Systems and methods for determining selected exercise resistance

Abstract

A system and method for determining a selected weight in exercise equipment (which may include an incremental weight sensor disposed on a shaft rotatably fastened with an incremental weight selection dial). The weight stack incremental sensor produces an electrical signal related to the dial position. A spring element or plurality of spring elements are disposed between a reference member and an unused portion of a weight stack results in spring displacement during an exercise motion. A weight stack sensor disposed between the reference member and the unused portion of a weight stack produces an electrical signal related to displacement. The sensor electrical signals can be used by an electronics unit to compute the total weight lifted by a user of exercise equipment.

I claim: 
     
         1 . An apparatus comprising:
 a plurality of weight plates including a bottom weight plate, the weight plates being at least partially selectively vertically translatable along a translation path from an at-rest position; and   a sensor configured to measure a displacement of the bottom weight plate from the at-rest position.   
     
     
         2 . An apparatus according to  claim 1 , wherein the sensor comprises a stationary component and a moveable component, wherein the displacement of the bottom weight plate is automatically measured by sensing two positions of the moveable component with respect to the stationary component. 
     
     
         3 . An apparatus according to  claim 2 , the sensor further comprising a biasing member to bias the moveable component in a first direction into contact with the bottom weight plate. 
     
     
         4 . An apparatus according to  claim 3 , wherein the biasing member is a biasing spring having a predetermined bias spring constant. 
     
     
         5 . An apparatus according to  claim 4 , wherein when the weight plates are positioned at the at-rest position, the bottom weight plate is at least partially supported by a plurality of weight stack springs, each weight stack spring having a spring constant that is at least substantially greater than the spring constant of the biasing spring. 
     
     
         6 . An apparatus according to  claim 5 , wherein the moveable component makes physical contact with the stationary component. 
     
     
         7 . An apparatus according to  claim 6 , wherein the sensor comprises a slide potentiometer. 
     
     
         8 . An apparatus according to  claim 7 , wherein the slide potentiometer comprises a wiper lever biased by a wiper bias force in a second direction opposite the first direction, the wiper bias force being substantially less than the predetermined bias spring constant. 
     
     
         9 . An apparatus according to  claim 5 , wherein the moveable component is spaced from the stationary component. 
     
     
         10 . An apparatus according to  claim 9 , wherein the sensor comprises a linear magnetic encoder. 
     
     
         11 . An apparatus according to  claim 9 , wherein the sensor comprises a linear optical encoder. 
     
     
         12 . An apparatus according to  claim 9 , wherein the sensor comprises a capacitive encoder. 
     
     
         13 . An apparatus according to  claim 2 , further comprising an electronics unit electrically coupled to the sensor, the sensor providing a sense signal to the electronics unit for signal processing. 
     
     
         14 . An apparatus according to  claim 13 , wherein the sense signal comprises an analog signal. 
     
     
         15 . An apparatus according to  claim 13 , wherein the sense signal comprises a digital signal. 
     
     
         16 . An apparatus comprising:
 a plurality of weight plates including a bottom weight plate, the weight plates being at least partially selectively vertically translatable along a translation path from an at-rest position;   a plurality of selectable incremental weights, each weighing less than each weight plate; and   a first sensor configured to sense a selection of the incremental weights.   
     
     
         17 . An apparatus according to  claim 16 , wherein the selection was made using a dial fixed to a shaft. 
     
     
         18 . An apparatus according to  claim 17 , wherein the first sensor is configured to sense a rotational position of the shaft. 
     
     
         19 . An apparatus according to  claim 18 , further comprising:
 a second sensor configured to measure a displacement of the bottom weight plate from the at-rest position.   
     
     
         20 . An apparatus according to  claim 19 , further comprising an electronics unit electrically coupled to the first sensor and the second sensor. 
     
     
         21 . An apparatus according to  claim 20 , wherein the electronics unit is configured to:
 receive a first sense signal from the first sensor;   determine a first amount of selected incremental weight based on the first sense signal;   receive a second sense signal from the second sensor; and   determine an amount of force removed from the bottom plate based on the second sense signal.   
     
     
         22 . An apparatus according to  claim 21 , wherein the electronics unit is further configured to calculate a total lifted weight as the sum of the first amount of selected incremental weight and the amount of force. 
     
     
         23 . An apparatus according to  claim 22 , wherein the electronics unit is further configured to display at least one of the first amount of selected incremental weight, the amount of force, and the total lifted weight. 
     
     
         24 . An apparatus according to  claim 21 , wherein the electronics unit is further configured to:
 start a timer at a start time upon detection of a first change in the second sense signal;   stop the timer at a stop time upon detection of a second change in the second sense signal; and   calculate an exercise duration by subtracting the start time from the stop time.   
     
     
         25 . An apparatus according to  claim 16 , wherein the translation path is at least partially defined by one or more longitudinal guide rods extending through the plurality of weight plates, the apparatus further comprising an electronics unit electrically connected to the first sensor through an electrically conductive path comprising at least a portion of the guide rods. 
     
     
         26 . A method comprising the step of:
 conducting electricity along a conductor, the conductor comprising a portion of a first guide rod, wherein the guide rod comprises a longitudinal rod on an exercise machine, the rod extending through a plurality of weight plates, the weight plates being at least partially selectively translatable along a translation path from an at-rest position.   
     
     
         27 . A method according to  claim 26 , further comprising the step of sensing a first voltage across a first resistor in electrical communication with the conductor, the second voltage being caused by the conducting step. 
     
     
         28 . A method according to  claim 27 , further comprising the step of sensing a second voltage across a second resistor in electrical communication with the conductor at a different time than the first resistor, the second voltage being caused by the conducting step. 
     
     
         29 . A method according to  claim 28 , wherein the exercise machine further comprises a plurality of selectable incremental weights, each weighing less than each weight plate, and further wherein the first voltage corresponds to a first selection of the incremental weights and the second voltage corresponds to a second selection of the incremental weights.