LED bulbs have a bright future

An evolution is underway in lighting technology that could change the bulbs you use on your boat. While incandescent and fluorescent lamps are the current standard, the future could well belong to light-emitting diode (LED)-based lamps. One small company in Nashville, Tenn., called Deep Creek Design, Inc., is producing LED bulbs that, while pricey, draw very little power and should last for more than 10 years of continuous use.

LEDs, of course, have been around for a long timeremember the Pulsar watches of the early 1970s? One common application for LEDs on boats is indicator lights on electrical panels. But now brighter LEDs have been developed that can handle other tasks. Recently, automakers have started using strings of LEDs for mid-line brake indicator lights. And, according to industry sources, in a few years the only incandescent lights on the average vehicle could be the headlights.

Until recently, most LEDs used in marine and non-marine products have emitted red and green light. But now there are also amber and orange LEDs. While there are applications for all these colors, the chromatic holy grail of LED development has been a general-purpose white lightafter all, most sailors would rather settle into their bunks and read the latest technothriller by white light rather than green or red. Since the largest use for general-purpose lighting will be in the home, where few people are concerned with dark-adapting their eyes through the use of red light, white LED lamps have the biggest market potential. White LEDs are now becoming available, and the world of lighting will never be the same.

Standard bulbs work fine, so why replace them? The answer is based on the physics of producing light via incandescence. The conductive filament wire in an incandescent bulb is made of tungsten. This metal passes electricity, but not without some resistance. As the electrical energy pushes through the filament, the wire gets hot. Soon the filament gets hot enough to radiate energy in the visible spectrum (or, in other words, it glows). The drawback to this process is clear enough: most of the electrical energy pumped into the tungsten filament is doing little more than producing heat (this resistive process isn’t great for lights but does work well in a toaster). Incandescent bulbs are simple and cheap (in general, they haven’t changed much from the early models developed in Edison’s Menlo Park labs). But this type of light source isn’t terribly efficientonly 4% to 6% of the electrical energy put in comes out as light. All the heat produced (a 100-watt bulb can warm up to almost 450° F) takes a physical toll on the filament. Tungsten atoms actually “boil” off the wire (that’s what all that black dust is inside a burned-out bulb). Eventually, the filament gets thin enough that it breaks. (Incandescent bulbs tend to fail when you first turn them on. The filament is cold and has less resistance. The lower resistance means more current surges through the wire, and this fractures it.)

Fluorescent tubes dispense with the incandescent filament and produce light by passing an electrical current through a conductive gas. This type of lamp is more efficient, runs cool, and the bulbs last longer than tungsten bulbs (see “Long-lived lights,” Issue No. 88). However, they are more complicated than incandescent lamps, and the bulbs are still subject to physical wear and have to be periodically replaced.

An LED, however, is a solid-state device that experiences virtually no wear and tear no matter how much you use it. LEDs are fairly simple devices composed of silicon that has been laced with impurities to enhance desired electrical characteristics. Light is produced as electrons cross the diode’s “pn junction.” One part of the diode has been doped to produce “p” or positive-type silicon and on the other side of the junction is “n” or negative-type silicon. The diode emits photons (light) when a forward current is passed through the junction.

While incandescent bulbs produce white light (tungsten filaments produce light that is not technically pure white but is displaced slightly toward the red end of the spectrum), LEDs produce specific colors of visible light depending on the materials used to dope the silicon. Red LEDs are usually made using gallium arsenide-phosphide, for example. Producing white light (which is a mixture of all wavelengths of visible light) is a matter of finding the right compounds to add to the silicon.

In addition to red, green, amber, and orange LEDs, there are blue LEDs and blue-green LEDs, and now a Japanese company called Nichia is selling a white LED. Nichia has figured out the right dopants and physical structure for producing blue-white light. The light from the diode then hits a phosphor layer applied to the inside of the package’s clear plastic enclosure. This phosphor layer is stimulated by the light coming from the diode and produces white light. The two lights mix to produce a silvery white light that is reportedly quite bright. “For 30 years companies have been trying to perfect white LEDs,” said Ken James, a design engineer who does LED lighting projects for Deep Creek. “In the past two years, they’ve done it.”

The early leader in LED lamps for marine applications is Deep Creek Designs, a small operation run by Rob Hoffman out of his home in Nashville. Hoffman’s day job is as a commercial photographer specializing in architectural work. As a photographer he has a great deal of experience with lights (don’t ask his opinion on halogen bulbshe vigorously dislikes them). And, as a self-confessed inventor (he holds several patents), he became intrigued with LED-based lights after the red lights on the boat he had at the time didn’t satisfy him. “The idea came from my exasperation with red-tinted bulbs,” Hoffman said. “The red coloring didn’t work very well.”

Since he knew that LEDs were ideally suited to producing red light, Hoffman purchased a few LEDs from Radio Shack and began to work with them. He hit on the idea of clustering them and then using epoxy to glue them into the standard two-contact bayonet-type mount used in many marine incandescent fixtures. He also included a set of resistors for even power transfer to the seven LED cluster. The result was Hoffman’s first red night-vision cluster bulb. This bulb ran continuously on his boat for almost six years.

His current bulbs produce 500 foot-candles of light measured at the surface of the LEDs. These bulbs can be retrofitted into any 0.60-inch-diameter single or double contact bayonet-type fixture. Hoffman later added amber LEDs.

The bulbs, all seven LEDs together, reportedly draw only 0.06 amps at 13.8 volts DC (making it a 0.828-watt bulb!). Thus, 10 of these lamps would draw 0.6 amps. There is no filament to burn out or be damaged by handling or vibration.

Probably the most impressive aspect of these lamps is their longevity. They are rated by the manufacturer for 100,000 hours of continuous use. That works out to more than 10 years of lifeif you left the bulb on all the time. With this kind of life span you might have the bulbs for longer than you own your present boatwhen you sell the boat you’ll want to take them with you!

Of course, all this solid-state lightning technology isn’t cheap. Each red bulb is $20, and the amber lamps go for $25. But considering the low current draw and the promise of long life, these bulbs make sense. By the time this story goes to print, Hoffman plans to be offering the latest white LED bulbs (according to Hoffman, their color will be similar to cool white fluorescent lights). The new white bulbs will be somewhat pricey at more than $70 each.

Deep Creek Design is now testing prototypes of replacement LED bulbs for Aqua-Signal series 40 navigation lights, including an anchor light bulb that Hoffman hopes to have ready later this year.

Because these lights use so little power, it’s feasible that several of them could be wired together on one circuit that is turned on at night and left on. “They would give a soft red glow throughout the boat,” Hoffman said, “helping crewmembers to get around.” The low power requirements of LED-based lighting make it especially appealing in conjunction with solar panels and wind generators. “For a small boat, lighting is a major energy draw,” James said. “With normal lighting, you’re constantly looking at your batteries and checking their state of charge.” Since LED bulbs use so little power, a solar panel now becomes a robust charging device, easily able to meet the demands of the boat’s lighting system. In this way, LED lighting makes solar and wind-power units more effective.

As the price comes down for colored, blue-white, and white LEDs, this type of lighting could become very popular aboard the average voyaging boat.

By Ocean Navigator