetermined usage limit, the central database provides a signal to the surgical instrument  2110  indicating that the surgical instrument  2110  should be discarded. 
     The surgical instrument  2110  may be configured to lock and/or prevent operation of the surgical instrument  2110  when the usage cycle count exceeds a predetermined usage limit. In some instances, the surgical instrument  2110  comprises a disposable instrument and is discarded after the usage cycle count exceeds the predetermined usage limit. In other instances, the surgical instrument  2110  comprises a reusable surgical instrument which may be reconditioned after the usage cycle count exceeds the predetermined usage limit. The surgical instrument  2110  initiates a reversible lockout after the predetermined usage limit is met. A technician reconditions the surgical instrument  2110  and releases the lockout, for example, utilizing a specialized technician key configured to reset the usage cycle circuit  2102 . 
     In some aspects, the segmented circuit  2000  is configured for sequential start-up. An error check is performed by each circuit segment  2002   a - 2002   g  prior to energizing the next sequential circuit segment  2002   a - 2002   g .  FIG. 23  illustrates one example of a process for sequentially energizing a segmented circuit  2270 , such as, for example, the segmented circuit  2000 . When a battery  2008  is coupled to the segmented circuit  2000 , the safety processor  2004  is energized  2272 . The safety processor  2004  performs a self-error check  2274 . When an error is detected  2276   a , the safety processor stops energizing the segmented circuit  2000  and generates an error code  2278   a . When no errors are detected  2276   b , the safety processor  2004  initiates  2278   b  power-up of the primary processor  2006 . The primary processor  2006  performs a self-error check. When no errors are detected, the primary processor  2006  begins sequential power-up of each of the remaining circuit segments  2278   b . Each circuit segment is energized and error checked by the primary processor  2006 . When no errors are detected, the next circuit segment is energized  2278   b . When an error is detected, the safety processor  2004  and/or the primary process stops energizing the current segment and generates an error  2278   a . The sequential start-up continues until all of the circuit segments  2002   a - 2002   g  have been energized. In some examples, the segmented circuit  2000  transitions from sleep mode following a similar sequential power-up process  11250 . 
       FIG. 24  illustrates one aspect of a power segment  2302  comprising a plurality of daisy chained power converters  2314 ,  2316 ,  2318 . The power segment  2302  comprises a battery  2308 . The battery  2308  is configured to provide a source voltage, such as, for example, 12V. A current sensor  2312  is coupled to the battery  2308  to monitor the current draw of a segmented circuit and/or one or more circuit segments. The current sensor  2312  is coupled to an FET switch  2313 . The battery  2308  is coupled to one or more voltage converters  2309 ,  2314 ,  2316 . An always on converter  2309  provides a constant voltage to one or more circuit components, such as, for example, a motion sensor  2322 . The always on converter  2309  comprises, for example, a 3.3V converter. The always on converter  2309  may provide a constant voltage to additional circuit components, such as, for example, a safety processor (not shown). The battery  2308  is coupled to a boost converter  2318 . The boost converter  2318  is configured to provide a boosted voltage above the voltage provided by the battery  2308 . For example, in the illustrated example, the battery  2308  provides a voltage of 12V. The boost converter  2318  is configured to boost the voltage to 13V. The boost converter  2318  is configured to maintain a minimum voltage during operation of a surgical instrument, for example, the surgical instrument  10  ( FIGS. 1-4 ). Operation of a motor can result in the power provided to the primary processor  2306  dropping below a minimum threshold and creating a brownout or reset condition in the primary processor  2306 . The boost converter  2318  ensures that sufficient power is available to the primary processor  2306  and/or other circuit components, such as the motor controller  2343 , during operation of the surgical instrument  10 . In some examples, the boost converter  2318  is coupled directly one or more circuit components, such as, for example, an OLED display  2388 . 
     The boost converter  2318  is coupled to one or more step-down converters to provide voltages below the boosted voltage level. A first voltage converter  2316  is coupled to the boost converter  2318  and provides a first stepped-down voltage to one or more circuit components. In the illustrated example, the first voltage converter  2316  provides a voltage of 5V. The first voltage converter  2316  is coupled to a rotary position encoder  2340 . A FET switch  2317  is coupled between the first voltage converter  2316  and the rotary position encoder  2340 . The FET switch  2317  is controlled by the processor  2306 . The processor  2306  opens the FET switch  2317  to deactivate the position encoder  2340 , for example, during power intensive operations. The first voltage converter  2316  is coupled to a second voltage converter  2314  configured to provide a second stepped-down voltage. The second stepped-down voltage comprises, for example, 3.3V. The second voltage converter  2314  is coupled to a processor  2306 . In some examples, the boost converter  2318 , the first voltage converter  2316 , and the second voltage converter  2314  are coupled in a daisy chain configuration. The daisy chain configuration allows the use of smaller, more efficient converters for generating voltage levels below the boosted voltage level. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
       FIG. 25  illustrates one aspect of a segmented circuit  2400  configured to maximize power available for critical and/or power intense functions. The segmented circuit  2400  comprises a battery  2408 . The battery  2408  is configured to provide a source voltage such as, for example, 12V. The source voltage is provided to a plurality of voltage converters  2409 ,  2418 . An always-on voltage converter  2409  provides a constant voltage to one or more circuit components, for example, a motion sensor  2422  and a safety processor  2404 . The always-on voltage converter  2409  is directly coupled to the battery  2408 . The always-on converter  2409  provides a voltage of 3.3V, for example. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
     The segmented circuit  2400  comprises a boost converter  2418 . The boost converter  2418  provides a boosted voltage above the source voltage provided by the battery  2408 , such as, for example, 13V. The boost converter  2418  provides a boosted voltage directly to one or more circuit components, such as, for example, an OLED display  2488  and a motor controller  2443 . By coupling the OLED display  2488  directly to the boost converter  2418 , the segmented circuit  2400  eliminates the need for a power converter dedicated to the OLED display  2488 . The boost converter  2418  provides a boosted voltage to the motor controller  2443  and the motor  2448  during one or more power intensive operations of the motor  2448 , such as, for example, a cutting operation. The boost converter  2418  is coupled to a step-down converter  2416 . The step-down converter  2416  is configured to provide a voltage below the boosted voltage to one or more circuit components, such as, for example, 5V. The step-down converter  2416  is coupled to, for example, a FET switch  2451  and a position encoder  2440 . The FET switch  2451  is coupled to the primary processor  2406 . The primary processor  2406  opens the FET switch  2451  when transitioning the segmented circuit  2400  to sleep mode and/or during power intensive functions requiring additional voltage delivered to the motor  2448 . Opening the FET switch  2451  deactivates the position encoder  2440  and eliminates the power draw of the position encoder  2440 . The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
     The step-down converter  2416  is coupled to a linear converter  2414 . The linear converter  2414  is configured to provide a voltage of, for example, 3.3V. The linear converter  2414  is coupled to the primary processor  2406 . The linear converter  2414  provides an operating voltage to the primary processor  2406 . The linear converter  2414  may be coupled to one or more additional circuit components. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
     The segmented circuit  2400  comprises a bailout switch  2456 . The bailout switch  2456  is coupled to a bailout door on the surgical instrument  10 . The bailout switch  2456  and the safety processor  2404  are coupled to an AND gate  2419 . The AND gate  2419  provides an input to a FET switch  2413 . When the bailout switch  2456  detects a bailout condition, the bailout switch  2456  provides a bailout shutdown signal to the AND gate  2419 . When the safety processor  2404  detects an unsafe condition, such as, for example, due to a sensor mismatch, the safety processor  2404  provides a shutdown signal to the AND gate  2419 . In some examples, both the bailout shutdown signal and the shutdown signal are high during normal operation and are low when a bailout condition or an unsafe condition is detected. When the output of the AND gate  2419  is low, the FET switch  2413  is opened and operation of the motor  2448  is prevented. In some examples, the safety processor  2404  utilizes the shutdown signal to transition the motor  2448  to an off state in sleep mode. A third input to the FET switch  2413  is provided by a current sensor  2412  coupled to the battery  2408 . The current sensor  2412  monitors the current drawn by the circuit  2400  and opens the FET switch  2413  to shut-off power to the motor  2448  when an electrical current above a predetermined threshold is detected. The FET switch  2413  and the motor controller  2443  are coupled to a bank of FET switches  2445  configured to control operation of the motor  2448 . 
     A motor current sensor  2446  is coupled in series with the motor  2448  to provide a motor current sensor reading to a current monitor  2447 . The current monitor  2447  is coupled to the primary processor  2406 . The current monitor  2447  provides a signal indicative of the current draw of the motor  2448 . The primary processor  2406  may utilize the signal from the motor current  2447  to control operation of the motor, for example, to ensure the current draw of the motor  2448  is within an acceptable range, to compare the current draw of the motor  2448  to one or more other parameters of the circuit  2400  such as, for example, the position encoder  2440 , and/or to determine one or more parameters of a treatment site. In some examples, the current monitor  2447  may be coupled to the safety processor  2404 . 
     In some aspects, actuation of one or more handle controls, such as, for example, a firing trigger, causes the primary processor  2406  to decrease power to one or more components while the handle control is actuated. For example, in one example, a firing trigger controls a firing stroke of a cutting member. The cutting member is driven by the motor  2448 . Actuation of the firing trigger results in forward operation of the motor  2448  and advancement of the cutting member. During firing, the primary processor  2406  closes the FET switch  2451  to remove power from the position encoder  2440 . The deactivation of one or more circuit components allows higher power to be delivered to the motor  2448 . When the firing trigger is released, full power is restored to the deactivated components, for example, by closing the FET switch  2451  and reactivating the position encoder  2440 . 
     In some aspects, the safety processor  2404  controls operation of the segmented circuit  2400 . For example, the safety processor  2404  may initiate a sequential power-up of the segmented circuit  2400 , transition of the segmented circuit  2400  to and from sleep mode, and/or may override one or more control signals from the primary processor  2406 . For example, in the illustrated example, the safety processor  2404  is coupled to the step-down converter  2416 . The safety processor  2404  controls operation of the segmented circuit  2400  by activating or deactivating the step-down converter  2416  to provide power to the remainder of the segmented circuit  2400 . 
       FIG. 26  illustrates one aspect of a power system  2500  comprising a plurality of daisy chained power converters  2514 ,  2516 ,  2518  configured to be sequentially energized. The plurality of daisy chained power converters  2514 ,  2516 ,  2518  may be sequentially activated by, for example, a safety processor during initial power-up and/or transition from sleep mode. The safety processor may be powered by an independent power converter (not shown). For example, in one example, when a battery voltage V BATT  is coupled to the power system  2500  and/or an accelerometer detects movement in sleep mode, the safety processor initiates a sequential start-up of the daisy chained power converters  2514 ,  2516 ,  2518 . The safety processor activates the 13V boost section  2518 . The boost section  2518  is energized and performs a self-check. In some examples, the boost section  2518  comprises an integrated circuit  2520  configured to boost the source voltage and to perform a self check. A diode D prevents power-up of a 5V supply section  2516  until the boost section  2518  has completed a self-check and provided a signal to the diode D indicating that the boost section  2518  did not identify any errors. In some examples, this signal is provided by the safety processor. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
     The 5V supply section  2516  is sequentially powered-up after the boost section  2518 . The 5V supply section  2516  performs a self-check during power-up to identify any errors in the 5V supply section  2516 . The 5V supply section  2516  comprises an integrated circuit  2515  configured to provide a step-down voltage from the boost voltage and to perform an error check. When no errors are detected, the 5V supply section  2516  completes sequential power-up and provides an activation signal to the 3.3V supply section  2514 . In some examples, the safety processor provides an activation signal to the 3.3V supply section  2514 . The 3.3V supply section comprises an integrated circuit  2513  configured to provide a step-down voltage from the 5V supply section  2516  and perform a self-error check during power-up. When no errors are detected during the self-check, the 3.3V supply section  2514  provides power to the primary processor. The primary processor is configured to sequentially energize each of the remaining circuit segments. By sequentially energizing the power system  2500  and/or the remainder of a segmented circuit, the power system  2500  reduces error risks, allows for stabilization of voltage levels before loads are applied, and prevents large current draws from all hardware being turned on simultaneously in an uncontrolled manner. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
     In one aspect, the power system  2500  comprises an over voltage identification and mitigation circuit. The over voltage identification and mitigation circuit is configured to detect a monopolar return current in the surgical instrument and interrupt power from the power segment when the monopolar return current is detected. The over voltage identification and mitigation circuit is configured to identify ground floatation of the power system. The over voltage identification and mitigation circuit comprises a metal oxide varistor. The over voltage identification and mitigation circuit comprises at least one transient voltage suppression diode. 
       FIG. 27  illustrates one aspect of a segmented circuit  2600  comprising an isolated control section  2602 . The isolated control section  2602  isolates control hardware of the segmented circuit  2600  from a power section (not shown) of the segmented circuit  2600 . The control section  2602  comprises, for example, a primary processor  2606 , a safety processor (not shown), and/or additional control hardware, for example, a FET Switch  2617 . The power section comprises, for example, a motor, a motor driver, and/or a plurality of motor MOSFETS. The isolated control section  2602  comprises a charging circuit  2603  and a rechargeable battery  2608  coupled to a 5V power converter  2616 . The charging circuit  2603  and the rechargeable battery  2608  isolate the primary processor  2606  from the power section. In some examples, the rechargeable battery  2608  is coupled to a safety processor and any additional support hardware. Isolating the control section  2602  from the power section allows the control section  2602 , for example, the primary processor  2606 , to remain active even when main power is removed, provides a filter, through the rechargeable battery  2608 , to keep noise out of the control section  2602 , isolates the control section  2602  from heavy swings in the battery voltage to ensure proper operation even during heavy motor loads, and/or allows for real-time operating system (RTOS) to be used by the segmented circuit  2600 . In some examples, the rechargeable battery  2608  provides a stepped-down voltage to the primary processor, such as, for example, 3.3V. The examples, however, are not limited to the particular voltage range(s) described in the context of this specification. 
       FIGS. 28A and 28B  illustrate another aspect of a control circuit  3000  configured to control the powered surgical instrument  10 , illustrated in  FIGS. 1-18A . As shown in  FIGS. 18A, 28B , the handle assembly  14  may include a motor  3014  which can be controlled by a motor driver  3015  and can be employed by the firing system of the surgical instrument  10 . In various forms, the motor  3014  may be a DC brushed driving motor having a maximum rotation of, approximately, 25,000 RPM, for example. In other arrangements, the motor  3014  may include a brushless motor, a cordless motor, a synchronous motor, a stepper motor, or any other suitable electric motor. In certain circumstances, the motor driver  3015  may comprise an H-Bridge FETs  3019 , as illustrated in  FIGS. 28A and 28B , for example. The motor  3014  can be powered by a power assembly  3006 , which can be releasably mounted to the handle assembly  14 . The power assembly  3006  is configured to supply control power to the surgical instrument  10 . The power assembly  3006  may comprise a battery which may include a number of battery cells connected in series that can be used as the power source to power the surgical instrument  10 . In such configuration, the power assembly  3006  may be referred to as a battery pack. In certain circumstances, the battery cells of the power assembly  3006  may be replaceable and/or rechargeable. In at least one example, the battery cells can be Lithium-Ion batteries which can be separably couplable to the power assembly  3006 . 
     Examples of drive systems and closure systems that are suitable for use with the surgical instrument  10  are disclosed in U.S. Provisional Patent Application Ser. No. 61/782,866, entitled CONTROL SYSTEM OF A SURGICAL INSTRUMENT, and filed Mar. 14, 2013, the entire disclosure of which is incorporated by reference herein in its entirety. For example, the electric motor  3014  can include a rotatable shaft (not shown) that may operably interface with a gear reducer assembly that can be mounted in meshing engagement with a set, or rack, of drive teeth on a longitudinally-movable drive member. In use, a voltage polarity provided by the battery can operate the electric motor  3014  to drive the longitudinally-movable drive member to effectuate the end effector  300 . For example, the motor  3014  can be configured to drive the longitudinally-movable drive member to advance a firing mechanism to fire staples into tissue captured by the end effector  300  from a staple cartridge assembled with the end effector  300  and/or advance a cutting member to cut tissue captured by the end effector  300 , for example. 
     As illustrated in  FIGS. 28A and 28B  and as described below in greater detail, the power assembly  3006  may include a power management controller which can be configured to modulate the power output of the power assembly  3006  to deliver a first power output to power the motor  3014  to advance the cutting member while the interchangeable shaft  200  is coupled to the handle assembly  14  ( FIG. 1 ) and to deliver a second power output to power the motor  3014  to advance the cutting member while the interchangeable shaft assembly  200  is coupled to the handle assembly  14 , for example. Such modulation can be beneficial in avoiding transmission of excessive power to the motor  3014  beyond the requirements of an interchangeable shaft assembly that is coupled to the handle assembly  14 . 
     In certain circumstances, the interface  3024  can facilitate transmission of the one or more communication signals between the power management controller  3016  and the shaft assembly controller  3022  by routing such communication signals through a main controller  3017  residing in the handle assembly  14  ( FIG. 1 ), for example. In other circumstances, the interface  3024  can facilitate a direct line of communication between the power management controller  3016  and the shaft assembly controller  3022  through the handle assembly  14  while the shaft assembly  200  ( FIG. 1 ) and the power assembly  3006  are coupled to the handle assembly  14 . 
     In one instance, the main microcontroller  3017  may be any single core or multicore processor such as those known under the trade name ARM Cortex by Texas Instruments. In one instance, the surgical instrument  10  ( FIGS. 1-4 ) may comprise a power management controller  3016  such as, for example, a safety microcontroller platform comprising two microcontroller-based families such as TMS570 and RM4x known under the trade name Hercules ARM Cortex R4, also by Texas Instruments. Nevertheless, other suitable substitutes for microcontrollers and safety processor may be employed, without limitation. In one instance, the safety processor  2004  ( FIG. 21A ) may be configured specifically for IEC 61508 and ISO 26262 safety critical applications, among others, to provide advanced integrated safety features while delivering scalable performance, connectivity, and memory options. 
     In certain instances, the microcontroller  3017  may be an LM 4F230H5QR, available from Texas Instruments, for example. In at least one example, the Texas Instruments LM4F230H5QR is an ARM Cortex-M4F Processor Core comprising on-chip memory of 256 KB single-cycle flash memory, or other non-volatile memory, up to 40 MHz, a prefetch buffer to improve performance above 40 MHz, a 32 KB single-cycle serial random access memory (SRAM), internal read-only memory (ROM) loaded with StellarisWare® software, 2 KB electrically erasable programmable read-only memory (EEPROM), one or more pulse width modulation (PWM) modules, one or more quadrature encoder inputs (QEI) analog, one or more 12-bit Analog-to-Digital Converters (ADC) with  12  analog input channels, among other features that are readily available for the product datasheet. The present disclosure should not be limited in this context. 
       FIG. 29  is a block diagram the surgical instrument of  FIG. 1  illustrating interfaces between the handle assembly  14  ( FIG. 1 ) and the power assembly and between the handle assembly  14  and the interchangeable shaft assembly. As shown in  FIG. 29 , the power assembly  3006  may include a power management circuit  3034  which may comprise the power management controller  3016 , a power modulator  3038 , and a current sense circuit  3036 . The power management circuit  3034  can be configured to modulate power output of the battery  3007  based on the power requirements of the shaft assembly  200  ( FIG. 1 ) while the shaft assembly  200  and the power assembly  3006  are coupled to the handle assembly  14 . For example, the power management controller  3016  can be programmed to control the power modulator  3038  of the power output of the power assembly  3006  and the current sense circuit  3036  can be employed to monitor power output of the power assembly  3006  to provide feedback to the power management controller  3016  about the power output of the battery  3007  so that the power management controller  3016  may adjust the power output of the power assembly  3006  to maintain a desired output. 
     It is noteworthy that the power management controller  3016  and/or the shaft assembly controller  3022  each may comprise one or more processors and/or memory units which may store a number of software modules. Although certain modules and/or blocks of the surgical instrument  14  ( FIG. 1 ) may be described by way of example, it can be appreciated that a greater or lesser number of modules and/or blocks may be used. Further, although various instances may be described in terms of modules and/or blocks to facilitate description, such modules and/or blocks may be implemented by one or more hardware components, e.g., processors, Digital Signal Processors (DSPs), Programmable Logic Devices (PLDs), Application Specific Integrated Circuits (ASICs), circuits, registers and/or software components, e.g., programs, subroutines, logic and/or combinations of hardware and software components. 
     In certain instances, the surgical instrument  10  ( FIGS. 1-4 ) may comprise an output device  3042  which may include one or more devices for providing a sensory feedback to a user. Such devices may comprise, for example, visual feedback devices (e.g., an LCD display screen, LED indicators), audio feedback devices (e.g., a speaker, a buzzer) or tactile feedback devices (e.g., haptic actuators). In certain circumstances, the output device  3042  may comprise a display  3043  which may be included in the handle assembly  14  ( FIG. 1 ). The shaft assembly controller  3022  and/or the power management controller  3016  can provide feedback to a user of the surgical instrument  10  through the output device  3042 . The interface  3024  can be configured to connect the shaft assembly controller  3022  and/or the power management controller  3016  to the output device  3042 . The reader will appreciate that the output device  3042  can instead be integrated with the power assembly  3006 . In such circumstances, communication between the output device  3042  and the shaft assembly controller  3022  may be accomplished through the interface  3024  while the shaft assembly  200  is coupled to the handle assembly  14 . 
     Having described a surgical instrument  10  ( FIGS. 1-4 ) and various control circuits  2000 ,  3000  for controlling the operation thereof, the disclosure now turns to various specific configurations of the surgical instrument  10  and control circuits  2000  (or  3000 ). 
     In various aspects, the present disclosure provides techniques for monitoring the speed and precision incrementing of the drive motor in the instrument  10  (described in connection with  FIGS. 1-29 ). In one example, a magnet can be placed on a planet frame of one of the stages of gear reduction with an inductance sensor on the gear housing. In another example, placing the magnet and magnetic field sensor on the last stage would provide the most precise incremental movement monitoring. 
     Conventional motor control systems employ encoders to detect the location and speed of the motor in hand held battery powered endosurgical instruments such as powered endocutter/stapler devices. Precision operation of endocutter/stapler devices relies in part on the ability to verify the motor operation under load. Simple sensor implementations may be employed to achieve verify the motor operation under load. 
     Accordingly, the present disclosure includes a magnetic body on one of the planetary carriers of a gear reduction system or employ brushless motor technology. Both approaches involve the placement of an inductance sensor on the outside housing of the motor or planetary gear system. In the case of a brushless motor there are electromagnetic field coils (windings, inductors, etc.) arrayed radially around the center magnetic shaft of the motor. The coils are sequentially activated and deactivated to drive the central motor shaft. One or more inductance sensors can be placed outside of the motor and adjacent to at least some of the coils to sense the activation/deactivation cycles of the motor windings to determine the number times the shaft has been rotated. Alternatively, a permanent magnet can be placed on one of the planetary carriers and the inductance sensor can be placed adjacent to the radial path of the planetary carrier to measure the number of times that stage of the gear train is rotated. This implementation can be applied to any rotational components in the system with increasingly more resolution possible in regions with a relatively large number of rotations during function, or as the rotational components become closer (in terms of number of connections) to the end effector depending on the design. The gear train sensing method may be preferred since it actually measures rotation of one of the stages whereas the motor sensing method senses the number of times the motor has been commanded to energize, rather than the actual shaft rotation. For example, if the motor is stalled under high load, the motor sensing method would not be able to detect the lack of rotation because it senses only the energizing cycles not shaft rotation. Nevertheless, both techniques can be employed in a cost effective manner to sense motor rotation. 
     During stapling, for example, tissue is firmly clamped between opposing jaws before a staple is driven into the clamped tissue. Tissue compression during clamping can cause fluid to be displaced from the compressed tissue, and the rate or amount of displacement varies depending on tissue type, tissue thickness, the surgical operation (e.g., clamping pressure and clamping time). In various instances, fluid displacement between the opposing jaws of an end effector may contribute to malformation (e.g., bending) of staples between the opposing jaws. Accordingly, in various instances, it may be desirable to control the firing stroke, e.g., to control the firing speed, in relationship to the detected fluid flow, or lack thereof, intermediate opposing jaws of a surgical end effector. 
     Accordingly, also provided herein are methods, devices, and systems for monitoring speed and incremental movement of a surgical instrument drive train, which in turn provides information about the operational velocity of the device (e.g., jaw closure, stapling). In accordance with the present examples, the instrument  10  ( FIGS. 1-4 ) does not include a motor encoder. Rather, the instrument  10  is equipped with a motor  7012  shown in  FIG. 30 , which illustrates a speed sensor assembly for a power train  7010  of the motor  7012 , in accordance with an illustrative example. The speed sensor assembly can include a motor  7012  having an output shaft  7014  that is coupled directly or indirectly to a drive shaft. In some examples, the output shaft is connected to a gear reduction assembly, such as the planetary gear train  7020  shown in  FIG. 30 . 
     With continued reference to  FIG. 30 , the speed sensor assembly further includes at least one sensor  7016  that detects the rotational speed of any suitable component of the system. For example, the sensor may be a proximity sensor, such as an induction sensor, which detects movement of one or more detectable elements  7018  affixed to any rotating part of the gear reduction assembly. In  FIG. 30 , which is exemplary, the detectable element is affixed to the last stage annular gear  7034   c  and the sensor is positioned adjacent the radial path of the detectable element so as to detect movement of the detectable element.  FIG. 30  is exemplary only—rotating components vary depending on design—and the sensor(s) can be affixed to any rotating component of the gear reduction assembly. For example, in another example, a detectable element is associated with the carrier gear of the final stage or even the drive gear. In some examples, a detectable element is located outside of the gear reduction assembly, such as on the driveshaft between gear reduction assembly and the end effector. In some example, a detectable element is located on a rotating component in the final gear reduction at the end effector. 
     With continued reference to  FIG. 30 , in one aspect motor  7012  is rotationally coupled to a gear reduction assembly, such as a planetary gear train  7020 . However, any suitable gear reduction or transmission can be used and/or the motor can be coupled directly to a drive shaft (e.g., direct drive). The planetary gear train can include 1, 2, 3, 4, 5, or more stages. The planetary gear train illustrated in  FIG. 30  has three stages. The planetary gear train is driven by a sun gear ( 7042  in  FIG. 31 ) attached directly or indirectly to the motor output shaft  7014 . The sun gear drives one or more first stage planet gears  7032   a , which in turn engage a first stage annular gear  7034   a . Any number of planet gears can be used such as, for example, 1, 2, 3, 4, 5 or more planet gears. First stage planet gears  7032   a  communicate with a first stage carrier  7036   a , which includes or connects to a second stage sun gear ( 7038   a  in  FIG. 31 ) that drives the second stage. 
     Similar to the first stage, the second stage includes one or more planet gears  7032   b , an annular gear  7034   b , and a carrier  7036   b  that includes or connects to a third stage sun gear ( 7038   b  in  FIG. 31 ) that drives the third stage. Likewise, the third stage includes one or more planet gears  7032   c , an annular gear  7034   c , and a carrier  7036   c . The final stage in the planetary gear train assembly is connected to a drive gear  7040 , which can be the final effector in the gear reduction assembly, depending on design. The use of three planetary gear stages is exemplary only. Any suitable type of gear reduction assembly can be used in accordance with the present disclosure. 
     The sensor  7016  can be mounted in or near the gear reduction assembly in, near, or adjacent the radial path of detectable element  7018 . The sensor can be any suitable sensor type capable of detecting rotational speed without an encoder. The sensor is used in conjunction with a detectable element capable of being detected by the sensor. For example, in some examples, the sensor is an inductance sensor and the detectable element is a metallic element. The inductance sensor can be configured to detect a change in inductance caused by a metallic object or magnet passing adjacent the inductive sensor. In some examples, the sensor is a magnetic field sensor, and the detectable element is a magnetic element. A magnetic field sensor can be configured to detect changes in a magnetic field surrounding the magnetic field sensor caused by the movement of the magnetic element. 
     Detectable elements can be affixed or integral with any rotating part or particular stage of the gear reduction assembly to measure the number of times that the part or stage rotates. For example, a single detectable element could be placed on drive gear  7040 . Each complete rotation of the drive gear would cause the detectable element to pass the sensor one time, resulting in one detected rotation. In some examples, multiple detectable elements  7018  can be used within the same gear reduction assembly, by placing a plurality of detectable elements (e.g., 2, 3, 4, 5 or more) on the same component (e.g., a gear) and/or by placing one or more detectable elements on a plurality of different components (e.g., on two different gears). Placing multiple sensors equally spaced on a single component can provide refined information about incremental rotations. Similarly, resolution of speed monitoring can be increased by placing a detectable element(s) on a component that rotates more quickly relative to other components and/or by placing the detectable element closer (in terms of number of connections) to the end effector depending on the design. Using multiple detectable elements on different components provides a redundant, fail-safe system should one sensor or detectable element fail. 
     Sensors should be located close enough to detectable elements to ensure that each revolution of a detectable element is captured by its associated sensor. Multiple sensors can be placed in the same radial path of a detectable element. In addition, if detectable elements are placed on a plurality of different components (e.g., two different gears), a sensor can be placed adjacent the radial path of each detectable element. The sensor  7016  is in data communication with a controller  7011  such as the microcontroller  1500  ( FIG. 19 ) or microcontroller  2006  ( FIGS. 21A, 21B ), processor  2104  ( FIG. 22 ), or controller  2606  and  3017  shown in  FIGS. 27-29 , which is programmed to translate the number and/or rate of detection events into a speed reading useful to the user, such as using the speed indicator display shown in  FIGS. 34-36 . 
       FIG. 31  shows a longitudinal cross section through plane A of  FIG. 30 . Clearly visible in  FIG. 31  is sun gear  7042  coupled to output shaft  7014 . 
       FIG. 32  illustrates a speed sensor assembly for  7050  for directly sensing the rotational speed of a brushless motor  7060 , in accordance with an illustrative aspect. A brushless motor typically comprises electromagnetic field coils  7062 ,  7064  arrayed radially around a central magnetic shaft ( 7066  in  FIG. 33 ). Negative  7062  and positive  7064  coils are alternately arranged around the central magnetic shaft, and these coils are sequentially activated and deactivated to drive the central magnetic shaft. One or more sensors  7016  can be placed adjacent these coils on the outside of the motor to monitor motor speed. The sensor induction field  7068  is affected each time an electromagnetic field coil passes the sensor. The sensor is in data communication with a controller  7011 , such as the microcontroller  1500  ( FIG. 19 ) or microcontroller  2006  ( FIGS. 21A, 21B ), processor  2104  ( FIG. 22 ), or controller  2606  and  3017  shown in  FIGS. 27-29 , for example, which is programmed to translate the number and/or rate of detection events into a speed reading useful to the user, such as using a speed indicator display shown in  FIGS. 88-90 . 
     If the motor stalls, for example under high load, the sensor  7016  may still detect activation of the coils, which the sensor  7016  would interpret as motor rotation even though the motor is stalled. As a result, under certain operational circumstances, motor speed could be an inaccurate readout for operational tool speed. In one example, speed is measured using one or more sensors  7016  on the gear reduction assembly because this measures the actual speed of the gear assembly, or a stage of the gear assembly, rather than the speed of the motor. In addition, the closer the detectable element(s) and associated sensor(s) are to the end effector, the more likely the sensed speed accurately reflects operational tool speed. The ability to verify motor operation under load is important for precision operation of surgical instruments, such as staplers. 
       FIG. 33  illustrates a transverse cross section through plane B of the motor assembly shown in  FIG. 32 . The central magnetic shaft  7066  is visible in  FIG. 33 . 
     Sensor  7016  is in data communication with a controller  7011 , such as the microcontroller  1500  ( FIG. 19 ) or microcontroller  2006  ( FIGS. 21A, 21B ), processor  2104  ( FIG. 22 ), or controller  2606  and  3017  shown in  FIGS. 27-29 , which is programmed to translate the number and/or rate of detection events into a speed reading useful to the user. The controller  7011  also can regulate motor speed to ensure safe operating parameters and/or to ensure that a constant speed and/or acceleration are maintained for particular surgical applications. 
     Various functions may be implemented utilizing the circuitry previously described, For example, the motor may be controlled with a motor controller  7011  similar those described in connection with  FIGS. 21A, 21B, 24, 25, 28A, 28B, and 29 , where the encoder is replaced with the monitoring speed control and precision incrementing of motor systems for powered surgical instruments described in connection with  FIGS. 30-33 . For example, the position encoder  2340  shown in  FIG. 24  can be replaced with the sensor  7016  shown in  FIGS. 30-33  coupled to the microcontroller  2306  in  FIG. 24 . Similarly, the position encoder  2440  shown in  FIG. 25  can be replaced with the sensor  7016  shown in  FIGS. 30-33  coupled to the microcontroller  2406  in  FIG. 25 . 
     In one aspect, as illustrated in  FIGS. 34-36 , the feedback indicator  9066  includes a dial  9096  and a pointer  9098  movable between a plurality positions relative to the dial  9096 . The dial  9096  is divided to define an optimal zone, a so-called “TOO FAST” zone, and a so-called “TOO SLOW” zone. The pointer  9098  can be set to one of a plurality of positions within the three zones. In one example, as illustrated in  FIG. 34 , the pointer is set to a position in the “TOO SLOW” zone to alert the operator that a selected speed of advancement of the cutting member  9040  through the tissue captured by the end effector  9012  is below an optimal or a desired zone. As described above, such a characterization of the selected speed can be performed by the microcontroller  9061  based on one or more measurements of one or more parameters of the end effector  9012 . In another example, perhaps after the operator increases the speed of the cutting member  9040  in response to the previous alert, the pointer is moved to a new position in the “TOO FAST” zone, as illustrated in  FIG. 35 , to alert the operator that a newly selected speed of the cutting member  9040  exceeds the optimal zone. The operator may continue to adjust the speed of the cutting member  9040  by adjusting the position of the firing trigger  9094  until the pointer lands in the optimal zone, as illustrated in  FIG. 36 . At such point, the operator may maintain the current position of the firing trigger  9094  for the remainder of the firing stroke. 
     The present disclosure will now be described in connection with various examples and combinations of such examples as set forth hereinbelow. 
     1. One example provides a motor speed control system comprising: a motor having an output shaft; a gear reduction assembly operably coupled to the output shaft; a detectable element located in the gear reduction assembly; and at least one sensor to sense the detectable element, the at least one sensor placed in the radial path of the detectable element, the at least one sensor in data communication with a controller configured to receive a signal from the at least one sensor and to control the speed of the output shaft. 
     2. Another example provides the motor speed control system of example 1, wherein the gear reduction assembly comprises a planetary gear train. 
     3. Another example provides the motor speed control system of examples 1 or 2, wherein the planetary gear train comprises a first stage, wherein the planetary gear train is driven by a sun gear attached directly or indirectly to the motor output shaft, and wherein the sun gear drives one or more first stage planet gears, which in turn engage a first stage annular gear. 
     4. Another example provides the motor speed control system of any one of examples 1-3, comprising a first stage carrier in communication with the first stage planet gears, the first stage carrier includes or connects to a second stage sun gear that drives the second stage. 
     5. Another example provides the motor speed control system of any one of example 2-4, wherein the planetary gear train comprises at least one stage connected to a drive gear, which is configured as a final effector in the gear reduction assembly. 
     6. Another example provides the motor speed control system of example 5, wherein a single detectable element is placed on the drive gear. 
     7. Another example provides the motor speed control system of any one of examples 1-6, wherein the detectable element can be affixed or integral with any rotating part or particular stage of the gear reduction assembly to measure the number of times that the rotating part or stage rotates. 
     8. Another example provides the motor speed control system of any one of examples 1-7, wherein the at least one sensor is an inductance sensor and the detectable element is a metallic element. 
     9. Another example provides the motor speed control system of example 8, wherein the inductance sensor is configured to detect a change in inductance caused by the metallic element passing adjacent the inductive sensor. 
     10. Another example provides the motor control system of any one of examples 1-9, wherein the sensor is a magnetic field sensor and the detectable element is a magnetic element. 
     11. Yet another example provides a motor speed control system comprising: a brushless motor having a housing and an output shaft, the brushless motor comprising electromagnetic field coils arrayed radially around a central magnetic shaft; a gear reduction assembly operably coupled to the output shaft; and at least one sensor placed in proximity to the brushless motor, the at least one sensor in data communication with a controller configured to receive a signal from the at least one sensor and to control the speed of the output shaft. 
     12. Another example provides the motor speed control system of example 11, comprising negative and positive electromagnetic field coils alternately arranged around the central magnetic shaft, wherein the coils are sequentially activated and deactivated to drive the central magnetic shaft. 
     13. Another example provides the motor speed control system of examples 11 or 12, wherein the at least one sensor is placed adjacent to the negative and positive electromagnetic field coils outside the housing of the brushless motor to monitor motor speed. 
     14. Yet another example provides a powered surgical instrument comprising: a motor having an output shaft; a motor speed control system in communication with the motor; at least one sensor to detect the speed of the motor; and a controller configured to receive a signal from the at least one sensor and configured to control the speed of the output shaft. 
     15. Another example provides the powered surgical instrument of example 14, wherein the motor speed control system comprises: a gear reduction assembly operably coupled to the output shaft; and a detectable element located in the gear reduction assembly; wherein the at least one sensor is configured to sense the detectable element, the at least one sensor placed in the radial path of the detectable element. 
     16. Another example provides the powered surgical instrument of example 15, wherein the gear reduction assembly comprises a planetary gear train. 
     17. Another example provides the powered surgical instrument of example 16, wherein the planetary gear train comprises a first stage, wherein the planetary gear train is driven by a sun gear attached directly or indirectly to the motor output shaft, and wherein the sun gear drives one or more first stage planet gears, which in turn engage a first stage annular gear. 
     18. Another example provides the powered surgical instrument of any one of examples 14-17, wherein the motor speed control system comprises: a brushless motor having a housing and an output shaft, the brushless motor comprising electromagnetic field coils arrayed radially around a central magnetic shaft; a gear reduction assembly operably coupled to the output shaft; and at least one sensor placed in proximity to the brushless motor, the at least one sensor in data communication with a controller configured to receive a signal from the sensor and to control the speed of the output shaft. 
     19. Another example provides the powered surgical instrument of example 18, comprising negative and positive electromagnetic field coils alternately arranged around the central magnetic shaft, wherein the coils are sequentially activated and deactivated to drive the central magnetic shaft. 
     20. Another example provides the powered surgical instrument of example 19, wherein the at least one sensor is placed adjacent to the negative and positive electromagnetic field coils outside the housing of the brushless motor to monitor motor speed. 
     In accordance with various examples, the surgical instruments described herein may comprise one or more processors (e.g., microprocessor, microcontroller) coupled to various sensors. In addition, to the processor(s), a storage (having operating logic) and communication interface, are coupled to each other. 
     As described earlier, the sensors may be configured to detect and collect data associated with the surgical device. The processor processes the sensor data received from the sensor(s). 
     The processor may be configured to execute the operating logic. The processor may be any one of a number of single or multi-core processors known in the art. The storage may comprise volatile and non-volatile storage media configured to store persistent and temporal (working) copy of the operating logic. 
     In various aspects, the operating logic may be configured to perform the initial processing, and transmit the data to the computer hosting the application to determine and generate instructions. For these examples, the operating logic may be further configured to receive information from and provide feedback to a hosting computer. In alternate examples, the operating logic may be configured to assume a larger role in receiving information and determining the feedback. In either case, whether determined on its own or responsive to instructions from a hosting computer, the operating logic may be further configured to control and provide feedback to the user. 
     In various aspects, the operating logic may be implemented in instructions supported by the instruction set architecture (ISA) of the processor, or in higher level languages and compiled into the supported ISA. The operating logic may comprise one or more logic units or modules. The operating logic may be implemented in an object oriented manner. The operating logic may be configured to be executed in a multi-tasking and/or multi-thread manner. In other examples, the operating logic may be implemented in hardware such as a gate array. 
     In various aspects, the communication interface may be configured to facilitate communication between a peripheral device and the computing system. The communication may include transmission of the collected biometric data associated with position, posture, and/or movement data of the user&#39;s body part(s) to a hosting computer, and transmission of data associated with the tactile feedback from the host computer to the peripheral device. In various examples, the communication interface may be a wired or a wireless communication interface. An example of a wired communication interface may include, but is not limited to, a Universal Serial Bus (USB) interface. An example of a wireless communication interface may include, but is not limited to, a Bluetooth interface. 
     For various aspects, the processor may be packaged together with the operating logic. In various examples, the processor may be packaged together with the operating logic to form a SiP. In various examples, the processor may be integrated on the same die with the operating logic. In various examples, the processor may be packaged together with the operating logic to form a System on Chip (SoC). 
     Various aspects may be described herein in the general context of computer executable instructions, such as software, program modules, and/or engines being executed by a processor. Generally, software, program modules, and/or engines include any software element arranged to perform particular operations or implement particular abstract data types. Software, program modules, and/or engines can include routines, programs, objects, components, data structures and the like that perform particular tasks or implement particular abstract data types. An implementation of the software, program modules, and/or engines components and techniques may be stored on and/or transmitted across some form of computer-readable media. In this regard, computer-readable media can be any available medium or media useable to store information and accessible by a computing device. Some examples also may be practiced in distributed computing environments where operations are performed by one or more remote processing devices that are linked through a communications network. In a distributed computing environment, software, program modules, and/or engines may be located in both local and remote computer storage media including memory storage devices. A memory such as a random access memory (RAM) or other dynamic storage device may be employed for storing information and instructions to be executed by the processor. The memory also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. 
     Although some aspects may be illustrated and described as comprising functional components, software, engines, and/or modules performing various operations, it can be appreciated that such components or modules may be implemented by one or more hardware components, software components, and/or combination thereof. The functional components, software, engines, and/or modules may be implemented, for example, by logic (e.g., instructions, data, and/or code) to be executed by a logic device (e.g., processor). Such logic may be stored internally or externally to a logic device on one or more types of computer-readable storage media. In other examples, the functional components such as software, engines, and/or modules may be implemented by hardware elements that may include processors, microprocessors, circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, and so forth), integrated circuits, ASICs, PLDs, DSPs, FPGAs, logic gates, registers, semiconductor device, chips, microchips, chip sets, and so forth. 
     Examples of software, engines, and/or modules may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, functions, methods, procedures, software interfaces, application program interfaces (API), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. Determining whether one example is implemented using hardware elements and/or software elements may vary in accordance with any number of factors, such as desired computational rate, power levels, heat tolerances, processing cycle budget, input data rates, output data rates, memory resources, data bus speeds and other design or performance constraints. 
     One or more of the modules described herein may comprise one or more embedded applications implemented as firmware, software, hardware, or any combination thereof. One or more of the modules described herein may comprise various executable modules such as software, programs, data, drivers, application APIs, and so forth. The firmware may be stored in a memory of the controller and/or the controller which may comprise a nonvolatile memory (NVM), such as in bit-masked ROM or flash memory. In various implementations, storing the firmware in ROM may preserve flash memory. The NVM may comprise other types of memory including, for example, programmable ROM (PROM), erasable programmable ROM (EPROM), EEPROM, or battery backed RAM such as dynamic RAM (DRAM), Double-Data-Rate DRAM (DDRAM), and/or synchronous DRAM (SDRAM). 
     In some cases, various aspects may be implemented as an article of manufacture. The article of manufacture may include a computer readable storage medium arranged to store logic, instructions and/or data for performing various operations of one or more examples. In various examples, for example, the article of manufacture may comprise a magnetic disk, optical disk, flash memory or firmware containing computer program instructions suitable for execution by a general purpose processor or application specific processor. The examples, however, are not limited in this context. 
     The functions of the various functional elements, logical blocks, modules, and circuits elements described in connection with the examples disclosed herein may be implemented in the general context of computer executable instructions, such as software, control modules, logic, and/or logic modules executed by the processing unit. Generally, software, control modules, logic, and/or logic modules comprise any software element arranged to perform particular operations. Software, control modules, logic, and/or logic modules can comprise routines, programs, objects, components, data structures and the like that perform particular tasks or implement particular abstract data types. An implementation of the software, control modules, logic, and/or logic modules and techniques may be stored on and/or transmitted across some form of computer-readable media. In this regard, computer-readable media can be any available medium or media useable to store information and accessible by a computing device. Some examples also may be practiced in distributed computing environments where operations are performed by one or more remote processing devices that are linked through a communications network. In a distributed computing environment, software, control modules, logic, and/or logic modules may be located in both local and remote computer storage media including memory storage devices. 
     Additionally, it is to be appreciated that the aspects described herein illustrate example implementations, and that the functional elements, logical blocks, modules, and circuits elements may be implemented in various other ways which are consistent with the described examples. Furthermore, the operations performed by such functional elements, logical blocks, modules, and circuits elements may be combined and/or separated for a given implementation and may be performed by a greater number or fewer number of components or modules. As will be apparent to those of skill in the art upon reading the present disclosure, each of the individual examples described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several aspects without departing from the scope of the present disclosure. Any recited method can be carried out in the order of events recited or in any other order which is logically possible. 
     It is worthy to note that any reference to “one example” or “an example” means that a particular feature, structure, or characteristic described in connection with the example is comprised in at least one example. The appearances of the phrase “in one example” or “in one aspect” in the specification are not necessarily all referring to the same example. 
     Unless specifically stated otherwise, it may be appreciated that terms such as “processing,” “computing,” “calculating,” “determining,” or the like, refer to the action and/or processes of a computer or computing system, or similar electronic computing device, such as a general purpose processor, a DSP, ASIC, FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein that manipulates and/or transforms data represented as physical quantities (e.g., electronic) within registers and/or memories into other data similarly represented as physical quantities within the memories, registers or other such information storage, transmission or display devices. 
     It is worthy to note that some aspects may be described using the expression “coupled” and “connected” along with their derivatives. These terms are not intended as synonyms for each other. For example, some aspects may be described using the terms “connected” and/or “coupled” to indicate that two or more elements are in direct physical or electrical contact with each other. The term “coupled,” however, also may mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. With respect to software elements, for example, the term “coupled” may refer to interfaces, message interfaces, API, exchanging messages, and so forth. 
     It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. 
     The present disclosure applies to conventional endoscopic and open surgical instrumentation as well as application in robotic-assisted surgery. 
     Aspects of the devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. Examples may, in either or both cases, be reconditioned for reuse after at least one use. Reconditioning may include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, examples of the device may be disassembled, and any number of the particular pieces or parts of the device may be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, examples of the device may be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device may utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application. 
     By way of example only, aspects described herein may be processed before surgery. First, a new or used instrument may be obtained and when necessary cleaned. The instrument may then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and instrument may then be placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation may kill bacteria on the instrument and in the container. The sterilized instrument may then be stored in the sterile container. The sealed container may keep the instrument sterile until it is opened in a medical facility. A device also may be sterilized using any other technique known in the art, including but not limited to beta or gamma radiation, ethylene oxide, plasma peroxide, or steam. 
     One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken limiting. 
     With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity. 
     The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely examples and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically matable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. 
     Some aspects may be described using the expression “coupled” and “connected” along with their derivatives. It should be understood that these terms are not intended as synonyms for each other. For example, some aspects may be described using the term “connected” to indicate that two or more elements are in direct physical or electrical contact with each other. In another example, some aspects may be described using the term “coupled” to indicate that two or more elements are in direct physical or electrical contact. The term “coupled,” however, also may mean that two or more elements are not in direct contact with each other, but yet still co-operate or interact with each other. 
     In some instances, one or more components may be referred to herein as “configured to,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to,” “conformable/conformed to,” etc. Those skilled in the art will recognize that “configured to” can generally encompass active-state components and/or inactive-state components and/or standby-state components, unless context requires otherwise. 
     While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that when a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. 
     In addition, even when a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” 
     With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. 
     In summary, numerous benefits have been described which result from employing the concepts described herein. The foregoing disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or limiting to the precise form disclosed. Modifications or variations are possible in light of the above teachings. The one or more examples were chosen and described in order to illustrate principles and practical application to thereby enable one of ordinary skill in the art to utilize the various examples and with various modifications as are suited to the particular use contemplated. It is intended that the claims submitted herewith define the overall scope.