The End Of The Light Bulb?

sdmonroe wrote to mention an MSNBC article discussing the likely eventual replacement of common light bulbs by LEDs. That replacement is likely to come quicker thanks to an accidental discovery announced this week. From the article: "Michael Bowers, a graduate student at Vanderbilt University, was just trying to make really small quantum dots, which are crystals generally only a few nanometers big. ... When you shine a light on quantum dots or apply electricity to them, they react by producing their own light, normally a bright, vibrant color. But when Bowers shined a laser on his batch of dots, something unexpected happened. 'I was surprised when a white glow covered the table,' Bowers said. 'The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.'"

Something new for moths?

[xanadu113 (657977)]

Something new for moths to fly in to?

well, likely not.

[way2trivial (601132)]

at my workplace, a hotel on the beach.

We had for many years yellow colored standard bulbs, as they don't attract bugs.

we started replacement with yello fluro twist bulbs, to save on electricity and replacement costs.

in research, it turns out, we can use white fluro-- as they only emit light in a very narrow spectrum of white light, unlike an ordinary filament bulb.. and the range they do emit light on, suitable for humans, does not attract bugs.

I'd guess these low power led lights also emit white light on a very narrow band....

Re:well, likely not.

[farquharsoncraig (711336)]

http://exploration.vanderbilt.edu/images/news/arti cle_main/quantumdot_led_5.jpg [vanderbilt.edu]

LEDs vs Dots

[maxwells_deamon (221474)]

I think what they are trying to say is that the new light bulb will be something like this:

Single freqeuncy LED light (high effiency but ugly/annoying color) will be used to generate the initial light. This will hit a thin film of dots which will reradiate the light as white light that makes humans happy.

Saves costs as you only need one LED and multiple LEDs do not really match sunlight anyway.

Of course the article claims no heat is produced! :-)

Re:well, likely not.

[way2trivial (601132)]

alright, it has the white light, and none of the 'rest' of the spectrum, which apparently attracts bugs.
but yes, a narrow spectrum of white, I found a good picture here
http://www.truesun.com/Litetube.htm [truesun.com]

roll down to where there are three bulb types listed.

note the incandescent bulb rolls up from blue to red
note the fluroscent has three spikes of blue, yellow and red

the missing bits, including the missing UV and IR at the ends, include whatever attract bugs.

so yes- a narrow band of white light......

no, it is NOT a contradiciton

[way2trivial (601132)]

I can make white light by emitting everything from UV to IR

or I can combine a 3 beams each of a very precise wavelength of red green and blue, and end up with WHITE.

a narrow spectrum of white.
very perception based.. I may see it as pure white, you may be more sensitive to one of the three, and therefore see it as green or blue or red tinged.

a bug may not see it at all.

Re:no, it is NOT a contradiciton

[dgatwood (11270)]

That's not true. At any brightness level, an equal combination of red, green, and blue will be perceived as white. It doesn't have to be "an overbrightness".

There are an infinte number of white light spectra. You seem to be defining it very narrowly as an incandescent white, but that is not the standard definition of the term.

Perhaps, but...

[msauve (701917)]

that only applies to the perception of the emitted light itself. However, objects illuminated by such a light source may appear to be significantly different in color than they would under a broad spectrum white light, since they may reflect light in narrow bands not matching those of the source.

Combining narrow spectrum RGB sources can work to produce whatever perceived color you want, as in a display. It does not work for all reflective lighting needs, so a solid state broad spectrum source still fills a need.

maybe, but here's a way better article

[farquharsoncraig (711336)]

http://www.google.com/search?q=Michael+Bowers+Vand erbilt+University [google.com]

http://exploration.vanderbilt.edu/news/news_quantu mdot_led.htm [vanderbilt.edu]

A return to white street light

[Simonetta (207550)]

One of the unfortunate side effects of the 1970s was the replacement of all the soft white street light bulbs with orange-yellow sodium vapor bulbs. Sodium vapor bulbs use less energy. All the night lighting went from soothing soft white to light orange. Orange, as you may recall, is the color of madness.

    I've never liked yellow-orange streetlights. It's one of those things that never gets noticed. But the difference can be really appreciated if you go to a wealthy neighborhood where white light bulbs are still used. However, unless you're older and white, it's going to be a short time before the 'security guards' drive up with tasers and ask you what you're doing. If you're truthful and tell them that 'you're digging the cool white groove of the light, baby', then they will do what all mercenaries do when encountering a civilian harmlessly enjoying life, they will kidnap and assault you for their amusement.

    Anyway, a return to soft white lighting in the night will be most welcome.

LED lights

[totallygeek (263191)]

I have been impressed with the LED lights over florescent or incandescent. The subdued lighting is fine with me and the energy consumption / bulb longevity is the best part. When my wife and I move (build a house), we will go 100% LED.

"LEDs don't emit heat"

[Tau Zero (75868)]

I wonder how many people are going to read this in the article and assume that LEDs are not just more efficient than other types of lamp, but 100% efficient?

(I hate scientifically-illiterate journalists.)

This brings up an important question

[by Anonymous Coward]

How many cats does it take to change a quantum dot?

Re:This brings up an important question

[Geoffreyerffoeg (729040)]

Two, and you don't know which one will actually change the dot until the light turns back on.

It's about damn time!

[Mysticalfruit (533341)]

Considering that the average lightbulb creates more heat than light, this is great!

Re:It's about damn time!

[winkydink (650484)]

Considering that the average lightbulb creates more heat than light...

Kind of like most slashdotters!

Re:It's about damn time!

[joostje (126457)]

Considering that the average lightbulb creates more heat than light, this is great!
As lightbulbs create about 95% to 98% heat (the rest is light), and modern LEDs about 85% to 96% heat, the LEDs still create more heat than light.

reference [wikipedia.org]

Re:It's about damn time!

[syukton (256348)]

Something interesting and useful to know is that the other reply you received to your post is totally incorrect.

First, LEDs are current driven, not voltage driven. The voltage difference between + and - determines the amount of current the device will consume, but if you can regulate the current you can run the device at 100V no sweat. You will of course need to dissipate any additional heat (usually in the device you're using to do the current limiting, sometimes a resistor, sometimes a more exotic circuit) created, but the very important thing to understand about LEDs is that their current absolutely determines their light output after you surpass a certain threshold voltage.

The relationship between the +/- voltage difference and the amount of current consumed is not the same for every kind of LED. LEDs require different chemistry in order to produce different colors, and this makes them have differing performance characteristics.

And another thing to consider is how the LEDs are packaged. Some 8mm packages have 4 chips inside and their rated light output is measured at a regulated input current of 80mA and not 20mA as for most single-chip devices. Also, some blue devices consume 30mA while reds only consume 20mA. Again, this depends on the chemistry. Now, also, taking packaging into consideration, a Luxeon device from Lumileds and a BL-3000 from Lamina Ceramics have totally different performance characteristics because of their chemistry, construction, packaging, and so forth.

You have two choices: Limit the voltage so that the device does not consume as much current, or limit your current and ensure that the voltage simply exceeds the maximum. Ultimately you need to regulate the current because the amount of current consumed (taking into consideration the device's ultimate efficiency) is directly proportional to the amount of heat generated in the chip itself.

You see, LEDs don't generate heat in their light path (radiant infrared travelling in parallel with the visible light, like the "heat" of the sun or a candle), but the chip itself does get rather hot, and if that heat isn't dissipated the LED chip will become physically damaged. Some [wikipedia.org] of [wikipedia.org] the materials used have melting points below 120 degrees, a temperature easily achieved by an LED not properly heatsinked.

So here's some tips: When you make LED boards (whether addressable matrices or simple blinky lights) you want to use a metal-core PCB or leave a portion of the LED's leads exposed in order to help dissipate the heat generated at the chip core and ensure longer chip life. LEDs don't just "burn out" one day, they will get dimmer slowly over time, and you can maximize that length of time by running them at less than their rated current, by cooling them actively or passively, and by using PWM to modulate their output.

Don Klipstein maintains a good set of information about LEDs: http://members.misty.com/don/ledx.html [misty.com]

Re:It's about damn time!

[Jedi Holocron (225191)]

Yeah, technically the LED itself doesn't throw out heat with the light it produces...however the "driver" (similar to a ballast on a flourescent fixture) or the electronics behind running/controlling the LED does produce a lot of heat. Reducing this ancillary heat production is another limiting factor to the adaptation of A Lamp replacement LED "bulbs".

Not sure this discovery is necessary

[gvc (167165)]

White LEDs are already 3 times as efficient as mercury fluorescent, and fluorescent tubes are 3 times as efficient as incandescent. They (fluorscent and LEDs) can get pretty good colour accuracy, too, if they want to. The only thing holding them back is price. I'm not sure what this new invention might bring to the table in that regard.

Re:Not sure this discovery is necessary

[Jedi Holocron (225191)]

No, actaully, the thing holding back LEDs from practical home applications is the color of the light they produce. More specifically the color temperature [wikipedia.org].

Typical incandescent lighting comes in somewhere around 2800-3200K. White LEDs live somewhere around the 5000-7000K range. When an efficent LED source can be made at a color temperature similar to that of incandescent lighting...then you'll see it take off in as a replacement for a standard A Lamp.

This same color issue relates to the slow adaptation of Co

Re:Not sure this discovery is necessary

[gvc (167165)]

It is the incandescent colour that is the wrong temperature, not the LEDs. Mid-day sun is nominally 5600K, and morning/evening higher. So why do you want to emulate candle-light?

Completeness of spectrum is another issue. Cheap fluorescent tubes have huge mercury spikes and little red - maybe 55% on the accuracy scale. Good tubes achieve 95% - a marked difference. This is independent of the colour temperature.

White LEDs (at leat the ones you commonly buy today) are also fluorescent, but with pretty decent spectral accuracy. It would at least in theory be possible to build an RGB array of monochrome LEDS that would produce apparent white light.

Re:Not sure this discovery is necessary

[westlake (615356)]

I imagine a hundred years ago the fact that incandescent bulb gave 2800K to candle's 1200K really hindered its adoption. Because candles were what people came to expect.

The mid 19th Century was home was lit by natural gas (if you could afford it) or by kerosene and other petroleum based lamp oils (dangerous).

Think for a moment how fifty to seventy-five years of experience with gas illumination affects interior design, men and women's fashions, cosmetics, etc.

There were real barriers to change, Competition to Edison's Lamp [si.edu]

Re:Not sure this discovery is necessary

[SuperBanana (662181)]

The only thing holding them back is price.

No- many things are holding back LEDs.

• They produce light efficiently (not THAT efficiently) but don't produce that much light compared to a very simple single-bulb HID or fluorescent tube (by the way, which tube are you basing that "3x" on? T12, T10, or T8? Because T8's are MUCH more efficient that T12's). It takes a HUGE number of LEDs to replace ONE T8 fluorescent tube- and that tube costs a few dollars tops, because it is very easy to make. Right now, a single Luxeon white LED sells in 100-1000 unit quantities for well over $10-20, and produces 1-5W. A T8 bulb will produce 30-40W, and costs RETAIL about $5.
• They require new reflector designs and light spreaders, since they are a VERY small point source. A lot of work goes into making light sources produce even, smooth lighting that won't generate harsh shadows- point sources make this job a real bitch. Point source also means that despite relatively low heat output the heat is very localized, and that means PCBs must also be heat spreaders, complicating assembly/design/manufacture further. You can't just toss them on a PCB. Companies like Luxeon now sell them on little PCBs with the necessary spreader etc, but now you're not just talking about buying an LED, you're buying a whole assembly for your product...$$$.
• Related- while they have a long life before failure, most of the high-output LEDs drop in light output very significantly, within a year or two of continuous operation 10-20 degrees above room temperature. VERY few LED manufacturers disclose this upfront- and virtually ALL the companies hawking LED products fail to mention this nice little caveat. Furthermore, just because the LED is rated to, say, 100,000 hours- doesn't mean it won't burn out because the company that made the device it is part of didn't botch the job on current+voltage regulation, heat dissipation, etc.

I know everyone thinks they are the second coming of Christ, and they do have some wonderful applications (like traffic signals and car brake lights)...but they're not the end-all be-all.

Re:Not sure this discovery is necessary

[fossa (212602)]

Bulb Efficiency (lumens per watt)

• Incandescent: 14-17.5 [1]
• White LED: 29-37.5 [1]
• Fluorescent: 50-100 [2]

[1] Why LEDs can be 10 times as efficient as incandescents in some applications but not in general home lighting! [misty.com]
[2] Are fluorescent bulbs really more efficient than normal light bulbs? [howstuffworks.com]

I'm a bit surprised at those fluorescent numbers... I don't have the box to one of my fluorescent bulbs handy to double check that, but I do know that while not as hot as incandescents, they become very hot to the touch when in use. I've never touched a lamp sized LED bulb however.

One disadvantage of fluorescents is that they contain mercury. Newer fluorescents may have found a way around this however; I'm not sure.

Not surprisingly, many of the websites I saw talked about future improvements in LED tech with goals around 100 lumens per watt.

Oh no!

[Trip Ericson (864747)]

But now we'll have to change our "how many x does it take the change a lightbulb" jokes!

"How many /. readers does it take the change a lightbulb? They don't have to because it's LED!"

No Effing Way!!!

[by Anonymous Coward]

Have you ever tried an LED light? They suck!!! They do not cast nearly enough light. The light color is a disturbing and unnatural color, usually with too much blue in it.

Florescent tubes are FAR superior to LED lights and yet so many people prefer good old incandescent lights to even florescent tubes. Hell, even something as simple as a flash light. Try an LED flash light and then try a xenon Mag Light and tell me which one rocks your socks.

LED lighting is one of those technology "revolutions" that are for the sake of technology. They are NOT better.

The greatest discoveries...

[PGC (880972)]

are not followed by 'Eureka' , but by "Hey, that's funny" .

Re:The greatest discoveries...

[B-a-Z.nl (765901)]

Let's quote the source on that now shall we?
Isaac Asimov
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny...'"
http://en.wikiquote.org/wiki/Isaac_Asimov [wikiquote.org]

Schroedinger's Bulb

[dada21 (163177)]

If I close my bedroom door, my quantum bulb will neither be working nor burnt out.

From the FAQ on LEDs

[jkind (922585)]

Answer: there are several obvious advantages LEDs have over traditional incandescent light bulbs, they are as follows:
Low power consumption - energy saving,
Long lasting,
Cold lighting,
Ruggedness,
Small size and weight,
Fast switch times,
Simple to use.
This is from the FAQ, but it doesn't list any disadvantages..
anyone care to share?

Re:From the FAQ on LEDs

[Rob the Bold (788862)]

Some Disadvantages:

Like Fluorescent, requires supporting circuitry -- doesn't plug directly into AC wiring.
Cost (initial investment)
Harder to dim -- can't use simple rheostat
Flicker (if using less than 100% on time)

I don't have anything against LED lighting, and none of these disadvantages are insurmountable. Indeed, these could be viewed as business opportunities instead. Most of the disadvantages are shared with fluorescents, and adequate solutions already exist there. I know a guy who lights his whole off-grid house with LEDs (using low voltage DC wiring). I particularly like the possibility of creating variable color lighting with LEDs, emulating daylight, sunlight, tungsten or whatever.

AC vs DC

[MDMurphy (208495)]

AC has it's advantages, especially for long distance transmission. But in a house, it's gradually losing out. If you don't count lightbulbs, I'd say I have more DC things plugged in than AC. So many of the outlets are connected to "bricks" or "wall warts" to change the high voltage AC to low voltage DC. Things that don't have an exterior brick, like the DVD player or TiVo just do the conversion internally. While the higher voltage AC might have some benefits of lower loss in the wires, I'd think that umpteen separate transformers and rectifiers are negating a large percentage of that benefit.

If lighting were go to DC, then a re-think of the home wiring would really be in order. If there were a "standard" DC voltage and current available to lower power devices, we might not have wall transformers with anything from 3v-12v hanging off our surge supressors.

So in-house DC makes lots of sense. Send the AC to things like ovens and clothes dryers, and DC to most everything else.

LED disadvantages

[Temeraire (913731)]

Anyone who tries (like me) to build small lighting devices with LEDs rapidly discovers lots of practical difficulties. To equal the light output of one cheapo fluorescent tube you need hundreds of the little blighters. It is not easy to make their output look even, rather than dotty. And with that large number, reliability is a real problem. Even a 1% failure rate (amplified to 3% or 5% by the LEDs often being in series) rapidly translates into major unevenness. Even production lines struggle to make large arrays of LEDs stay 100% alight, but little people often get sold the bin ends, which fail rapidly in service.
      Also LEDs are NOT yet more efficient than fluorescents. Their data sheets never give the one number that really matters: what percentage of input energy actually emerges as light? The answer is usually frighteningly low. Therefore LED devices tend to cook themselves to death if run really bright.
      To run LEDs stably requires either a wasteful series resistor or an expensive semiconductor constant-current device. And cheap low-voltage power supplies are actually badly life-limited by their electrolytic capacitors. In my experience many LEDs die prematurely because of a failing power supply and hot sunshine.
      Don't get me wrong. LEDs are the future, but you must be wary of calling them energy-saving, long-lasting, or easy to use!

We'll need a replacement for the Goodyear Blimp!

[by Anonymous Coward]

A LED Zeppelin, of course.

Re:We'll need a replacement for the Goodyear Blimp

[Pfhorrest (545131)]

Oh come now, that was highly uncalled for. Puns are for children, not groan adults.

(Note to mods: that's not a spelling error).

FTFA

[Associate (317603)]

When a brilliant idea pops into your mind in the future, what will appear over your head?

Answer: $$$

Ideas of the Future?

[Garridan (597129)]

"One big question remains: When a brilliant idea pops into your mind in the future, what will appear over your head?"

Smoke. That's one thing that I don't see changing any time soon. Not for me, anyway.

Re:Ideas of the Future?

[richdun (672214)]

Oh, I'm sorry, the correct answer was "an IP lawyer", "an IP lawyer." Well, thanks for playing! We have some wonderful parting gifts for you.

Thinkgeek

[Eightyford (893696)]

I'm totally surprised that they OSTG didn't pimp their LED bulb from thinkgeek. 35 bucks is a little steep though.
http://www.thinkgeek.com/gadgets/lights/7aa8/ [thinkgeek.com]


Of course, you could always make your own.
http://www.etgtech.com/update/products/super_flux. htm [etgtech.com]

LED efficiency versus Compact Fluorescents

[lancejjj (924211)]

This could be a big advance for LEDs. But as of now, commercially available LEDs do NOT produce as many lumens per watt as Compact Fluorescent Light bulbs (CFLs.) [doe.gov] Of course, this new LED discovery may improve LED efficiency to the point where they exceed CFL efficiency. We'll have to wait and see.

CFLs are inexpensive and readily available today. CFLs have a long life, and they save a ton of energy when compared to traditional light bulbs. Even more importantly, they don't suck like the CFLs of a few years ago that had a noticeable/painful "warm up" time.

I save quite a bit off of my energy bill [blogspot.com] by using CFLs. They really cut down on electricity consumption, and I've never had one "burn out" on me. Ever. Yet.

Re:LED efficiency versus Compact Fluorescents

[dr_db (202135)]

CFL's do not like enclosed fixtures - I live in a rental, so I am not inclined to change them, but *every* cfl I put in those fixtures failed. I did post-mortens on them, some seemed to have unsoldered themselves (wires off the board) and others just seemed to have died. They never seemed to feel hot enough to melt solder, but the conditions in the base while running might have been pretty rough. So 15 have failed, 2 survived (in open socket applications). Many rooms in my house have regular tube fluore

Costly Quantum Dots

[ObligatoryUserName (126027)]

If the manufacturing breakthough talked about in this article [monstersandcritics.com] pans out, the cost of Quantum Dot manufacture will drop from $2,000 to $400 per gram. That's huge improvement, but I still wouldn't expect to see Quantum Dot lightbulbs on ThinkGeek anytime soon...

Current LEDs are not there yet

[The Optimizer (14168)]

I just finished converting the lighting in my house to save energy, and learned a few things in the process. Most of the incandescent bulbs were replaced with compact fluorescents, but I did install 4 LED light bulbs in one application.

The current generation of compact fluorescent bulbs has come a long way from the ones I remember 10-20 years ago. They don't have the flicker or startup problem anymore, and they are available in a variety of color temperatures from 2700 degrees (yellowish, comparable to incandescent) to 6100 degrees (white, sterile). For the same light output (lumens), energy consumption is normally 22% to 27% of the incandescent bulbs they replace. They very slightly in things like color and wattage depending on the manufacturer.

Nobody who has visited my home has yet noticed the difference.

Since you can find common CF bulbs sizes for under $2 per unit (try Sams Club, etc), and they should last 4 to 8 times as long as an incandescent, the economic case is pretty sound even before factoring in the energy savings.

I replaced 4x 7.5 watt bulbs with LED bulbs and noticed a few things. The LED bulb itself is about twice as large, and as others have mentioned, the light emitted is an eerie blue-white light. You defiantly notice it. These bulbs consume 0.8 watts and produce an output pretty close to the 7.5 watt bulbs they replaced, though I could not find the output in lumens for either bulb anywhere. They were about $7 a bulb, and are rated to last 100K hours, or about 50 times as long the bulbs they replaced. Since the bulb is actually made of up 18 individual LEDs inside, I believe the rating is for the mean time until 50% of the LEDs are no longer functioning.

After converting 152 of 160 bulbs in my home, my electric bill happy.

Mixed reviews from me

[Just Some Guy (3352)]

I've switched a lot of my bulbs over to the CFs available at my local home store (Feit Electric; their websites down right now or I'd link it). The problems I have with them:

1. Most of them start nearly instantly, but dimly. They get brighter as they go, usually peaking after a minute or so.
2. At least half of them smell like magic smoke when you get close to them. One of them had me looking for an electrical fire inside my walls until I figured it out.

Once they're up and running, they're bright, ni

Re:Mixed reviews from me

[Yaztromo (655250)]

Are these "features" of all CF bulbs, or is the brand I've been buying really crummy?

I've recently converted my apartment to CF bulbs as well, and I've noticed mixed results in this regard. The Noma 60W equivalent bulbs in my hall and bedroom lighting fixtures don't exhibit this problem -- or if they do, the brightness differential is so minimal that I don't notice. They come on immediately and are at full brightness immediately (or at least as fast as I can perceive).

I also have a dimmable 100W equiv

Re:Current LEDs are not there yet

[tylernt (581794)]

Were they placed horizontal or base-up? When CFs are installed base-up, the heat from the bulb rises and tends to cook the ballast, shortening lifetime. They do a lot better in base-down or horizontal installations.

I have a huge 45w (200w equivalent) CF in my garage. Going on 3 years, still works great. And it's even base-up.

I've had a few CFs burn out within a few months, too. I think some of them just have manufacturing defects.

led's, worse than flourescents.

[plasmacutter (901737)]

I have an led flashlight.

led's emit a very cold light. Fourescent light is described as cold and "vitamin burning", but led light is even worse in this respect.

It works for headlights, emergency beacons, and select areas, but generalized room lighting is not one of those areas.

As a lighting design student...

[maino82 (851720)]

I can definitely see the benefits of LEDs when compared to other forms of electric light. They do produce more lumens per watt than most other sources, but they do produce a good deal of heat when combined together into a large array, despite what people may tell you. They also have the added benefit of efficiently producing (since they only produce light in a certain wavelength) just about any color you would want through color mixing of different color LEDs (check out the tunnel in the Detroit airport if you'd like to see a well done example). Personally, though, I would love to see more daylight in spaces rather than a push for the latest and greatest in electric light. If done properly, daylighting can greatly increase light levels in the workplace and lower energy consumed by electric light. Generally, this will lead to an increase in cooling load, but this is almost always smaller than the amount of energy saved by eliminating electric lighting (again, if done properly). So while I'm all for more efficient electric lighting, it would be nice to see no electric lighting used during daylight hours when the sun is readily available.

Why it's still not time for White LEDs

[josephdrivein (924831)]

The main reasons why White LEDs are still not ready for general purpose lighting are:

Low CRI (Color Rendering Index) that means bad illumination compared to incandescent
Low temperature of operation (120-150C max)

Most electronic design that include hi power LEDs (such as LUXEON http://lumileds.com/ [lumileds.com]) need to take in account hheat transfer.