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Power Technology

Making Strides Toward Low-Cost LED Lighting 398

Roland Piquepaille writes "You all know that incandescent bulbs are pretty inefficient, converting only 10% of electricity into light — and 90% into heat. Light-emitting diodes, or LEDs, could soon replace incandescent and compact fluorescent bulbs in our homes. They are more efficient and environmentally friendly. But LED lights are currently too expensive because they are using a sapphire-based technology. Now, Purdue University researchers have found a way to build low-cost and bright LEDs for home lighting. According to the researchers, the LED lights now on the market cost about $100 while LED lights based on their new technology could be commercially available within a couple of years for a cost of about $5. It would also help to cut our electricity bill by about 10%."
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Making Strides Toward Low-Cost LED Lighting

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  • Light vs. heat scale (Score:3, Interesting)

    by WhoIsThePumaman ( 1182087 ) on Sunday July 20, 2008 @02:47PM (#24264553)
    I'd be interested to see a progression timeline of the light vs. heat ratio from the various methods we've used. I'd imagine candle and torches would be the heaviest on the heat side, but seeing it slide with gas lamps, lanterns, incandescents, CFLs, and now LEDs would be neat. Anyone have some spare time on their hands?
  • LED = Luxury Goods (Score:5, Interesting)

    by cdrguru ( 88047 ) on Sunday July 20, 2008 @02:48PM (#24264563) Homepage

    Take a hint from the car manufacturers. Today, high-end cars are using LED tail lights. They are also used on trucks. The main advantage is they do not burn out.

    However, for most people in the world a burned-out tail light bulb is a minor safety issue and a minor expense. Replacing the bulb takes 10 minutes and maybe the owner's manual if you are truely clueless about how to do it. Also, many people own a car for 5+ years without ever having to replace a single bulb.

    Compare this to the cost of a minor traffic accident where a tail light is cracked. No, you cannot replace the lens or any individual part, just the whole assembly. Instead of $100-$200 for an incandescent bulb assembly expect to pay $1500-$2000 for the LED tail light.

    Sure, over the life of many vehicles it is a minor issue that bulbs will never burn out. But over the same number of vehicles it is far, far more likely that a lamp assembly will have to be replaced. The result is a far more expensive part to replace.

    With trucks there is a certain amount of sense to be made with claiming that the bulbs do not have to be replaced. Replacing a bulb on a truck or semi-trailer can be a real hassle requiring a ladder and tools. However, again the likelyhood the bulb would ever need to be replaced vs. the lens being damaged is about the same as for cars. Basically, it is a complete rip-off.

    Expect to see wired-in LED systems in household lamps where the fixture must be replaced because the bulbs cannot be. Expect to see the fixtures sold to builders with non-replacable bulbs will cost the builder only slightly more when bought in huge quantities but the homeowner will be faced with $1000 lamp fixtures should they ever need or desire to replace them.

  • by Animats ( 122034 ) on Sunday July 20, 2008 @02:53PM (#24264603) Homepage

    It's so Roland the Plogger.

    1. Find some minor advancement in materials science.
    2. Hype it as big breakthrough.
    3. Post on Slashdot.
    4. Direct traffic to ad-heavy blog.
    5. PROFIT!

    The "breakthrough" this time is that someone made gallium nitride substrates that might, someday, be useful for LEDs. After they solve the problem that their material cracks during cooling. However, Panasonic did that last year [], and has been shipping white LEDs using that approach in sample quantities.

  • Do LEDs blink ? (Score:5, Interesting)

    by dargaud ( 518470 ) <> on Sunday July 20, 2008 @02:59PM (#24264663) Homepage
    Today for the first time I noticed a car with blinking tail lamps. When I say blinking, I mean it was blinking as fast as a CRT monitor, but the problem is that I can see it. I'm one of those people who has never been able to stand CRT monitors at less than 100 or 120Hz. I also have a hard time with some fluorescent lighting. I suspect what I saw was the lousy application of LEDs on the backside of a car.

    So, suck it up, I hear you say. Right, except that each blink leaves an annoying remanent patch on my retina that lasts for a few seconds. Imagine driving at night in a city, 10 cars in your field of vision, look left, right and suddenly you have 200 spots in your field of vision. Awesome to know what's going on, right ?

    I loathed the xenon high beams when they first came out a few years ago. You know, those tiny very concentrated blue lights ? Leaves a retina trail that lasts for 20 seconds. I'm so glad that they are gone now. I've never heard if they were made illegal or if they just went out of fashion, but I hope LEDs (which are a good technology) are applied in a good way...

  • by ModernGeek ( 601932 ) on Sunday July 20, 2008 @03:06PM (#24264727)
    I have noticed that with LEDs, they are brighter than a comparable halogen bulb + filter, but they do not light up the surrounding area as well. I have an LED lightbar on top of my vehicle (volunteer firefighter), and the lights are brighter, but compared to a halogen lightbar, it does not light up the area with red and white the same. It is definitely more visible though. That is why I think LEDs might be good for taillights and such, but probably not for headlights.
  • Re:Yea, (Score:4, Interesting)

    by tomhudson ( 43916 ) <> on Sunday July 20, 2008 @03:12PM (#24264761) Journal

    Poster saith:

    Let's not forget improved cold weather characteristics

    TFA saith:

    "You all know that incandescent bulbs are pretty inefficient, converting only 10% of electricity into light and 90% into heat

    Me: "I live in Canuckistanbul - we NEED the heat, you ignorant clods!"

    Electricity costs less than oil or gas here ... it's cheaper to get some extra BTUs from incandescents in the winter months ...

  • by sdpuppy ( 898535 ) on Sunday July 20, 2008 @03:15PM (#24264783)
    Phosphor? Thats a bit disappointing. While I haven't followed the field much, I would have expected that they would have have come up with a way to make a variable band gap so you have electrons jumping back and forth over a wide range of frequencies.

    Another thing I imagine might be to make the LED as an integrated circuit - an array of LEDS with each junction a slightly different gap than the preceding, so while you don't really get a true continuum, a few million different colors would be awfully close (and besides the frequency that an LED produces does have a band width, so if each color is close enough, you do get a continuum with enough colors.)

    Anyone know if anyone is working on either method?

  • Re:Yea, (Score:5, Interesting)

    by kaizokuace ( 1082079 ) on Sunday July 20, 2008 @03:28PM (#24264901)
    not just an illuminating wall. Imagine the entire ceiling covered in an OLED sheet and have lighting do cool stuff like follow you around or whatever. Rooms with people get lit while others don't. Crazy flashy lights for parties. the possibilities are limitless!
  • CFL Color (Score:5, Interesting)

    by wooferhound ( 546132 ) <> on Sunday July 20, 2008 @04:11PM (#24265261) Homepage
    you need to look at the Color Temperature when you buy CFL bulbs. A CFL rated at 2700 degrees Color Temperature will look almost exactly like an incandescent light. A CT of 3000 degrees is called a warm white and is very pleasing. A CT of 4000 is called a cool white and looks a little bit blue. And a CT of 5000 degrees or more is about the same color as Sunlight and appears to be very blue indoors.

    I really like the color you get when a 2700 & 5000 degree light are in the same fixture, everything looks bright and colorful.
  • Link (Score:3, Interesting)

    by scorp1us ( 235526 ) on Sunday July 20, 2008 @04:17PM (#24265303) Journal

    Luxim Plasma []

  • Re:Yea, (Score:5, Interesting)

    by pz ( 113803 ) on Sunday July 20, 2008 @04:24PM (#24265349) Journal

    Well, they won't flicker, they won't contain mercury, and they won't be too big to fit in many light fixtures.

    Even if LEDs aren't any more efficient than current CFLs, they'll be a lot more attractive to people who don't like or can't use fluorescent lights.

    Have you actually looked at high-quality CFL bulbs? A good daylight bulb is a thing of beauty. No flicker (and, you know, CFL bulbs have never had flicker because they are run at much, much higher frequencies than you visual sytem can see), proper color balance, small, reliable, quiet.

    Note that I'm not talking about the two or four foot long fluorescent bulbs that you might have in your office. Those are probably not daylight balanced and probably flicker at 120 Hz (yes, 120 Hz, not 60 Hz, because both half cycles push current; unless you're in part of the world which runs on 50 Hz mains, in which case they flicker at 100 Hz). Their ballasts also have a tendency to buzz.

    Good CFLs are wonderful.

    Note, also, that many LED bulbs you can get these days are simply awful because they flicker at 60 Hz (yes, 60 Hz, because they're arranged in cascading diode fashion and only conduct on every other half cycle) and the phosphors are terrible. They also lose brightness at an astonishing rate and are horribly temperature sensitive (hotter chip, lower light output). The 60 Hz issue can certainly be fixed with better circuitry (ie, bridge rectifiers and some low-pass filtering) and one hopes that the phosphors and lifetime improve.

    Wait, phosphors in an LED? What am I smoking? Yes, it's true, most white LED bulbs for sale are actually UV emitters that excite phosphors. And just like fluorescents, the better the phosphors, the better the output spectrum. While it is possible to generate white-ish light from a combination of red, blue, and green LEDs, because the aging curves are different for the three classes of emitters, the color balance is dynamic over the bulb lifetime. And, also, the spectrum is terrible -- even the spectrum from fluorescents is better -- because it's essentially three isolated wavelengths instead of a continuous spectrum.

    LEDs have a long, long way to go before they can be used in living or working spaces.

  • Re:Yea, (Score:3, Interesting)

    by xaxa ( 988988 ) on Sunday July 20, 2008 @05:05PM (#24265639)

    I've never had a CFL burnout

    They will do. My parents were early adopters (must be over 15 years since we had them), I think the only incandescent light in their house is in the microwave.

    I remember the first ones cost about £10 and were massive, heavy things and they did flicker, and take five minutes to warm up. But the ones made in the last 5 years or more are brighter, white, don't flicker, and don't buzz. They do (eventually) burn out though.

    Yellowy incandescent lights remind me of my grandma's house; admittedly the yellow effect was enhanced by her cigarette smoke.

  • by xaxa ( 988988 ) on Sunday July 20, 2008 @05:15PM (#24265709)

    They are. I've seen some in nightclubs and at concerts, the brightness and the instant on/off effect is fantastic.

    It's probably even better with ecstasy.

  • Re:Do LEDs blink ? (Score:1, Interesting)

    by Anonymous Coward on Sunday July 20, 2008 @05:27PM (#24265805)

    The blinking circuit is too allow different brightness levels such as the difference between braking and having the tail lights at night. It is much cheaper to simply use pulse width modulation with the already available ECU then it is to build a variable current analog circuit.

  • by Maxo-Texas ( 864189 ) on Sunday July 20, 2008 @05:36PM (#24265877)

    Very dim. About 50% of the amount of light they advertised to put out.

    Even adding a lot of these wouldn't increase the light above "dismal" level-- the intensity of the light was just lower than that put out by CFL and incandescent.

    I want LED to work-- they last a long time, they use no power, and they have no mercury.

    These might be okay for a porch light-- dim but always on.

  • Re:CFL Color (Score:5, Interesting)

    by ivan256 ( 17499 ) on Sunday July 20, 2008 @05:56PM (#24266039)

    Here's some links:

    A white LED's spectrum []

    A CFL's spectrum []

  • by smellsofbikes ( 890263 ) on Sunday July 20, 2008 @06:27PM (#24266299) Journal

    For what it's worth, one reason trucks have gone to LED's is that they don't die because of vibration, like incandescent bulbs do. We don't really know how long LED's will last, but if they're correctly designed, they should still have at least 50% brightness at 50,000 hours of operation.

    All the LED lighting solutions my company is building, and all the ones from our competitors that we've been buying and taking apart, are screw-in replacements for existing bulbs. Every single one, without an exception. If car companies wish to make their cars more proprietary by specifying custom LED lights, well, they're free to, but I think it'd be a stupid move.

  • by Mr. Flibble ( 12943 ) on Sunday July 20, 2008 @06:37PM (#24266391) Homepage

    Dimming LED's.

    LED's are commonly dimmed in headlamps. I have right next to me a Petzel Tikka XP Headlamp that has multiple LED light settings. And yes, each of those settings is a different dim setting. The LED can also be "over-driven" for a short period, putting out more light than normal.

    So, parent poster is correct, LED's do dim, and they dim quite well.

  • Re:Do LEDs blink ? (Score:5, Interesting)

    by Chrontius ( 654879 ) on Sunday July 20, 2008 @08:38PM (#24267525)

    What you are seeing is the pulse-width-modulation dimming of the taillights applied with insufficiently high frequency. Cheap chinese flashlights like the Jetbeam C-LE (which has gone through three revisions prior to current - and is an absolutely excellent little LED torch) have been using increasingly high PWM frequencies to get around that; more expensive ones use current regulation (which averages the current of the PWM circuit over a few tenths of a second to produce a flat current (and therefore brightness) curve when viewed on an oscilloscope. The advantage of lower PWM frequencies is that the eye hands them off to the brain via a high-priority nerve link that results in people noticing them significantly (tenths of a second or so, IIRC) faster, theoretically reducing both the number and severity of accidents. The fact that many of them are bright enough to impair normal night vision seems to be lost on auto designers.

    HID headlights have not gone away, but their implementations have been getting better - projecting beams on a down-angle so they don't nail people in the eyes, lowering the operating temperature of the bulb, making them less blue and more yellow-white without making them dimmer (actually, lower-temperature HID bulbs are more efficient than the blue-tinted ones). HIDs are popular for bulb life being insane, since headlight replacement was getting to be a significant drain in carmaker's warranty claims, and being brighter and having a longer effective range, which is good when there's no streetlights.

    Entirely different is the blue-tinted halogen bulbs that are simply normal bulbs with a light blue paint applied - these are the ghetto-fabulous attempt to make it look like you've got an expensive HID conversion for an older car, and are about 30% dimmer than normal halogen headlights despite being harder on other drivers' eyes. I have no forgiveness for people who use these because they think it looks good.

  • dental fillings (Score:4, Interesting)

    by falconwolf ( 725481 ) <<falconsoaring_2000> <at> <>> on Sunday July 20, 2008 @11:15PM (#24268917)

    That's all well and good but you would be surprised at how much mercury gets into the environment from dental fillings and how few people will pay the extra $15.00 to get composite fillings!

    Not everyone knows dental fillings contain mercury. I got into an argument with someone over that, I had to prove to them mercury was used. And not all dentists use composite fillings [].


  • Re:Yea, (Score:2, Interesting)

    by Cpt. Fwiffo ( 42356 ) on Monday July 21, 2008 @07:45AM (#24271835)

    Funny thing, that.
    The dutch wikipedia site shows they do:
    Dutch article on Ledlamps []
    See the table...

  • Re:Yea, (Score:3, Interesting)

    by BigDogCH ( 760290 ) on Monday July 21, 2008 @09:47AM (#24273019) Journal
    If you put them on a dimmer, make sure the power is maxed. My parents have had several CFLS die, all on their lights that have dimmers. They will buzz and flicker more on a dimmer as well. When we remodeled, we didn't use any dimmers, because we have all CFLs. Will LEDs work on a dimmer?

Adding features does not necessarily increase functionality -- it just makes the manuals thicker.