Abstract:
A system and method for mechanically coupling an energy harvester to strength training type exercise equipment is disclosed. An energy harvester with unwanted vibration forces is mechanically isolated from exercise equipment by a system comprising a plurality of mechanically compliant vibration isolators and a ballast mass; a flexible cord, pre-loaded with a near constant force spring is used to transmit motion from the weight stack to the energy harvester; the flexible cord has a force limiting feature to pre-excessive force from being transmitted from the energy harvester to the weight stack during an exercise motion.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/935,853, filed 5 Feb. 2014, and entitled “Exercise Equipment With Coupling To An Energy Harvester,” which is incorporated herein by reference in its entirety. 
         [0002]    This application also claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 61/941,455, filed 18 Feb. 2014, and entitled “Exercise Equipment With Coupling To An Energy Harvester,” which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    This invention relates generally to the field of exercise equipment, and more specifically, exercise equipment having an electrical generating means. Systems and methods to produce electrical power derived from a human exercise motion, herein referred to as human-input, are known and have been reduced to practice in commercial exercise equipment products. Commercial has generally been limited to exercise products intended for cardiovascular exercise such as stationary bicycles. prior devices used for converting kinetic energy caused by human input generally includes at least one electrical generator and associated control and/or display electronics; these devices are generally referred to as an energy harvester in this disclosure. The electrical power produced is often used to provide power to an electronics load, generally known as fitness feedback electronics, typically comprising LCD displays, sensors, and communication electronics. In some examples, the equipment derives electrical power entirely from the human input, without a need to plug into an external electrical outlet. In exercise equipment that is of the strength training type, methods to produce electrical power by converting human input have been disclosed in prior literature, however the methods have generally had substantial limitations in performance. 
         [0004]    For instance, prior systems and methods employ energy harvesters that couple directly and rigidly to a translating or rotating member of the equipment in a manner that may cause undesired ripple forces and torques. That is, that arise during a process of electromechanical energy conversion are transmitted to the user, either through the seat or the user&#39;s grip, resulting in an objectionable exercise feel to the user. The undesired forces also can result in the generation of objectionable acoustic noise, for example inducing vibrations in the lightly damped, mechanically stiff frame of exercise equipment that resonate at frequencies in the audible range. One example of a source of undesired ripple force is cogging torque in an electrical generator. 
         [0005]    Prior art methods have disclosed energy harvesters that have rigid or semi-rigid mechanical coupling directly to an existing pulley or moving member of the exercise equipment, other than the weight stack. These prior-art arrangements generally require significant modification to the standard exercise equipment design in order to realize proper mechanical attachment of the generator, sensors, or other electronic devices. The modifications required for one equipment type, (e.g., a biceps machine), may generally not be compatible with the other types. 
         [0006]    Another drawback of prior art methods, especially methods that rely on engagement or attachment to existing equipment pulleys, is that they are not well-suited to strength equipment that incorporates independent motion arrangements (e.g., left and right bodily motion arrangements) with a common weight stack. This type of strength equipment has become popular in the market due to its ability to emulate a “free weight” user experience. For this type of equipment, methods disclosed in the prior art generally require the use of two energy harvesters to guarantee functional operation when a user chooses to utilize only a portion (e.g., left or right side) of the motion arrangement. 
         [0007]    Generally, the prior art methods are mechanically coupled to a rotating pulley that also provides a function to guide the main cable (or belt) of the strength equipment. In this arrangement, the energy harvester must apply torque to the pulley. To function properly, the torque applied to the pulley by the energy harvester must be limited to avoid slip between the pulley and the main cable, i.e., the torque applied by the energy harvester must be less than the torque capacity due to friction between the main cable and the pulley. When a user selects a relatively low weight, for example 10 pounds, the friction force capacity between the main belt and pulley is generally insufficient to support the function of the energy harvester to produce power from the exercise motion. 
         [0008]    Further, as safety is usually a critical issue, prior systems and methods fail to address adequately a failure in the generator or electronics of an energy harvester. Such conditions may result in substantial torque applied to the generator shaft of the energy harvester, the torque is subsequently converted to a proportional force applied to the weight stack of the exercise equipment. Generally, the resulting force associated with a failure condition can be large and sudden and therefore harmful to a user that has a grip and is engaged in an exercise motion. For applications where the user has an exercise objective of rehabilitation or therapy, the occurrence of a large weight stack force is especially unacceptable. 
       SUMMARY OF THE INVENTION 
       [0009]    An embodiment of a system according to the present invention includes an electrical generator (e.g. an alternating current or direct current generator) coupled to an exercise device. The exercise device is preferably of the type having a mechanical element forming a majority of resistive force to be overcome by an exercise motion of a user of the device. Such mechanical element may be a weight plate or a bendable rod for example. The electrical generator includes a rotatable shaft, the electrical generator being configured to produce electricity as a result of rotation of the shaft. A flexible cord is preferably coupled between the mechanical element and the electrical generator such that the shaft of the electrical generator is rotated in a first direction during motion of the flexible cord in a first cord direction. The shaft of the electrical generator may additionally be rotated in a second direction during motion of the flexible cord in a second cord direction. 
         [0010]    According to an aspect of an embodiment of a system according to the present invention the mechanical element (e.g., one or more weight plates) may be selectively translatable along a translation path between a first position and a second position. The translation path may be linear and/or curvilinear. 
         [0011]    According to another aspect of an embodiment of a system according to the present invention, a force limiter may be connected to the cord and to the mechanical element (e.g., weight stack), the force limiter configured to decouple the cord from the weight stack if a tension force conducted by the cord exceeds a predetermined force threshold. The force limiter may include, for example, a magnetic release arrangement and/or a mechanical fuse. 
         [0012]    According to a further aspect of an embodiment of a system according to the present invention, the electrical generator may be a part of an energy harvester that has a frame and a reel rotatably supported by the frame, wherein the cord extends about an outer circumference of the reel. The reel my be fixed to a second shaft that is rotatably supported by the frame. The reel may include a housing radially at least partially surrounding an arbor secured to the frame, the reel substantially containing a biasing member anchored to the arbor and the housing. The biasing member may be a spring member, such as a constant (or near-constant) force spring, torsion spring, or other desirable biasing member that may be used to balance cord tension. The energy harvester may include a ballast mass coupled to its frame, the ballast mass may serve no other purpose but to increase the overall mass of the energy harvester. 
         [0013]    According to still another aspect of an embodiment of a system according to the present invention, the electrical generator may be a part of an energy harvester that has a frame and vibration isolation mounts may be coupled to the frame. The vibration isolation mounts may be arranged between the frame and a support surface. The support surface may be attached to the exercise device, or any other surface that may counteract the force of gravity upon the energy harvester. 
         [0014]    According to yet a further aspect of an embodiment of a system according to the present invention, when the exercise device rests upon a floor surface the energy harvester may be positioned between the floor surface and a first height parallel to the floor surface defined by at least one of the plates when the device is not being used, or its at rest position. Alternatively, all of the plates may be positioned between the floor surface and a first height parallel to the floor surface defined by the portion of the frame of the energy harvester closest to the floor surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is an elevation view of an exercise machine including a first embodiment of an energy harvester coupling arrangement according to the present invention. 
           [0016]      FIG. 2  is an elevation view of an embodiment of an energy harvester used in accord with an embodiment of the present invention. 
           [0017]      FIG. 3  depicts the  3 - 3  sectioned view of the energy harvester shown in  FIG. 2 . 
           [0018]      FIG. 4  depicts the  4 - 4  sectioned view of the energy harvester shown in  FIG. 2 . 
           [0019]      FIG. 5  depicts the  5 - 5  sectioned view of the energy harvester shown in  FIG. 3 . 
           [0020]      FIG. 6  is a partial view of  FIG. 1 . 
           [0021]      FIG. 7  is a side view of  FIG. 6 . 
           [0022]      FIG. 8  is a graphical representation of an exemplary force versus displacement characteristic of an embodiment of a vibration isolation mount supporting an energy harvester in a coupling arrangement according to the present invention. 
           [0023]      FIG. 9A  is an elevation view of a first embodiment of a force limiter according to the present invention. 
           [0024]      FIG. 9B  is a graphical representation of the relationship of force conducted to a weight stack by a flexible cord and tension force of the flexible cord during typical operating conditions of a coupling arrangement according to the present invention. 
           [0025]      FIG. 9C  is a graphical representation of the relationship of weight stack force conducted to a weight stack by a flexible cord and tension force of the flexible cord during a condition that causes activation or passive operation of a force limiter in a coupling arrangement according to the present invention. 
           [0026]      FIG. 9D  is an elevation view of a second embodiment of a force limiter according to the present invention. 
           [0027]      FIG. 10  is an elevation view of an alternative embodiment of an energy harvester coupling arrangement according to the present invention. 
           [0028]      FIG. 11A  is a graphical representation of a flexible cord tension force characteristic as a function of weight stack displacement during use of the energy harvester coupling arrangement of  FIG. 1 . 
           [0029]      FIG. 11B  is a graphical representation of a flexible cord tension force characteristic as a function of weight stack displacement during use of the energy harvester coupling arrangement of  FIG. 9 . 
           [0030]      FIG. 11C  is a graphical representation of an exemplary time domain waveform of tension force in a flexible cord during an exercise motion with an operable energy harvester in a coupling arrangement according to the present invention. 
           [0031]      FIG. 12  is a schematic view of an exemplary electrical circuit of an energy harvester system. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0032]    Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
         [0033]    Referring now to the figures,  FIG. 1  depicts an energy harvester  10  mechanically coupled to an exercise equipment machine  60  by a flexible cable, wherein the harvester  10  produces electrical power during an exercise motion performed by a user of the machine  60 . The energy harvester  10  provides electrical power to an electronics unit  70  or other electrical storage element (e.g. capacitor or battery) or load (e.g., light(s), heating elements, battery chargers, etc.), which may be electrically connected to the harvester  10  by an electrical cord  72 . As is generally known, strength training machine  60  may include a weight stack  62  including one or more weight plates  64 , such as steel plates, which are coupled to a user interface such as handles  66 . A user exercise force applied to the handles  66  causes the plates  64  to travel in a generally linear path along one or more guide rods  68 . Though described with respect to a conventional plate/guide rod exercise machine, it is to be understood that embodiments of the present invention may be applied to other strength training apparatus, such as flexible rod systems (e.g., energy harvester coupled to a handle or system cable) or even free weights (e.g., energy harvester coupled to bench press bar). 
         [0034]    Referring also to  FIGS. 2-4 , the energy harvester  10  comprises a frame  12 , to which is coupled a mechanical arrangement including a low speed side  20  and a high speed side  40 . The low speed side  20  is adapted to receive mechanical input from the indicated exercise motion and the high speed side  40  is adapted to generate the indicated electrical power to be delivered to the electronics unit  30  or otherwise stored or utilized. While the monikers “low speed” and “high speed” are used to describe the sides of the harvester  10 , and components thereof, they should impart no limitations on the operation of the system as described. 
         [0035]    The low speed side  20  preferably includes a reel  22  and a low speed pulley  24 , both configured to rotate about a low speed axis  26  which may be defined by a first shaft  28  journaled and supported by a first bearing  30  and a second bearing  32 , which may be supported by the frame  12 . The reel  22  includes a housing  22   a  which is adapted to receive a cable or cord  11  about its circumference. Additionally, the housing  22   a  is preferably supported on the first shaft  28  and rotatable about an arbor  21 , which may be fixedly supported by the frame  12 , and which may lie at least substantially coaxially with the first shaft  28 . The arbor  21  is preferably attached rigidly to the frame member  12  of the energy harvester  10  by an arbor fastener  21   a . The arbor fastener  21   a  includes features (e.g. a hex key concentric with the arbor  21 ) that allow the arbor  21  to be rotated prior to fastening to the frame member  12 . The arbor fastener  21   a  is affixed to the frame member  12 , typically with a plurality of screws. The arbor fastener  21   a  can be rotated by a selected number of turns, or partial turns prior to fastening to the frame member  12 . The adjustment of the arbor fastener  21   a  and arbor  21  enables the cord tension at rest position CT 0  (described hereafter) to be adjusted prior to final assembly. It is preferable that both the housing  22   a  and the low speed pulley  24  be fixed to the first shaft  28 , such that the housing  22   a , the pulley  24 , and the shaft  28  rotate as a singular unit about the low speed axis  26 . Such arrangement allows for mechanical energy transfer to the high speed side  40  during bidirectional rotation of the low speed pulley  24 . Alternatively, the housing  22   a  may be clutched so as to rotate with the pulley  24  and shaft  28  in one direction and rotate only about the arbor  21  and directionally opposite the direction of rotation of the pulley  24  and shaft  28 . With reference also to  FIG. 5 , contained substantially within the housing  22   a  is a biasing member  23 , such as a constant force spring  25 , a spiral torsion spring (also referred to as a clock spring or power spring) (not shown), or a torsion spring (not shown). A first end  25   a  of the spring  25  may be fixed to the arbor  21  and a second end  25   b  of the spring  25  may be fixed to the housing  22   a . The biasing member  23  generally maintains the housing  22   a  biased in a first rotational direction  13 . Tensile force applied to the cable  11  will overcome the bias provided by the biasing member  23  and will rotate the housing in a second rotational direction  15 . 
         [0036]    The flexible cord  11  is attached to the resistive element, such as at least one member of the weight stack  62 , by a cord mounting bracket  110  that may be fastened to the top weight plate  64   a  or another member of the weight stack  62 . The cord  11  may comprise of a variety of commercially available apparatus for transmitting force between a rotating reel or bobbin and a translating object; these apparatus include but not limited to cords, cables, belts, ribbons, and strings constructed of a variety materials. The cord  11  preferably has a length that exceeds the full potential displacement, or full excursion, of the weight stack  62  along the guide rods  68 . 
         [0037]    The high speed side  40  of the harvester  10  preferably includes a high speed pulley  42  and an electrical generator  50 . The electrical generator  50  (which may be an alternating current generator or a direct current generator) includes a rotor  52  fixed to a second shaft  44 . The high speed pulley  42  and the rotor  52  are configured to rotate about a high speed axis  45  which may be defined by the second shaft  44 , which is preferably journaled and supported by a third bearing  46  and a fourth bearing  48 . It is preferable that both the high speed pulley  42  and the rotor  52  be fixed to the second shaft  44 , such that the pulley  42 , rotor  52 , and the shaft  44  rotate as a singular unit about the high speed axis  45 . Accordingly, the generator  50  is configured to generate electricity upon rotation of the second shaft  44  in either or both rotational directions, which may ultimately be caused by rotation of the housing  22   a  in either direction  13  or  15 . 
         [0038]    The low speed side  20  is mechanically coupled to the high speed sided  40  by a drive member  90 , such as a belt  92 . The belt  92  extends about and is frictionally engaged with the low speed pulley  24  and the high speed pulley  42 . The engagement of the belt  92  with the pulleys  24 , 42  may be enhanced by texturing the belt  92  and/or one or more of the pulleys  24 , 42 . Further enhancement of the engagement may be provided by using toothed pulleys and a notched belt. 
         [0039]    Referring more particularly to  FIGS. 6 and 7 , the energy harvester  10  may be supported by a plurality of vibration isolation mounts  80 , the vibration isolation mounts  80  may fastened or otherwise supported on a base side  81  to an isolation frame  82  or portion of the exercise equipment  60  and fastened on a harvester side  83  to the energy harvester frame  12 . An energy harvester  10  having a known mass, m h , may be supported by the plurality of vibration isolation mounts  80 , the vibration isolation mounts  80  having a mechanical degree of freedom to deflect in the vertical direction, and having a more limited mechanical freedom to deflect in a direction orthogonal to the vertical direction. Each vibration isolation mount  80  preferably has a stiffness characteristic, defined by a deflection of the mount  80  in response to an axially applied force, (i.e., a force applied vertically relative to the mounting orientation shown in  FIG. 7 ). Generally, during an exercise motion, the operation of the energy harvester  10  creates a combination of forces that are supported by the vibration isolation mounts  80 . A first type of force arises in response to the desired power producing function, and is generally characterized by a low frequency characteristic related to the exercise motion, the exercise motion frequencies generally occurring below 5 Hz. A second type of force refers to undesired forces, for example, forces that arise due to magnetic cogging forces within the generator  50 ; these undesired forces are generally characterized by the presence of higher frequency spectral content, substantially above the mechanical frequencies that arise directly in response to an exercise motion. The plurality of the vibration isolation mounts  80  has a combined stiffness characteristic or stiffness constant, K s , that relates vertical force and vertical deflection, generally the combined characteristic having a stiffness greater than that of a single vibration isolation mount  80 . The vibration isolation mount combined stiffness, K s , and the suspended mass of the energy harvester, m h , create a vibration isolation characteristic that is suitable to substantially attenuate the amplitude of undesired, higher frequency forces that are transmitted, mechanically, into the frame of the exercise equipment  60  through the vibration isolation mounts  80 . A preferred combined stiffness, Ks, may be on the order of about 15 to about 150 N/mm, with about 25 to about 60 N/mm being more preferred. In one embodiment of the present invention each vibration isolation mount  80  is comprised substantially of rubber with mounting features inserted, for example a threaded nut insert, to facilitate fastening one surface of the vibration isolation mount  80  to the exercise machine  60  and the opposite surface to the energy harvester  10 . A preferred force/deflection curve for each mount  80  is shown in  FIG. 8 . Those who are skilled in the art will recognize that there are a variety of vibration isolation apparatus that are well known, as well as a variety of methods for applying said vibration isolation mounts; it is understood that these apparatus and methods can be applied without departing for the scope and intent of the present invention. Examples include and are not limited to the use of helical springs, dampers, isolation pads, and isolation mounts constructed of rubber (e.g., urethane and/or silicone), foam, and other materials. 
         [0040]    Vibratory effects may be further reduced by alternatively or additionally utilizing a ballast. In one embodiment of the present invention, a ballast mass m b  may be used to provide an increase of the total suspended mass of the energy harvester, m h . One function of the ballast mass m b  is to increase attenuation of high frequency forces that are transmitted into the frame of the exercise equipment  60  through the vibration isolation mounts  80 , and also to increase attenuation of high frequency forces into the weight stack  62  of the exercise equipment  60  through the flexible cord  11 . Generally, the static and low frequency tension forces developed in the flexible cord  11  produce equal and opposite forces that are transmitted through the vibration mounts  80  to the exercise equipment  60  or other support surface. The ballast mass m b  is also selected to compensate for these static and low frequency tension forces to ensure sufficient compression loading of the vibration isolation mounts  80  during energy harvester operation, since certain types of vibration isolation mounts only function properly when a minimum compression force is maintained in the primary desired axis of isolation (the vertical axis according to  FIG. 7 ). In one embodiment of the present invention, the ballast mass m b  comprises a material with high density and low cost, such as carbon steel. It is understood that the ballast mass m b  generally provides the function to increase the suspended mass of the energy harvester and can comprise a variety of materials without departing from the scope and intent of the present invention. In a preferred embodiment, the total mass of the energy harvester m h  (which may include the ballast mass m b ) is substantially equal to the static tension force in the flexible cord  11 . 
         [0041]    It may be desirable to incorporate a safety feature into an energy harvester coupling arrangement according to the present invention.  FIG. 9A  shows a force limiter  100  that may be preferably disposed in an inline, series connection between the flexible cord  11  and the resistive element (e.g., at least one member of the weight stack  62 ), such as the top plate  64   a . During typical operation of the exercise equipment  60 , the energy harvester  10  operates to produce electrical power, and the force limiter  100  conducts the net tension force developed by the combination of the energy harvester operation and the force developed by the biasing member  23  of the mechanical reel  22 . Referring to  FIG. 9B , for a range of expected operation of the exercise equipment  60 , the tension in the flexible cord  11  remains within a region, or a typical operating range, between CT 0  and CT 1 , that does not cause the force limiter  100  to operate or react. Referring now to  FIG. 9C , the force limiter  100  has a characteristic that disconnects the mechanical connection between the flexible cord  100  and the weight stack  62  when the tension force transmitted through the force limiter  100  exceeds a limit threshold CT max ; the result after the limiter  100  reacts to an excess force, is that zero force is conducted to the weight stack by the flexible cord  11 . An increased tension force in the flexible cord  11  can occur when an unexpected failure occurs within the energy harvester  10 , for example, due to a seized bearing. The limit threshold CT max  is preferably above the maximum force in the flexible cord  11  that occurs during expected operation of the exercise equipment  60 , including aggressive exercise motions. In one embodiment of the present invention, referring more particularly to  FIG. 9A , the force limiter  100  comprises a support member  110 , a magnet  120 , and a magnetic material  130  (e.g., ferrous member or another magnet). An aglet  132  or other connector may establish a mechanical connection between the magnetic material  130  and the flexible cord  11 . Those who are skilled in the art will recognize that a force limiter that substantially exhibits the characteristic shown in the graph in  FIG. 9C , can be accomplished by several known methods and still remain within the scope and intent of the present invention. Known methods include and are not limited to mechanical fuses, wire rope fuses, hook-and-loop materials (e.g., Velcro®), adhesives, as well as tension limiters or clutches similar to apparatus used in automotive seat belts. For example,  FIG. 9D  shows a second embodiment  200  of a force limiter according to the present invention. This embodiment  200  is a mechanical fuse coupled between the cord  11  and the top weight stack plate  64 . The fuse includes a first anchor  220  and a second anchor  230  connected by a fuse element  240 , which is adapted to break when the tension force meets or exceeds the limit threshold CT max . 
         [0042]    In an alternative embodiment of the present invention, referring to  FIG. 10 , the energy harvester  10  may be mounted in a position that is vertically above the range of motion of the weight stack  62 . In the embodiment shown in  FIG. 10 , the tension profile shown in  11 B applies when the energy harvester is not in operation. The flexible cord  11  also remains in tension during operation of the energy harvester  10 . The other aspects of the invention are similar to those described herein. 
         [0043]    Referring to  FIG. 11A , the power spring  23  within the mechanical reel  22  produces a characteristic of tension in the flexible cord  11 , as a function of the vertical displacement of the top weight plate  64   a , this vertical displacement is referred to as weight stack displacement in  FIG. 11A . The weight stack rest position WS 0  corresponds to the location of the weight stack  62  when all members of the weight stack  62  are at rest and the machine  60  is not in use. The tension force in the flexible cord  11  remains preferably substantially constant as a function of the weight stack displacement; that is, the tension force in the flexible cord  11  when some or all of the weight stack  62  is at an elevated weight stack position WS 1  (i.e., when at least one weight stack plate  64  is lifted) is substantially similar to the tension force in the flexible cord  11  when the weight stack  62  is in the weight stack rest position WS 0 . The described characteristic of the tension force as a function of weight stack displacement is sometimes referred to as a near-constant force characteristic. The characteristic depicted in the graph of  FIG. 11A  applies for the case of an exercise motion without energy harvester operation, i.e., for the condition where no electrical power is produced by the energy harvester  10  in response to a motion of the weight stack  62 . Referring now to  FIG. 11C , the tension force in the flexible cord  11  due to the energy harvester operation and the near-constant force of the mechanical reel  22  are shown in an exemplary time domain waveform. 
         [0044]    Referring to  FIG. 12 , a schematic is provided of an exemplary electrical circuit  300 , including the energy harvester generator  40 . The electrical circuit  300  may be completed with an electronics load  302 . Generally, the electrical circuit  300  comprises the electrical generator  40  (such as that of the harvester  10 ) connected to a AC-to-DC converter or inverter  310 , control electronics  320 , a DC Link  330  comprising a Bulk Capacitor  332 , a positive DC link terminal  334 , and a negative DC link terminal  336 , and the electronics load  302 , the electronics load  302  being electrically connected to the DC link  330 . The electronics load  302  generally preferably comprises a DC-DC converter to convert the DC link voltage to a supply voltage appropriate for the electronics used in the electronics load  302 , for example 12, 5, or 3.3 volts DC may be preferred. The load  302  may further include a battery or capacitor for supplemental energy storage for electrical energy to be used by the electronics load  302  for some period of time after an exercise motion is completed. The electronics load  302  preferably performs a function to enhance or assist the user of the exercise equipment, for example, providing a display of workout metrics such as repetitions, range of motion, and work effort; other examples of electronics load functions include providing wireless communications to a mobile device of a user of the exercise equipment or to a wireless router or device located in a fitness facility.  FIG. 12  is provided for exemplary purposes only, and it is understood that various arrangements of electrical circuits for the energy harvester electronics may be used without departing from the scope and intent of the present invention. 
         [0045]    Those who are skilled in the art will recognize that the energy harvester in this invention is one embodiment, and is used as an exemplary apparatus to show the benefits of the present invention, in particular, the use of a mechanical reel  22  comprising a flexible cord  11  fastened to the weight stack  62 , and the rotating member  22   a  of the mechanical reel  22  coupled to the rotating member  44  of an electrical generator  50 . Other embodiments of energy harvesters exist that fall within the scope and intent of the present invention. In particular, numerous arrangements of an electrical generator  50  that result in rotation of the generator shaft  44  in response to the motion of the mechanical reel  22  fall within the scope of the present invention. As an additional example, the second low speed bearing  32  may be omitted and the housing  22   a  rotating on the arbor  21  may provide the function of the second low speed bearing  32 . Additionally or alternatively, an embodiment of the present invention may include an energy harvester  10  mounted to a surface that is not part of the exercise equipment  60 , such as a building surface (e.g., wall or floor), a compliant floor mat in an exercise facility, or may be weighted down with sufficient ballast and simply rested on a floor surface. 
         [0046]    The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.