Note: Descriptions are shown in the official language in which they were submitted.
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ENHANCED VISIBILITY TRAFFIC SIGNAL
FIELD OF THE INVENTION
The present invention relates generally to tragic signals and relates more
particularly to
an enhanced visibility traffic signal, such as a stop sign, which has a
plurality of lights, such as
light emitting diodes, or LEDs, disposed thereupon, so as to attract attention
thereto in a manner
which makes the traffic signal more likely to be seen and obeyed.
BACKGROUND OF THE INVENTION
Tragic signals for regulating the flow of traffic upon roadways are well
known. Common
examples of such traffic signals include stop signs, yield signs and speed
limit signs, as well as
a plurality of other signs and the like which are intended to control traffic
and/or to provide
helpful directions.
Of these various different traffic control signs, stop signs are particularly
important
1 ~ because failure to obey a stop sign is especially likely to result in an
automobile accident. Such
automobile accidents frequently result in undesirable automobile damage,
personal injury and/or
death. Of course, the failure to obey various other traffic control signs and
the like also
frequently results in such automobile accidents.
Occasionally, the failure to obey such critical traffic control signs results
from a difficulty
or inability to see the traffic control sign. Sometimes not seeing such
traffic control signs results
from nearby distractions, which cause the driver to pay attention to something
other than the
traffic control sign. Other times, the trafFc signs may be partially
obstructed by foliage, or the
driver may merely be inattentive. In any instance, drivers occasionally
overlook critical tragic
control signs and thereby risk automobile damage, personal injury and death.
Further, the ability of a driver to see traffic control signs and the like is
generally
dependent upon the ambient lighting conditions. For example, traffic control
signs are
substantially more difficult to see during periods of darkness or near
darkness as well as during
adverse weather conditions, e.g., overcast, fog, rain, sleet or snow.
Contemporary stop signs having LEDs formed thereon are known. For example,
clusters
of LEDs are being used to replace the red incandescent lights in the traffic
signals, where 300
or more LEDs are clustered together to provide sufl-icient brightness. Such
contemporary
illuminated signs have been used by the prior art in an attempt to mitigate
the above described
problems associated with the difficulty or inability to see stop signs during
darkness, near
darkness and adverse weather conditions. However, such contemporary
illuminated stop signs
utilize LEDs which have a typical brightness of 1,500 millicandella or less
and which thus do
not contribute substantially to enhancing the visibility of the stop sign.
Further, the total
included radiation pattern angle of the LED clusters in such contemporary
illuminated stop signs
CA 02337057 2003-12-17
is generally greater than 20 degrees, thus undesirably reducing their
effectiveness to
be visible at a distance or in adverse conditions.
Those skilled in the art will appreciate that the ability of LEDs to
contribute to
enhancing the visibility of a stop sign or the like is dependent upon the
brightness of
the LEDs and also the radiation pattern angle thereof. Greater brightness
provides
more light, thus making the LEDs easier to see. A smaller radiation angle
concentrates the available light, again making the LEDs easier to see.
In view of the foregoing, it is desirable to provide traffic signals having
enhanced visibility, so as to enhance the likelihood of the traffic signal
being seen and
obeyed and thereby mitigate the likelihood of accidents occurring as a result
of failure
to observe the traffic signal.
SUMMARY OF THE INVENTION
The present invention specifically addresses and alleviates the above-
mentioned deficiencies associated with the prior art. More particularly, the
present
invention comprises a traffic control signal enhanced visibility indicia
comprising:
a structure having traffic control indicia formed thereon;
a plurality of LEDs each with an output intensity of at least 6,000
millicandella; wherein each such LED is disconnectable without interrupting
the
operation of any other such LED, and wherein each such LED has a light output
beam
radiation angle of about 20 degrees and is individually mounted on the
structure in a
space-apart relationship from an adjacent LED to thereby provide discrete
points of
light as viewed by oncoming traffic;
a power source for providing direct current to the plurality of LEDs mounted
or the structure, wherein said power source includes a solar photovoltaic
panel and a
rechargeable battery;
a blink cycle timer for causing the plurality of LEDs to blink at a desired
frequency; and
a control circuit for regulating the operation of the traffic control signal
and
the blinking of the plurality of LEDs.
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The LEDs of the present invention preferably have a brightness of between
approximately 6,000 millicandella and approximately 60,000 millicandella.
The present invention also provides an enhanced visibility system for a
traffic
control signal comprising:
at least two LEDs mounted individually in a space-apart relationship from one
another on a structure as compared to their diameter and the structure;
a control circuit for effecting blinking of each such LED; and
wherein each such LEDs has an output intensity of at least 6,000 millicandella
and a light beam radiation angle of less than 20 degrees, each LED is further
configured to protrude from the structure on which it is mounted.
Thus, as those skilled in the art will appreciate, the traffic control sign of
the
present invention has substantially enhanced visibility, particularly in
darkness, near
darkness and in adverse weather conditions. The substantially enhanced
visibility of
the present invention is provided by the greater brightness and reduced
radiation
pattern angle of the LEDs utilized.
In a further aspect, the present invention provides a method for enhancing the
visibility of conventional traffic signs or structures by mounting a plurality
of LEDs
thereupon such that the output light from each LED is aimed approximately
towards
oncoming motor vehicle traffic, wherein each of said individual LED:
can be disconnected from said traffic sign or structure without interrupting
the
blinking operation of any remaining LED thereupon;
provides an output light intensity of at least 6,000 millicandella;
is spaced apart from an adjacent LED as compared to the LED's diameter and
the structure;
is provided with appropriate direct current electrical power derived from
sunlight by suitable solar photovoltaic panel, rechargeable battery and blink
cycle
timer circuit means; and
blinks once every 0.2 to 5.0 seconds as effectuated by the blink cycle timer
and when blink has a light pattern that is comparatively small independent of
any
shield.
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CA 02337057 2003-12-17
In a still further aspect, the present invention provides a method for
enhancing
the visibility of conventional traffic signs or structures by locating eight
discrete,
individually-mounted LEDs thereupon such that the output light for each LED is
aimed approximately towards oncoming motor vehicle traffic, said LEDs forming
at
least one of a recognizable geometric pattern and approximately defining the
physical
size of the sign or structure, wherein each of said individual LEDs:
provides an output light intensity of at least 6,000 millicandella;
has an external diameter not exceeding about 10 mm;
is provided with appropriate direct current electrical power from a blink
cycle
timer and battery rated at 1600 mAh; and
blink once every 0.2 to 0.5 seconds as effectuated by the blink cycle timer
and
a control circuit, wherein said eight LEDs operate continuously in blink mode
at a
duty cycle of 50% without any addition of external power to the battery for a
period
of at least about 50 hours.
These, as well as other advantages of the present invention, will be more
apparent from the following description and drawings. It is understood that
changes
in the specific structure shown and described may be made within the scope of
the
claims without departing from the spirit of the invention.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an electrical schematic showing a solar-powered battery charging
circuit for the enhanced visibility traffic sign of the present invention;
FIG. 2 is an electrical schematic showing the LED control circuitry for the
enhanced visibility traffic control sign of the present invention;
FIG. 3 is a rear view of an exemplary traffic control sign having a plurality
of
LEDs mounted thereupon according to the present invention;
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FIG. 4 is a side view of the exemplary traffic control sign of FIG. 3;
FIG. 5 is an enlarged side view, partially in cross section, showing a single
LED mounted
to the tragic control sign of FIG. 3 and showing the radiation pattern angle
of the LED:
FIG. 6 is an exploded perspective view of an LED control module having a
single LED
and also having conductive conduits extending therefrom. so as to effect
control of the plurality
of other LEDs mounted upon the traffic control sign;
FIG. 7 is a block diagram of an enhanced configuration of the enhanced
visibility traffic
control sign of the present invention, having a plurality of optional circuits
for enhancing the
utility thereof;
FIG. 8 is an electrical schematic of the main control circuit of FIG. 7;
FIG. 9 is an electrical schematic of an auxiliary override circuit according
to the present
invention;
FIG. 10 is an electrical schematic showing maintenance and test circuitry
associated with
the block diagram of the enhanced utility traffic control sign of FIG. 7;
FIG. 11 is a front view of a pole-mounted stop light having a stop sign
attached thereto
such that the stop sign will be displayed if power to the stop light is
interrupted, showing the stop
sign in the stowed configuration;
FIG. 12 is an enlarged view of the stop sign of FIG. 11, showing the stop sign
in the
deployed configuration thereof; and
FIG. 13 is a cross-sectional side view of the stop sign of FIG. 12, showing
the mechanism
for holding the stop sign in the stowed position thereof.
DETAILED DESCRIPTION OF THE INVENTION
The detailed description set forth below in connection with the appended
drawings is
intended as a description of the presently preferred embodiments of the
invention and is not
intended to represent the only forms in which the present invention may be
constructed or
utilized. The description sets forth the functions and the sequence of steps
for constructing and
operating the invention in connection with the illustrated embodiments. It is
to be understood,
however, that the same or equivalent functions and sequences may be
accomplished by different
embodiments that are also intended to be encompassed within the spirit and
scope of the
invention.
Referring now to FIG. 1, the battery charging circuit of the present invention
is configured
so as to mitigate problems associated with over charging which may occur when
the ambient
temperature is excessively hot, e.g., on very sunny days. Those skilled in the
art will appreciate
that excessive charging of some rechargeable batteries, particularly when the
temperature of the
battery is high, is undesirable.
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1 The battery charging circuit of the present invention is also configured so
as to avoid
excessive discharging of the battery through the solar panel during period of
reduced
illumination, e.g., at night or in adverse weather conditions.
Resistors 11, 13, and 14 provide desired biasing to transistor 15 which
functions as a
S switch so as to significantly decrease the current path between the battery
10 and the solar panel
18 when the temperature of temperature-sensitive resistor, or thennistor 17 is
raised above a
predetermined threshold value. Thus, thermistor 17 functions as a temperature
sensor, so as to
provide a control input to transistor 15, which allows significant current
flow from the solar
panel 18 into the battery 10 only when the ambient temperature is below the
predefined threshold
value. Thus, the lifetime of the battery is extended by reducing the charging
current as ambient
temperature increases.
In operation, the thetmistor 17 and the 6.8K resistor 14 form a voltage
divider. As
temperature increases, the thetmistor resistance decreases, causing less
current to flow through
the 6.8K resistor 14 and thereby decreasing the battery charging current.
Conversely, as
temperature decreases, the reverse effect takes place. The thermistor 17
preferably has a
resistance of l OK at 77 degrees F and the resistance varies within a typical
range of about 27K
at 32 degrees F to 4K at 120 degrees F.
Diode 12 inhibits undesirable discharging of the battery 10 through the solar
panel 18
during conditions of reduced ambient lighting, such as at night when the
voltage developed by
solar panel 18 may be less than the voltage charge of the battery I 0.
The present invention preferably comprises either one or two 12 vdc, 1600
milliamp-hour
rechargeable nickel metal hydride (NiMH) batteries. The solar panel preferably
comprises an 18-
volt maximum open-circuit, 6 watt, Siemens SM-6 solar panel, rated 330 mA, but
in normal
sunny condition provides about 200 mA maximum, and in shady, dim, or bright
foggy
conditions, provides about 24 to 32 mA at 12.3 volts sufficient for battery
recharging.
Referring now to FIG. 2, one preferred embodiment of the present invention
comprises
a solar panel 20 coupled so as to charge a battery 21. substantially as shown
in FIG. 1.
Thermistor 22 is coupled so as to inhibit charging of the battery 21 by the
solar panel 20
when ambient temperature exceeds a predetermined threshold value. Biasing
resistors 23, 24 and
25 cooperate with thermistor 22 so as to cause transistor 26 to conduct
substantially only when
ambient temperature is below the predetermined threshold value. Transistor 26
is preferably
mounted to a 3/16-inch diameter can, or the like, which will function as a
heat sink therefor. In
this manner, undesirable charging of the battery 21 by the solar panel 20
during periods of hot
temperature is avoided, as discussed above. It is also common practice to
locate thenmistor 22
on the surface of battery 21 to thereby detect the increased temperature of
the battery itself
caused by recharging.
Diode 27 prevents the battery 21 from discharging through the solar panel 20
when
ambient lighting is insufficient to effect charging of the battery 21 by the
solar panel 20.
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On/off switch 29 allows the LEDs 45a-45h to be turned on or off either
manually or
remotely, as discussed in detail below. Diode 30 prevents reverse current flow
through the solar
panel 20 during periods of low illumination. Resistor 31 cooperates with zener
diode 32.
capacitor 36, and transistors 33, 34 and 35 to effect switching on of the LEDs
45a-45h only when
ambient illumination detected by solar panel 20 has dropped below a
predetermined threshold
value. The LEDs 45a-45h preferably comprise Toshiba TLRH 190P LEDs, or similar
high output
InGaAIP LEDs with peak emission wavelength between 560 and 660 nanometers in
the visible
light spectrum.
Each LED 45a-45h, preferably comprises a jumbo 10 mm diameter LED which
provides
a much brighter output intensity than conventional LEDs having smaller
diameters. For
example, the output intensity, measured in millicandella, is typically from
about 100 to 600 for
conventional LEDs, while the output light for jumbo LEDs is typically greater
than
approximately 6,000 millicandella.
Commercially available jumbo LEDs, which require approximately 20 milliamps of
current, may provide intensities up to 60,000 millicandella.
Such LEDs emit a very bright and comparatively narrow beam of light having a
total
included cone angle or radiation pattern angle of less than about 7 degrees.
Indeed, many types
of the jumbo LEDs have even a smaller total included cone angle or radiation
pattern angle of
less than about 4 degrees. Since traffic signs are typically pointed toward
oncoming traffic, the
emitted light from such LEDs is thereby generally pointed directly toward
oncoming traffic, and
will not be seen by traffic on side streets, thus minimizing the need for
shielding the output light
from the LEDs. Thus, the light emitted from such LEDs is more e~ciently
utilized compared
with the light emitted from contemporary, e.g., non jumbo LEDs, or LED
clusters which have
larger radiation pattern angles.
Integrated timer circuit 43 provides an output LED drive signal which
facilitates
illumination of the LEDs 45a-45h such that the LEDs 45a-45h are illuminated
according to a
desired duty cycle and a desired on time. The integrated circuit timer 43
preferably comprises
a TLC 555 ceramic metal oxide substrate (CMOS) integrated circuit. The TLC 555
integrated
circuit timer has a current drain of only 14 mA when used with eight LEDs
which are turned on
simultaneously and 1.3 mA with the LEDs turned off. The LED cathode voltage is
0.92 volts
with the LEDs on and 12.32 volts with the LEDs off.
According to the preferred embodiment of the present invention, the LEDs 45a-
45h are
mounted about the periphery of a stop sign 46. Further, according to the
preferred embodiment
of the present invention, a first LED branch circuit 48 and a second LED
branch circuit 49, each
branch containing four LEDs in series and each branch in parallel with each
other branch,
provide electrical interconnection of the LEDs 49a-49h with the integrated
timer circuit 43.
Current limiting resistors 47 and 48 limit current flow through the LED branch
circuits 48 and
49, respectively. Thus, each branch circuit 48 and 49 is connected in series
with a 120 ohm
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resistor so as to provide the desired current flow, e.g., approximately 20 mA
through each LED
branch circuit 48 and 49.
However, those skilled in the art will appreciate that various different
circuit
configurations of the LEDs are suitable. For example, integrated time circuit
43 can operate at
least six LEDs in a given branch circuit, but by increasing the branch
resistor 47 or 48, the
number of LEDs in the branch circuit could be decreased down to only one LED.
It may also
be useful to utilize one or more self blinking LEDs to effect the blinking
cycle without requiring
a timer circuit. Thus, for example, all of the LEDs may alternatively be
configured in a single
serial chain or, alternatively, each of the LEDs may be placed in parallel
with one another.
Resistors 40 and 41 define the duty cycle and on time of the LEDs 45a-45h.
According
to one preferred embodiment of the present invention, resistor 41 comprises a
386K resistor and
resistor 40 comprises a 118K resistor. These resistance values for resistors
40 and 41 define a
duty cycle of approximately 20 percent with an on time of approximately 0.25
second. Of
course, varying the values of resistors 40 and 41 facilitates changes in the
duty cycle and on time
such that various different combinations thereof may be obtained. as desired.
Indeed. variable
resistors, such as the Bourns 3386 3/8-inch square metal cermet resistor may
alternatively be
used in place of resistors 40 and 41 so as to facilitate convenient manual
changing of the duty
cycle and on time.
In order to provide a SO percent duty cycle per the Manual of Uniform Traffic
Devices,
or MLJTCD guideline published by the United States Federal Highway Commission
for red
blinking lights on a stop sign located at a remote intersection, and to
provide an on time of
approximately one second, the resistances of resistors 41 and 40 should be
approximately 60K
and 600K, respectively.
It is important that resistor 41 have a resistance of at least IOK, in order
to prevent
undesirable damage to integrated circuit timer 43.
Resistor 40 and capacitor 37 cooperate to determine the on time of the LEDs
45a-45h.
The series combination of resistors 40 and 41 with the capacitor 37 determines
the off time of
the LEDs 45a-45h. The blinking cycle time is the sum of the on and off times.
The capacitor
38 prevents parasitic oscillation of the integrated circuit timer 43.
According to one preferred embodiment of the present invention, the control
circuit is
configured so as to facilitate compliance with the MLJTCD guideline which
specifies that the
preferred blink cycle for red blinking lights mounted on stop signs at remote
intersections as one
second on and one second off, equivalent to a 50 percent duty cycle and an on
time of one
second.
The solar panel output voltage is used to turn the integrated circuit timer 43
on and off,
using the high-gain Darlington transistor pair 34 and 35 for the switching
function. These high-
gain transistors 34 and 35 ensure that there is no instability in the
electrical switching function,
so that the LED blinking cycle is either turned fully on or fully off. The use
of this Darlington
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1 pair 34 and 35. and aiming the solar panel such that it is pointed
substantially directed upward.
tends to mitigate any tendency for vehicle headlights to cause the blinking
timer circuit to be
undesirably disabled at night such that the LEDs 45a-45h fail to blink as a
result of automobile
headlights. This arrangement provides a substantial advantage in that no
separate photocell or
photodetector is needed to provide an ambient light-sensing function, since
this function is
provided by the solar panel itself according to the present invention.
Zener diode 32, in cooperation with resistor 31, determines the output voltage
of solar
panel 20 which causes the blinking cycle of the LEDs 45a-45h to cease.
Mercury tilt switch 56 and fuse 57 cooperate to provide a simple and effective
means of
disabling the control circuit, so as to prevent further functioning of the
LEDs 45a-45h in the
event of theft or vandalism. Preferably, the mercury tilt switch 45 is
configured such that tilting
of more than approximately 30 degrees from the vertical results in closing
thereof. Closing of
the mercury tilt switch 56 effects a direct short across the terminals of
battery 21, thereby causing
fuse 57 to blow. Further operation of the LEDs 45a-45h will not occur until
the fuse 57 is
replaced.
Referring now to FIGs. 3 and 4, mounting of the LED drive circuitry and the
battery
charging circuitry, according to the present invention, is shown. The battery,
solar panel, and
control circuitry is preferably mounted upon the back of the stop sign as
shown in FIGs. 3 and
4.
Discussion and illustration of the present invention as a stop sign is by way
of example
only and not by way of limitation. Those skilled in the art will appreciate
the various other
embodiments or implementations of the present invention are likewise suitable.
Each of the LEDs 45a-45h are also preferably mounted to the back of the stop
sign and
preferably extend therethrough. The LEDs 45a-45h are mounted about the
periphery of the stop
sign 46. It is prefer ed that eight LEDs 45a-45h are mounted, one at each of
the eight vertices
of the stop sign. The stop sign 46 is attached. via threaded fasteners 50 such
as bolts, screws, or
. any other desired fasteners to pole 51. The LED drive circuitry,
rechargeable battery, and battery
charging circuitry of FIG. 2 is preferably contained within housing 52, which
is attached to the
sign 46 via brackets 53. The solar panel 20 is also attached to the stop sign
46 via brackets 53.
It should be noted that solar panel 20 can also be mounted remotely, for
example at the top of
extended mounting pole 51, in which case the rechargeable batteries and
control circuits can be
contained in a small business 52. The housing 52 is preferably not more than
3/4-inch thick
when mounted on the back surface of sign 46.
With particular reference to FIG. 4, the LEDs have a radiation pattern having
an angle,
Angle A (better shown in FIG. 5), less than approximately 20 degrees,
preferably less than
approximately 10 degrees. Indeed, as discussed above, the LEDs may have a
radiation pattern
angle less than approximately 4 degrees.
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1 Referring now to FIG. S, each LED provides illumination with a radiation
pattern having
an angle, Angle A, as discussed above. Each LED 45a-45h has a pair of leads 62
and 63 for
providing electrical power thereto. According to the present invention, the
leads 62 and 63 are
at least 3/8 of an inch long, so as to mitigate damage to the LEDs 45a-45h,
which may otherwise
occur during assembly of the present invention, when the LEDs are soldered in
place.
Referring now to FIG. 6, the LED housing comprises upper housing section 60
and lower
housing section 64, within which a portion of each LED 45a-45h and the LED
mount plate 61,
as well as the LED drive circuitry 65 of FIG. 2 are disposed. Ribbon cables 66
and 67 provide
electrical interconnection between LED drive circuitry 65 and other LEDs which
are similarly
contained within water-resistant housings. Thus, only one water-resistant
housing, such as that
shown FIG. 6, needs to contain the LED drive circuitry 65 while the other
water-resistant
housings merely contain the remaining LEDs and provide electrical connection
thereto.
Alternatively, LED drive circuitry 65 and rechargeable battery, preferably
NiMH type, can be
contained in a separate enclosure mounted to the back of stop sign 46. It is
preferred that all
components extend not more than 0.75 inches from back surface of stop sign 46,
except fro the
solar panel. Electrical connection between ribbon cable 66 and 67 and LEDs 45a-
45h is
preferably effectuated using insulation displacement connector, or IDC,
connector 74.
Trays 68 and 69 preferably cover ribbon cables 66 and 67, so as to provide
protection
therefor. Cable trays 68 and 69 are sufficiently rigid to provide protection
to the ribbon cables
67 and 69 enclosed therein. Ribbon cables 66 and 67 preferably contain eight
conductors
typically 28 AWG stranded type, enclosed by insulation on 0.050 inch centers.
Use of the water-resistant enclosure defined by upper section 60 and lower
section 64 and
the cable trays 68 and 69 substantially reduce the likelihood of undesirable
damage during
shipping and handling, as well as reduce the likelihood of damage from
vandalism or from
intrusion of water into the electrical parts.
Ribbon cables 66 and 67 thus provide for the independent connection of up to
four LEDs
each to the control circuit, such that each such LED may be independently
controlled by the
control circuit and independently tested thereby. Those skilled in the art
will appreciate that the
control circuit and cables 66 and 67 may be configured to accommodate any
desired number of
LEDs.
Optionally, some or all of the ribbon cables 66 and 67 and the cable trays 68
and 69 are
secured to the back of the stop sign 46 via VHB tape sold by the 3M Company or
any other
desired bonding or affixing material.
Pin selectors 57 and 58 define the desired sequential connections between the
eight
conductor ribbon cables 69 and 67, respectively, and may optionally provide
connection between
LED leads 62 and 63 of FIG. S and the desired positive or negative conductor
in each ribbon
cable 69 and 67. Each of the pin trees associated with the pin selectors ~7
and 58 has four
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possible positions. thereby providing optional connections to all eight
conductors in the
preferred embodiment of the present invention.
Attachment of the lower section 64 to the upper housing section 60 preferably
et~ects
substantially deforming of the ribbon cables 67 and 69 such that they are
caused to compress
S and bend around forms 73 which function as a cable restraint and thereby
prevent damage to the
LED drive circuitry 65 in the event that one of the ribbon cables 67 or 69 is
inadvertently pulled
or displaced. Compression of the ribbon cables 67 and 69 intermediate the
upper housing section
60 and the outer O-ring seal 71 contained in groove 75 within lower housing
section 64 inhibits
the undesirable introduction of water into the housing.
A plurality of threaded fasteners, such as screws 70 attach the lower housing
section 64
to the upper housing section 60 and may also attach the assembled upper and
lower housing
section 60 and 64 to the rear of the stop sign 46. Alternatively, the
assembled housing may be
attached to the stop sign 46 via any other desired means, e.g., adhesive
bonding, press fit, other
fasteners, etc. Outer O-ring seal 71 provides a water-resistant seal between
the upper housing
60 and the lower housing section 64 as upper housing 60 and lower housing 64
are compressed
together by fasteners 70. Similarly, LED O-ring seal 72 provides a water-
resistant seal between
LEDs 45a-45h and the upper housing section 60. where the LED 45a-45h extends
through the
upper housing section 60, so as to be visible from the front of the stop sign
46.
Thus, according to the preferred embodiment of the present invention, the LEDs
45a-45h
are each mounted in a small, waterproof enclosure so as to enable any one of
several LEDs
mounted on a traffic sign to be inspected, removed or replaced as may be
desired from time-to-
time without disturbing any of the remaining LEDs 45a-45h. Replacement of LEDs
45a-45h
may be accomplished by detaching IDC connector 74 from ribbon cables 66 and 67
and then re-
attaching another IDC connector 74 with new LED mount plate 61 to ribbon
cables 66 and 67.
According to the preferred embodiment of the present invention, the LEDs are
thus
mounted in a waterproof enclosure such that the output light beam therefrom is
aimed
approximately perpendicular to the flat surface defined by the stop sign 46.
Alternatively, the
enclosure defined by the upper enclosure section 60 and lower enclosure
section 64 is mounted
directly to a generally planar surface and the generally planar surface is
then mounted to the stop
sign.
Refernng now to FIG. 7, according to an alternative configuration, the present
invention
comprises a main control circuit 75 to which a plurality of other circuits may
be electrically
connected. The main control circuit 75 comprises the integrated circuit timer
43 of FIG. 2 and
defines the control circuitry for the LEDs 45a-45h. Batteries 76 and 77 are
electrically
connectable to the main control circuit 75, so as to provide power for the
LEDs 45a-45h.
Alternatively, any desired external electrical power source 78 may be
utilized, such as a solar
panel or other low voltage DC power source.
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Preferably, the LEDs comprise two banks 48 and 49, each having LEDs connected
in
series and the banks are connected in parallel as shown in FIG. 2.
Optionally, a test system 79, discussed in detail below, may be electrically
connected to
the main control circuit 75 in order to effect testing of the LEDs 45a-45h,
batteries 76 and 77,
the power source 78, as well as any desired control circuitry.
Auxiliary power output board 80 provide output power to other devices, as
desired.
Override control card 81 facilitates control of the LEDs 45a-45h via any
desired source
other than the internal LED control circuitry of FIG. 2. Thus, for example,
the LEDs may be
controlled by external environmental sensors, such as an ice or freeze sensor
or remotely from
an emergency vehicle, as discussed in detail below.
Blink selection option 82 facilitates changing of the duty cycle and/or on
time.
Other future auxiliary circuits interface 83 facilitates the electrical
connection of a variety
of other optional features, as discussed in detail below.
Time-of day memory time cycle 85 comprises an ambient light sensor and a timer
such
that illumination of the LEDs 45a-45h may be controlled with respect to a dusk-
to-dawn cycle.
For example, the LEDs may be preprogrammed so as to begin illuminating one
hour prior to
dusk and to cease illuminating one hour after dawn. In this manner,
illumination of the LEDs is
dependent upon the times of sunrise and sunset, but frequent reprogramming due
to variations
in these times is not necessary.
Theft transponder 86 provides a signal, which may be detected by a local
police
department, in the instance that the illuminated stop sign of the present
invention is moved, e.g.,
stolen. The signal is preferably provided via a wireless or radio frequency
link. However, any
other suitable signal, such as an audible alarm signal, may similarly be
utilized.
Colored and mufti-colored LEDs 87 may optionally be used to facilitate
communication
of more complex messages or to enhance the capability of the present invention
to attract
attention.
Ice or freeze warning 88 provides an autoblink or increased blink rate when a
temperature
sensor senses a temperature drop below a predetermined threshold, such that
ice is likely to form
upon the roadway so as to present a hazard to nearby motorists. The increased
blink rate will
draw enhanced attention to the stop sign.
Vehicle headlight activation minimum battery 90 comprises an optional circuit
for sensing
the presence of an approaching vehicle, such as a photosensor (for sensing
headlights), a radar
sensor, an ultrasonic sensor, or any other desired sensor. The LEDs 45a-45h
are only activated
when an approaching vehicle is sensed, to conserve battery power.
Multiple signs trigger circuits and sequence logics 91 provides control
circuitry so as to
facilitate illumination of LEDs upon a plurality of different signs in any
desired manner. For
example, a dangerous curve in the roadway may be indicated by a blinking
sequence of arrows
formed upon a sign.
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Mufti-intersection or complex intersection controls 92 provide control
circuitry so as to
cause a plurality of separate traffic control signals to cooperate with one
another such that traffic
at a plurality of different intersections or from a plurality of different
signs at a single
intersection regulate traffic in a desired manner.
S Real time clock on/off controller 93 facilitates illumination of the LEDs
45a-45h
according to a predetermined schedule which does not depend upon the presence
or absence of
ambient lighting. Thus, for example, the LEDs may be pre-programmed so as to
initiate
illumination at 7:00 p.m. each evening and so as to cease illumination at 7:00
a.m. each morning.
Referring now to FIG. 8, an electrical schematic for implementing features
shown in the
I 0 block diagram of FIG. 7 is provided. As in the electrical schematic of
FIG. 2. integrated circuit
timer 101 provides an output for driving LEDs according to a desired duty
cycle and on time.
Preferably, two branch circuits of LEDs, via LED string 1 connector 110 and
LED string 2
connector I 11, are utilized.
Resistors 155 and 156 in FIG. 9 which are connected via connector 1 of
override
15 connector I 14 facilitate the definition of a desired duty cycle and on
time for the LEDs. Also.
transistors 103, 104 and 1 OS cooperate so as to facilitate operation of the
integrated circuit timer
101 without undesirable oscillation. Resistor 123 and zener diode 124 in
cooperation with
transistor 105 and interrupt switch 151 in FIG. 9 are connected by connector 2
in override
connector 114 to facilitate operation of the LEDs only during a period of low
illumination, as
20 discussed in detail above.
One important aspect of the electrical schematic of FIG. 8 is the use of plug-
in connectors
110, 1 I I, 113, 114, 115 and 116. These plug-in connectors I 10, 111, 113,
114, 115 and 116
facilitate the use of a common control circuit for a variety of different LED
traffic sign
applications.
25 Thus, according to the present invention, the 8-conductor auxiliary
override connector 114
may be utilized to control the duty cycle and on time via connections I
thereof: to force the LED
blink cycle to commence upon demand via connection 2 thereof; and to provide
power from a
remote DC power supply, such as a solar panel via connector 3 thereof.
Connector 1 I S facilitates the connection of a first battery thereto via the
plus and minus
30 terminals thereof and the connection of a thermistor via the other two
terminals thereof.
Similarly, connector 116 facilitates the use of a second battery and
thermistor, if desired. LED
string number I connector 110 facilitates the attachment of an 8-conductor LED
ribbon
connector which may facilitate electrical connection to from one to four
individual LEDs. The
current in each LED string is preferably adjusted to 20 mA via balancing
resistors 117 and 118
35 which are preferably mounted so as to facilitate easy changing thereof.
The 16-conductor test console connector 113 facilitates both operational and
maintenance
testing as described in further detail below.
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Removal jumpers or pin selectors 121 and 122 facilitate further control of the
LEDs.
When removal pin selector 121 is removed. then the main control circuit is
completely disabled
and the LEDs will not illuminate. When removable pin selector 122 is removed,
then the LED
blinking cycle is forced to turn on.
As mentioned above, electrical power may optionally be provided via a solar
panel or
other external power source by electrical connection to connection 3 of
override connector 114.
When sufficient ambient light is available, then the solar panel input
voltage, which is provided
through resistor 123 is sufficient to cause zener diode 124 to conduct,
thereby causing transistor
105 to shunt voltage away from Darlington transistors 103 and 104. When
voltage is shunted
away from Darlington transistors 103 and 104, then insufficient voltage is
provided to the IC
timer 101 to maintain triggering of the LED blink cycle and the LED blink
cycle therefore
ceases. Thus, at night, in darkness or in adverse weather conditions zener
diode 124 overcomes
the reduced solar panel output voltage and transistor 105 no longer shunts
voltage away from the
Darlington transistors 103 and 104, thus facilitating triggering of the LED
blink cycle via
I S integrated circuit timer 1 O 1. Removing pin selector 122 has a similar
effect by interrupting the
function of transistor 105 so as to shunt voltage away from the Darlington
transistors 103 and
104.
Transistors 120 and 125 in combination with resistors 126-131 provide the same
battery
charging and regulating functions as the corresponding components shown in
FIG. 2. However,
since the electrical schematic of FIG. 8 contemplates the optional use of two
batteries (attached
via electrical connectors 115 and 116) and since the associated regulating
thermistors are not
located on the main control board, but rather are preferably located inside
the battery packs
themselves, provision is made for the interconnection of the batteries and the
thermistors via
electrical connectors 115 and I 16.
Referring now to FiG. 9, a preferred embodiment of the auxiliary override
circuit is
provided. Connector 159 is electrically attached to override connector 114 in
FIG. 8. Resistor
I55 and resistor 156, which are preferably both mounted so as to be easily
replaceable, are
optionally used to adjust the LED on time and duty cycle, respectively. As
those skilled in the
art will appreciate, the use of several banks of such resistors, combined with
overnde
transponder relays on the auxiliary overnde circuit would allow override of
the LED blink cycle
so as to facilitate the use of an increased blink rate, e.g., two or three
times that of the normal
blink rate, in order to alert motorists to emergency conditions.
Jumper assembly or pin selector 157 may be removed from the pin tree so as to
force the
LED blinking cycle to commence. A number of different methods for remotely
activating a relay
on the auxiliary override circuit so as to force the LEDs to start blinking or
to blink at different
rates using a relay device to optionally select from a number of pairs of
resistors I 55 and 156 are
contemplated, as mentioned above and discussed in detail below.
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1 External electrical power is provided from a solar panel or other external
DC power
source via connections 3a and/or 3b of connector 158. Connection number 4 of
connector 158
facilitates the addition of an auxiliary power output connector so as to
facilitate the provision of
electrical power to any other desired device. Connection 2a is an auxiliary
connection to other
optional means for forcing the LED blink cycle to start. For example, it may
be desirable to
provide a radio frequency or other wireless means for initiating the blink
cycle, so as to allow
emergency vehicles to control traffic. Further, external sensors, such as a
freeze or ice warning
sensor may attached so as to cause the LEDs to blink when the temperature
falls below a
predetermined threshold value.
Referring now to FIG. 10, a test system circuit is used to test the
independent functioning
of each individual LED 45a-45h {FIG. 2), the solar panel output, and the
batteries. Connections
I-16 are electrically connected to the test console connector 117 of FIG. 8
using suitable
connection means. Connections 7-11 corresponding to test switches 160-163 are
used to
individually test each LED in LED string 1 (48 of FIG. 2). Likewise,
connections 12-16,
corresponding to test switches I64-I67 are used to individually test each of
the LEDs in LED
string 2 (FIG. 2). The switches 160-167 may be operated manually,
automatically via
mechanical means, or may be computer or otherwise electronically controlled.
If any particular LED in one of the two LED strings fails, then all of the
rest of the LEDs
in that string will cease blinking. A common problem is to determine which of
the LEDs in a
string has failed, so as to facilitate only replacement of the failed LED. The
test system circuit
of the present invention shown in FIG. 10 facilitates such individual testing
of the LEDs. In
order to facilitate such individual testing of the LEDs, the 3-position
maintenance switch 168 is
used. The three positions correspond to (a) always blink, (b) normal operation
and (c)
disconnect. The 3-position maintenance switch 168 is moved to "always blink"
to force the LED
blinking cycle to start. Then. if there is a failed LED, the failed LED string
may be observed.
When the test switch 160-167 for a particular LED is closed. then that LED is
bypassed.
If the bypassed LED is the failed LED, then the rest of the LEDs on the failed
LED string will
commence blinking. If the LED corresponding to the closed switch is not the
failed LED, then
none of the LEDs on that particular LED string will blink. Thus, if there are
no failed LEDs on
either LED string, then only that particular LED being tested will stop
blinking when the
associate LED test switch 160-167 is closed.
,:
By selecting each of the LED test switches 160-167 in sequence, it is thus a
simple matter
to find any failed LED when all of the rest of the LEDs on that particular LED
string resume
blinking. If there is more than one failed LED, then the test switch for each
failed LED must be
used before the remaining LEDs will begin blinking again. If there are no
failed LEDs, then
circuit continuity and integrity can easily be verified by turning off each of
the blinking LEDs
in sequence utilizing the LED test switches.
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1 Switch 168 and 169, taken together, preferably define a 3-position
maintenance test switch
wherein in a first position switch 168 is closed and switch 169 is open. In a
second position.
both 168 and 169 are open and in a third position. 168 is open and 169 is
closed. In the first
position (168 closed and 169 open), the LEDs 4~a-45h blink continuously. In
the second
position, (both 168 and 169 open), the control circuit operates normally,
i.e., the LEDs illuminate
when ambient light falls below a predetermined threshold value and the LEDs
blink with a duty
cycle and on time as defined by the integrated circuit timer 43 and associated
circuitry. When
the test maintenance switch is in the third position (switch 168 is open and
switch 169 is closed),
then the control circuit is disabled and all batteries and external power
supplies are disconnected
therefrom.
According to the preferred embodiment of the present invention, the test
system circuit
is mounted in a hand-held test console which can be manually plugged into the
test console
connector 113 of the main control circuit board of FIG. 8 using a 16-pin
connector. For example,
a 16-conductor ribbon cable, typically approximately six feet long, may be
utilized to effect such
electrical interconnection. After plugging the 16-pin connector into the main
control circuit
board, a technician may then stand in front of the enhanced visibility traffic
signal of the present
invention and effect desired testing thereof. Thus, the LEDs, solar panel
and/or batteries may
be tested as described above.
Switch 172 facilitates the testing of the battery for proper voltage. Switch
173 facilitates
the testing of the solar panel for proper output during normal daylight
conditions or, an external
low voltage DC power source can be tested. Thus, the test circuit of FIG. 10
allows a test
technician to rapidly and efficiently perform all tests necessary to verify
proper operation and/or
identify maintenance requirements for one or more enhanced visibility traffic
signals of the
present invention.
Referring now to FIGs. 11-13, the present invention optionally comprises a
fail-safe stop
sign 140 configured so as to actuate or provide a traffic indication in the
event of power loss or
other emergency condition. Thus, for example, this optional configuration of
the present
invention comprises a stop sign
Thus, a sign, such as stop sign 140, is configured so as to be displayed in
the event of loss
of power. Thus, for example, for such stop signs 140 may be provided at a 4-
way intersection
such that in the event of loss of power and the consequent non-functioning of
the traffic lights,
each of the stop signs is displayed, so as to define a 4-way stop, or
alternatively, for example,
a required stop on side streets to a main highway. In this manner, the
likelihood of traffic
accidents is mitigated desirably.
Although a deployable stop sign is discussed and illustrated herein, those
skilled in the
art will appreciate that various other deployable signs are likewise
desirable. Thus, the use of
a deployable stop sign is by way of example only and not by way of limitation.
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Thus, according to this aspect of the present invention, a current detector
monitors current
provided to the traffic signal light, which should always be present since one
of the three, i.e.,
red, yellow or green, lights should always be illuminated at any given
instant. Thus, when no
current is present, as may be easily detected on the common or return line
from the signal lights.
then it is reasonable to assume that a power failure has occurred and that the
definition of a 4-
way stop via the deployable stop signs is appropriate.
With particular reference to FIG. 1 l, the deployable stop sign 140 is
disposed upon a pole
141, which is preferably the same pole that traffic signal light 142 is
disposed upon. Those
skilled in the art will appreciate that the deployable stop sign 140 of the
present invention may
similarly be mounted to any other structure.
With particular reference to FIG. 13, the deployable stop sign 140 comprises
upper stop
sign section 143 which is rigidly attached to the pole 141 and lower stop sign
section 144 which
is pivotally attached, via hinge 145, to upper stop sign section 143. Hinge
145 preferably
contains a hinge spring to open upon deployment.
1 S According to the preferred embodiment of this aspect of the present
invention, a detent
member comprises a bolt 146 attached to the lower stop sign section 144 via
nut 147 and washer
148. The bolt head 149 is captured by a release mechanism 1 S0, which is
contained within the
upper stop sign section 143. Alternatively, it is preferred that release
mechanism 150 is attached
to pole 141 using the same mounting bracket which is used to mount upper stop
sign section 143.
Release actuator 151, preferably comprising a 12-volt DC solenoid or actuator
is coupled
to effect holding of the detent defined by the head 149 of bolt 146 as long as
power is applied
to the solenoid or actuator 151. When power is provided to solenoid or
actuator 151, then the
resulting movement causes linkage 152 to effect release of the detent defined
by the head 149
of bolt 146 by the release mechanism 150.
Thus, when a power failure occurs, then the solenoid or actuator activates so
as to cause
release mechanism 150 to allow gravity to move the lower stop sign section 144
to the deployed
position thereof, such that the stop sign can be observed by oncoming
motorists. Since there is
no external electrical power available during a power outage, the electrical
power needed to
release and deploy a power outage, the electrical power needed to release and
deploy the stop
sign is provided to solenoid or actuator 151 by the rechargeable battery.
Since this is a 12-volt
DC battery, the release mechanism is preferably a conventional automotive
trunk release
mechanism.
Optionally, a spring preferably located in hinge 145 may be utilized to assist
movement
of the lower stop sign section from the stowed position (FIGS. 11 and 13) to
the deployed
position (FIG. 12) thereof. A spring may similarly be utilized to cause the
lower stop sign
section to move from the stowed position to the deployed position thereof when
the stop sign is
positioned or configured such that gravity will not effect such movement.
Thus, a stop sign or
any other desired sign may be mounted in various different positions and still
be caused to move
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from a stowed to a deployed position upon activation of a release mechanism,
such as may be
effected by a loss of power.
A toroidal current transformer 175 or the like may be installed such that the
hot or power
wires for each of the red, yellow and green traffic signal lights pass
therethrough or such that a
common or return line passes therethrough, so as to provide an indication of
the presence of
current to the traffic signal. Deployment of the deployable traffic sign 140
is preferably delayed
by at least 2 to 10 seconds after current loss is sensed, so that it does not
deploy in the event of
a short duration power fluctuation.
As shown in FIG. 11, the solar panel 20 is preferably mounted atop the pole
141.
Alternatively, the solar panel 20 may be mounted at any other convenient
location, such as at
some point upon the pole intermediate the deployable stop sign 140 and the top
of the pole or
upon the deployable stop sign 140 itself.
When the solenoid or actuator 151 deactivates so as to effect deployment of
the
deployable stop sign 140, the LED blinking cycle for the LEDs 45a-45h also
starts. Preferably,
the LEDs 45a-45h continue to blink until the restoration of electrical power
has been detected.
Optionally, the LEDs 45a-45h may be controlled so as to blink only at night or
in near
darkness or adverse weather conditions, or may be pre-programmed to blink
according to a
predetermined schedule according to either a real time or dusk/dawn timer.
After power has been restored, then a maintenance technician can restore the
deployable
stop sign 142 its stowed position. Preferably, a latch holds the lower sign
section 144 in the
deployed position thereof. Thus, the maintenance technician may be required to
unlatch the
lower sign section 144 so as to effect its return to the stowed position
thereof.
The outside surface of the stowed deployable stop sign 140 may optionally be
used as a
sign, a community identification emblem or as any other desired type of
conventional sign.
According to another preferred embodiment of the present invention, a
lightweight,
portable LED illuminated traffic sign system with a sign-mounted rechargeable
battery
preferably allowing at least fifty hours of LED operation at a 50 percent duty
cycle is further
described herein. Such a portable traffic sign is widely acceptable for a
variety of different
applications including emergency or police uses, for example, at traffic
accident sites,
checkpoints, construction projects, traffic signal outages, etc.
Such a portable preferred embodiment of the present invention preferably
comprises an
18-inch stop sign constructed from 16-gauge sheet metal and weighing
approximately two
pounds. Eight LEDs having water-resistant housing similar to those shown in
FIG. 6 are
preferably powered by a single 1600 milliamp-hour rechargeable nickel metal
hydride (NiMH)
battery and a main control circuit which add only approximately two pounds to
the weight of the
stop sign. A wire frame mounting stand, preferably using 1 /4-inch diameter
wire including
attachment points to the 18-inch stop sign add approximately another four
pounds. The total
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1 weight of such an 18-inch portable LED illuminated stop sign is
approximately only eight
pounds.
Such a completely portable LED illuminated stop sign with a 1600 milliamp-hour
battery
is thus designed to operate for at least fifty hours at SO percent duty cycle
with eight LEDs, each
blinking with at least 6,000 millicandella of output light. The 1600 milliamp-
hour NiMH battery
may be recharged using a polarized 2-wire plug from any vehicle 12-volt DC
electrical system
or from a 120-volt AC power source using an appropriate charger.
For example, the present invention may be configured so as to indicate the
presence of
a dangerous curve using a number of LED defined arrows or chevrons which may
be controlled
so as to operate in a desired sequence which clearly indicates the direction
of an upcoming turn
in the roadway ahead.
According to one preferred embodiment of the present invention, remote control
activation of the LEDs by emergency vehicles such as police cars, ambulances,
fire trucks,
military vehicles or an intelligent traffic system (ITS) is facilitated. Thus,
the so-called
1 ~ ''firehouse pre-empt" is an override transponder operated by radio or ITS
control which is
presently used in some cities to remotely control tragic signal lights so as
to facilitate safer and
faster response by firefighting vehicles. Other types of remote control
transponders could be
used to either selectively start, or double or triple the LED blinking rate on
individual LED-
activated traffic signs to thereby allow police or other emergency vehicles to
provide enhanced
awareness of emergency conditions by remote control. Still another type of
remote control from
police vehicle transponder or ITS control could effectuate deployment and
onset of LED blinking
cycles in traffic signs which are normally mounted in a stowed and non-
blinking condition.
The present invention may further comprise hand-held stop paddles for use by
crossing
guards, which are actuated using a manual switch mounted in the stop paddle
and which can be
recharged using a suitable charging device.
The enhanced visibility traffic signal of the present invention may be
constructed by either
retrofitting an existing traffic signal such as a stop sign or by custom
manufacturing new traffic
signals.
According to an alternative preferred embodiment of the present invention, one
or more
photodetectors or radar detectors is aimed toward oncoming motor vehicle
traffic, so as to detect
the approach of a motor vehicle at night or in overcast weather conditions.
The blink cycle time
may be increased to provide additional visibility during the approach of a
motor vehicle and then
reset to a normal, e.g., lower, rate after the motor vehicle has passed by.
It is understood that the exemplary traffic control signs described herein and
shown in the
drawings represent only presently preferred embodiments of the invention.
Various
modifications and additions may be made to such embodiments without departing
from the spirit
and scope of the invention.
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