Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention.
The present invention relates to lamp flashers and more
particularly to apparatus for flashing lamps in particular code
sequences and for synchronizing a number of lamp flashing
systems.
2. Background of the Invention.
Marine buoys and beacons commonly use incandescent lamps
which are periodically flashed in various sequences of short and
long flashes separated by short and long eclipses for identifica-
tion of channels, obstructions and other navigational features.
Many such devices are battery operated and conservation of
primary power is important. In recent years, older flashing
systems using motors and relays have been supplanted by transis-
tor timing and control circuits. For example, see the following
U.S. patents to Seidler: 3,24~,892; 3,310,708; and 3,596,113.
To obtain reliability and accurately timed signals, voltages must
be regulated. To eliminate relays, transistor switches have been
used. Prior art regulating and switching transistors have
generally been germanium types to minimize voltage drops; how-
ever, these types have high leakage, especially at high tempera-
tures. Lower leakage at high temperatures can be obtained with
the use of silicon transistors but at the expense of higher
voltage drops.
In many applications, a number of beacons or buoys are
required to operate in synchronism, and generally, a master
flasher controls a set of slave units. When the master fails~
improper operation of the slaves is common. A need exists for a
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flexible easily programmable flasher control circuit that will
minimize primary power drain, that will permit any unit to
synchronize the remaining units, ~hat will not fail when other
units fail, and which will permit almost any coded signals to be
generated.
SUMMARY OF TH~ INV~NTION
The invention is a new and improved lamp control system
that overcomes problems common to prior art systems. The voltage
regulator and switching circuits utilize silicon transistors
having low leakage in a novel connection that produces low
voltage drops. The current to the lamp is monitored during
flashes and a lamp change switch is closed when a lamp failure is
detected energizing an automatic lamp changer.
A solid-state flash sequence generation circuit is pro-
vided using, for the most part, integrated logic circuits.
Almost any code sequence or sequence of short and long flashes
and eclipses can be generated. The sequence generator utilizes
an electronic counter which produces a count for each sequential
flash and eclipse pair. A set of electronically switched RC time
constants are controlled from the counter to produce the desired
flash and eclipse durations of each successive set of a flash and
eclipse. The selected time constants for a given flash-eclipse
period controls a timing generator which clocks the counter at
the beginning of each such flash-eclipse period.
When a number of flashers are to be operated together,
the invention permits synchronizaticn of the flashes and
eclipses. Sync pulses are produced at the beginning of each
flash and are fed to a cable or othe{ link to the other flasher
units in the system. If all units are not in synchronization,
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the sync pulses will cause all of the other units to reset
and synchronize. Advan-tageously, any unit can serve as the
master and the remainder as slaves. Therefore, failure of
a master will not affect the other units.
A daylight control is also provided to disable
the flashes during the day, thereby conserving primary power.
When darkness falls, the daylight control will cause at least
one flasher to begin operation. The sync pulses from the
first enabled unit will automatically cause the remainder to
operate, regardless of whether their daylight controls have
been triggered. In the morning, all units will remain operating
until the least sensitive daylight control is operated at which
time all units will cease flashing. Therefore, if a very
sensitive daylight control on a flasher attempted to prematurely
disable that unit, the sync pulses from the other units would
maintain operation thereof, providing a fail-safe system.
Specifically, the invention is used with a dc power
source having a ground terminal, the source driving a load
having a varying resistance. The invention relates to a
load voltage regulating circuit comprising: a first transistor
connected between the power source and the load; a second
transistor connected to the first switching transistor in
a darlington connection; amplifier means including a selected
fixed reference voltage source, the amplifier means connected
to the driver transistor for regulating the voltage across
the load to an operating value controlled by the selected
reference voltage source by the darlington connected second
and first transistors when the current through the load is
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greater than a predetermined value; and switching means for
switching the second transistor from the darlington mode
for driving the irst transistor when the current through
the load is reduced to less than the predetermined value
such that the first transistor regulates the voltage across
the load to the operating value.
It is therefore a principal object of the invention
to provide a flasher unit for use in a system of synchronized
fla~her units which can be programmed to produce a desired
sequence of short and long flashes separated by short and
long eclipses and which produces synchronization pulses for
synchronizing other externally-connected flasher units there-
with.
It is another object of the invention to provide
a flasher unit having a daylight control for use in a system
of multiple units interconnected by communication links,
all units having a daylight control circuit and arranged
such that all units will continue flashing until the least
sensitive daylight control unit inhibits its flasher unit;
and in which the first flasher unit to be enabled wi.th a
drop in ambient light will cause all other units to begin
flashing.
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It is yet another object of the invention to provide a
flasher unit having a silicon transistor switch and regulator
having a low voltage drop across the regulator when the supply
voltage falls below the regulated value.
It is a further object of the invention to provide a
switch and voltage regulator using silicon transistors connected
to produce a darlington circuit for a first current level and to
change to a single regulator circuit at a second current level.
It is another object of the invention to provide a switch
and regulator using a darlington circuit modified to permit
driving the switching transistor to a preselected low voltage
drop.
It is still a further object of the invention to provide
a lamp current sensing circuit to determine when a lamp has
failed and to thereafter energize an automatic lamp changing
mechanism.
It is another object of the invention to provide a novel
lamp flash seq~ence generating circuit using integrated logic
circuits which minimize power drain on the power source and which
have long life and low cost.
It is still another object of the invention to provide a
sequence generating circuit permitting selection of a very large
variety of short and long flash sequences without the use of
mechanical devices, relays, or motors.
It is yet another object of the invention to provide a
sequence generating circuit utilizing a steppable counter con-
trolled by timing pulses in which a first timing pulse steps the
counter to the next count, in which the time to the next timing
pulse is controlled in accordance with the length of the required
flash and eclipse for that count, and in which the next timing
pulse is generated causing the counter to step to the next count.
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These and other objects and advantages of my flasher
system will be apparent from the following detailed description
and the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a waveform diagram of a simple code sequence
for the flasher unit illustrated in Figure 2;
Figure 2 is a simplified functional block diagram of a
flasher unit of the invention;
Figure 3 is a simplified functional diagram of a system
of flasher units interconnected by communication links;
Figure 4 is a schematic diagram o~f the voltage regulator
and switch portions of a flasher unit;
Figure 5 is a schematic diagram of the logic circuits for
producing a sequence of flashes of a flasher unit; and
Figure 6 is a waveform diagram of two cycles of the
sequence of flashes produced by the unit shown in Figures 4 and
5.
DETAILED DE~CRIPTION OF THE PP~EFERRED EMBODIMENT
Referring first to Figure 2 which provides a greatly
simplified functional block diagram of the lamp control and
synchronizing system of the invention and to Figure 1 which
illustrates certain waveforms occuring during the operation of
the system, the basic mode of operation will be explained. Lamp
24, shown in Figure 2, may be an incandescent lamp installed in a
buoy or on obstructions in a waterway such as an oil drilling
platform or the like. It is required to flash lamp 24 in a
particular sequence to produce a code for identifying to vessels
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the significance of the particular buoy or structure. In Figure
1, a specific light flashing cycle is shown for exemplary pur-
poses only and it is to be understood that a large number of
different coded signals may be produced by my invention. Line B
shows a sequence of flashes FL in which a code is generated con-
sisting of three code elements; in this case, two short flashes
and a long flash, indicative of the Morse code letter U~ The
first short flash 10 may be, for example, on the order of three
tenths of a second. The lamp is then OFF for a short period as
indicated at 12. The OFF period, EC, is termed an "eclipse".
This eclipse is followed again by a short flash and a short
eclipse. The long flash shown at 16 is much longer than the short
flash and is indicated as being about three times the short flash
length in this example, or about one second. A long eclipse 18
follows the completion of the Morse letter U at which time the
coded letter is again re~eated. It is to be understood that the
flash and eclipse ratios may be varied as desired. An example of
one timing is as follows: short flash, ON for 0.3 seconds, OFF
for 0.7 seconds; and long flash, ON for 1 second, OFF for 3
seconds.
~ eferring to Figure 2, lamp 24 is flashed or turned ON by
means of lamp control circuits 22 which close a circuit to one
side of lamp 24. Power is supplied from power supply 32 which may
commonly be primary or secondary batteries or other types of
power supplies. To maintain a long lamp life, the flash output
voltage is controlled by regulator 28 which effectively controls
the maximum voltage that can be applied to lamp 24. The current
which flows through lamp 24 is monitored by lamp current sensor
26. As will be explained in more detail below, a series resistor
in the circuit of lamp 24 is not required for current monitoring
in accordance with my invention. An indication from lamp control
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22 appearing on lead 27 indicates to lamp sensor 26 that lamp 24
is in the ON condition. If, at that time, the lamp current noted
is not within the normal limits for lamp 24, a control signal is
sent to an automatic lamp changer 30 described in U.S. Patent No.
3,308,338, which replaces lamp 24 with a new unit. Regulator 28
also includes means for regulating the operating voltage to the
electronic flash control circuits of my invention.
Next, the manner in which my invention produces the
required control of lamp 24 will be described. A counter 40 is
utilized to define the time period for each set of flashes and
eclipses such as 10 and 12, and 16 and 18 of Figure 1. As may be
noted, the time period 10 and 12 is much shorter than time period
16 and 18, therefore, counter 40 is controlled to provide
different length count periods through its cycle. In the present
example, only three count periods are required for producing
flashes representative of the Morse code U as shown on line B of
Figure 1. Therefore, in one cycle, counter 40 will step from
ZERO count to the ONE count, to the TWO count, and will then
automatically reset by virtue of connection of the count T~REE
output to the reset termination of counter 40. There~ore, the
counter cycles, as shown on lines C, D and E, produce a short
pulse 14 at the ZERO output, a shor~ pulse 15 at the ONE output
and a long pulse 20 at the TWO output.
The control to produce the long and short periods is
provided by a set of switches 44, 48, 52 and 58 with associated
reslstors ~0, 62, 64 and 66. At a particular count, the desired
resistors are switched so as to charge capacitor 6& ~Cl) wherein
the time constants control the lengths of the f lash and eclipse
during that output pulse of counter 40. In the present example,
resistor 60 (Rl) is selected to produce a time constant propor-
tional to the length of the counter output pulses 14 and 15 as
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will be explained in more detail hereinafter. Switch 44 is con-
trolled by gating circuits 42 to produce a short flash 10 with
the necessary gate control signals provided by lamp control
circuit 22. Similarly, switch 48 which controls resistor 62 (R2)
is controlled by short eclipse gates 46, which are also controll-
ed from lamp control circuits 22. Thus, the value of resistor R2
determines the OFF period 12 of the lamp and, in this applica-
tion, Rl and R2 may have equal values if equal flash and eclipse
durations are required. In some instances the flash and eclipse
periods are unequal; for example, a ratio of 3 to 7 is commonly
used. In a similar fashion switch 52 and 58 control resistors 64
(R3) and 66 (R4) in which the time constants of the selected
resistors in conjunction with capacitor 68 (Cl) produces either
long flash duration 16 or long eclipse duration 18. To provide
the long flash and long eclipse, a set of gates 50 and 54 is used,
each having four inputs-for this purpose. Therefore, in one
cycle, it is possible to have four long flashes and four long
eclipses However, my invention is not limited to ~his number and
it is obvious that additional gating inputs could be provided for
this purpose. The selection of the point in a cycle of flashes at
which a long flash and a long eclipse is required is selected by
connecting an input of gate 50 and of gate 54 to the counter
output occuring at the desired point in the cycle. In the
present example, the long flash 16 and long eclipse 18 is desired
at the third count which is count TWO on line E and therefore
inputs from gates 50 and 54 are connected to the count TWO output
of counter 40. Since this is the only count in the cycle requir-
ing the long flash and eclipse, the remainder of the gate inputs
are grounded.
The control which causes the long and short outputs from
counter 40 is provided by use of clock and timing generator 34.
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As will be described in more detail hereinafter, clock and timing
generator 34 produces a sequence of timing pulses on lead 35 to
lamp control circuits 22 as shown on line A of Figure 1. The time
between these pulses is controlled by the selection of resistors
Rl through R4. The timing pulses may be short pulses in the range
of one ~illisecond to ten milliseconds at the start of each
required flash or eclipse and in the center of each flash or
eclipse. These timing pulses are directed by lamp control cir-
cuits 22 via lead 23 to the clock input of counter 40 causing it
to step one count shortly after the beginning of each flash. If
the time between the first pulse 11 referred to as a START pulse
and the third pulse 13, referred to as a STOP pulse, is short,
flash lamp control circuits 22 enable gate 42 on the START pulse
and gate 46 on the STOP pulse, both of which occur during count
ZERO from counter 40. Thus, resistors 60 and 62 are switched in
sequen~ially. As may be understood, when the START pulse 11
enables gate 42, the short time constant of RlCl will cause clock
and timing generator 34 to produce the STOP pulse 13 of the pair
which causes lamp control circuit 22 to enable short eclipse gate
46. Similarly, when the START pulse 17 of the long flash period
occurs as counter 40 steps to produce output pulse 20 on its TWO
output, pulse 20 enables one input of gates 50 and 54. A flash
pulse will then appear on lead 41 from lamp control circuits 22
to long flash gates 50 which then operate switch 52 to connect
resistor R3 to capacitor Cl producing a long time constant for
long flash 16. When the STOP timing pulse 19 appears on lead 35
to flash lamp control circuits 22, an eclipse pulse on lead 43
enables long eclipse gates 54, switching resistor R4 on resulting
in eclipse period 18.
The invention also includes a daylight control subsystem
comprising daylight control circuit 70 and photocell 72. The
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purpose of this control is to disable the flashing system during
daylight hours and to turn on the system at night. As will be
explained in more detail below, during daylight or when suffi-
cient incident light falls on photocell 72, clock and timing
generator 34 is prevented from producing timing pulses. It is
desirable that, when the system is turned on, all units in the
system will begin at the beginning of the cycle shown on line B in
Figure 1. To this end, lamp control cir~ui~s 22 produce a short
synchronizing pulse at the start of each flash and during the
first flash of each cycle. In the present example, a sync pulse
would occur at the same time as pulse 11 and as the second timing
pulse on line A. The sync pulses will appear on lead 29 from
lamp control circuits 22 to sync output amplifier 36. The sync
pulses are then externally available on output line 37 for
purposes described below. The sync pulses also reset clock and
timing generator 34 and ~ia control circuits 22, counter 40 to
ensure that the first sequence of flashes begins at the start of
a cycle.
Turning now to Figure 3, an array of N flasher systems is
shown, each being of the type illustrated in Figure 2. As is to
be understood, when each of the photocells 72 is exposed to
sufficient light, the flasher systems will all be inhibited as
previously described. The objective of my invention is to cause
all of the systems in the array to come on at the same time and to
be synchronized. It is generally not feasible to have the
sensitivity of all the photocells identical and, even if this
were true, the light incident on each cell would not normally be
of the same intensity since each of the systems would be at a
different location. For purposes of illustration assume all of
the systems are off and that system 2 experiences a sufficient
reduction in light on its photocell 72 to start the operation of
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the flasher as described above. When this occurs, the sync
signals appearing on lead ~9 from lamp control 22 of Figure 2
will be sent out on lead 37 via sync output 36. In this instance,
the sync pulses will be transmitted via links 39 to system 1,
system 3 and the remainder of the systems in the array. Thus, as
each of the other systems receive the sync pulses, it resets its
clock and timing generator 34 and counter 40, causing each of the
systems to override its daylight control 70 which is inhibited by
a control signal on lead 71 from flash lamp control circuits 22.
It is to be now noted that each system is producing its own sync
signals with all sync signals occurriny simultaneously and
appearing on each output lead 37. When the light conditions
change such as to energize photocells 72, it is also an object of
my invention to require that all units remain flashing until the
least sensitive or last unit to be turned off by daylight control
70 occurs. Assume now that the system 3, photocell 72 is the last
unit to receive sufficient light to disable the flashing system.
At this time, all of the other units will have been controlled by
their photocell to cause daylight control 70 to attempt to stop
the unit from flashing. However, the synchroni%ing pulse from
system 3 appearing at the sync input on lead 37 at each of the
other systems will again perform the function of keeping each of
the units operating. However, when system 3 eventually turns off
due to sufficient illumination of its photocell 72, its sync
pulse disappears from lead 37 and all systems will therefore turn
off at the same time. Although Figure 3 shows a conductive line
39 between leads 37 of each unit it is to be understood that any
type of interconnection can be used as determined by the environ-
ment of the systems. For example, a cable connection may be used
on large structures such as oil drilling platforms and a radio
link may be used for buoys. I do not consider the interconnec~
tion means to be a part of my invention.
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Having now described the basic operation of my inventiont
the specific novel circuits will now be explained in more detail.
Figure 4 presents a schematic diagram of the power supply regu-
lators and lamp circuit sensor portions of my invention. This
circuit consists of three basic elements: a voltage regulator
for the electronic circuits 30, a voltage regulator 90 to control
the voltage applied to incandescent lamp 24, and a lamp current
sensor 26 which operates a switch composed of transistors 205,
202, and 109.
It is contemplated that my invention will be utilized
primarily with flashers operated from a battery-type power
supply. The battery supply will vary in output voltage over a
battery life or a charging cycle. To maximize the life of an
incandescent bulb 24, it is necessary to regulate the voltage
across the bulb. With battery operation it is also necessary to
minimize the losses in the regulator circuits to maintain proper
operation as the battery voltage drops to a value lower than
normal. This has been accomplished in the past by using ger-
manium power transistors for switching and regulating the current
through the incandescent lamp. Although the drop across the main
switching transistor could be held to about 0.5 to 0.6 volts with
germanium transistors, these devices have a high leakage current
which increases at higher temperatures. In my regulator 90,
however, I have used a silicon power transistor 92 as the main
switching and regulating element. Advantageously, for low
battery voltage, I am able to maintain the voltage drop across
transistor 92 much lower than previously possible with a silicon
transistor switch and regulator. Transistor 92 is driven by
transistor 94 which in turn is driven by transistor 96. When
main transistor 92 is cut off, the collectors of transistors 94
and 96 are connected to the collector of transistor 92 by diode
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1207~6
93 to form a darlington circuit. The collectors of transistors
94 and 96 are connected via bypass resistor 95 to the negative
side of the power source which is considered ground in the cir-
cuit of Figure 4. A differential amplifier 98 and 99 is connect-
ed in a regulator circuit with voltage reference zener 97 and is
used to regulate the collector voltage of transistor 92. When
lamp 24 is first turned on, drive current will pass through the
emitter-base junction of transistor 92, through transistors 94
and 96, through diode 93 and also through the load. However, as
the collector voltage of transistor 92 rises, diode 93 will
become reverse biased and the drive current will therefore pass
through bypass resistor 35 to ground. Thus, the circuit
automatically switches from a darlington circuit to a single
transistor circuit driven by another transistor where the drive
current is now not part of the load current. With transistor 92
conducting, incandescent lamp filament 24 will draw a heavy
current when first energized and will increase in resistance as
the filament heats up reducing the drive and load current
required. The resulting collector voltage and consequently the
voltage across lamp 24 will be determined by zener 97 and the
setting of resistor 201 in the regulator circuit ~ormed by
transistors 98, 99. When the currents through transistors 94 and
96 flow through bypass resistor 95, the minimum voltage drop
between the emitter and collector of transistor 92 is not limited
by the collector-to emitter voltages of transistors 94 and 96.
When the input voltage drops below the desired regulated output
voltage in the usual darlington regulator circuit, the minimum
voltage drop across transistor 92 would approach a value
determined by the voltage drops across transistors 94 and 9~ when
the input voltage drops below the desired regulated output
voltage.
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When the supply voltage is greater than the desired regu-
lated output voltage, the voltage divider formed by resistors 205
and 103 will produce a voltage across zener 97 greater than its
zener voltage causing it to conduct. Thus, the base of differ
ential amplifier transistor 98 will be held constant at the re-
ference voltage provided by zener 97. The voltage at the base of
transistor 99 will be determined by the voltage divider formed by
resistors 197 and 201 from the regulated lamp voltage. The ratio
of resistors 197, 201 is adjusted to provide only that current
through transistors 94 and 96 which will provide the desired max-
imum output voltage at the collector of transistor 92.
When the supply voltage to the emitter of switch transis-
tor 92 approaches or drops below the desired value of the regula-
ted output voltage , the voltage at the base of transistor 98
will drop below the breakdown voltage of zener 97 to a value de-
termined by the ratio of voltage divider 205, 103. The base vol-
tage of transistor 99 is determined by the ratio of voltage
divider 19~, 201. The ratio of resistors 205, 103 is adjusted so
as to produce a low predetermined emitter to collector voltage
drop across switch transistor 92. This voltage, however, is
higher than the drop would be if transistors 98~ 96 and 94 were
fully on. The addition of resistor 103 to form divider 205, 103
when zener 97 is non-conducting therefore permits limitation of
transistor 92 drive current to that current required to maintain
the desired minimum voltage drop across transistor 92 at any
given load current.
In an alternative arrangement of the circuit of Figure 4
in which it is only required that transistor 92 switch the load
off and on without regulation of the load voltage, zener diode 97
may be omitted and the voltage across switch transistor 92 main-
tained at a very low value over a wide range of supply voltages.
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In this case, resistor 103 prevents saturation of transistors 98,
96 and 94. Without resistor 103, the drive current for
transistor 92 would be limited only by the value of resistors 95
and 211. In such case, selecting resistor 95 to supply
sufficient drive current for a high amperage load would result in
excessively high drive current ~or a low amperage load,
representing a waste of energy. With resistor 103, the drive
current is dynamically adjusted to onl~ the amount required to
maintain the selected voltage drop across transistor 92 for any
instantaneous or steady-state value of load current and the drive
current can be maintained as a small percentage of the load
current for maximum efficiency.
As may now be recognized, the novel voltage dividers
associated with differential amplifier 98, 99 and drivers 94, 96
permit the voltage drop across switch transistor 92 to approach
saturation but without excessive drive current at any given lamp
load current.
As an example of a specific operation of my novel regula-
tor 90, assume that the input voltage may vary between 13 and 18
volts and that an output of 12 volts is desired. With the input
voltage in the range of 13 to 18 volts and resistor 103 omitted,
the first step is to adjust resistor 201 to give an output vol-
tage of 12 volts. Next, the input voltage is reduced below 12
volts to, for example, 11 volts. Resistor 103 is then inserted
and adjusted to give the desired voltage drop from the emitter to
the collector of transistor 92 at the highest lamp load for which
the unit is designed.
As may be recognized, the voltage drop across bypass re-
sistor 95 will decrease if the lamp filament fails and this
voltage can thus be used for sensing such failures. A sensing
resistor in series with lamp 24 is therefore not necessary and
the power loss such a resistor would cause is eliminated.
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12~7~a6
Accordingly, the voltage across bypass resistor 95 produced by
the drive current is sensed by comparator 195. If lamp 24 fails,
comparator 195 controls transistor switch 202 which in turn
causes switching transistors 204 and lO9 to conduct to energize
an automatic lamp changer which operates to remove failed lamp 24
and to insert a new lamp.
Regulator 80, which supplies regulated power to the
timing circuits of my invention and also to comparator 195, is a
simple voltage regulator utilizing transistor 206, zener 208 and
resistor 108.
The preferred embodiment of the electronic flash control
circuits and timing circuits for my invention is shown in sche-
matic form in Figure 5, although it will be understood that other
circuits to provide the desired functions will be obvious to
those of skill in the art. The operation of the circuits illus~
trated will be explained with reference also to the diagrams in
Figure 6 of waveforms at various points in the circuits. As pre~
viously discussed in reference to Figure 2, my invention can pro-
vide up to 10 flash periods with the counter shown to permit a
variety of coded signals to be flashed, and, by selection of the
values of capacitor 68 and resistors 60, 62, 64, and 66, the
durations of the flashes and eclipses can be controlled. It is
to be understood that larger counters may be used to provide
greater than 10 flash periods. For the circuits of Figure 5, six
periods (N=6) have been selected for illustrative purposes with
counter 40 connected to produce the coded flash sequence indicat-
ed on line T of Figure 6. The sequence of two dashes, two dots
and two dashes is also, of course, an arbitrary code for illus-
tration. A short eclipse space is provided between successive
code elements with a long eclipse at the end of the code. As will
be recognized, Figure 6 shows two complete cycles of the code.
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It may be noted in Figure 5, that counter 40 has it counter out-
puts ZERO and ONE connected to two inputs of quad NOR gate 146 to
produce the two long flashes at the beginning of the code and
counter outputs FOUR and FIVE are connected to the other two in-
puts to produce the two long flashes at the end of the code. Quad
NOR gate 148 has one input connected to count output FIVE to pro-
vide the long eclipse at the end of the code. The remainder of
its inputs are grounded as previously discussed.
Flip-flops 101 and 102 are key timing elements in the
circuit. As shown on lines G ~ H of Figure 6, flip-flops ~01 and
102 are interconnected to cause flip-flop 101 to produce equal
length HIGH and LOW pulses at its Q output for each HIGH or LOW
Output pulse from the Q output of flip-flop 102. For example,
when flip-flop 102 produces a long duration HIGH 170, flip-flop
101 produces ~IGH 171 followed by LOW 112 with each being half
the duration of HIGH 170. Thus, flip-flop 102 changes state once
for each two changes of state of flip-flop 101. The clock and
timing generator shown generally at 34 places the sequence of
timing pulses, as indicated on line F, on lead 35 which clocks
flip-flop 101 and inputs to several gates. The output levels on
Ql~ Ql~ Q2, and Q2 are utilized to control various gates in the
lamp control circuits.
A starting sequence for the flash control system may be
illustrated by assuming that the circuits are in the condition
indicated by the "start" arrow on line F of Figure 6, with the
timing pulse lead 35 HIGH, Ql and Qz LOW, and lamp OFF. Counter
40 wil~ be in its sixth count. As counter 40 completes its sixth
count which appears at output 5, the counter 40, as will be
shown, will step to its N + 1 or seventh count which appears at
output 6 and is connected via OR gate 132 to the reset input of
counter 40. The reset pulse to counter 40 also resets both flip-
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12~7~6
flop 101 and 102. At this point, Ql and Q2 are both LOW. When a
negative-going timing pulse appears on lead 35 from timîng gener-
ator 34, all inputs to NOR gate 110 will be LOW producing a HIGH
at its output. OR gate 126 output will then be HIGH, producing a
~IG}1 si~nal a~ one input of NOR gate 112 and of NOR gate 114. NOR
gate 114 will produce a LOW at one input of OR gate 124 which has
a LOW on its other input from NOR gate 112. Thus, the LOW pro-
duced at the output of OR gate 124 turns off transistor 141.
The collector of transistor 141 connects to input X of
Figure 4 which controls lamp switching transistor 92 via transis-
tors 98 and 99. When transistor 141 is conducting, point X is LOW
cutting off the current to lamp 24. Thus, when OR gate 124 turns
off transistor 141, the lamp switch is enabled and turns the lamp
24 on. The action of START timing pulse 174 in going LOW also
places a HIGH from the output of NOR gate 110 on one input of NOR
gate 120. Both Ql and ~2 are then HIGH producing a HIGH at the
input of NOR gate 118 which has a LOW input from lead 35. Thus,
NOR gate 120 produces a LOW output, turning transistor 125 on,
causing its collector and sync output lead 37 to go HIGH. This
produces the leading edge of sync pulse 178 on line S of Figure 6.
It may be noted that sync pulse 178 occurs at essentially the
same time as START timing pulse 174. when START timing pulse 174
goes positive ~trailing edge), flip-flops 101 and 102 are clocked
producing pulses 171 and 170 at Ql and Q2 shown on lines G and H.
The output of NOR gate 110 then goes LOW causing the output of NOR
gate 120 to be ~IGH. Transistor 125 is thus turned off and lead
37 goes LOW. The action just described therefore produces sync
pulse 178 on lead 37. when transistor 125 turns on, transistor
121 also turns on and transistor 123 turns off.
Prior to ~TART timing pulse 174, transistor 123 was on,
charging capacitor 145. When the first sync pulse 178 occurs,
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~Z~17~)~6
one input of AND gate 136 goes HIGH with the other input being
~IGH from the charge on capacitor 145. Therefore a HIGH appears
at the output of A~D gate 136. Resistor 143 is selected to dis-
charge capacitor 145 to inhibit AND gate 136 before the end of
the sync pulse 178. This action results in sync pulses 178 and
180 being duplicated on lead 161 but of shorter duration to pre-
vent lead 161 from remaining high which would cause a lock-on
condition at the reset input of transistor 139. Flip-flop 101
and 102 are set by the short set pulses 182 (line J of Figure 6)
and are reset by short pulses 183 through gate 132 which also re-
sets counter 40. The short pulse 183 on lead 161 to AND gate 138
is also conducted to the base of transistor 139 of clock and
timing generator 3~, resetting the generator. AND gate 106 has
both inputs HIG~; therefore, the reset pulse is propagated to re-
set counter 40.
It may be noted ~hat tpe output of NOR gate 118 goes HIGH
during the timing pulse 176 which occurs at the middle of each
flash in the flash sequence. When the ZERO counter output shown
on line M is present, timing pulse 176 produces second sync pulse
180 on line S of Figure 6. This pulse is therefore propagated
through NOR gate 120 to cause the signal on sync output line 37 to
go HIGH. Inverter 130 whose output is connected to one input of
AND gate 128 serves to inhibit a reset pulse which might occur
from a distant unit during the last count of counter 40 if the
last flash were a long one. Second sync pulse 180, which appears
on sync output 37, will be transmitted to all other flasher
systems in the network, and will reset each of the counters in
the other flasher systems connected to sync line 37 through their
corresponding gates 136, 138, 106, 128 and 132. If all of the
flasher systems in a group were not synchronized, the first
flasher system to reach the ZERO count will cause generation of
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07~G
the sync pulse 1~0 and will reset all of the others except any
which happen to be on the last count. However, when such a unit
goes to its ZERO count, the sync pulse generated will in turn re-
set and therefore resynchronize all of the other units to that
unit.
From the description above of the turn on sequence of the
lamp, it will be seen that turn off of the lamp is controlled by a
LOW input to NOR gate 114 which places a HIGH input on OR gate 124
turning on transistor 141. Transistor 141, when conducting,
places a LOW on the X input to the lamp switching circuits of
Figure 4 causing the lamp to be turned off. NOR gate 112 acts as
a latch to hold transistor 141 on until the next turn on signal
occurs. During a turn on pulse, a HIGH signal from the output of
AND gate 104 sets flip-flops 101 and 102 causing Ql and Q2 to go
LOW. During an eclipse, transistor 105 is conducting and charges
capacitor 107 permitting a sync signal on AND gate 104 to produce
a HIGH at the output for set~ing of flip-flops 101 and 102. Tran-
sistor 105 turns OFF, permitting discharge of capacitor 107 which
inhibits AND gate 104. The set pulse is thus shortened and
canno~ appear again during a flash period since the capacitor
will remain discharged. It may be noted that during synchroniza-
tion, both the sync pulse and the counter reset pulse from the
output of AND gate 138 will also appear at transistor 139 in the
clock and timing generator causing it to reset as wiIl be dis-
cussed below.
The next timing pulse 176 will occur while Ql and Q2 are
both HIGH as shown by pulses 171 and 170 in Figure 6. Lead 35 to
one input of NOR gate 118 will go LOW. The ZERO output of counter
~0, as seen on line M of Figure 6, will be HIGH and inverter 122
will cause a second input to NOR gate 118 to go LOW. Ql and Q2
outputs are LOW, cau~ing a LOW from the output of OR gate 116 to
~,-
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!~
~Z~7C~16
the third input of N~R gate 118. Thus, its output is HIGH to one
input of NOR gate 120 whose other input is held LOW by NOR gate
110. The output of NOR gage 120 then goes LOW turning on transis-
tor 125 to produce the HIGH sync pulse on output lead 37 as pre-
viously described. At the end of timing pulse 176, the input to
NOR gate 118 goes HIGH causing sync output line 37 to go LOW. It
is to be noted that the enabling of the sync pulse by means of NOR
gate 118 requires that the input from counter 40 via inverter 122
produce a LOW on that input to NOR gate 118. This can only happen
during the ZER~ count and therefore no sync pulses appear during
the rest of the cycle. The reset pulse produced on lead 161
during the second sync pulse 180 during the ZERO count will again
reset clock and timing generator 34 and will also be pacsed
through AND gate 1~6, AND gate 128, and OR gate 132 to the reset
terminals of flip-flops 101 and 102. As may now be recognized,
sync pulses 178 and 180 on sync output 37 will appear at all of
the other interconnected flash lamp systems. An incoming sync
pulse will be conducted via the units own gates 136 and 138 to its
clock and timing generator, resetting the same and, via gates
106, 128 and 132, resetting the counter. This will start that
unit in synchronism with the transmitting unit to provide the de-
sired simultaneous flashing among all units in the system. on
line L in Figure 6, a series of inhibit pulses are shown. These
negative going pulses are produced by gate 140 during the last
half of each flash period to inhibit gate 138 which prevents the
unit from resetting on an incoming sync pulse arriving during
such time.
Turning now to the circuits of the clock and timing gen-
erator shown generally at 34 in Figure 5 and with reference to
line F on Figure 6, its operation will be described. Timing
generator 34 utilizes transistor 137 and transistor 139. The
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~2~37~316
base of transistor 137 is held at a fixed bias voltage by the vol-
tage divider formed by resistor 43 and variable resistor 47.
Variable resistor 47 may be adjusted to provide the desired bias.
Transistor 139 is non-conducting during the period between timing
pulses such as STA~T pulse 174 and pulse 176 of Figure 6 thereby
producing a HIGH output on lead 35. When transistor 139 con-
ducts, its collector voltage drops producing a LOW on lead 35
during a timing pulse. Immediately after a timing pulse, one of
the bilateral switches 52, 5~, 44 or 46 is closed by the selected
gating circuits causing capacitor 68 (Cl) to begin to charge
through the selected resistor. Using timing pulse 174 of Figure
6 as an example, switch 52 is closed connecting resistor 64 to
the +V regulated power supply, charging capa~itor 68. When the
voltage on capacitor 68 rises sufficiently to overcome the bias
on the base of transistor 137, that transistor will conduct
placing a HIGH on the base of transistor 139 whose collector then
goes LOW as described above. The charge on capacitor 68 will be
dumped by diode 149 with diode 147 serving to hold the output of
resistor 64 LOW to prevent recharge of capacitor 68 during the
timing pulse period. ~hen the charge is quickly removed from
capacitor 68, the LOW at the collector of transistor 139, in a
regenerative fashion, cuts off transistor 137 permitting capaci-
to} 68 to recharge through resistor 64 connected to capacitor 68
by switch 52. I~ is to be noted that switch 52 has been held ON
by the ZERO count output from counter 40 as shown on line M of
Figure 6 and is therefore still conducting. Diode 147, as noted,
prevents recharging of capacitor 68 during the timing pulse 176
which occurs at the center of a flash or an eclipse. As may also
now be seen, a reset pulse from AND gate 138 to the base of tran-
sistor 139 will cause transistor 139 to conduct producing a
timing pulse and starting a new timing cycle.
~2(~7C~16
Bilateral switches 52, 58, 44, and 48, which may be ele-
ments of a quad switch 160, are closed by their respective AND
gates 152, 154, 156, and 158. When a short flash is required,
such as 184 on-line T of Figure 6, during count TWO o~ co~nter 40,
START timing pulse 185 clocks flip-flops 101 and 102 causing HIGH
186 at Q2. This HIG~ appears at one input of AND gate 156 which
has a HIGH on its other input from OR gate 146 whose inputs are
all LOW. Thus, a HIGH at the output of 156 turns on gate 44 for
the period that Q2 remains HIGH. when STOP timing pulse 187
occurs, flip-flop 102 is clocked by flip-flop 101 producing the
LOW at Q2 shown at 189 in Figure 6. Short eclipse 188 on line T
is next required and is accomplished by the HIGH from Q2 appear-
ing at one input of AMD gate 158 with the other input being HIGH
from the output of NOR gate lq8. Switch 48 is therefore closed
connecting resistor 62 to charge capacitor 68. Since resistors
60 and 62 in this instance have equal values, the charging times
will be the same as for the short flash and therefore transistor
141 will be controlled to maintain the lamp off during eclipse
188 for the same time period as flash 184. It is to be emphasized
that it is not necessary that the short flash and short eclipse
have the same duration. For example, resistor 60 may be selected
to produce a short flash of 0.3 seconds and resistor 62 selected
to p.roduce a short eclipse of 0.7 seconds.
The long flashes and long eclipse are controlled by
switches 52 and 58, respectively, with gates 152 and 154 main-
tained inhibited during short flashes and eclipses by the invert-
ing action of inverter 144 and NOR gate 150. When a long flash is
required, such as at count ONE, the count pulse 190 on line N of
Figure 6 is applied to one input of NOR gate 146 producing a LOW
at its output which via inverter 144, places a HIGH on one input
of AND gate 152. The other input receives a HIGH from Q2 turning
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~2~i7(116
on swi-tch 52. Similarly, a long eclipse is ob-tained by a
HIGH on NOR gate 148 which in this case would occur at
count FIVE, 191 on line R of Figure 6.
NOR gate 150 between NOR gate 148 and AND ga-te
154 is advantageously utilized in the daylight, con-trol
circui-t shown generally at 70 to disable the flashing system
during dayligh-t hours and to s-tart the sys-tem durin~ night
time or heavily overcast conditions. During the day when
sufficient light falls on photocell 72 to make the minus
input of comparator 162 lower -than the plus inpu-t, its
output will become HIGH, causing the output of NOR ga-te
150 to be LOW, inhibiting AND gate 154. However, the above
action will take place only when AND gate 164 is enabled
by Ql and Q2 being high simultaneously. As evident from
Figure 6, this condition occurs only during the last half
of each eclipse. Thus, when the sequence reaches the second
half of the next long eclipse, AND gate 154 is disabled,
capacitor 68 will discharge turning transistor 137 on.
Capacitor 68 cannot recharge since switch 58 remains open
until comparator 162 changes state again. ThereEore, the
clock and timing lead 35 will remain HIGH and the flashing
sequence will stop. When the light on photocell 72 drops
low enough to cause the voltages at the input of comparator
162 to change so as to put a LOW at its output when AND
gate 164 is enabled by HIGHS on Ql and Q2' this action
will enable OR gate 150 -to permit capacitor 68 to recharge.
AND gate 164 is disabled by a LOW on Ql of flip-flop 101
during the first half of each eclipse, disabling comparator
162. This action prevents the glow from the filament of
lamp 24 during nigressence from causing shut down of the
flash system.
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~Z~7~16
Although the invention has been described hereinabove in
detail using various specific elements, it will be obvious that
many modifications can be made without departing from the spirit
and scope of the invention. For example, it is contemplated that
the circuits shown herein may be implemented in LSI thereby re-
ducing the size and cost.
. .
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