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LED lightbulbs are already available on the market, such as the one shown here (manufactured by the C. Crane Company, available from discoverpower.com) which retails for $34.95 and lasts ten years. DiscoverPower advertises that you can run it 12 hours a day for a cost of 80 cents a year.  (Source: DiscoverPower.com)
New work blazes the trail for LED lighting to take a place in the consumer market

DailyTech has been following the field of solid state lighting.  Solid-state lighting, or using LEDs instead of traditional filament incandescent or fluorescent tube designs, promises long bulb lives, energy savings, and monetary savings thanks to the lower power consumption.  The light bulb, largely unchanged for decades, is finally on the verge of evolving.

Leading the way in the lighting renaissance is the U.S. Department of Energy, which announced millions in prizes in its new "L Prize" competition for solid state lighting.  Its programs also encompassed working with standards organizations to develop certifications and standards for the new devices.

Now researchers with the National Institute of Standards and Technology (NIST) working with experts worldwide have delivered two key standards.  These standards will help legitimize the form of lighting in the commercial industry.  The more recent of the two was completed last month.  The new standards dictate color specifications of LED lamps and LED light fixtures and testing methods for determination of total light output, energy consumption and chromaticity, or color quality.

NIST scientist Yoshi Ohno, who chairs the groups that developed the standards, explains how a little solid state lighting will go a long way, stating, "Lighting uses 22 percent of the electricity and 8 percent of the total energy spent in the country, so the energy savings in lighting will have a huge impact."

The new solid state designs will be twice as efficient as the touted fluorescent bulbs and ten times as efficient as incandescent bulbs.  To put it in perspective, current models can deliver 12 hours of light over an entire year for only 80 cents.  Further, they last ten years.  Over its lifetime, one bulb is advertised to provide consumer savings of over $370.  While most manufacturers are currently in the prototype phase, the technology is incredibly promising.

One additional benefit of LED lighting is color.  Solid state lights can produce a richer more full color than incandescent or fluorescent bulbs.  This can not only help with visibility, but has been shown to psychologically improve mood among many.

The Department of Energy (DOE) has partnered with NIST to achieve the goal of reducing energy consumption by lighting by 50 percent by 2025, by helping to establish LED lighting in the market.

The first standard was the work of the Illuminating Engineering Society of North America (IESNA).  The all-encompassing standard on testing details required environmental conditions, applicable test apparatus, methods of measurement, and how to stabilize and operate the lights during testing.

American National Standards Institute (ANSI) created the second standard C78.377-2008, which covers color standards.  It offers recommendations for color of cool to warm white LEDs with various correlated color temperatures.

This fall the Department of Energy (DOE) will begin certifying LED designs with its Energy Star certification.  This process will be assisted by the NIST-developed standards.  Says Ohno of the need for more standards and the new standards that work towards this end, "More standards are needed, and this will be the foundation for all solid-state lighting standard."

Ohno and other scientist are continuing to work hard on developing more standards.  They hope to soon release a standard on LED lifetime.  Further, they hope to develop an additional standard about performance measurements of high powered LED chips and arrays.



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A bit misleading
By arazok on 6/30/2008 11:44:08 AM , Rating: 3
What you don't tell the readers is that the pictured bulb only produces 60 lumen's of light. A 60W bulb is apx 800 lumen's. In other words, of $30.00 you get a bulb that can be used only as a pen light.

The http://www.ccrane.com/geobulb/index.aspx GeoBulb LED Light Bulb (also from from C. Crane) is 119.95 (!!!) and is an equivalent to a 60W bulb. It uses 8 watts. I can get a CFL to provide the same output using 15W.

You do NOT save money with these bulbs....yet. Give it 5-10 more years.




RE: A bit misleading
By Cogman on 6/30/2008 11:58:17 AM , Rating: 2
This is true. but considering how closely linked LEDs are to the computer manufacturing process, I don't think it is too far in the future. (2 years maybe) before these things become affordable. Eventually I see them becoming cheaper upfront then CFLs.


RE: A bit misleading
By daftrok on 7/1/2008 2:24:41 AM , Rating: 2
Lumens are a tricky business. The thing with incandescent and compact fluorescent light bulbs is that they aren't directional lighting, they glow. Here is a better option:

http://www.ccrane.com/lights/led-light-bulbs/cc-vi...

Its meant to be pointed in one direction and 150 lumens is more than enough for ceiling lights.


RE: A bit misleading
By mindless1 on 7/3/2008 4:48:14 PM , Rating: 2
That linked light is not sufficient for lighting much, 150 lumens is not even close to enough for ceiling lights. Obviously you don't have one nor much experience implementing LED lighting.

Also, the price is ridiculously high for what it is. 30 typical LEDs should not cost remotely close to $30, let alone $40. A hobbyist could build such a light except for the glass-like housing for less than that.


RE: A bit misleading
By rudy on 7/1/2008 4:17:06 PM , Rating: 2
maybe but standards is a real issue.

CFLs are great cause they save money and do not have the flicker but they are expensive because they must have the base to work. What really needs to happen is for a CFL bulb only with no base standard to come forth where the base is in the socket as is the case with incadecent bulbs and you just screw or slip a florecent tube in and it runs at a high frequency to reduce flicker. Then CFLs would easily come down in price to near incadecent bulbs and there would be much less waste.


RE: A bit misleading
By rudy on 7/1/2008 4:19:01 PM , Rating: 3
I should also add hopefully they will be going toward that with LEDs, wouldn't it be much less wasteful if the individual LEDs could be replaced but the back electronics would be built into lights and sockets. This would also allow you to upgrade LEDs when more efficient versions come out.


RE: A bit misleading
By mindless1 on 7/3/2008 4:54:30 PM , Rating: 2
Actually no, the cost of the driver circuit is negligable compared to the cost of enough LEDs to provide whole-room lighting. Modularizing individual LEDs or arrays would just increase cost over having the whole thing as integrated as possible.

A better idea for cost savings would be to do away with the whole incandescent screw bulb type design instead opting for panel lights that the AC wiring is directly connected to, allowing for a larger surface area to more effectively mount and keep an array of LEDs cool - decent LEDs not the weak products C.Crane is selling. You simply cannot light up a room sufficiently with a mere 10W worth of LEDs, not even 20W to the standards of most people already accustomed to enough light to make the comparitive average energy savings calculations true.


RE: A bit misleading
By UNHchabo on 6/30/2008 12:04:54 PM , Rating: 2
60 lumens is not a pen light. Surefire (my personal favorite flashlight company) makes 60 lumen flashlights that are bright enough to be used as "compliance" devices in law enforcement.

http://www.surefire.com/maxexp/main/co_disp/displ/...

Granted, I know that the perception of brightness is greatly affected by unidirectional vs omnidirectional light, but if I point my flashlight at the ceiling, I get enough light to read a book. 60 lumens would probably be too bright for a desk lamp, though.


RE: A bit misleading
By masher2 (blog) on 6/30/2008 12:34:40 PM , Rating: 3
> "60 lumens would probably be too bright for a desk lamp, though. "

I used to have 40-watt bulbs in my desklamps, which put out nearly ten times that (500 lumens). I replaced them as they were all too dim.


RE: A bit misleading
By danrien on 6/30/2008 2:54:19 PM , Rating: 2
quote:
Granted, I know that the perception of brightness is greatly affected by unidirectional vs omnidirectional light, but if I point my flashlight at the ceiling, I get enough light to read a book. 60 lumens would probably be too bright for a desk lamp, though.


Right, so if you combine a few of these, you would get a comparably bright omnidirectional light. I know that in class I have worked with some incredibly bright LED's that can cause some "blind spots" in your vision for a few seconds by looking directly at them... however, their ability to spread that light can be fairly weak compared to conventional lights.

But I mean, who doesn't get bothered by Blue LED's?


RE: A bit misleading
By zsdersw on 7/1/2008 6:32:16 AM , Rating: 2
quote:
But I mean, who doesn't get bothered by Blue LED's?


It depends on the application. :) My car has them in the overhead console.. they shine down at night, giving a very cool blue color to the car's interior. It's ambient lighting.

Obviously, though, you wouldn't want to stare directly at it.


RE: A bit misleading
By mindless1 on 7/3/2008 4:59:28 PM , Rating: 2
Have you used proper die-on-star LEDs or only the little plastic encapsulated ones? They are both already binned for color so you don't have to have blueish cast to the LED, although the more blueish the tint the more total light is produced if all else were equal.

60 lumens isn't remotely close to enough light for a desk lamp. My LED bike light produces over 5 times that and it "might" be close to bright enough depending on the user/use.


RE: A bit misleading
By Cobra Commander on 6/30/2008 12:10:18 PM , Rating: 2
I would consider that very misleading, but I only speak for myself. Glad other brains are in the building to finish the story when necessary. Thanks.


RE: A bit misleading
By Souka on 6/30/2008 12:10:57 PM , Rating: 4
Another advantage of LED lights is the tolerance to being turned on/off.

Incandecent bulbs might be rated for 2000hrs life..but that typically a 24/7 burn time, or 12hr-on 12hr-off.

CFLs might claim to be longer lasting, but if you frequently turn the light on-off you'll experience a short life, not to mention the light color/intensity changes during warmup...

I look forward to LED lights...but will stick with incandecents for now (with a few CFLs on lights left on long durations)


RE: A bit misleading
By kmmatney on 6/30/2008 12:44:22 PM , Rating: 4
IMO, the CFLs have gotten a lot better. I now use them in places where they are contanstly being turned on and off (e.g. recessed lighting in the kitchen) and I haven't come across any lifetime issues with the current generations of CFLs. The only annoying thing is the warm-up time, so a do tend to mix in a few incandescants. I have several different brands of CFLs and some start up quicker than others.


RE: A bit misleading
By kattanna on 6/30/2008 1:20:07 PM , Rating: 3
we have replaced all lights in our place with CFL and enjoy them very much. and while others seem to have an issue with the not full intensity when you first turn them on, we have in fact liked that very aspect of them so in the moring, i get up in the dark, or at night when it is dark, you dont have that glaring suddenness of total light from darkness.


RE: A bit misleading
By PrinceGaz on 6/30/2008 1:31:25 PM , Rating: 2
I agree 100% with you. I consider it a plus that with CFL bulbs you get a sort of dimmer-like startup increase in brightness rather than being dazzled first thing in the morning. If I were to switch to LED lighting, I'd prefer to be able to buy bulbs that electronically increase to full brightness in a similar way.


RE: A bit misleading
By TomZ on 6/30/2008 3:14:27 PM , Rating: 2
I agree, but I think that in many other circumstances, it is annoying. For example, we put CFLs in a lot of the fixtures in our home, and while some have been "well received," others have been rejected by my family. For example, in the bathrooms and part of the kitchen, everyone agreed that the warm-up time was really annoying, and we switched back to incandescents.

In our halls, the basement, and in my office, the CFLs were okay. These lights tend to be on for longer. Also, a lot of the bulbs that were replaced with incandescents were the more fancy/decorative shapes, and I think the CFL technology is not so well-developed for those as for the standard shape. Consequently, non-standard bulbs seem to have longer warm-up characteristic, at least in my experience.


RE: A bit misleading
By Oregonian2 on 6/30/2008 2:29:47 PM , Rating: 3
quote:
Incandecent bulbs might be rated for 2000hrs life..but that typically a 24/7 burn time, or 12hr-on 12hr-off.


Actually turning incandescent on and off isn't a significant problem in terms of lifetime. Having them burn out when turned on is I think the source of the misconception. They would have burned out soon anyway (probably had developed a thin-spot on the filament due to it being evaporated off (black stuff on the inside of the bulb)).

I once didn't believe that, but had built a tester that turned on and off bulbs (mechanical, flipping a switch back and forth) and tested some high powered incandescents. They were give time to cool in the off cycle, but "on" time was fairly short (few minutes). A pile of bulbs all still failed at about the rated number of hours. Turning on breaks the camel's back, but the back was already fatally damaged. The testing took a few weeks to run.

Now CFL's are a problem with frequent on/offs....


RE: A bit misleading
By Souka on 6/30/2008 11:27:59 PM , Rating: 2
Welp I seem to recall a Mythbuster's episode in which they had a wide array of incadecents of differnt types, CFLs of different types, and even an LED model.

All but the LED failed LONG before the rated hours were reached.

I do not recall the specific on/off cycle, but I think it was somehting like 1 min on, then 1 min off...cycle running 24/7. They further backed their data with that of some other sources. . .

Also, I'm sorry, but I really don't believe your "test"...here's why...

If what you say is true, you ran your tests for almost 6 months for a 2000hr incadent bulb... or 30 months for a 10,000 hr CFL. (this is based on %50 on, %50 off cycle)
(Typical CFL last 6000-15000hrs, and typical incandecent are 1000-2000hrs...so say Wiki).

My $.02


RE: A bit misleading
By zsdersw on 7/1/2008 6:35:59 AM , Rating: 2
Yes, I saw that episode as well. That LED light bulb was pretty neat.. I think I found the exact same one in a catalog or on a website somewhere for like $70-80.


RE: A bit misleading
By Oregonian2 on 7/1/2008 1:26:28 PM , Rating: 2
I ran the tests on a higher powered bulb that had a lifetime rating of only a few hundred hours which is why it didn't run excessively long. It also wasn't me "personally" it was for a company I worked for at the time (as an electronic engineer, although I was a newbie engineer back then).

If that episode used only one minute off then that may be a significant difference (although I'm not sure why). That's not long enough for a full cool-down. I had allowed a full heat-up and full-cooldown to simulate long term intermittent use, but to do it as quickly as possible. Minute-on-minute-off would be simulation of a Christmas display or something like that.

That said, my results also agreed with a nationally famous professional engineer (at that time which was about 30 years ago) having to do with the failure mechanisms in incandescent light bulbs. Now, we're talking standard tungsten bulbs, not necessarily halogens or other technologies which may have different failure mechanisms. Standard incandescents are ancient technology.

In any case, I did the study and I gave the results of it. If you think I'm lying, so be it.


RE: A bit misleading
By mindless1 on 7/3/2008 5:11:34 PM , Rating: 2
You're not talking about a typical filament and that few hundred hours is an atypically low, terrible lifespan.

Bottom line is the typical incandescent used in most places has substantially shorter life from cycling on and off constantly, and whether it is allowed to completely cool for over a minute off or not is fairly irrelevant, a trivial change in temp relative to the filament temp change on what most would call a standard fixture bulb for home lighting.


RE: A bit misleading
By mindless1 on 7/3/2008 5:08:10 PM , Rating: 2
Actually yes, turning them on and off is the most significant determining factor. The cold low resistance causes a rush of current and rapid expansion which changes the shape of the filament in a progressively damaging way each time it happens, not so much how long it is hot.

I don't believe your test was accurate at all for typical incandescents, something was seriously amiss because they all last a longer # of hours, much longer, much much much longer if left on than turned on and off frequently. Much.


Power factor
By bobsmith1492 on 6/30/2008 12:00:38 PM , Rating: 5
The other thing being ignored in the push for higher-efficiency lighting is the power factor and its effects on the grid.

Incandescent bulbs have a perfect power factor, acting as a pure resistance.

The power supplies in CFL and LED bulbs use a basic rectifier->capacitor input to generate high-voltage DC that is then switched to the proper levels for the lighting device in question.

The problem is that the rectifier->capacitor input only takes current from the very peak of the AC waveform. This has two effects: 1. introducing noise into the power lines and 2. decreasing the power factor.

With a lower power factor, more current must be supplied than is indicated by the real power measured. This current increase means more power is wasted in transmission and, in effect, the transmission system efficiency is reduced.

So, while less power is used at the point of consumption (the LED or CFL device), more power is wasted in transmission. Essentially these bulbs aren't as good at saving energy as is claimed - plus they are electrically noisier.

Something to think about to dampen the enthusiasm for electronic lighting.




RE: Power factor
By Cobra Commander on 6/30/2008 12:11:19 PM , Rating: 3
All the more reason to switch to DC, right? :)


RE: Power factor
By bobsmith1492 on 6/30/2008 12:37:46 PM , Rating: 2
I think Tesla and Edison already argued this one out and we all know who won... ;)


RE: Power factor
By JBird7986 on 6/30/2008 1:24:24 PM , Rating: 2
Actually, I believe it was Edison and Westinghouse...not Tesla.


RE: Power factor
By masher2 (blog) on 6/30/2008 1:44:02 PM , Rating: 2
Actually, it was Edison vs. Tesla and Westinghouse. It was known as the "battle of the currents".


RE: Power factor
By sprockkets on 6/30/2008 2:40:49 PM , Rating: 2
AC is better for distance, DC is better though for everything else.

I propose that devices that actually use AC but turn it into DC should also have a DC plug too. Computer power supplies are a prime example. Why use a UPS that changes their 12v DC battery to 120v imperfect sine wave AC, only to be changed right back to 12v DC?

If everything ran on 12v DC and was fed from the power company, we would lose too much due to line resistance. But if this was fed from your solar panels, which is what they output, getting rid of the 12v to 120v AC converter (forgot the proper term for it, rectifier?) makes sense.


RE: Power factor
By Nyamekye on 6/30/2008 7:22:45 PM , Rating: 5
A better idea would be to have a power supply built into every home capable of supplying the raw dc current needed to power any device on the market using the high voltage ac line from outside.

Sadly, I doubt our current system will ever change.


RE: Power factor
By Jellodyne on 7/2/2008 1:29:37 PM , Rating: 2
'Current system' -- I get it!


RE: Power factor
By monitorjbl on 6/30/2008 12:38:08 PM , Rating: 2
While what you're saying may be true, power companies have to deal with stuff like this anyway in certain situations. Since your power factor is a result of the real and imaginary power you're using if you use a lot of non-linear resistors in your building like AC motors, you'll be changing the power factor to a non-ideal state.

Basically, your power load can be viewed as having a real and imaginary component. Any circuit components that change your imaginary component from 0 (capacitors/inductors) tend to muck up things for the power company. There's a certain amount of wiggle room built into the system, but power companies will have a limit on your power factor that you must adhere to. Most people won't have much trouble with this in their houses. I could go into excruciating detail on most of this, but the general idea is that a lower power factor will cause the power company to pump more current into your building, losing them money.

Your power company will come in and put either an inductor or a capacitor in parallel with your building's power supply to cancel out the imaginary component enough to meet their standards. Granted, it does require a little bit more work to use these things en masse, but it isn't really a new problem.

If you want to know more about how imaginary power works, either get an EE degree or read Wikipedia:

http://en.wikipedia.org/wiki/AC_power
http://en.wikipedia.org/wiki/Power_factor


RE: Power factor
By bobsmith1492 on 6/30/2008 6:10:43 PM , Rating: 3
I have an EE degree...

The current waveform from a AC->DC supply via diode and capacitor does not create a simple, shifted current waveform like a pure capacitive load does. Hence it cannot be corrected for by classic passive means (inductor/capacitor load). It has to be corrected at the source, as in computer power supplies.


RE: Power factor
By masher2 (blog) on 6/30/2008 1:09:58 PM , Rating: 4
> "So, while less power is used at the point of consumption (the LED or CFL device), more power is wasted in transmission"

Well, not really. The PF for most residences is normally inductively biased, due to all those big motors in washers, a/c units, and vacuum cleaners. That means any capacitive load you put on the system is going to tend to cancel that out, and help correct the PF back to zero.


RE: Power factor
By bobsmith1492 on 6/30/2008 6:07:13 PM , Rating: 2
The load from a rectifier->capacitor is not the same as a purely capacitive load, though. Current is only drawn at the tips of the voltage wave as opposed to shifting the entire current waveform ahead of the voltage waveform.

You can't correct for the current signals placed on the line from an electronic load once it's there; PFC has to be performed at the load.

Now, if someone came up with a dirt-cheap, PFC AC->DC supply... maybe I'll take a crack at it. :)


RE: Power factor
By repatch on 6/30/2008 3:02:31 PM , Rating: 2
Some jurisdictions are already considering this problem.

The solution is called PFC - Power Factor Correction.

It's generally very simple to add PFC to CFL or LED driving circuits, and while it does increase cost, when mass produced the cost will be negligible.

That said, I think to single out lighting for power factor issues is unfair. Almost all electronics have poor power factors. Pretty much all electronics use switching power supplies without any PFC, so if this is an issue it should cover all sources.

TTYL


source?
By tastyratz on 6/30/2008 2:13:44 PM , Rating: 2
quote:
One additional benefit of LED lighting is color. Solid state lights can produce a richer more full color than incandescent or fluorescent bulbs. This can not only help with visibility, but has been shown to psychologically improve mood among many.


Do you have a source for this?
Solid state lighting is actually the opposite of what you put here. Led lights tend to have a very restricted color reproduction range making for harsher bright lights with no positive effects on mood and sleep cycles via light therapy.
This is actually one of the NEGATIVES of current generation solid state lighting.




RE: source?
By TomZ on 6/30/2008 4:55:12 PM , Rating: 2
quote:
Led lights tend to have a very restricted color reproduction range making for harsher bright lights with no positive effects on mood and sleep cycles via light therapy.

Do you have any sources for that?

Personally, I like the color tone of the LED lighting I have seen so far. I don't recall if it put me in a bad or good mood, though. Probably neither.


RE: source?
By Nyamekye on 6/30/2008 7:32:57 PM , Rating: 2
LED lights are capable of producing a more rich and full color than regular incandescent or fluorescent bulbs.

For example - the white incandescent or fluorescent bulb you brought is actually more yellow in color. If you brought the white LED light it would actually be white in color.

Just look directly at your light an you can clearly see it has a yellow aura around it and not a white one. When looking at a white LED light the aura would be pure white - not yellowish...


RE: source?
By Zoomer on 6/30/2008 11:30:28 PM , Rating: 2
Yes - for some reason, they only make these terribly warm spiral/compact cfls. I'd like to get something way cooler, above 6500k.


RE: source?
By josebl on 7/1/2008 12:06:49 AM , Rating: 2
Yeah, when Jason writes:

Solid state lights can produce a richer more full color than incandescent or fluorescent bulbs. that is incorrect. Incandescent light is a continuous "black body" radiator with continuous spectral distribution throughout all visible wavelengths. It's true that incandescent light is biased to the ROY section of the ROYGBIV spectrum. In fact 80% of an incandescent light source is emitted as infra-red wavelengths, hence why they are so inefficient.

"White" phosphor coated LEDs use a down conversion strategy similar to fluorescents. High quality fluorescent light is achievable which tri-phosphor coated tubes up to 95+ CRI (color rendering index) --- at around a 15x price premium. This is out of a scale of 1 to 100, with a certain amount of subjectivity assigned to the score. Standard consumer T12 fluorescents are dual phosphor and range from @60-85 CRI.

The NIST standard, dubbed CQS (Color Quality Scale) is an update to the CRI index. Essentially RGB LED fixture manufacturers vocalized concerns that the CRI was inaccurate when gauging the color quality of their fixtures, so the NIST developed a new metric, to encompass the new technology. An overview of the NIST CQS work this article covers is here:

So here's the source:

http://physics.nist.gov/Divisions/Div844/facilitie...


RE: source?
By mindless1 on 7/3/2008 5:18:11 PM , Rating: 2
LED lights can use any and all spectrums that the manufacturer perceives the public will buy, they have total control over whether the color is richer and fuller or not. However, the more deviation there is away from blue, the less useable light per watt input.


LED lighting is real and here today
By JeffS on 6/30/2008 3:28:43 PM , Rating: 4
The 60-lumen lamp shown in the photo above is a poor example of state-of-the-art LED lighting. Take a look at the following products:

http://creelighting.com/index.aspx

LED Lighting Fixtures (now Cree) offers the LR6, which addresses nearly every concern mentioned in this discussion. Unlike CFL, it has near-perfect power factor and is dimmable. Unlike the small bulb shown in the article, it puts out a lot of light- LLF claims 650 lumens, but I think it's brighter than that- and the color temperature is excellent. You can get it in either "warm" or "cool" white; they have some technology that gives you a very pleasant warm color rather than the too-blue hue that white LEDs are known for. Best of all it only draws 12 watts (I measure 10 using my own power meter at home).

I said I think it's brighter than 650 lumens. That's because I replaced an incandescent lamp with one of these and got notably more brightness in my work area.

I bought my LR6 from a local lighting store for about $80. The light quality and the long life make it worth it to me. It's also a no-brainer for high ceilings where changing a bulb is a big hassle.

High quality LED lighting technology is here today. It will undoubtedly get more affordable, but if you are a lighting enthusiast, try out one of these devices. And, no, I don't work for them.




RE: LED lighting is real and here today
By jimluu on 6/30/2008 6:57:47 PM , Rating: 2
I wonder how these LED handle voltage fluctuations. My lights flicker once in a while during a lighting surge, will the LEDs be more prone to blow outs?


RE: LED lighting is real and here today
By Zoomer on 6/30/2008 11:38:34 PM , Rating: 2
The reticifier should take care of that.


By mindless1 on 7/3/2008 5:20:06 PM , Rating: 2
Perhaps you mean that the driver circuit beyond the rectifier will take care of that, since a rectifier itself will not take care of that at all.


By tastyratz on 6/30/2008 11:36:24 PM , Rating: 2
WOW is that cree expensive.
Yea LED is definitely here today, but as you can see looking there that legitimate implementations are far from economical. I certainly cannot wait till its beyond practical!

Source?
Here's one of many
http://ledmuseum.home.att.net/spectra.htm

LED apparent brightness can be higher because the distributed lumens are in a range more sensitive to the human eyes perception. Infrared reproduction and others goes simply downhill however when switching to a solid state source. Sure it produces the most visible light lumen for lumen to the human eye, but it is not the most natural and usable lighting source yet.


lumens vs luminous intensity
By Integral9 on 7/1/2008 9:03:47 AM , Rating: 4
I think many people here are confused about light output and intensity. Hope this helps.
http://www.gizmology.net/LEDs.htm

Luminous flux and luminous intensity are measurements like radiant power and radiant intensity, only adjusted for the sensitivity of the human eye. Radiant power of a wavelength of 555 nm is multiplied by a factor of 1, but light of higher and lower wavelengths are multiplied by lower factors, until infrared and ultraviolet wavelengths are reached, when the radiant power is multiplied by zero.

Luminous flux is measured in lumen, while luminous intensity is measured in lumen per steradian, also called a candela.

The relationship between luminous flux, luminous intensity, and beam angle means is that focussing a given LED into a tighter beam (decreasing the beam angle) will increase its luminous intensity (brightness) without actually increasing the luminous flux (amount of light) it puts out. Keep this in mind when buying LEDs for illuminating purposes - a 2000 mcd 30° LED puts out just as much light as am 8000 mcd LED with a 15° viewing angle. (The angle is half in both width and height, so the beam is four times as bright.) This is one of the reasons that ultra-bright LEDs are often "water clear", to keep the light going in one direction and not diffuse it all over the place.

The brightness of LEDs is measured in millicandela (mcd), or thousandths of a candela. Indicator LEDs are typically in the 50 mcd range; "ultra-bright" LEDs can reach 15,000 mcd, or higher (the 617 nm Luxeon Star (part number LXHL-NH94) can reach 825,000 mcd).

By way of comparison, a typical 100 watt incandescent bulb puts out around 1700 lumen - if that light is radiated equally in all directions, it will have a brightness of around 135,000 mcd. Focused into a 20° beam, it will have a brightness of around 18,000,000 mcd.




Dimmers ?
By Silver2k7 on 7/2/2008 1:13:18 PM , Rating: 2
"The new solid state designs will be twice as efficient as the touted fluorescent bulbs and ten times as efficient as incandescent bulbs. "

the 'fluorescent bulbs' my guess is those are the same as energy savings bulbs are called here.. they can't be used when you have a dimmer.. right.. atleast my grandfathers dimmer burned up when he tried that.. never really knew that could happend.

So can these new LED lightbulbs be used with a dimmer ??




RE: Dimmers ?
By mindless1 on 7/3/2008 5:26:38 PM , Rating: 2
Depends on which specific LED bulbs you are calling "these new LED bulbs". Yes some can be dimmed, and some can't. The cheaper designs generally can be dimmed with a standard dimmer, while the current controlled types would need a digital input not present in a standard controller.

However, let's put it in context. You're paying dozens of dollars for a suitable output LED "bulb", it would not be that big a deal to get a different dimmer if/when the need arises though digital signaling dimmer and circuitry in the bulb itself is contrary to the goal of decreasing cost as much as possible to spur wide adoption rates.


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