United States Patent
`
`[19]
`
`[11] Patent Number:
`
`4,758,735
`
`Ingraham
`[45] Date of Patent:
`Jul. 19, 1988
`
`[54]
`
`[75]
`
`DC TOUCH CONTROL SWITCH CIRCUIT
`
`Inventor:
`
`Ronald D. Ingraham, Quincy, Mich.
`
`[73] Assignee:
`
`Nartron Corporation, Reed City,
`Mich.
`
`[21] Appl. No.: 38,832
`
`[22] Filed:
`
`Apr. 15, 1987
`
`Related US. Application Data
`
`[63]
`
`Continuation-impart of Ser. No. 913,084, Sep. 29, 1986. '
`
`Int. Cl.4 ...................... H01H 35/00; HOSB 37/02
`[51]
`[52] US. Cl. .................................... 307/116; 307/308;
`307/632; 315/362; 328/5
`[58] Field of Search .................... 307/116, 125, 252 13,
`307/308; 315/34, 74, 208, 246, 362; 318/345,
`446; 323/19, 24; 328/5
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`..... 307/252
`3,549,909 12/1970 Adelson et a1.
`
`. 318/345
`3,641,410 2/1972 Vogelsberg .
`3/1972 Vogelsberg.
`..... 318/446
`3,651,391
`
`. 307/116 X
`5/1972 Bellis ...........
`3,666,988
`
`....... 315/34
`3,899,713
`8/1975 Barkan et a1.
`
`3,919,596 11/1975 Bellis ...........
`. 307/308 X
`
`. 307/ 125 X
`3,965,465 6/ 1976 Alexander
`....... 323/19
`3,984,757 10/1976 Gott et a1.
`
`4,016,453 4/1977 Moennig .....
`307/308 X
`. 307/116
`4,031,408
`6/1977 Holz
`
`7/1978 Stone ................
`4,101,805
`315/74
`
`4,119,864 10/1978 Petrizio ............................... 307/116
`4,152,629 5/ 1979 Raupp ..
`....... 3 l 5/362
`
`4,159,473
`6/1979 Senk .....
`307/116 X
`7/1980 Wem ............................... 307/116
`4,210,822
`
`4,211,959 7/1980 Deavenport et a1.
`315/362
`
`7/1980 Conner .....
`4,213,061
`307/116
`
`1/1981 Chiang ..
`4,246,533
`307/116 X
`
`....... 307/252
`4,264,831
`4/1981 Wem
`9/1981 Wem ............
`4,289,972
`307/116
`
`....... 307/308
`4,289,980
`9/1981 McLaughlin
`.. 307/116 X
`4,308,443 12/1981 Tucker et a1.
`4,323,829 4/1982 Witney et a1.
`307/116 X
`4,360,737 11/ 1982 Leopold .............................. 307/116
`
`
`
`Primary Examiner—William M. Shoop, Jr.
`Assistant Examiner—Sharon D. Logan
`Attorney, Agent, or Firm—Price, Heneveld, Cooper,
`DeWitt & Litton
`
`[57]
`
`ABSTRACT
`
`A switching circuit includes a source of direct current
`for operating an oscillator which in turn applies a signal
`to a detector circuit including a touch plate. The detec-
`tor includes a voltage dividing capacitive system or, in
`one embodiment, a phase detector circuit. In either
`embodiments, the output signal from the phase detector
`circuit or the voltage divider provides a control signal
`which can be used for actuating a solid-state switch
`such as a transistor or the like for providing control
`functions.
`
`15 Claims, 2 Drawing Sheets
`
` 1
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`APPLE 1017
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`1
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`APPLE 1017
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`

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`US. Patent
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`Jul. 19, 1988 I
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`Sheet 1 012
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`4,758,735
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`US. Patent
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`Jul. 19, 1988
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`Sheet 2 of2
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`4,758,735
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`1
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`4,758,735
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`2
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`DC TOUCH CONTROL SWITCH CIRCUIT
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`The present application is a continuation-in-part ap-
`Referring initially to FIG. 1 there as shown, a direct
`plication of pending application Ser. No. 06/913,084 5 current (dc) powered touch control switch system 10
`filed Sept. 29, 1986 entitled “Touch Control Switch
`which utilizes a detector circuit including a voltage
`Circuit” to Ingraham. The subject matter of this prior
`dividing capacitive circuit having a first capacitor 12
`application is incorporated herein by reference.
`coupled in series with the body capacitance 14 of a
`person touching a touch plate 15. Plate 15 is electrically
`BACKGROUND OF THE INVENTION
`coupled to base terminal 20 of PNP switch transistor 22
`by a current limiting resistor 17. The touch plate 15 can
`be made of an electrically conductive material such as
`aluminum or the like and may be covered by a plastic
`overlie 16 which can carry printed indicia 18 thereon
`identifying for example, the switch function. Thus, it is
`not necessary for the operator to actually touch the
`electrically conductive plate 15 but only come suffi-
`ciently close to add the body capacitance 14 in series
`with the voltage dividing capacitor 12 which is coupled
`to an oscillator circuit 30 including a drive transistor 40.
`Oscillator 30 is an astable multi-vibrator comprising a
`pair of OR gates 32 and 34 coupled as inverters and
`cross-coupled by resistors 31, 33 and a capacitor 35 in a
`conventional manner as shown in the diagram.
`Resistor 36 applies the square wave output signal
`from the output of gate 34 to the base terminal 42 of
`PNP transistor 40 which has an emitter terminal cou-
`pled to the +V supply. The +V supply represents the
`positive terminal of a dc supply voltage such as a vehi-
`cle battery. Transistor 40 has a collector terminal 43
`coupled to ground 11 which for example, is the negative
`terminal of the +V source (i.e. vehicle battery) by
`means of resistor 44. Ground 11 typically will comprise
`a relatively large conductive area such as the vehicle
`chassis coupled to the negative terminal of the vehicle
`battery which is necessary for operation of the system.
`Circuits 32 and 34 are part of an integrated circuit
`which is supplied operating power from the +V supply
`in a conventional manner. A circuit such as a commer-
`cially available model CD 4070 BE or MC 14070 BCP
`can be employed for circuits 32 and 34 and the remain-
`ing invertor circuits 50 and 52 coupled as a Schmitt
`trigger as described below.
`The square wave signal applied to base terminal 42 of
`transistor 40 causes transistor 40 to conduct providing a
`positive going signal to the junction of capacitor 12
`with collector terminal 43 which is coupled to the emit-
`ter terminal 21 of transistor 22. Base terminal 20 is cou-
`pled to the emitter terminal 21 by resistor 24 such that
`unless capacitance 14 is present by the user touching or
`coming proximate to touch plate 15, transistor 22 will
`not be forward biased and will not conduct. Thus, when
`plate 15 is not touched, the output signal at collector
`terminal 23 and across a pulse stretcher circuit compris-
`ing resistor 26 and capacitor 28 will be zero volts.
`When, however, a person touches plate 15 thereby
`coupling capacitor 14 in series with capacitor 12, the ac
`voltage applied to base terminal 20 will be lower than
`the voltage applied to the emitter 21 thereby forward
`biasing transistor 22 into pulsed conduction. This tends
`to charge capacitor 28 providing a positive dc voltage
`to the Schmitt trigger circuit 60. A diode 25 is coupled
`across the base to emitter junction of transistor 22 to
`provide protection against reverse breakover voltage.
`The Schmitt trigger 60 comprises serially coupled
`inverter circuits 50 and 52 with feedback resistor 51
`coupled from the output of inverter 52 to the input of
`invertor 50 and to capacitor 28 through resistor 54.
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`The present invention relates to an electrical circuit
`and particularly to a touch controlled electrical switch-
`ing circuit for portable direct current operation.
`There exists a variety of electrical switching circuits
`which respond to a person’s touch on a touch pad
`which may be in the form of a lamp base or a specific
`surface area of an electrical appliance to be actuated.
`These circuits represent a convenient manner in which
`a consumer can easily operate an appliance without the
`need for manually actuating a conventional toggle or
`push~button switch. US. Pat. Nos. 4,119,864 and
`4,360,737 are representative of existing touch control
`switch circuits. Many of these circuits and other similar
`circuits require the utilization of 60 Hz line voltage for
`their operation. In some cases the circuits require a 60
`Hz induction field which induces a voltage applied to
`the circuit by the human body operating as an antenna
`for generating a control signal.
`SUMMARY OF THE PRESENT INVENTION
`
`The system of the present invention does not rely
`upon the utilization of a line frequency voltage source
`and as such can be operated as a portable touch control
`switch circuit where no alternating current voltage is
`available. Applications for the system of the present
`invention include vehicles such as automobiles, trucks,
`boats and airplanes. The system is not necessarily lim-
`ited to, however, portable applications since it can like-
`wise be used where ac power is available.
`Systems embodying the present invention include a
`source of direct current for operating an oscillator
`which in turn applies a signal to a touch plate coupled to
`a detector circuit. The detector includes a voltage di-
`viding capacitive system or, in one embodiment, a phase
`detector circuit. In either embodiments, the output sig-
`nal from the phase detector circuit or the voltage di-
`vider provides a control signal which can be used for
`actuating a solid-state switch such as triac or the like for
`providing control functions. When used in vehicles
`such as automobiles, the system can be used for actuat-
`ing door locks, power windows, or other accessories.
`Thus, the touch control circuit of the present invention
`can be used in environments where alternating current
`voltage is not generally available.
`These and other features, objects and advantages of
`the present invention can best be understood by refer-
`ence to the following description thereof together with
`the accompanying drawings in which:
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is an electrical circuit diagram in block and
`schematic form of a first embodiment of the present
`invention; and
`FIG. 2 is an electrical circuit diagram in block and
`schematic form of an alternative embodiment of the
`present invention.
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`Thus, when plate 15 or its coating 16 is touched, the dc
`level across to the input of Schmitt trigger 60 will rise to
`a level sufficient for the Schmitt trigger circuit to trig-
`ger providing a positive going output pulse at output
`terminal 70 of the circuit. This control output signal can
`be employed as a control input for a conventional solid-
`state switch circuit 72 shown in block form in the figure
`which may include a transistor or the like coupled be-
`tween the +V supply and a load 74 such as a power
`window motor, door lock or the like. The system can
`also be employed for controlling an alternating current
`(ac) load 74 by coupling the load and switching circuit
`72 to the ac supply independently of the +V supply.
`In the preferred embodiment of the invention Resis-
`tors 31 and 33 are 10 megohms and ] megohm, respec-
`tively while capacitor 35 is 0.001 microfarad (mfd).
`Resistors 36 and 44 are 4.7 kilo-ohms and 1 kilo-ohm,
`respectively while resistor 17 was 10 megohms. Resis-
`tor 24 was 4.7 megohms while capacitor 12 was 100
`picofarads. The body capacitance 14 typically ranges
`from 100—300 picofarads. Resistor 26 is 100 kilo-ohms
`while capacitor 28 is 0.01 microfarads. Resistor 54 is 100
`kilo-ohms, while resistor 51 is 1 megohm.
`Referring now to the FIG. 2 embodiment of the in-
`vention, circuit 100 like circuit 10 includes an oscillator
`circuit 110 comprising a pair of exclusive OR gates 102
`and 104 each having one input terminal coupled to a dc
`voltage suppl Vpp. The remaining input terminals of
`gates 102 and 104 are coupled to each other by resistors
`106 and 108 the junction of which are coupled to the
`output terminal 115 of gate 104 by feedback capacitor
`112. Oscillator 110 provides at output terminal 115 a 1
`kHz square wave signal.
`A power supply 120 is coupled to the +V supply
`such as the battery of a vehicle at one input terminal 122
`and to the chassis ground 124 of the vehicle. An input
`resistor 126 couples the + V source to a voltage regulat-
`ing Zener diode 128 for regulating the dc voltage there.
`across. The voltage is filtered by a capacitor 130 in a
`conventional manner to provide the VDD output volt-
`age which is somewhat lower than the input voltage.
`The ground terminal of supply 120 comprises the V35
`supply indicated in circuit 100.
`Output terminal 115 of oscillator 110 is commonly
`coupled to the two input terminals 140 and 142 of a
`detector circuit including an exclusive OR gate 145 by
`series coupled resistors 144 and 146. The square wave
`signals applied to input terminals 140 and 142 will be
`substantially in exact phase when the touch plate 15 is
`not touched by a person and therefore body capacitance
`14 not in the circuit. The exclusive OR gate in such
`circumstance will provide a logic “0” output for all
`polarities of these identical voltages applied to input
`terminals 140 and 142.
`Upon touching the touch plate 15 or coating 16 the
`body capacitance 14 couples terminal 142 to ground by
`means of resistor 148 to cause a slight phase shift of the
`signal applied to input terminal 142. Thusy during at
`least a portion of each cycle of the input voltage, gate
`145 will provide a dc output or a logic “1” output pulse
`which is applied to charge capacitor 150 through the
`forward biased diode 149. Typically, gate 145 will de-
`tect the dissimilar voltages applied during the leading
`edge of the square wave 1 kHz signals supplied by oscil—
`lator 110. The output signal from gate 145 thus, will be
`1 kHz dc pulses when capacitance 14 is in the circuit or
`0 volts when plate 15 is not touched. These output
`signals are applied to a pulse stretcher circuit 160 which
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`includes an exclusive OR gate 162 having one terminal
`coupled to the junction of diode 149 and capacitor 150
`and the remaining input terminal coupled to V55. A 10
`megohm resistor 151 is coupled across diode 149 to
`permit the discharge of capacitor 150.
`The pulse stretcher circuit 160 responds to the posi-
`tive output pulses from gate 145 to initially trigger gate
`162 through the application of voltage from diode 149.
`As the gate 145 output returns to a zero logic state,
`capacitor 150 which now is partially charged maintains
`the input terminal 161 of gate 162 high thereby main-
`taining the output at terminal 170 at a logic “1” level
`until such time as the pulsing signal from gate 145 dis—
`continues when the operator releases contact with
`touch plate 15 and allows capacitor 150 to fully dis-
`charge.
`The output signal at terminal 170 like the signal at
`terminal 70 of the FIG. 1 embodiment is coupled to the
`control input terminal of a suitable solid-state switch
`such as switch 72 as shown in FIG. 1 which is suitably
`coupled to a load 74 for providing a desired control
`function.
`Thus, in both of the embodiments, a soft touch capac-
`itive type switch control system is provided which can
`be operated from a dc voltage source without the need
`for an alternating current source. These circuits are
`particularly well adapted for use in the automotive
`environment or for other vehicles. It will become ap-
`parent to those skilled in the art that various modifica-
`tions to the preferred embodiments of the invention as
`disclosed herein can be made without departing from
`the spirit or scope thereof as defined by the appended
`claims.
`The embodiments of the invention in which an exclu-
`sive property or priviledge is claimed are defined as
`follows:
`1. A direct current powered touch controlled switch-
`ing circuit comprising:
`a source of direct current power;
`an oscillator coupled to said source for providing
`periodic output signals therefrom;
`a series voltage divider circuit coupled to said oscilla-
`tor for receiving said periodic output signals there-
`from, said voltage dividing circuit including at
`least one capacitor and an input touch terminal for
`coupling a person’s body capacitance in series with
`said at least one capacitor such that the voltage at
`the junction of said at least one capacitor and said
`touch terminal will vary upon a person touching
`said touch terminal; and
`a control circuit coupled to the junction of said at
`least one capacitor and said touch terminal and
`responsive to a change in voltage thereat for pro-
`viding a control output signal in response to the
`touching of said touch terminal.
`2. A circuit as defined in claim 1 wherein said control
`circuit includes a pulse stretcher circuit coupled to the
`junction of said one capacitor and said touch terminal
`for providing output pulses having a duration longer
`than said periodic output signals of said oscillator.
`3. A circuit as defined in claim 2 wherein said control
`circuit includes a Schmitt trigger circuit.
`4. A direct current powered touch controlled switch-
`ing circuit comprising:
`a source of direct current power;
`an oscillator coupled to said source and providing
`periodic output signals;
`'
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`a comparator circuit including first and second input
`terminals each coupled to said oscillator; and
`an input touch terminal for coupling a person’s body
`capacitance when touched to one of said input
`terminals of said comparator such that the periodic
`signal thereat will be varied when said touch termi-
`nal is touched wherein said comparator responds to
`the signal variation to provide an output control
`signal indicating the touching of said touch termi-
`nal.
`5. A circuit as defined in claim 4 wherein said com-
`parator comprises an exclusive OR gate.
`6. A circuit as defmed in claim 5 and further including
`a pulse stretcher circuit having an input coupled to the
`output of said OR gate and responsive to said output
`control signal for providing a predetermined logic out-
`put signal when said touch terminal is touched.
`7. A circuit as defined in claim 6 and further including
`a switch circuit having a control input terminal coupled
`to the output of said pulse stretcher circuit and switch
`terminals coupling a load to a source of power.
`8. A direct current powered touch controlled switch-
`ing circuit comprising:
`a source of direct current power;
`an oscillator coupled to said source for providing
`periodic output signals therefrom; and
`a detector circuit coupled to said oscillator for receiv-
`ing said periodic output signals therefrom, said
`detector circuit including an input touch terminal
`said detector circuit responsive to signals from said
`oscillator circuit and the simultaneous presence of
`a person’s body capacitance coupled to said touch
`terminal when touched by a person to provide a
`control output signal in response to the touching of
`said touch terminal.
`9. A circuit as defined in claim 8 wherein said detec—
`tor circuit comprises a series voltage divider circuit
`including at least one capacitor coupled to said touch
`
`6
`terminal for coupling a person’s body capacitance in
`series with said at least one capacitor, and a control
`circuit coupled to the junction of said at least one capac-
`itor and said touch terminal and responsive to the
`change in voltage at said junction when said touch
`terminal is touched for providing a control output sig-
`nal in response to the touching of said touch terminal.
`10. A circuit as defined in claim 9 wherein said con-
`trol circuit includes a pulse stretcher circuit coupled to
`the junction of said one capacitor and said touch termi-
`nal for providing output pulses having a duration longer
`than said periodic output signals of said oscillator.
`11. A circuit as defined in claim 10 wherein said con-
`trol circuit further includes a Schmitt trigger circuit
`coupled to said pulse stretcher circuit and responsive to
`output pulses therefrom to provide a predetermined
`logic output signal when said touch terminal is touched.
`12. A circuit as defined in claim 9 wherein said detec-
`tor circuit comprises a comparator circuit including
`first and second input terminals each coupled to said
`oscillator and one of said input terminals of said com-
`parator coupled to said touch terminal such that the
`body capacitance when coupled to the touch terminal
`will effect a change in voltage at said one input terminal
`resulting in the generation of said control output signal
`by said comparator circuit.
`13. A circuit as defined in claim 12 wherein said com-
`parator comprises an exclusive OR gate.
`14. A circuit as defined in claim 13 and further includ-
`ing a pulse stretcher circuit having an input coupled to
`the output of said OR gate for providing a predeter-
`mined logic output signal in response to the receipt of a
`control output signal from said OR gate.
`15. A circuit as defined in claim 14 and further includ-
`ing a switch circuit having a control input terminal
`coupled to the output of said pulse stretcher circuit and
`switch terminals coupling a load to a source of power.
`*
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