Sign & Digital Graphics

October '17

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22 • October 2017 • S I G N & D I G I T A L G R A P H I C S ferent channel letters or cabinets. In constant voltage designs, a sign module with good design circuitry within the module converts the constant voltage to constant current at the LED level. It also includes current regulation circuitry in the module which, in turn yields consis- tent brightness from each of the modules operating on a power supply, regardless of the number of modules on that power supply. True constant current designs may be a bit more efficient, but there are sig- nificant limitations and restrictions on the quantity of modules one can oper- ate on a constant current power supply while maintaining consistent brightness between the groupings of modules in a cabinet or channel letter. Improved Sign Module Optics It is arguable that the most recent design features having the biggest recent impact on LED acceptance and perfor- mance in channel letters and cabinets has been related to optics. Early module designs had no optical beam shaping lens over the LEDs. The output of the LEDs was most commonly a 120° Lambertian distribution. Those designs still exist and still work well, particularly in large deep channel letters. However, when used in shallow channel letters or cabinets, the distribution of light often results in non- uniform luminance on the sign face. This effect can be minimized by using lower-lumen modules mounted closer together, but while that solution helps with luminance uniformity, it also increases material costs and installation labor. Many sign modules today are avail- able with wide-beam optics that spread the light in a "batwing" distribution pat- tern, named for the cross section shape of the light emanating from the module optics. Wide batwing optics allow for an improvement in luminance uniformity while keeping the LED modules spaced relatively far apart, particularly in shal- low depth letters or in cabinets. Most modules with optics spread the light in a 155° to 170° beam angle. Going beyond 170° is not as effective as too much light ends up hitting the inside walls of the letter or cabinet, never reach- ing the sign face. The most recent advances in optical design have improved light distribution even further. Optics have evolved and can now square off a beam pattern when viewed face-on. Due to their quadrant- symmetric light distribution, square lensed sign modules can be placed optimally to achieve uninterrupted illumination. In simple terms, it's much more effi- cient to mate together adjacent square pools of light than adjacent round pools of light to achieve uniform illu- minance. Square lens pattern designs have improved sign face uniformity even further in small/shallow cabinets and in channel letters ranging from six inches deep down to depths as thin as two inches or even shallower. Summary LED sign module technology, perfor- mance, and design has evolved over the years since they were first introduced. Improvements in installation design features, LED performance, materials, durability, and optics make LED sign modules more attractive and compelling than ever. SDG OSRAM's BoxLED Plus DS LED system offers tool-less mounting accessories. (Images courtesy of OSRAM) In Print... Online... ...in Person sdgmag.com sdgmag.com

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