More On Led Applications & Technology
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More On Led Applications & Technology

Do you know just how fast LED technology is changing?

By Fritz Meyne, Jr.

Do you know just how fast LED technology is changing? Or how quickly it will meet the needs and demands of the future sign industry? Well let me tell you, PDQ! (If you do not know, PDQ is an old acronym for, let’s just say "fast").

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  • Now that I am self-employed (read that as broke by design), I am amazed at the information LED assemblers are seeking. Rest assured the LED assemblers out there and the actual LED manufacturers want to know about the sign industry. Even though they have some misconceptions about neon, they see the vast market potential. On a recent visit to the west coast I had the great fortune of learning some of the new LED applications that will be forth coming to a sign show near you. I was invited to one of those long lunch meetings. You know the kind, you want to go but you don’t want to have to eat "around" the conversation because your food will get cold (as if it was supposed to be hot) and your table manners, your breath and teeth might show signs of a poor upbringing!

    The bottom line is this: in the very near future you will see LEDs take a major jump in performance and application uses. Because of the nature of my meetings and confidentiality issues, I can not go into detail at this time. I can say that I am very impressed with what is coming to our industry, and I’m confident you will be too. As for present LED technology, let's take a look at what’s currently available, what we can actually put in our products today.

    If there is still a weak link with LEDs technology, it is the DC voltage Class 2 power supply. Now before you go on about how well your Class 2 phone charger works, remember this; I’ll bet you do not use it outside in the cold and rain, or the heat and rain or in high humidity for days, weeks, months, and then years. Your phone charger gets used in your home and or car, both well controlled environments.

    Not withstanding UL vs. ETL, as I have written before, there are logical “commercial” DC power supplies that can be used, however they present UL issues. So as most electrical sign shops strive for and/or have UL certification, ETL then becomes an issue. Using Class 2 power supplies presents a whole new learning dimension for the estimator and the installer. The End User pays for multiple J-Box connections and additional material costs due to a potentially large number of Class 2 power supplies.

    I believe LEDs are great and will offer endless new opportunities for all industries, however, as with any new technology, there is a learning curve. Let’s look at White LEDs. First of all they have a very high K temperature. K stands for Kelvin, which is a lighting measurement for the color temperature of the light. Think of neon 6500 White vs. neon 4500 White as this number is actually the K number. The higher the number, the more “blue” you see. As a reference, sunlight is rated at 5600K and is the plus or minus reference used for all lighting. The lower the number, the more “yellow” the light will look. Look at the color difference between DHO fluorescents vs. Cool White fluorescents and you’ll start to get the picture. This LED white has caused many a concern already with sign shops and End Users. White LEDs have a variance in visible color temperature (K) that must be taken into consideration in halo and/or face lit applications.

    We were recently involved in the lighting specification of LEDs and fiber optics for a very nice high end custom multiple site sign project. There was no traditional light specified, only fiber optic (behind white plastic for face illumination) and LEDs for the halo application, in Blue and White. I must say that the Blue LEDs gave a neon quality halo effect that was much better than we anticipated… most of you would be hard pressed to tell if it was old or new technology. The White LEDs gave a nice glow on the “one” test letter (on which the approval was based), however once all of the letters were in place we saw three or four different shades of white light. This was not good.

    The LEDs were mounted inside fabricated halo letters with the light beam shining onto the signs semi gloss pylon cover background through a clear plastic “diffuser”, as described above. In theory this should have worked, but in practice it did not and was a failure. Someone else recommended the LEDs be mounted indirect and the clear diffuser swapped for a white plastic. Can you guess what happened? By making two changes in the original design intent, the light output was diminished visually by about 30%. What would have worked was the indirect approach, keeping the clear backs, which would have keep the intensity level higher. The good news was that the End User bought off on it, so there lies another lesson, “The customer is always right”. I think most of you would not have accepted the light levels since they were not nearly as bright as white neon.

    Another test we performed was to work with several white plastic samples and translucent PSV. We even sandblasted clear plastic searching for a diffuser that would give the least amount of light reduction. None of this would have necessary had we used red spectrum LEDs. Surprisingly, what worked the best was sanding the clear plastic with a DA sander. It gave us the maximum light transmission with no visible imaging of the LEDs! We had to go with two layers of PSV to eliminate the LED imaging (seeing the point of light). With the white plastic, the LED Imaging problem was corrected, but there was way too much light loss.

    So the point of all of this is, before you stick your neck out using white LEDs on any given project, get some firm backup on what the final brightness and K will be. Also consider doing your own testing. The examples above were a learning curve not only for us, the sign fabricator, but for the OEM as well. As I always say, “Buyer Beware!” Just to make another quick point, we used white LEDs behind a green plastic face. The high color temperature of the LEDs shifted the nighttime color into a blue-green. As you might guess this was not acceptable to the End User.

    In closing, remember the Red spectrum of LEDs do not have these concerns. However when using any LED as a “halo” source, remember to design around the multiple imaging many different points of light will give.

    Fritz has been serving the retail and OEM sign and lighting industries with ISA, USSC, FSA, SEGD and ILA and has over fifteen industry articles in print and electronic circulation formats. You may contact him at: 1298 Blue Heron Lane N, Jacksonville Beach, FL 32250, fritz@vidsol.net or 904-247-4308.

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