1. Introduction
LED lighting for billboards offers significant maintenance savings as compared to conventional high intensity lights. When properly controlled, LED lighting has a much greater service life than conventional lamps, and LED lighting does not have the intensity degradation of conventional lamps which may lose about 30% intensity in the first 3 months of operation. Conventional lamps are typically replaced after approximately 6 months of service.
Despite the maintenance advantages, prior art LED devices have not been successful in providing high efficiency solutions which provide compelling economic motivation to replace conventional lighting.
There is a need for higher efficiency LED billboard lighting systems.
2. Prior Art Devices
A common example of prior art lighting for a large 14′ by 48′ billboard is the use of four metal halide lamp fixtures as shown in
Another prior art device is the Halophane™ fixture. Its distributor reports that two 400 watt lamps may be used to light a billboard.
The Adtech™ Ecotech™ series LED lights reportedly use a total of 624 watts per billboard side.
One aspect of the current invention is the ability to provide effective billboard lighting with approximately 200 total watts per side.
The current invention provides dramatically higher efficiency than prior art devices. This higher efficiency is achieved with less complex devices than prior art LED billboard lighting products, so that the current invention can be sold at prices that approach conventional lighting products. The ability to provide substantially improved energy efficiency, low cost, and long-life LED devices also facilitates the use of solar, wind, or other low energy density power for the devices.
The current invention includes the methods of retrofitting existing billboards; providing lighting for new billboards; installing and orienting LED lighting devices; communicating with LED lighting controllers; controlling LED devices.
The current invention includes methods for designing and fabricating LED lighting devices, such as for billboards.
The current invention includes LED lighting devices, such as for billboards.
Some aspects of the design methods include
List of Elements
The following list of elements is provided for convenience.
Many players in the LED lighting scene propose and sell Light Bulb, Fluorescent Tube and High Pressure Sodium Fitting Replacements. One embodiment of the current invention is the replacement of the whole fitting as the only way to efficiently disperse the heat generated by the LED lighting arrangement in such a way that the junction temperature remains in the sweet spot during prolonged operation.
The most common billboard lighting arrangement is a 480 Watt High Pressure Sodium Lamp and a special mirror arrangement designed to provide relatively even coverage of the billboard. The efficiency of a HPS arrangement is approximately 56 lumens per watt when the bulb is new and the spectrum often expressed in temperature is around 5500K (bright white). There is always a bright spot in the center as the glass shape of the lamp builds a focusing lens that produces a hot and bright spot in the center of the field the mirror is aimed at.
Instead of making bulb replacements for billboard lighting, this embodiment is for the making of a replacement fixture. This way light output limitations of an LED light can be compensated for by providing an ideal operating environment as described in copending patent applications by applicant (U.S. Patent Application Nos. 61/115,739; 61/115,775; 61/115,790; and 61/149,076 which are incorporate by reference to this specification) and optimal light distribution as well as diffusion to eliminate user aversion against too bright light sources.
One aspect of the current invention is to facilitate fast rollout of more efficient lighting technology, where more efficient is defined as the combination of;
In this embodiment, the whole billboard lighting fixture is replaced. This way the electrician can disconnect the old fitting and re-connect the new fitting. By contrast, in bulb or tube replacement technology, where the ballast has to be removed or at least disabled, fittings must be re-wired and/or receptacles replaced, tube or bulb replacements have to be installed. The following downsides continue to exist with bulb and tube replacement-inadequate cooling and the resulting low energy efficiency; and the need to clean diffusers.
In this example, one side of a billboard is illuminated with a first side lighting system comprising four lighting modules 100. The second side of the billboard may be illuminated with a second side lighting system also comprising four lighting modules.
Example Construction of Lighting Module 100 for LED Billboard Replacement Fitting
In this example, a high efficiency LED billboard lighting system with four LED modules replaces existing lighting modules. Each lighting module has six heat sink assemblies arranged in two rows. The heat sink assemblies comprise an LED package mounted on a heat sink reflector.
Housing and Reflector Design—Heat Sink Assemblies
In this embodiment, the general construction is an aluminum or copper, welded, extruded or formed frame housing 120 with either a separate or attached reflector holding plate 130 that acts also as the base to hold the seals, diffuser 260 and reflector 150 in place.
The construction allows for fast assembly and rigid construction, shipping of two units in one container can be achieved without breaking a glass diffuser.
In one example, the reflector is made from either “Formed”, “Cut and Bent”, “Extruded” or “Cast Aluminum” 3000 or 6000 series for best heat transfer or any other method of producing a suitable shape.
The reflector may also be made from formed copper that has been coated with a highly reflective material such as chrome or high-bright nickel or stuck on glass or plastic mirrors.
Extension Plate
In this embodiment, a reflector extension plate 152 can be attached to the main reflector in order to extend the reflection area.
In this example, the extension plate extends to both sides of the main reflector. The ends of the extensions may be bent, such as at a 45 degree angle, in order to eliminate light overspill from the sides of the billboard.
Alignment Feature
The housing may include reference marks that permit an easy field alignment of the device as described in the installation section below.
LED Package
In this embodiment, the LED packages include a diode and a first refraction element.
In this embodiment, the LEDs are Citizen Electronics Group co., LTD. CL-L102 series LEDs with a 120 degree viewing angle. Each module has tow rows of 3 LEDs for a total of 5 LEDs per module. For 14 foot high billboards, 8 watt LEDs are used; for 10 foot high billboards, 7 watt LEDs are used; and for 8 foot high billboards, 6 watt LEDs are used.
The LEDs provide 140 lumens/watt By contrast, prior art LED lighting may use 40 lumens per watt, or approximately 170 watts for a light module versus about 50 watts for a module of the current invention
The LEDs are typically selected or designed considering light output per watt and light output per cost.
Refraction Elements
The 6 LEDs per module represents a total of 24 LEDs for the four modules of a 48 foot wide billboard. By contrast, a prior art LED device provides a total of about 1200 LEDs for a 48 foot wide billboard.
The first refraction element is a diffuser clamp 250, such as 3/16 inch Industrex™ glass with an upward-facing fine scattering pattern 252. This diffuser clamp serves several functions including clamping the LED in good thermal contact with the housing for thermal management; lessening the “harshness” of the LED light source; reflecting or blocking yellow light which is transmitted out the sides of the LED; and providing a top-side heat sink for the LED. In this example, the diffuser clamp extends past the LED in order to block the yellow light from the sides of the LED.
The second refraction element is a diffusing lens 260, such as 3/16 inch Industrex™ glass that may have a downward-facing fine scattering pattern 262. Orienting this diffusing lens with the fine scattering pattern facing downward reduces the accumulation of dust on the top of the lens. One function of this lens is to reduce the LED harshness.
Relatively thin refraction elements may be used in order to reduce reflection.
Controller
In this embodiment, a custom controller is used.
The controller can determine approximate dawn to dusk timing without a calendar. In one example, the controller records dusk and dawn for the 3 days prior to the current day, and turns on the LEDs at dusk; turns them off at midnight, and turns them on 2 hours before dawn. Other timing selections may be made.
The controller has a low voltage (48 volt) connector so that it can run on four 12-volt batteries. The controller has a power factor corrected, switch mode Power Supply, where the secondary side can be connected directly to a battery to monitor and charge the battery, and can run directly from the batteries. This design permits more efficient battery management for longer battery life.
In this embodiment, each module has a controller. One controller is configured to be a sensor and can inform (communicate with) the other controllers by wire or wirelessly.
New or replacement modules are provided to mount on billboards. Alignment marks on the module housing are aligned with strings from the top and bottom of the billboard to quickly establish proper spacing and orientation angle.
In one example, side panels are prepared with seal and alignment features. An outer heat sink is thermally connected to reflector base. An LED Power Supply is mounted to back of Reflector Base. A Reflector Base/Heat-Sink is provided with LED on Reflector held by Glass-Diffuser and sealed by “Silicon Adhesive Seal” installed. A frame is mounted to the Reflector base.
An LED controller may communicate by wire or wirelessly with other controllers. This permits a single controller to determine or receive an on/off control signal and communicate with the other controllers.
Some aspects of the design methods include
This application is related to U.S. Provisional Patent Application No. 61/225,629 filed by applicant on Jul. 15, 2009, and claims priority from that application.
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