LED or Neon … Revisited

Everbrite manufactures large numbers of neon signs each day. We also manufacture an increasing number of signs utilizing LEDs as a light source or visual display. We see the tradeoffs of the two lighting technologies every day. While we have a long history in neon-product development and manufacturing, we see huge potential in LED technology and expect some products which are currently dominated by neon being in fact transformed almost entirely to LED illumination. We wish to offer a different perspective on the information stated and conclusions drawn in Marcus Thielen’s article "LED or Neon?"
 

LED applications

While LEDs have long been used in direct-view mode for indicators and message displays, the availability of higher performance/lower price LEDs has made their use as illumination sources increasingly more viable recently. The use of LEDs to back light channel letters, accent striping and the like has proven to be highly effective for sign products with monochromatic sign faces, especially red. These applications can easily be made to utilize most of the LEDs’ output, making them highly efficient. This type of application is generally not required to be illuminated in the daytime, greatly reducing the number of LEDs required, power consumed and heat generated.

The application cited in the article for comparison was exposed neon. It is very difficult for LEDs to compete with exposed neon in terms of "brightness" and the cost to achieve the continuously uniform brightness of exposed neon. As with any technologies being compared, scenarios can be devised in which one candidate performs better than the other. In any case, there is a large market for back-lit channel letters in the U.S.A., and we see LEDs assuming an ever increasing illumination role in them.
 

LED life

The article derates LED life to 5,000 – 10,000 hours. This is extremely short for red LEDs, which should be able to enjoy lifetimes approaching ten times those numbers, in properly designed applications. InGaN (blue, green, white) LED life is shorter than AlInGaP (red, amber) LED life and any LED’s life can be shortened by improper application, just as with neon.

In the back-lit applications cited above, the operating temperatures can be kept quite reasonable and therefore longer life can be expected. It should also be pointed out that even when the LED does reach the end of this rated life; it has a specified reduced output, not complete failure.
 

LED performance and cost

In illuminated signs, as well as any lighting application, the benchmark should be how the user perceives the product. We propose that surface "brightness" or luminous intensity (candela/m2) be the benchmark, as opposed to luminous flux (lumens). This allows for more relevant comparisons. We have done some of our own comparisons, actually building neon and LED versions of the same channel letter. In one study, we used a 20-inch "W" to do the comparison. The neon version contains approximately 11.5 feet of 15 mm double-stroke clear red neon and a 30 mA electronic power supply. Power consumption is 38 Watts at 120V input. In order to produce the same surface brightness (212 cd/m2), 50 LEDs are required, with a power consumption of only 9 Watts at 120V input.

Our experience is that the system cost of LED illuminated signs is much closer to that of neon than the author claims. When the life cycle costs including packaging, shipping, installation, maintenance and energy are considered, red LED applications clearly "outshine" neon.

No one lighting technology is ideal for every application; both LEDs and neon will be around for a long time!

Frank Mohacsi
Director, Lighting Technology
Everbrite Inc.
 

LEDs Defended

Regarding your feature, "LED or Neon?," Marcus Thielen’s conclusions are premature and based on an analysis that may be misleading.

First, it wasn’t made clear that the experiment Marcus performed was based upon exposed neon vs. exposed LED. Because he states that he is conducting experiments on LEDs in channel letters, the reader is led to believe he means regular covered channel letters. But his data is relative to exposed neon vs. exposed LEDs.

When he says LEDs aren’t the appropriate light source for most exposed applications, he is right. Energy savings and cost/brightness become favorable with LEDs when used to backlight a piece of colored plastic — a filter.

A filter blocks or prevents something from passing through it. In this case, it filters out the wrong colors. White light is generally made up of the full spectrum of light, which includes all the colors. LEDs only produce a single color. This is why they are called monochromatic.

If the "filter" or face of the letter is the same as the color of the LED, all light produced by the LED gets through, and thus appears bright. No other light source claims this advantage. It takes just as much time, material and energy to produce each color of light, so whatever we don’t use is wasted. Even red neon produces many colors, although it appears red/orange.

This concept is the main reason that LEDs can readily compete against conventional light sources in colored applications. Sure, there are other reasons to use LEDs, where durability, life and compact size are an issue. But the main reason is LEDs’ overall cost efficiency in producing a colored light effect. It’s the key reason why LEDs are in traffic signals, exit signs, automotive taillights and channel letters. LEDs are the colored light source for today and the general-purpose light source for tomorrow.

— Jim George, president
Permlight Products Inc.
Tustin, CA

Misleading test criteria "exposed"

In response to the article titled "LED or Neon?", we at GELcore do not feel that LED systems were accurately represented. In fact, the article was based on exposed neon, whereas most LED systems have been designed for covered channel-letter applications. These applications have different illumination requirements.

When discussing light output of a channel-letter system, the most important feature to examine is the amount of "usable lumens." Measurements should be made according to the luminance or intensity per unit area on the channel-letter face. Measurements of this type would show equal application output to neon with up to 80% energy savings for some red LED systems.

In addition, the article challenged the "advertised 100,000 hours lifetime of LEDs in outdoor applications" and the topic of application conditions. In correct terms, a properly designed and managed LED system can easily exceed the 100,000-hour life. Most LEDs have a storage temperature of 210 degrees.