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White LEDs for a Brighter World
deepfry writes "CBC radio today featured an interview with Dr. Dave Irvine-Halliday, an engineering professor at the University of Calgary, who's developed a home lighting system for the developing world using a combination of white LEDs, pedal generators and rechargable batteries. This type of "pico-power" can make a huge difference in the lives of villagers in rural areas where being connected to a power grid is not an option and probably never will be. Read about the Light Up the World project and make a donation."
Because, while that bulb only consumes 0.1 W, it gives off as much light as a much brighter incandescant bulb. I didn't see figures in the article, but one would figure that it's better than what you get with flourescent lights.
I've replaced many of the lights in my apartment with compact flourescents. Typically, a CF bulb that outputs as many lumens as a 100 W incandescant bulb will only require 20 - 30 W. Reading a newspaper with a 20 W incandescant isn't practical, but the 20 W CF is more than bright enough.
b&
All but God can prove this sentence true.
This was also featured on Talk of the Nation on NPR last week. It is worth a listen.
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Oh bother.
Here's a quote from the Web Site:
I should point out that a single WLED provides sufficient light to easily read a book or to study with. My wife, who wholeheartedly assisted me in Nepal in 1999, has amassed ample field evidence to support this last statement. It is very significant to the developing world that these wee marvels of technology can effectively light an entire kitchen table area using less than one watt of electrical power and there are none of the attendant dreadful pollution and fire dangers associated with the use of kerosene lamps.
Please read more of the web site before commenting. /Don
What you do not realize, judging by your post, is that the average 20 mA white LED looks brighter than the average 40W 120V bulb. A single one makes an excellent flashlight. A few of them together make an awesome lightsource.
I wouldn't be suprised if a 100W bulb only produced 1W of visible light.
It's usually around 3W. IIRC, flourescent runs around 25W.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
I work in the lighting industry with conventional means of producing light (florescent, incandescent, etc) and have done some testing on LEDs. The most important thing to realize is that the light being produced is not a pure "white" light.
Typically the manufacturer will use a blue LED and coat the outside of the lens with a yellow broadband phosphor, which when the blue light is filtered through it, appears white. True white is extremely difficult (and expensive) to produce; it's still years away and it has to do with the ability of the diodes to produce certain wavelengths of light.
As far as efficiency, yes, LEDs are quite effecient at producing light at a given (low) wattage but they are still not as bright as conventional light sources. The rating of an LEDs efficiency is measured in lumens per watt; a bulb with a higher lumen per watt rating is more efficient than that of a lower one. At this point, red LEDs are the most efficient, which is why many applications that use LEDs (exit signs, car turn signals, etc) are red.
Manufacurers claim a 100,000 hour life span of LEDs. What most of them fail to mention is that to acheive this, the power supply that the LEDs are attached to has to be set at a low current. Low current means decreased brightness. If the current is increased past the manufacurers recommended setting, you will get higher brightess but the lifespan will be cut short severely. Not to mention the fact that many LED applications where companies are touting 100,000 hour lifetimes (approximately 10 years) haven't been around that long to confirm or deny it.
LEDs are not going away, however. It's not a question of if they go mainstream, it's when. And I have no problem with that, it's just that from what I have observed, the manufacurers are dispensing half-truths and outright lies about this stuff. People take it for gospel because big companies are developing the technology (GE and HP-funded Agilent come to mind) so they figure it must be true.
Whatever. It's reall not going to make that much difference in the long run. Just want people to know there's more behind it.
The neutrality of this sig is disputed.
The problem with white LED's is that they can be inconsistent in their color. If you will recall they are made by placing a small amount of white phosphorus on the light emitting element of a high powered blue LED. When the phosphorus is bombarded by blue photons it emits photons that make up the rest of the visible light spectrum. The issue with manufacturing white LED's is that it is difficult to make white LED's that are consistent in their color and brightness. Too little phosphorus and the LED's light can look a little blue. Too much phosphorus and the LED is dimmer than a good white LED. If the phosphorus is placed off center the light produced by the LED varies in color and brightness. Of course their are grades of LED's, but the higher quality LED's cost more. Some people in developed nations might find these quality variations unacceptable. Now don't get me wrong there are some places where I could stand the inconsistencies of white LED's, like in a garage, a hallway, or some other room where tasks are done that do not require the color to be consistent. I would find it annoying to have inconsistent light in some place where I would be reading though. For that matter while I cannot be sure as I do not use makeup, applying makeup might be difficult in light that has color and intensity variations.
Impersonating Tycho from Penny Arcade since before there was a PA.
Frankly, I suspect we'd do more for the developing world by adopting this sort of thing for ourselves
A quick Google search turns up The LED Light, and they have a collection of "bulbs" that fit into 120 Volt AC sockets (That would be them things in yer house, at least in the US)
Very expensive though - "36 LED bulb...comparable to a 30 watt incandescent bulb" costs $190.
Another site I've run into in the past is LEDTronics which looks more in line with the geek need for way too much information, and component-level purchasing. I can just see the mod case now...
Last year, the numbers were something like this;
.sig
Lumens/Watt;
85-95: 32 watt T8 fluorescent
60-65: standard F40T12 cool white fluorescent
48-60: compact fluorescents
20: T3 tubular halogen
15-19: white LED
17: standard 100 watt incandescent
6: incandescent night light bulb (7w)
6: incandescent flashlight bulbs
The very best white LEDs are still under 35 lumens/watt, or about 1/2 the efficency of a flourencent. They have been steadily improving however, and around 2004 should surpass them.
But not today.
-- this is not a
After hunting around for a reasonably-priced reading spotlight to mount in the minivan for my kids to read after dark, I couldn't find anything that was (1) bright and clear at low wattage (2) priced under $100US (3) small enough to hide in the trimwork. Then putzing around Radio Shack one day, I saw the rack of white LEDs, and decided to give them a whirl.
I bought 6 WLEDs for about $30, a couple 100-ohm resistors and 1K trimmer pots for current limiting and dimming, and went home. Half an hour and a few solder joints later, I had mounted the 6 LEDs shining thru holes in my overhead panel, pointed at my steering wheel area (hey, first I helped MYSELF, not the kids). I found that I could run three LEDs, with a voltage drop of about 3.5V each, in series with the fixed 100 ohm resistor and a trimmer pot. So two sets in parallel worked well. I couldn't wait until nighttime.
After dark, out to the van I went. Switch on - WOW.
First impression - the color was all wrong. Until I realized that I'm so used to yellow light that pure white was almost distracting. But the light was BRIGHT and very crisp. From about 18 inches from LEDs to reading material, with only 6 LEDs, I had more light than with the original dome light 20 inches away, and the color was perfect - I could enjoy reading material with photos, without straining to see the colors. The pool of light was about 15 inches across. The LEDs I used are rated at 30deg beam spread (to the point of half brightness) so that seemed about right for six lights pointed a bit apart from each other. Best of all, unlike a dome lamp, there was NO spillover light to the rest of the interior - with the light on I could still easily see out the front to drive. Don't try that for long with a glaring dome lamp.
One other thing was worth noting - there were faint yellow/blue bands in the pool of light, noticable only when looking at a large mostly blank page. This is probably due to the blue LED/yellow phosphor combination used to make white light.
The biggest problem was cost. At Radio Shack prices of $4.99 each, I couldn't affort enough LEDs to do the other five seating locations. But it was still far cheaper than a quality aircraft-style reading lamp, and just as bright. If I wanted more brightness, I can easily add more LEDs.
Check out this link - http://www.theledlight.com - for some really cool ideas, parts, kits, assembled lamps, all based on LED technology. Really cool, and a LOT cheaper for the bare LEDs than Radio Shack. About $2.50 or less each.
Soon I'm going to order some bulk WLEDs from them - and light up the rest of the vehicle interior.
--Brandon / Split Infinity Music
This place offers 17 led bulbs(comperable to a 25w bulb) for $39, but they wont sell to developed nations(usa).
This place has 20 led bulbs for $60.
here is a place that has dimmer(?) bulbs for 30-35 bucks.
here are some really cool sunlight powered outdoor led lights for $80.
We have the best government that money can buy.
Check out http://www.arcflashlight.com
The Arc AAA is a great little light that is very rugged, waterproof, runs off a single AAA battery with good longevity (using a step-up voltage regulator) and *very* bright. I have a couple of these - been carrying one on my keyring for about 6 months and its never failed me. White LEDs are great..
They're used quite extensively as backlights for industrial equipment, I know some of the newer Fluke multimeters use white LEDs to backlight the display for nighttime use. Also, Gameboy Advance has outboard white LEDs that you can plug in the link cable slot, and I'm pretty sure some geek case modder types have installed white LEDs in their GBA's.