Modules are still the most commonly purchased LED product in the sign industry. LED modules were originally developed to replace neon in commercial channel letter applications. With improvements in LED output and lower costs, the applications of modules in the sign industry has expanded to illuminated cloud signs, border products, and all types of cabinet signs. These LED strings offer tremendous flexibility and are available in a plethora of sizes, colors, configurations, and beam patterns today. In fact it can be pretty confusing because of the sheer number of choices. First, let’s take a look back at LED module development.

Looking Back

I remember some of the first LED modules back that were released in the early 2000s. At that time the only commercially available LEDs that were reasonably priced were 5mm and 3mm LED lamps and these modules were an evolution from the indicator light business. 5mm lamps had a led frame with 2 pins and had an epoxy cast coating around the die. They were normally soldered to a through-hole PC board.

Due to limited heat dissipation and small chip size they typically had lifetimes (which back at that time we described as the time to 50 percent light loss) in the 10-25,000 hour range. They were also typically cast with a 50-degree beam pattern, which meant the modules had to be placed pretty close together and typically used only in sign depths of 5” or greater to prevent hot-spotting.  

Some manufacturers recommended mounting these products on the return of the channel letter. I remember Teledyne had a module that had the 5MM lamp sticking up above the PCB board and the sign maker could then bend each individual LED to aim each lamp to reduce hot spotting—pretty rudimentary, but heck these products were the “Apple I computers” of our time.

To improve heat dissipation, LED module makers released the piranha or superflux package. These materials had four pins to dissipate more heat, provide slightly better lifetimes—but most importantly, they had a 100-degree beam pattern, and no more hot-spots! LED modules for signs were off to the races.

Do you remember the original GE Tetra, US LED Right Light, Agilight TuffRayz, or SloanLED's Apollo product? These were all early systems that used piranha packages.

Enter SMD

The tipping point in the industry came with the adoption of cost-effective SMD LED systems. The surface mount devices, coupled with advances in the chip itself, allowed for both better heat dissipation and increased operating currents, which resulted in brighter LEDs that lasted longer and an even wider 120-degree beam angle.

Today a large portion of the LED systems utilize SMD lamps. There are a large variety of SMD lamps, with various chip sizes, quality levels, and drive requirements which could easily take up the whole of this article. 

Suffice it to say, SMD lamps are the mainstay lamp type in today’s channel letter modules. A module using a quality SMD lamp—driven properly and with adequate heat dissipation—can last well over 50,000 hours to 30 percent light loss and is an order of magnitude less expensive than just a decade ago.

More recently a few manufacturers (Principal LED, Tridonic) have used chip-on-board (COB) processes in their LED modules in which the diode die is mounted directly on the PCB. This can serve to further improve heat dissipation and extend the LED life. The illustration in Figure 1 shows some different types of LED lamps and their improvements in heat dissipation as well as typical lumen output in commercially available LED modules.

What's New with LED Modules?

So what is new and what is to come with LED modules? Many LED modules today come with an onboard constant current driver IC as a standard feature. This allows the sign maker to run a long daisy chain of modules without losing light from the first to the last. This makes wiring easier without having to split the load (and that is really about it).

Some overzealous sales people claim that the constant current driver IC makes the LED last longer by maintaining a constant current in the event that the power supply voltage increases.  This is true in theory, but in practice most LED modules are driven below their maximum drive current and even a half volt change in the driver will have limited impact on the LED module in a properly design constant voltage module. Regardless, constant current IC driven modules are pretty commonplace and come with only a slight premium over their constant voltage predecessor.

The other change in LED systems is the level of encapsulation. Historically, LED modules for signs were simply PCBs that were often exposed and maybe had a snap around clam shell type housing. Today many of the LED modules are over-molded and rated as high as IP67 (see Ingress Protection chart). One thing to keep in mind is that more IP protection does not necessarily mean better. Last I checked very few signs are operated under water.

Fully over-molded parts can often act like an insulator trapping heat inside, which can actually lead to faster-than-expected light degradation. For most commercial signs outside of high salt spray and humidity environments, anything over IP65 is generally acceptable. Regardless, these over-molded systems definitely reduce the chances of mechanical failure due to corrosion.

Batwing Optics

The biggest change in LED modules recently is in regards to optics. With LEDs being more than bright enough for many applications and the trend toward thinner and thinner channel letters and cabinets, many module makers have incorporated batwing optics to redirect more of the light laterally providing more even illumination on wider spacing (see Figure 2). This allows for the use of less product with increased coverage area per module.

Osram Sylvania recently released its BoxLED Plus family of LED chain modules, which is ideal for illuminating channel letter signage with shallower depth faces. These modules also utilize Flat-Ray optical lens technology to ensure uniform illumination at the sign face, even at minimal depths. They are available in three sizes and multiple color temperatures to meet the requirements of any application. Osram Sylvania has also taken this chain module approach with a Flat-Ray optic for use in cabinet signs.

BoxLED Plus and BoxLED Plus DS LED chain modules are ideal signage solutions for lighting single-sided and double-sided box signs, respectively. New for this family is the addition of Fluorescent-to-LED Retrofit Base Adaptors that slide onto the ends of the accessory track and allow for mounting into existing R17d fluorescent sockets. This allows for quick retrofitting of any size fluorescent box signs utilizing up to F96T12 lamps with only four components instead of stocking a large variety of sizes of LED retrofit sticks.

BoxLED Plus modules are now available in four color temperatures (3000K, 4000K, 5000K and 6500K) and BoxLED Plus DS modules are available in 6500K and 5000K color temperatures.

"Osram Sylvania is dedicated to providing long life LED solutions that meet the needs of the signage industry, whether it is for new or retrofitting existing signs," says Erich Bockley, signage product manager, Osram Sylvania. "Our LED modules provide high-quality light that lasts up to 50,000 hours, which significantly reduces sign maintenance costs. Now we have solutions for small, medium and large channel letters, as well as single and double sided box signs."

According to Mark Abernathy, director of sales, at Houston-based US LED, LED module-based cabinet solutions is a major focal point in their development process. US LED recently released their TD1 and TD3 cabinet modules which have a special optic and hits on all four of these customer drivers. “The new TD modules can be mounted as close as 3" from the face with 8" spacing between rows," Abernathy says. "The flexibility continues when you move the modules further from the face increasing spacing from row to row up to 24" apart at a 12" depth. This gives you the ability to create even lighting in a variety of depths all while using less product. This flexibility and ease of use keeps your project and your crews efficient and effective. At 240 lumens for TD1 and 360 lumens for the TD3 with an IP66 rating they are ready for any signage conversion,” according to Abernathy.

What's Next?

So what is next? I still think there is more to come as long as LED manufacturers continue to fight for new ways to capture market share in the sign industry. Recently, my company, Principal LED, released the world’s first true-AC LED sign module, called Powerline. The module has a batwing optic and uses a special chip that can run directly off of 120VAC directly. True AC means that there is no rectification circuitry on the PCB, with the only active component being the LED itself.

By removing the need for a power supply, Principal has removed the major point of failure in LED sign systems. In addition, the sign maker can daisy chain up to 1,600 modules on a single 20A circuit; and the system comes standard with a five year parts and labor warranty.

LED modules continue to evolve and have come a long way from a few indicator style lamps soldered on to a PCB to IC controlled over-molded units, batwing optics, and modules that don’t even require a power supply. The fact is that there are some excellent choices for just about any application or environment at great price points.