Features January 1, 2003 Issue

LED Lights: Low-Power, Long Life

The revolution continues. LEDs serve a growing range of uses on board. High efficiency, small size, and extreme longevity - what's not to like?

Light Emitting Diodes have been around for a long time now. They first appeared as dim red displays on things like calculators and early digital watches. Their main advantage was their very stingy consumption of electrical power, which allowed them to be used with extremely small batteries. 

Hella Marine's Naviled nav light eliminates
corrosion at sockets, and bulb failure. Wiring
is potted permanently in epoxy. At the moment,
LED nav lights are for powerboats only.

Well, this low power consumption is still one of the main advantages of LEDs, though improvements in technology have made it possible to make them much brighter than before, and in a rainbow of colors. Instead of just being bright enough to be seen, as the earliest ones were, new LEDs are bright enough to be considered as an alternative to - and often an improvement over - more conventional incandescent and fluorescent lamps. In addition to their low power demands, LEDs are extremely rugged, last virtually forever, and can be made physically quite small. They're ideal for applications where colored light is required, such as in red or green sidelights for boats. While these are now lit by white incandescent bulbs shining through colored lenses, LED lights can produce colors immediately.

LEDs are finding their way into flashlights, traffic signals, signs and displays, and automotive signal lighting, and their use is increasing at a rapid pace.

How They Work
We've covered LED products (flashlights and anchor lights) in recent years, but it's worth reminding ourselves of how LED technology works. A detailed explanation requires a basic familiarity with semiconductor theory and a bit of quantum physics. In general terms, though, an LED is a diode - a junction of a p-type and an n-type semiconductor called a p-n junction. A diode normally passes electricity in one direction and blocks it in the other. You encounter diodes in battery chargers and in alternator regulators - they are usually installed to change AC to DC.

Conventional diodes give off some energy. It's the normal result of moving an electron from a high-energy area at one side of the junction to a low-energy area on the other. With a conventional diode, the energy is in the form of heat; in an LED it's in the form of light. Theoretically, an LED could have an efficiency approaching 100%; in practice, there's some heat produced, which lowers the overall efficiency of an LED to about two to three times that of an incandescent bulb.

LEDs tend to produce light of a single color. Originally, they came only in red, but yellow ones soon were developed, followed in turn by green, blue, and, most recently, white. Red is the most efficient LED color, followed by the others in the same order in which they were introduced. Over the past decade, LED efficiencies have been steadily improving.

Incandescent lamps all work the same way: Electricity passing through a wire heats it to white heat, allowing it to emit light. It also emits a lot of heat, which you pay for but which usually doesn't do you any good. The wire - or filament - is generally made of tungsten, which takes the very high temperatures better than other metals. An incandescent bulb works most efficiently when the filament is as hot as possible - and this is also the situation making for the shortest bulb life.

LEDs, on the other hand, don't get hot. They're at their most efficient when the minimum possible heat is being generated. For all practical purposes, an LED will last forever - manufacturers are quoting minimum service lives of 50,000 hours. Because of this, it's generally not necessary to provide for LED "bulb" replacement. This, in turn, permits the appliance designer to seal the bulb and all connections, eliminating major points at which corrosion can occur - an important consideration for marine use.

LEDs tend to provide light in a single direction while incandescents are omnidirectional. Effectively, this means that incandescents are best for floodlighting and general area lighting while LEDs shine (sorry, couldn't resist) where a focused beam is called for. LEDs, as noted above, are far better than incandescents for producing colored light.

At this point, LEDs are considerably more expensive - in initial cost - per lumen of light produced than more conventional lights. The combination of low power requirements, long-life and small physical size, though, is opening new areas of lighting that were not previously practical. Let's review a few examples.

Light Pen
This gadget - not to be confused with a penlight, which doesn't write, or a pen that doesn't weigh much - is the size of a conventional ballpoint pen, measuring 5-1/2" long and weighing 0.6 ounces. The 3/8" diameter barrel flares out to a 1/2" diameter at the top, housing a couple of hearing aid batteries. At the writing end, there's a yellow LED fixture surrounding the ball point of the pen.

When you turn on the light, by twisting a knob at the top end, you get a one-inch circle of light on the page. We've been using a couple of these for months now. They've proved very handy for making notes and marking charts; for providing just enough light to keep you from barking your shins in the dark, and for reading paperbacks at 0300 while the spouse tosses and turns. The light isn't bright enough to seriously affect night vision.

The cap is removable, rather than having the pen retractable. The cap was thoughtfully made transparent so that you can tell if you forgot to turn the light off before putting it back in your pocket. In fact, the light works pretty effectively with the cap on - it's slightly muted and diffused.

The Light Pen just couldn't be made without LED technology. There's no way in which you could squeeze enough batteries to give even a tiny incandescent bulb a reasonable service life in a pen-sized case and still have room for the pen itself.

Weems & Plath sells it for a very reasonable $4.99.

SmartLyte
The little light that goes on when you open the refrigerator at home is a great idea. So is the dome light in your car. If you've ever wished that your toolbox, or your boat's lazarette, or almost any other container were similarly equipped, Acolyte Systems, Inc. has an answer for you. No wiring; automatic operation. And (in case you haven't guessed), it features an LED.

The gadget is called a SmartLyte. It's a miniature hockey-puck shaped plastic case 1-3/8" in diameter, with the business end of an LED bulb protruding about 1/4" from one edge. On one face there's a push-button; on the other, a 1"diameter battery case. The whole thing is only 7/16" thick. The LED is available in red, green, blue, or white. The battery is replaceable.

The second piece of the SmartLyte "system" is a small magnet.

The battery case rotates through a quarter-turn: full counter-clockwise opens the case for replacing the battery; an eighth turn clockwise locks it to "Off," and another eighth turn puts it on what one could call "Standby."

Once on "Standby," you have a couple of options. You can use it as a keychain-sized flashlight, turning it on or off with the push-button. It's surprisingly bright, and quite convenient to use.

The other option is one we really appreciate. If you attach the flashlight portion to the inside of your toolbox with the Velcro strip provided, and then Velcro the magnet to the lid, within a half-inch or so of the flashlight, you've just installed your "refrigerator light." The light remains off until the light and the magnet are separated. A microprocessor in the light section then turns on the light, and keeps it on until the magnet and the light are again in close proximity. If the lid is left open, keeping the magnet away, the light automatically goes off in about a minute and a half. If you want a manual control, there's always the push-button.

The manufacturer claims that the Smartlyte will run for over 100 hours before you have to change the battery. We tried it, and gave up at 144 hours. We can't imagine that you'd ever have to change the LED itself.

Whole Lot of Shakin'
In the March 2000 issue we reviewed LED flashlights. The Tektite Expedition was considered the Best Buy, but the exciting news, discounting price, was that these lights were long-lived and seemingly impervious to injury. To quote: "The lights were tested by submerging them for a few days in 4' of water and all passed - adequate for most boating uses... We drop-tested the flashlights four times from 6' onto concrete with not a single failure."

We've seen nothing in the intervening three years that has caused us to think we were misrepresenting things. These lights are tough stuff, and they go on and on. In fact we've used the Tektite Mini-Trek for countless hours on the same set of three rechargeable AAA batteries.

Nevertheless, flashlights have long been described as "storage devices for dead batteries," and the longer we live, the more accurate and less amusing this seems. A flashlight that doesn't need batteries is an idea with a very definite appeal.

One of the lights described in the March 2000 article was the NightStar, made by Innovative Technologies. An updated version is now available, and is being sold to the sailing community by Weems & Plath (and to other communities by other purveyors).

The Night Star uses an LED instead of an incandescent bulb. It has a self-contained generator, and stores electricity so that the light doesn't go out as soon as you stop producing electricity (as is true of some of the hand-cranked or squeezable lights we've seen). Instead of a battery, the energy is stored in a capacitor, which can provide storage enough to keep an LED lit for 5-10 minutes.

In the Night Star, the generator consists of a cylindrical magnet, which slides back and forth in a plastic tube through a coil of wire. When you shake the tube end-to-end, an electric current is generated, and the capacitor is charged after 30 seconds worth of shaking. There's virtually no friction in the charging system, because there are repulsive magnets at both ends of the tube, cushioning the ride and encouraging the traveling magnet to head back in the other direction, so that the effort required to shake it is minimal. It's really very clever.

When you switch on the flashlight, you get 5 minutes of bright bluish-white light, which dims over the next 5-10 minutes. If the light beam dims while you're using it, a few shakes will restore brightness.

The Night Star's highly focused beam doesn't provide as much illumination as a conventional flashlight with fresh batteries, but it's a lot brighter than one whose batteries are dead or nearly so. Consider: the LED itself is rated at over 100,000 hours of operation (we didn't test this...) so "bulb" replacement isn't necessary. The capacitor, according to he manufacturer, can be recharged over a million times. The entire flashlight, including the lens, is sealed in a tough Lectern case. The switch is magnetic, so it doesn't require an opening in the case. The light operates nicely over a wide range of temperatures. We tried it at 0° F and 130° F; the manufacturer claims operation between minus 58° F and 140° F.

The Night Star's switch is easy to find - it glows in the dark after even a brief exposure to light. It's waterproof. It doesn't quite float, but it has close to neutral buoyancy and a hole for a lanyard.

There's a strong magnetic field around the Night Star. The manufacturer warns that it should be kept at least two inches away from the chest of anyone who has a pacemaker, and six feet from a compass. We didn't try it with a pacemaker, but did experiment with deviation caused by both the old and the new Night Stars. We didn't observe any compass deflection further than 2-1/2 feet, but that's significant.

This second-edition Night Star has several important advantages. It's lighter, slimmer, and completely sealed. (The older one had a removable lens cap with O-ring seals.) The new light has a wider beam than the old one - 36" at 10 feet vs. 10"?which makes it much easier to use for locating objects. And the new one lists for $44.95, while the old one carried a hefty list price of $79. It would make a good emergency light, if you keep it away from your compass, and it's quite a conversation piece.

Nav Lights on the Horizon
We've been hearing announcements about LED navigation lights for several years , but we haven't seen any until now. Perko and Hella have introduced red and green LED sidelights. LEDs, in theory at least, offer some major advantages for nav lights. The most obvious advantage is lower power consumption. A two-mile red LED nav light will draw about 3 watts, rather than the 15 to 25 watts of a conventional incandescent light. Interestingly, since red LEDs are more efficient than green ones, a green two-mile sidelight will draw about 5 watts - 60% more than its red counterpart.

Unfortunately, none of the LED nav lights available today has been approved for sailboats, which require a wider beam in the vertical plane to take care of normal heeling. But the day will soon come, and when they do arrive, they'll bring several advantages, in addition to the low power draw. First, LEDs don't burn out. They have a service life of 10-20 years, operating 12 hours a day. This means, effectively, that you never have to replace a bulb, and thus you don't need bulb sockets - a major point for corrosion failure. Wires can be permanently attached to the LED, and the lamp assembly can be permanently sealed.

Second, LED lights are less sensitive than incandescent lights to changes in supply voltage. This means that if your boat's charging system fails (or if you're on a sailboat operating under sail alone) you can run longer without losing your nav lights. We've seen LEDs that continued operating without loss of visibility at voltages that would leave an incandescent counterpart dim to the point of invisibility.

Other advantages of LED nav lights are cooler operation (which can lead to smaller enclosures), easier focusing and inherent colors, which can eliminate the dimming effects of colored filters. At this point, there are no white LED nav lights available, but that, too, will be only a matter of time.

The Current Trend
LEDs are showing up as cabin lights, courtesy lights on deck, and in various utility lights where low current consumption is important and maximum illumination isn't. For these applications, the only real drawback to the use of LEDs is their initial cost - presently two to three times the price of a more conventional incandescent equivalent. As LED technology improves, this differential is certain to diminish. In fact much of it is already offset by battery replacement cost.

And the Future
Nobody can predict the effect that LEDs will have on marine lighting in future years. It's not out of line, though, to imagine battery-powered nav lights that require no wiring and will have a battery life of a season or more. Or halyard-mounted battery-powered anchor lights that will require no external wiring.

We'll be testing LED lighting products as they reach the marketplace, probably starting with a full comparison test of nav lights as more of them become available.

 

Contacts-Acolyte Systems, 888/ACOLYTE, www.smartlyte.com.
Hella Marine, 800/247-5924, www.hellausa.com.
Perko, 305/621-7525, www.perko.com.
Weems & Plath, 410/263-6700, www.weemsplath.com.

 

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