US005796183A
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`[11] Patent Number:
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`[451 Date of Patent:
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`5,796,183
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`Aug. 18, 1998
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`Ulllted States Patent
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`Hourmand
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`[191
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`[S4] CAPACITIVE RESPONSIVE ELECTRONIC
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`sw[TCH[N(; C[RCU[']‘
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`[75]
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`Inventor: Byron Hourmand. Hersey. Mich.
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`[73] Assignee: Nartron Corporation. Reed City.
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`Mich‘
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`[21] Appl. No.: 601,268
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`1811- 31» 1995
`F11ed=
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`Int. Cl.‘ ..................................................... H0111 35/00
`[51]
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`[52] U.S. C1.
`.......................... 307/116: 361/181; 307/125;
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`307/139
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`[58] Field of Search ................................... .. 307/112. 113.
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`307/116, 125, 139. 140. 157; 361/181
`References Cited
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`[56]
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`U_S, PATENT DOCUMENTS
`
`
`
`
`4.303/443
`
`4,323,829
`
`4,352,141
`
`
`43601737
`4,374,381
`
`4,476,463
`
`4 503294
`
`4.731543
`
`4,758,735
`
`4,831,279
`
`4,910,504
`
`4,939,382
`
`
`
`5,065,393
`
`5,087,825
`
`5,208,516
`
`
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`
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`5,386,219
`5,453,644
`5,572,205
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`,
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`363/181
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`200/S A
`
`
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`12/1931 Tucker 6131- ~
`
`
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`4/1982 Wimey et al.
`.
`
`
`
`9/1982 Kent
`
`
`
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`“/1932 Le°P°1d -
`2/1983 Ng el al.
`.
`
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`10/1984 Ng el al.
`.
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`
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`3/1985 Matsumm
`
`3/1988 Ingraham.
`
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`7/1988 Ingraham.
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`5/1989 Ingraham.
`
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`3/1990 Eriksson,
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`7/1990 Gruodis.
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`Z133‘: ;,;;j""""""""""""""""""""" “"623
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`11/1991 M1113; e1a1_ _
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`2/1992 Ingraham,
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`5/1993 Saidian.
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`gleth etalr .
`rton .....................................
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`1/1995 Greamas et a1.
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`9/1995 Yap et a1.
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`11/1996 Caldwell et al.
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`307/326
`
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`.
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`......................... 341/33
`
`
`
`
`
`
`3,549,909 12/1970 Adelson et al,
`.
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`3,641,410
`2/1972 Vogelsberg .
`
`
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`
`
`3,651,391
`3/1972 Vogelsbfifg -
`3,666,988
`5/1972 Bellis .
`
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`3,798,370
`3/1974 Hurst.
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`4/1975 Larson .................................... 307/116
`3,879,618
`
`
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`3,899,713
`8/1975 Balkan et al.
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`10/1975 Hutstet al.
`3,911,215
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`3,919,596
`11/1975 Bellis .
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`3.965.465
`6/1976 Alexander -
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`10/1976 G0“ 3131‘ -
`3v934=757
`4,0l6,453
`4/1977 Moennig.
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`4,031,408
`6/1977 Holz.
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`1/1978 Talmage et al.
`4,071,689
`7/1978 Stone.
`4,101,805
`
`
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`4,119,864 10/1973 peuizjo ,
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`4,152,529
`5/1979 Raupp _
`5/1979 senk _
`4,159,473
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`7/1980 Wem .
`4,210,822
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`4.2111959
`7/1930 DeaVeI1p0I1¢t 31-
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`7/1930 C‘?'“““'
`~
`42131061
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`47220315
`9/1930 G'bS°“ °‘ "1'
`'
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`12/1980 Wald
`,
`4 37,421
`"1981 Chianl-2"‘
`4346533
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`3/1931 Besson .
`4257,117
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`4/1931 Wern .
`4,264,831
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`9/1981 Wern .
`4,289,972
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`9/1981 McLaughlin .
`4,289,980
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`-
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`Primary Examiner—WilliaIn M. Shoop. Jr.
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`Assistant Exam/‘ner—Jonathan Kaplan
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`Attorney, Agent, or Firm—Price. Heneveld. Cooper. DeWitt
`& Litton
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`[57]
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`ABSTRACT
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`A capacitive responsive electronic switching circuit com-
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`prises an oscillator providing a periodic output signal having
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`a frequency of 50 kHz or greater. an input touch terminal
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`defining an area for an operator provide an input by prox-
`imity and touch. and a detector circuit coupled to the
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`oscillator for receiving the periodic output signal from the
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`oscillator. and coupled to the input touch terminal. The
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`detector circuit being responsive to signals from the oscil-
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`later and the presence of an operator s body capacitance to
`ground coupled to the touch terminal when in proximity or
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`touched by an operator to provide a control output signal.
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`Preferably, the oscillator provides a periodic output signal
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`having a frequency of 800 kHz or greater. An array of touch
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`terminals may be provided in close proximity due to the
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`reduction 111 crosstalk that may result from contaminants by
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`lltlllzlllg an oscillator outputting a slgnal having a frequency
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`01° 50 KHZ 0? greater-
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`32 Claims, 13 Drawing Sheets
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`~
`§
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`* VOLTAGE
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`‘"7’
`REGULATOR
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`192
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`Page 1 of 41
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`SAMSUNG EXHIBIT 1001
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`SAMSUNG EXHIBIT 1001
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`Page 1 of 41
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`U.S. Patent
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`Aug. 13, 1993
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`Sheet 1 of 13
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`5,796,183
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`Fig. 1
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`Aug. 13, 1998
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`5,796,183
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`F39 - 3
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`Fig. 8
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`U.S. Patent
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`Aug. 18, 1993
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`Sheet 3 of 13
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`5,796,183
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`—-ZGMWJ
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`FREQUENCY
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`---'---ZGMAX
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`FREQUENCY
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`Fig. 3A
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`U.S. Patent
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`Aug. 13, 1993
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`Sheet 5 of 13
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`Aug. 13, 1993
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`Sheet 6 of 13
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`5,796,183
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`S/N VS. BODY CAPACITANCE
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`U.S. Patent
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`Aug 18, 1998
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`Sheet 7 of 13
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`Sheet 8 of 13
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`U.S. Patent
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`Aug. 18, 1993
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`Sheet 9 of 13
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`5,796,183
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`Aug. 13, 1998
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`1
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`CAPACITIVE RESPONSIVE ELECTRONIC
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`SWITCHING CIRCUIT
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`lative Trauma Disorders by adopting ergonomic designs that
`more favorably control the range. angle. number. and force
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`of motions required of an operator as well as the number of
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`the operator’s muscle groups involved in the required
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`motions. Prosthetics and tests are used as well to provide
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`strain relief for the operator’s muscles. joints. and tendons.
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`In mechanical switches. the force required to actuate the
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`frictional forces between moving parts. However. reducing
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`such forces makes such switches more vulnerable to failure.
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`For instance. weaker springs typically lower the pressure
`between contacts in a “make” condition. This lower contact
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`pressure increases the resistance in the switch which can
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`lead to fatal heating in the switch and/or loss of voltage
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`applied to the switched load. Reducing frictional forces in
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`the switch by increasing the use of lubricants is undesirable
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`because the lubricants can migrate and contaminate the
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`contact surfaces. A switch designer may also reduce friction
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`by providing looser fits between moving parts. However.
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`looser fits tend to increase wear and contribute to earlier
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`switch failure. A designer can also reduce friction by using
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`higher quality. higher cost. surface finishes on the parts.
`Thus. as apparent from the foregoing description. measures
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`taken to reduce actuator force in mechanical switch parts
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`generally reduce the reliability and performance of the
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`switch and/or increase the cost of the switch.
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`In applications such as computer keyboards or appliance
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`controls. the electric load switched by a given switch can be
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`quite low in terms of current and/or voltage. In such cases
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`it is possible to use low force membrane switches such as
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`described in U.S. Pat. No. 4.503.294. Such switches can
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`relieve operator strain and are not as susceptible to arcing
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`problems because they switch small loads. However. the
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`flexible membrane remains susceptible to wear. corrosion.
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`and contamination. Although such switches require very low
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`actuation force. they are still mechanically based and thus
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`suffer from the same problems as any other mechanical
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`switch.
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`A more recent innovation is the development of “zero
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`force” touch switches. These switches have no moving parts
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`and no contact surfaces that directly switch loads. Rather.
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`these switches operate by detecting the operator’s touch and
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`then use solid state electronics to switch the loads or activate
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`mechanical relays or triacs to switch even larger loads.
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`Approaches include optical proximity or motion detectors to
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`detect the presence or motion of a body part such as in the
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`automatic controls used in urinals in some public rest rooms
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`or as disclosed in U.S. Pat. No. 4.942.631. Although these
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`non-contact switches are by their very nature truly zao
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`force. they are not practical where a multiplicity of switches
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`are required in a small area such as a keyboard Among other
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`problems. these non-contact switches sufier from the com-
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`paratively high cost of electro-optics and from false detec-
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`tions when the operator’s hand or other body part uninten-
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`tionally comes close to the switch’s area of detection. Some
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`optical touch keyboards have been proposed. but none have
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`enjoyed commercial success due to performance and/or cost
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`considerations.
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`A further solution has been to detect the operator’s touch
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`via the electrical conductivity of the operator’s skin. Such a
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`system is described in U.S. Pat. No. 3.879.618. Problems
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`with this system result from variations in the electrical
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`conductivity of dilferent operators due to variations in sweat.
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`skin oils. or dryness. and from variable ambient conditions
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`such as humidity. A further problem arises in that the touch
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`surface of the switch that the operator touches mu st remain
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`clean enough to provide an electrical conductivity path to
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`BACKGROUND OF THE INVENTION
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`The present invention relates to an electrical circuit and
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`particularly a capacitive responsive electronic switching
`circuit used to make possible a “zero force” manual elec-
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`tronic switch.
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`Manual switches are well known in the art existing in the
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`familiar forms of the common toggle light switch. pull cord
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`switches. push button switches. and keyboard switches
`among others. The majority of such switches employ a
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`mechanical contact that “makes” and “breaks” the circuit to
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`be switched as the switch is moved to a closed or an open
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`condition.
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`Switches that operate by a mechanical contact have a
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`number of well known problems. First. mechanical move-
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`ments of components within any mechanism make those
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`components susceptible to wear. fatigue. and loosening. This
`is a progressive problem that occurs with use and leads to
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`eventual failure when a sulficient amount of movement has
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`occurred
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`Second. a sudden “make” or “ eak” between conductive
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`contacts typically produces an electrical are as the contacts
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`come into close proximity. This arcing action generates both
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`radio frequency emissions and high frequency noise on the
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`line that is switched.
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`Third. the separation between contacts that occurs on each
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`break. exposes the contact surfaces to corrosion and con-
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`tamination. A particular problem occurs when the arc asso-
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`ciated with a “make” or “break” occurs in an oxidizing
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`atmosphere. The heat of the arc in the presence of oxygen
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`facilitates the formation of oxides on the contact surfaces.
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`Once exposed. the contact surfaces of mechanical switches
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`are also vulnerable to contaminants. Water borne contami-
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`nants such as oils and salts can be a particular problem on
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`the contact surfaces of switches. Arelated problem occurs in
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`that the repeated arcing of mechanical contact can result in
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`a migration of contact materials away from the area of the
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`mechanical contact. Corrosion. contamination. and migra-
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`tion operating independently or in combination often lead to
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`eventual switch failure where the switch seizes in a closed
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`or opened condition.
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`An additional problem results from the mechanical force
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`required in operating a mechanical switch. This problem
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`occurs in systems where a human operator is required to
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`repetitively operate a given switch or a number of switches.
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`Such repetitive motions commonly occur in the operation of
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`electronic keyboards such as those used with computers and
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`in industrial switches such as used in forming and assembly
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`equipment among other applications. A common type of
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`industrial switch is the palm button seen in pressing and
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`insertion equipment. For safety purposes. the operator must
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`press the switch before an insertion or pressing can occur.
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`This ensures that the operators hand(s) is(are) on the button
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`(5) and not in the field of motion of the associated machinery.
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`It also ensures that the mechanical motion occurs at a desired
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`and controllable point in time. The difiiculty arises from the
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`motion and force required of the operator. In recent years. it
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`has been noted that repeated human motions can result in
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`debilitating and painful wear on joints and soft tissues
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`yielding arthritis like symptoms. Such repetitive motion may
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`result in swelling and cramping in muscle tissues associated
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`with conditions such as Carpal Tunnel Syndrome. Equip-
`ment designers combat these Repetitive Motion or Cumu-
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`20
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`25
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`30
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`35
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`Page 15 of4l
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`Page 15 of 41
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`

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`5.796.183
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`3
`the operator. Such surfaces can be susceptible to
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`contamination. corrosion. and/or a wearing away of the
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`conductive material. Also. these switches do not work if the
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`operator is wearing a glove. Safety considerations also arise
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`by virtue of the operators placing their body in electrical
`Contact with the switch electronics. A further problem arises
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`in that such systems are vulnerable to contact with materials
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`that are equally or more conductive than human skin. For
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`instance. water condensation can provide a conductive path
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`as good as that of an operator’s skin. resulting in a false
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`activation.
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`A common solution used to achieve a zero force touch
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`switch has been to make use of the capacitance of the human
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`operator. Such switches. which are hereinafter referred to as
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`capacitive touch switches. utilize one of at
`three
`least
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`different methodologies. The first method involves detecting
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`RF or other high frequency noise that a human operator can
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`capacitively couple to a touch terminal when the operator
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`makes contact such as is disclosed in US. Pat. No. 5.066.
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`898. One common source of noise is 60 Hz noise radiated
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`from commercial power lines. A drawback of this approach
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`is that radiated electrical noise can vary in intensity from
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`locale to locale and thereby cause variations in switch
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`sensitivity. In some cases. devices implemented using this
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`first method. rely on conductive contact between the opera-
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`tor and the touch terminal of the switch. As stated. such
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`surfaces are subject to contamination. corrosion. and wear
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`and will not work with gloved hands. An additional problem
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`can arise in the presence of moisture when multiple switches
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`are employed in a dense array such as a keyboard. In such
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`instances. the operator may touch one touch terminal. but
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`end up inadvertently activating others through the path of
`conduction caused by the moistLn'e contamination.
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`A second method for implementing capacitive touch
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`switches is to couple the capacitance of the operator into a
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`variable oscillator circuit that outputs a signal having a
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`frequency that varies with the capacitance seen at a touch
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`terminal. An example of such a system is described in U.S.
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`Pat. No. 5.235.217. Problems with such a system can arise
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`where conductive contact with the operator is required and
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`where the frequency change caused by a touch is close to the
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`frequency changes that would result from unintentionally
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`coming into contact with the touch terminal.
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`Another method for implementing capacitive touch
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`switches relies on the change in capacitive coupling between
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`a touch terminal and ground. Systems utilizing such a
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`method are described in U.S. Pat. No. 4.758.735 and U.S.
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`Pat. No. 5.087.825. With this methodology the detection
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`circuit consists of an oscillator (or AC line voltage
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`derivative) providing a signal to a touch terminal whose
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`voltage is then monitored by a detector. The touch terminal
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`is driven in electrical series with other components that
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`function in part as a charge pump. The touch of an operator
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`then provides a capacitive short to ground via the operator’s
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`own body capacitance that lowers the amplitude of oscillator
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`voltage seen at the touch terminal. Amajor advantage of this
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`methodology is that the operator need not come in conduc-
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`tive contact with the touch terminal but rather only in close
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`proximity to it. Afurther advantage arises in that the system
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`does not rely upon radiated emissions picked up by the
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`operator’s body which can vary with locale. but relies
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`instead upon the human body's capacitance. which can vary
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`over an acceptable range of 20 pF to 300 pF.
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`An additional consideration in using zero force switches
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`resides in the difficulties that arise in trying to employ dense
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`arrays of such switches. Touch switches that do not require
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`physical contact with the operator but rather rely on the
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`10
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`20
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`25
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`35
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`65
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`4
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`operator’s close proximity can result in unintended actua—
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`tions as an operator’s hand or other body part passes in close
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`proximity to the touch terminals. Above-mentioned U.S.
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`Pat. No. 5.087.825 employs conductive guard rings around
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`the conductive pad of each touch terminal in an effort to
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`decouple adjacent touch pads and prevent multiple actua-
`tions where only a single one is desired. In conjunction with
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`the guard rings. it is also possible to adjust the detection
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`sensitivity by adjusting the threshold voltage to which the
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`sensed voltage is compared. The sensitivity may be adjusted
`in this manner to a point where the operator’s body part. for
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`instance. a finger. has to entirely overlap a touch terminal
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`and come into contact with its dielectric facing plate before
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`actuation occurs. Although these methods (guard rings and
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`sensitivity adjustment) have gone a considerable way in
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`allowing touch switches to be spaced in comparatively close
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`proximity. a susceptibility to surface contamination remains
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`as a problem. Skin oils. water. and other contaminants can
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`form conductive films that overlay and capacitively couple
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`adjacent or multiple touch pads. An operator making contact
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`with the film can then couple multiple touch pads to his or
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`her body capacitance and it’s capacitive coupling to ground.
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`This can result in multiple actuations where only one is
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`desired. Small touch terminals placed in close proximity by
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`necessity require sensitive detection circuits that in some
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`cases are preferably isolated from interference with the
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`associated load switching circuits that they activate.
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`As mentioned. in industrial controls. switches can be used
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`to control actuation time and to ensure that the operator’s
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`hand(s) or other body part(s) are out of the field of motion
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`of associated machinery. A common type of switch used in
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`this application is the palm button. The button is large
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`enough so that the operator can rapidly bring his or her hand
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`into contact with the button without having to lose the time
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`that would be taken in acquiring and lining up a finger with
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`a smaller switch. Zero force touch switches are also desir-
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`able in this application as Repetitive Motion or Cumulative
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`Trauma Disorders have been a problem with operator’s
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`utilizing palm buttons—especially those palm buttons that
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`must be actuated against a spring resistance. In this area
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`capacitive touch switches have also been employed. U.S.
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`Pat. No. 5.233.231 is an example of such an implementation.
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`Due to the proximity of machinery with the potential to
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`cause injury. false actuations are a particular liability in such
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`applications. Capacitive touch switches that exhibit vulner-
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`ability to radiated electromagnetic noise or that operate ofi
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`operator proximity have the potential to actuate when the
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`operator’s hand(s) is not at the desired location on the palm
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`button(s). In general. this is addressed by the use of redun-
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`dancies. In U.S. Pat. No. 5.233.231. a separate detector is
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`used to measure RF noise and disable the system to a safe
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`state if excessive RF noise is present. Other systems such as
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`UltraTouch vended by Pinnacle Systems. Inc. use redundant
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`sensing methodologies. In UltraTouch. both optical and
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`capacitive sensors are used and actuation occurs only when
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`both sensor types detect the operator’s hand at the desired
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`location. These implementations have a number of disad-
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`vantages. In the case of the RF noise detection system. the
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`system is unusable in the presence of RF noise. This forces
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`the user to employ a backup mechanical switch system or
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`accept the loss of function when RF noise is present. The
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`second system is less reliable and more expensive because
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`it requires two sensor systems to accomplish the same task.
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`i.e.. detect the operator. Such system may also suffer from
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`problems inherent in any optical system. namely. suscepti-
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`bility to blockages in the optical path and the need to achieve
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`and maintain specific optical alignments. A further problem
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`Page 16 of41
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`Page 16 of 41
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`5.796.183
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`6
`In a first preferred embodiment the circuit olfers enhanced
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`detection sensitivity to allow reliable operation with small
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`(finger size)
`touch pads. Susceptibility to variations in
`supply voltage and noise are minimized by use of a floating
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`common and supply that follow the oscillator signal to
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`power the detection circuit. The enhanced sensitivity allows
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`the use of a 26V or lower amplitude oscillator signal applied
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`to the touch terminal and detection circuit. This lower
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`voltage (as compared to the device of U.S. Pat. No. 4.758.
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`735) obviates the need for expensive UL listed higher
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`voltage construction measures and testing to handle what
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`would otherwise be large enough voltages to cause safety
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`concerns. A further advantage of the present invention is
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`seen in the manner in which the touch terminal detection
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`circuit is interfaced to the touch terminals and to external
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`control systems. A dedicated microprocessor referenced to
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`the floating supply and floating common of the detection
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`circuit maybe used to cost effectively multiplex a number of
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`touch terminal detection circuits and multiplex the associ-
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`ated touch terminal output signals over a two line optical bus
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`to a dedicated microprocessor referenced to a fixed supply
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`and ground. An additional advantage of the microprocessor
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`is an expanded ability to detect faults. i.e. a pad that is
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`touched for an excessive amount of time that is known a
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`priori to be an unlikely mode of operation or two or more
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`pads touched at the same time or in an improper order.
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`Additionally. the microprocessor can be used to distinguish
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`desired multiple pad touches in simultaneous or sequential
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`modes. i.e. two or more switches touched in a given order
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`within a given amount of time. The microprocessor can be
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`used to perform system diagnostics as well. The micropro-
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`cessor also allows the use of visual indicators such as LEDs
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`or annunciators such as a bell or tone generator to confirm
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`the actuation of a given touch switch or switches. This is
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`particularly useful in cases where a sequence of actuations
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`is required before an action occurs. The feedback to the
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`operator provided by a visual or audio indicator activated by
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`the microprocessor in response to intermediate touches in a
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`required sequence can minimize time lost and/or frustration
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`on the part of the operator due to failed actuations from
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`partial touches or wrong actuations from touching the wrong
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`pad in a given required sequence or combination of touches.
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`The second microprocessor may be used to communicate
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`with the user’s control system. Additional features include a
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`“sleep mode” to minimize power consumption during peri-
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`ods of non-use or power brown outs. and redundant control
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`circuits to facilitate “fail
`to safe” operation. Another
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`improvement is ofl’ered in a means to move much of the cost
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`of the system into simplified custom integrated circuits that
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`allow ease of sensitivity adjustment and assembly.
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`In a second preferred embodiment. an improved palm
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`button is featured. Through the use of a dielectric cover. a
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`large metallic touch terminal can be used that difierentiates
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`between the touch of a finger or partial touch and the full
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`touch of a palm. In this way the system avoids false triggers
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`due to inadvertent finger touches or brushing contact with
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`the palm prior or after an intended touch. The second
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`embodiment also features redundant control circuits to
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`facilitate “fail to safe” operation.
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`To achieve these and other advantages. and in accordance
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`with the purpose of the invention as embodied and described
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`herein. the capacitive responsive electronic switching circuit
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`comprises an oscillato