LED Lighting As Cheap As CFLs Invented 553
mcgrew writes "New Scientist reports that a British team has overcome the obstacles to cheap LED lighting, and that LED lamps as cheap as CFLs will be on the market in five years. Quoting: 'Gallium nitride cannot be grown on silicon like other solid-state electronic components because it shrinks at twice the rate of silicon as it cools. Crystals of GaN must be grown at 1000C, so by the time a new LED made on silicon has cooled, it has already cracked, rendering the devices unusable. One solution is to grow the LEDs on sapphire, which shrinks and cools at much the same rate as GaN. But the expense is too great to be commercially competitive. Now Colin Humphreys's team at the University of Cambridge has discovered a simple solution to the shrinkage problem. They included layers of aluminium gallium nitride in their LED design... These LEDs can be grown on silicon as so many other electronics components are. ... A 15-centimetre silicon wafer costs just $15 and can accommodate 150,000 LEDs making the cost per unit tiny.'"
Finally! (Score:5, Funny)
Now Colin Humphreys's team at the University of Cambridge has discovered a simple solution to the shrinkage problem.
Excellent news! Wait, what's this story about?
Oblig seinfeld reference (Score:5, Funny)
Lightbulbs getting out of a pool I guess.
My first experience with LED lighting... (Score:5, Insightful)
So I bought a 3 pack of LED lights that were supposed to be the equivalent of 40 watt bulbs...
A 25 watt incandescent bulb is about 10 times brighter. I was pissed. Might keep me from stumbling in the dark, but it doesn't really illuminate a damn thing.
I was so hopeful.
Re:My first experience with LED lighting... (Score:5, Insightful)
I've heard similar reviews from a co-worker who was very motivated to 'go green'. The '40-watt equivalent' turned out to be an over-sized night-light (per her review - I haven't seen it).
Still, this could be good news. I switched about half-way to CFLs largely to save $$ on electricity, but they're neither as efficient nor as 'green' as LED lights. I priced LED lights but, at the time, they were so damned expensive that it would take ~40 years for the investment to pay itself off. Even if I have to over-rate everything to get the same level of light, it should be better all the way around compared to the current alternatives.
Still, even though this sounds solid, the ominous 'This should be available in 5 years' always makes me a little cautious.
What about the production? (Score:5, Interesting)
I'm all for getting away from CFLs, as their production alone is NOT environmentally friendly (most of the mercury in the world is mined in China, where HALF of it is "lost" to the environment during production, which means "polluted"), not to mention the ratio thrown out.
But what about the LEDs? How toxic (or not) are the materials they're talking about? And what about the production of such? And heck, back on the pollution thing, WHERE they are produced makes a big difference, since if it's in China, forget any environmental disposal of chemicals used, whereas if it's in a developed country, it'll probably be OK.
Not insurmountable problems, but I do want to know how those things will work out.
Re:What about the production? (Score:5, Insightful)
If you only replace them at 1/10th or 1/1000th the rate then its unlikely it could be bad for the environment....
Wrong bulbs (Score:5, Informative)
You're buying the wrong bulbs then. Mine are at full brightness instantaneously.
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I've heard this dozens of times, but never seen how to differentiate crappy CFLs from good ones at the store. It's not like they have labels like "Hey, this CFL sucks! You should probably buy something better!" and spending more money is no guarantee of quality.
Do you have some reliable way to tell good CFLs from bad ones? I'd like to know how to do it.
Re:Wrong bulbs (Score:4, Informative)
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Re:Wrong bulbs (Score:5, Informative)
Re:Wrong bulbs (Score:4, Informative)
Re:Retina Sear (Score:5, Informative)
A pointless tip for anyone:
Don't you hate it, in the middle of the night you have to have a piss. So you get up and can quite easily make you way to the toilet just by ambient light. You flick the light switch in the WC and do your thing. You finish and then switch the light off. Instantly you are thrown into total darkness. You stumble your way back to bed, hitting your shins and stepping on as many things as possible on your way. What can you do?
A simple solution is to close one eye before turning on the light. Keep this eye closed tight as long as the light is on. After you switch the light off, open your eye. You can still see quite well in the ambient light again with the eye you had closed as it did not adjust to the brightness of the light.
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Re:What about the production? (Score:5, Informative)
Quit buying crap CFL and just rig your place with T5HO linear fluorescent.
One 54 watt bulb is all I need to light my living room or my kitchen, and it's 5,000 lumens INSTANTLY, no warm-up.
And they grow GREAT sweet basil and catnip and peppers.
Re:What about the production? (Score:5, Funny)
Is that what the kids are calling it these days?
Re: (Score:3, Informative)
I know you're joking, but that's what I actually grow with T5HO. [photobucket.com]
Pot only gets cloned and starting veg under fluorescent, then it's HID all the way.
Re:What about the production? (Score:5, Informative)
I'm calling bullshit.
The largest T5HO bulb only uses 54w of power, two of those would be 108, plus ballast which in reality should be far, FAR more efficient than that, should use no more than 125w of power.
My 4-lamp T5HO system uses 230w according to Kill-A-Watt, that's 216w in light bulbs plus 14w energy conversion loss in the ballast. I toss out 20,000 lumens.
Your 100w incandescent only at most pumps 12-1800 lumens.
So either you bought some bullshit lighting or you're talking out of your ass.
Re:What about the production? (Score:5, Informative)
Re:What about the production? (Score:5, Informative)
When you break a lamp, the state of Maine [maine.gov] says "The next time you replace a lamp, consider putting a drop cloth on the floor so that any accidental breakage can be easily cleaned up. If consumers remain concerned regarding safety, they may consider not utilizing fluorescent lamps in situations where they could easily be broken. Consumers may also consider avoiding CFL usage in bedrooms or carpeted areas frequented by infants, small children, or pregnant women. "
Here's what the EPA says to do if a CFL bulb breaks in your home [epa.gov]:
Before Clean-up: Air Out the Room
Clean-Up Steps for Hard Surfaces
Clean-up Steps for Carpeting or Rug
Clean-up Steps for Clothing, Bedding and Other Soft Materials
Disposal of Clean-up Materials
Re:What about the production? (Score:4, Informative)
I suggest you look up their recommendations for cleaning up a standard incandescent bulb for comparison.
I looked and didn't find anything. Care to provide a link?
As far as land fill problems, putting them in the land fill puts less mercury in the enviroment then using an incandescent bulb. Assuming your power come from coal, and not a clean alternative like nuclear.
The concern here is spot concentration -- what goes into the landfills tends quickly to go into the groundwater. If you've got a coal plant 150 miles away, you're not going to be getting much of it. Here's a link [mercuryexposure.org] that says mercury in landfills is a bigger problem than mercury in the air.
Re: (Score:3, Funny)
My coal plant is 5 miles away, you ignorant clod.
clean alternative like nuclear (Score:3, Informative)
Nuclear power isn't clean.
Falcon
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So it looks like the real mercury is from mercury vapor and from mercury that's already in the food chain.
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(Yes, this is a [citation needed] moment, I apologize.)
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not everybody's power comes from coal (Score:3, Interesting)
There are a lot of places where the majority of power comes from nuclear and hydro.
Yes, and both of those power sources use a lot of energy to build. Then for nuclear there's pollution from mining as well as the waste.
Also, the real risk of CFLs is caused by the fact that any pollution from it is local and concentrated as a point source
Over a period of years I replaced almost all of my incandescent light bulbs with CFLs. As one burnt out I got a CFL to replace it. A point source of mercury is easier to h
CFLs (Score:3, Insightful)
I use CFLs, though I've had 3 out of the 8 I installed go bad within the first 2 years of use and still haven't found the time to "properly" dispose of them.
I too use CFLs. Like you I have 3 that burned out, however one lasted about 20 years. I don't know how long the others lasted. Also like you, I haven't disposed of them either. I put them in a room nobody uses in the packaging some of the CFLs I bought came in. When I find out where I'll take them in for recycling. I heard Home Depot was starting
Re:What about the production? (Score:5, Informative)
BULL-fucking-SHIT. The ~3 MILLIgrams of Hg in a CFL are in an entirely inorganic metal amalgam form [patentstorm.us]. Stop pulling wacky pseudoscience scare tactic shit out of your ass and claiming it as truth.
Re:What about the production? (Score:5, Informative)
Inorganic mercury in the environment (wether it's by burning coal at power plants or from light bulbs) eventually reaches soils, which get wet with water, and as most of the water on land eventually does, washes into aquatic systems (water cycle).
Microorganisms in the aquatic environment then convert it to methylmercury (what he was talking about).
After that, it's the same old story you already know: Aquatic system is contaminated so the mercury (actually methylmercury) bioaccumulates its way up the food chain until it gets to the humans who eat the fish. The higher up the food chain the carnivore is, the more toxic their exposure is. This should be of personal concern to you if you are a whale, shark, big fish (like tuna) or human.
It really doesn't matter what type of mercury is in those bulbs.
All forms of it that get into the environment do eventually turn into the very type that hurts us most.
Re: (Score:3, Informative)
Manufacturers are moving from CCFLs to LEDs for laptops primarily because of power issues - lower power consumption == better battery life.
Re:What about the production? (Score:5, Informative)
More mercury from coal plants used to power incandescent bulbs, 100% of it lost to the environment. Look at whole life, not just one part.
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I get my power from HYDRO!!!!
Are you hooked up to the grid or do you have a micro hydro system?
Tell that to the environmentalists who won't let us build dams, water wheels, nuclear power plants, or anything that actually makes sense.
Dams are not environmentally clean, neither are nuclear power plants.
Falcon
Re:What about the production? (Score:5, Funny)
All in all, a win all around, although - as someone has mentioned here - LEDs are not that 'bright' compared to traditional lighting.
I take it you've never seen a high power LED. All I can say is: don't look into high power LEDs with remaining eye.
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It's all about the tight beam. LED lighting is much dimmer overall than CFL, but if you only shine light in a 12 degree arc it will be 100 times as bright as the same light in a 120 degree arc. If you *want* a narrow beam, LEDs are a clear winner. If you want to light a room, not so much.
In any case, gallium is scarce and there's not an easy way to increase production (there's no such thing as a gallium mine, we get gallium as a byproduct of aluminum production). If there suddenly a spike in gallium dem
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I see it a different way.
If gallium becomes scarce and expensive, then aluminum prices will drop. This will bring us cheaper, stronger, lighter, and less bio-degradable cars.
I, for one, welcome our gallium-based LED lighting overlords.
Re:What about the production? (Score:4, Informative)
1) They are nearly a perfect point light source.
2) They light output is typically very directional.
But when you try to illuminate a room with one, you have to spread out this concentrated beam so much that it's not nearly as bright as your first impressions might make you think.
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Wow, that looks awesome... but I'm just not prepared to spend $70 for a flashlight.
Don't need to. Go to target or walmart, they will have lights in the $15-$30 range that do 120 lumens too.
The bare emitter is only a buck or two, so even "cheaper" flashlights are starting to use them.
Unfortunately, even the brightest emitters can't do much more than 800 lumens and still cost in the $10-$15 range, so real incandescent replacements for the home are still either underpowered (a 90 watt incadescent can do roughly 1800 lumens) or prohibitively expensive.
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"While not considered toxic, the data about gallium are inconclusive. Some sources suggest that it may cause dermatitis from prolonged exposure; other tests have not caused a positive reaction."
-wikipedia
You must be thinking of a different metal.
We need lumens ratings (Score:5, Insightful)
The real issue is that all light bulbs really do need to have the rating of lumens. Wattage is power use, lumens is light output (obviously). Saying "40-watt equivalent" is empty marketing speak, no wonder they were disappointing. And then there's the whole light temperature issue, which is very difficult for a consumer to determine.
For my LED experience, I went with these LED bulbs [theledlight.com] for my chandelier (I was looking for a "25-watt equivalent") and have been very pleased. It may help that it's a cluster of bulbs in my fixture. Considering the lifespan of LED bulbs, I'm willing to pay a lot more per bulb providing the light output falls in the appropriate range.
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Especially as color temperature doesn't really tell the story where LEDs and fluorescents are concerned. While incandescent lights are thermal emitters with smooth color spectra, the others are composed of several sharp peaks at different wavelengths, a conditition which doesn't reduce to a single color temperature. It's also much of the reason why the light seems somewhat harsh and unnatural.
Re:We need lumens ratings (Score:5, Informative)
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I will verify this experimentally when I get home; I have diffraction gratings, I have "pure" (amber and orange-red)
Re:My first experience with LED lighting... (Score:5, Informative)
How so? Recently, in my local walmart, GE started selling Par20 LED bulbs that were supposed to be 40-50 watt equivalent but for 7 watts produced 200 lumens. That's 28.5 lumens per watt.
My Feit Electric (Costco) 13w CFLs (60 watt equivalent) produce about 800 lumens. That's 61 lumens per watt.
A 60w incandescent makes around 700-850, depending on brand. Using the 800 as a comparison, thats 13.3 watts per lumen.
LEDs may have the potential to be more efficient than CFLs, but it doesnt look like they automatically are. Or am I missing something?
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If you properly "dispose" of them (aka "recycle"), you can reuse just about every part of them except the small PCB in the base, and even that you can strip for the metals.
So yeah, they have a tiny blob of mercury in them - Of which, when properly recycled, 99.999% should end up in a new bulb.
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But the mercury from the standard incandescent lights is not concentrated in my living room.
It can be. Just take any cans of tuna you have from your kitchen and put them in your living room.
Re:My first experience with LED lighting... (Score:5, Insightful)
Any home depot accepts any and all CFLs. In fact, it's easier and cheaper to dispose of CFLs properly than it is of Fluorescents.
Oh, and if your electricity is generated from coal, you are helping put mercury in the air as well.
Re:My first experience with LED lighting... (Score:5, Informative)
Don't lose hope yet. For one thing, a 40 watt incandescant (you didn't specify if what you were replacing was incandescant or CFL) is damned dim to start with. When I used incandescants, the lowest watt bulb I used was usually a 100 watt (60s in closets and in the basement where there's one every fifteen feet), and used 3 way 250 watt bulbs for reading.
A 40 watt CFL would be damned bright, I don't know if I've ever seen one. Most of my lamps have 27 watt twirley tubes. They vary in intensity, in color, in startup time, and some grow brighter the longer they're on. The one on the front porch won't light if the temperature gets below 0F, the back porch light has lit every time. It's also dimmer and bluer.
I'm looking forward to these, but when I finally buy one, I'm not going to pick one that says "equivalent to a sixty watt incandescant", I'm going to get one that says it's equivalent to 100 watts, just to be sure.
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A 40-watt CFL is about like a 150-watt incandescent. Here's a link [1000bulbs.com] to a really bright "compact" fluorescent. It's over a foot long.
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'A 40W incandescent is an excellent light source - brighter than a pretty big fire or the largest candle known to man.'
In home lighting isn't rated against candles or big fires (unless you are looking for mood lighting) its compared to daylight.
'a typical domestic living room is nicely illuminated by 3-4 35W tungsten halogen lamps'
Yeah, I'm sure 110w of HALOGEN would be reasonably bright. But we were referring to indoor lighting. The gas in the bulb would be argon.
Re:My first experience with LED lighting... (Score:5, Funny)
Your friendly neighbourhood CDO neat-freak???
Fixed it for you. The letters are now in alphabetical order. LIKE THEY SHOULD BE!
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"you would need active cooling for a 300 watt halogen."
I'm calling bullshit. I've got a 300w halogen floodlamp. I don't see any fans on it. It's a shell, two ceramic sockets, a reflector, and a cord. I don't see ACTIVE ANYTHING in here.
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Don't trust their "equivalent to..." things. Look at the lumens [wikipedia.org] which is listed for both the incandescent bulb, and the LED bulb.
This rule goes for buying CFLs too: They often over-estimate by about one level. (Ex: A "40-watt equivalent" is really a 25-watt. A "60-watt equivalent" is really a 40 watt. Etc.)
Re:My first experience with LED lighting... (Score:5, Funny)
It's worse than that, mate. Every time you double the distance, the brightess goes down by a factor of four! So, two feet away, the bulb is a quarter as bright as it was a foot away.
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Sweet (Score:5, Insightful)
If they are still not dimmable they still suck (Score:5, Insightful)
Honestly we NEED a led light bulb that will DIM acceptably for people.
most people want to be able to use dimmers and every customer I have wants to use lighting automation.
They need to work on that second right after figuring out how to get the lumens up to that of CFL lamps.
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I wonder if discrete stepping for dimming an LED bulb would work... you know, 5 steps: off, 1/4 of the LEDs, 1/2, 3/4, and all?
I would imagine that you could work the logic into the bulb depending on how much juice it's getting, but then I have a pretty good imagination.
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Actually, you should be able to use a standard dimmer switch on these things. Unless someone is doing something I've never seen before, there's no logic in them, just the diode and a resistor. Maybe a capacitor if they were really ambitious.
I'd expect control with an LED to be much better than an incandescent, because the fact that the 'light emitting' voltage stays relatively constant between the on state and off state, so you should get better effective rangability and control.
Yes, I'm a control systems g
Re:If they are still not dimmable they still suck (Score:5, Informative)
Actually, you should be able to use a standard dimmer switch on these things. Unless someone is doing something I've never seen before, there's no logic in them, just the diode and a resistor. Maybe a capacitor if they were really ambitious.
Nope. LED fixtures on an Edison base incorporate ballasts, just like CFLs, and incandescent dimmers do not work well with any ballast. You are probably making the incorrect assumption that an incandescent dimmer just takes a sine wave with a ~ 170 V peak and outputs a sine wave with a lower peak. It would indeed be easy to create a dimmable ballast if that were the case. But instead these things just cut out portions of the wave creating all kinds of nasties on the house current. This is because it is cheaper to do, and all you need to do to dim an incandescent is to reduce it's average current consumption.
There are a number of solutions to this problem. The one that's most likely to happen is that a new type of dimmer will be created which does something sane for ballasts like reduce the peak voltage, and labeling will be created for both such dimmers and the CFL and LED light bulbs with compatible ballasts. Another solution would be to simply put the dimming entirely within the ballast itself, then the switch would just send a message to the bulb via radio or another out-of-band channel to the bulb circuitry to dim. But while this would be more efficient, this is not going to happen in today's fragmented home automation market without a government mandate, or at least the threat of a government mandate, to standardize.
PS There already are dimmable CFLs and CFL compatible dimmers, I have some in my house. They are not perfect, and both cost 2x as much as conventional CFLs and incandescent only dimmers; and there is no branding to tell the consumer they are compatible. This means you need to do a lot of frustrating web research before you buy the things. I also bought one bright LED Edison base lightbulb to satisfy my curiosity and it was both very expensive and non-dimmable.
PS2 My biggest frustration with buying lighting on the web is that no one shows you a spectral diagram of the light output of the bulbs. If there are any lighting web retailers reading this, please do this and you will win some early adopter business and appear expert in the eyes of even those who don't know what they are looking at. Use, trademark and reasonably license compatibility marks and you will make a killing.
Re:If they are still not dimmable they still suck (Score:5, Informative)
I've not used the commercial LED light bulbs, but standard LEDs dim just fine (at least to a point). I see no obstacle that would stop the bulbs from dimming too.
In fact, a very quick check on the bulbs available at Amazon indicates that they do dim. Is there a dimming problem that you're aware of that's not made clear in the Amazon reviews?
you sir are incorrect (Score:4, Insightful)
"Light Emitting Diodes are binary - either all the way on or all the way off"
You're smoking crack. LEDs can be dimmed just fine, by varying the current going through them. How do you think they control the brightness in LED-backlit LCD displays.
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PWM.
Basic EE: http://letmegooglethatforyou.com/?q=PWM&l=1 [letmegoogl...foryou.com]
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Um, no. A filter would require inductance and/or capacitance, which a PWM driver circuit is notably lacking in. PWM dimming works by running the LED at its rated current for the on-cycle,
Re:you sir are incorrect (Score:5, Insightful)
You're smoking crack. LEDs can be dimmed just fine, by varying the current going through them. How do you think they control the brightness in LED-backlit LCD displays.
While you can dim them that way, they are very picky and inefficient. PWM is much, much more efficient and allows for nearly 1-100% dimming range easily. Getting such accuracy with current is very hard, since it's nonlinear. Most LCD backlighting is done via PWM, there are tons of tiny chips to do this efficiently, for phones too. It's just too easy and cheap not to use PWM these days.
Re:If they are still not dimmable they still suck (Score:5, Informative)
It's hard to take you seriously when you don't know about a SINGLE component in the system.
First, LEDs are definitely variable in a non-binary sense. Anyone who has ever used an LED in pretty much any application ever can tell you that light output can be changed by altering the current.
Second, a dimmer isn't a variable resistor. It cuts the AC waveform, reducing the current available to an incandescent light bulb.
Pulse width modulation is definitely NOT the only way to vary the light output of an LED.
Ok, let's get this thread straightened out. (Score:5, Informative)
(1) LEDs can in fact be dimmed by running less current through them, however their power efficiency drops, which negates the whole purpose of LED lighting. The most efficient way to dim an LED is to strobe it on faster than the human eye can detect By varying with fraction of the on/off cycle that the LED is on, the human eye perceives this as "dimmer". The number of photons averaged over a second is reduced, but for the milliseconds the LED is on it is at full brightness.
(2) Incandescent bulb dimmers are almost never been rheostats, not since maybe the 1920s. The problem is efficiency again. Imagine a certain current flowing through the light bulb and the rheostat; the power dissipated in each device is then proportional to the resistance. When the rheostat is at equal resistance to the light bulb, it is dissipating as much power as the light bulb is! A 100 watt light bulb at 50% of the normal RMS current dissipates 25 watts, which means your rheostat is getting as hot as a small soldering iron. You'd need a massive heatsink to handle this.
Therefore for many years, dimmers were not very practical. The best dimmers were actually transformers, but they were extremely bulky. They were mainly used in theaters and fancy restaurants to soften the shock of the prices on the menu by relief at being able to find them at all.
With the creation of the solid state silicon controlled rectifier (scr), it is possible to do a trick with incandescent bulbs that is rather like the LED strobing trick. What you do is you take the sine wave power and you clip out the parts of the waveform on either side of the peak. So rather than having power delivered to light bulb all the time, the light bulb is only powered for a fraction of the cycle. The difference is that an incandescent filament glows because it is hot; it does not flicker on and off.
Now with respect LED light bulbs, I'm not sure about what circuitry they contain, but they do contain circuitry. If you just plugged enough LEDs in series to plug straight into AC, they'd flicker at a very noticeable 60Hz. If you put a full wave rectifier into the circuit, they'd flicker at 120Hz, which might be fast enough you wouldn't notice the flickering. You'd certainly be able to use the a solid state dimmer to dim such as circuit, but flickering might be noticeable.
There are relatively simple tricks you could use to maybe double the frequency, in which case you probably would not be able to perceive the flicker. On the other hand, there might be fancier circuits that know how to do the right thing. One of the problems with LEDs is that they age, their brightness varies. If the LED bulb achieves its white color by using several different colors, you need a compensating circuit to maintain the original color.
Of course you could use white LEDs, but most of the bright ones are very harsh; I've seen warm white LEDs advertised, but I've never had one.
So there you go, the straight facts on dimming that every geek should know.
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>Now with respect LED light bulbs, I'm not sure about what circuitry they contain, but they do contain circuitry. If you just plugged enough LEDs in series to plug straight into AC, they'd flicker at a very noticeable 60Hz. If you put a full wave rectifier into the circuit, they'd flicker at 120Hz, which might be fast enough you wouldn't notice the flickering.
Speaking as someone who designs LED drivers for illumination, and as such, who has spent tens of hours ripping apart competitors' LED lighting syst
Re:Ok, let's get this thread straightened out. (Score:4, Interesting)
Problem is: any recommendation I make is going to be based on the LED's we have, and most of those are either not for sale yet, or are stupidly expensive. I honestly don't know what commonly available lightbulbs have which LED's, either, because only a few LED's intended for general illumination are easy to recognize. I can tell you that I have great respect for Philips LumiLEDs, Osram Dragons, and most of the stuff Cree makes. I've worked with all those extensively and they're beautiful.
A white/red combo might look okay. It's good for general illumination but still not particularly great for really good color rendition. The problem is that color rendering is dependent on a *lot* of weird stuff. (For instance, part of the reason a ruby is so red is because it's absorbing shorter-frequency light, and re-emitting it as red light, so even if you have a good red source that's lacking in the short-wavelength area, the ruby will look dead. Fish have lots of fluorescent/iridescent coloration, so a standard color rendering index (CRI) test might not tell you what you want to know: will this light look good with this situation?)
With the li-ion, they'll burst into flame, so the manufacturers *have* to put in good charge-controller circuitry. LED's are currently like cars in 1910: you can make anything that sort of vaguely works, and someone will buy it. It's no secret that the LED crowd are hoping so many people will buy them just because they're cool, that they'll jump the early adopter chasm before they've realized that they've mostly bought turkeys.
All the stuff we work with does, essentially, some sort of rectification, then dc-dc conversion, either buck, boost, or SEPIC, and ends up as a constant-current supply for the LED. We (and I'm sure a bunch of other people) have made drivers for really good dimming using standard triacs (ours is just about to hit the market) and they work *amazingly* well. You're limited in part by how well the triac works: a lot of the ones I've worked with have such crappy triggering circuits that the best you could ever get is roughly 60% dimming -- as in, you turn it on, keep coming up, and suddenly the light comes on at 40% brightness. You can then finesse it down to maybe 20%, but it's a pain. Thing is: we can digitize that and do clever stuff in software and come up with something that can essentially accommodate for the crappy triac, learn what it's doing (by sensing how it's chopping the AC) and produce a fabulous dimmer. We have one setup that can dim 10,000:1. If you get 5:1 out of a so-called dimmable compact fluorescent you're lucky. A good dimmer with an incandescent can do something similar: it can start producing heat before there's visible light coming off the filament. But I think only our (and similar) driver can get good performance out of cheap triacs.
With all that said, a cheap triac dimmer driving a cheap unregulated LED will work, but they're (in my opinion) objectionably flickery. A triac dimmer driving a good switching converter (without any detection stuff to try and decode what the dimmer's trying to send) will still dim because you end up starving the switcher when the power's off, but it's icky-looking. In my experience it's even more non-linear than just the cheap triac: when there's enough power it drives well (but as you say at full current/full brightness), and when there's no power it turns off, and in the between situation it thrashes. Most LED driver chips have dim pins so you can apply an external dim signal derived somehow from the signal if you want to add a bunch of external circuitry. (We're building stuff that integrates all that junk into the chip.)
>the idea that you're trying to keep the LEDs at the peak of their efficiency, it seems like a no-brainer.
It is. But very few people will actually *pay* for better circuitry, apparently. So instead we have to add bullet-point functionality to justify more research, and then add in good current regulation and the like as a side-effect of (say) cold-we
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PWM works fine as long as the oscillating frequency is above what the visual system can respond to (IAAVN ... I am a visual neuroscientist). The maximum frequency that the visual system responds to depends greatly on a large number of parameters, including contrast levels, and individual sensitivities, but, generally, the upper limit is about 150 Hz.
If your intention is to draw attention, then 5-to-10 Hz is excellent for this.
If your intention is to make even illumuniation, then oscillating at or above 200
Re: (Score:3, Interesting)
As long as your dimmers are the electronic PWM based kind, LEDs will work with them. (CFL's have issues when they're only given part of the sinewave). If you use the crappy rheostat dimmers LEDs won't work with them.
The only thing I que
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'If you use the crappy rheostat dimmers LEDs won't work with them'
Why not? Adjusting resistance dims and brightens LED's just fine on a breadboard.
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Uhh led lights are dimmable... without flickering and all that... But they are just not bright enough atm to be worth anything.
Clap on? (Score:5, Funny)
I have a Clapper that I've been unable to use with CFL bulbs. I'd like to know whether these new LED lights work with the Clapper and other remote-switching appliances.
Re:Clap on? (Score:5, Informative)
They won't work with the clapper.
Cheap automated switching devices like the clapper and some timers include the bulb as a resistance element in the switching circuit. They count on the bulb acting almost like a short when the light is off. This works with incandescent bulbs, since the resistance of the filament is very low when it is cold. CFL and LED bulbs act exactly the opposite way. They are almost an open circuit when off. With no current flow, the automated switch is unpowered.
There are switches that will work with these types of bulbs, but they generally cost more.
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Thank you. The image of a crack addled addict struggling in a vain attempt to clap some life into a dead CFL bulb is one that I am sure will stick with me the rest of the day.
Whoopie for cold light! (Score:4, Interesting)
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If they can cluster LEDs in a way that simulates natural light (ie, a few at one frequency, a few at another frequency, etc) then I don't see how it's impossible... impossible for a single diode, perhaps..
Re:Whoopie for cold light! (Score:5, Informative)
LEDs have almost nothing to do with antennas, aside from the fact that both emit EM radiation. Specifically, there is no oscillator in the LED. The photons are a direct result of the diode band gap -- each electron-hole pair combining emits one photon with energy equal to the electron charge times the forward voltage (ie a 3V forward voltage LED emits photons with 3eV of energy, aka blue visible light). The Wikipedia page [wikipedia.org] has a fuller explanation.
The reason LEDs produce weird light is that their spectrum is a sharp band, as opposed to the broad hump of a black body. This can be fixed (somewhat) by using a phophor to shift some of that frequency (most white LEDs), but the usual techniques for that leave a gap between the LED emission and the phosphor emission. Better, though more expensive, is combining enough different color LEDs that the narrow individual bands blend together to simulate the blackbody output. Eventually, that will get cheap enough to be common, and then you'll see LEDs in common usage as lighting.
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But I have yet to find truly warm non-tungsten/halogen/mercury/fire/quartz/evil light for home use.
I thought the same for the first week after we started migrating our home to CFLs. I've since come to understand that "warm" is a synonym for "ugly yellow".
British invention (Score:5, Funny)
Are they going to be tiny? (Score:2)
A 15 cm silicon wafer: 15x15=225cm2
If they fit 150000 LEDs you get 225/150000=0.0015 cm2 per led.
Aren't they too small to be used for home lights?
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Wafers are a disk, so pi * 7.5^2 = 176.7144375 cm^2 so you get area/150000 = 0.00117809625 cm^2/led.
Also, 1 LED != 1 LED "lightbulb" is also != 1 LED with package size.
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Wafers are usually circular (since they are sliced off a cylindrical ingot), so the calculation would actually be [google.com]:
( pi*(15cm/2)^2 )/150000 = 0.0012 = 0.12 mm^2
Which is slightly smaller. But this means that each LED is roughly [google.com] 0.3 mm in size, which is about the size of any LED I've ever encountered.
I presume a real lightbulb would require multiple LEDs bundled together somehow. Which is actually cool, because it would allow for more interesting bulb shapes, and should allow for dimming (by controlling how ma
Re:Are they going to be tiny? (Score:4, Funny)
That's just what women SAY to make LEDs feel better, but in the end, they always go home with some huge frosted incandescent with a harsh light. And the day after, they'll be crying to their LED friends about how much energy it wasted the night before, how it kept getting hot and leaving burns on her, and how it burned out after only a few thousand uses. And the LED will listen and be supportive, but you know she'll never give it a shot.
Not that I'm BITTER or anything...
Cheap by what measure? (Score:3, Interesting)
So what is the energy consumed during production for one of these LED lights?
If we're just using more energy per unit during manufacture, then what is the energy payoff balanced vs. the number of hours these will remain in service?
Gallium (Score:3, Interesting)
Aren't we already in short supply of gallium? Do we really want demand for this rare metal that already has so many uses? We have plenty of ways to generate light, let's use one that doesn't require one of our rarest and most useful materials.
Gallium is NOT in short supply (Score:5, Informative)
Never has been, and probably never will be.
Indium and Gallium Sustainability â" September 2007 Update [indium.com]
Big advancement (Score:5, Interesting)
I'm not sure everyone is completely aware of how big an advance this is. I'm going to buy Philips' stock as soon as I can. I'm sorry people have been screwed by some misleading marketing, but LEDs are the future of lighting... and the big green movement.
And yes, they're really easy to dim, either by converting to DC and modulating current, or by using a PWM - I'm not sure which is more efficient/cheaper.
I can't wait for CFLs to go away. Eventually you'll see commercially available, color-selectable LED bulbs.
Anyone know if the process was patented/sold to a specific company? Pretty obvious why...
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Ahh, 5 years... (Score:5, Insightful)
Re:Ahh, 5 years... (Score:4, Funny)
The good ole' 5-year technology promise. Close enough to be exciting and get attention, but far enough away that you'll forget about their claim before they miss their deadline.
I just updated the "desktop" image on my OLED t-shirt to read "PowerVegetable is right on!"
Solar panels too? (Score:3, Interesting)
Aren't some solar panels made with GaN as well? Will this help them too?
Re:Solar panels too? (Score:5, Informative)
Looks likely. Cambridge are researching that too, e.g. both fields are covered by the following grant application.
Details of Grant [epsrc.ac.uk]
Good for displays too (Score:4, Interesting)
This is great news not just for lighting, but also potentially for ILED TVs (basically LED - the "I" stands for inorganic. It would be simpler than even OLED, and the lifetime would be amazing of course.
Lumens per watt is? (Score:4, Interesting)
Granted this is an as yet unrealized technology, but I really wonder what the lumens per watt will be.
For reference a standard 48" T8 fluorescent is about 80 lumens per watt,
Compact fluorescent is around 65 lumens per watt,
and a 60w A19 bulb (the "normal" light bulb) is about 15 lumens per watt.
Cree has some Gallium nitride LEDs that (they claim) produce a record breaking 130 lumens per watt,
but they also have some 100 lumens per watt LEDs and they're also gallium nitride.
Cost of production isn't totally meaningless, but over it's 20 year life, 5 watts means more than $100.
Please research before spreading FUD! (Score:3, Informative)
BZZZT, *WRONG*!!!
According to Energystar.gov: [energystar.gov]