LED Guru On InGaN-Based LEDs And The Future 116
Mayor Quimby writes: "EETimes reports that LED guru Shuji Nakamura predicts
White LEDs to overtake the light bulb
Mr. Nakamura is an amazing guy who is given substantial credit in the
development of blue and white LEDs. Other articles about him can be found
here and
here.
He "works from 7 a.m. to 7 p.m., 355 days a year, and says he has never taken a vacation." Also, check out this circuit board
found in an LED flashlight that uses a single AA battery. It'll be nice when low cost knockoffs start flooding in from the Far East." I can vouch for the life of white-LED flashlights -- the ones I purchased more than a year ago from Holly Solar are still on their first sets of AA batteries. Not as bright as incandescents, but plenty for lighting up a tent or to keep from stumbling on a trail.
355? (Score:4)
Back in MY day, we worked all 365 days of the year.
Traffic Lights (Score:1)
LEDs are the wave of the future (Score:2)
If you combined this with a transmeta chip, the power savings would be enormous!! If one of those regenerative keyboards was thrown into the mix, these things would last forever.
my experience with LED Lights (Score:5)
Anyway, the LED lamp uses three white LED's and doesn't put off anywhere near the light of the 2-AA princeton tec with a standard bulb. However, by way of comparison, it produces a more disperse light and it will last up to 150 hours on a single set of batteries, compared with 6-8 on the Princeton Tec.
The light is certainly whiter than most anything but maybe a xenon bulb (which uses tons of power). It has virtually no range, though. It lights up a nice hemisphere in front of me for a good 6 feet whereas the carbide and Princeton Tec can send a light several dozen.
I keep thinking that if they made a headlamp that had so many LED's in it that it sucked as much power as the standard bulb, it would be fucking bright indeed.....
Oh yeah, and the Tikka was almost $40 and the Quest was $15.
Re:my experience with LED Lights (Score:2)
And here [karstsports.com] is my Princeton Tec.
Yes, the Tikka is the 3 white LED lamp.
Thank LEDs for laptops! (Score:4)
Re:Traffic Lights (Score:1)
Re:my experience with LED Lights (Score:1)
I've been carrying a Mag-Lite around in my backpack for years, and something that was smaller, weighed less and lasted longer would be awesome. If voltage is important, you could just use three smaller cells, but if it isn't, you could just run off one "D". The extra LED's might also come in handy, but I kind of wonder if that isn't more available, if at all, because of diminishing returns and/or the sticker shock it would cause?
Re:Traffic Lights (Score:1)
Re:Traffic Lights (Score:2)
Yup, and 'round about these parts (San Francisco peninsula), they're starting to retrofit the green traffic lights as well, and man that shade of green is gorgeous to behold...
Schwab
Re:my experience with LED Lights (Score:1)
This site has some interesting looking lights. Especially the 7 LED custom Petzl headlamp, which is unfortunately (1) expensive, and (2) out of stock. [glow-bug.com]
I don't own any of their products, but was thinking of buying one of the various headlamps.
Regards
-Jeremy
Re:my experience with LED Lights (Score:2)
In any case, check out the link in the article..they make flashlights in the $20-$50 range it seems. I'm sure they're pretty decent, but LED flashlights are a different beast than incandescent. You don't get a spot of light surrounded by a really diffuse yellow the way you do out of a normal flashlight like a Mag. You kinda get all the light spread over a much wider range. The reflectors seem to do very little in focusing the light..I don't know why. As such, you don't get the same range out of them.
In any case, I personally don't like mag lites. Princeton Tec actually makes some wonderful incandescent flashlights that are small, powerful, and extraordinarily reliable (you can't imagine how hard caving is on gear like an extra small flashlight or bottle...you know those really hard Lexan Nalgene drinking bottles? I broke one a couple weeks ago..imagine doing that to your Mag...after you've had it submerged in water for a couple hours).
Er..anyway..I don't know if it works with incandescent flaslights, but using lithium AA or AAA batteries (energizer makes some) can easily more than double the expected life out of an LED lamp.
For a wider selection of LED flaslights check out http://www.karstsports.com/ledlights.html (yes, I like the store..sorry, I find it immensely useful and cheap with invariably good products). Enjoy.
Let Light Loose (Score:3)
Lovely LED's letting luscious luminence lift lonely lives. Light leaves love's lost luminairies lamenting, languishing, listlessly listening lest loveless labor limit life.
Lo! Love leverages light. Light limits love. Love learns light lessens lucidity. Loss lies lurking, luring lovers 'long looping lanes lacking love, leaving little. Less. Lust.
-Intense introspection
-Into interesting interpretations
-Involving intellectual indulgences
spectrum on these? (Score:2)
Cuz I was thinking, no heat and low power, these would make good grow lamps . . .
Fire Jon Katz. Hire Neal Stephenson. (make this your sig too)
All about LEDs (Score:5)
LED museum [att.net]
No Need for "Brighter" Buttons (Score:1)
Not only traffic lights... (Score:1)
Re:No Need for "Brighter" Buttons (Score:1)
household lighting (Score:3)
I guess you'd need a lot more LED's (or banks of them) then bulbs. Since LED's are also DC beasts, you'd need to convert to DC with a rectifier circuit from the standard 110 VAC. I guess this would be best done once (instead of having a rectifier at each lighting location), and seperate 5 V (or 12 V or whatever) circuits for lighting only done throughout a house. This would be best applied to new houses only. Having a seperate rectifier at each light location (i.e. to replace traditional bulbs) would probably be wasteful and expensive.
Re:No Need for "Brighter" Buttons (Score:1)
Why LED lights might not take over (Score:2)
So why haven't floresent light taken over?
The light from floresent lamps is, emotionally speaking, "cold" and "unpleasant". I have an Inova light [inovalight.com] (a cheap clone of the photon light), and the light from it by itself is cold and harsh compared to tungsten lights.
- Sam
Re:Traffic Lights (Score:1)
Starting to change traffic lights over to LEDs in the UK as well, as far as I can tell. (A few round my area in London starting to appear for sure). Very bright.
This is really for those hard to reach places (Score:3)
Similarly, think about lights in places where they are difficult to replace. Embedded lights in offices come to mind. Anywhere were work has to stop to replace a light, it makes sense to pay $30 for a bulb. In the home, on the other hand, the cost of replacement is negligible. So, LEDs probably won't take over until they are almost as cheap as standard bulbs. On the other hand, I'd love to replace the pool lights with LEDs, because I have to lower the water level, which is a complete pain, to replace those lights.
Thalia
Next hurdle - omni-directional LED lighting (Score:5)
Now that I'm done with links - I'll say this - while LED lights are great for directional lighting, they are not good at all for omni-directional lighting. This is because the reflector is housed inside the LED itself, and the light will always be facing the direction of the LED plate.
Now... I wonder how difficult it would be to get that LED plate inside the plastic/resin housing into a shape of a cylinder, and install it in place of a standard tungsten filament? If that is possible, then the LED light will truly be able to replace all lightbulbs... Not just the directional ones.
Hmm, I guess I don't have much to say other than the good links up top, and my hope for tomorrow's LED, household lightbulb. If you experts have something to say about the possibility of the cylindrical LED plate, I'm all ears. I surely don't know if it's possible or not.
White LEDs are nothing new ... (Score:1)
Re:my experience with LED Lights (Score:3)
Re:This is really for those hard to reach places (Score:1)
Re:355? (Score:1)
That leaves about 45 days a year of ACTUAL work. Oops, I forgot
CREE and Nakamura (Score:1)
I read this article a couple months ago and I haven't heard anything about it since. None of the articles given in the story mention anything but his professor job. Is Nakamura working for CREE or not?
very true (Score:1)
A strange idea from timothy (Score:2)
Why? Because the product you end up with will be flimsy? Because you'll have to return the first three before finding one that works? Because the company that developed this product will stop receiving any return on their R&D? Because your Uncle is some slave-labor king in Malaysia? You sure won't be "vouching for the life" of any low-cost knockoff.
If you think about the success of the MAG light, you will realize that low-cost knockoffs probably wouldn't even be attractive to most people.
The Infinity task light linked to is a good little light. If I could only have one LED light it would be the Photon Micro Light, but the Infinity is still a good option if you don't want to use button cells. It could benefit from some reflective material around the LED perhaps, as the light output is much less than the Photon. Maybe I'll polish the metal around the LED... hmmm.
Is this really a white LED? (Score:2)
>> over his blue chip to get a white light."
Is this really a white "LED"? Sounds like a blue
led activating phosphorous to me, which hardly
seems would be the holy grail.
Don't get me wrong, it's great about Nakamura
developing the blue led, I just don't think we
should call this a white "LED".
LEDs on Late Night Radio (Score:2)
Of course, these were very popular among certain folks who were stocking up for the Y2K crisis last year. (Everyone who remembers the end of Western Civilization, raise your hands).
Actually not a bad technology, but a little pricey if you do not have a real need for it.
C. Crane [ccrane.com] company has some cool things, although they are more oriented towards the radio geeks
Re:household lighting (Score:3)
An L.E.D. does not have a filament to "heat-up" and thus there is not lost energy, making L.E.D.s approximately 3-5 times more efficient than incandescent bulbs.
I wonder how it compares with flourescent power wise.
Is it wasteful & expensive to have all that circuitry? If LEDs really do get 100,000 hours of duty use, that's 100-200 TIMES the claimed life of incandescent, so for every LED unit you toss in the trash, that compares to maybe 150 glass bulbs in the trash. Flourescents are claimed to get maybe 10,000 hours.
Re:household lighting (Score:3)
Still, even with conversion circuitry, that's pretty cool. Many don't like the slow startup times and colors of flourescents, many are used to the "warm" color of incandescents to use in the home.
Re:This is really for those hard to reach places (Score:2)
Alex Bischoff
Alex Bischoff
---
Re:Next hurdle - omni-directional LED lighting (Score:2)
Re:This is really for those hard to reach places (Score:1)
real-world uses of LEDs for lighting (Score:2)
Re:Let Light Loose (Score:2)
Seek social surroundings.
--
Re:This is really for those hard to reach places (Score:4)
On a related topic:
40 Hours My Arse (Score:2)
A standard incandescent bulb will typically burn out in less than 40 hours.
That sees a little bit low to me... unless you mean 'standard' being the homemade lightbulb created with a vacuum pump and a piece of yarn.
Re:very true (Score:2)
-Nev
not really (Score:1)
Re:355? (Score:1)
In MY day we worked 365 and 1/4 days a year and we liked it!
Re:spectrum on these? (Score:2)
here [att.net]
Aircraft Landing Lights (Score:1)
Re:household lighting (Score:2)
________________________________________
Re:very true (Score:2)
Re:my experience with LED Lights (Score:1)
No way (Score:1)
Re:my experience with LED Lights (Score:2)
My impressions on the White Light LED...
Very Energy Efficient
Very diffuse unfocused light source
Gives you awesome side vision
Don't go very far, because it is not a focused light source.
Great in the tight crawls of NY caves
Suck in large rooms, since they are so diffuse (WV Caves)
Suck when trying to look though semi cloudy water, Blue scatters better than RED turning water milky white. (Most NY Cave Passages)
Incredible battery life
Carbide is still the way to go...
When the white light LED's hit the market a few years back, I a grabbed the spectrum of one off of a Monochromator at work [acton-research.com]. The White LED's are a Blue Light LED with a Phosphor placed in front. Most of the Energy is emitted in the Blue (that's why the light looks so cold) and excites the Phosphor, which emits light in the other color ranges. I did notice from the trace that LED's have almost no RED component. Wish I had some of the trace data with me, I would post it. The Real trick for LED's is to push them farther and farther into the Deep Blue and UV, If you could get a device to emit at down around 253nm you could basically make a low voltage ballast free high efficiency light replacement that lasts 10,000 maybe 100,000 hours (1 to 11 years continuously on). Compact Low power UV light sources would be very nice, (though I question how long they would last working at 193nm and 157nm (the Photons have enough energy to start breaking atomic bonds in the substrate and window)).
TastesLikeHerringFlavoredChicken
Workaholic (Score:2)
Yeah fellow Japanese and Chinese are traditional workaholists. But frankly I believe that our fellow americans and europeans have also such epidemy catching their lifes... At least some friends say things like "sorry I'm in the 14th hour, going to sleep". So I don't think that workaholism will made his LEDs shine brighter...
LED + Mirror projectors will kill the CRT(finally) (Score:1)
Re:spectrum on these? (Score:1)
TastesLikeHerringFlavoredChicken
LED's inhibit aircrash post-mortems (Score:2)
LED's are terrific. Increased reliability, higher efficiency, lower power consumption, higher peak output, and better heat dissipation.
BUT, one 'negative' side effect of greater LED usage is the NTSB will have less forensic evidence after aircrashes (at least with smaller private planes without a flight data recorder)...
At moment-of-impact, the filament from a lit bulb breaks apart differently from an already-burned out bulb or from an operable-but-not-lit bulb.
Here's an article that describes filament analysis. [harristechnical.com] And two reports, one where LED's prevent filament analysis (search for "filament analysis") [http] and another where analysis showed the status of indicators (search for "filament stretching") [erau.edu]
Slightly off-topic, but interesting, I think.
Re:Traffic Lights (Score:1)
Re:If anyone remembers... (Score:1)
They were mostly written by Arthur C. Clarke's co-writer.
Re:A strange idea from timothy. (Nope, and Yup.) (Score:1)
a) that's not my idea, it's Mayor Quimby's. All I did was post his story.
b) But I would like to see cheap knockoffs in the hopes that several years down the line the overall quality and variety of LED devices available would be greater.
Just like all the Japanese companies which currently are renowned for high-quality products (Nikon, Honda, Seiko) were correctly considered imitators for a long time, but aren't now. They made (cameras / cars / watches) of acceptable quality cheap, and quickly ramped the quality up. Hondas today are high-quality, low-maintenance, reasonable price -- a net customer benefit. (I say that as a Ford owner with what is basically a Mazda engine.)
So. Wasn't a strange idea from timothy, but now it is.
timothy
Re:spectrum on these? (Score:1)
Re:very true (Score:1)
Re:spectrum on these? (Score:1)
I don't know what you've been smoking, but green is precisely the color you don't need. Red is probably the color you're looking for, but the reality is that plants not only absorb in various spectra, but the required range can vary somewhat between species. Did you know that not all chlorophyll is created equal?
There are photochromatic analyses that have been performed on chlorophyll absorption (and there is more than one type, found in various ratios in plant materials), but even that data doesn't entirely match up with experimental results.
What I want to see is someone producing LED clusters which target specific frequencies needed by plants, without wasting energy on the unused light spectra. And even then I'll want to see solid experimental data backing up its effectiveness.
Stimulated emissions (as in flourescent) might be the only way to adequately spread the incredibly narrow frequency of LEDs into a broader, more useful spectrum.
Our eyes are have only three color sensors (Score:2)
LED's are not going to do well in home lighting for quite some time if ever. Fluorescent lighting is more efficient, reasonably color balanced, and much much cheaper per lumen output.
(Insane_work_ethic == BAD) (Score:3)
He "works from 7 a.m. to 7 p.m., 355 days a year, and says he has never taken a vacation."
And this is supposed to be a good thing? Obsessing about anything to the verge of lunacy, and sacrificing all the other things that really make life worth living, is hardly a healthy way to live. The quality of life on this planet is only going to get worse as long as people keep praising this kind of unreasonable work ethic.
Re:household lighting (Score:2)
But flourescents have that insufferable strobe effect and lack the pure white color of the led. I don't think you could embed flourescents in epoxy to make them impact-resistant.
"Free your mind and your ass will follow"
I can't wait for LED Christmas Lights... (Score:1)
No patents for you Big Guys, it was posted here on Slashdot first...
They're DIODES - let them rectify (Score:1)
I tend to use amber high-brightness (6.5 candela) LEDs because they'll run off 2xAAA with no electronics other than a weedy resistor. Inserted into one of those glasses-like head lights instead of bulbs, I can run them for months on the batteries that won't work in my pager.
Vik :v)
Re:Our eyes are have only three color sensors (Score:1)
Re:CREE and Nakamura (Score:1)
Re:40 Hours My Arse (Score:2)
This reminds me of another factor for incandescent longevity: power. A 40 watt bulb doesn't get as hot and will last far longer than that 100 watt bulb.
I once read about a 40 watt bulb at a firestation that burned continously for 16 years! Does anyone remember a primary source of info for this? It may have been one of those yellow sodium jobbers which are possibly the longest lived incandescents of all. When using low power and continous duty cycles, incandescents can last a long time indeed.
Come to think of it, 40 hours was the amount of time the first practical incandescents lasted. This was over a hundred years ago and I do believe they have perfected them somewhat since then!
Of course, none of this addresses being dropped and moved about. Even a 40W bulb is a power pig compared to an LED unit that may be far brighter and efficient using less power.
Re:I can't wait for LED Christmas Lights... (Score:1)
only 4.3 watts (as compared with the small incandecent sets that take 210watts/100).
The voltages at which a standard LED operates
would allow for 70 lights/segment (as compared
with 50 incandecent bulbs/segment).
--
Downsides include:
The cost. LED's can cost anywhere from $.12 to
$.30/each for high brightness ones (in quantities
of 1000).
As LED's are solid state devices - all the LED's
need to be oriented with the same polarity for
the string to function at all.
--
I built a string of 100 using a dead incandecent string (containing two segments of 50 bulbs each)
using red,green and yellow LED's, (2) 2000ohm resistors, and (4) 1n4007 diodes as a bridge rectifier. It requires only 36mA for the entire
string.
Re:spectrum on these? (Score:2)
Am I crazy, or does that have implications for long-term space flight?
Re:Is this really a white LED? (Score:1)
Save the "white light emitting diode" for a P-N junction that emits white light.
Re:This is really for those hard to reach places (Score:1)
Say what?! I've never seen a traffic light that didn't follow the top/left rule. If it's vertical, red is at the top. If it's horizontal, red is on the left. I'd imagine exceptions are rare indeed. What cities/towns have traffic lights that don't follow that rule?
Re:This is really for those hard to reach places (Score:2)
See, you learned the world is bigger then you thought today.
Re:This is really for those hard to reach places (Score:1)
Reflectors (Score:1)
What, not use 90% of the energy to make heat? (Score:1)
Actually, I was very recently involved in a project using this technology (which I believe used Nichia's instruments). The idea was to use an array of white LEDs bounced off a secondary reflector which could be repositioned for focusing a la Maglite. We did run into a number of difficulties in reflector design, but I believe this technology is certain to take off. A funny point to Shuji Nakamura's statement that:In testing an initial mockup, we managed to make six LEDs run off a pair of D-cell batteries for over two weeks without a loss in performance! Might be time to sell off that stock in Duracell...
Re:355? (Score:1)
But you try telling the kids of today that and just won't believe you.
led and mags (Score:1)
sorry, but when it comes down to ass-whoopin', mag does an amazing job, i guess that's why even cops are using them. i've never clubbed anybody over the head with same efficiency as i did with mag-lite.
heck, yes, i'd love to have an LED flashlight with the magnitude and ass-whoop-power of a 4-double-d mag-lite
Re:LED's inhibit aircrash post-mortems (Score:1)
I dont think so, Tim. (Score:1)
2. LONG LIFE: The light emitting portion of an L.E.D. has a 100,000 hour life span. A standard incandescent bulb will typically burn out in less than 40 hours.
Really? I can't think of any light bulb I've ever had that lasted less than a few weeks (and yes, I realize that means hours of on-time). Someone is buying really bad light bulbs!
Geoff
Re:household lighting (Score:1)
Here's an idea - just put a few dozen LEDs in series in one direction across the AC line to match the forward-bias voltage of a hunder-some-odd volts. Do it twice, in parallel, with the second string connected the other way to it lights on the other half of the AC cycle. Do this all on one chip (a few dozen LEDs on one chip, like millions of transistors in a CPU). Now you have a direct light bulb replacement. No fancy power supplies, extra electronics, or extra cost.
All royalties gladly accepted.
Re:This is really for those hard to reach places (Score:1)
Re:household lighting (Score:2)
Re:household lighting (Score:2)
Re:household lighting (Score:2)
Why LEDs? (Score:2)
Tesla bulbs.
These bulbs work in a similar fashion as a flourescent bulb. Essentially, the bulb looks like a normal bulb, but with a wire running up the middle in a glass tube, tipped with a small metal sphere. The inside of the bulb is "coated" with a material that flouresces in the presense of intense radio waves. When Tesla was experimenting with them, simply holding one in the presence of a Tesla coil was enough to get them to light, but they were really meant to be "directly" connected to the Tesla coil output.
IIRC, Tesla's original bulbs weren't very bright, but they showed the concept well. Later inventors have experimented with the system, and built bulbs in which the Tesla coil formed part of the "filament", with some of the electronics in the base of the bulb - meant to be screwed into an ordinary socket and run off of normal houshold current. These bulbs were much brighter, and supposedly last for over 50 years of continuous operation.
I don't know if they were ever manufactured on a large scale. They were VERY expensive, supposedly costing over $30 each, but given their longevity over ordinary bulbs, this wasn't a real issue. They were meant for commercial installations, where changing a bulb was difficult or dangerous.
Does anyone know more about these bulbs, and whether they still exist (I tend to wonder if the new compact flourecents have taken over)?
Worldcom [worldcom.com] - Generation Duh!
Re:household lighting (Score:2)
Re:Thank LEDs for laptops! (Score:2)
And, of course, the big bank of neon lamps that would come on to indicate a low battery state.
Fortunately, small plasma discharge lamps like neon indicators are almost as efficient as LEDs.
<grin>
Japanese white light? (Score:2)
This won't be the first time that the Japenese help the White LED (the third letter stands for death). I seem to remember a little incident called World War II.
I think the Japanese got to see more than enough white light during WWII. Maybe that served as the inspiration for the white LED?
Around here, most Jews seem to drive German cars; most Chinese people seem to be driving Japanese cars.
Personally, while I wouldn't touch a Japanese car with a ten meter cattleprod, but speaking as a former tech at a TV station, no one has ever made a better TV set than Sony. As long as the Japanese allow North American manufacturers to sell their products there, I have no problem with the Japanese selling their products here. Competition and innovation are mutually beneficial.
Forgiveness is an interesting thing. And a good thing.
Re:spectrum on these? (Score:2)
Any one have any info about the range of light they put out? Cuz I was thinking, no heat and low power, these would make good grow lamps
I think most (ahem!) herbs grow best under a greenish to bluish glow light. You should be able to find that out for sure in any good book on amateur hydroponics... Grow lamps, for example, always seem to be a more blue-green glow than an ordinary fluorescent tube. And incandescents don't seem to do much at all.
If that's the case then, don't bother with an array of white LEDs. They're incredibly expensive. Instead, go for an array of blue (still expensive) or green (common) LEDs.
Hi-intensity green LEDs are fairly available, just quickly checking the back cover of my Digi-Key catalog, you can buy Panasonic green clear LEDs in T-1 3/4 packages for $199.70 per thousand pieces. At 20mcd @ 565nm @ 30mA @ Vf=4, they might grow plants pretty well, if you have enough of them. (There are far more intense and efficient green LEDs out there, I just flipped over a catalog.)
There are also 1500 mcd blue LEDs available from the same source (www.digikey.com). On my older Canadian edition of their catalog, the 1500 mcd blue LEDs put out at 470nm, If=20mA, Vf=3.5V. Panasonic part # LNG992CFBW, if you wanna check out the datasheets on their website. A thousand of them will cost you over three grand.
It would, for sure, be an interesting project. Remember to budget for a large DC power supply to run these, as well as homebrew PC board to wire all these, because you're sure as hell not going to do it by hand.
LED Lighting in Space - a prediction. (Score:2)
Am I crazy, or does that have implications for long-term space flight?
You're probably crazy, but yes, it does.
Fluorescent lights are not as efficient as LEDs, though they're still more practical for the moment. And they're bulky, the ballasts are heavy, and they're fragile. The LED will first see general lighting use in space, but I don't think it's ready for that yet.
And yes, it's another one of those evolutionary improvements that will improve the technology of space travel. I'm still holding out for the revolutionary ones, like superluminal travel and gravity manipulation.
White LED Notebook Backlights are here now (Score:2)
Actually LED screens would be pretty sweet, if they could build them pixel-sized. They're bright, don't require crazy voltage like back-lights do, refresh super fast, black blacks and white whites....
White LEDs are already being adopted as replacements for the fluorescent tubes or electroluminescent sheets being used as notebook backlights. You can now get large (notebook display sized) sheets of frosted white plastic with white LED junctions embedded for use as backlighting in new notebooks. It will basically work like an electroluminescent backlight but without the inefficient and failure-prone inverter. I saw them advertised in an electronics engineering trade magazine that I get.
Re:household lighting (Score:2)
Do this all on one chip (a few dozen LEDs on one chip, like millions of transistors in a CPU). Now you have a direct light bulb replacement. No fancy power supplies, extra electronics, or extra cost.
Nope.
While you're right about the LEDs in series - especially since the diodes would then protect themselves from being reverse-biased beyond their PIV ratings, this isn't practical.
The problem is that LEDs are still less efficient than a comparable semiconductor junction. While it's easy to build a rectifier diode or other power semiconductor that will stay cool in a small package, an LED is a special case because it has such a high voltage drop. Most of that energy does leave as light, but some as heat.
Getting heat away from a power semiconductor's silicon die can be tough enough, without the added problem of diffusing light away from the junction in such a way as to be practical as well. It's just not going to happen.
Re:household lighting (Score:2)
you'd need to convert to DC with a rectifier circuit What you talkin' 'bout, Willis?
Actually, you do want to be careful that your diode string has a peak reverse voltage rating greater than the AC to which you're going to connect it.
For this reason, it's prudent to include a 1N4004 or better in series with your string. As with any diodes, when LEDs are reverse-biased and you exceed their breakdown voltage, the current quickly runs away and the diode fries. The maximum allowable reverse current of LEDs is generally much lower than most other kinds of diodes.
Re:Light Emitting EPROMs (Score:2)
I have always preferred Light Emitting EPROMs, though they're a lot more expensive and don't last as long. (plug one into your breadboard backwards)
Or try programming it on the wrong voltage. (Ooops.)
Re:A strange idea from timothy (Score:2)
If you think about the success of the MAG light, you will realize that low-cost knockoffs probably wouldn't even be attractive to most people.
Thank you.
Just when I was starting to despair over the fact that some people think Wal-Mart is a perfectly reasonable place to buy a VCR and flimsy disposeable cars like Hondas and Toyotas choke the roads around me, it's nice to see someone else who still respects that "100% plastic-free" school of product design.
I keep a MAG light in my glove box. It comes in handy when I need to use my 24-year-old pickup truck to jump-start my boss's Integra, which won't start when it gets below 10F outside.
I go out of my way to buy the real thing, not the crappy made-in-Taiwan knockoffs.
Re:A strange idea from timothy. (Nope, and Yup.) (Score:2)
Hondas today are high-quality, low-maintenance, reasonable price -- a net customer benefit.
Sure. Disposable and expendable, like their owners.
Uhh... Unfair comparison. (Score:2)
So that's my car. It's messy right now, need to clean it and would if it weren't raining here. It's not flashy, but the tape deck works and I have a nubby cover on the steering wheel
Listen, I'm not a Saab fan, and I'm not an Escort fan. Neither is a car that I like.
But to compare the reliability of a 14 year old turbocharged luxury car against a 5 year old econobox is patently unfair.
Because of its age, it's probable that the Saab had more miles on it. It's also probable that the Saab, being a turbocharged alleged sports car was also driven harder. It's a luxury car, too - more complicated, with more things to break or wear out.
And, it's definite that because the car was nine years older than the Escort, there was a lot of decay to little things that nickel-and-dime you to death unless you know how to fix them yourself. Insulation on wire decays. Rubber breaks down. Gaskets dry up. Contacts get corroded. Keep your Escort around another 9 years and you'll learn all about that.
I drive a 24-year-old Dodge Ram pickup truck. The other day, the connector to my voltage regulator failed. It was corroded. The regulator didn't have a reference for the voltage on the battery, so it assumed the battery voltage was zero, and therefore pegged the charging current. +50A charge on my gauge - I pulled over as soon as I could, because my battery was boiling and my electrical system was running at 22 volts. (Only blew a headlight, though.) I pulled out my multimeter, checked a few connections against the service manual (kept stashed under the seat), found the bad connection, cleaned it with a pencil eraser, and the problem was fixed.
This is the sort of thing that will happen with *any* older vehicle. Period. There's no escaping it. If you like older vehicles and choose to drive them, you have to know what to do and be prepared to do it.
It's nice, though. Driving older vehicles has taught me to be resourceful, a skill useful everywhere. And I can diagnose a problem quickly, and have a lot of practice in assessing the severity of a situation.
The truck is insured for liability only, and pickup trucks are cheap to insure. $34/mo gets me $1,000,000 coverage in a city almost as big as Chicago. Besides that, I'm not paying out monthly car payments, so that money can instead go to fund other things - like a 401(k).
And besides, I just like the thing.
With a good tune-up, my truck is also the only vehicle I know that doesn't need to be plugged in to a block heater on a cold winter's night - it'll still start, first shot, on the coldest morning of the year. I frequently have to jump-start my boss's 2-year-old Integra. Why? Because, while my truck may be crude, it was built to last, and I take good care of it. The Acura was built to perform flawlessly for the first 100,000 miles and then be scrapped.
My truck gets an oil change - cheapest 10W30 oil and filter I can find - every month (3,000 miles). Every month, I also pop off all the wheels, check the brake linings, lubricate the parking brake cable with silicone grease, check the wheel bearings and balljoints looking especially for looseness or torn dust boots, and grease all the suspension. Takes about 2 hours every month. New air filter if it's visibly dirty or every three months, whichever comes first. I clean and regap the spark plugs every three months, checking the compression, timing and vacuum advance at the same time. (I'm impressed with the Bosch Platinum plugs I put in early this summer!) And while I've got the motor warmed up and I'm in my coveralls, I pop a vacuum gauge on the old Carter BBD carburetor and balance the metering rods, and re-set the idle.
Every fall, I spray another coat of paint on the underside of the body to prevent the floor and frame from rusting in the salty wet snow. Every week when there's snow on the ground, the whole underside gets washed off with hot water at a car wash. And every summer, I set aside at least one project that I'd like to do, usually because I enjoy them. Last year, I gave my truck the gift of air conditioning. This year, I'm going to repair some old rust damage on the truck, replace the windshield (there's a small chip in it), tap a couple of small dents out of the body and then treat Methusulah to another coat of Chrysler Forest Green Metallic paint.