LED Evolution Could Spell The End For Bulbs

An anonymous reader writes "USA Today is running a story discussing how LED lamps were unthinkable until the technology cleared a major hurdle just a dozen years ago. Since then, LEDs have evolved quickly and are being adapted for many uses, including pool illumination and reading lights, as evidenced at the Lightfair trade show here this week. More widespread use could lead to big energy savings and a minor revolution in the way we think about lighting."

LEDs do not evolve

[keesh (202812)]

I know that this is true because I read it in the Bible. They did not evolve, they were created by God.

Re:LEDs do not evolve

[sokoban (142301)]

Really? I heard they were created through intelligent design.

Re:LEDs do not evolve

[mysticwhiskey (569750)]

LED's were created from the rib of the original incandescent, don'tcha know? And let's not get into the argument that "Lucifer" means "Bringer of Light", sheesh.

Let there be light! But at what Watt?

But it's warmer..

[Dancin_Santa (265275)]

I guess we are going to start having "illumiphiles" who will try to tell us that the incandescent lightbulbs of yesteryear are somehow "warmer" and that humans can tell the difference between LEDs and vacuum tubes.

You jest, however

[Sycraft-fu (314770)]

Warm and cool are really terms used to describe white light. When you talk about white the question becomes what is it? A blend of all the colours is an elementary explination, but the fact is they aren't all present in equal levels, from any source.

The way that it is talked about, is called colour temperature, and it is spoken of in kelvins. The idea is if you heat a black body radiator to that temperature, that's the kind of white you get. The lower the temperature, the more red in it, the higher the temperature, the more blue.

On most monitors that aren't connected via DVI, you can see colour temperature changes for yourself. In its configuration there should be a colour temperature option, generally with three presets: 5000k, 6500k and 9300k. PLay with them and notice the change. You'll probably find that changing from the one you are used to looks "wrong", either too red or too blue depending on. That's an illusion, however. If you go away for awhile and come back, or just ignore it and keep working, you'll find your eyes adjust and consider that to be white.

With bulbs, it gets more complex because it's not just a function of the temperature of the white, but of it's spectral composition. Most incandesant bulbs have a spectrum that is low on the high frequencies (near violet) and high on the low frequencies (near red). Other lights, like many floursecants, have an uneven spectrum, with peaks all over.

Now ideally what you are shooting for usually is light as close to sunlight as you can get. That's what humans would generally think of as "normal" or "correct" lighting. Easier said than done, of course.

So I don't know what the spectrum for any of the varities of white LEDs looks like, but it is very possible, even likely, that they are different than an incandescant bulb. It may be that they have a generally higher temperature and thus really are cooler, colourwise.

Re:You jest, however

[zippthorne (748122)]

With bulbs, it gets more complex because it's not just a function of the temperature of the white

It is exactly a function of the temperature of the white.. in fact, it's exactly function of the temperature of the filament. (minus a few absorption bands)

The function is given by Planck, Planck's Law of Blackbody Radiation [wolfram.com]

The 'temperature' in your presets is an approximation to the Blackbody spectrum at those temperatures. Warmer and Cooler are, however, reversed when people discuss the whites of pictures etc. I suspect it's because for much of our history light would be either the sun or a fire - and everyone knows a fire is warm. (even though it is much cooler than the sun)

Regardless, given enough complexity, leds could surely approximate a solar spectrum, but it would be very difficult for incandescents to reach the temperature required to actually emit a solar spectrum. (first you have to find a filament material that won't melt/vaporize at solar temperature.)

Re:But it's warmer..

[Anne Thwacks (531696)]

if you're one of those mutants with a fourth color receptor, you'll hate these lights. Reply to This

Yes, I am. You might be too ...

Most people have another type of receptor, called a rod, which is not colour sensitive, unlike the three kinds of cones which are colour sensitive. However, my rods have a much wide spectral response than the normally accepted colour range of white light. I have known for a long time that light without significant ultraviolet content makes it hard for me to accurately resolve edges. I find technical drawing very difficult by incandescent light. Others may be the same too.

Remember 10% of men lack one kind of cone, and are partly colour blind. A lot more lack fashion sense, but you can't blame that on LEDs

Hmm, don't think so.

[cosmol (143886)]

Yes, I am. You might be too ...

I doubt it, at least not the kind of person the grandparent is referring to. If you are you should be calling a research lab and asking for bids to be a guinea pig. Tetrachromats are extremely rare.

This hypothesis sounds more likely (from http://www.physics.utoledo.edu/~lsa/_color/18_reti na.htm [utoledo.edu] Rods and all three cone types readily absorb ultraviolet radiation, photons of which are energetic enough to damage these delicate cells. The reason we cannot see in the UV is because the eye lens is opaque in that wavelength range. In addition, the cells in a region called the macula surounding and including the fovea contain a yellow pigment that further prevents short wave radiation from reaching the photo-receptors. Some people with less of this yellow pigment and those who have had their lenses replaced with plastic inserts can see further into the UV than normal people can.

Re:But it's warmer..

[Avian visitor (257765)]

In fact, there is a major difference, even in theory. A white LED light is produced by combining red, green, and blue LEDs. If you were to take this white light and run it through a prism, you would not see it defract into a rainbow. Instead, you'd see a red beam, a green beam, and a blue beam.

Did you actually did this experiment? Modern white LEDs have a single light emitting junction that mostly emitts light in the blue part of the spectrum. This junction is then covered with a phosphor-like coating that converts a narrow band of wavelengths to a broad band that you see as white light. This means that white LEDs have a continuous spectrum, much like the light bulbs.

Re:But it's warmer..

[by Anonymous Coward]

I'm not the one you replied to, but I did look up the spectrum -- it's shown here [att.net]. It's definitely more spread out than I would have guessed, but it doesn't look like an incandescent [mis.net],

Re:But it's warmer..

[Jah-Wren Ryel (80510)]

In fact, there is a major difference, even in theory. A white LED light is produced by combining red, green, and blue LEDs.

bah
lone
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All modern white LEDs are single indium gallium emitters in the blue to uv range that are coated with a phosphor somewhat like that in a flourescent lamp. The energy from the blue led excites the phosphor into producing a multitude of wavelengths which we perceive as "white." Generally, the thicker the phosporus coating, the warmer the light (lower color temperature). The output is definitely a lot richer than three simple RGB wavelengths.

Even perfect RGB cannot cover all colours

[Dogtanian (588974)]

There are also more subtle issues at work with the 'R/G/B mixing' approach to colour generation. You can read more about them here [slashdot.org].

To summarise; consider that the red, green and blue receptors are sensitive to a *range* of colours; the sensitivity curve for each receptor is roughly bell-shaped, peaking on red, green or blue light. There is also some overlap between the red and green sensitivity curves, and between green and blue (not red and blue IIRC).

This is of course essential. Sensitivity narrowly focused on R, G or B would leave us unable to see intermediate colours (e.g. yellow!).
Reasonable overlap is necessary, or
(A) there would be certain intermediate frequencies that were not covered sufficiently by either receptor (e.g. certain shades of yellow in the valley between the red and green curves would be very hard to see), and
(B) Colours would be quantised into 'red group', 'green group', or 'blue group' (think about it...)

Because of the (necessary) sensitivity-curve overlap, the green receptor is slightly sensitive to red light, and so on. Where is this leading, you ask?

True cyan has a frequency between blue and green. This is within the sensitivity range of both blue and green receptors; the brain can use the 'ratio' to figure out that it's looking at cyan. But true cyan is (to all intents and purposes) outside the red receptors' range, so the red receptor is not stimulated.

Simulated cyan is made up of green and blue light. This stimulates the green and blue receptors in the same ratio as true cyan would, so in theory looks just like the real thing. However, the red receptor is also slightly sensitive to green light; thus, unlike with real cyan, the RGB-mixed version also stimulates the red receptor.

This is (supposedly) what makes certain RGB-generated colours less convincing (hence the linked story above).

This isn't even counting the fact that our colour receptors aren't exactly R, G and B, and therefore to simulate certain colours using RGB is impossible, as it requires one or more components to be negative. (If the receptors were exactly R, G and B, that would not be the case).

Re:But it's warmer..

[Jace of Fuse! (72042)]

Tetrachromats [wikipedia.org]

It isn't science-fiction.

To simply, some women are blessed with color receptors that allow them to see a color between the green and red wavelengths. Their idea of the world and it's colors is much more vivid than most people's.

It's almost certain that all tetrachromats would have to be women.

girls and color sense

[zogger (617870)]

I have an interestiung anecdotal from ye olden days. Way back when, I had a girlfriend who was an artist, and going to an art school. They had a black tie affair for the students faculty and parents,so we went. Hey, free food and champers! Me in a tux, too funny! Anyway, one of the students mom's there lost a diamond out of a setting, fell on the floor someplace. So here's a couple dozen people in gowns and tuxes all bent over squinting at the floor. We saw it, went over to ask "what's up"? Got told about the loose stone, girlfriend glanced down, immediately spotted it, went over and picked it up, like one second. She saw it from her extraordinary ability to see colors. She had been tested in the school and won, ran 10,000 colors in ROYGBIV sequence not missing a single shade, the only student to get all of them correct.

Re:But it's warmer..

[ComputerizedYoga (466024)]

I'm in the US, I perceive flicker on 70hz and below refresh rate monitors, and on some old fluorescent lighting (but I've gotten used to it and can deal with it). But the thing is, a properly ballasted fluorescent lamp doesn't flicker at 50 or 60 hz. It flickers at 100 or 120 -- the ballast doubles the frequency from the mains frequency. Which is faster than most people perceive. However, solid state ballasts go WAY faster than that ... Wikipedia's entry on ballasts [wikipedia.org] is pretty informative.

So, pretty much, newer better lamps shouldn't flicker perceptibly. I know my CFL's don't, and ever since we got the ballasts replaced the tubes at work don't either. But I guess YMMV.

Re:But it's warmer..

[unitron (5733)]

The ballast does nothing to the frequency, it just limits current by acting as a choke coil. It's an inductive load in series with the path through the ionized gas inside the tube. 60 Hertz means 60 cycles per second which means 60 positive peaks per second and 60 negative peaks per second which means 120 total peaks per second. Another way of looking at it is that there are 2 zero crossings per cycle, therefore 120 zero crossings per second.

Light bulbs, incandescent or fluorescent, running off of house current "flash" 120 times per second.

Re:But it's warmer..

[UncleFluffy (164860)]

When I went to the US the flicker from flourescent tubes drove me insane (in the UK they flicker at 50Hz, what is it in the states?).

60Hz in the US, so for single tube installations you should see less flicker. However, in the UK, the Health and Safety regulations for offices require that multi-tube installations have the tubes fed from different phases of the supply. So a typical office setup with three tubes, one on each phase, gives you almost no noticable flicker.

Certainly

[Dorsai65 (804760)]

an illuminating article...

I like the color-mixing aspect..

[jcr (53032)]

I'd buy them for that capability alone.

I wonder when we might see LEDs with enough brightess to serve as a projector lamp?

-jcr

Re:I like the color-mixing aspect..

[metlin (258108)]

Actually, rock climbers & spelunkers who do lots of caving have been using LED based headlamps [rei.com] for a while now.

They have excellent focus and can illuminate pretty darned well, projecting the light to a good distance as well as a very effecient battery usage.

I do not even remember the last time I used a lightbulb based headlamp.

So, to answer your question - current LEDs can probably do that already.

In other news...

[Nichotin (794369)]

the lightbulb industry lobbies the congress to ban LED technology that will ruin the market for lightbulbs.

Is this true?

[by Anonymous Coward]

For starters: LEDs aren't as efficient as many people seem to think, iirc they're a bit more efficient than normal lightbulbs, but TL-lamps and other gas-ionisation-type lamps are still way more efficient. Secondly: While LEDs may emit light for 6 years continuously, they have a certain half-life that's way shorter than that; at the end of the 6-year life span, the leds probably only emit 1/4th of what they did when they were new.

Did you read the article?

[egosum (758988)]

Just this week, researchers at the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y., said they had boosted the light output per watt of a white LED to almost six times that of an incandescent light bulb, beating even a compact fluorescent bulb in efficiency.

LEDs are definitely becoming more powerful

[Motherfucking Shit (636021)]

I used to think of LEDs as cute little indicator lights. A nice tiny, soft green LED light tells me that my monitor is on, or blinkenlights let me know that packets are flowing through my router. An orange LED might alert me to standby mode on a device. None of them were really all that visible unless I was looking directly at them, and certainly none put out any ambient light.

Then I got my newest computer. This thing has a single blue LED backlighting an area the size of a dime, behind the power button on the case. When I turn off all the lights, after a minute or so of my eyes adapting, the single blue LED gives off enough light to illuminate half the room. For the first week or so, I had trouble getting to sleep because of the light... From one blue LED.

As the technology gets better I can imagine LED lamps coming in vogue. I seriously doubt that the end of the bulb will come anytime soon, though. Probably not in my lifetime.

Re:LEDs are definitely becoming more powerful

[ShaunC (203807)]

Ugh. Blue LEDs are, without a doubt, the most annoying new fad in consumer gadgetry. The problem is they're suddenly showing up in everything, replacing green LEDs as the default.

A couple of months ago I bought an all-in-one VCR/DVD deck that plays and records to both tapes and DVDs. Hell of a convenient unit, except that when you power this puppy up, it has four blue LEDs on its face. One for "power on," one for "disc in," one for "tape in," and one down by the controls which I guess is there for the hell of it. The clock is a matched-color blue LCD display.

The blue LEDs are absolute distractions. Even during the day, with the lights on or the sun coming in the windows, my eyes want to focus on the blue lights instead of on the TV screen. I'm not sure whether it's the intensity of the LEDs, or the fact that the eyes are more sensitive to blue light. Probably some combination of both - they chose blue strobes on cop cars for a reason I guess - but whatever, it's damned annoying.

Give me a soft green LED any day. Enough with these bright blue ones.

Not new

[The Tyro (247333)]

This is no surprise... it's been this way in flashlights (hand torches, to you brits) for a while, particularly the higher-end ones and those designed for specialty applications.

As an example, some of the weapon-mounted lights being used by the military are also going to LEDs. Some of the regular incandescent bulbs just don't hold up as well to the punishing recoil of most weapons... you were forever changing bulbs. The higher end incandescent lights like the Sure-Fire lights [surefire.com] could take the shock, but forget mounting anything like a mag-lite [maglite.com] on a weapon.

Best thing about them: they're easy on the batteries. Batteries are heavy, and there's nothing worse than having to carry too many spares. Every ounce counts when you're carrying it on your back.

Re:Not new

[by Anonymous Coward]

"but forget mounting anything like a mag-lite on a weapon"

YOU SEE!!! Doom 3 had it right all along!

Re:Not new

[a whoabot (706122)]

Your sig reminds me of a conversation two people I knew/know had.

One was just a regular guy. One was a girl that knew taekwondo and I guess was pretty good at it. He would bug her that even though she knew a deadly art of self defense he could still beat her, just because she was a girl. This would tick her off and eventually it escalated one day into seriously discussing setting up a "no holds barred" fight between the two.

At one point of the discussion he was like, "Wait wait wait wait wait. If she gives me a compound fracture, am I allowed to stab her with my exposed bone?"

It only made it funnier that he was serious.

They never got to fighting because eventually she became convinced of his psychosis when he started agressively arguing that even biting and the gouging of eyes were not be barred:

"Well, it just so happens that I think my stomach for, and skill in, gouging eyes are my greatest abilities. If I'm barred from such an act then I can't imagine how this fight would not be a handicap fight in your favour. It's tying my hands behind my back."

Re:Not new

[theonetruekeebler (60888)]

I have a Petzl 3 LED headlamp , the size of half a golf ball, with a retracting headband. I keep it in my motorcycle tank bag---and use to hike to the the deer stand. Incredibly light, good for reading in a tent, for roadside map consultation (back before I invested in a GPS). Three LEDs, sips battery power, a good, natural color of light.

The absolute best use for new-generation LEDs I have seen is for brake lights. Many high-end cars, and even some delivery trucks, use LEDs now, and the advantages are clear: they are damned bright, highly directional, don't burn out, and best of all, they reach full brightness a tenth of a second faster than an incandescent bulb. That may not sound like much, but at 60MPH, 0.1 second is 8.8 feet extra feet for the car behind you to start reacting (100km/h ==> 2.8m in 0.1s). I have blinky LEDs on my motorcycle and they solve all sorts of problems with tailgaters.

Not Convinced

[Paris The Pirate (799954)]

Not convinced I'd want that style of lighting everywhere around my house as it stands it'd be like living in a large supermarket.

I'd have to invest in some hardcore lift music to complete the 'still out shopping' effect. And perhaps pay a young relative to scream and be slapped periodically in the middle distance.

Marketing is pushing it.

[by Anonymous Coward]

"On a very hot day you might want blue light to cool it down a bit."

And if street noise is distracting you, a green LED will quiet that right down.

Need to fit normal lamp-sockets.

[jdonnis (115371)]

I think one of the main issues with LED lights is the incompatibility with existing lamps.

Sure you buy new lamps every once in a while, but a real breakthrough will come when you can get LED 'bulbs' that fit in a normal 220/110V socket on a normal lamp.

The same thing happened with those energy-saving bulbs, it seems they only really took off (at least here in Denmark where electricity is expensive) when they became available in versions that looked like normal bulbs and fit most lamps.

Another example is the wire spot halogen lights, once they became available in 220/110V versions they took off. Nobody seemed to want those bulky 220->12V transformers around.

Re:Need to fit normal lamp-sockets.

[zakezuke (229119)]

Sure you buy new lamps every once in a while, but a real breakthrough will come when you can get LED 'bulbs' that fit in a normal 220/110V socket on a normal lamp.

They've been out for some time.

http://store.sundancesolar.com/ledlibu12acl.html
http://www.smarthomepro.com/97314.html
http://w ww.ccrane.com/120-volt-led-light-bulb.aspx

The technique is simple. Use a rectifier to convert AC to DC, and use enough LEDs in series and glue them all together. Sure if one LED burns out you loose a whole series, but don't expect that for a few years.

Whether you'd actually want to own one is a different story.

Future of Lighting Design

[maino82 (851720)]

I'm a lighting and electrical systems design student and a lot of talk has been going on about LEDs these past few years. One thing people seem really excited about is the color mixing capabilities. While it may be true that a single white LED might not provide the kind of white you want, you can mix RGB to any color temperature of white you want (from a warmer incandescent color to the cooler color of the sun). I went to Lightfair a few years ago and saw an LED parking lot light that had an array of various color LEDs that mixed to white on the workplane, and an added bonus was that because there were so many colors in the array, the color rending was amazing.

Unfortunately, like the article says, the first cost is still prohibitive in a lot of cases, although the savings in energy would seem to make it worthwhile. LEDs also tend to get very, very hot in large quantities if they're used for a long period of time, so air circulation is a common problem as well.

Hopefully some of you computer engineers and programers can come up with a cheap way to produce and control LED arrays so I can start using them in practice! Building owners would be extremely happy if power consumption in buildings would go down significantly and if they had the ability to control the color and brightness (they are easily and cheaply dimmable, unlike flourescents) of any room individually.

Hold On Now

[Rie Beam (632299)]

This article contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things (and light sources). This material should be approached with an open mind, studied carefully, and critically considered.

Hrm...

[Duncan3 (10537)]

So which way am I better off? Just using lower wattage "classic" lightbulbs, or with dozens of 120V AC->5V DC converters wasting energy everywhere.

The adapter for my iBook puts out more heat then the iBook. More of the heat from my AMD64 is from the power supply vs. the CPU and Gfx.

Almost nothing I own needs over 12V anymore. When will I be able to just have one nice 120->12V spaceheater and run everything else in the room off 12V?

Re:Hrm...

[Matthias Wiesmann (221411)]

Quite a few years ago, they built a 'ecological house' in Switzerland (sorry I can't seem to be able to find a link). One of the interesting aspects of this house was that it had twin electrical wiring, one 220V AC circuit and one one 12V DC circuit. The 12V circuit was powered by batteries and solar panels, while the 220V circuit was powered by the grid. The point was that converting from 220V to 12 is not very efficient, and solar panels are better suited for producing 12 V DC.

At that time, LED based illumination was not possible. Now if light can be produced efficiently from 12V the list of devices that really need 220V is not that large: mostly cleaning machines and kitchen appliances. Of course rewiring houses is the real problem...

Most white LEDs work using a different method

[Andy Mitchell (780458)]

The article says:

They haven't been used as sources of illumination because they, for a long time, could not produce white light -- only red, green and yellow. Nichia Chemical of Japan changed that in 1993 when it started producing blue LEDs, which combined with red and green produce white light, opening up a whole new field for the technology.

This is certainly one way to produce a white LED but it is not the common method today. Most white LEDs use a phosphor to convert a blue or ultraviolet LED into a white one. A quick google found the following page that talks about this in more detail:

http://www.marktechopto.com/engineering/white.cfm [marktechopto.com]

I would speculate that for normal home lighting using a phosphor will give better results as:

• Using separate red, green, and blue emitters increases complexity. Different colour LEDs are often made using different semiconductors.
• Using 3 separate LEDs will produce a light that looks white, however as LEDs only produce a very narrow range of frequencies (determined by the band gap as I recall) this may cause some colours to look a bit off. Fluorescent lighting also works by converting UV to visible light and can produce an excellent reproduction of daylight. Providing of course you buy the right tube that uses the approprite magic combination of phosphors.

Drag Racing

[Skraut (545247)]

The drag racing industry has moved from incadecant to LED lights for the starting "Christmas Tree"

3 generations of humor obsoleted...

[theonetruekeebler (60888)]

What are we going to do for lightbulb jokes? LEDs just don't work here:

Q: "How many Californians does it take to resolder an LED?"
A: "Californians don't resolder in LEDs. They resolder in hot tubs."

One can only pray for a GFI failure.

Q: "How many trailer trash rednecks does it take to resolder an LED?"
A: "They still use lightbulbs!"

Okay, that one's still okay.

21st Century Slowly Arriving

[DumbSwede (521261)]

Conventional incandescent bulbs are cheap and incandescent bulb factories churn out billions per year. They won't disappear overnight, but disappear they will eventually when we reach some tipping point in price. Trouble is all those old factories will continue to churn out bulbs until the profit margin is some fraction of a cent above raw material price. You can get 4 conventional bulbs for 99 cents today when they are on sale, so I think $5-$10 Dollar will be the magic tipping point for LED bulbs given the energy savings and lifetime for home use and $20-$40 for commercial use. When this happens incandescent will probably drop to 10 or 15 cents a pop for a while, basically burning off inventory at cost. Once LEDs are 60-80 percent of indoor illumination, conventional bulbs will slowly start to climb in price as old bulb factories close their doors leaving fewer suppliers.

It will be some years before we reach this tipping point in price however as current costs are about $100-$200 a bulb for 65watt equivalent LED bulbs [ledtronics.com]

10 years after most bulbs are LED conventional bulbs will seem anachronistic and stone age. One of the few things in the last 100 years to just be out and out replaced by a new technology. Granted we have lots of bright shining new things in our modern world, but they general have been added to what we already have or evolved slowly from what came before. The switch to transistors from tubes is about the only other thing that comes to mind where this has happened, and perhaps this should just be seen as one of the last hold outs of filaments in tube to be displaced by solid state. All that is left to go are CRTs and this too will happen relatively soon.

In need of a similar revolution: Cars that run without gas - this is a hard one, but we are finally starting to make some progress; Energy production from other than Oil, Gas, Coal, and Uranium. Fusion is about the only way to go here, but it isn't doable at any price today. None of the other energy alternatives have a chance of displacing the big 3 fossil fuels or remaining conventional nuclear plants; Getting to Space without conventional rocket technology. Do all these things and we will have finally arrived in the 21 Century.

Already used in stoplights...

[xxxJonBoyxxx (565205)]

I think all the new stoplights in town are LED stoplights. Most of the brakelights on trucks around town are too. Did this story fall through a time-rift from seven years ago?

LED flashlights were my latest toy. . .

[Fantastic Lad (198284)]

We had a three day power outage over the winter, and a few things became apparent.

Without power, many people seem to turn into hopeless wrecks.

People burn their entire supply of toxic paraffin candles in about two days, (if they have them), they run out of food, and they start to freeze. If the power had gone out for more than a couple of weeks without emergency help or without a shift in how people arranged their lives, I think we'd have seen some serious Darwinism in effect. --Luckily, when people get motivated, they also tend to be quite resilient; two weeks without power is like getting kicked out of bed. "Okaaay. Fine. I'll go do something about the situation rather than gripe and eat all the easy food."

But anyway. . ,

I found myself hurting for a decent lighting solution. With no power, and time to kill, people like to read and they play social games like D&D! Except, without reliable lighting, these things are possible only during the daylight hours, (which in the winter time are in shorter supply, plus if you have your windows covered up with blankets for extra warmth, the lighting situation isn't so good). --And a room filled with paraffin wax smoke gets toxic and trippy in a bad way after about half an hour. Yuck. --Bees wax burns non-toxic and smells really nice, but those kind of candles are usually expensive and in short supply.

Enter the LED flashlight! After the power out-age I ordered a 'Lightwave 4000'. It runs on 3 D-cells, and you can expect about 900 hours of solid run time. (2000 hours, if you believe the packaging, which I don't.) Still, 900 hours is 37.5 days of solid 'On.' Cut that in half for night time use only, and you're looking at over two months of lighting on 3 batteries. That's 9 batteries to last you all through winter. Not bad!

Then just toss in a few of those small, $10 Dorcy single-LED lights which run on AAA cells for 200 hours or so. --Keep those in supply, and you're fine. --For a social setting, just set up a Bee's wax candle to throw a little nice color, and you're surviving in style.

Wrap up in blankets, get an alcohol burner for teas and soups, or better, a wood stove, and you're laughing. Life is fun when you're prepared!

-FL

Re:Bought some today!

[Adult film producer (866485)]

I've heard of this before, having the odd bluish tone to it, maybe this will help.. I dont know, I dont have a lot experience with leds.

"Q: I want to use white LEDs for photographing or videotaping insects, plants, electronic parts, and other close-up subjects, but all of the white LEDs I've tried have this blue circle in them that ruins the picture. Any suggestions?

A: Try using Nichia's rectangular white model, NSPWF50S. This LED has a very wide, even beam that doesn't have that obnoxious blue ring

Re:Bought some today!

[Yokaze (70883)]

I thought white LEDs are usually blue LEDs, which are coated with a scintillator, which converts parts of the blue light to yellow. Wikipedia seems to support my impression [wikipedia.org].

Regarding efficiency, I refer once more to Wikipedia: "In 2002, 5-watt LEDs were available with efficiencies of 18-22 lumens per watt. [...] In September 2003 a new type of blue LED was demonstrated by the company Cree, Inc. to have 35% efficiency at 20 mA. This produced a commercially packaged white light having 65 lumens per watt at 20 mA, [...]".

Re:Bought some today!

[squidinkcalligraphy (558677)]

The first white LEDs were an RGB mix to produce white; now they use blue + scintillator, probably producing the blue circle. I'd imagine with better diffusion methods this could be overcome.

Anyone notice that a blue LED has a 'haze' around it when looked at from the side (i.e. not looking at where the light comes out)? This is even more pronounced in purple LEDs (which are still expensive and not ready for commercial use). Wonder if this haze has anything to do with the blue circle appearing on recordings...

Re:Bought some today!

[ebh (116526)]

Arrays that mix red, green and blue LEDs can produce any color of the rainbow.

Mostly true. When viewed directly, the eye perceives any color in the color space defined by the three LED colors. But the actual light is still trichromatic, so it won't light up the objects in the room the way you expect them to. A beautiful yellow light might make an object of that same beautiful yellow look like a dingy brown, becuse there's no actual light of that color to reflect off the object.

Try it yourself: Tonight, set your screen background to various colors, turn off the other lights in the room, and see what things look like when lit only by the monitor. The effect isn't as pronounced, but it's still observable.

Re:Bought some today!

[by Anonymous Coward]

Try it yourself: Tonight, set your screen background to various colors, turn off the other lights in the room, and see what things look like when lit only by the monitor.

What other lights?

Re:50000 hours lifetime?

[dabigpaybackski (772131)]

Dude, six years is forever in the tech world. Six years is long enough for everybody to want to replace whatever they have with something that is both cheaper and vastly better, even LEDs.

Re:Legal on bicycles?

[glesga_kiss (596639)]

Some say that bikes in the UK can only be ridden at night with 'incandescent bulb' lights, and that LEDs are against the law.

Not entirely true. LED lights are fully legal if they don't flash, that's all there is to it. There are laws that predate LEDs on having flashing lights on vehicles. This was a minor news article when flashers first appeared, but many prominent figures came out and said they would pay for any fines should someone get in bother for having something that clearly improved their safety.

I don't think anyone has actually been prosecuted for it. So, what we are basically seeing what is a new "stupid law" that never gets enforced. Kinda like the one that states that taxi drivers must always carry a bale of hay, and that they can legally urinate in a public street provided they pee on their back wheel!