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LED Evolution Could Spell The End For Bulbs
An anonymous reader writes "USA Today is running a story discussing how LED lamps were unthinkable until the technology cleared a major hurdle just a dozen years ago. Since then, LEDs have evolved quickly and are being adapted for many uses, including pool illumination and reading lights, as evidenced at the Lightfair trade show here this week. More widespread use could lead to big energy savings and a minor revolution in the way we think about lighting."
I just bought a keychain LED flashlight today, because they last forever on one of those little watch batteries. I wouldn't want them for home lighting though. It's such a weird shade of white, like blue-white. It would drive me nuts!
I know that this is true because I read it in the Bible. They did not evolve, they were created by God.
I guess we are going to start having "illumiphiles" who will try to tell us that the incandescent lightbulbs of yesteryear are somehow "warmer" and that humans can tell the difference between LEDs and vacuum tubes.
an illuminating article...
--- Asking inconvenient questions for over 30 years...
I'd buy them for that capability alone.
I wonder when we might see LEDs with enough brightess to serve as a projector lamp?
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
the lightbulb industry lobbies the congress to ban LED technology that will ruin the market for lightbulbs.
Dvorak on Doomtech
For starters: LEDs aren't as efficient as many people seem to think, iirc they're a bit more efficient than normal lightbulbs, but TL-lamps and other gas-ionisation-type lamps are still way more efficient. Secondly: While LEDs may emit light for 6 years continuously, they have a certain half-life that's way shorter than that; at the end of the 6-year life span, the leds probably only emit 1/4th of what they did when they were new.
I used to think of LEDs as cute little indicator lights. A nice tiny, soft green LED light tells me that my monitor is on, or blinkenlights let me know that packets are flowing through my router. An orange LED might alert me to standby mode on a device. None of them were really all that visible unless I was looking directly at them, and certainly none put out any ambient light.
Then I got my newest computer. This thing has a single blue LED backlighting an area the size of a dime, behind the power button on the case. When I turn off all the lights, after a minute or so of my eyes adapting, the single blue LED gives off enough light to illuminate half the room. For the first week or so, I had trouble getting to sleep because of the light... From one blue LED.
As the technology gets better I can imagine LED lamps coming in vogue. I seriously doubt that the end of the bulb will come anytime soon, though. Probably not in my lifetime.
"BSD: Free as in speech. Linux: Free as in beer. Windows 10: Free as in herpes." --Man On Pink Corner in #52607549.
This is no surprise... it's been this way in flashlights (hand torches, to you brits) for a while, particularly the higher-end ones and those designed for specialty applications.
As an example, some of the weapon-mounted lights being used by the military are also going to LEDs. Some of the regular incandescent bulbs just don't hold up as well to the punishing recoil of most weapons... you were forever changing bulbs. The higher end incandescent lights like the Sure-Fire lights could take the shock, but forget mounting anything like a mag-lite on a weapon.
Best thing about them: they're easy on the batteries. Batteries are heavy, and there's nothing worse than having to carry too many spares. Every ounce counts when you're carrying it on your back.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
I'd have to invest in some hardcore lift music to complete the 'still out shopping' effect. And perhaps pay a young relative to scream and be slapped periodically in the middle distance.
www.whitedust.net
Hasn't this been obvious for years? I mean, even though the first white LEDs were hugely expensive, and the public seems to be as clueless as always, this must be one of the most important technology revolutions outside the silicon industry for decades.
*Directed at the USA Today article, not the /. reviewers
"On a very hot day you might want blue light to cool it down a bit."
And if street noise is distracting you, a green LED will quiet that right down.
I wonder what the effect would be on people if
their home enviroment didn't look much different
from their work place, supermarket, etc. I'd
like to think of home as a refuge away from those
places, and sometimes, even the flourecent
ceiling fixture in my living room reminds me
too much of the "real world". When that happens,
I shut it off, and just use the much dimmer
incadecent lamps built into the ceiling fan.
I also tend to feel more relaxed when the
flourecent is off.
Like this one.
The three watt variant. Runs on two AA batteries.
It lights up the entire room with a somewhat cold white light. Can be fixed by adding some red and yellow I recon.
Also, looking directly into it is very nasty, but a clear bulb probably does that aswell.
Wow, I never noticed that the room light is out, guess I have too many displays and boxes with status LEDs in here or something.
Beep beep.
I think one of the main issues with LED lights is the incompatibility with existing lamps.
Sure you buy new lamps every once in a while, but a real breakthrough will come when you can get LED 'bulbs' that fit in a normal 220/110V socket on a normal lamp.
The same thing happened with those energy-saving bulbs, it seems they only really took off (at least here in Denmark where electricity is expensive) when they became available in versions that looked like normal bulbs and fit most lamps.
Another example is the wire spot halogen lights, once they became available in 220/110V versions they took off. Nobody seemed to want those bulky 220->12V transformers around.
There's your answer, fishbulb.
I don't know much about the tech side of LEDs. I know they're pretty. So this might be a stupid question.
Why haven't I ever seen two of the little light junctiony dealies inside one little plastic bubble? Whenever they make products like those LED flashlights that they want to be brighter, they add more individual LEDs, but is there a technical reason why you can't just make the little plastic bubble bigger and put 50 of the light sources inside it to save space? Or is it a manufacturing cost issue?
you can really say a beowulf cluster of leds
The problem is theft.
Over their long lifetime, even existing LED lights are much cheaper than incandescents (factoring in electricty and replacement costs). So they should be attractive to places like hotels, shops and so on.
One of the most serious problems is that the high intial cost makes the LED a very attractive target for thieves. Nobody's going to bother stealing incadescent light bulbs from, say, a hotel room - they're bulky, delicate and almost worthless. LEDs on the other hand, are compact, easily hidden, and quite valuable.
Unfortunately, like the article says, the first cost is still prohibitive in a lot of cases, although the savings in energy would seem to make it worthwhile. LEDs also tend to get very, very hot in large quantities if they're used for a long period of time, so air circulation is a common problem as well.
Hopefully some of you computer engineers and programers can come up with a cheap way to produce and control LED arrays so I can start using them in practice! Building owners would be extremely happy if power consumption in buildings would go down significantly and if they had the ability to control the color and brightness (they are easily and cheaply dimmable, unlike flourescents) of any room individually.
This article contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things (and light sources). This material should be approached with an open mind, studied carefully, and critically considered.
Current white LEDs will last up to 50,000 hours, about 50 times as long as a 60-watt bulb. That's almost six years if they're on constantly.
Erm. Weren't LEDs supposed to have (virtually) unlimited lifetime?
...when you use them to be seen directly be the human eye, like for displays, or car brake lights. As soon as you use them to "light something", like a room, a book with a reading light, or a film set, their property of irregular spectrum makes them only second choice, because the LED light changes the colors in ways ranging from subtle to irritating. Give me flat-spectrum LEDs and I'll use them any day!
A big advantage of LEDs over standard lightbulbs is, that they are quickly switchable without reducing lifetime that much. For lightbulbs you need expensive flashlights, but for LEDs a standard 5mm High Power LED - or if you want more power, a flux - can be used for fast switching applications.
,-).
Additionally you can use many LEDs together without much effort to create nice structures and designes in different colors - as mentioned in the article.
Since I discovered not so long ago, that the blue and white LEDs of today with e.g. 8000 and 20000mcd are another dimension compared to the LEDs I used in my electonic experimenting set as a child, I hacked together an XMMS-Plugin serial lightshow with a uC-backend and use some blue and red high-power LEDs to illuminate some parts of the room. With standard lights that fast-switching beat-detection would not be possible in such a cheap way.
Of course if you really want to illuminate the room in a standard, really bright manner, you need even more powerful and expensive LEDs, however it is a good start and I expect my main, ordinary illumination to be "lightshow compatible" in 10 years
--- censored
So which way am I better off? Just using lower wattage "classic" lightbulbs, or with dozens of 120V AC->5V DC converters wasting energy everywhere.
The adapter for my iBook puts out more heat then the iBook. More of the heat from my AMD64 is from the power supply vs. the CPU and Gfx.
Almost nothing I own needs over 12V anymore. When will I be able to just have one nice 120->12V spaceheater and run everything else in the room off 12V?
- Adam L. Beberg - The Cosm Project - http://www.mithral.com/
They haven't been used as sources of illumination because they, for a long time, could not produce white light -- only red, green and yellow. Nichia Chemical of Japan changed that in 1993 when it started producing blue LEDs, which combined with red and green produce white light, opening up a whole new field for the technology.
This is certainly one way to produce a white LED but it is not the common method today. Most white LEDs use a phosphor to convert a blue or ultraviolet LED into a white one. A quick google found the following page that talks about this in more detail:
http://www.marktechopto.com/engineering/white.cfm
I would speculate that for normal home lighting using a phosphor will give better results as:
I notice when I look directly at a blue light
source, my pupils dialate to the point that the
surrounding enviroment looks noticably dimmer.
Dosen't happen with most colors on the lower end
of the spectrum.
Scince blue lighting is real popular in consumer
devices these days, incuding car detailing, I
wonder how much of a hazard this is for night time
driving, or any other risky places where these LEDs may be showing up?
Just this week, researchers at the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y., said they had boosted the light output per watt of a white LED to almost six times that of an incandescent light bulb, beating even a compact fluorescent bulb in efficiency.
The drag racing industry has moved from incadecant to LED lights for the starting "Christmas Tree"
Introducing Microsoft Vacuum 1.0 The first Microsoft product that doesn't suck.
The feature of LEDs likely to propel them into homes is aesthetic, not practical.
I want to have Natalie Portman propeled into my home. She is aesthetic pleasing, but this would not be practical.
There was mention of the Mitsubishi mini projector/a just a few months back. July was the expected release date, and I haven't heard any changes to that plan.
Build it, and they will come^Hplain.
Its not like you could make a dance floor out of LEDs can you now....
Didnt think so!
...and it should be known by now
Torrent hashes get cranky. LEDs start projecting patterns of dementia across the laundry pile on your floor.
All you can do is role over , face the other wall and wonder if those LEDs you purchased on Ebay really are DOT approved.
Does this mean that when Wile E. Coyote has an idea, an ACME LED cluster will switch on above him? I'm not sure I could handle that sort of iconography.
Nobody's going to bother stealing incadescent light bulbs from, say, a hotel room - they're bulky, delicate and almost worthless. LEDs on the other hand, are compact, easily hidden, and quite valuable.
Just put a little RFID tag inside of the bulb (tm). When you check out they will simply add it to your bill. The lady behind the counter will tell you you with a smile on her face: "an ash tray, two towels, a pyjama and -ohh- 12 light bulbs. That makes $218, the room charge is offered by the hotel."
A few years ago (actually, a lot) when fluorescent lamps were invented someone said that regular lamps would be dead in 10 years. Fluorescent lamps where invented still in 19th century, so I guess it didn't come true.
I'd hope it gets through this time, but people still by those energy consuming lamps, so I'll just wait and see...
The low light receptors are most sensitive to blue. That's why the blue cones are the least sensitive... a lot of blue data comes from the rods.
That's why bluer light looks whiter, and why a blue led fucks with you so much. A bright blue registers pretty close to being white.
Light bulbs are there for a reason. They are cheap. Try to explain incremental cost to "Joe Sixpack" and his eyes will gloss over.
LEDs will be made by the same people who make fluorescents today. They'll start to save the costs of the transformers and the light temperature. The cheaper transformers, of course, will mean that the lights blink at the same cursed 60Hz that today's fluorescents do (I'm happy I don't live in 50Hz land, unless they have better ballasts). Some people have problems with this; my mother can't be under a fluorescent lamp for more than 5 minutes without a migraine. On the other hand, manufacturers will skimp on the blue part of the LED spectrum, which is the most expensive part-- since most modern white LEDs are made by making a blue LED and putting a material that converts some of the blue into a wider spectrum, so you compromise on overall power and make up for it by converting more of the blue to other spectrums-- which is fine for most people because most prefer a warmer light anyway.
Everybody knows a light bulb. For putting in my home, I'll stick with what's efficient. Others will see it differently. Cars may or may not do it differently. Only high end cars get efficient LEDs in their brakelights, despite the convenience and expense when the incandescents burn out and a cop pulls us over to point it out.
A slashdotter pointed this page on efficiency out in a previous LED article.
Q: "How many Californians does it take to resolder an LED?"
A: "Californians don't resolder in LEDs. They resolder in hot tubs."
One can only pray for a GFI failure.
Q: "How many trailer trash rednecks does it take to resolder an LED?"
A: "They still use lightbulbs!"
Okay, that one's still okay.
This is not my sandwich.
from the article:
"If the visitor comes back in 15 years, the fruit of Thomas Edison's bright idea may be gone."
it's a well-known fact that thomas edison had nothing to do with the invention of the lightbulb, see http://en.wikipedia.org/wiki/Lightbulb
when i can get LED lightbulbs @ a reasonable price that i can simply install in my existing lamps that currently have incandescent bulbs, i am sure they dont create heat and use much less electricity...
Politics is Treachery, Religion is Brainwashing
You can lead a horse to water, but a Light bulb revolution must me LED
And thats why Firecrackers and kittens don't mix.
Some say that bikes in the UK can only be ridden at night with 'incandescent bulb' lights, and that LEDs are against the law. I cant find an explicit reference to this, so maybe its changed recently. Certainly flashing lights are outlawed unless attached to the person instead of the bike!
A BBC web site says this:
"If you are hit from behind and you have flashing rear lights, you will be held at least partly to blame - even though flashing lights have been scientifically proven to be more visible."
Baz
LED stocks are the up and coming hot thing. CREE in particular is the stock to buy to get in on this.
But something will definitely replace incandescent light bulbs in the future. They generate too much heat, they most certainly burn your fingers when you touch them, and I've seen a light bulb fracture and spit part of itself across the room when someone accidently dropped a bit of cold water on it. Oops.
Warm and cool are really terms used to describe white light. When you talk about white the question becomes what is it? A blend of all the colours is an elementary explination, but the fact is they aren't all present in equal levels, from any source.
The way that it is talked about, is called colour temperature, and it is spoken of in kelvins. The idea is if you heat a black body radiator to that temperature, that's the kind of white you get. The lower the temperature, the more red in it, the higher the temperature, the more blue.
On most monitors that aren't connected via DVI, you can see colour temperature changes for yourself. In its configuration there should be a colour temperature option, generally with three presets: 5000k, 6500k and 9300k. PLay with them and notice the change. You'll probably find that changing from the one you are used to looks "wrong", either too red or too blue depending on. That's an illusion, however. If you go away for awhile and come back, or just ignore it and keep working, you'll find your eyes adjust and consider that to be white.
With bulbs, it gets more complex because it's not just a function of the temperature of the white, but of it's spectral composition. Most incandesant bulbs have a spectrum that is low on the high frequencies (near violet) and high on the low frequencies (near red). Other lights, like many floursecants, have an uneven spectrum, with peaks all over.
Now ideally what you are shooting for usually is light as close to sunlight as you can get. That's what humans would generally think of as "normal" or "correct" lighting. Easier said than done, of course.
So I don't know what the spectrum for any of the varities of white LEDs looks like, but it is very possible, even likely, that they are different than an incandescant bulb. It may be that they have a generally higher temperature and thus really are cooler, colourwise.
Would you like hot grits with that?
If you want to experiment, here are LED lightbulbs that screw into regular sockets. There are lots of other companies offering them (this was just the first link that came up in Google). Smarthome.com offers them, too.
The lamp manufacturers are very much involved in led development. how much profit margin do you think there is on a 60 watt incandescent lamp sold in a pack of 4 for less than a dollar? Following your logic, the computer chip manufacturers would still want to make 386 processors since it is cheaper to make them.
They wouldn't want a 25% earnings increase to slow down because they're selling less lightbulbs. According to NY Times:
With the stock market as it is, GE will try to keep its revenue up by downplaying the usefulness of LEDs, promoting its bulbs as a more long-lasting and dependable resource used for decades. (Not in my kitchen, where they always burn out for some reason--fuses? weakness? I'll never quite know.)
You can hold down the "B" button for continuous firing.
Color Kinetics has done some of the coolest stuff that I've seen with LEDs.
I saw an article that said that they were growing lettuces under red LEDs in Japan. There was a big saving in the electricity bill as less heat was generated.
Would LEDs be any use for other indoor plants that may need to be grown with sensitivity to electrical usage? My friends dog had a previous owner whose sister once met someone in a bar who said he was thinking of growing tomatoes out of season...
I have an interestiung anecdotal from ye olden days. Way back when, I had a girlfriend who was an artist, and going to an art school. They had a black tie affair for the students faculty and parents,so we went. Hey, free food and champers! Me in a tux, too funny! Anyway, one of the students mom's there lost a diamond out of a setting, fell on the floor someplace. So here's a couple dozen people in gowns and tuxes all bent over squinting at the floor. We saw it, went over to ask "what's up"? Got told about the loose stone, girlfriend glanced down, immediately spotted it, went over and picked it up, like one second. She saw it from her extraordinary ability to see colors. She had been tested in the school and won, ran 10,000 colors in ROYGBIV sequence not missing a single shade, the only student to get all of them correct.
Of course rewiring houses is the real problem...
Most houses are wired in zones, I know all the places I've lived in have the lights on a seperate switch to the powerpoints (which are usually split into groups too). So the lights are actually the easiest to swap as long as you do them all at the same time.
The other stuff gets more hands-on since, just looking about this room, I'd have to crack open my printer to bypass its built-in converter, reduce the 12V to 7.5V for the USB hub, modem uses 15V, phone charger 5.8V, subwoofer might still want AC, etc.
We really need a standard plug agreed on by gadget makers (the USB of DC power) before it makes sense for the rest, but lights might be a good the first step in the right direction.
I'm not sure of the veracity of this, but I remember that a couple years ago the City of Chicago wanted to change all of its lights to LEDs instead of bulbs, but - get this - the light bulb changer's union went on strike wen they heard about it. Ridiculous. In some areas, unions still have use (like in preventing big companies that focus on Arts of the Electronic variety from treating their employees as slaves), but more often than not they just stifle innovation because it'll cause some poor soul to lose their job.
There are also more subtle issues at work with the 'R/G/B mixing' approach to colour generation. You can read more about them here.
To summarise; consider that the red, green and blue receptors are sensitive to a *range* of colours; the sensitivity curve for each receptor is roughly bell-shaped, peaking on red, green or blue light. There is also some overlap between the red and green sensitivity curves, and between green and blue (not red and blue IIRC).
This is of course essential. Sensitivity narrowly focused on R, G or B would leave us unable to see intermediate colours (e.g. yellow!).
Reasonable overlap is necessary, or
(A) there would be certain intermediate frequencies that were not covered sufficiently by either receptor (e.g. certain shades of yellow in the valley between the red and green curves would be very hard to see), and
(B) Colours would be quantised into 'red group', 'green group', or 'blue group' (think about it...)
Because of the (necessary) sensitivity-curve overlap, the green receptor is slightly sensitive to red light, and so on. Where is this leading, you ask?
True cyan has a frequency between blue and green. This is within the sensitivity range of both blue and green receptors; the brain can use the 'ratio' to figure out that it's looking at cyan. But true cyan is (to all intents and purposes) outside the red receptors' range, so the red receptor is not stimulated.
Simulated cyan is made up of green and blue light. This stimulates the green and blue receptors in the same ratio as true cyan would, so in theory looks just like the real thing. However, the red receptor is also slightly sensitive to green light; thus, unlike with real cyan, the RGB-mixed version also stimulates the red receptor.
This is (supposedly) what makes certain RGB-generated colours less convincing (hence the linked story above).
This isn't even counting the fact that our colour receptors aren't exactly R, G and B, and therefore to simulate certain colours using RGB is impossible, as it requires one or more components to be negative. (If the receptors were exactly R, G and B, that would not be the case).
"Slashdot - News and Chat Sites Deviant". (Click "homepage" link above for details).
Anybody know how things like the NASDAQ building were made? I was wondering if people were out there actually making their own large RGB LED displays from scratch. And I was also wondering if there were any LEDs out there that were something like tiles that contained an array of multiple LEDs in the same plastic bit.
Also while LED's have made great strides in efficiency over the last 20 years, they're still no better than a fluorescent tube.
Isn't it strange that blue is considered cool and red warm, even though blackbody spectrum tells just the opposite?
Escher was the first MC and Giger invented the HR department.
I've been dreaming of this possibility for a few years now: imagine if the U.S. government replaced every light in every federal facility with LED equivalents.
;-)
We'd save BILLIONS every year in electricity and replacement costs. I wonder what they'd do with the money? Give it back to the taxpayers, or spend it on a new park in West Virginia?
Stiny! Get me a danish!
I'm one of the, apparently, 5% who has converted 80% of the home bulbs to compact fluorescents. Is is really true that current LEDs are only "about twice as good as a light bulb of the same wattage" compared to 4X for fluorescents?
If so, it looks like I may get my 20 years use on the fluorescents without having to upgrade yet another technology.
I have a lot of 12V halogens in the house powered by compact (12cm3) electronic high-frequency switched power supplies. The advantage is that the halogens, powered at a stabilized 11.3V, do not flicker when a high-power consumer like an oven is turned on or off and last almost forever due to the ^10 inverse power law between voltage and life expectancy for incandescents (see wikipedia).
I have 50W halogens in my living room (lots of hours, lots of switching on/off) that are more than 10 years old. CFs or plain TL do not last that long under these conditions, and aren't close in offering the light quality. Lights are on mostly during the dark and cold winter, so the excess energy they consume isn't entirely lost as the heat is welcome.
Flourescent (adj): smelling like ground wheat.
For a good comparison you could visit the LED Museum at http://ledmuseum.home.att.net/
Everything there is to know about LED's, flashlights and lasers.
Might be fun to get some of these implanted under your skin. I bet a system could be designed that uses a small battery implanted with it that would last a couple years. You'd need a reliable switching mechanism though.
Would make for a nice tattoo!
If you are reading this, then you are one of those people whom I just can't take seriously.
How are cartoons going to indicate someone having an idea?
"Kittens give Morbo gas!"
I think when LED technologies mature, that's where it will have the most importance.
Imagine the same color temperature as xenon high-intensity discharge headlamps but with far less hardware and power requirements, not to mention far longer usable life! It could mean lighter automobiles because there will be less need for a high-capacity automotive electrical system and also we eliminate the weight of the xenon HID headlamp electrical hardware in the first place.
It will be some years before we reach this tipping point in price however as current costs are about $100-$200 a bulb for 65watt equivalent LED bulbs
10 years after most bulbs are LED conventional bulbs will seem anachronistic and stone age. One of the few things in the last 100 years to just be out and out replaced by a new technology. Granted we have lots of bright shining new things in our modern world, but they general have been added to what we already have or evolved slowly from what came before. The switch to transistors from tubes is about the only other thing that comes to mind where this has happened, and perhaps this should just be seen as one of the last hold outs of filaments in tube to be displaced by solid state. All that is left to go are CRTs and this too will happen relatively soon.
In need of a similar revolution: Cars that run without gas - this is a hard one, but we are finally starting to make some progress; Energy production from other than Oil, Gas, Coal, and Uranium. Fusion is about the only way to go here, but it isn't doable at any price today. None of the other energy alternatives have a chance of displacing the big 3 fossil fuels or remaining conventional nuclear plants; Getting to Space without conventional rocket technology. Do all these things and we will have finally arrived in the 21 Century.
Letter To Iran
Fire=red
Ice=blueish
HTH
HAND
I think all the new stoplights in town are LED stoplights. Most of the brakelights on trucks around town are too. Did this story fall through a time-rift from seven years ago?
In the last couple years, many of the stop lights around here have been converted to LED arrays, and they are great. They're much brighter than incandecent bulb stop lights, and the best part is when they start to burn out, it's not all or nothing like incandecents. The city has lots of warning that the lights need to be replaced while there are still LEDs visible for motorists.
In a meeting room somewhere.....
Power company CEO:
Everyone is switching to more efficient lighting, our profits are WAY down! We need to do what the petroleum company's have done because of more fuel efficient cars, jack up our prices!
CEO's minion:
By your command
"I bow to no man" - Riddick
Any guess as to when we will see LEDs replacing the high wattage florescent tube in LCD panels? Even a 50% reduction in power consumption would have a big impact on laptop battery life.
Seems like combining these LEDs with hybrid solar lighting could be even more energy efficient, and still give you the ability to run the lighting in your house like they do in those submarine movies.
Is that electricity costs will rise proportionally so that we end up paying the same amount anyway.
Just like gas.
"Oh, you hate your job? There's a support group for that, it's called everyone, they meet at the bar."
... missing in LED's. I hated LED lights until my Jeep came with reading lights. A cluster of WHT-GRN-ORG emits a chromatic spectra that resembles incandescant light. Really useful and easy to read white pages under this chroma.
A lot of people actually say that LED's are great because they'll be using one watt instead of sixty. Furthermore, a lot of the energy that goes into the diode is being converted into light, not heat.
They'll burn longer, but the problem is that they require so little power, they'll need a decent sized resister so the thing doesn't blow when you turn it on. To be extremely efficient, it'd need some sort of setup so that it has some capacitor or whatever... Capacitor is full, sends electricity to light. ETC.
>
someone should write up an RFP for a new lightbulb socket that's at once compatible with the old edisonian bulbs, as well as something new, smaller, and more appropriate for LEDs.
White leds do emulate hot grits nicely.
Fast and bulbous is the way to go..
"I know that this is true because I read it in the Bible. They did not evolve, they were created by God."
And people wonder why religious people percieve, religion as being under attack.
. . . our new LED overlights.
Still, to replace all our current lighting needs, just imagine, it would take a beowulf cluster of LEDs.
In soviet russia, the LEDs illuminate YOU!
Aaah, it had to be said, I searched to -1.
There goes my karma.
Anyone know of anywhere to get some nice LED desklaps or something little to illuminate my computer desk?
Blinking lights on bikes should be forbidden. The blinking of bike taillights is as annoying and distrubing as blinking ads on a web page. It disturbs the attention of all other users of the road and should not be permitted.
Imagine in 10 years all tail-lights of all other users of the road to blink to stay visible among the blinkers...
Markus
When you show me an LED lamp that will thread into a regular socket, *truly* produce as much light as a 60-watt bulb while consuming 60 watts of electricity (or less), and costs a few dollars. Until then, I'm not holding my breath.
Despite all of the hype, LEDs really aren't as efficient (in terms of lumens per watt) as a lot of people think. Their "higher efficiency" is due to the fact that it is very easy to tightly concentrate the light beam from them. For one of those keychain lights or a reading lamp, that's fine: But when you're trying to fully illuminate a 600 square foot room, that just doesn't cut it.
Also, they tend to be very efficient at very low power consumptions, but as you increase the power, the efficiency drops VERY rapidly. If you need a one-watt bulb, that's alright, but when you're replacing 40-, 60-, or 100-watt bulbs, that will bite you in the butt.
So, let's say that you get the efficiency and coverage things figured out, and you *truly* come out ahead of not only incandescent lamps, but fluorescent lamps as well (don't hold your breath). You're still stuck needing something like 300-600 LEDs to equal a 60-watt lamp. You'd better be making those whiz-bang LEDs at a twentieth of a cent to be anywhere near economical. Besides, who wants a 500-LED array hanging off of their ceiling? Yes, it may appeal to the college-dorm geek, but a foot-wide protrusion isn't going to appeal to the rest of society.
Now, some potential benefits: LEDs can be easily and efficiently dimmed, unlike fluorescents, and that is a larger obstacle than many people realize. The color can also be adjusted, and poor color quality is a HUGE obstacle to the adoption of fluorescents.
Don't get me wrong, I'd love to see LEDs become what people say they will. But when you get through the hype, BS, and semi-dishonestly measured ratings ("I'll take this 100 milliwatt LED and rate it's efficiency at 1 milliwatt to boost the score...."), they're just not nearly as close to mainstream adoption as a general lighting source. Spot-lighting, sure. General illumination, no.
steve
Oh, you're not stuck, you're just unable to let go of the onion rings.
White LEDs can have a continuous spectrum; Expecting RGB bands or at least distinct bands, it surprised me a bit when I put one through a spectrograph about 5-8 years ago and found a smooth looking spectrum.
Thought everyone noticed that stuff.... Though when i was younger, I used to think everyone heard the HV transformers in TVs too. Never thought to mention it to anyone at the time.
I didnt see the parent posters examples, ill go back and re-read it.
---- Booth was a patriot ----
I doubt it, at least not the kind of person the grandparent is referring to. If you are you should be calling a research lab and asking for bids to be a guinea pig. Tetrachromats are extremely rare.
This hypothesis sounds more likely (from http://www.physics.utoledo.edu/~lsa/_color/18_reti na.htm
Rods and all three cone types readily absorb ultraviolet radiation, photons of which are energetic enough to damage these delicate cells. The reason we cannot see in the UV is because the eye lens is opaque in that wavelength range. In addition, the cells in a region called the macula surounding and including the fovea contain a yellow pigment that further prevents short wave radiation from reaching the photo-receptors. Some people with less of this yellow pigment and those who have had their lenses replaced with plastic inserts can see further into the UV than normal people can.
Has anyone got information as to the overal costs on a per lumen basis associated with manufacturing LED vs those for traditional incandescent bulbs?
I've read some rather nasty descriptions of the cost of manufacturing semiconductors -- the highly toxic chemicals that are used, worker exposure to these, the large amouts of water that are needed, etc. -- and I'm wondering whether the touted benefit of LEDs being so energy efficient are really true when one takes into the account all of the costs associated with producing and using them.
CUR ALLOC 20195.....5804M
In the 2 houses I've owned in the past 8 years, I loaded every bulb socket with these things (excepting the oven and fridge). I've documented a $10-to-$20 savings per month, depending on the season. In those 8 years, I've had maybe a half dozen of the 30 or so bulbs in each house go bad.
Not a bad deal.
Method of processing duck feet
Since the original poster referred to 'warm' and 'cool' in ironic reference to chips and vacuum tubes, I would believe that they referred to the debate amoung rock musicians between vacuum tube (or valves, in the UK) and power transistor amps. Here 'warm' refers to the difference in non-linear distortion at the high-end saturation level of the amp's operation. Tubes distort differently and musicians call this characteristic 'being warmer' than the power transistor sound.
If you find that the "blinking of bike taillights is as annoying and distrubing [sic] as blinking ads on a web page" then those lights are doing their job properly. Just like the garish ugly clothing that many cyclists feel they have to wear though they hate it improves their chances of not being hit.
There are way too many dumbass motorists out there whose mind is more on the aesthetics of the driving experience than on driving safely. Not that you, Esteemed Sir or Madam, are one of those.
As to safety considerations in 10 years' time: You are now telling me that I should let my imagination of a possible future guide the safety decisions I have to make today. You, Sir or Madam, are FUBARF[1]
Do they run Linux?
...the right of the people to keep and bear arms, shall not be infringed.
When compact fluorescent lights went for ten to twenty bucks each, it's very understandable that few want to invest the big bucks to change all their house lighting over for the promised benefits. They're used to paying their electric bill, and the thought of lowering it might not be as immediate as the thought of shelling out one hundred or more bucks for a bunch of light bulbs.
Last summer, we found six-packs of compact fluorescent bulbs for about ten bucks at Home Depot. We started buying a pack or two every time we went from $120.00+ to less than $80.00 per month in electric bills. The bulbs paid for themselves in less than a month.
Practical tip: If you're buying a few bulbs at a time, put the first ones in the fixtures that are on all the time, and the places where kids turn them on but forget to turn them off.
When I brought up compact fluorescent lamps on another forum, the major complaint about them was the imperceptible (120 Hz*) flicker that causes some people headaches, and the ghastly color.
This prompted me to do some testing. I swung a string with a weight on the end under an older fluorescent and noted the dark bars that come from the flicker. The modern electronically ballasted lamps have no flicker.
As for the color -- well, some are a kind of ghastly bluish, and others a of a much warmer color. Look at the label and make your choice.
I predict that some of the first household LED lamps will have some kind of a gimmick to make it more desirable. You're not spending $$$ to do what you are already doing. You are buying a fancy "mood light" dimmer system that lets you set your color and brightness where you want it.
"the lightbulb industry lobbies the congress to ban LED technology that will ruin the market for lightbulbs."
The lightbulb industry isn't competing, effectively with a "free" version of themselves. The content providers however are, because the "product" is a digital copy of what they offer. Not a digital original. There isn't a "digital copy" industry built up around the light bulb, who's main purpose is to get "free" lightbulbs.
LEDs are practical right now for many applications. A few years ago, I bought some Dorsey solid state flash lights. I found one outside one morning. It was turned on, and still working (though dimly). Even though a white LED is inherently less efficient than a separate red, green, and blue Leeds, and even though the use of a dropping resistor makes the system less efficient and more sensitive to drops in battery voltage, the lamp greatly outperforms its incandescent counterpart. That is largely because a small incandescent is a whole lot less efficient than a large one.
Also, since the source itself is small and uniform, the spot of light uniform. Shining an LED flashlight on the wall yields a nice, round spot, rather than a hollow circle or half-moon shaped spot.
We recently bought some more modern LED flashlights that use a single AAA battery. Instead of using a dropping resistor to regulate the current, they use something very similar to the switching power supply circuits that are used in computers. We haven't managed to run one out of power yet.
Another area where Leeds are very practical is any application where you want a single color of light -- automotive tail lights, traffic lights, Christmas lights, and the like.
An incandescent emits all colors, so if you want a single color, you end up using a filter to throw away most of the (inefficiently generated) light.
You might notice that the very money-conscious trucking industry has gone to LED tail lights. They put up the money now, and end up having to pay less mechanics to replace burned-out tail lights, not to mention the occasional citation, and the necessity for keeping them inspected. Switching to LED tail lights doesn't increase the mileage of the vehicle significantly, but the reduced maintenance alone is enough to pay for them.
I guess we are going to start having "illumiphiles" who will try to tell us that the incandescent lightbulbs of yesteryear are somehow "warmer" and that humans can tell the difference between LEDs and vacuum tubes.
Incandescent light bulbs create light much the same way as the sun. Something that is hot emits electromagnetic radiation is a specific pattern -- a smooth blend of all wavelengths with more energy at the lower wavelengths. LEDs emit monochromatic light. While red/green/blue (and red/yellow) monochromatic light looks white to us, it will illuminate things differently. This is more noticable to some than others.
That is unlikely to ever happen. Beyond the obvious problem of getting a critical mass, DC is the wrong solution to the problem.
Put AC through a transformer and you can efficiently change the voltage to anything you care to use. (There are limits on the high end, but 100,000 volts is too much for a house so who cares) Most of those DC things want 5 volts or less (they don't all want the same, though you can use a resister to change voltage inefficiently), but to transmite your power requirements at 5 volts requires think wires, enough to make copper one of the most significant expenses when building a house.
DC is used fr long distance transmissions. However power companies worry about other issues.
waste of money, compact flourescent and flourescent laps are still more effianct and cheaper
There is virtually no scenario where a commercial plant could pose a threat to a surrounding population. BUT because there is still some waste, so there are some environmentalists that would oppose its pursuit.
Again getting back to the gasses issue. Because the percentage weight difference is so huge between isotopes of helium and hydrogen, you can much more easily separate out the radioactive byproducts. What's left can be used industrially, or more likely just released back into the environment. Remember that burning coal releases all sorts of more dangerous radioactive isotopes into the air, ones more readily absorbed into the body. Conventional fission reactors (accidents aside) put far less radiation into the environment than coal, and with fusion we're talking generating thousands of times less waste again. I don't believe there are any remaining radioactive direct fusion byproducts that cannot be recycled. As for being dangerous because they are gasses, should they need to be contained they can just be made part of a chemical that is not a gas. Should there be unusable Helium isotopes (helium won't bind chemically to other elements easily), which I don't believe there are any unusable ones, but should you want to permanently get rid of Helium isotopes, they could be released at any suitable altitude to drift into the far upper atmosphere where solar wind will eventually strip them away from Earth completely. This is why we have to mine Helium from deep underground; it doesn't stay in the atmosphere.
Fusion can be used to generate Tritium or convert abundant Thorium to Uranium and Plutonium, thus could escalate proliferation of atomic weapons, but that would be an abuse of the technology not an inherent byproduct of normal operation. But this is no doubt this is where radical environmentalists will hang their hats in opposition. Of course this kind of Ludite thinking only works if you can get every nation in the world to avoid Fusion.
I predict the next 5 to 10 years will see breakthroughs in fusion. My reasoning is that Oil prices will probably fluctuate wildly over the next 5-10 years seldom getting below $40 and often above $60. While I don't think there has been a conspiracy to keep fusion down, nothing focuses the mind quite so clearly as a crisis. $60 dollar a barrel oil will motivate research into all sorts of energy research. Unlike the '70s I don't believe truly cheap oil is returning, oh and there is that Global Warming thing to think about.
Letter To Iran
In the summer time in the USA the incandecant is actually a lot more inefficient than its power draw. The reason for this is that these creatures put out about 95% of their energy as heat which then has to be pushed out the window with an A/C
OTHO - in the middle of winter it can be just as efficent to heat your home with light bulbs as with a furnace and in the future as fuel prices increase it may become even more economic.
While a LED may be more efficient and it certainly can be switched on and off a lot (they are used in place of lasers in fibre optic communications) the cost will have to appraoch that of a light bulb before they become economic in say the bedroom.
So I don't think the light bulb is as obsolete as it is made out to be.
I have read that compact florescents are more energy efficient than leds. As for the life - I've been using them for over 10 years now and they live for anywhere from 5 to 7 years or more and this is at 16+ hours per day usage.
The lifespan is much greater if they run constantly - same as with a computer.
In my office for instance I have 3 x 13 watt so that is 39 watts draw. at 10 cents per kwh this works out to just under 10 cents per day or $28.08 per 30 day month for 24 hours with lights on.
Since they last over 5 years the bulbs cost less than incandesent bulbs without considering power draw. Since fuel prices are up any waste energy offsets heating costs in the winter so the marginal cost of operation is probably under a nickle per day. The lifespans I've been getting are in the 50,000 hour range even though they are not rated for this - but then I sometimes leave them on for weeks at a time. At most they are cycled once per day.
Sorry - that is $2.808 per month. I amde a typo.
The one thing nobody has addressed is that LEDs shoot almost all thier light straing ahead. They are almost impossible to focus accruately, because bright lights need many LEDs, and each LED had it's own first lens in it's plastic end cap. These things are precision, but not up to optical precision standards. You don't get 1/2 wavelength precision for $0.10 each. Therefore, the focus is rough, and some beams are too small while others are too large.
/. users who use LED lights don't understand how they work.
Also, has anyone noticed that on multi-LED lights, if all the LEDs point forward, you can cover up 1/2 the lights, something strange happens? Can you tell me what? It's not like a standard flashlight. 90% of
Finally, I can vouch for the weapon mounted LED lights. They are amazing. Look on the bright side, with the RIAA so afraid of new technology they will be using black powder muskets by torch light when they finally spark a second American civil war (next week.)
Andy Out!
Here's a challenge for the boffins: white LEDS in my video projector. You don't know just how much trouble that whacking great lightbulb causes.
thermonuclear ignition will be achieved in the laboratory in the year 2010 (+or- 2 years). so yes, there will be a breakthrough in fusion in the next 10 years but it will not be due to 60$ a barrel oil. it will be a result of slow and steady progress in the field over the last 40 years and a decision in the early 90s to build the NIF. is this the breakthrough you were talking about? no perhaps not. but the breakthrough you were probably referring to (economical fusion power) is possible and it is still a good bet that this type of breakthrough will also occur in the next 10 years. the Univ. of Rochester's lab for laser energetics will switch on the most powerful laser in the world in 2 years. this laser, at ~3 PETAwatts will be equivalent to about 2% of the total power recieved by the earth from the sun and will be used to attempt "fast ignition" experiments which may indeed make fusion power economical.
- "Hear that?! The percolations are imminent! Cease your ingress!"
The article mentions replacing neon signs, thereby avoiding the associated fire risk.
Cable installers would appreciate that too, as mandatory separation between Extra Low Voltage (e.g. ethernet, phones) and High Voltage (such as neons) is a much bigger deal than separating ELV and LV (such as 110V / 240V)
-- All your bass are below two Hz
LEDs may be changing the home, but it will be a long time until they completely replace the conventional light bulb. I work as an LD (Lighting Designer) and while LED lights are entering the market, they are still a far ways away from a good discharge lamp. In short, LEDs are here to stay, they will revolutionize a lot of lighting, but there are still many applications which will continue to use good old regular (If you call discharge lamps regular...) light bulbs for quite a while yet.
...Had this been an actual emergency, we would have fled in terror, and you would not have been informed.
Only the old transformer "ballasts" work that way. Solid-state ones run at 25khz or more.
A google search will explain.
12V might sound nice for some low power equipment, but its not really suitable for most household appliances.
Imagine something like a vacuum cleaner; these things are rated 1000 to 2000 watts these days. A 1200 watt model would need a whopping 100 amps. Plugs for this sort of current tend to be huge.
A standard european socket provides 230 volts at 16 amps, well over 3.5 kW. To give the same power output at 12 volts, it would need to supply over 300 amps... cables suitable for that voltage are a few CM in diameter.
Then tell me how the hell I'm going to grow my daffodils, tulips, and crocus??
Oh, LIGHT bulbs.
Nevermind.
Sanctioned by God. (tm)
While the LED element will last for tens of thousands of hours, the phosphor coating will not last that long. Based on tests I've seen a difference can been seen in a matter of days, presenting a problem for widespread lighting use.
Mixing red, green and blue LEDs into white does not have this problem.
..don't panic
I came to the same idea once, that a DC line throughout a house was a lot more efficient than dozens of AC to DC power bricks. I'm thinking this new DC plug could be shaped similar to headphone jacks, like the DC in on some devices, to avoid confusion with AC plugs.
It talks about the first good really efficient white LED. The kind useful in replacing indoor lighting.
They are only efficient compared to incandecent bulbs. Even most common flourescent lights are more efficient. Halogen lights are more efficient. High pressure sodium lights are several times more efficient.
White LEDs have a horrid spectrum. Here's an example of what spectrum a light source should have, and similar spectrum correcting technology can be applied to more efficient sources such as HPS. LEDs are good for displays as status lights, but it's stupid to use them for general lighting when there are far better options.
"Politicians and diapers must be changed often, and for the same reason."
nuff said
Yeah, I recall this discussion on /. a while back. Somebody kindly posted a table of lumen-per-watt performance from various light sources. LED's were in the middle of the pack, and low pressure sodium had them beat by a mile.
I think the selling point of LEDs is that they are good for low temperature, low power situations--and being solid state, they also are much better for reliability in wear-and-tear environments.
Does anybody have RFI / EMC data or experience on the LED light systems that are sold for household use?
Talk about cheap incandescents:
When I lived in Chicago, late nineties, Commonwealth Edison [the power company] subsidized incandescent lightbulbs to the point of giving us vouchers for up to four bulbs free each month. No subsidy for new tech such as compact fluorescent, as I recall.
For electric house lighting, I'd never use anything other than a good ol' incandescent for several of the reasons you quote.
But when it comes to hand-held flashlights, nothing beats LED technology in terms of operating hours! The 'Lightwave 4000' I picked up, on the conservative side, gets about 900 hours on a set of three D cells. (2000 hours if you believe the packaging.) It's darned bright, too.
The little 'Dorcy' singe AAA cell is supposed to get about 200 hours. It's darned bright as well. --I used it during a night-bike ride through unlighted back roads, and it was illuminating road signs fifty meters away.
-FL
Without power, many people seem to turn into hopeless wrecks.
People burn their entire supply of toxic paraffin candles in about two days, (if they have them), they run out of food, and they start to freeze. If the power had gone out for more than a couple of weeks without emergency help or without a shift in how people arranged their lives, I think we'd have seen some serious Darwinism in effect. --Luckily, when people get motivated, they also tend to be quite resilient; two weeks without power is like getting kicked out of bed. "Okaaay. Fine. I'll go do something about the situation rather than gripe and eat all the easy food."
But anyway. .
I found myself hurting for a decent lighting solution. With no power, and time to kill, people like to read and they play social games like D&D! Except, without reliable lighting, these things are possible only during the daylight hours, (which in the winter time are in shorter supply, plus if you have your windows covered up with blankets for extra warmth, the lighting situation isn't so good). --And a room filled with paraffin wax smoke gets toxic and trippy in a bad way after about half an hour. Yuck. --Bees wax burns non-toxic and smells really nice, but those kind of candles are usually expensive and in short supply.
Enter the LED flashlight! After the power out-age I ordered a 'Lightwave 4000'. It runs on 3 D-cells, and you can expect about 900 hours of solid run time. (2000 hours, if you believe the packaging, which I don't.) Still, 900 hours is 37.5 days of solid 'On.' Cut that in half for night time use only, and you're looking at over two months of lighting on 3 batteries. That's 9 batteries to last you all through winter. Not bad!
Then just toss in a few of those small, $10 Dorcy single-LED lights which run on AAA cells for 200 hours or so. --Keep those in supply, and you're fine. --For a social setting, just set up a Bee's wax candle to throw a little nice color, and you're surviving in style.
Wrap up in blankets, get an alcohol burner for teas and soups, or better, a wood stove, and you're laughing. Life is fun when you're prepared!
-FL
Lamina leds are the best I've found. They've just released a small round array that looks interesting. Low power, efficient, balanced and bright.
I saw the LED Zepplin light years ago. I have every album ... but doesn't seem to illuminate the room. I must have bought faulty ones.
Sure enough, the cow costume was hanging up next to the superhero outfit and sailors uniform. (S,Spud)
Except for the fact that low pressure sodium gives off this horrid yellow light that is impossible to see any color whatsoever in. Not only is it limited application for this reason, but not being able to see color is something people associate with low light conditions. So you have an area that's very well lit, in theory, yet people think it is very dimly lit.
The only upside to low pressure sodium is being able to throw the lamps into a 55 gallon drum that's half full with water, breaking them on the edge of the barrel, and watching the sodium burn in the barrel.
The previous has been a secret message to my comrades.
Home Theatre Projector lamps are, as you may know insanely expensive. Furthermore, in DLP projectors the light goes throug a RGB color wheel to produce the colors. Would it not be possible to use an array of RGB LED's in the projector set at the frequency of the color wheel? This way you remove the expensive (and very hot) bulb and you remove the moving part - the color wheel.
h tm that you can also "overdrive" leds - that is increase their brightness if they are on for a very shortened period of time. Thus, you could possibly triple the output of the LED's without causing them damage.
I saw on this website http://www.emanator.demon.co.uk/bigclive/makendo.
Anyone out there consider this? Does this sound like a worthwhile DLP projector hack?
Try to hack my 31337 firewall!
Ah, I see what you're getting at now.
IF cyan stimulates the red cones (it will, fractionally, as I doubt the red-sensitivity-curve will have hit 0 when it reaches cyan; the only question is by how much (*)), then even "genuine" cyan will be "impure".
Of course, this is rather misleading; if it's genuine single-wavelength cyan, then it can't be considered "impure". That's just the way the eye perceives pure cyan.
Assuming all this is true, what *you* are doing is something quite unusual; YOU ARE MAKING A "COLOUR" THAT COULD NOT EXIST IN REAL LIFE! No real colour would stimulate green and blue to that extent without stimulating the red sensors also (under normal circumstances), and this brings up some very interesting philosophical questions.
That having said, to be honest, the cyan I got from your simulation was vivid, certainly, but it didn't appear "artificially" bright. It may have been more vivid than fake 'green+blue' cyan for the reasons described above, but it didn't appear "more cyan than real cyan". Perhaps you *really* have to zap those red receptors, or perhaps (as I originally assumed), the red-receptor output is so negligible at cyan frequencies that reducing/omitting it makes no notable difference.
Still, all good stuff, and it could point the way to some very interesting experiments with synthetic colours.
Oh, and on a semi-related topic, check out these links, and search the text for "martian colors":-
One, Two.
Essentially, colour-blind subjects with synesthaesia who cannot perceive certain colours optically can still "experience" them as a result of their synesthaesia. In short, they can experience colours that they couldn't possibly see.
(*) Note that I say "to all intents and purposes" in my original post. I assume that the red receptors will still be minutely stimulated by (e.g.) blue light, but at an extremely low level which is insignificant.
"Slashdot - News and Chat Sites Deviant". (Click "homepage" link above for details).
WIth a passion that can only be described as 'migrane'.
I've had a number of those LED Tailight vehicles drive past me and been nearly wrecked because I can't keep my eyes off them. The flicker at such an obnoxious rate that, even while staring forward, my vision is destroyed as the car passes me.
If it passes on the right I'm left with 12 to 14 after images of that damn tailight streaking thru my vision.
Very very very annoying. At least flash them at 120hz.
Is it just psychological because we associate them with work and depressing places? Is it because the truer white makes the bland walls, carpeting and cube fabric blander? Or is it beecause most institutions go with el cheapo bulbs? I have several compact fluorescent bulbs in my house and really like them.
Things are more like they are now than they ever were before.
Really though, you should at least give a link!
The mind certainly does summersalts on this issue. So an LED would be more power-efficient than a bulb, of course, because it generates less heat. However, you have to convert to DC which generates MORE heat. So in saving power, we waste power.
I find myself wondering what percentage of the power in our grid system ends up being consumed in AC->DC conversion. Could it be more than 50%?
Perhaps power-supply manufacturers should be taxed relative to the efficiency of their power supplies? That would be incentive to build devices that convert into DC with higher efficiency as well as providing incentive to have centralized conversion in a home.
I think it makes a great deal of sense to have power outlets in the home that supply both AC and DC current. Granted, DC does not carry well over large distances, but it should be okay in the typical home, right?
The reason that it can be true that 1+1 > 2 is that very peculiar nonzero value of the + operator