I 1111111111111111 11111 111111111111111 IIIII 111111111111111 111111111111111111
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`US0057607 l 5A
`5,760,715
`
`United States Patent
`c191
`1111 Patent Number:
`Jun.2, 1998
`Senk et al.
`[45]Date of Patent:
`
`
`
`[54]PADLESS TOUCH SENSOR
`
`2/1989 Evans ........................................ 178/19
`
`4,806,809
`
`5/1990 Antikidis et al .......................... 341/33
`4,924,222
`
`9/1990 Kohno et al ....................... 340/825.69
`4,954,820
`[75]Inventors: Miro Senk. St-Laurent; Pierre Repper.
`
`
`
`
`
`4/1991 Hollaway ................................ 307/116
`5,012,124
`
`Chateauguay, both of Canada
`
`
`3/1993 Edwards .................................... 341/20
`5,194,862
`
`
`
`12/1993 Gaultier et al ............................ 341/33
`
`5,270,710
`[73] Assignee:
`Inc .. St-Laurent.
`Pressenk Instruments
`
`
`10/1995 Huang et al .............................. 178/20
`5,457,289
`Canada
`
`
`2/1996 Miller et al ............................... 178/18
`5,495,077
`5,508,700
`
`
`4/1996 Taylor et al .............................. 341/33
`
`
`6/1996 Ono et al ................................ 364n09
`5,526,294
`
`
`6/1996 Arnold ...................................... 380/25
`5,526,428
`
`
`
`7/1996 Laing et al ........................ 340/825.34
`5,534,857
`
`11/1996 Davis et al. .............................. 380/24
`5,577,121
`
`[21] Appl. No.: 843,3(i5
`
`[22]Filed:Apr. 15, 1997
`
`
`
`
`
`Related U.S. Application Data
`
`[56]
`
`
`
`References Cited
`
`Zimmerman
`Primary Examiner-Brian
`[60]Provisional application No. 60/014,638 Apr. 15, 19%.
`
`
`
`Edwards. Jr.
`
`Assistant Examiner-Timothy
`6 ..........................
`
`
`
`Gould. Smith Edell. Attome.» Agent, or Finn-Merchant.
`H03K 17/94; H03M 11/00
`[51] Int. Cl.
`Welter & Schmidt
`[52]U.S. CI .............................
`341/33; 200/600; 345/173;
`
`
`
`345/174; 341/26; 341/34; 361/181; 178/18
`[57]
`ABSTRACT
`
`............................. 200/600; 345/173.
`[58]Field of Search
`The padless touch sensor is used for detecting a touch at a
`
`
`
`
`
`345/174, 179; 341/26. 33. 34; 307/116.
`
`
`
`
`
`sensing location onto a dielectric element by a user coupled
`
`109. 98, 99; 361/181; 178/17 C. 17 D.
`
`
`
`to earth. Toe sensor comprises a conductive plate attached
`18
`
`
`under the dielectric element and in registry with the sensing
`
`
`
`location. A predetermined potential is applied on the con­
`
`
`
`
`
`ductive plate. Simultaneously. test pulses are produced into
`
`
`earth. When the user touches the dielectric element at the
`
`
`
`
`sensing location. a potential variation in the conductive plate
`
`
`4/1977 Weckenmann et al ................. 361/181
`4,016,490
`
`
`is produced during a test pulse due to a capacitive circuit
`
`
`4,175,239 11/1979 Sandler ................................... 361/181
`4,221,975
`
`
`
`9/1980 Ledniczki et al ....................... 307/116
`
`
`formed between earth. the user and the sensor. No deposition
`
`
`
`
`4,257,117 3/1981 Besson ...................................... 368/69
`
`
`
`of conductive pads on the dielectric element or other special
`
`
`
`3/1982 Ledniczki et al ....................... 307/116
`4,321,479
`
`
`
`
`processes are required. Foreign matter or objects placed
`
`
`
`4,353,552 10/1982 Pepper, Jr ................................. 463/37
`
`
`
`directly on top of the dielectric element will not erroneously
`
`
`
`
`4,550,310 10/1985 Yamaguchi et al ..................... 340/365
`produce a touch condition.
`
`
`
`
`4,556,871 12/1985 Yoshikawa et al ..................... 340/365
`
`
`4,561,002 12/1985 Chiu ........................................ 340/365
`
`
`3/1987 Ganesan et al ......................... 340/365
`4,651,133
`
`18 Claims, 10 Drawing Sheets
`
`U.S. PATENT DOCUMENTS
`
`24
`
`C9
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`(/ ,------! I
`i,•
`22 ,{
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`(-· /
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`-
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`1/1 Rl
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`• 24 V
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`EARTH
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`V
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`10/
`
`Ql
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`Yp
`
`Q2
`
`Ra
`
`CIRCUIT -=
`GROUND
`(0 1/0LT)
`
`Samsung EX1010 Page 1
`
`

`

`U.S. Patent
`Jun. 2, 1998 Sheet 1
`of 10
`
`5,760,715
`
`I'
`
`,
`
`CB
`
`EARTH
`
`1
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`1
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`C1
`C 2
`1 1
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`I I
`I
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`I I
`
`TEST SIGNAL
`
`EARTH
`
`.___ ____ TO CIR CU rT
`
`Fl G. 1
`
`{ PRIOR ART)
`
`C1
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`C 2
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`T �'---•►TO CIRCUIT
`
`JC
`
`E ARTH
`
`B
`
`EARTH
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`Fl G. 2
`
`( PRIOR ART)
`
`Samsung EX1010 Page 2
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`

`

`U.S. Patent Jun. 2, 1998 Sheet 2 of
`5,760,715
`10
`
`22
`
`EARTH
`
`30
`
`32 34
`
`20
`
`+5V
`
`R 1
`Vt
`
`+24 V
`
`Vp
`
`
`
`EARTH
`
`Q2
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`Ro
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`CIRCUIT
`GROUND
`(0 VOLT)
`
`FIG. 3
`
`Rb
`
`vi-.
`
`Vo
`
`
`
`10/
`
`Samsung EX1010 Page 3
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`

`

`U.S. Patent
`Jun. 2, 1998 Sheet 3 of 10
`
`5,760,715
`
`+ 5 V
`
`30
`
`rvi
`
`Cin
`
`Rjn
`
`+ 24 V
`
`___ ___._Vo
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`Ro
`
`r-71
`
`-J;;- E
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`ARTH
`
`R1
`
`....------------vt
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`v.P
`
`
`
`EARTH
`
`-
`
`CIRCUIT
`GROUND
`(0 VOLT)
`
`Fl G. I.
`
`Samsung EX1010 Page 4
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`

`

`U.S. Patent Jun. 2, 1998 Sheet 4 of 10
`
`5,760,715
`
`Yp
`
`+ 5 V ........ -- - - --,
`
`OV-J----------'-...J._----__J�L----____.,-.,._�
`
`t
`
`Fl G. 5 (A)
`
`Vt
`
`•2:vf__.____
`
`-----L.........D...L-.-- ---L-0-L--- ____ D__.___..
`
`FIG. 5 (8)
`
`t
`
`KEY TOUCH
`PERIOD
`
`Vj
`• 1. 5 V
`
`+ 1. 2 V
`+0.9V
`
`ov
`
`Fl G. 5 (C}
`
`t
`
`
`IN P U T "TO U C H"
`�LEVEL---.
`
`FIG. 5 (D)
`
`..
`..
`OUTPUT
`NO TOUCH "TOUCH" LEVEL
`V0 REFERENCE /
`'-...
`LEVEL
`¥'
`�
`
`+Q.9V
`
`"NO TO UC H "
`REFERENCE
`LEVEL
`�
`
`•0.3V
`
`ov-l-- ------------- -------
`FIG. 5 (E)
`
`Samsung EX1010 Page 5
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`

`

`U.S. Patent
`Jun. 2,
`1998 Sheet 5 of 10
`
`5,760,715
`
`♦ sv
`
`IN
`Vj
`
`Q2
`
`SELECTOR
`
`IN
`Vj
`
`Q2
`UT
`SELECTOR 2
`
`--
`
`-...
`_,,.--
`I'
`, I
`,,, C
`I
`\ _.,,,."
`1
`I ,,,
`
`--
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`-
`
`,---\
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` I
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`I •
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`-
`--
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`--
`
`7-
`24 20
`
`30
`22
`
`32
`
`IN
`
`OUT V
`V·I
`SELECTOR 3
`
`-------
`
`0
`
`Ro
`r-�-1}
`(0 VOLT}
`-:: GROUND
`CIRCUIT
`_.,
`� SELECT CONTROL
`
`MULTIPLEXER
`
`GROUND
`CIRCUIT
`( 0 VOLT )
`
`FIG. 6
`
`Samsung EX1010 Page 6
`
`

`

`U.S. Patent
`Sheet 6 of 10 5,760,715
`Jun.2, 1998
`
`SELECT
`
`INHl811
`
`SELECT
`
`INHIBIT
`
`Fl G. 7 (A)
`
`Ft G. 7 (8)
`
`SELECT
`
`INHIBIT
`
`FIG. 7 (C}
`
`t
`
`"TOUCH LEVEL" "NO TOUCH"
`REFERENCE LEVEL
`
`V·I
`
`/\
`I
`, l
`\_ SENSOR 1 KE!_/\__SENSOR 1 KEY PAD
`NOT TOUCHED -----..
`PAD TOUCHED
`
`+1.SV
`
`+1. 2V
`+O.9V
`
`ov
`
`1
`
`FIG. 7 {D)
`
`Samsung EX1010 Page 7
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`

`

`U.S. Patent
`Jun.2, 1998 Sheet 7 of 10
`
`5,760,715
`
`__ ,i( ___ 1''\\.._ __ !4�,.._
`
`SENSOR 2
`
`2
`
`2
`
`______➔
`SENSOR 2
`
`KEYPAD NOT
`TOUCHED
`
`V
`· t•1.5 �.1. 2 V
`+0.9V
`0 V ____ ____.
`
`2
`
`SENSOR 2
`KEYPAD NOT
`KEYPAD
`TOUCHED
`TOUCHED
`
`FIG. 7(E)
`
`Vi
`
`+1.5V
`+1.2V+----.
`+0.9 3
`-�-- SENSOR 3 KEYPAD--!'\__SENSOR 3 __/
`
`ov
`
`NOT TOUCHED
`
`KEYPAD
`TOUCHED
`
`F IG. 7(F)
`
`OUTPUT DUE
`OUTPUT DUE TO SENSOR 2
`TO SENSOR 1
`.-- �
`i0.9V
`
`OUTPUT DUE
`TO SENSOR 3
`
`/ ✓�
`
`Vo
`
`+0.6V
`+0.3V
`
`ov
`
`' 2 I 3
`
`I l
`
`FIG. 7 (G)
`
`t
`
`t
`
`t
`
`Samsung EX1010 Page 8
`
`

`

`U.S. Patent Jun. 2, 1998 Sheet 8 of 10
`
`5,760,715
`
`30
`
`36
`
`30
`
`32
`
`24
`
`L--+----------�---- ,
`36
`
`FIG.8
`
`I
`
`--,__
`
`I
`
`24
`
`22
`
`---20
`
`32
`
`30
`
`FIG. 9
`
`30
`
`Samsung EX1010 Page 9
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`

`

`U.S. Patent
`Jun. 2, 1998 Sheet 9 of 10
`
`5,760,715
`
`30
`
`36
`
`32
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`Ff G. 10
`
`40
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`
`32
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`36
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`36
`
`CIRCUIT
`GROUND
`
`{O VOLT)
`
`FIG. 11
`
`Samsung EX1010 Page 10
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`

`

`U.S. Patent
`Jun.2, 1998 Sheet 10 of 10
`
`5,760,715
`
`30
`
`30 32
`
`/ OUT
`SELECTOR 1
`SELECTOR 2
`
`CIRCUIT
`GROUND
`(0 VOLT)
`
`MICROCONTROLLER
`
`PULSE
`OUTPUT
`VP
`
`I /0
`
`OUT
`SELECTOR N
`SELECTOR 3
`Vo
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`Ro
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`CIRCUIT
`GROUND
`(0 VOLT}
`
`A /D IN
`
`-t 24V
`
`FIG. 12
`
`EARTH
`CIRCUIT
`GROUND
`( 0 VOLT)
`
`Samsung EX1010 Page 11
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`

`

`
`
`PADLE� TOUCH SENSOR
`
`BACKGROUND
`
`SUMMARY
`
`1
`
`5,760.715
`
`2
`need to be deposited over the sensing location of the
`
`
`
`
`
`
`dielectric element for the system or method to function. The
`
`
`
`
`conductive plate of each sensor is instead provided in close
`This application claims the benefit of U.S. Provisional
`
`
`
`
`
`contact with the opposite side of the dielectric element. This
`
`
`Application No. 60/014.638. filed Apr. 15. 1996.
`
`
`
`
`5 results in greater simplicity and flexibility with regards to
`
`
`
`
`the production and installation of a keyboard combining one
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`
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`or a plurality of sensors. Greater key density and a consid­
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`
`
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`Conventional capacitive touch sensing systems employ a
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`
`
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`erably smaller sensing location are possible compared to
`
`
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`passive form of detection. In such sensor, there is an existing
`
`
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`traditional capacitive sensing systems.
`capacitive circuit driven by a source signal. A key touch,
`
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`
`
`representing a change to the circuit capacitance. results in 10
`
`
`
`
`In particular, the present invention features a padless
`
`
`attenuating the potential and resulting voltage level change
`
`
`
`
`touch sensor for detecting a touch at a sensing location onto
`
`
`
`
`indicates a key touch. This capacitive circuit is usually
`
`
`
`a dielectric element by a user coupled to earth. The sensor
`
`
`
`implemented by the deposition of opposing conductive key
`
`
`
`comprises a conductive plate attached under the dielectric
`
`
`pads to opposite sides of a dielectric element.
`
`
`element and in registry with the sensing location. A means
`l5
`
`
`
`for applying a predetermined potential on the
`is provided
`
`FIG. 1 shows an example of a conventional capacitive
`
`
`
`
`conductive plate. Test pulses are injected into earth using a
`
`
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`coupled touch sensor according to the prior art. FIG. 2 shows
`
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`pulse test generating means and a means responsive to a
`
`
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`the equivalent circuit of the sensor shown in FIG. 1.
`
`
`
`potential variation in the conductive plate produces an
`
`
`One problem with conventional sensors is that accumu­
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`
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`output signal indicative of that variation. In use. when the
`
`lation of foreign deposits on the key pads has the drawback
`
`
`
`
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`user touches the dielectric element at the sensing location. a
`
`of negating the effect of a touch by the user. Chemicals and 20
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`plate during a potential variation occurs in the conductive
`
`
`
`abrasion of the exposed key pads can also degrade perfor­
`
`formed between earth.
`
`test pulse due to a capacitive circuit
`
`
`
`mance. Yet, different dielectric characteristics, such as thick­
`
`
`the user and the means responsive to the potential variation.
`
`
`
`ness and dielectric constant. result in having to change or
`
`
`redesign the size of the key pads to achieve the same
`
`
`
`
`The present invention also provides a padless touch
`25
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`
`
`
`capacitance for a different dielectric element in identical
`
`
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`sensor for detecting a touch at sensing locations onto a
`applications.
`
`
`
`dielectric element by a user coupled to earth. The sensor
`
`
`
`
`comprises a plurality of conductive plates. one for each
`
`
`Another type of conventional sensing system is a plastic
`
`
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`sensing location. Each conductive plate is attached under the
`
`
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`membrane switch. Plastic membrane switches are not suit­
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`
`
`dielectric element and in registry with a respective sensing
`
`able for applications where they are located close to high
`30
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`
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`location. A predetermined potential is successively applied
`
`
`
`temperature sources, such as on a cooktop surface. When a
`
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`on one of the conductive plates at once. A test pulse is
`
`
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`plastic membrane is located in the vicinity of a heat source,
`
`
`produced into earth while one of the conductive plates
`
`
`it would have a tendency to warp or separate. They are also
`
`
`
`
`receives the predetermined potential. A means responsive to
`
`
`susceptible to easy damage by heat and abrasion in a
`
`
`a potential variation in the conductive plate with the prede­
`
`
`situation where it is normal that objects are used nearby or
`35
`
`
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`termined potential is then provided for producing an output
`
`
`
`can be placed on the membrane. Actuation of this type of
`
`
`
`signal indicative of the potential variation in that conductive
`
`
`
`switch is mechanical in nature and reliability is inherently
`plate.
`
`reduced with use.
`The present invention also provides a padless touch
`
`
`
`Infra-red detection methods are sensitive to extraneous or
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`
`
`
`
`
`
`
`sensor for detecting a touch at sensing locations onto a
`
`
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`even ambient light sources. Accumulation of foreign matter
`40
`
`
`
`dielectric element by a user coupled to earth. The sensor
`
`
`
`or objects placed over the sensing locations can affect
`
`
`comprises a plurality of conductive plates. one for each
`
`
`
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`
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`sensitivity or produce erroneous detections. Moreover. the
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`
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`sensing location. Each conductive plate is attached under the
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`
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`front plate or panel in front of the infra-red transmitters and
`
`
`
`
`dielectric element and in registry with a respective sensing
`
`
`
`detectors must be transparent for the technology to function.
`
`
`
`
`location. A means for applying a predetermined potential on
`45
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`
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`the conductive plates is provided and test pulses are injected
`
`
`
`into earth. A means responsive to a potential variation in the
`The object of the present invention is to provide a padless
`
`
`
`
`
`
`conductive plates with the predetermined potential is then
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`
`
`
`
`touch sensor employing direct capacitive coupling under a
`
`
`
`
`provided for producing output signals indicative of the
`
`
`
`dielectric element, such as a glass window, a ceramic plate.
`
`
`
`potential variation in each of the conductive plates.
`
`etc. This sensor and the corresponding method have several
`50
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`
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`important advantages over the traditional touch sensing
`
`
`
`According to the present invention. there is also provided
`
`
`
`systems and methods previously described.
`
`
`a method for detecting a touch at a sensing location onto a
`
`
`
`
`are sent to invention, test pulses According to the present
`
`
`dielectric element by a user coupled to earth. The method
`
`earth and when a user, standing by a sensor, touches the
`
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`
`
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`comprises the steps of applying a predetermined potential on
`dielectric element at one sensing location, pulses are sup­
`
`
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`element and under the dielectric 55 a conductive plate attached
`
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`plied to a conductive plate located under the dielectric
`
`
`in registry with the sensing location. Test pulses are pro­
`
`
`
`element and in registry with the sensing location. These
`
`
`duced into earth and a potential variation on the conductive
`
`
`
`pulses are due to the capacitive reaction of the body of the
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`
`
`plate is sensed. An output signal indicative of the potential
`
`
`user to the test pulses sent into earth. A coupling path is thus
`
`variation is then produced.
`
`formed through the body capacitance with reference to earth.
`According to another aspect of the present invention,
`
`
`60
`
`One of the important advantages of the present invention
`
`there is also provided a method for detecting a touch at
`
`is that it is only the touch of the user that is actively coupling
`
`
`
`
`sensing locations onto a dielectric element by a user coupled
`
`
`
`the circuit and activating the sensor, unlike the traditional
`
`
`
`to earth. Each sensing location is provided with a corre­
`
`
`
`sensing systems that depend on disturbing an existing
`
`
`
`sponding conductive plate attached under the dielectric
`
`capacitive circuit.
`
`
`
`sensing location. 65 element and in registry with the respective
`
`The proposed touch sensor and method have several
`
`
`The method comprises the steps of successively applying a
`
`
`
`
`major impacts on overall system design. No conductive pads
`
`
`
`predetermined potential on one of the conductive plates at
`
`Samsung EX1010 Page 12
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`

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`5.760,715
`
`VO
`
`
`
`FIG. 10 is a schematic view of an example of a sensor
`
`4
`3
`FlG. 7E is a graph showing an example of the input signal
`
`
`once. A test pulse is produced into earth each time the
`
`
`
`V, representing the potential of the conductive plate of the
`
`
`
`predetermined potential is applied on one conductive plate.
`
`
`second key of FIG. 6 in function of time and following the
`
`
`
`
`A potential variation in each of the conductive plates is
`
`key selection shown in FIG. 7B.
`
`
`
`sensed while the predetermined potential is applied thereon.
`
`
`
`
`An output signal is then produced. The output signal is 5
`FIG. 7F is a graph showing an example of the input signal
`
`
`
`
`
`indicative of the potential variation in each of the conductive
`
`
`
`V, representing the potential of the conductive plate of the
`
`
`
`plates while the predetermined potential is individually
`
`
`
`third key of FIG. 6 in function of time and following the key
`
`applied thereon.
`
`selection shown in FIG. 7C.
`
`
`
`According to another aspect of the present invention.
`FIG. 7G is a graph showing an example of the resulting
`
`
`10 output signal
`
`
`there is provided a method for detecting a touch at sensing
`
`
`representing the potential at the output of
`
`
`
`
`locations onto a dielectric element by a user coupled to
`
`
`
`the transistor Q2 in function of time in the sensor of FIG. 6
`
`
`
`
`earth. each sensing location being provided with a corre­
`
`
`and in response to the input signals V, shown in FIGS. 7D.
`
`
`
`sponding conductive plate attached under the dielectric
`7E and 7F.
`
`
`
`
`element and in registry with the respective sensing location.
`FIG. 8 is a schematic view of an example of a touch at a
`
`
`
`the method comprising the steps of:
`
`
`15 sensing location which overlaps different traces.
`
`
`
`applying a predetermined potential on the conductive
`
`
`FIG. 9 is a schematic circuit diagram of the equivalent
`plates;
`
`
`circuit of the sensor shown in FIG. 8.
`
`
`producing test pulses into earth;
`
`
`with a grounding plate.
`
`
`
`sensing a potential variation in each of the conductive
`20
`
`
`FIG. 11 is a schematic circuit diagram of the equivalent
`
`plates; and
`
`circuit of the sensor shown in FIG. 10.
`
`
`
`
`producing output signals indicative of the potential varia­
`
`
`FIG. 12 is a schematic view of a sensor with multiple
`tion in each of the conductive plates while they are
`
`
`
`
`
`keys. according to a preferred embodiment of the present
`being sensed.
`25 invention.
`
`
`
`A non restrictive description of preferred embodiments
`
`
`will now be given with reference to the appended drawings.
`DESCRIPTION
`Referring to FIG. 3. there is shown a basic sensor (10)
`
`
`
`
`
`according to a possible embodiment of the present inven-
`
`
`
`FIG. 1 is a schematic view of a capacitive coupled touch
`
`
`under a dielectric 30 tion. The basic sensor (10) is mounted
`
`
`sensor according to the prior art.
`
`
`
`
`element (20) and is illustrated in a "touch" condition since
`
`
`FIG. 2 is a schematic circuit diagram of the equivalent
`
`
`
`
`the sensing location (22) on the dielectric element (20) is
`
`
`circuit of the sensor shown in FIG. 1.
`
`touched by a finger (24) of a user.
`
`
`FIG. 3 is a schematic view of a basic padless touch sensor
`
`
`The basic sensor (10) can be divided in two main parts.
`
`
`
`according to a possible embodiment of the present inven­
`
`
`
`section. 35 namely a test pulse generator section and a receiver
`tion.
`
`
`Those parts are described in detail hereinbelow.
`
`FIG. 4 is a schematic circuit diagram of the equivalent
`
`
`
`
`The test pulse generator section produces test pulses into
`
`circuit of the basic sensor shown in FIG. 3.
`
`
`earth. Preferably. the test pulse generating means comprises
`
`
`FIG. SA is a graph showing an example of the pulse signal
`
`
`
`a resistor having an input terminal connected to a DC source
`
`of FIG. 3. VP in function of time in the sensor
`
`
`40 and an output terminal connected to earth. The output
`
`
`
`of the resistor is also connected to the collector of
`terminal
`
`FIG. SB is a graph showing an example of the pulse test
`
`
`a transistor. The emitter of the transistor is then connected to
`
`
`
`signal V, in function of time in the sensor of FIG. 3.
`
`
`
`
`the circuit ground. A pulsed signal is generated at the base
`
`
`FIG. SC is a schematic representation of an example of a
`
`of the transistor. FlGS. 3. 4 and 12 show such construction.
`
`
`key touch scenario in function of time.
`
`
`In this embodiment. a +24 volts DC potential is applied
`
`
`
`FIG. SD is a graph showing an example of the input signal 45
`
`
`
`through a resistor Rl that is connected to earth. A typical
`
`
`
`V, representing the potential of the conductive plate in
`
`
`value for the resistor Rl would be 10 Kohms. A transistor Ql
`
`
`
`function of time in the sensor of FIG. 3 and during the key
`
`
`
`
`alternatively connects and disconnects the circuit ground to
`touch scenario of FIG. SC.
`VP of +5 volts for instance,
`and from earth. A pulse signal
`
`FIG. SE is a graph showing an example of the output
`
`
`
`The circuit ground 50 arrives at the base of the transistor QI.
`
`representing the potential at the output of the
`signal
`
`
`and earth are disconnected whenever VP drops to O volt.
`This
`
`
`
`transistor Q2 in function of time in the sensor of FIG. 3 and
`
`
`
`
`applies a +24 volts. with reference to the circuit ground, at
`
`
`V, shown in FIG. SD. in response to the input signal
`
`
`the opposite side of the resistor RI. As soon as the pulse
`
`
`
`FIG. 6 is a schematic view of a padless touch sensor with
`
`
`
`Ql is the transistor signal VP is back to the +5 volt level.
`
`
`
`
`multiple keys. according to a preferred embodiment of the
`
`55 switched on again and the circuit ground and earth are
`
`
`
`present invention, shown without the test pulse signal gen­
`
`
`
`
`connected together. dropping V, to O volt. FIGS. SA and SB
`erator.
`
`VP and the resulting test
`
`respectively show the pulse signal
`
`
`
`FIG. 7A is a schematic representation in function of time
`
`pulse signal V, that is injected into earth.
`
`of the selection of the first key of FIG. 6.
`Earth in the context of the present invention means the
`
`
`
`
`FIG. 7B is a schematic representation in function of time
`
`
`ground. For 60 real earth or any other mass acting as a virtual
`
`of the selection of the second key of FIG. 6.
`
`
`
`instance, in case of an appliance. the sensor can be con­
`nected to the real earth by means of a wire electrically
`
`
`
`FIG. 7C is a schematic representation in function of time
`
`
`
`connected to the grounding prong of the appliance. itself
`
`of the selection of the third key of FIG. 6.
`
`
`connected to the earth wire of the building. As for the virtual
`
`FIG. 7D is a graph showing an example of the input signal
`
`65 ground. an example could be the metallic body of a vehicle.
`
`
`
`V, representing the potential of the conductive plate of the
`
`
`The receiver section of the basic sensor (10) comprises a
`
`
`first key of FIG. 6 in function of time and following the key
`
`
`
`conductive plate (30) located under the dielectric element
`
`selection shown in FIG. 7 A.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`VO
`
`
`
`Samsung EX1010 Page 13
`
`

`

`5,760,715
`
`6
`5
`ments have shown that the distance between the user and the
`
`
`
`(20). The plate (30) is in registry with the sensing location
`
`
`
`
`test pulse generator section may be as far as 50 meters. A
`
`(22)onto the dielectric element (20). The sensing location
`
`
`
`
`
`shielded cable was used to connect the plate (30) to the
`(22)and the corresponding conductive plate (30) are also
`
`
`
`remote circuit board (32).
`
`
`
`referred to as a "key". If appropriate, markings may be
`
`
`When there is a key touch. like in FIGS. 3 and 4. the touch
`provided to indicate to the user the exact location where the 5
`
`
`
`
`
`
`
`detection is achieved by coupling the +24 volts DC test pulse
`
`finger (24) has to touch to achieve a touch condition at the
`
`
`
`
`
`
`signal through the user's effective body capacitance, to the
`
`key. Of course. a person skilled in the art would realize that
`
`
`
`
`
`plate (30). by way of earth. The test pulse signal V, is applied
`the term "finger" may be substituted for any body part that
`
`to earth and to one side of body capacitance
`Cs-The value
`can be used for touching a key. For instance, a handicapped
`
`
`10 of the capacitance
`
`
`Cs is typically between 200 and 500 pF.
`person may have to use his or her toes instead of one finger.
`
`
`
`
`in series During a key touch. the capacitance Cs is connected
`
`
`
`
`
`The present invention may also work in applications where
`to the capacitance
`
`CF, which represents the capacitance
`animals are involved.
`
`
`
`formed by the user's contact area at the sensing location
`
`
`
`
`
`The receiver section further comprises a means for apply­
`
`
`
`(22). the dielectric element (20) and the conductive plate
`
`
`
`ing a predetermined potential on the plate (30). This sets a
`(30).
`CF is 20 pF for a 1,s
`
`A typical value of the capacitance
`
`
`
`
`reference voltage. referred to as a "no touch" reference level.
`
`
`
`15 inch thick glass-ceramic with a dielectric constant of 22 and
`
`
`
`Then, a means responsive to a potential variation in the plate
`
`
`
`
`a plate area of about 0.5 square inch. A material with a higher
`
`
`
`(30)is used to produce a signal indicative of the potential
`
`
`
`relative dielectric constant increases the capacitance CF and
`
`
`variation. It is this signal that will be used to determine if
`
`
`
`
`produces improved signal coupling to the sensor or
`
`there is a touch condition or not.
`
`
`
`
`alternatively. allows the use of a thicker dielectric element
`
`
`As aforesaid. the plate (30) is attached under the dielectric
`
`
`
`20 (20). Increasing the thickness of the dielectric element (20).
`
`
`
`element (20). There are many ways of achieving the con­
`
`
`with the area of the plate (30) remaining constant. decreases
`
`
`nection. One is to provide the plate (30) on a circuit board
`
`the value of CF and the resulting coupling to the sensor.
`
`
`(32)and to connect the circuit board (32) with. for instance,
`
`
`
`The capacitance for parallel plates is given by the fol­
`
`
`
`Of course,(not shown). an adhesive strip (34) or with screws
`
`
`lowing general formula:
`
`
`other kinds of attachments may be used, according to the 25
`
`particular needs and environment.
`
`
`FIG. 3 shows a possible embodiment of the present
`
`
`invention. where the means for applying a predetermined
`wherein.
`
`
`
`
`potential and the means responsive to a potential variation in
`
`
`
`the plate (30) are combined together using a transistor Q2.
`A is the area of plates.
`
`
`
`FIG. 4 shows the equivalent circuit when there is a touch
`30
`
`d is the distance between the plates.
`
`condition, also referred to as a "key touch".
`
`e is a constant, and
`
`
`The transistor Q2 is connected in a high input impedance
`
`
`k is the relative dielectric constant.
`
`
`emitter follower configuration. The voltage gain of the
`
`
`One can see that for a dielectric element of a specific
`Rb is connected
`
`
`circuit is slightly less than 1. A resistor
`thickness.
`35
`
`the area of the conductive plate (30) and the
`
`
`between the base of the transistor Q2 and a second supply
`
`
`the value of the contact area of the finger (24) determines
`
`
`
`
`voltage source. The resistor � serves as a termination and
`
`
`
`
`capacitance CF. Increasing the contact area will increase the
`
`
`bias for the input and sets the "no touch" reference level at
`
`
`
`capacitance and improve coupling of the test pulse signal V,
`an output resistor
`
` The other end of the resistor Ro is
`
`
`
`to the sensor. The maximum area is however limited by the
`
`
`connected to the circuit ground.
`
`
`contact area for a typical human finger, beyond which
`
`
`
`would be +5 volts DC. 40 A typical second supply voltage
`
`
`The input resistance R;n at the base of the transistor Q2 is
`
`
`increasing the area of the plate (30) has no effect. A circular
`
`approximately given by the formula hFeX!l· The input
`
`
`plate of ½ inch diameter is a reasonable maximum useable
`
`
`
`resistance R;n is then approximately between 0.5 Mohmand
`
`
`limit to set for finger actuation. However. a ¼ inch diameter
`
`
`
`2 Mohms for a typical transistor when the resistor
`is 4.7
`plate works very reliably.
`
`Kohms and hFE between 100 and 400. Decreasing the value 45
`
`When the test pulse signal V, goes from O volt to +24
`
`
`
`of the resistor Rb raises the potential at the base of the
`
`
`volts. the capacitance Cs and CF acts instantly
`as a "short"
`
`
`
`transistor Q2 and also the "no touch" reference level. For
`
`
`and +24 volts would normally be applied to the base of the
`
`
`instance, this level can be adjusted from +o.6 volt to +3.4
`
`
`transistor Q2. The effective capacitance of Cs and CF in the
`
`
`
`volts by adjusting the resistor Rb from 5.6 Mohms to 200
`
`example is approximately 18 pF. Since the input base
`
`
`
`
`Kohms. The detection level at the output resistor
`can also 50
`
`
`capacitance Cm of the transistor Q2. which is in the range of
`R0
`
`
`
`be adjusted by changing the value of the resistor Rb to
`
`
`
`5 pF to 10 pF for a typical transistor, is comparable to the
`
`
`
`
`
`
`compensate for different coupling levels for various sizes of
`
`of C8 and CF combined, the signal
`
`coupling capacitance
`
`
`
`
`the conductive plates (30). Any convenient reference level
`
`
`
`level that the transistor Q2 receives is actually lower than
`
`
`can be chosen depending on the application and power
`
`
`
`+24 volts. The input resistance of the transistor Q2 also acts
`
`
`supply voltage available.
`
`
`
`
`to reduce the level depending on the coupled resistance. The
`In use, the VP test pulse signal drives
`
`the transistor Ql
`55
`
`
`rise time of the test pulse signal V, also acts to further reduce
`
`
`
`which alternatively connects and disconnects the circuit
`
`
`
`this level. If this time is comparable or greater than the time
`
`
`ground to and from earth. In the illustrated embodiment. the
`
`
`
`constant of the input resistance of the transistor Q2 and the
`
`
`
`first supply voltage is +24 volts DC and when the transistor
`
`coupling capacitance
`
`
`(C8 and CF). the coupled signal level
`
`
`Ql is switched off, the +24 volts DC is applied through the
`
`
`
`is further reduced. The transmitted test pulse signal V, from
`
`
`
`resistor Rl to earth for producing the test pulse signal V r 60
`
`earth generally does not have a very sharp rise time. The
`
`
`FIGS. SA and SB show the typical waveforms. Preferably,
`
`
`effective signal coupled to the transistor Q2 is thus much
`
`
`the test pulse signal V, is applied once every 1 ms.
`
`lower than +24 volts, and typically is +o.3 volt.
`
`The test pulse sign al V, is coupled from earth to the
`
`FIG. SC shows an example of a key touch period with
`
`capacitance Cs of the body of the user. When there is no key
`
`
`reference to the test pulse signal V, shown in FIG. SB. FIG.
`
`touch, the potential at the conductive plate (30) will not 65
`
`
`
`
`
`5D then shows the resulting variation of the potential in the
`
`
`change. Nevertheless, the est pulse V, is always being
`
`
`
`plate (30). FIG. SE shows how the potential variation is felt
`
`
`injected into ground and coupled to the user's body. Experi-
`is
`
`at the emitter of the transistor Q2. The output signal
`
`R0•
`
`VO
`
`
`
`R0
`
`
`
`Samsung EX1010 Page 14
`
`

`

`5.760,715
`
`0
`
`
`
`O
`
`O
`
`O
`
`8
`7
`in F1GS. 10 and 11. has the effect of shielding all conductive
`
`
`sent to an appropriate device to determine whether or not the
`
`
`
`
`
`
`traces behind it. A key touch at a sensing location (22) which
`
`
`
`
`
`potential variation is sufficient to initiate a positive key touch
`
`also overlaps another trace now has its capacitance CFc to
`
`
`
`
`
`status and, for instance. actuate a corresponding switch (not
`
`
`the overlapped trace (34'i) coupled to circuit ground.
`shown).
`
`
`Furthermore, a minimum number of conductive traces (34'i)
`
`
`FIG. (i shows a multiple key configuration. The keys are 5
`
`
`
`should run on the outward facing side of the keyboard to be
`
`
`each individually scanned to determine whether there is a
`
`able to make effective use of the shielding.
`
`key touch or not. The input to the base of the selected key
`
`
`
`
`transistor is left active ( enabled) while the inputs to the other
`
`
`
`F1G. 12 illustrates conductive plates (30) and circuit
`
`
`keys are disabled by grounding their input bases through a
`
`
`ground plane ( 40) that are etched on the outward facing side
`
`
`
`multiplexer. The individual key transistor Q2 and resistance
`
`
`
`
`of a circuit board (32). A dielectric element (20) covers and
`10
`Rb are called a "selector".
`
`
`is in close contact with the keys. The outputs of all the
`
`FIGS. 7 A. 7B and 7C illustrate schematically the selec­
`
`
`
`corresponding selectors are connected to a common output
`
`
`tion of the individual keys. When a key is selected, the test
`
`
`• As aforesaid, it is possible to provide a separate
`resistor
`R0
`
`
`pulse signal is coupled to that key only if there is a touch at
`
`output resistor R
`
`for each key. This would however require
`
`
`
`the corresponding sensing location. It should be noted that
`
`
`
`more than one output channel. A microcontroller provides
`
`the test pulse generator section was omitted from FIG. (i for 15
`
`
`
`
`
`
`the necessary signals for scanning the selector of each key
`
`
`
`simplification. FIG. 12 shows the complete system with "N"
`
`
`of the array. Measurement and analysis of the potential
`keys.
`
`variations at the output resistor
`
`is performed by the
`
`
`FIG. 7D shows an example of the input voltage V; for the
`
`
`
`microcontroller. A determination of whether a valid key
`
`
`first key. In the given example. the first key is touched in the
`
`
`
`
`touch has been received and the appropriate reaction is then
`
`first two readings of that key, while there is no key touch for 20
`performed.
`
`
`t