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As my car uses regular headlamps as daytime running lights (and at $15 a pop, I really don't like replacing them every 6 months), I wonder why no one has implemented untrabright white LED's for daytime running lights, or even as citylights (for Europeans). As a matter of fact, how come the largest white
LED they make (or at least what I have found) is only 10 mm?
An LED efficiency area
http://www.howstuff...com/question424.htm
Your link, Amishman35. I fine one, I might add. I don't know how scientifically accurate this is, but the 'law of unintended consequences' is worth mentioning. [reensure, Apr 17 2001]
(?) Truck-Lite LED running lights
http://www.truck-li...enbr=26&cgrfnbr=645
[rmutt, Apr 17 2001, last modified Oct 04 2004]
A great idea
http://users.snip.n...CLAMB/MODULATOR.HTM
Running lights on cars make it more difficult to spot motorcycles - here's the solution [FloridaManatee, Oct 04 2004]
Luxeon Stars
http://www.lumileds...products_index.html
Superbright LEDs [evildman, Oct 04 2004]
[link]
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probably because LED's are a pain in the neck to aim using lenses. it's also possible that they just don't put out enough light for the buck compared to halogens or xenons. considering that you would need a few hundred LED's to make the equivalent of one halogen, you'd probably end up paying more. |
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They've just started using what look like an array of LEDs for traffic lights in the UK. The LEDs (if that's what they are) are bright enough for daylight use and when one fails the traffic signal is still usable. |
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LED daytime running lights are much more efficient and they last longer.
http://www.howstuffworks.com/question424.htm |
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Blue LEDs, necessary to make white light, are still to expensive to be economical in this sort of application. Maybe some day. |
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LED brake lights and turn signals are quite baked; I see them on cars and buses all the time. |
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You have to replace your headlights every 6 months? That sounds like an awful lot, even if you do have them on all the time. |
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Colored LEDs will last a long time, but white LEDs will burn out eventually as the phosphor degrades. Rmutt was unable to find any specs on the lifetime, but supposes it is comparable to fluorescent tubes or CRTs (which is still a lot longer than incandescents). Now if they only cost less than three bucks a pop... |
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First of all, LEDs do not contain phosphor. That's the material in flourescent tubes. LEDs are solid state devices, similar to transistors, that emit light when energized. Second, modern hi-intensity LEDs last ~50-100,000 hours - that's about 15-30 times as long as a halogen headlight, and typically 5-10 times as long as a flourescent tube. With proper lenses, modern ultra-bright LEDs can produce quite bright light, and it can be focused more than adequately to serve for DRL purposes. The main reason automakers don't use them, I suspect, is because it would involve installing an additional light source just for DRLs that would not be used for night illumination. That would add cost and complexity... it's easier, and cheaper, to just activate the headlamps at reduced voltage levels. Now... does anyone know how to disable the damned things on a 2000 Pontiac Grand Am? |
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Oh bl**dy h*ll. I wish I'd seen [rmutt]'s link before I built my LED brake light array in college for my 125cc bike. |
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Even though it outshone incandescents on the 6V electrical system, I remember it was technically illegal, as it didn't use the equivalent minimum wattage. |
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BTW, if you want to focus a light beam from a bank of LEDs, you can encapsulate them in a block of clear plastic, shaped so as to focus the beam. I believe early ruby lasers and light-gathering skylights used a similar technique. |
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squirl033, Jan 09 2003: *most* LEDs don't contain phosphor... but white ones are actually blue LEDs with a phosphor for producing white. There is a car with LED *headlights* but it is a concept car. Audi i think. |
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Actually there is a company by the name of Lumileds which produce a new type of LED known as Luxeons (see link) which are basically nseveral oversized LED emmiters in a single die package. Depending on the color and modem you choose they are roughtly as bright as 10-20 normal superbright LEDs each. They can also be ordered in custom configurations. They do however start at about $20 each unless your ordering in mass quantities. |
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Umm what about GM's New Trucks etc? They have seperate lights for DRL's. My firends Jaguar has a LED in each headlight, but thats to light the headlight housing up, but it stays on till the headlights are on. |
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Oh and the concept car with the LED headlights was a Cadillac. I cant remember the model name, but i know it was a cadillac. It used LED's and prisms to create the light.. It is pretty cool to see a diagram, but i cant find that either.. What i dont understand is that if they can use LED's for Tail lights, why not for DRL's? I dont think it would take very many, I have a Lunar Accent 4 led blue light tube. I can put that in my windsheild, and you can see it for a LONG ways, in the day time... So i unno. What would be cool is that since LED's dont use very much battery, is when you turn the car off, the DRL cluster of LED's stay on "Bright" for 60 Seconds after you exit the car, then go onto a "Medium" or even a "Low" mode and stay on till the car is started again, Lighting around the car in the dark.. I think it would be Cool anyways.. LOL .. -Josh |
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Yeah,squirl033, as achoo pointed out, white LEDs DO have a phosphor, excited by blue LED. I have some 10,000 mCd ones; jeez they're bright. Don't think they'll ever be bright enough for headlights, tho. |
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Btw, are there a lot of dickheads where you are who drive around with their fog lights on ALL the time?? They are in the millions around here and it drives me nutz. |
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A problem in cities is that of light polution, this is becuase not enought light spans out to cover the areas that governments would like to cover. So they install lights that spread out and reflect off everything and produce a lot of light polution. And that trees often get in the way of lights reaching the roads and footpaths. |
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I think that strings of lights can be ran around the city scape and can be put at lower levels thus making it safer to install street lights. |
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