I’ve noticed that in the last few years, LEDs have become more common in application such as rear brake lights and turn signals in cars, and traffic lights.
LED computer monitors put out a range of colors using RGB subpixels to mix colors to simulate the entire spectrum of visable colors per pixel, including white light.
Using this idea, is it possible that eventually we will see LED car headlamps?
I’ve already seen a flashlight with white LEDs.
Is a cluster of LEDs…using a parabolic reflector or some kind of lens…strong enough to project a beam so-many hundred feet ahead of a car? This is yet to be seen.
Every year affordable LED’s are becoming available in higher powers. As Enola Staight already pointed out, LEDs are available in white today with some of them pretty bright.
It wouldn’t surprise me if they get bright enough for a reasonable cost and we see some used in car head light before long. (say, less than 10 years, and 5 wouldn’t be to unreasonable.)
There would be some great advantages.
White LEDs aren’t as efficient as manufacturers lead you to believe. The efficiency is actually close to that of high quality halogen bulbs. Also, it’s difficult to make a large bright LED. The Nichia LEDs found in flashlights are less than 0.2W. The brightest LED currently available is the Luxeon Star, but it’s still only 5 watts so you need several of those to make an effective automotive headlight. But if you use an array of LEDs, you need a reflector and lens on each LED. Worse still, LEDs are very sensitive to heat so you need a heat sink connected to each LED. LEDs do have advantages such as long life, whiter light and faster response, but currently not enough to overcome the disadvantages.
But there is another alternative - high intensity discharge (HID) lamps. These are several times more efficient than halogen bulbs or LEDs and produce a pure white light. They are complex and expensive, but they are already common in luxury cars.
LED headlights are already available for bicycles. The CatEye EL-300 uses 5 LEDs, each with its own focusing lens. Still, I find it’s not a big improvement over halogen lights. The manufacturer claims long battery life but that’s because of the low power (1 watt total), not high efficiency.
Incidentally, HID bicycle lighs are also available, like the NiteRider Blowtorch. They cost over $300 and intended only for competitive off-road riding.
Most car owners replace their headlights maybe once or twice during their time with their vehicles, and at $15 bucks a pop it’s no big deal. A white headlight LED array would cost close to $1,000 and the benefits are intangible (a few cents worth of gas each 100 miles lost due to increased alternator load). You might save $2,000 in gas over 100,000 miles but who’s gonna go for that $1,000 of potential profit when it comes with a $1,000 increase in dealer price?
White LEDs are not exactly what they seem; apparently the actual diode emits coloured light internally, which is converted to white light by a phosphor.
I was looking yesterday and RS components have packages with R G and B in a single unit; I think I’ve seen these used in arrays as stage lighting.
Behold!
It has been done - check out the Fioravanti Yak concept car.
As it has been pointed out LEDs aren’t all that efficent - 10% for green, 20% for blue, and 40% for red. So there’s plenty of room for improvement.
Where does the remaining energy go? (I thought LEDs generated very little heat)
The remaining energy turns into heat, as you’d expect. White high-power LEDs generate quite a bit of heat. I was playing around with a 1-watt Luxeon star LED yesterday and even with a heat sink it got too hot to touch.
Color LEDs generate very little heat compared to colored incandescent bulbs. With a bulb you are generating a white light and then absorbing most of it with a color coating or filter. Color LEDs produce monochromatic light to begin with, so there is no need for a filter.
I want to get some of those Luxeon LEDs, but it looks as if I’d have to buy 200 of them.
> it looks as if I’d have to buy 200 of them
Are you trying to buy direct from the manufacturer? There are many on-line shops that sell those. I got a pre-packaged 1-watt bulb from LEDCorp but I think you can find bare LEDs for much less elsewhere. Just do a net search. I’m not sure about the availability of 5-watt versions, those are very new.
(LEDCorp doesn’t say what LEDs they use, but I’m pretty sure their “Pro Series” bulbs use Luxeon Stars. The cheaper ones are plain old Nichia LEDs.)
Please give a cite where LED’s are close to halogen bulbs - I just can’t beleive it. I have a Photon fusion 6 white LED light and on max brightness I get about 5-6 hrs of light on 3 AA’s and about the same amount of light as a 2 D cell flashlight that may last about an hr or 2. aLSO on max brightness the light is not even warm.
Perhaps upscalling LED produce heat?
This FAQ, for example, states that LEDs are slightly less efficient than halogen bulbs. I tried to look for actual data sheets but Nichia doesn’t seem to state the brightness in lumens. (Candlepower is power output in a particular direction, so a high candlepower just means the beam is well focused.)
… that being the case then, is it that all these LED torches are only able to boast superior battery life because of a reduction in light output?
Basically, yes. The color is also different - LEDs are more white or bluish, so they appear brighter.
BCULLMAN
Are you sure you’re not confusing LED with LCD in this statement? I realize that some large screens, like Jumbotrons and stuff, use LED’s but most everything I’ve seen that qualifies as a “monitor” was LCD.