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CROSS REFERENCE TO RELATED APPLICATIONS
Touch control bar graph devices with which the present invention may be
employed in combination are disclosed in the commonly-assigned copending
application Ser. No. 750,559, filed Dec. 14, 1976, U.S. Pat. No. 4,121,204
by Stanley B. Welch, Juan de J. Serrano and David Y. Chen and entitled
"Bar Graph Type Touch Switch and Display Device"; and in commonly-assigned
copending application Ser. No. 908,317, filed May 22, 1978, by Juan de J.
Serrano and entitled "High Density Capacitive Touch Switch Array
Arrangement."
BACKGROUND OF THE INVENTION
The present invention relates generally to user input and display devices
for controlling a range or the like and, more particularly, to ON/OFF
switch arrangements for touch control bar graph devices such as are
disclosed in the applications cross referenced above.
In the above-mentioned Welch, Serrano and Chen and the Serrano
applications, devices are disclosed which advantageously and effectively
combine touch switch user-input technology and bar graph display output
technology to provide simple and readily understandable input/output
devices herein referred to as touch control bar graph devices. More
specifically, the display portion of a touch control bar graph device is a
bar graph display which continuously and graphically represents a selected
value, such as a range heat setting. The input portion is an array of
touch-sensitive areas superimposed over the bar graph, permitting
convenient changes to the setting with immediate reinforcing visual
feedback to the user. In operation, the end of the bar graph display
"follows" the tip of the user's finger in a unique and pleasing manner.
Such touch control bar graph devices are a significant improvement over
previously employed input/output devices for electronically controlled
apparatus such as appliances, particularly when "human engineering" and
user acceptability considerations are taken into account. The devices are
readily understandable and permit the construction of unintimidating
control panels which a person may use with confidence.
The previously disclosed touch control bar graph devices activate the load
device, for example a range surface unit, whenever touched. Additionally,
there is a separate "OFF" touch pad which turns off the touch control bar
graph device and the load when touched.
In certain applications, and in particular in a control for a range surface
unit, safety considerations are of utmost priority. In a range cooktop,
the possibility of a surface heating unit being energized accidentally
should be minimized. At the same time, interference with convenient
operation of the appliance should be minimized to the extent possible
consistent with safety considerations.
An Underwriters Laboratory requirement has addressed this particular
concern. Specifically, in UL 858 pertaining to "Household Electric
Ranges," Section 43 deals with "Unintentional Operation of Surface-Unit
Controls."
UL Paragraph 43.1 requires, "The control for a surface unit shall require a
minimum of two operations to activate the surface unit." In conventional,
non-electronic ranges employing rotary switches and controls, the
requirement of paragraph 43.1 is typically met by a switch having a push
and a turn or a pull and a turn operating sequence. This particular
solution is generally approved in paragraph 43.3 of the UL requirement.
Lastly, paragraph 43.2 requires, "Only one operation shall be required to
turn a surface unit off."
One example of a prior art electronic range including touch control input
devices is disclosed in U.S. Pat. No. 3,819,906 issued to Gould, Jr. The
Gould, Jr. range satisfies the UL "two operation" requirement by having
"address pads," located near the right side of the control panel, for the
individual surface cooking units. Separate "setting pads" numbered 0
through 9 are located near the center of the control panel and shared by
all four surface units. Each of the "setting pads" corresponds to a
particular heat value. To activate a heating unit of the Gould, Jr. range,
a user first touches one of the "address pads" and then touches one of the
setting pads.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a convenient
ON/OFF switch arrangement for use in combination with a touch control bar
graph device.
It is another object of the invention to provide an ON/OFF switch
arrangement for a touch control bar graph device, which arrangement
enhances the safety of the appliance by requiring two operations for
energization of a load, but which at the same time does not unduly detract
from the user-acceptability of the touch control bar graph device.
It is still another object of the invention to provide a ON/OFF switch
arrangement for a touch control bar graph employed as a domestic range
surface unit control which satisfies Underwriters' laboratory's
requirements.
Briefly stated and in accordance with one aspect of the invention, these
and other objects are accomplished by an ON/OFF touch arrangement for a
touch control bar graph device, which arrangement has an ON
touch-sensitive area positioned adjacent to but spaced from the touch
control bar graph device. There is a de-energizing touch sensitive area
positioned in the space between the ON touch-sensitive area and the touch
control bar graph device. A circuit means is responsive to the ON
touch-sensitive area and to the de-energizing touch-sensitive area for
enabling operation of the touch control bar graph device in response to
the touching of the ON touch-sensitive area, and for disabling operation
of the touch control bar graph device in response to the touching of the
de-energizing touch sensitive area. As a result, if a user attempts to
enable operation of the touch control bar graph device by moving a finger
directly between the ON touch-sensitive area and the touch bar graph
device, the user's finger at least momentarily touches the de-energizing
touch-sensitive area to disable the touch control bar graph device.
Essentially, then, this arrangement forces a user to first touch the ON
touch-sensitive area, and then to lift his finger before placing it on the
touch control bar graph device itself. The possibility of accidental turn
on is greatly minimized, and the "two operation" Underwriter's Laboratory
requirement should be satisfied.
Not only is safety enhanced by the present invention, but the close
proximity of the ON touch-sensitive area to the touch control bar graph
device makes the entire arrangement, from a user's viewpoint, easy to
understand and to use. Thus there is minimal adverse effect on the basic
simplicity (to the user) of a touch control bar graph device.
Briefly stated and in accordance with another aspect of the invention, the
de-energizing touch sensitive area is a clearly designated OFF
touch-sensitive area which corresponds to a particular touch switch touch
pad. In further accordance with this particular aspect of the invention,
the ON and OFF touch-sensitive areas may be positioned side by side at the
left side of a horizontally oriented touch control bar graph device.
Briefly stated and in accordance with still another aspect of the
invention, the ON touch-sensitive area corresponds to a particular touch
switch touch pad and the de-energizing touch-sensitive area does not have
an individual touch pad, but rather bridges both the touch pad
corresponding to the ON touch-sensitive area and a touch pad of the touch
control bar graph device. Suitable decoding logic recognizes the condition
when the ON touch-sensitive area and the touch pad of the touch control
bar graph device are both touched at once, to disable the touch control
bar graph device.
Preferably, the OFF touch sensitive area is visually dominant compared to
the ON touch-sensitive area. The visual dominance may be achieved by size
and color.
In accordance with various other aspects of the invention, the touch
control bar graph devices may be horizontally or vertically oriented, and
the ON and OFF touch-sensitive areas may both be located at the same end
of the touch control bar graph device, or at opposite ends. It is
preferable that there be an indicator lamp for the ON touch sensitive area
to indicate when the touch control bar graph is enabled.
In a range surface unit control application, the touch control bar graph
devices have legends indicating values increasing from left to right in
the case of a horizontally oriented bar graph device, and from bottom to
top in the case of a vertically oriented bar graph device. The values
represent particular range surface unit heat settings such as low, medium
and high.
BRIEF DESCRIPTION OF THE DRAWINGS
While the novel features of the invention are set forth with particularity
in the appended claims, the invention, both as to organization and
content, will be better understood and appreciated, along with other
objects and features thereof, from the following detailed description
taken in conjunction with the drawings, in which:
FIG. 1 is a perspective view of a portion of an electric range including
bar graph type touch switch and display devices as the four surface unit
heat controls, an ON/OFF switch arrangement according to the present
invention being combined with each of the bar graph devices.
FIG. 2 is a greatly enlarged view of a single one of the controls of FIG.
1, and represents a preferred embodiment of the invention when touch
control bar graph device is horizontally oriented;
FIG. 3 is an alternative arrangement for a horizontally oriented touch
control bar graph device;
FIG. 4 is still another alternative arrangement for a horizontally oriented
touch control bar graph device;
FIG. 5 represents an arrangement which may be employed in combination with
a vertically oriented touch control bar graph device;
FIG. 6 represents a preferred embodiment of the invention where a
vertically oriented touch control bar graph device is employed;
FIG. 7 is another alternative embodiment of the invention for use in
combination with a vertically oriented touch control bar graph device;
FIG. 8 is an exploded perspective view of the device of FIG. 2, showing
details of construction not ordinarily visible to a user;
FIG. 9 is a sectional side view viewed from the right hand side of FIG. 8,
and further showing a subpanel and a block schematic representation of
circuit means forming part of the complete operative device;
FIG. 10 is a portion of a schematic diagram of a representative electrical
circuit suitable for operating in the embodiments of FIGS. 2, 8 and 9, and
more particularly the touch switch portion of the circuitry;
FIG. 11 is the decoding logic portion of the electrical circuit;
FIGS. 12 and 13 are schematic diagrams of an electrical circuit suitable
for generating signals to drive the display portion of the embodiments of
FIGS. 2, 8 and 9;
FIG. 14 is a schematic diagram of a representative electrical circuit for
receiving signals from the ON and the OFF touch switches; and
FIG. 15 shows circuitry suitable for driving the indicator lamps of FIGS. 8
and 9 to form a bar graph display.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring first to FIG. 1, an electric range 20 includes four conventional
electrical surface heating units 22, 24, 26, and 28. To provide user
control over the heat produced by the surface heating units, four
corresponding input/output devices 30, 32, 34 and 36 are disposed upon the
right hand portion of the range control panel 38, which is formed of
tempered glass approximately 3/16" thick for good appearance and
cleanability. As will be apparent from the physical arrangement of the
devices 30, 32, 34 and 36, the upper left input/output device 30 controls
the left rear surface heating unit 22, the upper right input/output device
32 controls the right rear surface heating unit 24, and so on.
Referring now to FIG. 2, there is shown a greatly enlarged view of
representative input/output device 30 as it appears to the user when a
"medium" heat setting for the left rear surface heating unit 22 has been
selected. The largest part of the device 30 is a horizontally oriented
touch control graph device 37 such as is disclosed in the Welch, Serrano
and Chen and in the Serrano applications referred to above. To indicate to
the user what heat setting has been selected, the touch control bar graph
device 37 has a lighted bar graph display 40 visible through a suitable
transparent window 42 in the panel 38. The bar graph display 40 actually
comprises a linear array 44 of nine individual display segments 46 through
54 which are strung out such that each segment is adjacent the no more
than two other segments. The segments are adapted to be progressively
energized to form the bar graph type display 40 representing a particular
value.
In order to provide a user input to the touch control bar graph device 37,
a linear array 56 of light transmitting touch sensitive areas 58 through
66 is superimposed over the array 44 of display segments. The individual
touch-sensitive areas 58 through 66 are delineated by line 68 through 77
forming left and right boundaries of the individual touch-sensitive areas.
The delineating lines 68 through 77 may be applied in any suitable manner
such as painting or silk screening. For ease of understanding a decoding
arrangement hereinafter described, the areas 58, 60, 62, 64 and 66 are
termed primary touch-sensitive areas, and the intermediate areas 59, 61,
63 and 65 are termed secondary touch-sensitive areas.
In accordance with the present invention, an ON touch-sensitive area 78 is
positioned adjacent to but spaced from the touch control bar graph device
37. More particularly, the ON touch-sensitive area 78 is positioned
adjacent to but spaced from the left end of the touch control bar graph
device 37. A de-energizing touch-sensitive area 80 is positioned in the
space between the on touch sensitive area 78 and the touch control bar
graph device 37. More particularly, in the particular embodiment
illustrated in FIG. 2, the de-energizing touch-sensitive area 80 is a
clearly designated off touch sensitive area 82.
Circuit means, hereinafter described in more detail, is responsive to the
ON touch-sensitive area 78 and to the de-energizing touch-sensitive area
80 (more particularly shown as the OFF touch-sensitive area 82) for
enabling operation of the touch control bar graph device 37 in response to
the touching of the ON touch-sensitive area 78 and for disabling operation
of the touch control bar graph device 37 in response to the touching of
the de-energizing touch-sensitive area 80.
For a user to activate the left rear surface unit 22 requires two
operations: First, a touch on the ON touch sensitive area 78, and second,
a touch on the touch control bar graph device 37. Any attempt by the user
to enable operation of the touch control bar graph 37 by moving a finger
between the ON touch sensitive area 78 and the touch control bar graph
device 37 in one continuous motion results in at least a momentary
touching of the OFF touch sensitive area 82, to disable the touch control
bar graph device 37.
To complete the input/output device 30 of FIG. 2, the touch control bar
graph device 37 has a plurality of legends 84 representing relative values
increasing from left to right. More particularly, the legends "LOW," "MED"
and "HIGH" represent range surface unit heat settings. The ON
touch-sensitive area 78 also has an indicator display lamp 86 which may be
similar to any one of the display segments 46 through 54 of the touch
control bar graph device 37. The indicator display lamp 86 is connected to
indicate when the touch control bar graph device 37 is enabled following
touching of the ON touch-sensitive area 78.
From FIG. 2 it will also be seen that the OFF touch-sensitive area 82 is
visually dominant compared to the ON touch sensitive area 78. In its
particular embodiment, this visual dominance is achieved by size, but
preferably the OFF touch sensitive area 82 is dominant compared to the ON
touch sensitive area 78 by color as well.
Referring now to FIG. 3, there is illustrated an alternative embodiment of
an ON/OFF touch switch arrangement for the horizontally oriented touch
control bar graph device 37. In FIG. 3, the ON touch-sensitive area 78 is
located at the left end of the touch control bar graph device 37, and the
OFF touch-sensitive area 82 is located at the right hand end of the touch
control bar graph device 37. It will be seen that the ON touch sensitive
area 78 is adjacent but spaced from the touch control bar graph device 37,
the space being designated 94. In this particular embodiment the ON
touch-sensitive area 78 corresponds to a particular touch switch touch
pad, and there is another touch switch touch pad associated with the left
end of the touch control bar graph device 37. A de-energizing touch
sensitive area bridges the touch pad corresponding to the ON
touch-sensitive area 90 and the touch pad of the touch control bar graph
device, over the space 94, such that a touch on the de-energizing
touch-sensitive area contacts both of the touch pads. Logic means similar
to that disclosed in the above-mentioned copending Serrano application
Ser. No. 908,317 recognizes the condition when both of these touch pads
are touched and generates a signal indicating the touching of the
de-energizing touch-sensitive area 94.
FIG. 4 depicts another ON/OFF switch arrangement for use in combination
with the horizontally oriented touch control bar graph device 37. In FIG.
4, the ON and OFF touch-sensitive areas 78 and 82 are positioned at the
left end of the touch control bar graph device 37, one above the other.
The ON touch-sensitive area 78 is spaced from the touch control bar graph
device 37, the space being designated 102. As in the FIG. 3 embodiment,
the ON touch-sensitive area 78 corresponds to a particular touch switch
touch pad, and a de-energizing touch-sensitive area over the space 102
bridges the touch pad corresponding to the ON touch-sensitive area 78 and
a touch pad of the touch control bar graph device 37.
Various embodiments of the invention may be used in combination with
vertically oriented touch control bar graph devices. In FIG. 5, ON and OFF
touch-sensitive areas 104 and 106 are positioned at the upper end of a
vertically oriented touch control bar graph device 108, the ON
touch-sensitive area 104 being spaced from the touch control bar graph
device 108 and the OFF touch-sensitive area 106 being positioned in the
space. The vertically oriented touch control bar graph device 108 also has
a plurality of legends 110 representing relative values increasing from
bottom to top. As before, the legends 110 may represent range surface unit
heat settings.
FIG. 6 represents a presently preferred embodiment of the invention where
the vertically oriented touch control bar graph device 108 is employed. In
FIG. 6, the OFF touch-sensitive area 106 is positioned at the lower end of
the touch control bar graph device 108, and the ON touch-sensitive area
104 is positioned adjacent to but spaced from the upper end of the touch
control bar graph device 108. The space 112 between the ON touch-sensitive
area 104 and the touch control bar graph device 108 represents the
approximate center of a de-energizing touch-sensitive area generated as
before, by simultaneous touches on a touch pad corresponding to the ON
touch-sensitive area 104 and a touch pad of the touch control bar graph
device 108.
FIG. 7 is comparable to the arrangement of FIG. 4, except that it is for
use in combination with the vertically oriented touch control bar graph
device 108.
Turning now to FIGS. 8 and 9, the underlying constructional details of the
representative input/output device 30 may be seen. FIG. 8 is an exploded
perspective view of the various elements associated most directly with the
glass panel 38, and FIG. 9 is a sectional right side view of the panel as
assembled, together with additional elements. The specific underlying
constructional details of FIGS. 8 and 9, as well as the exemplary circuits
which follow, do not themselves form a part of the invention claimed
herein, but merely represent one way of implementing the invention. It
will be recognized that various aspects of the constructional details and
of the circuitry are disclosed in the above-mentioned copending Welch,
Serrano and Chen and Serrano applications.
Disposed on the front side of the panel 38 are seven transparent touch pads
120 through 126 which comprise the input elements of capacitive touch
switches generally designated 128 through 134. It will be apparent that
the thicknesses of the touch pads 120 through 126 are greatly exaggerated
for clarity of illustration.
To complete the touch switches 128 through 134, conductive rear pads,
generally designated 136, are disposed on the rear side of the panel 38.
More specifically, individual transmitter pads 138, 140 and 142 are
provided for the touch switches 131, 132, and 133, respectively. A single
split transmitter pad 144 having portions 144a and 144b serves both the
touch switches 129 and 130, and another split pad 146 having portions 146a
and 146b serves the touch switches 128 and 134. A single receiver pad 148
serves the five touch switches 130 through 134 through a multiplexing
arrangement hereinafter described. The "ON" and "OFF" touch switches 128
and 129 similarly share a receiver pad 150. It will be seen that each of
the rear pads 136 forms a capacitor with at least one of the touch pads
disposed on the front side of the panel 38.
In the particular arrangement illustrated, the rear pads 136 need not be
transparent and therefore may be made of any suitble conductive material,
such as metallic silver or copper. In order to conceal the rear pads 136
from view for a pleasing appearance, a layer 152 of black paint (FIG. 9)
is applied to the rear side of the panel 38, underneath the rear pads 136,
the window 42 being defined by a suitable break in the paint layer 152.
The nature of the conductive touch pads 120 through 126 is such that are
not readily visible to the casual observer, but are discernible only upon
close examination. However, the painted lines delineating the individual
touch sensitive areas 58 through 66 and the "ON" and "OFF" touch-sensitive
areas 78 and 82 are readily visible and, in conjunction with the visible
outline of the window 42, guide a person's touch.
To facilitate electrical connection between the rear pads 136 and a circuit
means 156, an electrically insulating subpanel 158 (FIG. 9) is mounted
behind and spaced from the rear panel 38. The subpanel 158 carries
suitable spring contact clips such as the clips 160 and 162 which contact
the rear pads 136. Representative transmitter (T) and receiver (R)
conductors 164 and 166 connect the spring contact clips 160 and 162 to the
circuit means 156.
The subpanel 158 additionally carries the individual display segments 46
through 54 comprising the array 44. In FIG. 9, the representative display
segment 54 is joined to the subpanel 158 at 167 by any suitable means such
as by gluing. In FIGS. 8 and 9, each of the individual display segments 46
through 54 may be seen to comprise a neon lamp 168 mounted in a suitable
red plastic light dispersing lens element. The lens elements are
preferably rectangular when viewed from the front thereof, and have
suitable light scattering surface roughness so as to produce a solid block
of light when the neon bulbs 168 are energized. To complete the mechanical
arrangement, conductors 170 and 172 connect the electrodes of the
representative neon lamp 168 in FIG. 9 to the circuit means 156.
The indicator display lamp 86 for the "ON" touch-sensitive area 78 is
similar to the display segments 46 through 54. The display 86 is
positioned behind a window 174, similar to the window 42, so as to be
visible through the "ON" touch pad 120.
In the operation of the representative input/output device 30, the touch
control bar graph device 37 is initially disabled such that the ultimate
load device, for example the surface unit 22, is not energized. If a user
merely touches the touch control bar graph device 37 while it is in the
disabled condition, preferably the touch control bar graph device 37 does
not respond, and in any event the ultimate load device is not energized.
When the user touches the ON touch-sensitive area 78, the circuit means 156
responds to enable the touch control bar graph device 37. Additionally,
the display lamp 86 indicates the enabled condition. Thereafter, when a
user touches any one of the individual touch sensitive areas 58 through
66, the circuit means 156 responds to properly drive the display array 44
to form a bar graph. Additionally, the circuit means 156 sends suitable
signals to external circuitry (not shown) to cause the appropriate control
function, for example establishing a desired heat setting, to be
accomplished. This operation is described in greater detail in the
above-mentioned Serrano application, Ser. No. 908,317.
To briefly summarize, decoding logic (described later with particular
reference to FIG. 11) within the circuit means 156 is arranged such that
when any single one of the touch pads 122 through 126 is touched, an
output signal representing a corresponding primary touch-sensitive area
58, 60, 62, 64 or 66 is produced. When any two adjacent touch pads are
simultaneously touched, an output signal representing a secondary
touch-sensitive area 59, 61, 63 or 65 associated with the two touch pads
is generated. The different signals thus generated by the decoding logic
are applied to a means (described hereinafter with particular reference to
FIGS. 10-15) for energizing the display segments 46 through 54 to produce
the bar graph display.
At any time, the user can disable the touch control bar graph device 37 and
thus de-energize the load by touching the OFF touch-sensitive area 80.
As previously mentioned, the arrangement requires two user operations to
enable the touch control bar graph device 37 and energize the load device.
Any attempt to enable operation of the device 37 by moving a finger
directly between the ON touch-sensitive area 78 and the touch contol bar
graph device 37 in one continuous motion results in at least a momentary
touching of the OFF touch sensitive area 82.
While FIGS. 8 and 9 illustrate details of the FIG. 2 embodiment only, it
will be appreciated that the embodiments of FIGS. 3-7 may similarly be
constructed. In FIGS. 2 and 8 the ON and OFF touch-sensitive areas 78 and
82 each correspond to a particular touch switch touch pad. Specifically,
the ON touch-sensitive area 78 corresponds to the touch pad 120 of the
touch switch 128, and the OFF touch-sensitive area 82 corresponds to the
touch pad 121 of the touch switch 129. However, as is taught in the
above-referenced Serrano application Ser. No. 908,317, there need not be a
one-for-one correspondence between touch-sensitive areas and touch pads.
In particular there may be more touch-sensitive areas than touch pads,
with logic circuitry being employed to respond to a simultaneous touching
of two adjacent touch pads and to generate an output indicative of this
condition. For example, in the FIG. 3 embodiment, the de-energizing
touch-sensitive area positioned over the space 94 does not correspond to a
particular touch switch touch pad, but rather is recognized by a
simultaneous touching of adjacent touch pads.
Referring now to FIGS. 10-15, one example of suitable circuitry for
operating the input/output device 30 of FIGS. 2, 8 and 9 will be
described. It will be appreciated, however, that similar circuitry may be
employed to operate the embodiments of FIGS. 3-7. It will be further
appreciated that the circuitry illustrated and described is exemplary only
and that many different schemes are possible, including microprocessor
based systems executing a sequence of instructions stored in a program
memory.
In FIG. 10, the rear transmitter pads 138, 140, 142, 144 and 146 of FIG. 8
are represented, along with suitable circuitry for driving the transmitter
pads. Similarly, the rear receiver pads 148 and 150 are represented along
with suitable circuitry connected to receive the outputs therefrom. The
front touch pads 120 through 126 visible in FIG. 8 are not shown in FIG.
10.
In contrast to the touch switch transmitter and receiver circuitry of the
copending Welch. Serrano and Chen application Ser. No. 750,559 now U.S.
Pat. No. 4,121,204 which uses individual channels for each of the touch
switches therein, the embodiment described herein uses a multiplexing
technique which requires significantly fewer electrical connections
between the circuitry itself and the rear pads 136. However, as previously
stated, the specific circuitry described herein is exemplary only and
specific circuit details, including the multiplexing arrangement, are not
a part of the invention claimed herein.
The digital logic elements employed herein are of two families: CMOS and
TTL. The CMOS logic may comprise elements selected from the CD-4000 series
of integrated circuits manufactured by RCA Corporation, and the TTL logic
elements may comprise SN7400 series integrated circuits manufactured by
Texas Instruments, Inc.
Considering specifically the transmitter circuitry of FIG. 10, a five-phase
clock, generally designated 190, comprises a suitable square wave
oscillator 192 operating on a frequency of approximately 100 KHz, and a
pair of serially connected five-bit shift register 194 and 196 with their
clock (CK) inputs driven by the clock oscillator 192. The five-bit shift
registers 194 and 196 may comprise SN7496 TTL IC's. To prevent overlapping
outputs, every other shift register output along the chain is taken to
provide the five clock phase outputs. Specifically, from the first
five-bit shift register 194, the Q.sub.A output drives the .PHI.1 line,
the Q.sub.C output drives the .PHI.2 line, and the Q.sub.E output drives
the .PHI.3 line. From the second five-bit shift register 196, the Q.sub.B
output drives the .PHI.4 line and the Q.sub.D output drives the .PHI.5
line. The Serial Input (SI) of the first shift register 194 receives the
output of a nine input, low-activated AND gate 198 having its inputs
connected to the Q.sub.A through Q.sub.E outputs of the first shift
register 194 and the Q.sub.A through Q.sub.D outputs of the second shift
register 196.
The logical equivalent of the low-activated AND gate 198 may be constructed
from three SN7427 TTL 3-input NOR gates supplying the inputs of an SN7410
TTL 3-input NAND gate followed by an SN7404 TTL inverter.
In the operation of the five-phase clock 190, logic highs are applied to
the serial input (SI) of the first shift register 194 and clocked through
in response to pulses from the clock oscillator 192 to successively appear
at each of the Q outputs. Upon initial powering up of the circuit, the
output of the AND gate 198 remains low, and this low applied to the first
shift register 194 SI input causes all the shift register stages to
eventually be cleared to logic low in response to clock pulses. When all
the Q outputs are low, the output of the low-activated AND gate 198 goes
high, inserting a logic high into the A stage of the first shift register
194, and this logic high is then clocked through in response to clock
pulses.
The five clock lines are applied to the inputs of five transmitter pad
drivers 200 through 204, which have their outputs connected to the
transmitter pads 144, 138, 140, 142 and 146. The drivers 200 through 204
have high voltage transistor outputs, and provide approximately 160 volts
to the transmitter pads.
The common receiver pad 144 is connected to a high impedance input
inverter/buffer amplifier 206, and the receiver pad 150 for the ON and OFF
switches to another high impedance input/inverter/buffer amplifier 207.
Both inverters 206 and 207 may comprise CD4049 CMOS IC's. A demultiplexing
network 208 comprises five NAND gates 210 through 214, each of which has
its upper input connected to the output of the common buffer amplifier 206
and its lower input connected to one of the clock lines .PHI.1 through
.PHI.5. For the "ON" and "OFF" touch switches, another NAND gate 215 has
its upper input connected to the output of the inverter 207, and its lower
input to the clock phase line .PHI.5. The NAND gates 210 through 215 may
comprise CD4011 CMOS NAND gates.
In the operation of the de-multiplexing network 208, each of the NAND gates
is interrogated in sequence by a logic high on the corresponding one of
the clock lines .PHI.1 through .PHI.5. If the corresponding touch pad is
not touched, the logic high present on the corresponding transmitter pad
is capacitively coupled to the common receiver pad 148, changed to logic
low by the inverter 206, and applied to the upper input of the
corresponding one of the NAND gates 210 through 214. The NAND gate is not
activated and its output therefore remains high. If, however, one or more
of the touch pads is touched, then the logic high applied to the receiver
pad in response to the particular clock phase is shunted by the touch. The
receiver pad 148 goes low. The resultant logic high at the output of the
inverter 206 applied to the upper input of the corresponding NAND gate of
the demultiplexing network 208 in coincidence with a logic high from the
particular clock phase line causes the output of the NAND gate of the
demultiplexing network 208 to go low, indicating that the corresponding
touch switch has been activated. The NAND gates 215 and 210 for the "ON"
and "OFF" touch switches operate similarly.
The outpts of the NAND gates 210 through 215 are applied through first and
second sets of buffers 216 and 218 to effect CMOS to TTL conversion. The
first buffers 216 may be type CD4050 CMOS buffers, and the second buffers
218 may be type SN7407 TTL buffer amplifiers. Suitable output pull up
resistors are required.
To enhance noise immunity, the outputs of the buffers 218 are followed by a
set of pulse stretchers 220. Each of the pulse stretchers 220 may comprise
for example a type SN74123 TTL retriggerable monostable multivibrator,
with suitable external resistance and compacitance to provide an output
pulse of 30 microseconds duration when triggered. To provide low-active
inputs and low active outputs of the pulse stretchers 220, the "A" inputs
and the Q outpts of the SN74123 IC's are used.
The output lines of the pulse stretchers 220 are designated OFF and A
through E. Each of these lines goes low when the corresponding one of the
touch switches 128 through 134 (FIG. 8) is touched.
The A through E outputs of the circuit of FIG. 10 are applied to the inputs
of the circuit of FIG. 11. In particular, FIG. 11 illustrates decoding
logic 222 for generating different outputs in response to the t | | |
