Murphy's 4

LED Insights: LED Backlighting Strategies

J. Bryan Vincent is an expert in the field of solid state lighting and electronic materials. He has dedicated the past 10 years to developing LED solutions specific to the sign industry and is a partner at Principal LED. He has a bachelor’s degree in Chemistry and a Ph.D. in Chemistry/Materials Science.

LED backlighting is the light engine that powers the illuminated sign industry.

Looking Back

According to the American Sign Museum, the first backlit sign dates back to the 1840s with a gas-lit sign on the P.T. Barnum museum. Later came the incandescent light bulb—Edison filed his patent for a carbon-filament electric lamp in 1879, but commercialization had no traction until the turn of the century. By then a good number of merchants were using illuminated signage to draw the attention of consumers. In fact it was 1900 when the first electric sign company (Federal Electric Company in Chicago) was formed and began offering the first commercially available illuminated signs.

The electric sign industry was born.

At the time, however, most electric signs were not backlit but typically consisted of a porcelain enamel with the copy or message surrounded by Edison bulbs along the outer edge of the sign.

At the turn of the century, neon was developed, followed by the fluorescent lamp in the 1930s. However, it really was not until the development of plastics after World War II that backlit signage began to mature. Plastic-faced signs were easier to manufacture and required less skill to produce than hand-blown formed neon.

Much of the sign industry remained relatively unchanged for the next 50 years or so—until light emitting diodes (LEDs) became a viable illumination source about 15 to 20 years ago.

Choosing the Right System

Historically, backlighting was relegated to three primary forms of illumination: fluorescent lamps, metal halide or neon. With the wide variety of LED systems now available, sign makers have hundreds of choices to optimize signs of about any shape, size, or material. In fact, part of the problem is knowing which LED system to choose for a given sign application. In order to develop a strategy for choosing the appropriate LED backlighting, a sign maker needs to answer a few questions.

  • What type of sign is going to be built?
  • Where is the sign going to be used?
  • What kind of manufacturing and installation capability do I have available?

The answers to these three questions can help drive making a good decision and having a solid product strategy when choosing the right LED backlighting solution.

Knowing the type of sign, its size, depth, and the desired lighting effects are probably the most important things to know in determining the right LED system.

Channel letters are pretty easy. Most likely, you will want to choose a “string-based” LED system. These are tried and true, offer the maximum flexibility and are relatively easy to install. Most sign companies have a particular module or manufacturer that they prefer. Sign modules come in a variety of forms—with or without optics, different colors, a range of outputs, etc.

General Rules and Considerations

However, there are some general rules that can be used to make sure you are not buying and installing too much or too little of a system. Your decision, of course, will depend upon the sign type and desired face material. Here are some things to think about:

  • Compensate for a Vinyl Face—If the sign face includes perforated vinyl you may want to choose a brighter LED in order to compensate for the 50%+ light blockage as a result of the vinyl.
  • Beware of the Low-Cost Trap—Another consideration is cost. I have seen many sign makers take the approach where they just use the brightest, lowest-cost module they can find. Beware of this trap. For instance, if a 120 lumens-per-foot product (0.72W) system costs $2.50 per ft., and you can buy a 180 LM/ft. (1.2W) system for the same price, you may think – “Hey I am better off.” However, depending on the spacing, you may still need the same number of modules and now, instead of running 50 ft. per power supply, you can only run 30 ft. Now you will need two power supplies instead of one, adding another $0.50 per ft. to your total cost when that level of brightness is not really required. It also adds labor and other costs to install and mount and wire the extra power supplies.
  • Consider a Universal System—Sign makers say they want to have one single module that is versatile enough to use for most channel letter applications. This certainly can simplify manufacturing and stock levels, but the tradeoff is flexibility. Principal LED has tried to address this unmet need with its Fusion Freedom module. This module is universal in that it has the ability to choose the desired output based on wiring and has a removable batwing optic, as well as a range of colored lenses that can be attached or removed to provide specialty colors and color temperatures of white.

According to Jeff Brazin, vice-president of national accounts for Principal LED, “Our goal is to simplify the lives of our customers. Fusion Freedom allows sign makers to stock a single module that can be used in over 100 configurations with a simple lens change or based upon how the product is wired.”

Sign Cabinet Modules

What about larger backlit applications like sign cabinets? While modules can do the job, they typically are laboriously time consuming. In order to address this need a range of systems are available as fluorescent alternatives to illuminated sign boxes. In this instance, understanding the application and location of the sign is critical to your backlighting strategy.

For large outdoor illuminated signs, it is recommended to use a dedicated system. A number of manufacturers have systems available, including GE, SloanLED, US LED and many others. Many of the “new construction” systems are easy to assemble and install. For companies that are installation-based, many manufacturers offer LED systems that fit directly into T-12 sockets for sign retrofits and offer equal levels of illumination and even lighting on standard 12” centers.

This year, US LED successfully launched its breakthrough TDX product for backlighting either retrofits or new-build cabinets. TDX covers up to 24” of stroke with 370 lumens per module and can evenly light applications from 3” to 18” depths (for recommended module spacing, visit www.usled.com). This product fulfills their engineering team’s goal of developing a class-leading product, with cost, performance, reliability, and ease of installation as their primary objectives.

According to US LED president John Allgood, “We’ve never been more excited about a product in our signage lineup than TDX. Compare the total TDX option with any other backlighting cabinet solution and you’re going to love TDX—a lot!”

TDX is available pre-assembled on military grade aluminum extrusions in 4’ lengths and in tube lengths for single or double-face applications. With supplied length-to-length connectors there is no need to survey for retrofits. Everything is easily configured in the field. US LED's patented quick-connect wiring system also makes the TDX system even more versatile and reliable.

Bitro Group sells its Lattice2G dedicated cabinet system that is available in a single- or double-sided option. One advantage of this system is that is particularly easy to install in single-sided cabinets and it can be “rolled” out directly into the back of the sign, providing even illumination without the added labor of peeling and sticking modules.

While true LED cabinet lighting solutions are ramping up extremely well, we still see channel letter modules being used in very large signs by shops that have the misconception that the unit cost of string-based channel letter modules is cheaper than a dedicated cabinet sign solution. "Nothing could be further from reality once total costs such as labor and liability are factored in,” according to Fritz Meyne Jr., vice president of sales for Bitro Group.

“With the advent of the new L3G Batwing Optics, the grid lighting system with its preconfigured depth options allows for factory-consistent and repeatable performance every time. Additionally, the optics provide white face illumination with no hot spots as shallow as 1.75 inches,” Meyne adds.

Light Tapes

Light tapes are a new entrant into the sign market that can be a low cost alternative that is easy to install for indoor sign cabinets. GE Lighting recently released its Tetra LED Tape, a flexible product that can be cut every two inches and is available with clamp-on jumper connectors; and they can be used in both sign cabinets and channel letter applications.

Principal LED offers Qwik Tape, another flexible tape system that utilizes a patented micro-pop rivet system that eliminates the need for soldering end wires and between ends of two reels. Qwik Tape also comes in Prime (175 LM /ft.) and Prime HD (350 LM.ft) versions on long 164 ft. rolls, reducing scrap and the end of rolls.

Bitro Group makes a “Tracer” flexible LED tape that is die cut so that it can be easily shaped for circular cabinets, as well as low-profile channel letters. With the advent of smaller and smaller illuminated letters with shallower and shallower return depths, very specialized LEDs are needed to eliminate hot spots. Add to this the trend for illuminated returns and your choices for illumination are slim (pun intended). Bitro’s patented Tracer, as the name implies, traces the font offering direct face illumination with no hot spots. This product is designed for a very specific application into custom-shaped fonts. On the other hand, if simple linear flat straight runs is the need, then tape LED is a more affordable solution.

Side-Mounted Solutions

In some cases cabinet or light box illumination is desired without the need for a baffle. While stick-based products often do the job, a number of manufacturers—including Principal LED (Street Fighter POD), International Light Technologies (Light Edge Summit), and SloanLED (Poster Box series)—offer systems that can be mounted to the side (return) of the sign cabinet.

The modules use a focusing optic that narrows the bean angle parallel to the sign face, allowing even illumination in a range of sign boxes. SloanLED Poster Box 3 is an excellent choice for lighting large, shallow fabric-faced light boxes and is 20” long and boasts an output of 1700 LM.

Pre-Plan, Choose Right

There is no question that the sign industry has undergone massive changes with the advent of LED technology over the past twenty years. There are a large number of LED options available today. Understanding the application, pre-planning, and then choosing the right product can speed up installation, improve performance, save money, and make for a happy customer.