throbber
US008432173B2
`
`(12) Unlted States Patent
`(10) Patent No.:
`US 8,432,173 B2
`
`Philipp
`(45) Date of Patent:
`Apr. 30, 2013
`
`(54) CAPACITIVE POSITION SENSOR
`
`-
`-
`.
`Inventor. Harald Ph111pp, Zug (CH)
`(75)
`(73) Assignee: Atmel Corporation, San Jose, CA (US)
`( * ) Notice:
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 15403) by 0 days.
`
`(21) Appl‘ No“ 13/118380
`
`(22)
`
`Filed:
`
`May 27, 2011
`
`7,920,129 B2
`8,031,094 B2
`8,031,174 B2
`8,040,326 B2
`8:173:31 E;
`2003/0043174 A1
`2004/0027395 A1
`2004/0196267 A1
`2004/0207605 A1
`
`4/2011 Hotelling
`10/2011 Hotelling
`10/2011 Hamblin
`10/2011 Hotelling
`3
`.
`lééggfi gigfllmg
`3/2003 Hinckley et a1.
`2/2004 Lection et a1.
`10/3004 Kawai et 31~
`10/2004 Mackey
`(Continued)
`FOREIGN PATENT DOCUMENTS
`
`DE
`DE
`
`19645907 A1
`19903300 A1
`
`5/1998
`8/1999
`
`(65)
`
`Prior Publication Data
`US 2011/0227589 A1
`Sep. 22, 2011
`
`(Continued)
`OTHER PUBLICATIONS
`
`Related US. Application Data
`
`(63) Continuation of application No. 12/703,614, filed on
`Feb. 10, 2010, now Pat. No. 7,952,367, which is a
`continuation of application No. 11/868,566, filed on
`Oct. 8, 2007, now abandoned.
`
`UK Intellectual Property Office, Combined Search and Examination
`Report in Corresponding UK application, Feb. 22, 2008.
`
`(Continued)
`
`Primary Examiner 7 Vincent Q Nguyen
`(74) Attorney, Agent, or Firm 7 Baker Botts L.L.P.
`
`ABSTRACT
`(57)
`In one embodiment, a method includes receiving one or more
`first signals indicating one or more first capacitive couplings
`of an object with a sensing element that comprises a sensing
`path that comprises a length. The first capacitive couplings
`correspond to the Obie“ coming into PYOXimitY With the sens-
`ing element at a first position along the sensing path of the
`sensing element. The method includes determining based on
`one or more ofthe first signals the first position ofthe object
`along the sensing path and setting a parameter to an initial
`value based on the first position of the object along the sens-
`ing path. The initial value includes a particular parameter
`value and is associated with a range of parameter values. The
`range ofparameter values is associated with the length ofthe
`.
`sensmg Path
`
`19 Claims, 4 Drawing Sheets
`
`(60)
`
`(51)
`
`(2006.01)
`
`530233611211 application No. 60/862,358, filed on Oct.
`’
`i
`Int. Cl.
`go1R 27/26
`(52) US. Cl.
`USPC ........................................... 324/686 324/667
`(58) Field of Classification Search
`5324/667
`............324/67E690,
`See application file for complete search history
`
`.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
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`4,121,204 A
`4,264,903 A
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`{3355}
`
`‘33
`
`1.316
`.5
`
`33306
`WA3
`“Wm.“
`«MW
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`290:0Vi“:2we" mane
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`M}...
`.8 333330
`“\
`fit“
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`3’
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`“if
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`:30
`
`1
`
`CYPRESS 1001
`CYPRESS 1001
`
`1
`
`

`

`US 8,432,173 B2
` Page 2
`
`US. PATENT DOCUMENTS
`
`3/2005 Philipp
`2005/0052429 A1
`4/2005 Philipp
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`4/2008 Philipp
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`5/2009 Philipp
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`
`DE
`DE
`DJ:
`DE
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`
`EP
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`
`WO
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`gggig
`WO 22021291293461; A4
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`-
`-
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`-
`tional Search Report mailed May 7, 2010, 3 pages.
`International Application Serial No. PCT/US2009/069322, Written
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`.
`.1 d M 7 2010 5
`.
`<
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`.ay ,
`.
`, Pages
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`U.S. Appl. No. 61/454,894, filed Mar. 21, 2011, Rothkopf.
`
`2
`
`

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`

`1
`CAPACITIVE POSITION SENSOR
`
`RELATED APPLICATIONS
`
`US 8,432,173 B2
`
`2
`
`This application is a continuation under 35 U.S.C. §120 of 5
`US. patent application Ser. No. 12/703,614, filed 10 Feb.
`2010, which is a continuation under 35 U.S.C. §120 of US.
`patent application Ser. No. 11/868,566, filed 8 Oct. 2007,
`which claims the benefit under 35 U.S.C. §119(e) of US.
`Provisional Patent Application No. 60/862,358, filed 20 Oct.
`2006.
`
`10
`
`TECHNICAL FIELD
`
`This disclosure generally relates to touch sensors.
`
`15
`
`BACKGROUND
`
`25
`
`Particular embodiments relate to capacitive position sen-
`sors. Particular embodiments relate more particularly to 20
`capacitive position sensors for detecting the position of an
`object around a curved path.
`Capacitive position sensors are applicable to human inter-
`faces as well as material displacement sensing in conjunction
`with controls and appliances, mechanisms and machinery,
`and computing.
`Capacitive position sensors in general have recently
`become increasingly common and accepted in human inter-
`faces and for machine control. In the field ofhome appliances,
`it is now quite common to find capacitive touch controls 30
`operable through glass or plastic panels. These sensors are
`increasingly typified by US. Pat. No. 6,452,514 which
`describes a matrix sensor approach employing charge-trans-
`fer principles. Electrical appliances, such as TVs, washing
`machines, and cooking ovens increasingly have capacitive 35
`sensor controls for adjusting various parameters, for example
`volume, time and temperature.
`Due to increasing market demand for capacitive touch
`controls, there is an increased need for lower cost-per-func-
`tion as well as greater flexibility in usage and configuration. 40
`There exists a substantial demand for new human interface
`
`technologies which can, at the right price, overcome the tech-
`nical deficits of electromechanical controls on the one hand,
`and the cost of touch screens or other exotica on the other.
`
`EP1273851A2 discloses a device for adjusting tempera- 45
`ture settings, power settings or other parameters of a cooking
`apparatus. The device comprises a strip sensor which may be
`linear, curved or circular and may be a capacitive touch sensor
`or some other form of touch sensor. A linear display is
`arranged in parallel to the sensor. The capacitive touch sensor 50
`is sensitive to the touch of a finger and the display strip is
`made up of multiple display segments which illuminate to
`show the current touch setting as defined by a finger touch on
`the capacitive touch sensor. A predetermined calibration
`curve relating to a parameter to be adjusted is mapped onto 55
`the strip, the range extending from a minimum value to a
`maximum value. The minimum value may correspond to an
`off condition of the domestic appliance. Additional opera-
`tional modes may be associated with the adjustment strip to
`ascribe new functions to the sensor strip. These can be 60
`selected by touching the display for a certain time. For
`example, a first additional mode can be entered by touching
`for 5 seconds, and a second additional mode by touching for
`10 seconds. One of the additional operational modes is a
`zoom mode which provides for fine adjustment ofthe param-
`eter value. The zoom operational mode can be activated by a
`contact time of, for example, 10 seconds. In the zoom mode
`
`65
`
`an additional digital display is activated to show the current
`numerical value ofthe parameter being adjusted. In the zoom
`mode, only a fraction (e.g. 10%) of the original adjustment
`range is mapped onto the adjustment strip so that moving a
`finger across the full length of the sensor strip from left to
`right (or right to left) will only increase (decrease) the current
`setting of the parameter value, thereby providing a finer
`adjustment. During this fine adjustment, the display strip
`keeps its original function as a relative indicator of the full
`range between the minimum and maximum values.
`More generally, linear, curved and circular sensor strips for
`adjusting cooker settings have been known for many years,
`for example see US. Pat. No. 4,121,204 (resistive or capaci-
`tive
`sensor),
`DE19645907A1
`(capacitive
`sensor),
`DE19903300A1 (resistive sensor), and EP1602882A1 (opti-
`cal sensor).
`W02006/133976A1, WO2007/006624A1 and WO2007/
`023067A1 are more recent examples of work on touch-sen-
`sitive control strips for domestic appliances using capacitive
`sensors. These three patent applications were filed before the
`priority date of the present application, but first published
`after the priority date of the present application. In particular,
`WO2006/133976A1 and WO2007/023067A1 disclose sen-
`sors with a zoom function similar to the above described
`
`EP1273851A2 which is used for setting a timer.
`W02006/133976A1 provides an adjustment strip with two
`operational modes. In the first mode the full parameter value
`range is mapped across the sensor strip. For example 0 to 99
`minutes in a timer function. If a user wishes to set the timer to
`
`30 minutes, he touches the strip approximately one third way
`along. A parameter value of say 34 minutes is sensed by the
`capacitive sensor, and displayed to the user on a numeric
`display. Once the initial value has been set, the effect of
`touching the sensor field is automatically changed to a second
`mode in which the parameter value is decreased (or
`increased) finely from the initially selected value by an
`amount that depends on the distance moved by the finger
`along the sensor strip. In the example, the user can then slide
`his finger from right to left to reduce the time from 34 minutes
`to the desired 30 minutes, using the display for visual feed-
`back. In this way, the user can initially make a rough selection
`of the desired parameter value with a point and touch action,
`and then refine it to the exact value desired by a finger sliding
`action.
`
`W02007/023067A1 provides an adjustment strip with two
`operational modes that switch between mapping the full
`parameter value range across the sensor strip and a partial
`range selected to show the sub-range of parameter values
`between which the parameter is mo st often set by a user. The
`example of setting the timer on a cooker is given.
`While a zoom function is useful, prior art implementations
`ofthe zoom function have limitations regarding the manner in
`which the transition is effected from the full range mode to the
`zoom mode. In EP1273851A2, the user is made to wait for a
`certain time, 10 seconds in the specific example, until the
`transition occurs. On the other hand, in WO2006/133976A1
`the transition automatically occurs as soon as a value from the
`full range is selected.
`
`SUMMARY
`
`Particular embodiments provide an improved capacitive
`position sensor for an electrical appliance in which a desired
`parameter value can be more efficiently and accurately
`selected.
`Particular embodiments provide a capacitive position sen-
`sor for detecting a position of an object comprising: a sensing
`
`7
`
`

`

`US 8,432,173 B2
`
`3
`element comprising a sensing path; at least one terminal
`connected to the sensing element; at least one sensing channel
`connected to the at least one terminal in which the sensing
`channel is operable to generate a signal indicative of capaci-
`tance between the terminal and a system ground; means to
`determine a position of an obj ect on the sensing element; and
`means to further refine the position ofthe object correspond-
`ing to a value in a parameter range of values.
`Particular embodiments provide a capacitive position sen-
`sor for setting a parameter or function to a desired value in a
`range of parameter or function values by determining the
`position of an object on a capacitive position sensor, the
`capacitive position sensor comprising: a sensing element
`comprising a sensing path; at least one terminal connected to
`the sensing element; at least one sensing channel connected to
`the at least one terminal in which the sensing channel is
`operable to generate a signal
`indicative of capacitance
`between the terminal and a system ground; means to deter-
`mine a position of an object on the sensing element; means to
`further refine the position of the object corresponding to a
`value in the range of parameter or function values; and a
`processor operable to interpret and process the signal to deter-
`mine the approximate position of an object on the sensing
`path, the processorbeing configured to provide a first mode of
`the capacitive position sensor in which the range ofparameter
`or function values is mapped onto the sensing path and in
`which the parameter or function can be set to approximately
`the desired value by a touch ofthe sensing path at a first point,
`and a second mode in which displacement of an object on the
`sensing element adjusts the parameter or function from the
`value initially set in the first mode, wherein the processor is
`configured to switch from the first mode to the second mode
`responsive to capacitive coupling caused by moving displace-
`ment of an object along the sensing path in relation to the first
`point of touch.
`Particular embodiments provide a method for determining
`the position of an object on a capacitive position sensor as
`hereinbefore defined, the method comprising bringing an
`object into proximity with the sensing element so as to deter-
`mine a position of the object, initiating a change in mode of
`the sensor to respond to capacitive coupling caused by mov-
`ing displacement of an object on the sensor element, displac-
`ing an object on the sensing element to select a value in a
`parameter range of values, and processing the signal to deter-
`mine the selected parameter value.
`Particular embodiments provide a method for setting a
`parameter or function to a desired value in a range of param-
`eter or function values by determining the position of an
`object on a capacitive position sensor, the capacitive position
`sensor comprising: a sensing element comprising a sensing
`path; at least one terminal connected to the sensing element;
`at least one sensing channel connected to the at least one
`terminal in which the sensing channel is operable to generate
`a signal indicative of capacitance between the terminal and a
`system ground; means to determine a position of an object on
`the sensing element; and means to further refine the position
`of the object corresponding to a value in the range of param-
`eter or function values, the method comprising: in a first mode
`ofthe capacitive position sensor in which the range ofparam-
`eter or function values is mapped onto the sensing path bring-
`ing an object into proximity with the sensing element at a first
`point so as to determine a position of the object and thereby
`initially set the parameter or function to approximately the
`desired value; initiating a change in mode of the sensor from
`the first mode to a second mode responsive to capacitive
`coupling caused by moving displacement of the object along
`the sensing path in relation to the first point of touch of the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`
`obj ect on the sensing element; in the second mode displacing
`the object on the sensing element to adjust the parameter or
`function from the value initially set to the desired value; and
`processing the signal to determine the selected parameter or
`function value.
`
`In particular embodiments, the capacitive sensor may work
`in a first mode and a second mode. In a first mode, a signal
`may be generated which is indicative of capacitive coupling
`of an object, for example a user’s finger, with the sensing
`element. The signal generated in the first mode may provide
`an approximate position of an object in relation to a desired
`parameter value the user wishes to select. A processor may be
`provided to interpret and process the signal to determine the
`approximate position of an object on the sensing element. In
`the first mode of operation, the capacitive sensor may gener-
`ate a signal indicative of capacitive coupling caused by bring-
`ing an object into proximity with a desired location on the
`sensor or by moving displacement of the object in proximity
`with the sensing element.
`In particular embodiments, the capacitive sensor may enter
`a second mode of operation if moving displacement of the
`object in proximity with the sensing element during a first
`mode of operation exceeds a minimum threshold value. For
`example, for a sensing element in the form of a rotary capaci-
`tive sensor, if a user displaces an object in proximity with the
`sensing element during a first mode of operation by a mini-
`mum threshold angle in relation to a first point of touch ofthe
`object on the sensing element, the capacitive sensor may
`switch into a second mode of operation. The minimum
`threshold angle may be determined by an algorithm pro-
`grammed into a microcontroller and the threshold angle may
`be set at different values depending on the sensitivity required
`and the parameter which is being adjusted. In one embodi-
`ment, the threshold angle may be set at 20 degrees before the
`capacitive sensor switches from the first mode to the second
`mode of operation. An approximate parameter value may be
`obtained in the first mode and in the second mode a desired
`
`parameter value may be selected.
`In the second mode of operation, an object may be dis-
`placed in proximity with the sensing element by a pre-deter-
`mined threshold value, for example 20 degrees, to effect an
`incremental change in the parameter value thereby allowing a
`desired specific parameter value to be selected. Advanta-
`geously, a capacitive sensor of particular embodiments oper-
`ating in a first mode may allow a parameter value to be
`selected (which may be the desired value, or near to the
`desired value, the user wishes to select) and in a second mode
`the sensor may effect an incremental increase or decrease of
`the parameter value selected in the first mode. In the second
`mode, a parameter value may be increased or decreased by a
`pre-determined amount, for example :1 unit, :5 units, or :10
`units, based on the number of times an object is displaced on
`the sensing element exceeding a pre-determined threshold
`value. Therefore, the threshold value may correspond to an
`increase or decrease of the parameter value by, say, :1 unit,
`and each time the threshold value is reached (11 times) the
`parameter value will increase or decrease by :1 (n times :1).
`In particular embodiments, the capacitive sensor may enter
`a second mode of operation by effectively “zooming-in” on a
`narrower range of parameter values, compared to the param-
`eter range displayed in the first mode, so that a user may
`accurately select a desired parameter value. The narrower
`range ofparameter values shown during the second mode will
`be determined by the parameter value selected in the first
`mode, for example plus and minus 10 units from the value
`selected in the first mode. In the second mode of operation, an
`
`8
`
`

`

`US 8,432,173 B2
`
`5
`object may be displaced along the sensing element so as to
`select the desired parameter value.
`The processor for determining the position of an object in
`proximity with the sensing element in a first mode of opera-
`tion may be operable for also determining the position of an
`object in proximity with the sensing element in a second
`mode of operation.
`Inparticular embodiments, the capacitive sensor may func-
`tion in a first mode of operation in which an approximate
`parameter value may be selected followed by a second mode
`of operation in which a specific parameter value may be
`selected. The range of parameter values associated with the
`capacitive sensor (i.e. the resolution) may determine whether
`a desired parameter value can be selected in the first mode of
`operation. The second mode of operation will allow a desired
`parameter value to be accurately selected, for example, either
`by zooming-in on a narrower range of parameter values
`around the parameter value selected in the first mode and
`displacing an object in proximity with the sensing element to
`select the desired value, or, by displacing an object in prox-
`imity with the sensing element to exceed a predetermined
`threshold value in order to change the parameter value
`selected from the first mode by one or more increments. The
`number of times the threshold value is exceeded may deter-
`mine the number of times the parameter value is increased or
`decreased.
`
`A capacitive sensor of particular embodiments may be
`incorporated into a control panel of an electronic appliance or
`gadget, for example a cooking oven, microwave oven, televi-
`sion, washing machine, MP3 player, mobile phone, or other
`multimedia device. A wide range of parameters or functions
`may be controlled by the capacitive sensor of particular
`embodiments, dependent on the type of electronic appliance
`in which the capacitive sensor is incorporated, for example,
`temperature, volume, contrast, brightness, or frequency. The
`parameter or function to be controlled may be selected prior
`to use of the capacitive sensor.
`Advantageously, the sensor has a higher degree of resolu-
`tion in the second mode allowing a user to move their finger
`in proximity with the sensing element to select a specific
`parameter value. If the sensing element is in the form of a
`closed loop, a user may be able to scroll clockwise or anti-
`clockwise around the sensing element to select the desired
`value. In the second mode for example, a 20 degree rotation
`may be equivalent to changing a parameter value by 1 unit.
`The amount of rotation required by an object on the sensing
`element to cause an incremental change in a parameter value
`may be varied dependent on the parameter or function being
`controlled. Control circuitry or a program-controlled micro-
`processor may be used to control the degree of rotation
`required to cause a change in a parameter value.
`In particular embodiments, the sensing element is arcuate
`in shape. In particular embodiments, the sensing element is in
`the form ofa closed loop foruse in a rotary capacitive position
`sensor. In a rotary capacitive position sensor embodiment, an
`object may be moved along the sensing element of the sensor
`for a plurality of revolutions and the distance moved by the
`object may determine the output signal which is generated by
`the sensing channel(s).
`In the first mode of operation of the capacitive sensor,
`capacitive coupling of an object in proximity with a sensing
`element may be detected to give an approximate position in
`relation to a range of values for a given parameter. If a user
`wishes to obtain different position data, the object may be
`removed from proximity with the sensing element and then
`brought into proximity with the said sensing element again. In
`other words, a user may initiate the first mode of the sensor
`
`6
`again simply by retouching the sensing element. When the
`second mode of operation is initiated, a user may scroll the
`sensing element to select a specific value of a certain param-
`eter. An output signal may be generated indicative of a spe-
`cific parameter value when an object ceases displacement at a
`certain position on the sensing element. In an embodiment, if
`a user releases touch from the sensing element in a second
`mode and retouches the sensing element then the first mode of
`operation may be activated again.
`In particular embodiments, the capacitive position sensor
`may further comprise one or more discrete sensing areas in
`the centre region of a rotary sensing element. If the sensing
`areas in the centre region ofthe sensing element sense capaci-
`tive coupling to an object, any signal produced from the
`sensing element is reduced or “locked out” using the Adj acent
`Key SuppressionTM technology described in the applicant’s
`earlier U.S. Pat. No. 6,993,607 and U.S. Patent Application
`Publication No. 2006/0192690, both incorporated herein by
`reference. Any output signal from the rotary sensing element
`caused by capacitive coupling with an object may also lock
`out a signal from the central sensing areas. The sensing ele-
`ment may be embodied by a single resistor, for example it
`may comprise a resistive material deposited on a substrate to
`form a continuous pattern. This provides for an easy-to-fab-
`ricate resistive sensing element which can be deposited on the
`substrate in any one of a range of patterns. Alternatively, the
`sensing element may be made from a plurality of discrete
`resistors. The discrete resistors may be alternately connected
`in series with a plurality of conducting sense plates, the sense
`plates providing for increased capacitive coupling between
`the object and the resistive sensing element. This provides for
`a resistive sensing element which can be fabricated from
`widely available off-the-shelf items. The disclosure of
`WO2005/019766 is incorporated herein by reference as an
`example of the capacitance measurement circuitry which
`may be used. Alternatively, a resistorless sensing element
`similar to that described in U.S. Pat. No. 4,264,903 may be
`used to form the capacitive sensor ofparticular embodiments.
`The resistive sensing element may have a substantially
`constant resistance per unit length. This provides for a capaci-
`tive position sensor having a simple uniform response. Where
`greater positional resolution is required or when employing a
`relatively long resistive sensing element, the resistive sensing
`element may include a plurality of terminals.
`The object to be detected may be a pointer, for example a
`finger or a stylus, which can be freely positioned by a user.
`Alternatively, the object may be a wiper held in proximity to
`the resistive sensing element, the position of the wiper along
`the resistive sensing element being detected by the capacitive
`position sensor. The position of the wiper may be adjusted by
`a user, for example by turning a rotary knob, or may be
`coupled to a shaft driven by connected equipment such that
`the capacitive position sensor can act as an encoder.
`Particular embodiments provide a sensor having high reli-
`ability, a sealed surface,
`low power consumption, simple
`design, ease of fabrication, and the ability to operate using
`off-the-shelf logic or microcontrollers.
`In U.S. Pat. No. 6,466,036, the applicant teaches a capaci-
`tive field sensor employing a single coupling plate to detect
`change in capacitance to ground. This apparatus comprises a
`circuit employing repetitive charge-then-transfer or charge-
`plus-transfer cycles using common integrated CMOS push-
`pull driver circuitry. This technology fom1s the basis of par-
`ticular embodiments and is incorporated by reference herein.
`Some definitions are now made. “Element” refers to the
`physical electrical sensing element made of conductive sub-
`stances. “Electrode” refers to one of the galvanic connection
`
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`US 8,432,173 B2
`
`7
`points made to the element to connect it to suitable driver/
`sensor electronics. The terms “object” and “finger” are used
`synonymously in reference to either an inanimate object such
`as a wiper or pointer or stylus, or alternatively a human finger
`or other appendage, any of whose presence adjacent the ele-
`ment will create a localized capacitive coupling from a region
`of the element back to a circuit reference Via any circuitous
`path, whether galvanically or non-galvanically. The term
`“touch” includes either physical contact between an object
`and the element, or, proximity in free space between object
`and element, or physical contact between object and a dielec-
`tric (such as glass) existing between object and element, or,
`proximity in free space including an intervening layer of
`dielectric existing between object and element. Hereinafter
`the terms “circle” or “circular” refer to any ellipsoid, trap-
`ezoid, or other closed loop of arbitrary size and outline shape
`having an open middle section.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 shows a control panel of an apparatus embodying a
`rotary capacitive sensor, the sensor being used in a first mode
`of operation.
`FIG. 2A shows the capacitive sensor of FIG. 1 being used
`in a second mode of operation, with the user scrolling around
`the sensor in an anticlockwise direction.
`
`FIG. 2B shows the capacitive sensor of FIG. 1 being used
`in a second mode of operation, with the user scrolling around
`the sensor in a clockwise direction.
`
`FIG. 3 shows a control panel of an apparatus according to
`another embodiment, in which a rotary capacitive sensor is
`being used in a first mode of operation.
`FIG. 4 shows the capacitive sensor of FIG. 3 being used in
`a second mode of operation.
`
`
`
`DESCRIPTION OF EXAMPLE EMBODIMENTS
`
`FIG. 1 illustrates part of a control panel 50 having a capaci-
`tive sensor 60 and a digital readout display 70. The control
`panel 50 may be incorporated into an electronic appliance
`such as a cooking oven, microwave oven, washing machine,
`fridge freezer, television, MP3 player, mobile telephone or
`the like. The parameter or function to be controlled by the
`capacitive sensor will depend on the type of electrical appli-
`ance in which the capacitive sensor is incorporated. Param-
`eters like volume, temperature, operating program, bright-
`ness, contrast are some examples of functions that may be
`controlled by the capacitive sensor of particular embodi-
`ments. In particular embodiments, the parameter to be con-
`trolled may be chosen from a predetermined list of param-
`eters so that a user may advantageously adjust different
`parameters on an electrical appliance or apparatus. The
`capacitive sensor 60 shown in FIG. 1 is set to control cooking
`temperature of a microwave or cooking oven.
`The capacitive sensor 60 comprises a rotary sensing ele-
`ment 100 for detecting capacitive coupling with an object,
`typically an operator’ s finger. A Liquid Crystal Display 75 (or
`other known display) is formed in the control panel 50 to
`illuminate the temperature scale around the sensing element.
`The temperature scale ranges from 0 to 300 degrees Centi-
`grade. The capacitive sensor 60 is shown in a first mode of
`operation in which a user’s finger is used to select a cooking
`temperature. A user’s finger 80 is shown in proximity with a
`portion of the sensing element 100 corresponding to a tem-
`perature of 175 degrees Centigrade (° C.) which is displayed
`on the digital readout display 70. The selected temperature of
`175° C. may be the desired temperature required by the user,
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`but in most cases the temperature selected in the first mode of
`operation will indicate a temperature near to the actual tem-
`perature required by the user. A user may re-touch the sensing
`element 100 of the sensor to reactivate the first mode of
`
`operation and select a different temperature. The resolution of
`the sensor may determine how close the temperature selected
`in the first mode is to the desired temperature sought by the
`user.
`
`Turning now to FIGS. 2A and 2B, the capacitive sensor 60
`is shown in a second mode of operation. The capacitive sensor
`automatically enters the second mode of operation after a
`temperature has been selected in the first mode of operation.
`In the second mode, a user is able to increase or decrease the
`temperature selected in the first mode by a pre-determined
`increment. Changing the te

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