PATENT DOCUMENT

Publication Number: US-10551798-B1
Application Number: US-201715597145-A
Country: US
Kind Code: B1

Title: Rotatable crown for an electronic device

Abstract:
A compact crown for an electronic device such as an electronic watch, including a set of wipers capable of determining a rotation angle, rotation direction, or rotation speed, is disclosed. The set of wipers is in contact with at least one resistance member at different angular positions around a rotation axis. The crown may have a group of ground taps disposed along the resistance member and a measured signal may vary based on the position of each wiper as it contacts the at least one resistance member. A compact crown may also include capacitive members and capacitive sensors in order to similarly determine rotation angle, rotation direction, or rotation speed.

Claims:
What is claimed is: 
     
       1. An electronic watch, comprising:
 a housing; 
 a crown at least partially positioned within the housing and configured to receive rotational and translational input, and comprising:
 a shaft; 
 a resistance member; and 
 a set of wipers affixed to the shaft and operative to travel along the resistance member during rotation of the shaft, the set of wipers providing an output based on multiple contact points between the set of wipers and the resistance member; 
 
 a display positioned at least partially within the housing and configured to depict a graphic in response to at least one of the rotational input or the translational input; 
 an analog-to-digital converter electrically connected to the set of wipers, the analog-to-digital converter configured to provide a digital output corresponding to the output; and 
 a processor configured to determine an angular position, a direction of rotation, or a speed of rotation of the shaft using the digital output, and to manipulate the graphic in response to the determined angular position, the direction of rotation, or the speed of rotation; wherein 
 each wiper divides a resistance of the resistance member at each contact point, and a voltage at each contact point of the multiple contact points varies in response to rotation of the shaft. 
 
     
     
       2. The electronic watch of  claim 1 , wherein:
 the resistance member is circular; 
 the resistance member has a constant resistance along its circumference; and 
 the set of wipers maintains constant contact with the resistance member. 
 
     
     
       3. The electronic watch of  claim 1 , wherein:
 the resistance member comprises a first segment and a second segment separated by a ground tap; 
 the set of wipers comprises a first wiper and a second wiper; and 
 during rotation of the shaft, the first wiper divides the first segment at a first contact point of the multiple contact points while the second wiper divides the second segment at a second contact point. 
 
     
     
       4. The electronic watch of  claim 3 , wherein a first resistance of the first segment is equal to a second resistance of the second segment. 
     
     
       5. The electronic watch of  claim 3 , wherein:
 the first segment has a constant resistance; and 
 the first contact point defines, in the first segment, two portions having a cumulative resistance equal to the constant resistance of the first segment. 
 
     
     
       6. The electronic watch of  claim 5 , wherein a resistance of each of the two portions varies in response to rotation of the shaft while maintaining the cumulative resistance equal to the constant resistance of the first segment. 
     
     
       7. The electronic watch of  claim 5 , wherein the first wiper and the second wiper maintain electrical contact with the resistance member during rotation of the shaft. 
     
     
       8. The electronic watch of  claim 1 , wherein:
 the resistance member comprises a first resistive track and a second resistive track; 
 the electronic watch further comprises a switch configured to electrically activate the first resistive track while electrically floating the second resistive track, and to electrically activate the second resistive track while electrically floating the first resistive track; 
 the set of wipers comprises a first wiper that travels along the first resistive track and a second wiper that travels along the second resistive track; 
 the first wiper is electrically connected to the second wiper; and 
 the output comprises a first output associated with the first wiper and a second output associated with the second wiper. 
 
     
     
       9. The electronic watch of  claim 1 , wherein:
 the resistance member comprises a resistive track; 
 the set of wipers comprises a first wiper that travels along the resistive track and a second wiper that travels along the resistive track; 
 the first wiper is electrically isolated from the second wiper; and 
 the output comprises a first output associated with the first wiper and a second output associated with the second wiper. 
 
     
     
       10. The electronic watch of  claim 9 , further comprising:
 a first conductive output track; 
 a second conductive output track; 
 a third wiper affixed to the shaft and electrically connected to the first wiper, and operative to travel along the first conductive output track during rotation of the shaft; and 
 a fourth wiper affixed to the shaft and electrically connected to the second wiper, and operative to travel along the second conductive output track during rotation of the shaft. 
 
     
     
       11. The electronic watch of  claim 1 , wherein:
 the resistance member comprises a resistive track; 
 the set of wipers comprises a first wiper that travels along the resistive track and a second wiper that travels along the resistive track; 
 the first wiper is electrically connected to the second wiper; and 
 the output comprises an output associated with both the first wiper and the second wiper. 
 
     
     
       12. The electronic watch of  claim 11 , further comprising:
 a voltage input; 
 a resistor; 
 a constant current regulation circuit; and 
 a reference voltage output, wherein 
 the resistive track is coupled between the reference voltage output and the constant current regulation circuit; and 
 the voltage input is coupled to the reference voltage output via the resistor. 
 
     
     
       13. A crown for an electronic watch, comprising:
 a resistance member on a contact surface; 
 a rotatable shaft; 
 an array of ground taps separating the resistance member into segments of uniform resistivity; 
 a first wiper and a second wiper affixed to the rotatable shaft, the first wiper configured to generate a first output based on a relative position of the first wiper with respect to the resistance member and the second wiper configured to generate a second output based on a relative position of the second wiper with respect to the resistance member; and 
 a processor configured to determine at least one of an angular position, a direction of rotation, or a speed of rotation of the rotatable shaft based on the first output and the second output, wherein: 
 the crown is configured to receive a rotational input and a translational input; and 
 the first wiper and the second wiper are affixed to the rotatable shaft such that the first wiper contacts the resistance member at a first segment that is distinct from a second segment contacted by the second wiper. 
 
     
     
       14. The crown of  claim 13 , wherein:
 a display is configured to depict a graphic in response to at least one of the rotational or translational input; and 
 the processor is configured to manipulate the graphic in response to the determined angular position, direction of rotation, or speed of rotation. 
 
     
     
       15. The crown of  claim 13 , wherein the array of ground taps is positioned on the resistance member such that the segments have a substantially similar size. 
     
     
       16. The crown of  claim 13 , wherein the resistance member comprises a first resistive track and a second resistive track, the crown further comprising:
 an array of voltage inputs connected to the resistance member, the array of voltage inputs including a voltage input positioned between each set of adjacent ground taps along the resistance member; and 
 a switch connected to at least the array of voltage inputs and configured to electrically activate the first resistive track while electrically floating the second resistive track, and to electrically activate the second resistive track while electrically floating the first resistive track, wherein 
 the first wiper is electrically connected to the second wiper. 
 
     
     
       17. The crown of  claim 13 , further comprising:
 a dome switch, wherein 
 the rotatable shaft is translatable and has a first end configured to depress and activate the dome switch in response to translation of the rotatable shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a nonprovisional patent application of and claims the benefit of U.S. Provisional Patent Application No. 62/337,804, filed May 17, 2016 and titled “Compact Rotary Encoder,” the disclosure of which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD 
     The described embodiments relate generally to compact crowns for electronic devices such as electronic watches. More particularly, the present embodiments relate to a crown having (or taking the form of) a high-resolution rotary encoder that detects a rotation angle or relative amount of motion using an output from two or more angularly offset wipers. 
     BACKGROUND 
     In computing systems, a rotary encoder may be employed to detect an angular position or motion of a shaft. Many traditional rotary encoders use optical sensing of indicia placed around a circumference of an encoder surface or wheel. The precision of such rotary encoders is therefore limited by the minimum achievable size and spacing of the indicia. Optical sensing of indicia may also limit the ability of a traditional rotary encoder to detect a direction of rotation of a rotatable shaft of the encoder. 
     SUMMARY 
     Embodiments of the present invention are directed to a crown for an electronic device, which crown may be configured to determine an angular position, direction of rotation, or speed of rotation of a user-rotatable shaft or other user-rotatable element, for example, to control a function of the electronic device. The controlled function may include, for example, a graphical output of a display on the electronic device or a volume of an audio output of the electronic device. 
     In a first aspect, the present disclosure describes an electronic watch. The electronic watch includes a housing; a crown at least partially positioned within the housing and configured to receive rotational and translational input from a user, and comprising: a shaft; a resistance member; and a set of wipers affixed to the shaft and operative to travel along the resistance member during rotation of the shaft, the set of wipers providing an output based on multiple contact points between the set of wipers and the resistance member; a display positioned at least partially within the housing and configured to depict a graphic in response to at least one of the rotational or translational input; an analog-to-digital converter electrically connected to the set of wipers, the analog-to-digital converter configured to provide a digital output corresponding to the output; and a processor configured to determine an angular position, direction of rotation, or speed of rotation of the shaft using the digital output, and to manipulate the graphic in response to the determined angular position, direction of rotation, or speed of rotation; wherein each wiper divides a resistance of the resistance member at each contact point, and a voltage at each contact point of the multiple contact points varies in response to rotation of the shaft. 
     Another aspect of the present disclosure may take the form of a method for controlling an electronic watch, comprising: receiving an output signal from a crown of the electronic watch; identifying, based on the output signal, a first angle of rotation of a first wiper of the crown about an axis of a shaft of the crown, the first wiper in contact with a resistive track or a conductive output track of the crown; identifying, based on the output signal, a second angle of rotation of a second wiper of the crown about an axis of the shaft of the crown, the second wiper in contact with the resistive track; and controlling a function of the electronic watch based on at least one of the first and second angles of rotation. 
     Still another aspect of the disclosure may take the form of a crown for an electronic watch, comprising: a resistance member on a contact surface; a user-rotatable shaft; an array of ground taps separating the resistance member into segments of uniform resistivity; a first wiper and a second wiper affixed to the user-rotatable shaft, the first wiper configured to generate a first output and the second wiper configured to generate a second output based on a relative position of the first wiper or the second wiper with respect to the resistance member; and a processor configured to determine at least one of an angular position, a direction of rotation, or a speed of rotation of the user-rotatable shaft based on the first output and the second output, wherein the first wiper and the second wiper are affixed to the user-rotatable shaft such that the first wiper contacts the resistance member at a first segment that is distinct from a second segment contacted by the second wiper. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  shows a sample electronic device that may incorporate a rotary encoder in the form of a crown, as described herein; 
         FIG. 2  shows an electrical block diagram of the electronic device of  FIG. 1 ; 
         FIG. 3  shows a sample rotary encoder according to one example embodiment; 
         FIG. 4  shows a simplified electrical diagram of the rotary encoder of  FIG. 3 ; 
         FIGS. 5A-5B  show sample circuit diagrams formed by the rotary encoder of  FIG. 3 ; 
         FIGS. 6A-6B  show sample voltage vs. position graphs of the rotary encoder of  FIG. 3 ; 
         FIG. 7  shows a simplified electrical diagram of a rotary encoder according to another example; 
         FIGS. 8A-8B  show sample voltage vs. position graphs of the rotary encoder of  FIG. 7 ; 
         FIGS. 9A-9B  show a simplified electrical diagram of a rotary encoder according to another example; 
         FIG. 10  shows a sample circuit diagram formed by the rotary encoder of  FIG. 9 ; 
         FIG. 11  shows a sample voltage vs. position graph of the rotary encoder of  FIG. 9 ; 
         FIG. 12  shows a timing diagram for the rotary encoder of  FIG. 9 ; 
         FIG. 13  shows a simplified electrical diagram of a rotary encoder according to another example; 
         FIG. 14  shows a sample circuit diagram formed by the rotary encoder of  FIG. 13 ; 
         FIG. 15  shows a simplified electrical diagram of a rotary encoder according to another example; 
         FIG. 16  shows a sample circuit diagram formed by the rotary encoder of  FIG. 15 ; 
         FIG. 17  shows a sample voltage vs. position graph of the rotary encoder of  FIG. 15 ; 
         FIG. 18  shows another example of a rotary encoder; 
         FIG. 19  shows a top view of a portion of the rotary encoder of  FIG. 18 ; 
         FIGS. 20A-20B  show sample capacitance vs. position graphs of the rotary encoder of  FIG. 18 ; and 
         FIG. 21  illustrates a method that may be performed to control a function of an electronic device based on an angle of rotation of a wiper of a rotary encoder about an axis of a rotatable element of the rotary encoder. 
         FIG. 22A  illustrates a list, displayed on an electronic device, that may be controlled by rotation of a crown. 
         FIG. 22B  illustrates the list of  FIG. 22A , changed in response to rotation of the crown. 
         FIG. 23A  illustrates an electronic device displaying a picture, the magnification of which may be controlled by rotation of a crown. 
         FIG. 23B  illustrates the picture of  FIG. 23A , changed in response to rotation of the crown. 
         FIG. 24A  illustrates an electronic device displaying a question that may be answered by rotating a crown. 
         FIG. 24B  illustrates the electronic device of  FIG. 23A , with the question answered through rotation of the crown. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The following disclosure relates to a compact rotary encoder capable of high resolution output for use in an electronic device such as an electronic watch. More particularly, the rotary encoder may be used as, or connected to, a crown of an electronic watch. The crown may function as an input device of the electronic device, and may be selectively rotated about an axis. The relative rotation around the axis may be used to control a feature, interface, or other mechanism of the electronic device. The high resolution of the rotary encoder, functioning as a crown (or as part of a crown), may allow for precise control of an electronic device. In some examples, the rotary encoder may control or vary any or all of: a graphic shown on a display on the electronic device; a function of the electronic device; a haptic output of the electronic device; and/or a volume of an audio output of the electronic device. 
     In an embodiment, the crown (e.g., rotary encoder) may have a user-rotatable shaft, at least two arms extending radially from the shaft and separated by an angle, and a wiper or slider coupled to each arm. Each wiper may extend from the arm at an angle and contact at least one resistance member on a contact surface of a rotary encoder base. In some embodiments, the arms may extend at a non-right angle from the shaft. In some examples, the arms may be replaced by one or more rotors, or by a portion of the shaft that extends outward from an axis of the crown, which portion provides or supports the wipers, sliders, or other electrical contact members. The contact surface may also have a group of ground taps electrically coupled to the resistance member and at least one conductive element disposed radially around the shaft. In some embodiments, the resistance member may form a circle, track, path, or the like. Further, the resistance member may be divided into multiple segments. 
     As the shaft is rotated about its axis (e.g., by a user), each wiper contacts a different portion of the resistance member and experiences a variable resistance as a result of the wiper “dividing” a portion of the resistance member between ground points into at least two segments. That is, as the shaft rotates, the wiper varies the length of segments of the resistance member between the wiper contact point and grounded points disposed around the resistance member. The output signals for each wiper may be detected and monitored by a processor to determine a rotation angle (i.e., angle of rotation or angular position), rotation direction (i.e., direction of rotation), or rotation speed (i.e., speed of rotation) around the shaft axis. 
     In some embodiments, the at least two arms (or the at least two contact members that are otherwise affixed to the shaft) are separated by an angle. This may cause each respective wiper to contact the resistance member at points at which the output signals are out of phase. The particular angle of separation for the arms (or contact members) may be chosen such that the output signals from the wipers, when plotted as a function of the rotation angle, are signals in quadrature (e.g., signals separated by a predetermined offset). Accordingly, by determining the phase difference between signals from the respective wipers, a direction of rotation can be determined. 
     In another embodiment, the rotary encoder/crown may have a shaft and at least two capacitive members extending radially from the shaft and separated by an angle. The capacitive members may rotate above the base of the rotary encoder member. The base of the rotary encoder/crown may include a set of capacitance sensors positioned on a sensing surface beneath the shaft. The capacitance sensors may be coaxial with the shaft. The capacitive sensors may detect a capacitance between themselves and the capacitive members. As the shaft rotates, the capacitive members may pass over the capacitive sensors. Capacitance between a capacitive member and a capacitive sensor increases as overlap between the member and sensor increases, and decreases as overlap decreases. The capacitive member may revolve as the shaft rotates, thereby varying the overlap of the capacitive member with respect to the capacitive sensor. As the shaft rotates, this overlap may vary from zero to full, or anywhere in between. 
     The capacitive members and the group of capacitance sensors may be configured to maintain a constant separation during rotation of the capacitive members around the shaft axis. The output signals of the capacitance sensors may be detected and monitored by a processor to determine a rotation angle, rotation direction, or rotation speed of the shaft around the shaft axis. 
     These and other embodiments are discussed below with reference to  FIGS. 1-21 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
     Turning now to the figures,  FIG. 1  illustrates an electronic device  100  such as a wearable electronic device, timekeeping device, portable computing device, mobile phone, touch-sensitive input, or the like. The electronic device  100  may have a housing  102  defining a body, a display  104  configured to depict a graphical output of the electronic device  100 , and at least one input device or selection device  106 . An input device  106  may be positioned at least partially within the housing  102  and may project through the housing so that a user may manipulate the input device (for example, by rotating it). Likewise, the display  104  may be positioned at least partially within the housing  102  and may be accessible by, and visible to, a user. The user may view information presented on the display and may touch the display to provide a touch or force input. As one example, the user may select (or otherwise interact with) a graphic, icon, or the like presented on the display by touching or pressing on the display at the location of the graphic. 
     The electronic device  100  may have a band  108  for securing the electronic device  100  to a user, another electronic device, a retaining mechanism, and so on. In some embodiments, the electronic device  100  may be an electronic watch, the body defined by the housing  102  may be a watch body, and the input device  106  may be a crown of the electronic watch. The crown may extend from an exterior to an interior of the electronic device housing. The crown may be configured to receive rotational and translational input from a user. The input device  106  may include a scroll wheel, knob, dial, or the like that may be operated by a user of the electronic device  100 . Some embodiments of the electronic device  100  may lack the band  108 , display  104 , or both. 
     The electronic device  100  may include a number of internal components.  FIG. 2  illustrates a simplified block diagram  200  of the electronic device  100 . The electronic device  100  may include, by way of non-limiting example, one or more processors  202 , a storage or memory  204 , an input/output interface  206 , a display  210 , a power source  212 , and one or more sensors  208 , each of which will be discussed in turn below. 
     The processor  202  may control operation of the electronic device  100 . The processor  202  may be in communication, either directly or indirectly, with substantially all of the components of the electronic device  100 . For example, one or more system buses  201  or other communication mechanisms may provide communication between the processor  202 , the display  210 , the input/output interface  206 , the sensors  208 , and so on. The processor  202  may be any electronic device capable of processing, receiving, and/or transmitting instructions. For example, the processor  202  may be a microprocessor or a microcomputer. As described herein, the term “processor” is meant to encompass a single processor or processing unit, multiple processors, or multiple processing units, or other suitably configured computing element(s). 
     In some examples, the function(s) of the electronic device  100  controlled by the processor  202  may include a graphical output of a display  210  on the electronic device  100 . For example, in response to detecting rotation of the input device  106  (e.g., a changed angular position, direction of rotation, or speed of rotation of a rotary encoder, which rotary encoder may be a crown or part of a crown), the processor  202  may change or manipulate (e.g., scroll, zoom, pan, move, etc.) a graphic depicted on the display  210 . Scrolling may be within a graphic (e.g., a photo or map), within text and/or images of a document or web page (which are specific examples of graphics), within an array of graphics representing applications or functions that may be selected, launched, and so on. The processor  202  may cause graphics on a display to scroll in a particular direction based on a determined direction of rotation of the input device  106 , or may cause scrolling at a speed based on a determined speed of rotation of the input device  106 .  FIGS. 22A-24B , discussed below, provide examples of how a rotatable input device  106 , such as a crown, may be used to interact with an electronic device and manipulate or change graphics on an associated display. 
     As another example, rotating the input device  106  may cause different graphics, icons, information, or the like to be shown on the display so that a user may select or otherwise interact with such graphics/icons/information (collectively, a “graphic”). The user may interact with a graphic by touching or applying force to a portion of the display  104  depicting the graphic, through rotational input to the input device  106 , through translational input to the input device  106  (e.g., pressing a crown toward the housing of the electronic device), and so on. 
     The processor  202  may also or alternatively adjust a volume of an audio output of the electronic device  100  in response to detecting rotation of the input device  106 . The volume may be adjusted up or down based on a direction of rotation of the input device  106 . The processor  202  may also or alternatively adjust other settings of the electronic device  100  (or settings of applications hosted on or accessed by the electronic device  100 ) in response to detecting rotation of the input device  106  (e.g., the processor  202  may adjust the time displayed by a clock function of the electronic device  100 ). In some examples, the processor  202  may control movement of a character or item within a game based on a detected rotation (change in angular position), direction of rotation, or speed of rotation of the input device  106 . 
     In some examples, the function of the electronic device  100  controlled by the processor  202  may be determined based on a context of the electronic device  100  or processor  202 . For example, the processor  202  may adjust a volume of an audio output of the electronic device  100  when the input device  106  is rotated while an audio player is open or active on the electronic device  100 , or the processor  202  may scroll through graphics representing applications or functions when the input device  106  is rotated while a home screen is displayed on the electronic device  100 . 
     The memory  204  may store electronic data that may be utilized by the electronic device  100 . For example, the memory  204  may store electrical data or content (e.g., audio files, video files, document files, and so on), corresponding to various applications. The memory  204  may be, for example, non-volatile storage, a magnetic storage medium, optical storage medium, magneto-optical storage medium, read only memory, random access memory, erasable programmable memory, or flash memory. 
     The input/output interface  206  may receive data from a user or one or more other electronic devices. Additionally, the input/output interface  206  may facilitate transmission of data to a user or to other electronic devices. For example, in embodiments where the electronic device  100  is an electronic watch, the input/output interface  206  may be used to receive data from a network, other electronic devices, or may be used to send and transmit electronic signals via a wireless or wired connection (Internet, Wi-Fi, Bluetooth, and Ethernet being a few examples). In some embodiments, the input/output interface  206  may support multiple network or communication mechanisms. For example, the input/output interface  206  may pair with another device over a Bluetooth network to transfer signals to the other device, while simultaneously receiving data from a Wi-Fi or other network. The input/output interface  206  may receive input signals from the sensors  208  and the processor  202  may control the input/output interface  206  to output control signals for the electronic device  100 . 
     The power source  212  may be substantially any device capable of providing energy to the electronic device  100 . For example, the power source  212  may be a battery, a connection cable that may be configured to connect the electronic device  100  to another power source such as a wall outlet, or the like. 
     The sensors  208  may include substantially any type of sensor. For example, the electronic device  100  may include one or more audio sensors (e.g., microphones), light sensors (e.g., ambient light sensors), gyroscopes, accelerometers, or the like. The sensors  208  may be used to provide data to the processor  202 , which may be used to enhance or vary functions of the electronic device  100 . In some embodiments, at least one of the sensors  208  may be a rotary encoder associated with the input device  106  of the electronic device  100  (e.g., a rotary encoder used as, or connected to, a crown of an electronic watch). In some embodiments, at least one of the sensors  208  may be a dome switch that may be depressed and activated by user translation of a crown of an electronic watch. 
       FIG. 3  illustrates an embodiment of a compact rotary encoder  300  for use in an electronic device, such as electronic device  100 . In some embodiments, the rotary encoder  300  may function as the input device  106  of the electronic device  100  such that a shaft  306  of the rotary encoder  300  rotates when the input device  106  rotates. As one example, the input device (and thus the shaft and wipers) may rotate about a long axis of the shaft  306 . Such rotation changes the shaft&#39;s angular position. As discussed above, in some embodiments, the input device  106  may be the rotating crown of an electronic watch. Similarly, any user-rotatable element may be used in place of a shaft. As previously mentioned, the rotary encoder  300 , and other rotary encoders discussed herein, may be a crown of an electronic watch, or part of a crown of an electronic watch. Accordingly, discussions herein of rotary encoders should be understood to include crowns (or bezels, or other rotatable elements) of an electronic device, such as a watch, phone, tablet computing device, input mechanism, and so on. 
     The rotary encoder  300  may include a base  302 , cover  304 , and a contact surface  303  on the base  302 . The cover  304  may include an aperture  308  through which a rotating shaft  306  passes, extending into an interior of the rotary encoder  300  (or associated device). It should be appreciated that the rotary encoder  300  may take the form of a crown, button, scroll wheel, or the like for an electronic device, and the cover  304  may be a housing of the electronic device. A user may manipulate a portion of the rotary encoder to cause the shaft  306  to rotate about an axis extending along a length of the shaft, in order to provide an input to the electronic device. 
     In some examples, the shaft  306  may be translatable and slide within the aperture  308 , such that a terminal end or portion of the shaft is configured to depress or otherwise activate a dome switch  322  within the base  302 . Although a dome switch is illustrated, other types of switches may be employed and actuated by translation of the shaft. At least two arms  310   a ,  310   b  may extend outwardly in a radial direction from the shaft  306 . As discussed in more detail with respect to  FIG. 4 , the arms  310   a ,  310   b  may be coupled to the shaft  306  and separated by a radial angle. It will be appreciated that although two arms  310   a ,  310   b  are illustrated, more arms may be coupled to the shaft  306  (or other rotatable element) and separated by other angles. This may improve the resolution or accuracy of the angular position of the shaft detected by the rotary encoder  300 . 
     Each arm  310   a ,  310   b  may include a contact member (e.g., a wiper or slider  312   a ,  312   b , respectively). The wipers  312   a ,  312   b  may extend from the arms  310   a ,  310   b  at an angle such that the wipers  312   a ,  312   b  extend toward, and touch, the contact surface  303  of the base  302 . Each wiper  312   a ,  312   b  may have a known resistance and may electrically couple the arms  310   a ,  310   b  to the contact surface  303  of the rotary encoder  300 . Each wiper  312   a ,  312   b  contacts the contact surface  303  at a unique wiper contact point. In some examples, the arms  310   a ,  310   b  may be provided by one or more rotors, or the arms  310   a ,  310   b  may be replaced by a portion (or portions) of the shaft  306  that extends outward from the axis of the rotary encoder  300 , and the contact members may be formed on or attached to a surface of the shaft  306  that faces the contact surface  303 . It should be appreciated that the contact members/wipers need not be attached to an arm in any embodiment described herein, but instead may be attached to the shaft or to another structure that ultimately is affixed to the shaft. 
     The contact surface  303  of the base  302  may have a resistance member  314 , such as a resistance pad, track, path, or the like provided thereon. In some embodiments, the resistance member  314  may be embedded into or integral with the contact surface  303 , while in other embodiments the resistance member  314  may be adjacent, or deposited or otherwise formed on the contact surface  303 . As shown in  FIG. 3 , the resistance member  314  may be disposed in a ring, circle, or other radial pattern around the rotation axis of the shaft  306 . The resistance member  314  may have a uniform resistivity along its path, circumference, length, or other dimension. The electrical resistance of the resistance member  314  may be determined by dimensions of the member, such as its thickness, length, width, density, or other dimension. In some examples, the resistance member  314  may have constant concentrations of material such as gold, copper, silver, or other metals (including alloys), resistive polymers, ceramics, other suitable material, or a combination thereof to maintain a uniform resistivity. As will be discussed below, the uniform resistivity may be used to determine a position of a wiper  312   a ,  312   b  around the resistance member  314 . A constant current source (such as a current regulation circuit) may supply current to the resistance member  314  in certain embodiments. The current source may provide a relatively fixed or invariant current, and thus may be considered a constant current source. 
     The contact surface  303  of the rotary encoder  300  may also include a conductive element  316  and a group of ground taps  318   a - d . The conductive element  316  may be in constant electrical contact with the wipers  312   a ,  312   b  as they travel along the resistance member  314 . In some embodiments, the conductive element  316  may be embedded or integral with the resistance member  314 , while in other embodiments the conductive element  316  may be positioned above or below the resistance member  314 . 
     The conductive element  316  facilitates the detection of an electrical signal provided to the wipers  312   a ,  312   b , as discussed further below with respect to  FIGS. 4 and 5 . The wipers  312   a ,  312   b  may be shaped and angled to maintain electrical contact with the resistance member  314  and the conductive element  316  throughout rotation of the shaft  306 . As illustrated in  FIG. 3 , the conductive element  316  may be shaped substantially the same as the resistance member  314  (e.g., in the shape of a circle or ring coaxially aligned with the axis of rotation of the shaft  306 ). As the shaft rotates, the angular positions of the shaft and the wipers change, and thus the wipers travel along the resistance member. 
     As illustrated in  FIG. 3 , the four ground taps  318   a - d  may be provided at equally spaced locations around the resistance member  314 . However, the number of ground taps  318  may vary based on the number of wipers  312 , the angle between wipers  312 , a desired accuracy of the rotary encoder  300 , the number of bits of an analog-to-digital converter (as discussed below), and the like. In some embodiments, the ground taps may be unequally spaced apart from one another. 
     The rotary encoder  300  may also include a group of electrical contacts  320   a - d . The group of electrical contacts  320   a - d  may be included in the base  302  or top  304  and may be electrically coupled to the wipers  312 , ground taps  318 , conductive element  316 , and resistance member  314 . Electrical contacts  320   a - d  may provide input and output control of elements of the rotary encoder  300 . In some embodiments at least one of the electrical contacts  320   a - d  may provide an output signal from wiper  312   a , an output signal from wiper  312   b , a control signal, a common ground, and the like. 
     With reference to  FIG. 4 , a simplified electrical diagram  400  illustrates the electrical connectivity of the rotary encoder  300 . As shown in  FIG. 4 , a resistance member  402  is positioned coaxially around a shaft  410 . A group of ground taps  404   a - d , which may correspond to the ground taps  318   a - d , may be provided around the resistance member  402 . The total resistance of the resistance member  402  may be R and the resistance member  402  may have uniform resistivity as discussed above (e.g., uniform resistance per unit of material forming the resistance member  402 ). That is, when the resistance member  402  has a uniform resistivity, the total or cumulative resistance may be defined as R in the segment from Θ=0 to Θ=2π. Accordingly, each quadrant Q 1 -Q 4  may have a predefined resistance R Q1 -R Q4 , where R Q1 +R Q2 +R Q3 +R Q4 =R. 
     As the wiper travels along (e.g., rotates around) and maintains contact with the resistance member  402  in various locations, the wiper contact points  407 ,  409  form a voltage dividing circuit as discussed below. However, although a resistance member  402  having uniform resistivity has been discussed, it should be noted that the resistance member  402  may vary its resistance in a known or predetermined manner as a function of angular displacement around the shaft axis. 
     Although four ground taps  404  are illustrated in  FIG. 4 , it should be appreciated that more or fewer ground taps may be provided. The resolution of the rotary encoder  300  may vary based on the number n of ground taps provided. As shown in  FIG. 4 , the first wiper  406  (e.g., a first contact member) and second wiper  408  (e.g., a second contact member) may be separated by an angle α. This angle α may ensure that the first and second wipers  406 ,  408  output signals in quadrature. Output signals that are in quadrature are ones whose phases are offset by a preset amount or predetermined offset. In some embodiments, the angle α may depend on the number of ground taps. In a particular embodiment, the angle α may be determined by the formula α=π(½n), where n is the number of ground taps  404 . 
     As illustrated in the example of  FIG. 4 , a first wiper  406  may contact the resistance member  402  at a contact point  407  between Θ=0 and Θ=π/2 (e.g., quadrant Q 1 ) around the resistance member  402 . Put another way, the contact point  407  may define a first portion and a second portion of the resistance member  402 . Accordingly, when a signal is applied such as a voltage VDD to the first wiper  406 , a signal may be measured at the contact point; this measured voltage varies between VDD and zero volts (e.g., ground). In some embodiments, the voltage at the wiper contact point may be measured by including a conductive trace on the wiper itself (not shown). In other embodiments, the signal transmitted through the wiper(s) may be read out using a conductive element  316  on or embedded in the contact surface  303  of the base  302  of the rotary encoder  300  (see  FIG. 3 ). The foregoing generally applies no matter which quadrant or at what contact point the wiper contacts the resistance member. 
     Generally, the voltage at the wiper contact point  407  is a function of the position of the first wiper  406  as measured along the resistance member  402 . The wiper&#39;s contact point  407  is between two ground taps, unless it is at a ground tap. For example and as shown in  FIG. 4 , the contact point  407  is in quadrant Q 1  of the resistance member  402 , defined as the segment of the resistance member between a first ground tap  404   a  and a second ground tap  404   b . The quadrant Q 1  may be thought of as two separate portions or resistors; namely one resistor R 1  extending from the first ground tap  404   a  to the wiper contact point  407 , and a second resistor R 2  extending from the first ground tap  404   a  to the wiper contact point. Each portion R 1 , R 2  will have its own voltage, which will vary with the length of the portion (e.g., the distance from the contact point to an adjacent ground tap). 
     The second wiper  408  may contact the resistance member  402  at a contact point  407  between the ground tap  404   b  and  404   c . A third resistance R 3  may be formed between the contact point of the second wiper  408  and the ground tap  404   b . A fourth resistance R 4  may be formed between the contact point of the second wiper  408  and the ground tap  404   c . As will be discussed below with respect to  FIGS. 5A-5B , a circuit may be formed enabling readout of the electrical signal at the contact points of the respective wipers  406 ,  408 . 
     Similarly, the voltage at the wiper contact point  409  is a function of the position of the wiper  408  as taken along the resistance member  402 . The wiper&#39;s contact point  409  is between two ground taps, unless it is at a ground tap. For example and as shown in  FIG. 4 , the contact point  409  is in quadrant Q 3  of the resistance member  402 , defined as the portion of the resistance member  402  between a third ground tap  404   c  and a fourth ground tap  404   d . The quadrant Q 3  may be thought of as two separate portions or resistors; namely one resistor R 3  extending from the third ground tap  404   c  to the wiper contact point  409 , and a second resistor R 4  extending from the fourth ground tap  404   d  to the wiper contact point  409 . 
     It should be noted that the foregoing is but one example of contact point locations; the wipers may contact the resistive track at any points in any quadrants (or any segment between two ground taps, if the resistive track is not separated into quadrants). Accordingly, any portion of the resistive track between two ground points (e.g., any segment) may be modeled as two resistors that have resistances varying with distance between the contact point and ground tap. 
     The circuit shown in  FIG. 5A  represents the first wiper  406  contacting the resistance member  402 . As shown in  FIG. 5A , an input signal VDD may be provided to the first wiper; the first wiper has a wiper resistance Rw. In some embodiments, the first wiper may be the first wiper  406  of  FIG. 4 . At the contact point  407  between the first wiper and the resistance member  402 , the input signal VDD is voltage divided by the first resistance R 1  and the second resistance R 2 , as shown in  FIG. 5A  and similarly in  FIG. 4 . That is, the voltage at contact point  407  varies with the resistance Rw of the wiper, R 1 , and R 2 . As the wiper  406  is rotated to angle Θ around the shaft  410  axis (e.g., as the angular position of the shaft changes), the first and second resistances R 1 , R 2  vary. 
     An input of an m-bit analog-to-digital Converter (ADC) may be electrically coupled to the contact point of the first wiper  406  while its output is electrically connected to a processor  202 . The ADC may have a reference voltage Vref determined by the ratio of Rw to R, which is the total resistance of the resistance member  402  as discussed above. In one particular embodiment, the reference voltage Vref may be determined by the formula Vref=(VDD*R)/(R+Rw). 
     The m-bit ADC may output a digitized signal Wd 1  of the voltage measured at the contact point of the first wiper  406  and the resistance member  402 . The signal at the wiper contact point  407  may be detected and monitored over time by a processor  202 , in order to determine a rotation position of the first wiper  406  and thus an angular position of the shaft, as discussed below with reference to  FIG. 6 . 
     Similar to  FIG. 5A , above,  FIG. 5B  is an example circuit which represents when the second wiper  408  contacting the resistance member  402  at contact point  409  (see also  FIG. 4 ). As shown in  FIG. 5B , an input signal VDD may be provided to a second wiper having a wiper resistance Rw. In some embodiments, the second wiper may be the second wiper  408  as shown in  FIG. 4 . 
     At the contact point between the second wiper  408  and the resistance member  402 , the input signal VDD is voltage divided by the third resistance R 3  and the fourth resistance R 4 , as shown in  FIG. 5B  and similarly in  FIG. 4 . That is, the voltage at contact point  409  varies with the resistance Rw of the second wiper, R 3 , and R 4 . As the second wiper  408  is rotated at an angle Θ around the shaft  410  axis (e.g., as the angular position of the shaft changes), the third and fourth resistances R 3 , R 4  vary. 
     An input of an m-bit Analog-to-Digital Converter (ADC) may be electrically coupled to the contact point of the second wiper  408  and may provide a digital output to a processor  202 . The ADC may have a reference voltage Vref determined by the ratio of Rw to R (e.g., the total resistance of the resistance member  402 ). In one particular embodiment, the reference voltage Vref may be determined by the formula Vref=(VDD*R)/(R+Rw). Accordingly, for a given setup with a resistance member  402  having a total resistance R around its length, and given a wiper with a resistance of Rw, the value of Vref may be constant. 
     With continuing reference to  FIG. 5B , the m-bit ADC may output a digitized signal Wd 2  of the voltage measured at the contact point of the second wiper  408  and the resistance member  402 . The signal at the wiper contact point  409  may be detected and monitored over time by a processor  202 , in order to determine a rotation position of the first wiper  406  and thus an angular position of the shaft. 
     Turning now to  FIGS. 6A and 6B , the outputs at wiper contact points  407  and  409  (as discussed above in  FIG. 5 ) are plotted as voltages cycling between zero and a maximum voltage Vref. The figure illustrates the wiper contact voltages as functions of wiper angle Θ, which is the angle between a wiper&#39;s current contact point and a zero-angle point on the resistance member (e.g., where Θ=0). Plot  602  may be a plot of the signal at the wiper contact point  407  of the first wiper  406 , and line  604  may be a plot of the signal at the wiper contact point  409  of the second wiper  408 . As shown in  FIG. 6A , as the shaft  410  is rotated (e.g., its angular position changes) causing rotation of the first and second wipers  406 ,  408 , the wiper contact point signals vary between zero and Vref. The plots  602  and  604  are out of phase by a constant, predetermined offset and thus considered to be in quadrature. The amount of quadrature or predetermined offset may depend on the angle α between the first and second wipers  406 ,  408 . By determining a phase difference between plots  602  and  604 , the rotational direction around the shaft  410  can be determined, as can the shaft&#39;s angular position. Such determination may be done by any suitable processor  202 . 
       FIG. 6A  depicts plot  602  as leading plot  604  (i.e., positively out of phase). Accordingly,  FIG. 6A  may be a plot reflecting rotation of the shaft  410  in a first direction (e.g., clockwise in  FIG. 4 ). Similarly,  FIG. 6B  depicts plot  602  as lagging plot  604  (i.e., negatively out of phase). Thus,  FIG. 6B  may be a plot reflecting rotation of the shaft  410  in a second direction (e.g., counter-clockwise in  FIG. 4 ). 
     Based on the above configuration, the resolution of the rotary encoder  300  may be adjusted to meet various design requirements. The resolution of the rotary encoder  300  may be approximately n*(2{circumflex over ( )}m), where n is the number of ground taps  404  and m is the number of bits in the m-bit ADC. Therefore, in order to increase resolution, one may provide more ground taps or a higher-bit ADC. Furthermore, one may choose an ADC and vary the number of ground taps n to increase or decrease resolution. Conversely, one may choose a number of ground taps n and vary the number of bits m of the ADC to increase or decrease resolution. The ADC may be connected electrically to, and provide digital output to, a processor  202 , such that the digital output of the ADC may be used by the processor  202  to determine an angular position of the shaft. 
     With reference now to  FIG. 7 , a simplified electrical diagram  700  of another embodiment of a rotary encoder  300  is shown, as is also suitable for use in, or as, a crown of an electronic device.  FIG. 7  illustrates the electrical connectivity of a rotary encoder similar to the rotary encoder  300  in  FIG. 3  but with a single arm (e.g., a rotor) having a first and second contact member  706 ,  708  provided thereon. The first contact member  706  may be offset by an angle α from the second contact member  708 . Here, α=π. 
     A resistive track  702  may be positioned coaxially around a shaft  710  (or other user-rotatable element). The first contact member  706  may contact the resistive track  702  at a first contact point  707 . A group of electrical sinks  704   a ,  704   b  (which act as the ground taps previously described) may be provided around the resistive track  702 . The total resistance of the resistive track  702  may be R, and the resistive track may have uniform resistivity as discussed above (e.g., a uniform resistance per unit volume of material forming the resistive track). A second resistive track  703  may be positioned radially inward from the first resistive track  702  and disposed in a half-circle around the shaft  710 . The second contact member  708  may contact the second resistive track  703  at a second contact point  709 . The radius of the second resistive track  703 , which in this example is a half-circle, may be less than the radius of the circular resistive track  702 . Another group of electrical sinks  704   c, d  may be spaced around the second resistive track  703 . In one embodiment, second resistive track  703  may have one electrical sink  704   c  at one end and another electrical sink  704   d  at the other end. 
     As illustrated in  FIG. 7 , the first contact member  706  may contact the resistive track  702  at a first contact point  707  located somewhere between Θ=0 and Θ=π. Accordingly, when a signal is applied (such as a voltage Vref) to the first contact member  706 , an output voltage at the contact point may vary between Vref and zero volts (i.e., ground). 
     A third resistance R 3  may be established between the contact point of the second contact member  708  and the electrical sink  704   c . Similarly, a fourth resistance R 4  may be established between the contact point of the second contact member  708  and the electrical sink  704   d . As was discussed above with respect to  FIGS. 5A-5B , a circuit may be formed enabling readout of the electrical signals at the contact points of the respective contact members  706 ,  708 . 
     Generally, the voltage at the first contact member&#39;s  706  contact point  707  is a function of the position of the contact member  706  along the resistive track  702 . The contact member&#39;s contact point  707  is between two electrical sinks, unless it is at an electrical sink. For example and as shown in  FIG. 7 , the contact point  707  is in quadrant Q 1 -Q 2  of the resistive track  702 , defined as the portion of the resistive track between a first electrical sink  704   a  and second electrical sink  704   b . The quadrant Q 1 -Q 2  may be thought of as two separate resistors, namely one resistor R 1  extending from the first electrical sink  704   a  to the contact point  707 , and a second resistor R 2  extending from the second electrical sink  704   b  to the contact point  707 . 
     Likewise, the voltage at the second contact member&#39;s  708  contact point  709  is a function of the position of the second contact member  708  along the second resistive track  703 . The contact member&#39;s contact point  709  is between two ground taps, unless it is at a ground tap. For example and as shown in  FIG. 7 , the contact point  709  is in quadrant Q 2 -Q 3  of the resistive track  703 , defined as the portion of the resistance member between a third electrical sink  704   c  and a fourth electrical sink  704   d . The quadrant Q 2 -Q 3  may be thought of as two separate resistors, namely a third resistor R 3  extending from the third electrical sink  704   c  to the contact point  709 , and a fourth resistor R 4  extending from the fourth electrical sink  704   d  to the wiper contact point  709 . 
     Although four electrical sinks  704  are illustrated in  FIG. 7 , it should be appreciated that more or fewer electrical sinks may be provided. The resolution of the rotary encoder  300  may vary based on the number n of electrical sinks provided. As shown in  FIG. 7 , the first contact member  706  and the second contact member  708  may be offset from one another by an angle α=π. 
     The embodiment of  FIG. 7  may have substantially the same circuitry as discussed above with respect to  FIG. 5 . That is, a voltage divider circuit is set up based on the contact position of the first contact member  706  on the first resistive track  702  and a second voltage divider circuit is formed based on the contact position of the second contact member  708  on the second resistive track  703 . As the first contact member  706  is rotated around the shaft  710  axis, the first and second resistances R 1 , R 2  vary. An input of an m-bit Analog-to-Digital Converter (ADC) may be electrically coupled to the contact point of the first contact member  706 . The m-bit ADC may output a digitized signal Wd 1  that is the voltage measured at the contact point between the first contact member  706  and the first resistive track  702 . The signal at this contact point  707  may be detected and monitored over time in order to determine a rotational position of the first contact member  706  and thus an angular position of the shaft, as discussed below with reference to  FIG. 8 . 
     Similarly, as the second contact member  708  is rotated around the shaft  710  axis, the third and fourth resistances R 3 , R 4  vary. An input of an m-bit Analog-to-Digital Converter (ADC) may be electrically coupled to the contact point of the second contact member  708 . The m-bit ADC may output a digitized signal Wd 2  of the voltage measured at this contact point between the second contact member  708  and the second resistive track  703 . The digital signal Wd 2  may be detected and monitored over time in order to determine a rotational position of the second contact member  708  and thus an angular position of the shaft, as discussed below with reference to  FIGS. 8A-8B . 
     Turning now to  FIGS. 8A-8B , the outputs at the contact points  707  and  709  are plotted as voltages cycling between zero and Vref as a function of contact member position around the axis of the shaft (e.g., the contact points and the angle Θ vary as the shaft revolves and a contact member travels along its resistive track). Plot  802  is a plot of the voltage of the first contact member  706  as measured at its contact point  707 , and plot  804  is a plot of the voltage of the second contact member  708  as measured at its contact point  709 . 
     With respect to  FIG. 8A , rotating the shaft  710  (or other user-rotatable element) causes rotation of the first and second contact members  706 ,  708  and changes the shaft&#39;s angular position. As the contact members rotate around the shaft (e.g., the angle Θ changes), their output signals vary between zero and Vref. The output of the first contact member is shown as plot  802  and the output of the second contact member is shown as plot  804 . 
     Due to the layout of the resistive tracks  702 ,  703  around the shaft  710 , plots  802  and  804  may peak at Vref at different angles of rotation Θ. This information may be used to determine the rotational direction of the contact members  706 ,  708  around the shaft  710 . For example,  FIG. 8A  may depict a rotation of the shaft  410  in a first direction (e.g., clockwise in  FIG. 7 ). Similarly,  FIG. 8B  may depict a rotation of the shaft  710  in a second direction (e.g., counter-clockwise in  FIG. 7 ). 
     With reference now to  FIGS. 9A-9B , a simplified electrical diagram  900  of another embodiment of a rotary encoder is shown. As with the other rotary encoders discussed herein, the embodiment shown in  FIGS. 9A-9B  may be used as, or in, a crown of an electronic device (such as an electronic watch).  FIG. 9A  illustrates the electrical connectivity of a rotary encoder similar to the rotary encoder in  FIG. 7  but with a conductive output track  902  and a somewhat different arrangement of resistive tracks  904 ,  906 . The resistive tracks  904 ,  906  and conductive output track  902  may be circular, concentric, and positioned coaxially around a shaft  908 . The resistive tracks  904 ,  906  and conductive output track  902  may be supported by a contact surface of a base of the rotary encoder. 
     The first resistive track  904  (e.g., a resistance member) may be positioned coaxially around the shaft  908  (or other rotatable element). A first contact member  910  (e.g., a first wiper) may contact the first resistive track  904  at a first contact point  912  and travel along the first resistive track  904  as the shaft  908  rotates with respect to an axis of the rotary encoder. A first array of electrical sinks  914   a ,  914   b ,  914   c ,  914   d  (which act as the ground taps previously described) may be provided around the first resistive track  904 . The total resistance of the first resistive track  904  may be R 1 , and the first resistive track  904  may have uniform resistivity as discussed above (e.g., a uniform resistance per unit volume of material forming the resistive track). A second resistive track  906  may be positioned radially inward from the first resistive track  904  and disposed around the shaft  908 . The total resistance of the second resistive track  906  may be R 2 , and the second resistive track  906  may have uniform resistivity as discussed above (e.g., a uniform resistance per unit volume of material forming the resistive track). R 1  and R 2  may be equal or unequal. A second contact member  916  (a second wiper) may contact the second resistive track  906  at a second contact point  918  and travel along the second resistive track  906  as the shaft  908  rotates with respect to the axis of the rotary encoder. The radius of the second resistive track  906  may be less than the radius of the first resistive track  904 . A second array of electrical sinks  914   e ,  914   f ,  914   g ,  914   h  may be spaced around the second resistive track  906 . In one embodiment, the electrical sinks  914   a - h  may be equally spaced about each of the first resistive track  904  and the second resistive track  906 . The electrical sinks  914   a - h  are indicated by diamonds in  FIG. 9A , while voltage inputs  920   a - h  (discussed below) are indicated by triangles. The shape is arbitrary and intended only to provide visual differentiation between the two. 
     The electrical sinks  914   a - h  may divide the first resistive track  904  and the second resistive track  906  into multiple segments. An array of voltage inputs may include a first array of voltage inputs  920   a ,  920   b ,  920   c ,  920   d  connected to the first resistive track  904  and a second array of voltage inputs  920   e ,  920   f ,  920   g ,  920   h  connected to the second resistive track  906 . Each voltage input  920   a - h  may be positioned between a set of adjacent electrical sinks (e.g., voltage input  920   a  may be positioned between electrical sinks  914   a  and  914   b , voltage input  920   b  may be positioned between electrical sinks  914   b  and  914   c , etc.). 
     The conductive output track  902  may be positioned radially inward from the second resistive track  906  and disposed around the shaft  908 . The radius of the conductive output track  902  may be less than the radius of the second resistive track  906 . The conductive output track  902  may be electrically connected to a voltage output  922  via a conductor  924  (e.g., a conductive trace, wire, etc.). In alternative embodiments, the concentric relationships of the tracks may differ (e.g., the resistive tracks  904 ,  906  may be interior to the conductive output track  902 ). 
     The first and second contact members  910 ,  916  may be electrically connected and coupled (affixed) to the shaft  908 . In some examples, the first and second contact members  910 ,  916  may be coupled to a single arm  926  (e.g., a rotor) that is affixed to and rotates with the shaft  908 . The entirety of the arm  926  may be conductive, or the arm  926  may include conductive traces or wires that electrically connect the first and second contact members  910 ,  916 . The first contact member  910  may be offset by an angle α (about the shaft  908 ) from the second contact member  916 . Here, α=π. A third contact member  928  (i.e., a third wiper) may be electrically connected to the first and second contact members  910 ,  916  and coupled to an arm  928  (which arm  928  may be configured similarly to the arm  926 , replaced by a portion of the shaft  908  that extends over the resistive tracks  904 ,  906 , etc.). The third contact member  928  may contact the conductive output track  902  at a third contact point  930 . The third contact member  928  may travel along, contact, or wipe the conductive output track  902  as the shaft  908  rotates with respect to the conductive output track  902 . 
     During rotation of the shaft  908  with respect to the axis of the rotary encoder, the angles of rotation (Θ) associated with the first contact member  910  and the second contact member  916  change with rotation of the shaft  908 , and thus the angles of rotation (or locations) of the first contact point  912  and the second contact point  918  change with respect to an axis of the rotary encoder. 
     As shown in  FIG. 9B , the rotary encoder may further include one or more switches  932  configured to electrically activate the first resistive track  904  while electrically floating the second resistive track  906 , and to electrically activate the second resistive track  906  while electrically floating the first resistive track  904 . For purposes of this description, a resistive track is electrically active when a current is intentionally induced to flow through the resistive track. As shown, the one or more switches  932  may include a first multiplexer  934  and a second multiplexer  936 . The first multiplexer  934  may have an input  938  configured to receive a voltage (e.g., Vdd), a first output  940  to which the voltage may be applied (as Vdd_A) when the first multiplexer  934  is placed in a first state (e.g., a logic “0” state), and a second output  942  to which the voltage may be applied (as Vdd_B) when the first multiplexer  934  is placed in a second state (e.g., a logic “1” state). The first output  940  may be coupled to the first array of voltage inputs  920   a - d  and the second output  942  may be coupled to the second array of voltage inputs  920   e - h . The second multiplexer  936  may have an input  944  configured to be coupled to ground, a first output  946  to which the ground may be connected (as Gnd_A) when the second multiplexer  936  is placed in a first state (e.g., a logic “0” state), and a second output  948  to which the ground may be connected (as Gnd_B) when the second multiplexer  936  is placed in a second state (e.g., a logic “1” state). The first output  946  may be coupled to the first array of electrical sinks  914   a - d , and the second output  948  may be coupled to the second array of electrical sinks  914 - e - h . In some examples, the control inputs of the first multiplexer  934  and the second multiplexer  936  may be electrically connected at a node  950  to which a common control signal (e.g., a binary control signal, CTRL) may be applied. The common control signal may alternately place each multiplexer  934 ,  936  in the logic “0” state or the logic “1” state. 
     When the first resistive track  904  is electrically active, and as rotation of the shaft  908  with respect to the axis of the rotary encoder causes the location of the first contact point  912  to change with respect to the first resistive track  904 , the voltage at the first contact point  912  changes (i.e., the voltage is a variable voltage). Similarly, when the second resistive track  906  is electrically active, and as rotation of the shaft  908  with respect to the axis of the rotary encoder causes the location of the second contact point  918  to change with respect to the second resistive track  906 , the voltage at the second contact point  918  changes (i.e., the voltage is a variable voltage). Because just one of the resistive tracks  904 ,  906  is electrically active at a time (while the other resistive track is floating), the voltages at the first contact point  912  and the second contact point  918  may be alternately output on the conductive output track  902 . Despite the variance in the voltages at the first contact point  912  and the second contact point  918 , the first resistive track  904 , second resistive track  904 , and/or other components of the rotary encoder may be configured to maintain a predetermined offset between the voltages. 
     Based on the voltages outputted on the conductive output track  902  (or at output  922 ), and the predetermined offset between the voltages, a processor may determine an angle of rotation of the first contact member  910 , the second contact member  916 , or the shaft  908 . The processor may also or alternatively determine a direction of rotation or speed of rotation of the shaft  908 . 
     The circuit shown in  FIG. 10  represents the first contact member  910  contacting the first resistive track  904  and the second contact member  916  contacting the second resistive track  906 . Each of the first and second resistive tracks is modeled as a set of resistors separated by grounds, in accordance with the diagram of  FIG. 9A . As shown in  FIG. 10 , the first resistive track  904  may be electrically activated by coupling Vdd_A to the first array of voltage inputs  920   a - d  and coupling Gnd_A to the first array of electrical sinks  914   a - d . Alternatively, the second resistive track  906  may be electrically activated by coupling Vdd_B to the second array of voltage inputs  920   e - h  and coupling Gnd_B to the second array of electrical sinks  914   e - h . The voltages at the first and second contact points  912 ,  918  may be alternately output at the voltage output  922  (as Vout) via the first contact member  910 , arm  926 , and conductive output track  902  (see  FIG. 9A ), and via the second contact member  916 , arm  926 , and conductive output track  902 . Each of the first contact member  910 , second contact member  916 , arm  926 , and conductive output track  902  may be associated with an impedance and consequent voltage drop that affects the voltage obtained from the first or second contact point  912 ,  918 . 
     Turning now to  FIG. 11 , an example of the voltages at the first contact point  912  and second contact point  918  (as discussed above in  FIGS. 9A, 9B, and 10 ) are plotted as voltages cycling between zero and a maximum voltage Vref (e.g., Vdd_A or Vdd_B). The figure illustrates the voltages as a function of a rotation angle Θ, which is the angle between a contact point and a zero-angle point of the resistive tracks  904 ,  906  (e.g., where Θ=0). Plot  1102  may be a plot of the voltage at the first contact point  912 , and plot  1104  may be a plot of the voltage at the second contact point  918 . As shown in  FIG. 11 , as the shaft  908  of the rotary encoder shown in  FIG. 9A  is rotated (e.g., as its angle of rotation or angular position changes), causing rotation of the first and second contact members  910 ,  916 , the voltages vary between zero and Vref. Plots  1102  and  1104  are out of phase by a constant, predetermined offset, and are thus considered to be in quadrature. The amount of quadrature or predetermined offset may depend on the angle α between the first and second contact members  910 ,  916 . By determining a phase difference between plots  1102  and  1104 , the direction of rotation of the shaft  908  can be determined, as can the shaft&#39;s angular position. Such determinations may be made by any suitable processor  202 . 
       FIG. 12  shows an example of a timing diagram for the rotary encoder shown in  FIGS. 9A and 9B . As shown, the first resistive track  904  may be electrically activated during a first time period  1202  by connecting the first array of voltage inputs  920   a - d  to Vdd_A and the first array of electrical sinks  914   a - d  to Gnd_A. The second resistive track  906  may be electrically isolated (held at a high impedance state, z) during the first time period  1202 . Similarly, the second resistive track  906  may be electrically activated during a second time period  1204  by connecting the second array of voltage inputs  920   e - h  to Vdd_A and the second array of electrical sinks  914   e - h  to Gnd_A. The first resistive track  904  may be electrically isolated (held at a high impedance state, z) during the second time period  1204 . One or more switches, such as the first multiplexer  934  and the second multiplexer  936 , may be operated to provide alternating instances of the first time period  1202  and the second time period  1204 . In some examples, electrical activation of the first resistive track  904  or the second resistive track  906  may require assertion of an enable (EN) signal  1206 . During each of the first time period  1202  and the second time period  1204 , an ADC may obtain one or more samples  1208 ,  1210  of the voltage at the first contact point  912  or the second contact point  918 . Obtaining multiple samples during each of the first time period  1202  and the second time period  1204  may improve direction of rotation or speed of rotation determinations. 
     With reference now to  FIG. 13 , a simplified electrical diagram  1300  of another embodiment of a rotary encoder is shown.  FIG. 13  illustrates the electrical connectivity of a rotary encoder similar to the rotary encoder in  FIGS. 9A-9B , but with a single resistive track  1302  and multiple conductive output tracks  1304 ,  1306 . The resistive track  1302  and conductive output tracks  1304 ,  1306  may be circular, concentric, and positioned coaxially around a shaft  1308 . The resistive track  1302  and conductive output tracks  1304 ,  1306  may be supported by a contact surface of a base of the rotary encoder. 
     The resistive track  1302  (i.e., a resistance member) may be positioned coaxially around the shaft  1308  (or other rotatable element). A first contact member  1310  (i.e., a first wiper) may contact the resistive track  1302  at a first contact point  1312  and travel along the resistive track  1302  as the shaft  1308  rotates with respect to an axis of the rotary encoder. A second contact member  1314  (i.e., a second wiper) may contact the resistive track  1302  at a second contact point  1316  and travel along (e.g., wipe) the resistive track  1302  as the shaft  1308  rotates with respect to the axis of the rotary encoder. The first contact member  1310  may be electrically connected to a first arm  1318  (e.g., a first rotor) that is affixed to and rotates with the shaft  1308 . The second contact member  1314  may be electrically connected to a second arm  1320  (e.g., a second rotor) that is affixed to and rotates with the shaft  1308 . The first arm  1318  may be electrically isolated from the second arm  1320 . The entireties of the first and second arms  1318 ,  1320  may be conductive, or the first and second arms  1318 ,  1320  may include conductive traces or wires that electrically connect to the first or second contact member  1310 ,  1314 . In other examples, the first and second contact members  1310 ,  1314  may be affixed to the shaft  1308  in other ways (e.g., the shaft  1308  may have a portion that extends outward from the axis of the rotary encoder and over the resistive track  1302 , and the first and second contact members  1310 ,  1314  may be formed on or attached to a surface of the shaft  1308  that faces the resistive track  1302 ). The first contact member  1310  may be offset by an angle α (about the shaft  1308 ) from the second contact member  1310 . 
     An array of electrical sinks  1322   a ,  1322   b ,  1322   c ,  1322   d  (which act as the ground taps previously described) may be provided around the resistive track  1302 . The total resistance of the resistive track  1302  may be R, and the resistive track  1302  may have uniform resistivity as discussed above (e.g., a uniform resistance per unit volume of material forming the resistive track). In one embodiment, the electrical sinks  1322   a - d  may be equally spaced about the resistive track  1302 . The electrical sinks  1322   a - d  may divide the resistive track  1302  into multiple segments. An array of voltage inputs  1324   a ,  1324   b ,  1324   c ,  1324   d  may also be connected to the resistive track  1302 . Each voltage input  1324   a - d  may be positioned between a set of adjacent electrical sinks (e.g., voltage input  1324   a  may be positioned between electrical sinks  1322   a  and  1322   b , voltage input  1324   b  may be positioned between electrical sinks  1322   b  and  1322   c , etc.). 
     A first conductive output track  1304  and a second conductive output track  1306  may be positioned radially inward from the resistive track  1302  and disposed around the shaft  1308 . The radius of the first conductive output track  1304  may be less than the radius of the resistive track  1302 , and the radius of the second conductive output track  1306  may be less than the radius of the first conductive output track  1304 . The first conductive output track  1304  may be electrically connected to a first voltage output  1326  via a first conductor  1328  (e.g., a conductive trace, wire, etc.), and the second conductive output track  1306  may be electrically connected to a second voltage output  1330  via a second conductor  1332 . In alternative embodiments, the concentric relationships of the tracks may differ (e.g., the resistive track  1302  may be interior to the conductive output tracks  1304 ,  1306 ). 
     A third contact member  1334  (e.g., a third wiper) may be electrically connected to the first contact member  1310  and coupled to the first arm  1318  (or otherwise affixed to the shaft  1308 ). The third contact member  1334  may contact the first conductive output track  1304  at a third contact point  1336 . The third contact member  1334  may contact, travel along, or otherwise wipe the conductive output track  1304  as the shaft  1308  rotates with respect to the axis of the rotary encoder. A fourth contact member  1338  (e.g., a fourth wiper) may be electrically connected to the second contact member  1314  and coupled to the second arm  1324  (or otherwise affixed to the shaft  1308 ). The fourth contact member  1338  may contact the second conductive output track  1306  at a fourth contact point  1340 . The fourth contact member  1338  may contact or wipe the second conductive output track  1306  as the shaft  1308  rotates with respect to the axis of the rotary encoder. 
     During rotation of the shaft  1308  with respect to the axis of the rotary encoder, the angles of rotation (Θ) associated with the first contact member  1310  and the second contact member  1314  change with rotation of the shaft  1308 , and thus the angles of rotation (or locations) of the first contact point  1312  and the second contact point  1316  change with respect to the axis of the rotary encoder. 
     As rotation of the shaft  1308  with respect to the axis of the rotary encoder causes the locations of the first and second contact points  1312 ,  1316  to change with respect to the resistive track  1302 , the voltages at the first and second contact points  1312 ,  1316  change (e.g., the voltages are variable voltages). The voltage at the first contact point  1312  may be output via the first conductive output track  1304 , and the voltage at the second contact point  1316  may be output via the second conductive output track  1306 . Despite the variance in the voltages at the first contact point  1312  and the second contact point  1316 , the resistive track  1302  and/or other components of the rotary encoder may be configured to maintain a predetermined offset between the voltages. 
     Based on the voltages (Vout 0 , Vout 1 ) outputted on the first and second conductive output tracks  1304 ,  1306  (or at outputs  1326  and  1330 ), and the predetermined offset between the voltages, a processor may determine an angle of rotation of the first contact member  1310 , the second contact member  1310 , or the shaft  1308 . The processor may also or alternatively determine a direction of rotation or speed of rotation of the shaft  1308 . 
     The circuit shown in  FIG. 14  represents the first and second contact members  1310 ,  1314  contacting the resistive track  1302 . As shown in  FIG. 14 , the resistive track  1302  may be electrically activated by coupling Vdd to the array of voltage inputs  1324   a - d  and coupling Gnd to the array of electrical sinks  1322   a - d . The voltages at the first and second contact points  1312 ,  1316  may be simultaneously output at the first and second voltage outputs  1326 ,  1330 , as Vout_ 0  and Vout_ 1 , via the first contact member  1310 , first arm  1318 , and first conductive output track  1304  (see  FIG. 13 ), and via the second contact member  1314 , second arm  1320 , and second conductive output track  1306 . Each of the first contact member  1310 , second contact member  1314 , first arm  1318 , second arm  1320 , first conductive output track  1304 , and second conductive output track  1306  may be associated with an impedance and consequent voltage drop that affects the voltage obtained from the first or second contact point  1312 ,  1316 . The voltages at the first contact point  1312  and second contact point  1316  may be plotted as voltages cycling between zero and a maximum voltage Vref (e.g., Vdd), with Vout_ 0  being plotted as plot  1102  in  FIG. 11  and Vout_ 1  being plotted as plot  1104  in  FIG. 11 . 
     With reference now to  FIG. 15 , a simplified electrical diagram  1500  of another embodiment of a rotary encoder is shown. This rotary encoder may be used as, or in, a crown of an electronic device, similar to other rotary encoders discussed herein.  FIG. 15  illustrates the electrical connectivity of a rotary encoder with a single resistive track  1502  and a single conductive output track  1504 . The resistive track  1502  and conductive output track  1504  may be circular, concentric, and/or positioned coaxially around a shaft  1506 . The resistive track  1502  and conductive output track  1504  may be supported by a contact surface of a base of the rotary encoder. 
     The resistive track  1502  (or any other resistance member) may be positioned coaxially around the shaft  1506  (or other rotatable element), but may have a radial gap  1508  in its circumference. A first contact member  1510  (i.e., a first wiper) may contact the resistive track  1502  at a first contact point  1512  and wipe (e.g. travel along) the resistive track  1502  as the shaft  1506  rotates with respect to an axis of the rotary encoder. A second contact member  1514  (a second wiper) may contact the resistive track  1502  at a second contact point  1516  and wipe the resistive track  1502  as the shaft  1506  rotates with respect to the axis of the rotary encoder. The total resistance of the resistive track  1502  may be R, and the resistive track  1502  may have uniform resistivity as discussed above (e.g., a uniform resistance per unit volume of material forming the resistive track). 
     A first end  1518  of the resistive track  1502  may be electrically connected to a voltage input  1520 , which voltage input  1520  may receive a voltage such as Vdd. In some examples, the voltage input  1520  may be coupled to the first end  1518  of the resistive track  1502  via a resistor  1522  (e.g., a resistive trace, a wire, etc.). As shown in  FIG. 15 , a less resistive conductor  1524 , or other more or less resistive elements may also be used to couple the voltage input  1520  to the first end  1518  of the resistive track  1502 . A reference voltage output  1526  may also be coupled to the first end  1518  of the resistive track  1502 . A second end  1528  of the resistive track  1502  may not be electrically connected to other elements. 
     The conductive output track  1504  may be positioned radially inward from the resistive track  1502  and disposed around the shaft  1506 . The radius of the conductive output track  1504  may be less than the radius of the resistive track  1502 . The conductive output track  1504  may be electrically connected to a constant current regulation circuit  1530 . In alternative embodiments, the concentric relationship of the tracks may differ (e.g., the resistive track  1502  may be interior to the conductive output track  1504 , the two may be positioned such that they are not separated by an equal distance around their circumferences, and so on). The constant current regulation circuit  1530  supplies a constant current to the conductive output track  1504 , thereby enabling the voltage Vout to change as the contact member traverses the track, as described below. It should be appreciated that other embodiments described herein may likewise include constant current sources, and that any constant current source may be the illustrated constant current regulation circuit  1530 . 
     The first and second contact members  1510 ,  1514  may be electrically connected and coupled to a single arm  1532  (e.g., a rotor) that is affixed to and rotates with the shaft  1506 . The entirety of the arm  1532  may be conductive, or the arm  1532  may include conductive traces or wires that electrically connect the first and second contact members  1510 ,  1514 . In other examples, the first and second contact members  1510 ,  1514  may be affixed to the shaft  1506  in other ways (e.g., the shaft  1506  may have a portion that extends outward from the axis of the rotary encoder and over the resistive track  1502 , and the first and second contact members  1510 ,  1514  may be formed on or attached to a surface of the shaft  1506  that faces the resistive track  1502 ). The first contact member  1510  may be offset by an angle α (about the shaft  1506  from the second contact member  1514 . Here, α=π. A third contact member  1534  (i.e., a third wiper) may be electrically connected to the first and second contact members  1510 ,  1514  and coupled to the arm  1532  (or otherwise affixed to the shaft  1506 ). The third contact member  1534  may contact the conductive output track  1504  at a third contact point  1536 . The third contact member  1534  may contact or wipe the conductive output track  1504  as the shaft  1506  rotates with respect to the axis of the rotary encoder. 
     During rotation of the shaft  1506  with respect to the axis of the rotary encoder, the angles of rotation (Θ) associated with the first contact member  1510 , the second contact member  1514 , and the third contact member  1534  change with rotation of the shaft  1506 , and thus the angles of rotation (or locations) of the first contact point  1512 , the second contact point  1516 , and the third contact point  1536  change with respect to the axis of the rotary encoder. 
     As rotation of the shaft  1506  with respect to the axis of the rotary encoder causes the locations of the first and second contact points  1512 ,  1516  to change with respect to the resistive track  1502 , the voltage at the third contact point  1516  changes (thus, the voltage is a variable voltage). The voltage (Vout) at the third contact point  1516  may be output via the conductive output track  1504 . 
     Based on the voltage (Vout) outputted on the conductive output track  1504 , and a reference voltage (Vref) that is outputted at the reference voltage output  1526 , a processor may determine an angle of rotation of the first contact member  1510 , the second contact member  1514 , the third contact member  1534 , or the shaft  1506 . The processor may also or alternatively determine a direction of rotation or speed of rotation of the shaft  1506 . 
     The circuit  1600  shown in  FIG. 16  represents the first and second contact members  1510 ,  1514  contacting the resistive track  1502 . As shown in  FIG. 16 , the reference voltage output  1526  may be coupled to the voltage input  1520  via the resistor  1522 , and the resistive track  1502  may be coupled between the reference voltage output  1526  and the constant current regulation circuit  1530 . The voltage (Vout) at the third contact point  1516  may be based on the locations of the first contact point  1512  and the second contact point  1516  with respect to the resistive track  1502 . The constant current regulation circuit  1530  ensures that the current provided to the conductive output track  1504  is invariant, and thus that the voltage changes in a known fashion as the contact member traverses (wipes) the conductive output track  1504 . It should be appreciated that the constant current regulation circuit is not electrically connected to the resistive track  1502 . 
       FIG. 17  illustrates an example plot  1702  of the difference between the voltage (Vout) that is output via the conductive output track  1504  and the reference voltage (Vref) that is output via the reference voltage output  1526  (as discussed above in  FIG. 15 ). The voltage difference cycles between zero and a maximum voltage Vref. The figure illustrates the voltages as a function of a rotation angle Θ, which is the angle between a contact point and a zero-angle point of the resistive track  1502  (e.g., where Θ=0). As shown in  FIG. 17 , as the shaft  1506  is rotated (e.g., as its angle of rotation or angular position changes), causing rotation of the first, second, and third contact members  1510 ,  1514 ,  1534 , the voltage difference varies between zero and Vref in a sawtooth pattern. The slope direction of the sawtooth pattern is indicative of the direction of rotation of the shaft  1506 . 
     With reference now to  FIG. 18 , another embodiment of a compact rotary encoder  1800  is illustrated for use as a crown in an electronic device, such as electronic device  100 . In some embodiments the rotary encoder  1800  may be coupled to the input device  106  of the electronic device  100  such that a shaft  1806 , or other rotatable element, of the rotary encoder  1800  rotates when the input device  106  rotates. As discussed above, in some embodiments the input device  106  may be the rotating crown of an electronic watch. The rotary encoder  1800  may include a base  1802 , cover  1804 , and a contact surface  1803  of the base  1802 . The cover  1804  may include an aperture  1808  through which a rotating shaft  1806  passes, such that the shaft is at least partially received within the housing. In some embodiments, the cover  1804  may be a housing of an electronic device in which the rotary encoder is at least partially enclosed. For example, a knob, portion of the shaft, or other user-manipulable element may protrude from an electronic device housing. A user may turn the user-manipulable element, thereby causing the shaft  1806  to rotate about an axis extending along a length of the shaft. A user may rotate a crown of an electronic watch in this fashion, as one example. 
     At least two capacitive members  1810   a ,  1810   b  may extend outwardly in a radial direction from the shaft  1806 . The capacitive members  1810   a ,  1810   b  may be coupled to the shaft  1806  and separated by an angle α around the shaft  1806 . It should be noted that although two capacitive members  1810   a ,  1810   b  are illustrated, more capacitive members  1810  may be coupled to the shaft  1806  and separated by other angles α. 
     Each capacitive member  1810   a ,  1810   b  may have a known capacitance. The contact surface  1803  of the base  1802  may have a capacitance sensing region  1814 . The capacitance sensing region  1814  may include or define capacitance sensors  1816 . In some embodiments the capacitance sensing region  1814  may be embedded or integral with the contact surface  1803 . As shown in  FIG. 18 , the capacitance sensing region  1814  may be disposed coaxially beneath the rotating shaft  1806  such that capacitive members  1810   a ,  1810   b  rotate with respect to each other while maintaining a predetermined separation distance. That is, the capacitive members  1810   a ,  1810   b  rotate angularly with the shaft  1806  and interact with the capacitance sensors  1816  in the capacitance sensing region  1814  at different points throughout a full rotation. 
     The rotary encoder  1800  may also include a group of electrical contacts  1820   a - d . The group of electrical contacts  1820   a - d  may be included in the base  1802  and may be electrically coupled to the capacitive members  1810   a, b  and capacitance sensors  1816 . Electrical contacts  1820   a - d  may provide input and output control of elements of the rotary encoder  1800 . 
     In a particular example, as shown in  FIG. 19 , a capacitive member  1810   a  of the rotary encoder  1800  may substantially overlap a capacitance sensor  1816 , at an example angle Θ of rotation. Accordingly, the capacitance sensor  1816  which substantially aligns with capacitive member  1810   a  in  FIG. 19  may detect a maximum capacitance of the capacitive member  1810   a . Conversely, the capacitive member  1810   b  in  FIG. 19  overlaps only a portion of the capacitance sensor  1816 . Therefore, the capacitance sensor corresponding to capacitive member  1810   b  may sense a capacitance between zero and the maximum capacitance of the capacitive member  1810   b . As shown in  FIG. 19 , the capacitive member  1810   a ,  1810   b  may be separated by an angle α. Analogous to the angle α described with respect to  FIG. 4 , the angle α may be chosen to ensure that the first and second  1801   a ,  1801   b  output signals in quadrature, or output signals whose phases are offset by a preset amount (such as a predetermined offset). 
       FIG. 20  illustrates an exemplary plot of the digitized output of the capacitance sensors  1816  as a function of rotation angle Θ of capacitive members  1810   a, b  around the shaft  1806  (or other user-rotatable element). Similar to the embodiment of  FIG. 3  discussed above, the angle α between the first capacitive member  1810   a  and the second capacitive member  1810   b  may be chosen to ensure that the capacitance signals recorded are in quadrature. The outputs of capacitance sensors  1816  may be digitized by m-bit ADCs as discussed above with respect to  FIGS. 5A and 5B and 6A and 6B  and plotted as voltages cycling between zero and Vref as a function of wiper position Θ around the axis of the shaft  1806 . Plot  2002  is a plot of a digital voltage Wd 1  of the first capacitive member  1810   a , and plot  2004  is a plot of a digital voltage Wd 2  of the second capacitive member  1810   b . As shown in  FIG. 20A , as the shaft  1806  rotates, the signals Wd 1  and Wd 2  vary between zero and Vref. 
     The plots  2002  and  2004 , corresponding to Wd 1  and Wd 2  respectively, are out of phase by a predetermined offset and thus considered to be in quadrature. The amount of quadrature (e.g., the predetermined offset) may result from the angle α between the first and second capacitive members  1810   a, b . By determining the phase difference between plots  2002  and  2004 , the rotational direction around the shaft  1806  can be determined. 
       FIG. 20A  is a leading plot  2004  (e.g., the signals are positively out of phase). Accordingly,  FIG. 20A  illustrates the capacitive members&#39; outputs as the shaft  1806  rotates in a first direction (clockwise in  FIG. 19 ). Similarly,  FIG. 20B  is a lagging plot  2004  (e.g., the signals are negatively out of phase). Thus,  FIG. 20B  reflects rotation of the shaft  1806  in a second direction (counter-clockwise in  FIG. 19 ). 
       FIG. 21  illustrates a method  2100  that may be performed to control a function of an electronic device (e.g., the electronic device  100  of  FIG. 1 ) based on an angle of rotation of a first wiper of a rotary encoder about an axis of a user-rotatable element (e.g., a shaft) of the rotary encoder. The first wiper may be affixed to the user-rotatable element and in contact a resistance member (e.g., a resistive track) or a conductive output track of the rotary encoder. The method  2100  may be performed by a processor. In some examples, the rotary encoder may be any of the rotary encoders described in the present disclosure, or any rotary encoder that incorporates aspects of the rotary encoders described in the present disclosure. 
     At block  2102 , the operation(s) may include receiving at least one output signal from the rotary encoder. The output signal(s) may include one or more voltages at one or more contact points between the first wiper and the resistance member or conductive output track (e.g., the signals or voltages output by any of the rotary encoders described with reference to  FIGS. 1-20 ). 
     At block  2104 , the operation(s) may include identifying, based on the at least one output signal, the angle of rotation of the first wiper of the rotary encoder about the axis of the rotatable element of the rotary encoder. 
     At block  2106 , the operation(s) may include controlling a function of the electronic device based on the angle of rotation. 
     In some examples of the method  2100 , the at least one output signal may include a first variable voltage associated with contact between the first wiper and the resistance member and a second variable voltage associated with contact between a second wiper of the rotary encoder and another resistance member (e.g., another resistive track) of the rotary encoder (e.g., the voltages output by the rotary encoder described with reference to  FIGS. 9-12 ). The second wiper may also be affixed to the user-rotatable element, and the first variable voltage may be out of phase with the second variable voltage by a predetermined offset. In these examples, identifying the angle of rotation may include comparing the first variable voltage to the second variable voltage. In some examples, the method  2100  may further include a direction of rotation or speed of rotation of the user-rotatable element based on the first variable voltage, the second variable voltage, and the predetermined offset. 
     In some examples of the method  2100 , the at least one output signal may include a variable voltage and a reference voltage (e.g., the voltages output by the rotary encoder described with reference to  FIGS. 15-17 ). The variable voltage may be associated with contact between the first wiper and the conductive output track, contact between a second wiper of the rotary encoder and the resistance member, and contact between a third wiper and the resistance member. The second wiper and the third wiper may be affixed to the user-rotatable element. The reference voltage may be associated with a reference voltage output coupled to the resistance member. In these examples, identifying the angle of rotation may include comparing the variable voltage to the reference voltage. 
       FIGS. 22A-24B  generally depict examples of manipulating graphics displayed on an electronic device through inputs provided by rotating a crown of the device. This manipulation (e.g., selection, acknowledgement, motion, dismissal, magnification, and so on) of a graphic may result in changes in operation of the electronic device and/or graphics displayed by the electronic device. Although specific examples are provided and discussed, many operations may be performed by rotating and/or translating a crown incorporating a rotary encoder. Accordingly, the following discussion is by way of example and not limitation. 
       FIG. 22A  depicts a sample electronic device  2200  (shown here as an electronic watch) having a rotatable crown  2210 . The rotatable crown  2210  may be, or incorporate, any rotary encoder described herein. A display  2220  shows information and/or other graphics. In the current example, the display  2220  depicts a list of various items  2230 ,  2240 ,  2250 , all of which are example graphics. 
       FIG. 22B  illustrates how the graphics shown on the display  2220  change as the crown  2210  rotates (as indicated by the arrow  2270 ). Rotating the crown  2210  causes the list to scroll or otherwise move on the screen, such that the first item  2230  is no longer displayed, the second and third items  2240 ,  2250  each move upwards on the display, and a fourth item  2260  is now shown at the bottom of the display. This is one example of a scrolling operation that can be executed by rotating the crown  2210 . Such scrolling operations may provide a simple and efficient way to depict multiple items relatively quickly and in sequential order. A speed of the scrolling operation may be controlled by the speed at which the crown  2210  is rotated—faster rotation may yield faster scrolling, while slower rotation yields slower scrolling. The crown  2210  may be translated (e.g., pushed inward toward the display  2220  or watch body) to select an item from the list, in certain embodiments. 
       FIGS. 23A-23B  illustrate an example zoom operation. The display  2220  depicts a picture  2300  at a first magnification, shown in  FIG. 23A ; the picture  2300  is yet another example of a graphic. As the crown  2210  of the electronic watch  2200  rotates (again, illustrated by arrow  2270 ), the display may zoom into the picture, such that a portion  2310  of the picture is shown at an increased magnification. This is shown in  FIG. 23B . The direction of zoom (in vs. out) and speed of zoom, or location of zoom, may be controlled through rotation of the crown  2210 , and particularly through the direction of rotation and/or speed of rotation. Rotating the crown in a first direction may zoom in, while rotating the crown in an opposite direction may zoom out. Alternately, rotating the crown in a first direction may change the portion of the picture subject to the zoom effect. In some embodiments, pressing the crown may toggle between different zoom modes or inputs (e.g., direction of zoom vs. portion of picture subject to zoom). In yet other embodiments, pressing the crown may return the picture  2300  to the default magnification shown in  FIG. 23A . 
       FIGS. 24A-24B  illustrate possible use of the crown  2210  to change an operational state of the electronic watch  2200  or otherwise toggle between inputs. Turning first to  FIG. 24A , the display  2220  depicts a question  2400 , namely, “Would you like directions?” As shown in  FIG. 24B , the crown  2210  may be rotated (again, illustrated by arrow  2270 ) to answer the question. Rotating the crown provides an input interpreted by the electronic watch  2200  as “yes,” and so “YES” is displayed as a graphic  2410  on the display  2220 . Rotating the crown  2210  in an opposite direction may provide a “no” input. 
     In the embodiment shown in  FIGS. 24A-24B , the crown&#39;s rotation is used to directly provide the input, rather than select from options in a list (as discussed above with respect to  FIGS. 22A-22B ). 
     As mentioned previously, rotational input from a crown of an electronic device may control many functions beyond those listed here. The crown may rotate to adjust a volume of an electronic device, a brightness of a display, or other operational parameters of the device. The crown may rotate to turn a display on or off, or turn the device on or off. The crown may rotate to launch or terminate an application on the electronic device. Further, translational input of the crown may likewise initiate or control any of the foregoing functions, as well. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. For example, certain embodiments may employ a resistive track, output track, and/or resistance member that is substantially flat. However, this need not be the case. Embodiments may employ tracks and/or members that vary in the Z dimension as well as within an X-Y plane. Some such tracks/members may have raised or lowered portions in order to facilitate electrical routing, provide space for other components of the embodiment or other components in an electronic device housing the embodiment, to ensure or enhance contact between a wiper and the member or track in a specific region, and so on. Accordingly, it should be understood that any and all of the embodiments described herein may have non-planar tracks or other members. 
     Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not targeted to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20170516
Publication Date: 20200204
Grant Date: 20200204
Priority Date: 20160517
Inventors: BUSHNELL, TYLER S.
CLAVELLE, Adam T.
WERNER, CHRISTOPHER M.
ELY, COLIN M.
SWEET, STEPHEN N.
MOORTHY, SRIRAM
PENG, Huan
Assignee: APPLE INC
CPC Classifications: [{"code": "G04C3/008", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/1655", "inventive": true, "first": true, "tree": "[]"}, {"code": "G04C3/002", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B3/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/1655", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04B3/04", "inventive": true, "first": false, "tree": "[]"}, {"code": "G04G21/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "G04G21/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/1655", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01D5/2412", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01D5/2412", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 69230068