Jan 3, 2007

LEDs Mean The Light Bulb Will Soon Be A Museum Piece

LEDs mean the light bulb will soon be a museum piece

Cyberspeak- USA Today
Andrew Kantor

There's an old puzzle that goes like this: You're standing outside of a room with a tightly closed door. There are three light switches in front of you and three lamps in the room. You want to know which switch turns on which light in the room, but you're only allowed to open the door once. How do you do it?
The puzzle is solvable because today's light bulb technology is old and wasteful. Your typical incandescent bulb uses a ton of energy making heat instead of light, something you've probably demonstrated countless times by attempting to unscrew a bulb that's just been turned off. Ouch.

The incandescent bulb was invented by Heinrich Goebel in 1854. (Thomas Edison's didn't come around until 1879 and was based on a patent he bought from two other guys, for those of you who keep track of these things.) It works by heating a filament, usually made of tungsten, to around 4,000 degrees Fahrenheit—hot enough to glow. Those of you with electric stoves are familiar with the concept; the coils of the stove glow red hot. The filament in a light bulb glows white hot, but the argon gas in the bulb keeps it from burning up. The result is a cheap way to make light. Unfortunately it's a wasteful way, with all that energy going into making heat instead of light. Nor is it a terribly long-lasting way, and those tungsten filaments, which may be only .01-inch thick, have a tendency to break; how else would we have so many light-bulb jokes?

Halogen bulbs are a bit better. They embed a special filament inside a quartz "envelope" to get a strong, more efficient, longer-lasting light — like, for example, your car's headlights which probably don't need to be changed all that often. (They also get a lot hotter than standard bulbs.)

Fluorescent lights are more efficient than standard or halogen bulbs — you might have noticed they don't get terribly hot — but they also take a while to get up to full brightness, they get dim over time, and they aren't particularly sturdy.


When we say light is white, we mean that it closely matches the light from the sun. Using a concept called black body radiation, which I will not go into here, you can rate the color of light in terms of temperature. Sunlight's color is about 5400 degrees Kelvin.
The white light in our homes and offices isn't really white. Incandescent bulbs radiate around 2600 to 3000 degrees K. They're on the orange side, which you can easily demonstrate by taking a photo indoors that's lit only by some incandescent bulbs. It'll be very orange (unless you're using a digital camera that corrects the "white balance").

Typical office fluorescent lights are in the 3000-3500 degree range. They're greenish; try taking a photo under one to see. Many hardware and photography stores sell "daylight" fluorescent bulbs that are rated 5500 or 6000 degrees, and closely match the sun for whiteness.

But a new kind of lighting has been making its way into the world. You've probably already noticed it: LEDs, or light-emitting diodes, taking the place of light bulbs.

Unlike incandescent bulbs, which generate light essentially by heating a filament till it glows, LEDs are electronic components based on semiconductors, which have some interesting properties that happen to generate light when a current is passed through them. They've got no filament to burn out, and the electronics are encased in a tough plastic bulb. Today's LEDs last a long time. (If you want the full details on how LEDs generate light, check out How Stuff Works.)

Usable LEDs have been around since the 1960s. The early ones were weak and useful only as indicator lights (the way many still are). Reasonably bright red LEDs were developed in the 1970s; you probably remember the first digital watches came out around then using red LEDs to show the time.

LEDs are often used in traffic lights. Look for the dots.

New semiconductor materials were developed in the '80s and LEDs got cheaper and much, much brighter. They were made in red, yellow, and green. In the early 1990s blue LEDs were finally developed, and a few years later bright blue ones came out. Then, by adding some chemicals to a blue LED chip, engineers were able to create white LEDs. (In fact, they've been able to create LEDs of just about any color.)

I said earlier that you've probably noticed LED lamps. You just may not have realized it. Many traffic lights have been converted to LED lamps, and so have a lot of car and truck taillights. You can often spot them because LED-based lights typically are made up of a number of smaller lamps clumped together (see the photo). Next time you're behind a semi, look at the taillights. There's a good chance they're LEDs.

White LEDs are available in consumer products. Flashlights are one popular use because LEDs are tougher, longer lasting, and less power hungry than a typical bulb.

When my 17-month-old son discovered flashlights, I gave him a cheap one I got at a trade show. It was clearly the Coolest Thing Ever. As most parents know, once your offspring hit about eight months old it's time to buy stock in Duracell; they sell those 24-packs for a reason. So it was with Sam, as he has yet to discover the Off switch. So I swapped lights with him, and gave him an LED-based flashlight instead. It's water- and drool-proof, just about unbreakable, lasts a heck of a lot longer, and the bulb won't burn out for a long time.

Mine (rather, Sam's) is Princeton Tec's "Attitude" and goes for about $22, but you can find lots of others in sporting goods stores and places like The LED Light.com. Mini Maglite users can buy a converter kit to upgrade their flashlight to LEDs, and those of you with a lot of disposable income can even buy LED replacements for regular light bulbs. At 89 bucks for the equivalent of a 15-watt bulb, it's only for those really hard to reach places.


Americans take their lighting seriously, as anyone who's ever tried to use a telescope near a city knows. We spend about $50 billion a year just on the electricity for our lights. To put that in perspective, $50 billion would buy more than 1.6 billion elementary school textbooks. Think about that next time you leave your porch light on.

Of course, white LEDs are still relatively new and prices will drop tremendously in the coming years. It won't be long before light-bulb jokes are a thing of the past, and we're spending a lot less money to illuminate our homes and businesses. LEDs can put out a more natural glow than either incandescent or fluorescent bulbs, so we're also getting a better light.

Not too far down the pike are a cousin of today's LED: organic light-emitting diodes, or OLEDs. You're going to be hearing a lot about those soon. But not today.

(By the way, the solution to the puzzle: Turn on the first switch for a few minutes. Turn it off. Turn on the second light. Open the door and go into the room. The first switch controls the bulb that's warm, the second switch controls the bulb that's lit, and the third switch controls the bulb that's off.)

Andrew Kantor is a technology writer, pundit, and know-it-all living in Columbus, Ohio; he's also a former editor for PC Magazine and Internet World. Read more of his work at kantor.com. His column appears Fridays at USATODAY.com.

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