usled

Living the LED Life

​Ryan N. Fugler is a former editor of WRAPS magazine. 
 

Much has been written about the longevity of LED lighting systems as compared to conventional incandescent technologies. However, even these highly efficient components and products do not last forever. We know from experience that there is a period of depreciation with all electric signs; and sign makers are keen to maximize the life of their LED-based signage projects.

When we replace a conventional lightbulb in our homes, we understand that the chances are high that we’ll have to replace that bulb again at a future date. With LEDs the expectations are higher for a longer durability. With that in mind, there are steps a sign maker can take to ensure the life or improve upon the efficiency of lighting components without having to continually replace pieces. 

“When an LED chip fails it’s usually because it’s either overdriven—given too much energy—or the device before it in the chain (like a resister) is not working properly,”  explains Mike Bluhm, director of product solutions, SloanLED.

So as a rule, Bluhm adds, sign makers should make sure to scrupulously follow the manufacturer’s recommendations for energy load to the LED, and to make sure that the components are wired in properly.

“Every LED manufacturer rates their LEDs at what current you’re allowed to put in there,” Bluhm continues, “but there’s no ‘Current Police’ running around saying ‘you can’t put in more current,’ so our biggest challenge as an LED manufacturer is that we have people who overdrive LEDs.”

Overall quality is another concern, and one that can affect the entire sign system if the LED modules are faulty. “What we have found is that people need to start thinking about quality again,” says Scott Cutcher, vice president at TMT LEDs USA.

In addition, there are questions about external factors, the initial design, and overall location of the sign that can contribute to the success or failure of an LED project. Let’s investigate these areas to determine how sign makers can provide the best product to their customers.

Quality and Construction

“Right now we are at a critical turning point with LEDs,” Cutcher says. “We’re still really heavily in the early adoption stages. We’re 15 or 20 years away from mass adoption. But it’s gaining momentum really quickly.”

This is important to note because of the tremendous amount of different LED products that have entered the scene, and it’s up to sign makers to weigh the factors of cost versus quality.

“A lot of cheap products have flooded the market and there are many questions about what makes a good product versus what makes a bad product,” Cutcher says. So, ruling out user error, “if an LED fails, usually there are bad circuit welds on the PCB boards. Stay away from a product that isn’t backed by the domestic distributor, or that is backed by someone who isn’t representing the product here in the U.S.”

Another example of poor quality is when the “wiring is not ‘seated’ properly, or soldered to the actual module,” he continues. “When they come snapped into the tray, people pull on the wires to pop them out of the tray and that’s where a lot of the failure happens."

Bottom line here? "Don’t pull modules out by the wires. Better yet, get a better product; one where the wire runs all the way through the module, which the higher end ones do. Ones they call a full-solder to the board—not a tack, not a glue. A lot of people will glue it and that’s another big issue.”

Lower-quality LEDs may also be susceptible to environmental extremes. “A lot of cheap products aren’t rated for higher temperatures,” Cutcher says. “Temperature is a big deal, especially in the West. When we test our products, we make sure we are at least 50 degrees Celsius (120˚ F) because when you put something inside of a sign cabinet it’s going to heat up. You’re going to see the cheap components start to be outflanked by high-efficiency products because an efficient product uses less power, requires less labor and less of the product itself is needed to light something properly.”

The LED Break Down

In the past, Bluhm has hosted seminars to explain how LEDs function in a channel letter application, and just how much power can run through the modules before a problem occurs. He explains, “we literally took the resister off the board of the channel letter module and ran a variable current power supply where we can turn up the current from 30 milliamps to 60 milliamps to 90 milliamps. The audience could see it appeared to be brighter and brighter—that is until it wasn’t. There was a poof of smoke and it was dead.”

In this case, the LED was overdriven; but there are other instances when an LED sign will fail due to the connection.

“The drivers are more likely to fail than the modules,” says Ron Farmer, CEO of US LED. “Drivers have an inherently shorter life since they have many more components and therefore, more points of failure. And their reaction to heat is failure rather than LED’s premature dimming ‘failure mode.’”

But there are ways to avoid a power supply failure.

“Wiring connections and proper module mounting are the most preventable points of failure and not to be ignored,” Farmer continues. “Of course, the basic quality of the LEDs and driver components combined with their manufacturing quality are the most important contributors to the lifetime of the system.”

To support that view, Cutcher emphasizes that there are more points of failure with multiple connections, so a configuration with several connections to the power supply has a greater risk of failure than one with minimal connections.

“If you have a cheap product that you have to split the load and make two connections to the power supply,” explains Cutcher, “versus a more expensive product where you only have to make one connection, you just hedged your bet that you’re going to have 50 percent less failure probability.”

The fact of the matter is that cheap products are everywhere nowadays, and shops looking to fulfill low-bid jobs are using lower-end, inexpensive products, and quality inevitably takes a back seat.

“It used to be hard for me to find channel letter signs that were failing with cheap, bad modules, but now I see them everywhere I go,” Bluhm says. “You really shouldn’t ever see a module out, you should see the whole product depreciate over time, where it’s not as bright as it used to be. But seeing individual LED modules going out—that’s just a bad design.”

The Importance Of Design

In an LED sign project, one with channel letters for example, the LEDs are typically placed on the back of the letter facing forward.

 “Therefore, even if water pools at the bottom, you would only lose the bottom,” explains Bluhm. “UL requires a drain hole to be installed in the bottom of all letters. If water were to get in there you wouldn’t want it to pool up and cause electric shock or a fire.”

Because water is one of the elements that can cause immediate failure in LEDs, it’s best to avoid it as best as possible. In many instances, LED products are rated high enough – such as at IP67 or IP68 – that they are virtually water resistant. However, over time, enough water penetration will start to affect the LED. 

“Water intrusion can lead to failure or degradation of both the modules and drivers, depending on their construction,” Farmer says. “Even if the components are IP66 the connections can become corroded and fail when exposed to water.”

For this reason and several others, it is important that the design of the LED sign is engineered properly.

“As a manufacturer we recommend layout programs,” Cutcher says. “We submit a ton of data to them and they put it into an algorithm to maximize the light output according to the IES files, which tells them where the light goes. And according to our real-world testing of row spacing they say this is the optimal way to lay it out.”

A well-conceived design not only protects LEDs but also maximizes their lighting output.

“Proper placement of LED modules is vital to a satisfactory result with any sign. A good sign maker will test every product in his various cabinet and channel letter scenarios to determine proper placement based on sign depth, channel letter stroke, and face material,” says Farmer. “Even though his LED lighting supplier has recommended a layout, if the lighting product is being used at the limit of its capability, a slight variance in face material translucence and/or sign interior reflectivity can alter historical results. Of course, the proper placement of modules will result in even light along the face of the sign, whether cabinet or channel letter and it is worth a quick test before the sign leaves the shop.”

The materials that are used within the sign, as well as sign faces and overall depth, will contribute to the decision made on the design level.

Cutcher reminds sign makers to consider “other factors such as reflectivity of the sign. We tell people all the time to paint it white, do not leave it aluminum because you’re going to have hot spots and it’s going to look weird. You want to have an even surface that reflects properly. Make sure whatever aluminum you use, you paint it. That light is bouncing all around in there and that’s going to determine how few or how many modules you need.”

He continues by recommending a polycarbonate face because it is translucent, and employing a good lens depending on the depth of the sign. But as a general rule of thumb, it’s best to layout all components of the sign and eyeball how the lighting can be improved.

“Whenever sign makers are using a new type of LED, they should get a layout and then from that layout, actually see if they can eliminate modules,” Cutcher says. “On average, you can eliminate one module per letter. So you actually can get great and even lamination with today’s lenses and not have to have as much product in there. Now, brightness is subjective and people need to remember that. We always start off with even illumination and work from there. You can always scoot in the modules a little bit and get more illumination.” 

External Factors

Heat is a nuisance when it comes to LEDs. The same isn’t true with cold temperatures, but heat is one of the major contributors to failure in LED signs.

“The two biggest external forces that can create havoc for led signs are heat and moisture—period,” Bluhm says. “On all LED products known to man, even parking lot lights, if it’s designed where the heat is not dissipated normally off the board it can fail. Engineers come up with different ways to make the heat dissipate off the board.”

One of the best ways to extend the life of an LED is to know where it will be placed and install the LEDs so that they are not subject to high heat levels.

“Control the moisture and the heat, make sure they don’t mount the power supplies,” Bluhm says. “UL requires a 4" clearance between power supplies and nobody follows that rule. They either stack them on top of each other or they put them too close to each other. With a bunch of heat-producing devices next to another one, the next thing you know you’ve got a Suzy Bake Oven.”

Bluhm recalls a project that was done in Las Vegas where temperatures can get to the 100 to 120-degree range during the summer. The sign was running around the clock and the power supplies were installed inside the cabinet in a way that “literally melted the over-mold off of our modules. The LEDs were still working but the over-mold was melted. But the LEDs would eventually get killed, so proper location of power supplies and spacing is key.”

But it isn’t just variable factors such as weather and temperature—the actual products that are used can make all the difference in the world. Again, it goes back to the quality of the components.

“The quality of the fabrication and materials will greatly enhance the life of the internal lighting,” says Farmer. “Providing the correct materials for the application will protect and help the internal parts achieve their maximum lifespan. The correct face material can also help maximize the light output for any internal lighting.”

As for setting life expectations for an LED sign, the typical answer is somewhere around the 50,000-hour mark. But there are higher-rated LEDs on the market that can extend the life of the sign.

“You’re starting to see ones that are rated at 100,000 hours,” says Cutcher, pointing to quality again.

For sign makers, it’s important to stand by the quality of the product. Obviously, it will not last forever, but with the right planning and inclusion of dependable components, an LED sign will achieve maximum life expectancy.