U.S. patent number 3,928,960 [Application Number 05/455,666] was granted by the patent office on 1975-12-30 for combination wristwatch and calculator.
This patent grant is currently assigned to Time Computer, Inc.. Invention is credited to Robert O. Reese.
United States Patent |
3,928,960 |
Reese |
December 30, 1975 |
Combination wristwatch and calculator
Abstract
Disclosed is a combination wristwatch and calculator utilizing a
common electro-optical digital display. A time and calendar circuit
is combined with a calculator circuit, both formed by large scale
integration, and used to actuate common display stations of a light
emitting diode digital display. Time is constantly kept but the
calculator circuit is only energized upon operation of a "calculate
mode" switch to conserve battery energy. Also disclosed is a solar
cell for recharging the battery and an inhibit timer for
automatically extinguishing the display when the device is in the
calculate mode but not in use.
Inventors: |
Reese; Robert O. (Lancaster,
PA) |
Assignee: |
Time Computer, Inc. (Lancaster,
PA)
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Family
ID: |
26987064 |
Appl.
No.: |
05/455,666 |
Filed: |
March 28, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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329973 |
Feb 6, 1973 |
3803834 |
|
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Current U.S.
Class: |
708/111; D18/2;
368/87; 368/159; 368/239; 968/937; 713/321 |
Current CPC
Class: |
G06F
15/0208 (20130101); G04G 9/007 (20130101) |
Current International
Class: |
G04G
9/00 (20060101); G06F 15/02 (20060101); G04B
037/12 (); G04B 019/30 (); G04C 021/32 () |
Field of
Search: |
;6F/738
;58/4A,5R,152R,153 ;235/92T,152,156 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Jackmon; Edith Simmons
Attorney, Agent or Firm: LeBlanc & Shur
Parent Case Text
This application is a continuation-in-part of copending application
Ser. No. 329,973, Filed Feb. 6, 1973, now U.S. Pat. No. 3,803,834.
Claims
What is claimed and desired to be secured by United States Letters
Patent is:
1. A combination wristwatch and wrist calculator comprising an
electro-optical digital display, a time circuit having a plurality
of time information outputs, a demand switch coupled to said time
circuit for energizing said time information outputs only on
demand, a calculator circuit having a plurality of calculator
information outputs, a miniature keyboard coupled to said
calculator circuit, common means coupling both said time and
calculator information outputs to said display, and a second demand
switch coupled to said calculator circuit for energizing said
calculator information output, said common coupling means
comprising a plurality of driver transistors.
2. A combination wristwatch and wrist calculator comprising an
electro-optical digital display, a time circuit having a plurality
of time information outputs, a demand switch coupled to said time
circuit for energizing said time information outputs only on
demand, a calculator circuit having a plurality of calculator
information outputs, a miniature keyboard coupled to said
calculator circuit, common means coupling both said time and
calculator information outputs to said display, a second demand
switch coupled to said calculator circuit for energizing said
calculator information output, a battery, and means coupling said
battery to said time circuit, said battery being coupled to said
calculator circuit through said second demand switch.
3. A combination wristwatch and wrist calculator comprising an
electro-optical digital display, a time circuit having a plurality
of time information outputs, a demand switch coupled to said time
circuit for energizing said time information outputs only on
demand, a calculator circuit having a plurality of calculator
information outputs, a miniature keyboard coupled to said
calculator circuit, common means coupling both said time and
calculator information outputs to said display, a second demand
switch coupled to said calculator circuit for energizing said
calculator information output, and an inhibit timer coupled to said
calculator circuit for inhibiting said calculator information
output after a predetermined period of time.
4. A device according to claim 1 wherein said driver transistors
are bipolar.
5. A device according to claim 1 wherein said driver transistors
form a transistor array.
6. A device according to claim 2 wherein said battery is
rechargeable.
7. A device according to claim 6 including a solar cell coupled to
said battery for recharging it.
8. A device according to claim 3 including means coupling said
inhibit timer to said keyboard whereby said inhibit timer is reset
whenever a key on said keyboard is depressed.
9. A combination wristwatch and wrist calculator comprising a
plurality of electro-optical digital display stations, a time
circuit having a plurality of time information outputs, a first
demand switch for coupling said time information outputs to said
display stations, a calculator circuit having a plurality of
calculator information outputs, a miniature keyboard having a
plurality of keys electrically coupled to said calculator circuit,
a second demand switch for coupling said calculator information
outputs to said display stations, and common driver transistors
coupled between said display stations and both said time
information outputs and said calculator information outputs.
10. A device according to claim 9 wherein said driver transistors
comprise a transistor array.
11. A device according to claim 9 wherein said driver transistors
are bipolar.
12. A device according to claim 9 wherein said driver transistors
comprise both segment drivers and digit drivers.
13. A device according to claim 9 including rectifier diodes
coupling said time information outputs and said calculator
information outputs to said common driver transistors whereby said
time and calculator information outputs are electrically isolated
from each other.
14. A device according to claim 9 wherein said display comprises
four time stations, and a plurality of additional stations, at
least some of said time stations and all of said additional
stations being coupled to said calculator information outputs.
15. A device according to claim 14 wherein said time stations
include a pair of colon dots, the lowermost of said colon dots also
being coupled to said calculator information outputs to serve as a
decimal point.
16. A device according to claim 14 wherein three of said time
stations are coupled to said calculator information outputs.
17. A device according to claim 9 including a power supply, said
second demand switch coupling said power supply to said calculator
circuit whereby said calculator circuit is energized only when said
second demand switch is operated.
18. A device according to claim 17 including means continuously
coupling said time circuit to said power supply whereby time is
continuously kept by said time circuit.
19. A device according to claim 9 including an automatic display
turnoff circuit coupling said keyboard to said calculator circuit
whereby the display is automatically turned off if a calculator key
is not actuated within a predetermined time.
20. A device according to claim 19 wherein said automatic turnoff
circuit comprises a capacitor, the actuation of a key acting to
discharge said capacitor.
Description
This invention relates to a combination wristwatch and calculator
and more particularly to a combination solid state wrist calculator
and crystal controlled precision timepiece. It incorporates a
miniature keyboard and an electro-optical digital display,
preferably in the form of a plurality of light emitting diodes. The
time display and the calculate operations are mutually exclusive
and are selected by a mode switch.
In recent years, there have been developed a variety of new
wristwatches generally referred to as "electronic" watches. In many
instances, these device use as a timing source a crystal controlled
electronic oscillator whose frequency is divided down to produce
timing signals at a frequency of 1 Hz and less by a low power solid
state divider often incorporating complementary MOS transistors. In
some instances, the wristwatches have incorporated an
electro-optical digital display in the form of liquid crystals or
light emitting diodes. A wristwatch of this general type
incorporating light emitting diodes is disclosed in assignee's U.S.
Pat. 3,672,155 whereas a similar wristwatch construction utilizing
a liquid crystal digital display is disclosed in assignee's U.S.
Pat. 3,701,249. Through the use of large scale integrated circuits,
it is possible to form most of the active components of the
wristwatch from a single large scale integrated circuit chip, or at
the most only a few chips.
Recent years have also seen the development of a new family of
electronic calculators generally referred to as pocket calculators.
These calculators have taken a wide range of forms, depending upon
size and complexity, but in many cases have incorporated integrated
circuitry in combination with a digital numerical display. While in
some instances the pocket calculators have been sufficiently small
to be readily held in the palm of one hand, they have in all
instances been quite large and bulky in relation to a modern sized
man's wristwatch. One of the limiting factors in further reduction
in size of a pocket calculator has been the necessity for a readily
accessible keyboard which can be easily and accurately operated
without placing undue requirements on the manual dexterity of the
operator to perform the desired mathematical calculation.
In order to overcome these and other problems, there is disclosed
in my copending application Ser. No. 329,973, filed Feb. 6, 1973,
now U.S. Pat. No. 3,803,834, a novel wristwatch device which
combines the features of both a precision timepiece and a very
small or minature electronic calculator. This is made possible by
combining in a novel manner certain features of the newer type
wristwatches with certain features of the so-called pocket
calculators and by providing an improved and unique miniature
keyboard on the watch face.
In the device of that application, time, which as used herein
includes calendar information such as the day and month of the
year, is constantly kept. This time information is displayed when
desired on the face of the watch in the form of a digital numerical
display. The display took the form of an eight-digit
electro-optical display using two digits to display minutes, two
digits for hours, two digits for the day of the month and the last
two digits for the month of the year. By manually depressing a mode
switch on the wristwatch, the calculator portion of the device is
actuated and the eight digit display made responsive to the digital
calculator circuitry. By depressing appropriate keys on the face of
the wristwatch, the desired mathematical calculations are performed
by the calculator circuits within the watch and the result
displayed on the same digit display previously used to indicate
time. Time is constantly being kept in the wristwatch even when
operating in the calculate mode, so that accurate time may be
displayed at any instant. In addition, when the device is used to
display time, i.e., not in the calculate mode, the calculator
circuits are de-energized so as to minimize the power drain on the
small sized energy source or battery provided in the wristwatch
case.
The present invention is directed to an improved device of the same
general construction but one which is particularly adapted for use
with a light emitting diode display. In the present device, the
display takes the form of seven display stations four of which are
used to display the same time (and calendar) information as in the
previous construction. Three of these stations along with the
remaining three stations of the display are connected to a
calculator circuit to form a six-digit numerical calculator
display.
The combination calculator and timepiece is constructed to take
optimum advantage of present day, large-scale integrated circuit
techniques and in the preferred embodiment, most of the active
circuit elements are formed from only two large-scale integrated
circuit chips, namely a combination clock and calendar chip and a
calculator chip. Novel circuitry is disclosed which, in conjunction
with a manually operated mode switch, selects the calculator or
time circuit as desired to energize the light emitting diode
display. During display, the diodes are scanned or strobed at a
relatively high rate so as to conserve energy by reducing the
maximum energy drain from the small battery power supply while at
the same time giving the impression of continuous illumination. A
further feature of the device of this invention is an improved
keyboard construction and the incorporation of an inhibit timer
circuit for extinguishing the display when the device is in the
calculate mode, but not in use.
It is therefore one object of the present invention to provide an
improved combination wristwatch and calculator.
Another object of the present invention is to provide an improved
wristwatch and digital calculator.
Another object of the present invention is to provide an improved
digital wristwatch and calculator utilizing a light-emitting diode
display.
Another object of the present invention is to provide an improved
wrist calculator having a novel miniaturized calculator
keyboard.
Another object of the present invention is to provide a combination
wristwatch and calculator in which both share a common
light-emitting diode digital display.
Another object of the present invention is to provide a combination
wristwatch and calculator including a calendar time display.
Another object of the present invention is to provide a combination
wristwatch and electronic calculator incorporating a common light
emitting diode display which minimizes power drain on the watch
batteries.
Another object of the present invention is to provide a combination
wristwatch and electronic calculator particularly adapted for
construction using primarily large-scale integrated circuit
chips.
Another object of the present invention is to provide a combination
wristwatch and calculator which can be made using only one or at
the most only two large-scale integrated circuit chips.
These and further objects and advantages of the present invention
will be more apparent upon reference to the following
specification, claims and appended drawings, wherein:
FIG. 1 is a perspective view of a combination wristwatch and
electronic calculator constructed in accordance with this
invention;
FIGS. 2A through 2E, when assembled in the manner illustrated in
FIG. 2, show a detailed circuit diagram of the device of this
invention; and
FIG. 3 is an enlarged view of the keyboard of the device of FIG.
1.
Referring to the drawings, the novel combination wristwatch and
electronic calculator of the present invention is generally
indicated at 10 in FIG. 1 as comprising a watch case 12 to which is
attached a wristwatch band or bracelet 14. Visible through a window
16 in the watch face 18 is a numerical digital time and calculator
display 20. Also mounted on the face 18 of the watch is a
calculator keyboard 22. The display includes a four digit or four
station time portion which is shown with the numerals 12:28,
indicating that the time is 28 minutes after 12 o'clock. These same
four display stations are used to indicate the day of the month and
month of the year, as well as the AM or PM of time as more fully
described below. The three rightmost of the time stations are
common to a calculator display which includes three more stations
(not illuminated in FIG. 1) to form a six-digit or six-station
calculator display.
Keyboard 22 is of the same type as disclosed in my copending
application Ser. No. 329,974 filed Feb. 6, 1973, now U.S. Pat. No.
3,803,834, the disclosure of which is incorporated by reference.
Briefly, it comprises a plurality of keys 24 which, when depressed,
complete an electrical circuit to a calculator inside watch case
12. The keys are formed of an electrically conductive plastic of
the snap-acting type, having sufficient resiliency to snap back
into position when the pressure is removed. By way of example only,
the conductive plastic for the keys may be formed of a composite of
micron-sized copper particles dispersed in a cross-linked polymer
classified as a conductive polymer. Volume resistivity and
thermo-elasticity are a function of the metal loading by weight.
When a key is depressed by the end of a standard ball point pen or
similar device, the central portion of the key engages the head of
an electrically conductive pin beneath the key. Depression of the
key into engagement with the head of the pin establishes an
electrical connection to the calculator circuit. When the key is
released, the inherent resiliency of the plastic material from
which it is formed causes it to snap back, thus breaking the
circuit to the calculator.
By way of example only, the keys may comprise a composite
consisting of a copper base filler in a silicone rubber binder.
Conductive polymers of this type are generally as flexible as
rubber and nearly as conductive as copper. Usually, the copper
particles must be segregated to an optimum size and particle shape
and subsequently plated to prevent surface oxidation. Metal filled
elastomers are typically orders of magnitude more conductive than
conventional carbon elastomers and give greater electrical
stability. They typically contain about 80% by weight of metal and
are capable of 300 percent elongation and tensile strengths of 200
psi.
FIGS. 2A through 2E, when arranged as illustrated in FIG. 2, show a
detailed circuit diagram of the combination wristwatch and
calculator 10 of FIG. 1. Principal components of the device are
formed by a CMOS clock and calendar chip 26 and a second MOS
calculator chip 28. If desired, both the chips 26 and 28 may be
formed using complementary-symmetry MOS transistors and in fact,
they may both be formed as a single chip. However, at the present
time, more desirable calculator features are available in P-MOS so
that in the preferred construction, chips 26 and 28 are separate
chips and the LIS chip 26 is a CMOS chip while the calculator chip
28 is made using P-MOS.
In the preferred embodiment, the clock and calendar chip 26 is the
same circuit as that set forth in assignee's copending application
Ser. No. 328,639, filed Feb. 1, 1973, now U.S. Pat. No. 3,803,827,
the disclosure of which is incorporated herein by reference.
In order to understand the remainder of the circuitry of the device
of the present invention, a brief description of the timekeeping
portion of the circuit and the operation of chip 26 is believed
necessary. The time keeper comprises a crystal oscillator formed by
a CMOS inverter in chip 26 in combination with a quartz crystal 30,
which acts as a frequency standard for the time keeper operating at
a frequency of, for example, 32,768 Hz. Other components of the
oscillator external to chip 26 have been omitted for the sake of
clarity. This relatively high frequency from the oscillator is
supplied to a frequency converter in chip 26 formed of a CMOS
binary divider, so that the output from the converter is at a
frequency of 1 Hz. This signal is supplied to a display actuator
also in chip 26 to produce segment drive signals at output pins
labeled a through g, and digit drive signals at pins labeled
S.sub.1 through S.sub.4 for actuating the time portion of the
display 20. When in the time keeping mode, the diodes are normally
not illuminated but time is constantly being kept. When it is
desired that time be displayed, the wearer depresses the time
demand button 32 in FIG. 1, closing time switch 34 labeled S1. With
the operation of this switch, the hours and minutes are first
displayed for a predetermined time and if the pushbutton 32 remains
depressed, the hours and minutes are extinguished and the seconds
become visible. The same display diodes are used for both minutes
and seconds since these are not displayed simultaneously, thus
minimizing the power drain from the watch battery.
When calendar information is to be displayed, the demand button 36
in FIG. 1 is depressed. This closes switch 38 labeled S2 so that
the same diodes which previously displayed hours and minutes now
display, in numerical form, the day of the month and month of the
year, as long as the date button 36 remains depressed. When hours
and minutes are displayed, these are separated by a pair of colon
dots (:), each formed by a light-emitting diode. During the
calendar display, the upper colon dot is illuminated to indicate AM
of time and the lower colon dot is illuminated to indicate PM of
time. Minutes are reset by momentarily closing switch 40 labeled S3
on the back of the watch and hours are independently reset by
closing switch 42 also from the back of the watch, all as more
fully described below.
Display 20 is also of the type more fully shown and described in
assignee's copending application Ser. No. 328,639, filed Feb. 1,
1973, now U.S. Pat. No. 3,803,827, and comprises a plurality of
light-emitting diodes mounted on a ceramic substrate (not shown) to
form a single unitary display package. In the device of the present
invention, the display comprises seven digits or stations 44, 46,
48, 50, 52, 54 and 56. The first station 44 is formed by a pair of
light-emitting diode segments 58 and 60 whereas each of the other
stations are formed as seven-segment LED arrays. Individual diodes
62 and 64 form colon dots between the hours and minutes display and
the lower colon dot 64 also acts as a decimal point for the
calculator display. Individual LEDs 66, 68, 70 and 72 also are used
for decimal points in the calculator mode. During date display,
illumination of the upper colon dot 62 indicates AM of time and
illumination of the lower colon dot LED 64 indicates PM of
time.
The first four LED stations or digits, namely digits 44, 46, 48 and
50, are used to display time and calendar information. At station
44, both segments 58 and 60 are simultaneously ON or OFF to display
either a one or nothing at all. The seven-bar segment arrays at the
other six stations display the numbers zero through 9. These other
six stations all form part of the calculator display. Separate
connections are made to the anodes of the diode segments at each
station as illustrated. The diode cathodes at each station are
connected in common, as indicated by the rectangular dashed box 74
at station 44, and the larger rectangular dashed boxes 76 at each
of the other stations. The only exception to this is the individual
cathode connections for the colon dots 62 and 64 as indicated by
the small dashed boxes 78 and 80.
Timing information from CMOS chip 26 appears only on demand at the
seven pins labeled a through g and passes by way of leads 82
through inverters 84 and rectifier diode 86, to the seven segment
drivers 88, 90, 92, 94, 96, 98, and 100. The eighth driver 102 is a
decimal point driver connected to the calculator chip. These are
NPN junction transistors in which the timing information is
supplied through the diodes 86 to the transistor bases. The
collectors of each of the segment driver transistors are connected
in common to the power supply or battery voltage V.sub.ss as
indicated at 104, and the emitters are all connected to the display
20 through current limiting resistors 106. The inverters 84, diodes
86, and transistors 88 etc. are preferably each formed as arrays,
that is, formed on a common substrate so as to have more nearly
matching characteristics.
In the preferred embodiment, the stations are strobed or scanned to
reduce excessive current drain on the watch battery. This is done
for the time and calendar displays by turning the first four
stations 44, 46, 48, and 50 on in sequence, so that no two stations
are energized from the battery at the same time. However, this is
done at a sufficiently high rate so as to create the appearance of
constant illumination of all four stations. These strobing or
scanning signals are derived from CMOS chip 26 and appear at the
pins labeled S.sub.1, S.sub.2, S.sub.3, and S.sub.4. They pass by
way of leads 108 and the three rectifier diodes 110 to four of a
set of eight digit drivers 112, 114, 116, 118, 120, 122, 124 and
126. These digit drivers are NPN junction transistors and they have
their emitters connected in common to the power supply or battery
voltage V.sub.dd. The connections are to the bases of these
transistors through current limiting resistors 128 and the
transistor collectors are connected to the cathodes of the
respective display stations forming the display 20. The digit
driver transistors, as with the segment drivers previously
described, are preferably formed as an array, that is, on a single
common substrate, so as to better match their characteristics. The
four digit drivers 114, 116, 118 and 120, connected to CMOS chip
26, control the sequence of display of the first four display
stations 44, 46, 48 and 50. The last three digit drivers 122, 124
and 126 control the display of the last three stations 52, 54, and
56. The digit driver 112 is connected through the first of a pair
of rectifier diodes 130 and 132 to the cathode 80 of the lower
colon dot LED 64. The driver 114 for the first station is connected
to the cathode 78 of the upper colon dot LED 62 by way of cathode
74 of station 44 and lead 79. A second pair of rectifier diodes 134
and 136 cooperate with the diodes 130 and 132 to control the
operation of the colon dot diodes 62 and 64. In the time display
mode the upper colon dot is energized at the same time as station
44 by way of lead 79 from the cathode 74 of the station to the
colon dot cathode 78. The lower colon dot is also energized at this
time from driver 114 by way of lead 81, rectifier diode 130, and
lead 83 to cathode 80. However, colon dot 64 is also used in the
calculator mode (as a decimal point) and in this mode cathode 80 is
energized from driver 112 by way of recitifier diode 132. Rectifier
diode 136 connects the anode of dot 64 to the decimal point lead 85
and rectifier diode 134 supplies the colon and PM logic signals
from segment driver 92 to the anode of dot 64 in the time display
mode. The colon dots are energized along with station 44 since that
station consists of only two segments 58 and 60.
As previously indicated, the calculator chip 28 is preferably a
P-MOS chip and by way of example only, in the preferred embodiment,
is a Cal-Tex P-MOS chip identified as CT-5007. It supplies signals
to the seven segment driver transistors 88, 90, 92, 94, 96, 98 and
100, and to the decimal driver 102, by way of a plurality of
rectifier diodes 138. Again, these diodes are preferably formed as
an array and are eight in number, one for each of the display
stations and a last one supplying a signal to the decimal point
driver transistor 102. The digit or station drivers are connected
to the calculator chip by way of a decimal point on lead 140 to the
driver 112 and by way of six leads 142, for the six station drivers
116, 118, 120, 122, 124 and 126. No signal is supplied to station
driver 114 from the calculator chip since the first station 44 is
not used in the calculator mode and only six digits can be
energized. Three of these six connections are through recitifier
diodes 144.
The keyboard 22 is shown diagrammatically in FIG. 2A to illustrate
its electrical connection in the circuit. It comprises ten lower
keys numbered 0 through 9. The upper row also contains ten keys and
these are labeled beginning at the upper left, +M, Add To Memory,
-M, Subtract From Memory, RM, Read Memory, Division,
Multiplication, Subtraction, a common Equals and Add Key, a Clear
Entry Key, a Clear Key for clearing both entry and memory, and a
decimal point key for inserting the decimal point. The two
vertically aligned keys from each row are connected in series with
the ten respective output leads 146, 148, 150, 152, 154, 156, 158,
160, 162 and 164. Each row is connected to the calculator chip 28
by the respective leads 166 and 168 labeled K.sub.1, K.sub.2,
respectively. For example, when the decimal point key 170 is
depressed, the K.sub.1 signal on lead 166 is connected to lead 164.
Similarly, when the 0 key 172 is depressed, the K.sub.2 signal on
lead 168 is connected to lead 164. Similar connections of either
the K.sub.1 signal or the K.sub.2 signal are made to the respective
output leads when either a corresponding upper or lower key is
depressed. The decimal point is inserted by depressing key 170 and
the appropriate number for energizing from the K.sub.2 line the
cathode of the station at which it is to appear.
An important feature of the present invention resides in the fact
that the K.sub.1 and K.sub.2 pins of the calculator chip are also
connected by way of leads 174 and 176 and resistors 178 and 180 to
an inhibit timer circuit generally indicated at 182.
The purpose of the inhibit timer 182 is to extinguish the LED
display when in the calculate mode, if one of the keys on the
keyboard is not depressed within a predetermined length of time.
This acts to conserve battery energy by avoiding the possibility of
inadvertently leaving the display on in the calculate mode when no
calculations are actually being performed. Inhibit timer 182
applies a signal on inhibit lead 184 to the inhibit input 186 of
the calculator chip 28. Lead 184 is connected to the junction of a
resistor 188 and a capacitor 190 in turn connected through a
rectifier diode 192 to an NPN junction transistor 194 having bias
resistors 196 and 198. During normal operation, the capacitor 190
is charged with the polarity indicated and junction transistor 194
is turned off or in the non-conducting state. At this time, the
display is inhibited by the inhibit voltage on lead 186 of the
calculator chip.
When one of the keys of the keybaord 22 is depressed, current flow
from one of the K.sub.1 or K.sub.2 pins of the calculator chip
through one of the resistors 178 or 180 turns on transistor 194,
causing its emitter-collector circuit to conduct. This results in a
discharge of capacitor 190 causing the inhibit voltage to approach
V.sub.dd, which permits the display to come on. Subsequent keyboard
entries keep capacitor 190 at least partially discharged so that
the calculator display remains on. However, if a key is not
depressed within a predetermined length of time, determined
primarily by the RC time constant capacitor 190 (C.sub.1) and
resistor 188 (R.sub.1), then the capacitor recharges, the inhibit
voltage on lead 184 approaches ground potential, and the calculator
display is automatically extinguished.
The combination calculator and wristwatch 10 of FIG. 1 is provided
with a third demand or pushbutton 200. This pushbutton operates a
mode switch 202 which, as illustrated, is a double pole, double
throw switch. It comprises a pair of ganged movable contacts 204
and 206, with the first movable between the stationary contacts 208
and 210, and the second movable between the stationary contacts 212
and 214. The switch is shown in the "time" position where movable
contact 204 engages stationary contact 210 and movable contact 206
engages stationary contact 214. When pushbutton 20 is momentarily
depressed, the switch moves to the "calculate" position with
movable contact 204 engaging stationary contact 208 and movable
contact 206 engaging stationary contact 212. Successive depressions
of pushbutton 20 cause the mode switch to move back and forth
between the mode and time positions. As with the time and date
buttons 32 and 36, mode button 200 preferably carries a permanent
magnet which actuates a magnetic field responsive reed switch
within the watch case. Stationary switch contact 208 is connected
to the calculator by way of a lead 216 and stationary contact 212
is connected to the calculator chip by way of a lead 218. Movable
contact 204 is connected to ground or the positive side of a
battery (V.sub.ss) whereas movable contact 206 is connted to the
negative side of the rechargeable battery 220. The battery is a
conventional rechargeable dry cell type energy source, preferably
formed by three dry cells connected in series to produce an output
voltage of approximately 4 1/2 volts. It is preferably connected in
series with a solar cell 222, mounted on the face of the watch to
receive ambient light, such as through the window 16 of FIG. 1. By
placing the device near a suitable light source, such as a
conventional 100-watt lightbulb, where the light from the lightbulb
impinges upon solar cell 222, it is possible to completely recharge
battery 220 in a matter of only a few hours and this may be done,
for example, overnight, when the device is not being worn.
The keyboard 22 is diagrammatically illustrated in FIG. 2 as a
two-line keyboard in order to illustrate the electrical connections
to the calculator chip by way of the K.sub.1 and K.sub.2 leads 166
and 168. The actual physical layout of the keyboard is shown in
FIG. 3 where, in the preferred embodiment, the keyboard comprises
20 keys arranged in four rows of five columns. Various keyboard
arrangements may be provided as desired but the one illustrated in
FIG. 3 is preferred in that it provides ready access to the keys
most used and is fully consistent with accepted calculator keyboard
layouts. As previously indicated, the individual keys may be
depressed to actuate the circuits by the tip of a ballpoint pen, a
small stylus, or any small relatively narrow tipped instrument
which may be readily grasped in the fingers and applied to the
keyboard.
While the mode switch 202 has been described as a pushbutton
actuated magnetic reed switch, it may, if desired, be a
conventional electrical circuit switch actuated by the keyboard.
For example, successive depression of two keys in an unusual
sequence (such as the divide key followed by the multiply key) can
be used to set an RS flip-flop to place the device in the
"calculator" mode. In order to return the device to the "time"
mode, the flip-flop is reset by depression of the time read demand
button 32 and the accompanying momentary closure of switch 34.
It is apparent from the above, that the present invention provides
an improved combination wristwatch and watch calculator. The device
is particularly adapted for use with a light-emitting diode display
and because of this incorporates an inhibit timer circuit for
automatically turning off the display when not in use. Also
provided is a rechargeable battery which is connected to a solar
cell so that the battery may be recharged from a conventional light
source, such as a conventional 100-watt incandescent lightbulb.
Novel circuitry is disclosed for strobing or scanning the display
to minimize maximum current drain from the battery and a novel
diode arrangement for isolating the time and calculator portions of
the circuit so that the device may be converted from time to
calculator display by the operation of a single manual switch. Time
setting is effected by bringing a permanent magnet near one of two
indentations in the back of the watch case so as to actuate either
a minute set reed switch or hour reed switch inside the case.
Actuating the hour set switches advances the hours at a rate of 2
Hz and actuation of the minute set switch advances the minutes at
the same rate while automatically resetting the seconds to zero,
all as more fully shown and described in assignee's copending
application Ser. No. 328,639, filed Feb. 1, 1973, now U.S. Pat. No.
3,803,827.
In the preferred embodiment, the light-emitting diode display is a
seven-digit or seven-station display with the first digit used only
to display the tens digit of the hours of time and the tens digit
of the month of the year. Time information, including the date, is
displayed on the first four digits whereas only the last six digits
are used for the calculator display. The circuit is particularly
adapted for large-scale integration and requires for the principal
components of the device, at the most, only two chips, namely, a
time chip 26 and a calculator chip 28.
While the device of the present invention is particularly adapted
for use with a light-emitting diode display, other digital displays
such as field effect liquid crystals and the like may be used if
desired. For displays of this type, which draw less current, the
inhibit timer circuit 182 is not required and the calculator chip
may take the form of a CMOS chip. By way of example only, one type
of LSI chip usable in such a construction is a Toshiba type T3171B.
In constructions where the time and calculator chips are both all
CMOS, these may, if desired, be combined in a single CMOS chip.
The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
present embodiments, therefore, are to be considered in all
respects as illustrative and not restrictive, the scope of the
invention being indicated by the appended claims rather than by the
foregoing description, and all changes which come within the
meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
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