Slashdot Mirror
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 to fly in to?
-Myke
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.
Click here or here.
How many cats does it take to change a quantum dot?
I will go to leds when they meet my budget....just a matter of time.
Considering that the average lightbulb creates more heat than light, this is great!
Yes Francis, the world has gone crazy.
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.
But now we'll have to change our "how many x does it take the change a lightbulb" jokes!
/. readers does it take the change a lightbulb? They don't have to because it's LED!"
"How many
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.
are not followed by 'Eureka' , but by "Hey, that's funny" .
The Dutch will inherit the earth. If not, we'll settle for a bit of ocean. Beta delenda est!
If I close my bedroom door, my quantum bulb will neither be working nor burnt out.
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....
every day http://en.wikipedia.org/wiki/Special:Random
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?
~jennifer.k~
A LED Zeppelin, of course.
Answer: $$$
Someone hates these cans.
"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.
http://www.google.com/search?q=Michael+Bowers+Vand erbilt+University
u mdot_led.htm
http://exploration.vanderbilt.edu/news/news_quant
I'm totally surprised that they OSTG didn't pimp their LED bulb from thinkgeek. 35 bucks is a little steep though.
. htm
http://www.thinkgeek.com/gadgets/lights/7aa8/
Of course, you could always make your own.
http://www.etgtech.com/update/products/super_flux
Religion for nerds. Stuff that really matters
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.) 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 by using CFLs. They really cut down on electricity consumption, and I've never had one "burn out" on me. Ever. Yet.
If the manufacturing breakthough talked about in this article 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...
Oh come now, that was highly uncalled for. Puns are for children, not groan adults.
(Note to mods: that's not a spelling error).
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
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.
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.
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.
every day http://en.wikipedia.org/wiki/Special:Random
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.
VLC FOR MAC IS DYING! IF YOU DEVELOP, PLEASE SAVE IT!!
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.
The quantum dots were supposed to emit blue light, but instead they were giving off a beautiful white glow.
I bet Marie and Pierre Curie thought something similar at one point. "Hey look, this lump of weird metal that we produced is glowing so pretty... hey, if I put it in my mouth, my eyes glow too! Fun!"
I want to delete my account but Slashdot doesn't allow it.
I'm a professional firefighter and a lot of the guys have started using LED flashlights. I had just purchased my own (out of my pocket and not the city's) rechargeable StreamLight that uses a halogen bulb. When I started seeing the LED's showing up I thought I had made a mistake. They "seem" bright but after seeing them more and more I'm convinced it's just because the light is so white (slightly blueish) and clean.
However even though it looks brighter in fact it's less so and seems to accentuate shadows MUCH more.
I really haven't discussed power consumption with anyone yet but for now........ at least in this application....... I'll stick with the older technology.
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!
(I hate scientifically-illiterate journalists.)
Time is Nature's way of keeping everything from happening at once... the bitch.
Once they're up and running, they're bright, nicely colored, and cool to the touch. But having to wait a full minute for the stairwell bulb to get bright is pretty suboptimal.
Are these "features" of all CF bulbs, or is the brand I've been buying really crummy?
Dewey, what part of this looks like authorities should be involved?
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/) need to take in account hheat transfer.
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.
yes, here is the link to the actual article. http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/as ap/abs/ja055470d.html
Have a nice day.
The frequency distribution of this light is so much more natural than the other low-energy alternatives! I wonder if it could be made to match the frequency distribution of sunlight more closely by just rearranging the mixture of the sizes of the quantum dots. Anyway, this is excellent news. It's because of the spectrum distribution of fluorescent bulbs that I refuse to use them. It's not that I like wasting energy, but even without ugly light, winter is depressing enough in upstate New York!
I'm an LED flashlight geek, so I'm realistic when it comes to lighting a house with LEDs. I'd be surprised if in 20 years we weren't replacing CFLs with LED bulbs, but at the moment it's not a worthwhile investment.
Right now, I'm happy with my CFLs: for the wattage needed to light my living room and foyer with incandescents (140 watts), I can light my whole apartment on a dark October day. It's definitely a mood-lifter to not have to worry about my electric bill, or have the place look like a funeral home.
OTOH, incandescents may not be so quick to fade away: the efficiency of tungsten filaments can be significantly increased by using crystals instead of wires.
Hmmm, if you shine a strong enough laser on *anything*, it can give off a beautiful white glow...
Oh well, what the hell...
http://www.llnl.gov/str/Lee.html
"With all these different colors, it's now possible to make light-emitting diodes (LEDs) from quantum dots," says Lee. "We've come up with a process so easy you can almost do it in your garage. We can put these dots in a polymer and make thin films that are 1,000- to 2,000-angstroms thick. This means we can create precisely tuned blue or green LEDs."
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!
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.
"National Security is the chief cause of national insecurity." - Celine's First Law
Yep, I was wrong. The full text peer reviewed article is availabe: J. Am. Chem. Soc., ASAP Article 10.1021/ja055470d S0002-7863(05)05470-3
Web Release Date: October 18, 2005
Basically though: Magic-sized nanocrystals are so small that the electron wave function has significant overlap with the selenium surface sites.17,18 Therefore, any hole trapped on the surface would likely encounter the electron before nonradiatively relaxing to the ground state.
Quantum yield is currently only at 2-3% - I'd be curious to know what the theortical max for the quantum yield would be assuming better manufacturing of the dots. Also, these things do not last forever - in the paper they take them out to ten days of excitation, but I imagine it might be quite a challenge to extend the life of these.
ôó
....Tag.
Considering that the average lightbulb creates more heat than light... Kind of like most slashdotters!
I tried to moderate your comment and had to give up in the End as i couldnt decide whether You were Funny or Insightful.We need a new "Funny Because True" Tag.
Wanted : A Signature.
Thanks for the link, I bookmarked the homepage to explore the site. I noticed one thing on the page where it says there's a problem with Fluorescent lights, "Use halogen lighting for outdoor applications where temperature causes problems with fluorescents." I lived in Florida and never had a problem using them outdoors and I currently live in Minneasota and haven't experienced problems here either. I've lived and used CFLs in both heat and cold without problems.
FaclonShould there be a Law?
HomePower said the experiment was performed to compare lights suitable for task lighting, as opposed to room lighting; then they avoid using a CFL with a reflector that is suitable for task lighting. In other words, they lit up the entire room with the CFL, but concentrated the light output of the LED bulb only onto the measuring photocell.
Makes you wonder about the results of anything else in that magazine.....
Someone else pointed out to me that in the following issue of "Home Power" they printed a correction saying the test focused on task not area lighting so LEDs would be better because they concentrate light into a small spot. CFLs are still better for area lighting. Sorry about the confusion.
FalconShould there be a Law?