US 3672155 A
Disclosed is a solid state watch which requires no moving parts for timekeeping and display. The watch comprises a crystal controlled oscillator connected through an integrated circuit binary frequency divider to an electro-optical display in the form of light emitting diodes. The display is energized only on demand and the level of the light output is controlled in accordance with ambient light conditions. The watch is energized from a rechargeable battery.
Claims available in
Description (OCR text may contain errors)
United States Patent Bergey et al.
[ 51 June 27, 1972  SOLID STATE WATCH  Inventors: John M. Bergey; Richard S. Walton, both of Lancaster, Pa.
 Assignee: Hamilton Watch Company, Lancaster, Pa.
 ,Filed: May 6, 1970  Appl. No.: 35,196
 U.S. Cl. .58/50 R, 5 8/85.5  Int. Cl. ..G04b 19/30  Field of Search ..58/23, 50, 85.5
 References Cited UNITED STATES PATENTS 3,485,033 12/1969 Langley ..58/23 3,194,003 7/1965 Poiin ..58/5O 3,576,099 4/1971 Walton.'. .l ..58/50 Primary Examiner-Richard B. Wilkinson Assistant Examiner-E. C. Simmons Attorney-Le Blane & Shur ABSTRACT Disclosed is a solid state watch which requires no moving parts for timekeeping and display. The watch comprises a crystal controlled oscillator connected through an integrated circuit binary frequency divider to an elcctro-optical display in the form of light emitting diodes. The display is energized only on demand and the level of the light output is controlled in accordance with ambient light conditions. The watch is energized from a rechargeable battery.
17 Claims, 26 Drawing Figures PATENTEDmzv I972 3. 672. 1 55 sum 01 or 15 INVENTORS JOHN M. BERGY RICHARD S. WALTON ATTORNEYS PKTENTEDmzv m2 3.672. 155
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sum 12 nr15 402 MW Q jlllll lllll PATENTEDwm I972 SHEET 13H! 15 FIG. 15/] .PDmkDO hmai TENS BINARY NUMBER UNITS TENS Q Q2 Q Q Q5 PATENTEDJum m2 SHEET 1H [1F 15 V W X Y UNITS 0 O O O O O O O O O O O O O O 7+| SEGMENT DISPLAY TENS BINARY NUMBER UNITS 0 Q2 0 Q4 Q5 0 O O O- O O O O O O O 0 0 O O O O O O O PKTDITEBJIIIINIQR 3.672.155
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magi/gig? 7+| SEGMENT DISPLAY E UNITS TENS g UNITS N E8 Q o Q o Q RsTu VWXYC 0 o 0 o o o I I I I l o o l I o o o o I o I I o o o o o I o I o o o 2 I I o I l o l o l I l o o o a I I I I o o I o I 0 o I o ,o 4 o I l I o I I o l I o I o o 5 I o l I o I l o I o o o o o o I I l I I I o 0 I o o o o I o I I o o o o o I o I o o o 2 I I o I I o I o I SOLID STATE WATCH This invention relates to a solid state timepiece and more particularly to an electric watch which employs no moving.
parts. In the present invention, a frequency standard in the form ofa crystal oscillator acts through solid state electroniccircuit dividers and .drivers to power in timed sequence the light emitting diodes of an electro optic display. Low power consumption and small size and weight are achieved through the use of complementary MOS circuits to produce what is in essence a miniaturized fixed program computer.
Battery power Wristwatches and other small portable I timekeeping devices of various types are well known and are ploy an electromechanical oscillator as the master time reference. In many instances, these constructions have utilized a crystal controlled high frequency oscillator as a frequency standard in conjunctionwith high frequency conversion circuitry to produce a drive signal at a suitable timekeeping rate. However, difficulties have been encountered in arriving at an oscillator-frequency converter combination having not only the required frequency stability, but also sufficiently low power dissipation and small size to be practical for use in a battery powered wristwatch.
ln'order to overcome these and other problems, there isdisclosed in assignees copending U.S. application Ser. No. 768,076, filed Oct. 16, 1968, now U.S. Pat. No. 3,560,998 a crystal controlled oscillator type watch construction using low power complementary MOS circuits. The'oscillator-frequency converter combination of that application as described is suitable for'driving conventional watch hands over a watch dialor, alternatively, for selectively actuating the display elements of anoptical display in response'to the drive signal output of the converter.
ln assignees copending U.S. application Ser. No. 818,228, filed Apr. 22, 1969, now U.S. Pat. No. 3,576,099, there is disclosed an improved watch construction in which the optical display takes the form of a plurality of light emitting diodes which are intermittently energized on demandat the'option of the wearer of the watch. Thisassures a minimum power consumption and an increasingly long life for the watch battery.
The present invention is directed to an improved watch construction of thesame general type as disclosed in the aforementioned copending applications and one which utilizes no moving parts to perform the timekeeping function. The watch of the present invention consists of only three major components, namely, a quartz crystal time base, a miniature time computer module, and a rechargeable battery. These mic'rominiature components are packaged in a conventional size wristwatch chassis or case. A tiny quartz slab is precisely cut to predetermined dimensions so that it vibrates at 32,768 l'lz when" properly stimulated by pulses from an electronic oscillator. The high frequency from the crystal time base is divided down to 1 pulse per second by utilizing a multistage, integrated circuit binary counter. The time computer module counts the input pulse train, encodes it into binary form, and
then decodes and processes the results so as to provide the appropriate signals at display stations.
Situated on the front of the watch adjacent the display is a pushbutto'n demand switch which, when pressed, instantly activates' the appropriate visual display stations. Minutes and hours are programmed to display for 14 4 seconds with just a touch of the demand switch. Continued depression of this switch causes the minute and hour data to fade and the seconds to immediately appear. The seconds continue to count as long as the wearer interrogates the computer module. Computation of the precise time is continuous and completely independent of whether or not it is displayed.
Incorporated in the watch case is a miniature} or 4- 6 V rechargeable battery which is easily replaced by the wearer. The battery will last about fiveor six months underaverage wearing conditions before recharging becomes necessary and need for replacement is indicated by a dim display but the time accuracy of the watch is not affected by the reduced capacity power supply. Each watchis soldwith an extra rechargeable battery connected through a recharging circuit to provide the correct recharging current. The spent battery is, simply removed by the wearer and replaced, by the, fully recharged spare. No computed time is lost in this battery exchange since a third energy source pennanentlylocated inside the electronic module supplies sufficientpower to run the,
time computer module during the exchangecycle.
The watch display consists of a T.V. screen-like colored. filter which passes the cold red light from. GaAsP light emitting diodes. A 27 dot or, alternatively, a 7 segment array forms each individual number at'theappropriate moment at a brightness detemiined by a specially designed dimmer circuit.
This dimmer circuit utilizes photodetectors .to measure ambient lighting conditions so the display intensity provides viewing comfort under all day or nighttime lighting conditions.
Setting is accomplished quickly and accurately by inserting any suitable probe (pencil, pen, small stick, etc.) into one of two clearly marked recesses. The Hour Set" rapidly advances the hours without disturbing the accuracyof the minutes or seconds. The Minute Set" automatically zeros the seconds while it advances the minutes to the desired setting, The whole procedure, even though seldom required, takes a,
matter of a few seconds. I
The watchof the present invention is virtuallyshockproof, and waterproof, regardless of the environment in which it .is placed. The computer module, including the display, is encapsulated with a clear potting compound sothat no mechanical It is therefore one object of the present invention to provide.
an improved electronic wristwatch. Another object of the present invention is to provide a wristwatch which utilizes no moving parts. for performing the timing function.
Another object of the present invention is to provide av completely solid state electronic wristwatch in which the display is in the form of a plurality of light emitting diodes.
Another object of the present invention is to provide an electronic watch including an illuminateddisplay in whichthe light level is automatically compensated tothe viewing conditions for increased eye comfort and reduced power drain.
Another object of the present invention is to provide an improved electronic watch in which the display is automatically programmed such that the hours and minutes disappear at a predetermined period of time and the seconds display comes into view. I
Another object of the present invention is to provide an improved wristwatch incorporating an electro optic display with an improved arrangement for resetting the display and one which includes automatically zeroing of the seconds display.
Another object of the present invention is to provide an-im- These and further objects and advantages of the invention wiil be more apparent upon reference to the following specification, claims, and appended drawings, wherein:
FIGS. lA-IC are views of the face of a watch constructed in accordance with the present invention under differing conditions of operation;
FIG. 2 is a simplified block diagram of the major components of the solid state watch of this invention;
FIG. 3 is an exploded view showing the physical construction of the novel solid state watch of this invention;
FIGS. 4, 4A and 4B are overall block diagrams of the electrical circuit for the solid state watch of FIG. 3;
FIGS. 5, 5A, 5B and 5C are detailed wiring diagrams for the watch of FIG. 3',
FIG. 6 shows a plurality of waveforms illustrating the operation of the light dimmer forming a part of the watch of FIG. 3;
FIG. 7 shows the details of one of the decoder drivers forming a part of the electrical circuit of the watch of FIGS. 3-5;
FIG. 8 shows a modified crystal controlled oscillator circuit for the watch of the present invention utilizing complementary MOS circuits;
FIG. 9 shows a modified display element for the watch of the present invention in the fon'n of a 7 bar segment construction of light emitting diodes;
FIG. 10 is a detailed wiring diagram for a modified watch construction utilizing the display of FIG. 9 in which the programmable counter and decoder for the 7 segment display are all formed on a single monolithic integrated circuit chip;
FIG. 10A is a table showing the connections to the power supply terminals A and B in FIG. 10 when the circuit of FIG. 10 is used for different display digits;
FIG. 10B shows the alphabetical nomenclature for the 7 bar segment diodes R through W of a ones digit and the corresponding diode Y of the I0s digit in the hours display;
FIG. 11 shows waveforms at various locations in the circuit of FIG. 10.when it is used to count to 12 (11 2) for the hours display;
FIG. 12 shows similar waveforms for the circuit of FIG. 10 when it is used to count to 10 (0-9) for the ones digits of the minutes and seconds display;
FIG. 13 shows corresponding waveforms for the circuit of FIG. 10 when it is used to count to 6 (0-5) for the IOs digits of the minutes and seconds display;
FIG. 14 is a waveform and timing diagram for the BCD to decimal decoder forming a part of the circuit of FIG. 10;
FIG. 15A is a table showing the relationship between the input signals, the BCD output of the counter (counting 1-12) and the 7 diode segments (8 segments with the 10s Y) for the hours display;
FIG. 15B is a similar table showing the relationship when the counter is counting to 10 (09); and
FIG. 15C is a corresponding table for when the counter is counting to 6 (0-5 Referring to the drawings, the novel watch of the present invention is generally indicated at 10in FIG. 1A. The watch is shown in FIG. 1A to actual size and is constructed to fit into a watch case of approximately the size of a conventional man's wristwatch. The case 12 isshown connected to a wristwatch strap 14 and includes a display window 16 through which the time is displayed in digital form and a pushbutton 18 for operating a demand switch through which the display is activated.
FIG. 1A shows the watch as it normally appears when the time is not being displayed. That is, in FIG. 1A no time indication is visible through window 16 and this is the normal condition which prevails in order to conserve battery energy in the watch. However, even though the time is not displayed through the window 16, it is understood that the watch 10 continuously keeps accurate time and is capable of accurately displaying this time at any instant of the day or night. When the wearer desires to ascertain the correct time, he depresses pushbutton 18 with his finger and the correct time immediately is displayed through the window 16 which illustrates a dot display giving the correct time reading as 10:10, namely ten minutes after ten o'clock, as indicated at 20 in FIG. 1B. The hours and minutes, i.e., 10:10, are displayed through the window 16 for a predetermined length of time, preferably l-% seconds, irrespective of whether or not pushbutton 18 remains depressed. The exact time of the display is chosen to give the wearer adequate time to consult the display to determine the hour and minute of the time. Should the minutes change during the time of the display, this change is immediately indicated by advancement of the minute reading to the next number, i.e., 11, as the watch is being read. If pushbutton 18 remains depressed, at the end of l-Vi seconds, the hours and minutes of the display are extinguished, i.e., they disappear, and simultaneously the seconds reading, i.e., 59, is displayed through the window 16 as indicated at 22 in FIG. 1C. The advancing seconds cycling from 0 to 59 continue to be visible through window 16 until the pushbutton 18 is released.
FIG. 2 is a simplified block diagram of the electrical circuitry for the watch of FIG. 1. The circuit comprises a time base or frequency standard 26 including a crystal to provide a very accurate frequency such that the frequency standard or oscillator oscillates at 32,768 Hz. This relatively high frequency is supplied by lead 28 to a frequency converter 30 in the form of a divider which divides down the frequency from the standard so that the output from the converter 30 appearing on lead 32 is at a frequency of 1 Hz. This signal is applied to a display actuator 34 which, in turn, drives the displays 20 and 22 of the watch 10 by way of electrical lead 36.
FIG. 3 is an exploded view showing the physical construction of a watch formed in accordance with the present inven tion. Watch 10 in FIG. 3 comprises the casing 12 carrying the pushbutton or display button 18 and provided with a window 16 through which the display-may be read. Inserted into the window 16 and sealed there by a suitable epoxy resin is alight filter 38 which screens out much of the light which might otherwise get through the window. Of course, the filter 38 may be formed of a clear transparent material which passes all light but in the preferred embodiment it takes the form of a suitable red colored plastic, such as Plexiglas, which acts as a red filter (bandpass) passing light from the light emitting diodes of the display which, by way of example only, operate at a wave length of approximately 6,500 Angstroms in the visible red region. In some instances, it may be desirable to construct the filter 38 to pass blue as well as red wave lengths so that the blue of the sky gets absorbed in the watch, thus enhancing somewhat visibility of the lighted numbers under outdoor daytime reading conditions. The filter 38 may be formed of any suitable material, in addition to plastic, such as transparent colored glass or of ruby material having sufficient hardness that it will not scratch.
Received within case 12 are a pair of abutting back-to-back shims (shown separated for the sake of clarity), namely, a display shim 40 and a logic shim 42. The shims are preferably formed of a good strong heat conducting material, such as beryllium copper to take away any heat that might be generated by the display. Mounted on the underside of the logic shim 42, as indicated by phantom lines at 44, is the integrated logic circuitry. Secured to the top surface of display shim 40 are six display modules 46, 48, 50, 52, 54 and 56. Display modules 46 and 48 are for displaying the hours from I to 12, modules 50 and 52 are for displaying the minutes from 0 to 59, and modules 54 and 56 are for displaying the seconds from 0 to 59. Each of the modules is formed as a 27 dot array, i.e., each carries 27 light emitting diodes with the exception that minute module 50 carries the additional colon diodes 58 and hours 10s digit module 46 carries only suflicient diodes to display a l that is the tens digit of the hours display is either 1 or 0 and O is not illuminated. While a 27 dot array is illustrated, the display modules may take any desired form and may consist of a 13 dot array or a 7 segment bar array as disclosed in copending application Ser. No. 818,227, filed Apr. 22, 1969. By way of example only, the 27 dot array illustrated in FIG. 3 may be formed on modules of the type manufactured by the Hewlett-Packard Company of Palo Alto, California, identified as solid state numeric indicator HP 5082-7,000. These moduleshave the light emitting diodes mounted on them and are formed of a ceramic base with integrated circuit chips such as the chips 60, 62, 64, 66 and 68 mounted on the ceramic base and connected to the diodes and the logic circuitsby suitable leads, laminated, printed or etched directly on the ceramic substrates. Connection from the display modules to the logic circuit 44 is by way of leads 70 which extend over the adjacent edges of the display shim 40 and the logic shim 42. In the preferred embodiment, the display modules are made slightly narrower than is customary for solid state numeric indicators but they are in all other respects I similar to the commercially available solid statenumeric indicators identified above.
While twoseparate shims are'illustrated, it is understood that by using suitable monolithic integrated circuit constructions itis possible to mount the logic circuits and display circuits on the top of a single shim, thus eliminating the necessity for the second shim illustrated in FIG. 3. In the preferred embodiment, the display shim and the logic shim with the respective circuits attached are potted by coating the upper surface of shim 40, theshim edges and the lower-surface of shim 42 with a clear silicone rubber potting compound. This isolates the electronics from the surrounding environment and enhances the reliability of operation of the circuits.
Depending from the underside of logic shim 42 is a quartz crystal 72 which,when the watch is assembled, is adapted to project into the opening 74 of a quartz crystal pocket 76 attached to electronic seal cover 78. Seal cover 78 carries a second pocket 80 which permanently receives a small internal sustaining power sourceor battery for maintaining the timing operation of the watch when the main battery is removed for replacement and recharging.
Mounted on back cover 82 of the watch is a battery case 84 which houses a conventionalrechargeable 4- .6 V silver zinc battery (not shown). The battery may be of a 3 lk V cell construction to give a total battery output of 4 1% volts with a life of approximately 250 milliampere hours. Assuming standard usage, i.e., an average of approximately 24 interrogations per day, the battery will last on the order of 5 or 6 months before recharging is necessary. The batteryemploys a potassium hydroxide electrolyte and batteries of this type are commercially available from Yardney, Inc. of New York City. Power is supplied from the battery in case 84 by way of a pair of pins 86 and 88 which slide into receptacles 90 and 92 in the battery case to make contact with the battery and the upper ends of which contact with the electrical circuitry on the underside of logic shim 42. Resetting is effected by a pair of two-part reset pins extending through the back cover of the watch, the two parts of one of the reset pins being illustrated at 92A and 92B in FIG. 3. Finally, the various elements of the watch are mechanically secured together by the screws 94.
It is a feature of the watch that the substrates of the display modules are removably attached to the upper surface of display shim 40. That is, the substrates of the display modules 46, 48, 50, 52, 54, and 56 are attached by Borden's epoxy to the shim, which epoxy softens at about 300 F. and permits removal of the display modules from the. shim for repair or replacement. The light emitting diodes mounted on the substrates are interconnected with the remaining circuitry by 0.001 inch aluminum wires ultrasonically bonded for interconnection.
FIGS. 4, 4A and 4B show an overall block diagram of the electrical circuit of the watch of the present invention. Watch 10 comprises an oscillator 96 which is controlled by the crystal. 72 of FIG. 3 to produce an output on lead 98, i.e., a pulse train on that lead having a pulse repetition rate of 32,768 Hz. The crystal output passes through a complementary symmetry MOS counter 100 of the type shown and described in assignees copending application Ser. No.
7 768,076, filed Oct. l6, 1968, which acts as a divider, dividing on lead 102 having a pulse repetition rate of 256 Hz. This signal is divided by 2 in counter 104, by 2 again in counter 106, by 6 (2 in counter 108, and by 4 (2) in counter 110.
An 8 Hz. output on lead 112 from counter 108 is applied to a set-hold circuit 114 where the 8 Hz. repetition rate pulse train appears as an output on lead 116. The 8 Hz. signal on lead 116 is applied to a counter 118 where it is divided by 8 (2") to produce a 1 Hz. output pulse train on lead 120. The 1 Hz. pulse train is divided by 10 in counter 122, divided by 6 in counter 124, divided by 10 again in counter 126, divided by 6 again in counter 128, and the output of this counter is finally applied to counter 130 which divides by 12. The output of counter 122 appearing on leads 132, 134, 136, and 138 is a binary coded decimal 1248 code which is applied to the decoder-driver 140 which, in turn, energizes the tens digits of the seconds display indicated at 142. The ones digits of the 1 seconds display indicated at l44are similarly actuated from counter 124 by way of seconds decoder-driver 146. Similar decoder-drivers 148, 150, and 152 actuate the tens digits of the minutes display at 154, the ones digits of the minutes display at 156, and the hours display at 158. Counter 130 has five output leads to decoder-driver 152 for a purpose more fully described below. The other decoder-drivers 146, 148 and 150 are actuated by BCD 1248 codes from their respective counters 124, 126, and 128 in the same manner as decoder-driver 140 is actuated from counter 122.
As previously stated, in order to conserve energy, the light emitting diodes are only energized on demand, i.e., when the pushbutton 18 of FIGS. lA-lC is depressed by the wearer's finger. Even when the button is depressed, the lights are not always continuously lit but instead, in order to conserve power, are intermittently lighted during less than full daylight conditions at a frequency sufficiently high to give the appearance of continuity due to the light retention properties of the human eye. The pulses for intermittently lighting or pulsing the seconds display are derived from a display controldriver 160 which applies the on-off pulses by way of lead 162 to the seconds decoder-drivers and 146. Similar intermit tent pulses from the display control drivers are applied by lead 164 to the minutes decoder'drivers 148 and 150 and by lead 166 to the hours decoder-driver 152. The exact frequency at which the displays are turned on and off while always sufficiently high to give the impression to the human eye of con tinuous light is determined by a light control circuit 168 which supplies a light control signal by lead 170 to display control drivers 160. The light control signal is. either DC (full daylight) or a combination of a 64 Hz. signal supplied from counter 106 by way of lead 172, a 128 Hz. signal supplied by counter 104 by way of lead 174, and a 256 Hz. signal supplied from the output of counter 100 by way of lead 176. These signals are combined in the light control circuit 168 in a manner determined by the output signal on lead 178 to the light control circuit from ambient light sensors 180. These light sensors are in the form of three phototransistors mounted on the display shim at 180 in FIG. 3 and act to produce increased illumination from the light emitting diodes during strong daylight conditions and less illumination from the diodes under nighttime or reduced light conditions. In the preferred embodiment, light sensors 180 provide four different light levels from the light emitting diodes so that the watch face may be read with equal facility and comfort under all possible lighting conditions while at the same time conserving energy at times when less light is needed from the diodes to make them visible, such as is the case when the watch is read in at least partial darkness.
As previously stated, the watch face is ordinarily not illuminated. The hours and minutes diodes only light up when the demand switch is depressed. Actuation of the demand button by the wearer causes the read switch 184 in FIG. 4b to close, causing the positive side of the power supply to be connected by way of leads 186 and 188 to the display control drivers 160. Energization of these drivers permits passage through them of the signal from the light control circuit 168 which is passed on to the decoder-drivers causing the minutes and hours displays to be illuminated. No output from the display control diodes 160 appears on lead 162 at this time and the seconds displays are not illuminated. Closure of read switch 184 also applies B+ by way of lead 190 to set-hold circuit 114 which immediately resets a display timer 192 by way of lead 194. Display timer 192 is a divide by counter and has applied to its input the 8 Hz. pulse train on lead 112. This timer divides the 8 Hz. by 10 and after 1 seconds produces an output pulse on lead 196 which is applied to display control driver 160. This pulse causes the display control driver to change state, removing the output from leads 164 and 166 and causing the minutes and hours displays to be extinguished. At the same time, the output is switched to lead 162 causing the seconds display to be illuminated simultaneous with the extinguishment of the hours and minutes display.
An important feature of the watch of the present invention lies in the fact that the hours may be set independently of the minutes and seconds and at a very rapid rate. Closure of hours set switch 198, which is actuated from the back cover of the watch by a double pin setting arrangement of the type illustrated at 92A and 92B in FIG. 3 grounds one input of an hours set circuit 200 by way of leads 202 and 204. Hours set circuit 200 receives a 2 Hz. pulse train from counter 110 by way of lead 206 and actuation of the hours set circuit by closure of hours set switch 198 causes the hours set circuit 200 to pass the 2 Hz. signal on lead 206 to counter 130 by way of lead 208. Hours set switch 198 is also connected to the display control drivers 160 to cause an output to appear on leads 164 and 166 assuring that the hou'rsand minutes are displayed when the hours are being reset during closure of switch 198. A minute set switch 212 is connected by leads 214 and 216 to a minute set circuit 218. As before, actuation of this circuit causes it to pass a 2 Hz. pulse train on lead 220 from counter l 10 by way of lead 222 to the divide by 10 counter 126 drivirig the minute display. Minute set switch 212 is likewise connected by lead 224 to display control drivers 160, again to insure an output on leads 164 and 166 during resetting.
It is a feature of the watch of the present invention that actuation of the minute set switch 212 automatically zeros the seconds display. The reason for this is that most time signals, such as those given over the radio and the like, are given on the hour or on the minute and in order to start the watch in synchronism with the correct time as given by such a signal, it is necessary that the seconds display be at zero at the time the radio tone or-other time signal is heard. In order to accomplish this, the minute set switch 212 is connected by leads 214 and 216' and a further lead 226 to set-hold circuit 114. Energization of this circuit from lead 226 produces an output pulse on output lead 228 which is applied to the reset terminals of counters 1 18, 122, and 124 by way of leads 230, 232, and 234 resetting these counters to zero and causing the seconds display to be automatically zeroed.
FIGS. 5,5A,5B and 5C show a detailed circuit diagram of the watch of the present invention shown in block form in FIG. 4. In FIG. 5, like parts bear like reference numerals. In FIG. 5, the elements corresponding to the blocks in FIG. 4 are enclosed in dashed boxes and the various decoder-drivers 140, 146, 148, 150, and 152 are shown as including a plurality of logic NOR gates for a purpose more fully described below. .The display control drivers 160 are shown in two separate dashed boxes at different points in the circuit of FIG. 5 as is the light control circuit 168. Oscillator 96, including quartz crystal 72, takes the form of a complementary bipolar transistor construction including transistors T1 and T2 which are connected to form a free running crystal controlled multivibrator producing a substantial squarewave or pulse output. Alternatively, oscillator 96 may take the form of a complementary MOS transistor of the type shown and described in assignee's copending application Ser. No. 768,076, filed Oct. 16, 1968, or it may take the fonn of the oscillator shown and described in assignees copending application Ser. No. 802,571, filed Feb. 26, 1969. In the preferred embodiment,
oscillator 96 is connected to the positive side of the battery through a current limiting resistor 229 and capacitor 227. The light sensors, which are preferably mounted on the top surface of the logic shim 40 of FIG. 3 so as to be exposed to ambient light passing through the filter 38 of that FIG., take the form of three photosensitive transistors 331, 333, and 335, labeled LS1, LS2, and LS3, respectively. These are conventional transistors in which the conductance of the emitter-collector circuit of the transistor is modified in accordance with the amount of light radiation impinging on the transistor base.
Following is a detailed description of the operation of the circuit of FIG. 5.
The transistors T1 and T2 with the crystal and associated parts oscillate at a frequency of 32,768 Hz. This frequency is divided by 2" by counter 282. The output frequency of this counter is 256 Hz. This frequency is fed into counter 283 which has outputs of 128 Hz., 64 Hz., 8 Hz. and 2 Hz. The frequencies 256 Hz., 128 Hz., and 64 Hz. are used in the light control or light dimmer circuit 168 which will be explained later. The 2 Hz. is used in the setting circuits also to be explained later. The 8 Hz. signal is used to drive'the seconds counter and as the time base for the output control.
For timekeeping, the 8 Hz. signals feed into the 7 stage counter 310. The first three stages of this counter act to divide by 8 and correspond to counter 118 of FIG. 4. Output Q4 gives a pulse every second, Q5 gives a pulse every two seconds, Q6 every four seconds, and Q7 every eight seconds. This is known as a binary coded decimal (BCD).output. The decoder-driver requires a negative BCD input which is achieved by passing the signal through the NOR gates 301, 302, 303, and 304. The decoder-driver converts the BCD input into the proper form to light a numeral with light emitting diodes in a 27 dot matrix. The counter 310 is supposed to count to 10 but would nonnally count to 16. By detecting the numbers two and eight from outputs Q5 and Q7 and feeding them into a NAND gate 308 and inverter 309, it is possible to get a reset signal which passes through NOR gates 315 and 316 to the reset input. The reset signal from inverter 309 is also fed into the counter 313. This counter has outputs of one, two and four. This BCD number is converted to a negative BCD number by NOR gates 305, 306 and 307 and fed into the decoder-driver. The numbers two and four are detected by NAND gate 311 and inverter 312 and turned into a reset signalwhich passes through NOR gates 318 and 317 to the reset of counter 313 so that it counts six. This input pulse is lengthened by the 10 pf capacitor 236 at the input of NOR gate 314 and passed through this gate to be the input signal of counter 326. The outputs of this counter are the BCD 1,2, 4, 8. This output is converted to a negative BCD number by NOR gates 319, 320, 321 and 322and fed into the decoderdriver. The numbers two and eight are detected by the NAND gate 328 and the inverter 329 converts it to a reset signal to make counter 326 count 10. This reset signal is also used as an input signal for counter 327. Counter 327 is gated to divide by 6. The BCD output is converted to negative BCD by NOR gates 323, 324 and 325 for use by the decoder-driver. The numbers two and four are detected by the NAND gate 330 and converted to a reset signal by inverter 331. This signal passes through NOR gate 332 to flip-flop 339. The Q output of this flip-flop provides the one output of the BCD output. The two, four, and eight outputs are detected by NAND gate 342 and converted to a reset signal by inverter 343. This reset signal passes through NOR gates 346 and 347 to reset counter 340 only. It is not necessary to reset flip-flop 339 because at the count of 10 its output is zero. The reset signal is also fed into flip-flop 341. This sends a signal to NOR gate 338 which puts a signal into the negative BCD input of the decoderdriver which lights the one of the hours. This one remains for the numbers 10, ll and l2; however, when the number thirteen is detected by signals from flip-flop 339, counter 340 and flip-flop 341, being fed into NAND gate 344, a reset signal is generated by NOR gate 345 which actuates pulse generator T9. This signal resets counter 340 to zero and flip-flop 341.