Note: Descriptions are shown in the official language in which they were submitted.
BACK(-`IRO~JNi) OF IIIF INVEN-rInN
This inventiorl relates to light climlllers, and more
particularly to devices for variably controllirlg the clirnminq of
traffic lights in accordance with predeterrmirled twilight schedules.
_IOR ART
It is known to use clock timers to control various
electrical devices, such as lights, radios, and the like. Such
devices typically suffer from the disadvantage oF fixed tinnes for
turning devices on and off, and of failing to respond to varying
requirments without manual supervision.
The use of light sensitive devices for controlling lighting
apparatus to operate during times of darkness is known. ~lowever~
such controls are known to suffer from a disadvantage of reliance
on light conditions, so that the apparatus may be turned on during
daylight hours, for example, as a result of cloudy atmospheric
conditions.
; There is no provision made in the prior art, however, for
control of power consuming electrical apparatus in a reliable manner~
in which electrical power supp1ied to the apparatus is automatically
altered as a function of daylight times yet independently of actual
light measurement.
SUMMARY OF T~IE INVENTIO~I
_.___ _ _ _ _ _
To alleviate a number of the problems presented by the
prior artI a device is utilized which is capable of chang~ng the
power input to a power utili~atlon device In accordance wi-th a
pre-selected time sequence. Such a device is particularly useful in
controlling power input to traffic lights in accordance with a daily
schedule of hours of light and darkness, so that, For exam~le, the
lights are dimmed during darkness hours to thereby consume less
energy.
Accordingly, in general terms the invention provides a
control apparatus for reducing power supplied to utilization devices
comprising storage means for storing particular times for providing
the reduced power, time keeping means for determining present time,
comparing means for comparing present time with the stored times for
15 providing the reduced power, and activating means responsive to the
comparing means for providing appropriate power to the lighting
devices.
In a more specific embodiment the invention provides an
electronic control circuit, including a storage device for a schedule
20 of control times for an entire year, in ~Ihich a comparison of the
present time and stored time for a particular day is performed and
evaluated in accordance with a determination of whether the present
time is AM or PM. The invention provides circuitry for activating or
deactivating a power reduction device in accordance with the results
25 of the comparison. Moreover, the invention provides addressing
circuitry for the storage device which is itself responsive to a
signal indicative of whether the present time is AM or PM.
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In accordance wi-th the other features of the invention, the
circuitry includes a day counter and a week counter, the latter being
used to ad(lress the storage device which includes thereln a schedule
of twilight tinles For a speciFic latitut(le For an entire year, stored
5 as weekly twilight times. The day counter is responsive to
generation of a transition between a PM signal and an AM signal, and
itself is used to trigger the week counter.
. ~ - 3 -
A clisplay means is provicled for the electronic clata use(l in
the control circuit ancl m()re specificall~y for the present time the
contents o-f the day counter and the corlterlts of the week counlfr.
The data are multiF)Iexecl For clisplay on a single display clevice.
The electronic device of the present invention is used for
conserving electrical energy by dimming tra-ffic 1ights in accordance
with a predetermined schedule determined by sunrise and sunse-t times
for the location of the traffic lights.
BRIEF DESCRIPTION OF Tl-lE DRAWINGS
______ ________ .
The foregoing and other objects features and advdntdges of
the invention will become more readily apparent upon reference to the
following detailed description of the preferred embodiment when
taken in conjunction with the accompanying drawings in which like
numbers refer to like parts.
FIGURE I shows the inventive circuit in generalized block
diagram form.
FIGURE 2 shows a portion of the actual circuitry used to
realize the embodiment of FIGURE 1 in schematic representation.
FIGURE 3 shows a further portion of the ernbodiment of
FIGURE 1 including the counters for days and weeks and a
multiplexing arrangement therefor.
FIGURE 4 (located with FIGURE 1 on the first paye of
drawings) shows the display portion of the invention along with a
switching arrangement for displaying the time or the contents of the
day and week counters thereon.
~L~ 4~
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
In accordance with the present invention, an apparatus is
shown for reducing the voltage applied to traffic signal lights
during nighttime operating hours to effect substantial savings in
energy consumption thereby. It is appreciated that the disclosed
apparatus, or similar, moderately varied versions thereof, may be
used in other applications, including but not limited to control of
motors, lighting, assembly line devices, power distribution, and the
like.
Referring now to FIGURE 1, the present embodiment of the
invention is generally shown at 10. As seen therein, the invention
is comprised of three basic portions.
A first portion, identified by reference rumeral 12,
includes therein the various timekeeping devices, storage devices,
comparison and logic circuitry, and activating circuitry for the
dimming device. A second portion, identified by reFerence number 14,
includes the day and weeks counters used in the invention, as well as
a multiplexing arrangment for the outputs thereof. Finally, a third
portion, identified by reference numberal 16, includes a display
apparatus, receiving the output of the multiplexing arrangement and
of the clock mechanism for display, and a control means therefor.
Referring to the first portion 12, a storage device 18 is
provided for storing time data, or schedules, for activating or
deactivating a dimming device for the lights to be controlled.
A clock 20 is provided for keeping present time, the clock
providing outputs on lines 22, containing the time data, and on lines
o
24, containing data. The time output clata on lines 22 is provided in
seven-segment forma-t, for display on seven-segment display devices.
A strobe generator circui-t 25 uses the control signals to provide
strobe signals to the display. /\ decoding circuit 26 is provided for
5 converting the seven-segment data on lines 22 to BCD (binary coded
decimal) format, for use in comparison and other computation
functions.
The decoded present tirne data, provided on output lines 28
of decoding circuit 26, is compared with the s-tored schedule data
l0 from storaye device 18, provided on output lines 30 thereof. The
comparison of the present time with the stored time data is made in a
comparator 32, providing an output on line 34 indicative of whether
present clock time is greater or less than the -time output from
stora~e device 18.
A logic device 36 receives the output of comparator 32 and,
responsive thereto, operates an activating ci rcuit 38 for a dimmer
(not shown). Inasmuch as a comparison transition from a "less than"
comparator output to a "greater than" output is indicative that the
present time has passed the scheduled point of activation, but is not
20 indicative of whether the activation should be energization or
deenergization of the dimmer, additional information is provided to
the logic device for deciding on the appropriate response to the
transition.
An AM/PM circuit 40, responding to the decoded time output
25 by decoding circuit 26, provides an indication on output line 42 of
the particular time segment (AM or PM) identifying the present time.
Logic device 36, determining that comparator 32 has undergone a
~2Z~
transition during an AM interva1, thus provides ar1 outpu-t to
activating circuit 38 indicatirlg that the dim1ner should be
deactivated, in order to provide full ligr1ting intensity durin~
daytime. On the o-ther hand, when 10gic device 36 deterrr1ines that the
transition of comparator 32 occurs during a PM interval, -the ou-tput
signal provided thereby is used to cause activating circuit 38 to
activate the dimmer, thereby reducing the light intensity during the
evening and night hours, and providing the desired saving in energy
dissipated by the controlled traffic light.
The data stored in storage device 18 thus need not include
any control data (i.e~5 "activate" or "deactivate") information, but
need only include comparison times representative of sunrise and
sunset, for example. Such control data may be stored, however along
with the desired comparison times, in which case the logic device 36
may be replaced by a decoding circuit to provide the appropriate
output to activating circuit 38 in response to the appropriate stored
control data.
It is appreciated that actual dimming and brightening -times
for the controlled traffic light devices need not coincide with
sunset and sunrise. These control times may, in Fact, provide for
dimming the lights a particular time increment after sunset, and may
provide for brightening the lights a similar time increment prior to
sunrise. Moreover, it is understood that where other devices are to
be controlled by the present invention, the times for activating and
deactivating the power reduction device need not have any
relationship with times for sunrise or sunset. Any desired time
scheduling may be used. However, for simplicity and consistency in
~?,~
language herein, the terms sunrise and sunset continue to he used to
indicate the stored times in storage device l~ for deactivating and
activatirlg -the power reduction device.
Further, in such other applications not related to sunrise
and sunset tlmes, it may be more convenient to determine other time
segments than AM or PM times. For example, where one con-trol signal
(e.g., activate power reduction device) is typically given in a first
time segment, such as 3:30 PM to 10:00 PM, and -the other control
signal (e.g., deactivate power reduction device) is typically given
in a second tirne seglnent, such as 10:01 PM to 3:29 PM, then AM/PM
circuit 40 may be replaced by a detector for the OUtpllt of decoding
circuit 26. The detector need only provide a first signal during the
first time segment, and a second signal during the second time
segment, for instructing logic device 36 on how to respond to the
determination that a transition has occurred in the output of
comparator 32.
It is an advantage of the present invention that a schedule
of non repetitive times for activating or deactivating any device may
be stored. The schedule may cover an arbitrarily long time period,
such as a year, for example. A year is a particularly appropriate
time period for light dimming devices, inasmuch as sunrise and sunset
times vary at a yearly repetition rate. For the specific preferred
embodiment, wherein traffic control lights are dimmed during the
night-time hours, it is known that sunrise and sunset times vary
relatively slowly, and that for predetermined periods of time they
may be considered to be relatively constant. Particularly, it is
known that the changes in sunrise and sunset times over any one-week
periocl are typically limitea to a few mirlutes at most;.
As d savings in storage re(luirement, the present invention
accordingly stores -the activating and deactivating schedule in terms
of the selec-ted time periocls where such schedule times vary by the
above mentioned Few minutes. That is~ only weekly sunrise-sunset
time shcedules are s-tored in storage clevice 18.
Whether the time period during which the stored schedule
may be considered to remain substantially constant is a week or any
other period, however, apparatus is provided for counting such
periods, in order to address the particular data in storage
corresponding -to the particular present period. In the present
preferred embodiment, second por~ion 14 is seen to include a day
counter 44 and a weeks counter 46, the output of the weeks counter
being used to address storage device 18 at its address inputs 48.
The day counter is triggered by detection of transition of AM/PM
circuit 40 to an AM output. Accumulation of a count of seven days in
day counter 44 is used to cause weeks counter 46 to increment its
count by one.
Thus, for any day within a particular week, the sunrise/
sunset schedule for that day is obtained from a location within
storage device 18 which is addressed by the contents of weeks counter
4S. The embodiment of FIGURE 1 further provides for obtaining the
particular time for comparison (i.e., sunrise or sunset) from the
storage device by a further address input 50, receiving the output of
AM/P~ circuit 40.
The appropriate comparison time is thus obtained by a
combined address, formed of the week number and an indication of AM
4~
or PM time segment, cornparecl with present time in comparator 32, and
appropriate action taken by logic device 36 in accordance with the AM
or PM s-tatus.
For convenience of the user, the present invention includes
a display 52, for displayiny -the present tirne, the contents of the
day counter, and the contents of the week counter. A multiplexing
arrangement, shown as multiplexer 54, is used to provide the contents
of counters 44 and 46 to the display. A control 56 is provided for
controlling display 52, in order to display the contents of clock 20
or counters 44 and 46.
Referring now to FIGURES 2-4, the detailed structure oF the
present invention is shown in terms of specific interconnections of
commonly available circuit chips. As shown in FIGURE 2, clock 20 is
comprised of a 24 hour clock chip of the type 7045, timed by a quartz
crystal 58, which supplies multiplexed, seven-segment encoded
hour/minute information together with five digit strobes. Four of
the strobes are used to excite the four-digit, seven segment display
of FIGURE 4 and for latching digit information into decoding circuit
26, formed of four seven-segment to BCD decoders of the type 74C915.
A fifth strobe is used as a system trigger for proper timing of
comparison and control functions.
The strobe signals are processed by strobe generator
circuit 25, formed of a plurality of NAND gates receiving one input
from an inverting amplifier at the output of the clock ship and a
second input from a control switch for deactivating the display.
The schedule of morning and evening twilight data, ordered
by week from 1 to 52, is stored in a pair of programmable read only
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memory chips of the type 2-/58. The inFormation is arrange(l wi-thin
the PROMS as follows. Locations 1 through 52 contain the sunrise
information, by week, ancl locations 10L -through 152 inclu(le surlset
information, by week.
The AM/PM circuit qO is seen to decode the BCD time
information, output by the seven segmen-t to BCD decoding circuit 26,
by setting a flip flop (type 4027, for example) in response to a time
of 23 hours, 40 minutes and resetting the flip flop at 12 hours, O
minutes. The setting of the flip flop at 23 hours 40 minutes,
instead of at O hours, O rninutes, is chosen for hardware and space
limitations, and does not affect operation of the circuit inasmuch as
none of the stored times are in the range of 11:40 PM to nnidnight.
The outputs of the decoding circuit 26 and the PROMs are
compared in comparator 32, formed of four 4-bit comparators of the
type 74C85. The results of the comparison, along with AM and PM
outputs of circuit 40, are provided to logic device 36, formed of a
number of AND and OR gates connected to set and reset a second 4027
flip flop. As will be appreciated by those skilled in the art, logic
device 36 sets flip flop 4027, which forms activating circuit 38,
when the output of circuit 40 indicates an AM situation and the
present time is less than the stored (sunrise~ time, or when the
output of circuit 40 indicates a PM time and the present time is
greater than the stored (sunset) time. Alternatively, activating
circuit 38 is reset when it is AM and the present time is greater
than the stored time, or when the present time is less than the
stored (sunset) time and the output of circuit 40 indicates PM. The
output of activating circuit 38 provides a signal to a low pass
1 1
~%~ L4~
circuit, formetl of a cdpacitor 60 and a resis-tor 62, and then to a
relay For energizirlg the dilrl control circuit.
The multiplex rate of the clock is apF)roxirlldtely 1()() ~Iz,
which is also used as -the rate for comparisorls an(i logicdl decisiorls
in the inventive circuit. Provision of the low pass circuitry is
advantageous in filtering out any faulty comparisons, which are made
at the 100 Nz rate, prior to activating the energizing relay 64 for
the dim-corltrol circuit, thus correcting errors prior to displaying
the results of such errors.
A transition in the output of AM/PM circuit 40 from PM to
AM is used to cause day counter 44, formed of one half a 4518
counter9 to count an additional day, as seen in FIGURE 3. Upon
reaching a count of seven days, gating circuitry 66 is used to cause
weeks counter 46, formed of a 4518 counter as well, to advance its
l 5 count.
As seen in FIGURE 2, the eight outputs of weeks counter ~5
are used to address eight of the input address lines of the PROMs
used for storage device 18. The ninth address line is addressed by
the PM output line of AM/PM circuit 40. The combined address inputs
thus access locations 1-52 and 101-152, as previously described, ancl
provide the appropriate stored time information (sunrise or sunset~
for comparison with the appropriate present time segment (AM or PM,
respectively).
Referring once again to FIGURE 3, multiplexer 54 is seen to
be formed of a plurality of AND and OR gates to provide a single set
of four BCD outputs from three input sets of Four BCD inputs, each.
Referring now to FIGURE 4, the four multiplexed BCD outputs from
~l2;;~
FIGllRE 3 are seen -to be input to a BCD to seven-segment clecocler 6~,
formed of a 4511 chip. The inpu-ts are providecl at 70. As is a'lso
seen from -the Figures, the seven-segment clock outputs dt 22 are also
input to -the display, to a p'lurality of enabling AND gates each
having one input connected to control 56. Control 56 comprises a
switch 72 for grounding and disabling the AND gates, thereby passing
the output of BCD to 7 segment decoder 68 for display. Alter-
natively, the switch may be used to disable the decoder 68, and to
pass the output signals from clock 20 for display.
The output signals From strobe generator circuit 25 are
used to strobe the appropriate one of the four digits in the display,
thus providing either the time (in hours and minutes) or the day and
week count for disp'lay in the apparatus.
It is appreciated that the above described preferred
embodiment may also be realized using a single chip microprocessor to
implement the timekeeping, comparison, storage and display
maintenance functions similarly to the above described structure.
Moreover3 in terms of the schedules of twilight times, sunrise and
sunsets, and the like, stored in the circui~, it is known that such
schedules are a function of the geographical latitude of the
observer. Accordingly, it is contemplated that complete tables of
sunrise and sunset times may be stored permitting accessing or
computation of precise twilight times for any number of latitudes.
One contemplated approach is to provide tables encompassing the
latitudes from zero to 63 north and south, as well as tables
varying by one degree increments of longitude within a time zone.
.,
In order to assure long ter1n accuracy oF c'lock output, the
timekeeping function preferably is connectecl to operate with a power
supply from standarc1 50~1z or 60~1z AC power, and with a c1uartz
reference when line power is not availab'le~ 13ackup battery power is
to be provided for operation during interruptions in 'line power.
The preceeding specification describes the preferred
embodiment of the invention as an illustration and not a limitation
thereof. It is appreciated that equivalent variations and
modifications of the invention will occur to those skilled in the
art. Such modifications, variations and equiva'lents are within the
scope of the invention as recited with greater particularity in the
appended claims, when interpreted to obtain the benefits of all
equivalents to which the invention is fairly and legally entitled.
'14
