Capacitive touch control and display
First Claim
1. A capacitive control assembly activatable by positional contact by a member having an impedance to electrical ground potential, comprising:
- a solid panel having front and rear surfaces;
a plurality (M) of electrodes, where M is an integer greater than one, disposed along a preselected geometric curve and fabricated upon one of said panel surfaces;
each of said M electrodes insulated from the others of said electrodes;
means coupled to each electrode for providing one of a like plurality (M) of signals thereto;
each signal having the same frequency as all other signals and having a phase differing by (360/M) degrees from the phases of the signals coupled to adjacent electrodes;
said signal providing means including first means for producing a train of pulse signals at a frequency F,second means receiving said train of pulse signals for producing a plurality (M) of square wave outputs each having a frequency (F'"'"') equal to (F/N), where N is an integer greater than one, and each successive one of said plurality of square waves having a phase difference of (360/M) degrees with respect to the next preceding and next subsequent square wave;
each successive square wave output of said second means being coupled to a successive one of said plurality of electrodes, commencing at a particular one of said electrodes associated with a reference point; and
means connected to each of said plurality of electrodes for recognizing the phase of the summation of all of said square wave outputs after coupling to said electrodes to determine the location of said contact position of said member on said panel above said electrodes, with respect to said reference point;
said recognizing means including third means coupled to said electrodes for recovering from said electrodes a periodic waveform having a frequency equal to the frequency (F'"'"') of said square wave outputs and crossing a predetermined level at a time, after a predetermined transition of the square wave coupled to the electrode associated with said reference point, related to the position of said member contact with respect to said reference point; and
fourth means coupled to said first and third means for counting the pulses from said first means during the time interval between said predetermined transition and said predetermined level crossing to obtain a digital representation of the position of said member contact with respect to said reference point.
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Accused Products
Abstract
A control for use upon a solid panel, devoid of control shaft apertures, allows data entry by rotational positioning of a human member, such as one'"'"'s finger, about a pattern of a plurality of interdigitated electrodes formed upon an interior surface of the panel. The position of the member varies the capacitance between adjacent ones of the electrodes, with position-decoding electronics energizing successive ones of the plurality of electrodes with successive phases of a master signal and recovering information relating the phase of the signal returned from the control to the position of the member. A light-emitting display may be positioned behind the panel to indicate the index of the control knob by a variable-length circular bar of light, a digitized display and the like.
309 Citations
14 Claims
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1. A capacitive control assembly activatable by positional contact by a member having an impedance to electrical ground potential, comprising:
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a solid panel having front and rear surfaces; a plurality (M) of electrodes, where M is an integer greater than one, disposed along a preselected geometric curve and fabricated upon one of said panel surfaces;
each of said M electrodes insulated from the others of said electrodes;means coupled to each electrode for providing one of a like plurality (M) of signals thereto;
each signal having the same frequency as all other signals and having a phase differing by (360/M) degrees from the phases of the signals coupled to adjacent electrodes;
said signal providing means including first means for producing a train of pulse signals at a frequency F,second means receiving said train of pulse signals for producing a plurality (M) of square wave outputs each having a frequency (F'"'"') equal to (F/N), where N is an integer greater than one, and each successive one of said plurality of square waves having a phase difference of (360/M) degrees with respect to the next preceding and next subsequent square wave;
each successive square wave output of said second means being coupled to a successive one of said plurality of electrodes, commencing at a particular one of said electrodes associated with a reference point; andmeans connected to each of said plurality of electrodes for recognizing the phase of the summation of all of said square wave outputs after coupling to said electrodes to determine the location of said contact position of said member on said panel above said electrodes, with respect to said reference point;
said recognizing means including third means coupled to said electrodes for recovering from said electrodes a periodic waveform having a frequency equal to the frequency (F'"'"') of said square wave outputs and crossing a predetermined level at a time, after a predetermined transition of the square wave coupled to the electrode associated with said reference point, related to the position of said member contact with respect to said reference point; andfourth means coupled to said first and third means for counting the pulses from said first means during the time interval between said predetermined transition and said predetermined level crossing to obtain a digital representation of the position of said member contact with respect to said reference point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification