U.S. patent number 3,573,788 [Application Number 04/758,378] was granted by the patent office on 1971-04-06 for means to vary the intensity of illumination of electroluminescent display segments.
This patent grant is currently assigned to The Bendix Corporation. Invention is credited to Robert J. Molnar, Walter Parfomak.
United States Patent |
3,573,788 |
Molnar , et al. |
April 6, 1971 |
MEANS TO VARY THE INTENSITY OF ILLUMINATION OF ELECTROLUMINESCENT
DISPLAY SEGMENTS
Abstract
Means for controlling an alternating current selectively applied
to energize a plurality of electroluminescent segments so as to
vary the intensity of illumination of the selectively energized
electroluminescent display segments.
Inventors: |
Molnar; Robert J. (New York,
NY), Parfomak; Walter (Wallington, NJ) |
Assignee: |
The Bendix Corporation
(N/A)
|
Family
ID: |
27064927 |
Appl.
No.: |
04/758,378 |
Filed: |
September 9, 1968 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
535745 |
Mar 21, 1966 |
3440637 |
Apr 22, 1969 |
|
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Current U.S.
Class: |
345/36;
345/690 |
Current CPC
Class: |
G01R
13/405 (20130101) |
Current International
Class: |
G01R
13/00 (20060101); G01R 13/40 (20060101); G01d
007/00 (); G09b 009/32 () |
Field of
Search: |
;340/324,335,334,339,336
;313/108 ;315/163,164,169,170,176 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Caldwell; John W.
Assistant Examiner: Curtis; Marshall M.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application is a division of a copending U.S.
application Ser. No. 535,745, filed Mar. 21, 1966, and now U.S.
Pat. No. 3,440,637 granted Apr. 22, 1969 to Robert J. Molnar and
Walter Parfomak for a Solid State Display with Electronic Drive
Circuitry.
Claims
We claim:
1. For use with a condition sensor of a type including means for
effecting an output signal proportional to a sensed condition, the
combination comprising a plurality of electroluminescent display
segments including opposite capacitive-type plates, a first source
of alternating current, means response to said output signal to
selectively connect said source of alternating current across the
opposite capacitive-type plates of said display segments to
illuminate said segments so as to provide a variable length
luminous display indicative of the sensed condition, a second
source of direct current biasing voltage, the means for selectively
connecting said source of alternating current across the opposite
capacitive-type plates of said display segments including first
unidirectional current flow control means connecting one phase of
said alternating current in a series opposing relation with said
direct current biasing voltage of said second source, and a second
unidirectional current flow control means for connecting an
opposite phase of said alternating current in an opposite series
opposing relation with said direct current biasing voltage of said
second source, said second source of direct current biasing voltage
being connected in a back biasing relation to said first and second
unidirectional current flow control means and in opposition to the
first and second phases of said alternating current applied through
said first and second unidirectional current flow control means
across the opposite capacitive-type plates of said display
segments, and operator-operative means for adjusting the direct
current biasing voltage of said second source to vary intensity of
illumination of the electroluminescent display segments by the
alternating current of said first source.
2. The combination defined by claim 1 in which the selective
connecting means includes a bridge network, the first and
unidirectional current flow control means being arranged in
opposite arms of said bridge network, a first pair of input legs
being connected between opposite arms of the bridge network, said
first input legs being serially connected in the means connecting
said source of alternating current across the opposite
capacitive-type plates of said display segments, and a second pair
of input legs being connected between other opposite arms of the
bridge network for connecting the second source of direct current
biasing voltage across the first and second unidirectional current
flow control means in such a polarity sense as to apply an
electromotive force in a back biasing relation to said first and
second unidirectional current flow control means and acting in
opposing relation to the first source of alternating current, and
operator-operative means for adjusting the second source of direct
current voltage so as to vary the electromotive force acting in
said opposing relation and thereby the intensity of the
illumination of the electroluminescent display segments by the
first source of alternating current applied through said bridge
network and across the opposite capacitive-type plates of said
display segments.
3. The combination defined by claim 1 in which the selective
connecting means includes a diode bridge means, the first
unidirectional current flow control means including a first pair of
diodes connected in opposite arms of said bridge means in one like
polarity sense, said second unidirectional current flow control
means including a second pair of diodes connected in other opposite
arms of said bridge means in another opposite polarity sense from
said first pair of diodes, said first and second pairs of diodes
being connected in said bridge means in said one and other polarity
senses for connecting said one and other phases of said first
source of alternating current in said series opposing relation to
said second source of direct current voltage and across said
opposite capacitive-type plates of said display segments, an
adjustable potentiometer connected across said second source of
direct current voltage and operatively connected across opposite
arms of the diode bridge means to apply the back biasing voltage to
the first and second pairs of diodes of the diode bridge means to
block passage of a portion of the alternating current applied
through the diode bridge means and across the opposite
capacitive-type plates of the selectively connected display
segments to thereby vary the intensity of illumination of the
selectively illuminated electroluminescent display segments.
4. For use with a condition sensor of a type including means for
effecting an output signal proportional to a sensed condition, the
combination comprising a plurality of electroluminescent display
segments, each of said segments including opposite conductive
layers, a source of alternating current, means responsive to said
output signal to selectively connect said source of alternating
current across the opposite conductive layers of said display
segments to illuminate said segments so as to provide a variable
length luminous display indicative of the sensed condition, a
bridge network, a first control junction on the bridge network, the
bridge network including a first pair of unidirectional current
flow control devices for permitting flow of current from the first
control junction of the bridge network to opposite input-output
junctions of the bridge network, a second control junction on the
bridge network, the bridge network including a second pair of
unidirectional current flow control devices for permitting flow of
current to the second control junction of the bridge network from
the opposite input-output junctions of the bridge network, means
serially connecting the opposite input-output junctions of the
bridge network between the source of alternating current and the
means to selectively connect said source of alternating current
across the opposite conductive layers of said display segments, a
direct current voltage source, means connecting the direct current
voltage source across said first and second control junctions in a
polarity sense to back bias the unidirectional current flow control
devices in opposite relation to the unidirectional flow of current
therethrough by the alternating current source so as to block
passage of at least a portion of the alternating current applied by
the alternating current source and permit passage through the
bridge network of that portion of the alternating current which
effectively overcomes the biasing voltage of the direct current
voltage source and thereby control intensity of illumination of the
selectively illuminated electroluminescent segments.
5. The combination defined by claim 4 including a potentiometer
having a resistor element connected across said source of direct
current voltage, the means connecting the direct current voltage
source across said first and second control junctions of the bridge
network including an adjustably positioned control arm
cooperatively arranged in relation to said resistor element so as
to provide first and second portions of said resistor element, each
of said portions of the resistor element being variable relative
one to the other by the positioning of the control arm, and an
operator-operative control to vary the position of the control arm
and the effective resistance of said portions of the resistor
element relative one to the other and thereby provide a variable
voltage divider permitting a variable biasing voltage to be derived
and applied by the direct current voltage source across the first
and second control junctions so that the portion of the alternating
current which effectively overcomes the derived biasing voltage
applied by the direct current voltage source may effect a flow of
current through the second pair of unidirectional current flow
control devices to the second control junction of the bridge
network and through at least one of said portions of the resistor
element of the potentiometer to the first control junction of the
bridge network and selectively through the first pair of
unidirectional current flow control devices to the output of
alternating input-output junctions of the bridge network.
Description
The present invention is directed to a means to vary the
intensitive of illumination of a plurality of selectively
illuminated electroluminescent display segments as described and
claimed herein with reference to the dimming control of FIG. 4. The
pulse responsive control network described herein is the subject
matter of a U.S. application Ser. No. 758,946 filed Sept. 11, 1968
by Robert J. Molnar and Walter Parfomak as another division of the
U.S. application Ser. No. 535,745 filed Mar. 21, 1966, and which
last mentioned application was in turn filed as a
continuation-in-part as to all common subject matter of a now
abandoned U.S. application Ser. No. 467,391, filed Jun. 28, 1965 by
Robert J. Molnar and Walter Parfomak for a Solid State Display with
Electronic Drive Circuitry.
The solid state display system to which the present invention may
be applied may include a condition sensor, comparator, drive
circuitry, driven step integrator network and feedback summation
network for driving a plurality of electroluminescent display
segments.
In such a display system the condition sensor may, for example,
include: (1) a thermocouple of a type arranged to provide an analog
direct current signal corresponding to a sensed temperature
condition; or (2) the condition sensor may be of a fuel flow
synchro sensing type which may necessitate the use of a converter
such as described and claimed in a U.S. Pat. No. 3,375,508, granted
Mar. 26, 1968, to Robert J. Molnar and Walter Parfomak, the
inventors of the present invention.
Further, the comparator provided in the system may be of a type
described and claimed in a U.S. Pat. No. 3,363,112 granted Jan. 9,
1968, to Robert J. Molnar and Walter Parfomak, the inventors of the
present invention.
Moreover, the electronic drive circuitry utilized in the system may
be of a type described and claimed in a U.S. Pat. No. 3,333,114
granted Jul. 25, 1967, to Robert J. Molnar and Walter Parfomak, the
inventors of the present invention.
Furthermore, there may be provided in the drive circuitry a control
circuit and electronic step integrator of a type described and
claimed in a U.S. Pat. No. 3,427,609 granted Feb. 11, 1969 on a
copending U.S. application Ser. No. 411,803, filed Nov. 17, 1964 by
Robert J. Molnar and Walter Parfomak, the inventors of the present
invention. All of the foregoing applications and patents have been
assigned to The Bendix Corporation, the assignee of the present
invention.
As distinguished from the foregoing features, the present invention
is directed to a means for adjusting an alternating current for
energizing the plurality of electroluminescent display segments so
as to vary the intensity of illumination of the display segments as
more specifically described and claimed herein with reference to
FIG. 4.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is in the field of solid state display with
electronic drive circuitry and, more particularly, to an improved
control network including means for adjusting an alternating
current for energizing a plurality of selectively illuminated
electroluminescent display segments so as to vary the intensity of
illumination thereof.
2. Description of the Prior Art
Heretofore, solid state display systems have been provided
including means for controlling the illumination of a stack of
electroluminescent segments which may be of a type similar to that
of the electroluminescent segments disclosed in a U.S. Reissue Pat.
No. 26,207, granted May 23, 1967 to Frederick Blancke Sylvander and
assigned to The Bendix Corporation, assignee of the present
invention.
In the display system of the U.S. Reissue Pat. No. 26,207, and in
the arrangement of the present invention, the electroluminescent
segments are of a type having thin films of phosphor material
sandwiched or positioned immediately between two electrical
conductive layers one or both of which may be transparent. In such
an arrangement, each electroluminescent layer is essentially a
capacitor which is so arranged that upon the application of an
alternating current voltage across the outer conductive layers, the
phosphor material will emit light, as heretofore explained in the
aforenoted U.S. Reissue Pat. No. 26,207, while upon a direct
current voltage being applied thereto, the capacitor effect of the
electroluminescent segment serves to block the passage of the
direct current therethrough so that no light is emitted from such
electroluminescent segment.
In the present invention, the specific control network for the
stack of electroluminescent display segments is quite different
from that disclosed in the U.S. Reissue Pat. No. 26,207, in that in
addition to the provision of a means responsive to an output signal
proportional to a sensed condition to selectively operate a control
network so as to connect a source of alternating current to said
display segments to effectively illuminate said segments so as to
provide a variable length luminous display column indicative of the
sensed condition, there is further provided in the present
invention an operator-operative means, as shown fails detail by
FIG. 4, for adjusting the alternating current from said source so
as to vary the intensity of the illumination of the
electroluminescent display segments and thereby enable the operator
to better distinguish the variable length display column under
different operating conditions of ambient illumination. The prior
art fails to suggest the simplified control network of the present
invention for adjusting the alternating current so as to vary the
intensity of the illumination of the plurality of
electroluminescent display segments selectively connected thereto
through the control network.
SUMMARY OF THE INVENTION
The invention contemplates an improved network from controlling the
intensity of illumination of a stack of electroluminescent display
segments selectively energized from a source of alternating
current.
Another object of the invention is to provide a means for
controlling the illumination of a stack of electroluminescent
display segments including a back biased diode bridge network in
series with a source of alternating current, and means for
effecting selective energization of the segments, together with a
variable direct current supply voltage to back bias the diode
bridge so as to control the effective alternating current applied
across opposite conductive layers of the stack of
electroluminescent segments to in turn vary the intensity of
illumination of a luminous display column.
Another object of the invention is to provide a diode bridge
network arranged to limit the passage of alternating current
therethrough so as to effect illumination of the electroluminescent
display segments with only that portion of the alternating current
of a voltage greater than a back biasing direct current voltage,
set by adjustment of an operator-operative potentiometer, so as to
provide a precise control of the intensity of illumination of the
electroluminescent display column regardless of the number of
electroluminescent segments that may be selectively activated.
A further object of the invention is to provide a stack of
electroluminescent segments connected in series with a blocking
diode bridge network, a source of alternating current, and means to
connect the source of alternating current through the blocking
diode bridge network so as to selectively illuminate the segments,
the blocking diode bridge network including a control potentiometer
to vary a back biasing direct current voltage applied to the diodes
of the bridge network so that the alternating current supplied
across the electroluminescent segments may be varied to reduce or
increase the brightness of illumination of the selectively
energized electroluminescent display segments.
These and other objects and advantages of the invention are pointed
out in the following description in the terms of the embodiment
thereof which is shown in the accompanying drawings.
IN THE DRAWINGS
FIG. 1 shows a block diagram of an electroluminescent
photoconductor solid state display system embodying the
invention.
FIG. 2 is a symbolic representation of the electroluminescent
photoconductor matrix in a novel layout arrangement for indicating
coarse, fine, and sectional controls in driving the
electroluminescent display segments.
FIG. 3 shows an enlarged detailed fragmentary schematic view of the
electroluminescent photoconductor matrix shown in FIG. 2, as
attached to the electroluminescent display segments for
illuminating the same.
FIG. 4 is a detailed circuitry of the dimming circuit shown in FIG.
1.
DESCRIPTION OF THE INVENTION
The electroluminescent photoconductor solid state display system
comprises an indicator panel and a driven network utilizing a novel
optoelectronic approach. A condition sensor device is provided to
obtain from analog signals such as exhaust gas temperature, fuel
flow or a tachometer, a direct current analog signal to control a
comparator circuit and in turn an electronic drive circuitry to
effect a corresponding control of a driven network including
electroluminescent segments arranged in an instrument simulating a
thermometer type moving display.
More specifically the condition sensor means used may, for example,
be: (1) a thermocouple of a type arranged to provide an analog
direct current signal corresponding to a sensed temperature
condition; or (2) the condition sensor means may be of a fuel flow
synchro signal sensing type which may necessitate the use of a
converter such as described in U.S. Pat. No. 3,375,508, granted
Mar. 26, 1968 to Robert J. Molnar et al., assigned to The Bendix
Corporation, the same assignee as the present invention; or (3) the
condition sensor means may be tachometer signal sensing means of a
type in which tachometer signals are converted to produce one pulse
per cycle of a generator speed and in which the amplitude and width
of the pulses are controlled so that a filtered output produces a
direct current analog signal which is an accurate function of the
sensed condition or tachometer speed.
Referring to the drawing of FIG. 1, there is indicated a block
diagram of the system. A condition sensor 210 provides a direct
current analog signal corresponding to the sensed condition which
is directed, as shown by arrow 211, to an electronic error
detector, such as, a comparator 216, which may be analogous to a
differential in an electromechanical system. The comparator 216 may
be of the type described and claimed in the aforenoted U.S. Pat.
No. 3,363,112, granted Jan. 9, 1968 to Robert J. Molnar and Walter
Parfomak for a single transistorized comparator circuit and
assigned to The Bendix Corporation, the assignee of the present
invention.
An electronic drive circuitry 218 which may be of a type described
and claimed in the aforenoted U.S. Pat. No. 3,333,114, granted Jul.
25,1967 to Robert Molnar and Walter Parfomak for an electronic
drive circuit and assigned to The Bendix Corporation, may include
as shown by FIG. 5, a control circuit 219 which receives the
differential output signal, as shown by arrow 215, from the
comparator 216. The control circuit 219 in turn controls the
operation of the drive circuit 218 in applying driving pulses, as
shown by arrow 217 of FIG. 1, to a driven network 221.
The driven network 221, under control of the driving pulses applies
electrical pulses, as indicated by the arrow 223 of FIG. 1, to
regulate the operation of the electroluminescent matrix 220.
Further, a summation network 222 receives electrical signal
information, as shown by arrow 225, from the driven network 221 and
directs a feedback signal, as indicated by the arrow 227, to the
comparator 218 corresponding to the regulated condition of the
matrix 220.
More specifically, as described and claimed in the aforenoted U.S.
Pat. No. 3,440,637, the driven network 221 directs signal
information corresponding to the regulated operation of the
electroluminescent capacitor strips extending along the X axis and
Y axis of the matrix 220, while the summation network 222 then
integrates the information signal until the direct current feedback
signal voltage directed to the comparator 216 from the summation
network 222, as shown by an arrow 227 of FIG. 1, is equal to the
direct current analog signal voltage directed to the comparator 216
from the condition sensor 210, as shown by the arrow 221. That is,
the DC feedback signal voltage acts in opposition to the DC analog
signal voltage so that when the resulting differential or error
signal voltage is reduced to zero, the integration is
accomplished.
Electroluminescent Matrix
It should be also noted at this time that, as described and claimed
in the U.S. Pat. No. 3,440,637, the multisegment switching of the
electroluminescent display portion of the invention requires three
orders of control including a fine control, a coarse control, and a
third order of control achieved by photoconductor switches 224
being arranged to receive light from the electroluminescent
capacitor strips F1 to F10 of the electroluminescent matrix 220, as
shown by arrows 229 of FIG. 1.
A last row of Y axis extending photocells are provided to control
the excitation of each succeeding row of X axis extending
photocells in which the first row of X axis extending photocells
does not require such control since it is excited continuously.
The electroluminescent matrix 220 of FIG. 1 is shown symbolically
in FIG. 2, partially in schematic form in FIG. 3 and in detail in
the U.S. Pat. No. 3,440,637.
In addition, the photoconductor switches 224, shown in the block
diagram of FIG. 1, are also shown symbolically in FIG. 2, partially
in FIGS. 3 and 4, and in detail in the U.S. Pat. No. 3,440,637.
An electroluminescent display column made up of a series of
electroluminescent display segments 226, shown in FIG. 1, is
connected to be energized by the electroluminescent matrix 220 and
the photoconductor switches 224, as shown by arrows 229 and 230,
respectively. The electroluminescent display segments 226 are shown
symbolically in FIG. 2 and partially schematically in FIGS. 3, and
4, and in the U.S. Pat. No. 3,440,637. The electroluminescent
display segments 226 are described more fully in the aforementioned
U.S. Reissue Pat. No. 26,207.
A dimming circuit 228, providing means for dimming the
electroluminescent display 226 by manual control, is shown in FIG.
1 connected to the system by a line 231. The dimming circuit 228 is
more specifically shown in FIG. 4, as including a back biased diode
bridge in series with the ground leg of the electroluminescent
display section, as hereinafter more fully described.
As shown symbolically in FIG. 2 and in detail in the U.S. Pat. No.
3,440,637, the electroluminescent matrix 220 is optically coupled
to the photoconductor switches 224 to form an electroluminescent
photoconductor matrix 234. The electroluminescent photoconductor
matrix 234 may, for example, comprise 209 photoconductor switches
indicated by numerals PC1 to PC209, a coarse electroluminescent
control 236 including 19 electroluminescent capacitor strips C1 to
C19, extending along the X axis, a fine electroluminescent control
238 including 10 electroluminescent capacitor strips F1 to F10,
extending along the Y axis with a symbolic F11 to show the last
fine control, and a sectional control 240 which includes 19
sectional photoconductor switches S1 to S19, which are rendered
conductive upon illumination of the associated coarse control
electroluminescent capacitor strips C1 to C19.
The electroluminescent photoconductor matrix 234 symbolically
shows, in FIG. 2, 209 squares representing the 209 photoconductor
switches providing driving or switching means for the 209
electroluminescent display segments 226 numbered EL1 to EL209. It
should be noted that each photoconductor switch PC1 to PC209 drives
its correspondingly numbered electroluminescent segment, and in
this sense are correlated one to the other. It should be also noted
that FIG. 2 symbolically shows at 226 an example of 36 activated
electroluminescent segments which are driven by 36 photoconductor
switches PC1 to PC36.
The interconnection of the photoconductor switches 224 with their
corresponding electroluminescent display segments 226 is shown in
more detail in FIG. 3 wherein the electroluminescent segments 226
are controlled by the photoconductor switches 224 through the fine
electroluminescent switching means 238 controlled by silicon
controlled rectifier switches, as described and claimed in the U.S.
Pat. No. 3,440,637, and which control the energization of the 10
electroluminescent strips F1 to F10. In addition, the coarse
switching means 236 is controlled by other silicon controlled
rectifier switches which control the energization of the 19
electroluminescent strips C1 to c19, as described and claimed in
the U.S. Pat. No. 3,440,637
Therefore, as shown in FIG. 3, the electroluminescent
photoconductor matrix 234 illuminates 209 photoconductor switches
PC1 to PC209 through the electroluminescent strips F1 to F10 and C1
to C19 controlled by the silicon controlled rectifier switches
which are operatively controlled by the driven network 221.
It should be noted that FIG. 3 is a fragmentary drawing of the
electronic circuitry to show the connection between the silicon
controlled rectifier switches energizing the electroluminescent
strips and that the U.S. Pat. No. 3,440,637 shows in greater detail
the silicon controlled rectifier electronic circuitry utilized in
the solid state display circuitry to drive the optoelectric portion
of the system. That is the electronic circuitry which operates to
energize the 19 electroluminescent coarse control strips C1 to C19
extending in the X axis and the 10 electroluminescent fine control
strips F1 to F10 extending in the Y axis of the electroluminescent
photoconductor matrix 234 to provide thereby two orders of control
to illuminate the electroluminescent display segments 226. However,
as hereinbefore described, and as shown in FIGS. 2 and 3,
multisegment switching of the electroluminescent display 226
requires three orders of control. This third order of control is
effected by providing photoconductor switches S1 to S19 of the
sectional control 240 each of which sectional control switches
corresponds to one of the photoconductors such as the last
photoconductor in each row PC11, PC22, PC33, and so on up to the
last photoconductor PC198 located on the next to the last row of
photoconductors. These photoconductors, PC11, PC22, PC33, and so on
to PC198 corresponding to the sectional control switches S1 to S19,
respectively, are the last photoconductors on each of the
electroluminescent strips extending on the X axis from C1 to C18
except for the last electroluminescent strip C19. The last
photoconductor PC209 may be utilized as an additional section
control switch in the event more than 209 electroluminescent
display segments were to be illuminated.
In this system the photoconductors S1 to S18 of the sectional
control 240 are used to control the excitation for the next row of
photoconductors extending on the X axis. For example, as shown
schematically in FIG. 3, the photoconductor PC11 corresponding to
the sectional control switch S1 is used as a stand-by power switch
for the second row of photoconductors, PC12 to PC22.
More specifically, as shown in FIG. 3, photoconductor PC11
corresponding to sectional control switch S1 is connected through
line conductors 242 and 250 to one terminal of a suitable source of
alternating current 243. The other terminal of the source 243 is
connected by a line conductor 244 to a ground 245. The
photoconductor PC11 is also connected by a line conductor 246 to
electroluminescent segment EL11 and in turn the electroluminescent
EL11 is connected to ground 245 by a common line conductor 248. In
addition, the line conductor 250 connects the row of
photoconductors PC1 to PC11. When the electroluminescent strip C1
is illuminated, light rays are directed thereby upon the
photoconductors PC1 to PC11 to reduce their electrical resistance
and render them conductive of electrical energy, whereupon voltage
from the alternating current source 243 will be applied through
photoconductor PC11 corresponding to the sectional control switch
S1 to the photoconductors PC12 to PC22 through a line conductor
252. Thereafter, should the fine control electroluminescent strips
F1 to F10 be illuminated, then the photoconductors PC11 to PC21
would be rendered conductive; or, should the coarse control
electroluminescent strip C2 be illuminated, then the
photoconductors PC11 to PC22 would become electrically conductive
and current would be directed to the electroluminescent segments
EL12 to EL22 for illuminating segments of the electroluminescent
display 226. That is, when the photoconductor PC11 is switched on
to illuminate the eleventh electroluminescent segment EL11 through
the line conductor 246, it is also effective as the sectional
control switch S1 to connect through the line conductor 252 for
stand-by the next row of X axis extending photoconductors PC12 to
PC22.
Furthermore, the photoconductor PC22 is connected to the
alternating current source 243 through photoconductor PC11 by the
line conductor 252 and should the photoconductor PC22 have been
previously rendered conductive by the illumination of the coarse
control strip C2, the photoconductor PC22 then serves to effect the
illumination of the electroluminescent segment EL22 through a line
conductor 254. At the same time photoconductor PC22 is also
effective as sectional control switch S2 to connect for stand-by
the next succeeding row of X axis extending photoconductors PC23 to
PC33. The photoconductor PC33, upon illumination of the coarse
control strip C3, is rendered conductive to illuminate the
electroluminescent segment EL33 and is thereupon effective as
sectional control switch S3 to connect for stand-by the next
succeeding row of X axis extending photoconductors PC34 to PC44,
and so on until photoconductor PC198, shown by FIG. 2, becomes
effective upon illumination of the coarse control strip C18 to
connect for stand-by the last row of X axis extending
photoconductors PC199 to PC209.
The driven network 221 while utilizing only 16 silicon controlled
rectifier switches may be rendered effective to drive 10 Y axis
extending fine control electroluminescent strips and 19 X axis
extending coarse control electroluminescent strips, for energizing
209 electroluminescent display segments, as explained in the
aforenoted U.S. Pat. No. 3,440,637.
As shown schematically in FIG. 3, the electroluminescent display
segments 226 are divided into a column of a number of small
segments of a phosphor material. The number needed being determined
by the accuracy, resolution, and sensitivity requirements of the
display instrument.
Dimming Control
Referring now to the dimming control 228, a dimming potentiometer
control 255 shown in FIG. 4 provides for manual control of the
brightness of the energized electroluminescent display segments 226
so that the display may be distinguishable under any condition of
ambient illumination.
The dimming circuit 228, shown in FIG. 4, comprises a back biasing
diode bridge rectifier 256 connected in the common conductor 231
leading from the display segments 226, shown in FIG. 3, and
interposed between the electroluminescent display segments 226 and
the conductor 248 leading to ground 245. A dimming potentiometer
control 255 is provided for the area source lamp to balance the
display for darkness operation. The brightness of the
electroluminescent segments will be adequate for visibility in
normal lighting (approximately 50 foot-candles). The arrangement is
such that the diode bridge rectifier 256 serves to limit the
passage of alternating current from the source 243 and through the
display segments 226 to a voltage greater than a back biasing
direct current voltage 257 set by adjustment of the potentiometer
255. In this manner, there is provided a precise control of the
electroluminescent display brightness regardless of the number of
electroluminescent segments activated.
Referring particularly to the back biasing diode bridge rectifier
256, it will be seen that a first diode 258 comprises an anode 259
connected to a junction 273 and thereby to the ground 245 by
conductor 248 and a cathode 260 connected to a junction 261 to
which leads the conductor 274 from the control potentiometer 255. A
second diode 262 comprises an anode 263 connected to a junction 264
to which leads the line conductor 231 from the electroluminescent
display segments 226 and a cathode 265 connected to the junction
261.
In addition, the bridge rectifier 256 comprises a third diode 266
having an anode 267 connected to a junction 268 from which leads
the conductor 275 to the control potentiometer 255 and a cathode
269 connected to the junction 264 to which leads the line conductor
231 from the electroluminescent display segments 226. A fourth
diode 270 has an anode 271 connected to the junction 268 and a
cathode 272 connected to the junction 273 and thereby through the
common line conductor 248 to the ground 245.
In this manner, the back biasing diode bridge 256 is connected to
the ground 245 in series with the electroluminescent display
segments 226 by its two junctions 264 and 273. The bridge rectifier
256 is also connected to the back biasing direct current voltage
257 at its junctions 261 and 268 through line conductors 274 and
275, respectively. The line conductor 275 is connected to a
negative terminal 276 of a direct current supply voltage 280 and to
one terminal 281 of a resistor 282 at junction 283. The other line
conductor 274 is connected through a movable contact arm 284 to the
resistor 282 which resistor is connected at an opposite terminal
286 to a positive terminal 288 of the supply voltage 280. The
lighting intensity may be adjusted, as desired, by suitable
adjustment of the dimming potentiometer control 255 to set the back
biasing DC voltage so as to limit the effective voltage of the
energizing alternating current applied through the bridge rectifier
256 to the electroluminescent display segments 226.
The electroluminescent display segments EL1 to EL209 are
essentially capacitors and if a direct current voltage is applied
across an electroluminescent segment no light would be produced. At
the same time, if a portion of the alternate current voltage which
is applied across the electroluminescent segment is blocked, it
will vary its brightness. Therefore, since the electroluminescent
segments 226 are in series with the bridge rectifier 256, an
operator may adjust the control potentiometer 255 to vary the back
biasing direct current, whereupon the alternating current supplied
across the electroluminescent segments 226 will be varied to reduce
or increase the brightness of the electroluminescent display
lamps.
The alternating current activating circuit for the selectively
illuminated electroluminescent display segments 226 may be readily
traced from the source of aLternating current 243. Thus upon a
positive half wave of alternating current being applied from the
source 243 through the conductor 244 leading to the ground 245, the
positive half wave of alternating current will be applied through
the grounded conductor 248 to the junction 273 of the diode bridge
256 and thereby to the anode 259 of the diode 258 and from the
cathode 260 of the diode 258 to the junction 261.
However, only that portion of the positive half wave of the
alternating current will pass through the diode 258 to the junction
261 which effectively overcomes the biasing force applied by the
direct current source 280 to the cathode 260 of the diode 258. The
resultant portion of the positive half wave of the alternating
current applied at the junction 261 will then be applied through
the conductor 274 and the effective part of the resistor 282
leading to the conductor 281 and through the conductor 275 to the
junction 268 of the diode bridge 256. Moreover, from the junction
268, the resultant portion of the alternating current is applied to
the anode 267 of the diode 266 and from the cathode 269 of the
diode 266 to the junction 264 where the resultant portion of the
alternating current is applied through the common conductor 231 to
one conductive layer of each of the selectively illuminated
electroluminescent segments 226, while the opposite conductive
layer of each of the selectively illuminated segments 226 is
connected through a control section, as shown by FIG. 4, to the
opposite then negative terminal of the source of alternating
current 243.
Similarly, upon the reoccurring opposite positive half wave being
applied at the previously negative terminal of the source of
alternating current 243, this opposite positive half wave will then
be applied through the aforementioned control section to one of the
conductive layers of each of the selectively illuminated segments
226, while a positive reverse flow of current will be effected from
the opposite conductive layers of each of the selectively
illuminated segments 226 through the common conductor 231 to the
junction 264 of the diode bridge 256 and thereby to the anode 263
of the diode 262 and from the cathode 265 of the diode 262 to the
junction 261.
However, only that portion of the positive half wave of the
alternating current will pass through the diode 262 to the junction
261 which has effectively overcome the back biasing force applied
by the direct current source 280 to the cathode 265 of the diode
262. The resultant portion of the positive half wave of the
alternating current applied at the junction 261 will then be
applied through the conductor 274 and the effective part of the
resistor 282 leading to the conductor 281 and through the conductor
275 to the junction 268 of the diode bridge 256. Moreover, from the
junction 268 the resultant portion of the alternating current is
applied to the anode 271 of the diode 270 and from the cathode 272
of the diode 270 to the junction 273 where the resultant portion of
the alternating current is applied through the conductor 248 to the
ground 245 returning thereby through the conductor 244 to the
opposite then negative terminal of the source of alternating
current 243.
It will be seen then that the resultant portion of the alternating
current applied across the opposite conductive layers of the
selectively illuminated electroluminescent display segments 226 is
effectively controlled by the back biasing direct current voltage
applied by the direct current source 280 as set by the adjustment
of the operator-operative potentiometer control 255. Thus the
intensity of illumination of the selectively illuminated
electroluminescent segments 226 may be effectively increased by
decreasing the biasing voltage applied by the direct current
biasing source 280 while the intensity of illumination may be
effectively decreased by increasing the biasing voltage applied by
the direct current biasing source 280.
The dimming control 228, as described and claimed herein with
reference to FIG. 4, provides the subject matter of the present
invention, whereby the intensity of the illumination of the
luminous column of the electroluminescent display may be readily
adjusted independently of the number of electroluminescent segments
226 that may be selectively illuminated so that the viewer may be
able to better distinguish the indicator display column under
varying conditions of ambient illumination.
Control System for Display Segments
As herein described with reference to FIG. 1, a direct current
analog signal voltage effected by the condition sensor 210 is
compared in a comparator 216 with a feedback voltage applied
through a summation network 222 by the driven network 221 and any
difference or error voltage is fed to the electronic drive
circuitry 218 to control the operation of a driven network 221 as
more fully described in the U.S. Pat. No. 3,440,637.
Within the electronic circuitry the differential error voltage
resulting from the comparison of the direct current analog signal
voltage and the feedback voltage is used to control the length of
the lighted electroluminescent display column 226. That is, a
lighted condition is caused to progress along the display column of
the electroluminescent display segments 226 by the resulting
operation of the driven network 221 which causes electroluminescent
driving capacitor strips F1 to F10 and C1 to C19 to shine upon the
photoconductor switches PC1 to PC209 to excite, in turn, a
predetermined number of the 209 electroluminescent display segments
EL1 to EL209 corresponding to an indicated value of the condition
sensed by the sensor 210.
Thus, by means of the direct current analog and feedback signals
from the electronic circuit, the length of this lighted
electroluminescent column of the display segment 226 is
continuously compared to the value of the direct current input
parameter of the sensor 210. When the lighted column of the display
segments 226 has progressed to the predetermined length indicative
of the sensed condition, the switching circuit is operated to stop
further movement or illumination of the column of the display
segment 226.
As hereinbefore described with reference to FIGS. 2 and 3, the
various electroluminescent capacitor control strips F1 to F10 and
C1 to C19 of the electroluminescent photoconductor drive circuits,
internal to the display indicator, are not made in the same
geometrical format as the column of the display segments 226. The
display segments 226 may be made, for example, of 44
electroluminescent display segments to the inch, but the
electroluminescent capacitor control strips are provided with a
series of 10 parallel, spaced electroluminescent fine control
strips F1 to F10 extending in Y-axis direction, and the other with
a series of 19 parallel spaced electroluminescent coarse control
strips C1 to C19 extending perpendicular thereto in an X-axis
direction. The electroluminescent strips are then connected to the
electronic control circuitry, partly shown in schematic form in
FIGS. 3 and 4, and more fully shown in the U.S. Pat. No.
3,440,637.
The various electroluminescent and photoconductor elements may be
arranged on four or more thin cards, as shown in the U.S. Pat. No.
3,440,637. These cards may be stacked and interconnected in the
same manner as if they were a single format. In addition, in
simplifying the production of these electroluminescent
photoconductor elements, this method may be used for
troubleshooting and thus allow for change of scale factor in the
summation of signals from each card. Reliability theory assigns a
great importance to the proper assembly of individual
electroluminescent and photoconductor cells.
The electronic drive circuitry and driven network 221 and summation
network 222 performs the guiding control for the various coarse and
fine electroluminescent strips, the photoconductors and eventually
the electroluminescent display segments 226 as best shown and
described in the aforenoted U.S. Pat. No. 3,440,637.
The dimming circuit shown in FIG. 4 utilizes the capacitor
characteristics of the electroluminescent display segments 226 so
that a direct current applied across the opposite plates of the
display segments 226 effects no illumination. At the same time, if
a portion of the alternating current voltage of the illuminating
current is blocked, the brightness of the electroluminescent
display segments 226 will be varied thereby. In the bridge circuit
of FIG. 4, there is a direct current supplied in series with the
alternating current voltage and with the electroluminescent display
segments 226 so that as the direct current is increased in the
bridge rectifier 256, the alternating current across the
electroluminescent display segments 226 will be reduced.
In summary therefore, the solid state display circuitry described
herein provides for reduction in activating the circuitry by means
of a four dimensional control, the use of an electronic servo for
greater accuracy, and the use of means to simultaneously switch off
all the photoconductors for a faster response within the system. In
addition, this system provides for a unique combination of
electronic and optoelectronic techniques in a matrix control with a
multifunction operation of the coarse and fine control circuitries
and a dual function of a transfer circuit. Further, this system
provides for a high accuracy produced by a simple summation
circuit, a unique circuit arrangement for excitation control and
level changes and a unique electronic isolation between control and
display sections achieved by means of the electroluminescent and
photoconductor components and in addition the present invention
provides a unique circuit for dimming the electroluminescent
display segments.
While one embodiment of the invention has been illustrated and
described, various changes in the form and relative arrangement of
the parts, which will now appear to those skilled in the art may be
made without departing from the scope of the invention. Reference
is, therefore, to be had to the appended claims for a definition of
the limits of the invention.
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