LED's for beginners

[icecow]

http://www.instructables.com/id/E9NFEFO2ZGEV2Z9QKZ/?ALLSTEPS

[tlf9999]

good experiments.

two comments:

a) 20ma is a little too much for the regular leds (20ma is usually the maximum current they can take), and a little too little for the super bright types (they usually start at 50ma).

b) you really should use a current source, rather than a voltage source to drive an led. the easilyst is to use a 3-terminal voltage regulator and configure it as a current source, or if you want to control their brightness, a 555-pwm generator (or one of those pwm controllers for smps).

[Bobcrane]

If one wanted to invest in LED technology what would be a good company to invest ones money in?

[tlf9999]

I am not sure why one would invest in led: it is very commodity game now, and the bulk of the leds, including smd types, is made in China now and only a low-cost producers would win.

you may want to invest downstream, into applications where LEDs are used. for example, lighting manufacturers who use LEDs for automotive applications (it is only a matter of time before all interior and non-frontal lights to be LED based), home applications - long-life LED bulbs, display panels, portbal devices.

and you may also look into alternative technology (OLED) as well.

[icecow]

Much like 'they' genetically modify cats and dogs, LEDs are getting bigger.

Giant mutant LED bulbs are expected to overthrow the flourecent light bulbs' evil hold on home lighting. Such LED lightbulbs are availible today, but are presently still more costly then flurecent bulbs. Each year the lumens/watt efficiency of big LED bulbs increases, as manufacture costs decrease.

LED bulbs last like twice as long as florecent bulbs, but don't blink 59.x times a second, or deal with freaky argon gas (or equivlant gas), weird phosphorus, and the fourth state of matter: plasma. LEDs don't buzz. They run very cool.

As the manufacturing cost plunges I expect to see them invade society like the spiral flurecent bulbs did.

I'd think home lighting LEDs to be a good investment. LEDs are going through a phase of technological improvements that will continue for years. When and who to invest in I don't know. Sometimes the big $ in mass produced things like cpus or LEDs is not investing in the company that sells the chips, but investing in some arcane part of the manufacturing process that is over most peoples heads. Made up example: invest in a company that makes machines that aligns the LEDs during the manufacture process (made up).

You'd probably be going with some korean company, which might also protect you from the flimsy US dollar.

some links:
http://techon.nikkeibp.co.jp/english/NEWS_EN/20061221/125713/
http://www.physorg.com/news72629783.html

[tlf9999]

LED bulbs last like twice as long as florecent bulbs,

it depends on how you use the bulbs. florecent bulbs really have unlimited life, as long as you don't turn it off: its life is limited by the # of starts.

LED can last 100,000 hours but usually starts to dim after 50-75K hours, especially for the super brights.

As to blinking, well, not sure how that matters.

[dhodory]

[QUOTE=icecow]
LED bulbs last like twice as long as florecent bulbs, but don't blink 59.x times a second, or deal with freaky argon gas (or equivlant gas), weird phosphorus, and the fourth state of matter: plasma. LEDs don't buzz. They run very cool.
[QUOTE]

Based on several years working around (not an engineer, but spent a lot of time around them) LEDs, I'd like to make a couple of small adjustments to your above statements. I may, in fact, be incorrect -- as this information is about 12-18 months old, and LEDs are on a semi-conductor-like improvement/change curve with light output/efficiency doubling every 18 months or so.

Almost all LEDs use a phosphor coating of some kind. In fact, when people who work with LEDs refer to the color gamut that a particular range of LEDs produce, they generally refer to the phosphor coating type to refer to the LED. For example, whilte LEDs in use today are typically a 450-470 nm blue GaN (Gallium Nitride) covered in a yellow phosphor made of cerium doped yttrium aluminum garnet (YAG:Ce). Some white LEDs are actually made by using UV emitting diodes (i.e. no visible light) covered in very specific combinations of phosphors (I'm no optical engineer, but my understanding is that when the UV rays/particals go through the phosphor and excite the phosphor, wavelengths of visible light are generated from this combination in much the same way that a flourescent light generates visible light --> no phosphor = no visible light).

Contrary to conventional belief LEDs do, in fact, generate quite a bit of heat. They do not generate this heat, however, in the manner in which we are accustomed to seeing/feeling it. Typically, when you turn on an incandescent or halogen light, you can put your hand 6-9" inches away from the bulb and feel the warmth. With an LED, this conversion of electricity to heat just doesn't happen in the same way (and to your point, it does happen to a slightly lesser degree -- LEDs enjoy a much higher lumens per watt ratio for precisely this reason, more energy gets converted to light, hence, higher lumens/watt -- at least that is my "I'm not a lighting engineer, but I DID sleep at a Holiday Inn Express last night" understanding). LEDs generate their heat at the diode/exciter level, and generally speaking, this heat is radiated back into some sort of heatsink (generally speaking the heat gets radiated back to wherever the diode is mounted). In fact, a critical factor for LED longevity is maintaining a "junction temperature" (the point where the diode is mounted on the die) of below N degrees centigrade. If you manage that thermal load properly, LEDs will last for-freaking-ever (think 20,000-40,000+ hours at very specific and strict light output levels). As soon as that junction temperature rises above N degrees, the light output capabilities of the LED are compromised and degredation happens at a fairly consistent rate.

Sorry for the long reply . . . I just think LEDs are really nifty. Unfortunately, a lot of the benefit to be had from using LEDs (i.e. much lower electricity useage) will only be seen by re-wiring existing buildings (LEDs have much lower wattage requirements and using a step-down converter/transformer ends up wasting the excess energy as heat) or for new construction (i.e. homes or building that can be built with lower wattage/voltage wiring from the get-go).

[tlf9999]

[QUOTE=icecow]
In fact, a critical factor for LED longevity is maintaining a "junction temperature" (the point where the diode is mounted on the die) of below N degrees centigrade.

that's true. like all semiconductor products, junction T is very important. However, the usual issue with LED lighting products isn't how much heat they generate but how little heat they do. For example, led-based traffic lights are specifically designed so that the optics wouldn't accumulate snow and if there is accumulated snow, it can be melted by the (little) heat from the leds.

(LEDs have much lower wattage requirements and using a step-down converter/transformer ends up wasting the excess energy as heat) or for new construction (i.e. homes or building that can be built with lower wattage/voltage wiring from the get-go).

they are done with DC/DC or AC/DC converters usually. This is true with truck/autom based lighting as well.

[icecow]

Logically, ideally, it would make more sense to wire a home DC and have AC run to the home.

In chicago I want a little heat from lightbulbs.

In california.. I want the coolest bulbs I can get

[slowbiscuit]

When will we start seeing LED light bulbs as a replacement for compact fluorescents in the home? I like the latest gen of CFs that start instantly but they still put out a decent amount of heat in the >20 watt varities. I just bought some more at Home Depot and looked but didn't see any LED equivalents in the same 'energy saving' bulb section of the store.

[gduprey]

I've been an LED nut since I was a kid and LEDs were dim, guttering red-only affairs. As soon as any new tech comes out with LEDs, I've got my hands on them. Recently I've played with some incredible 10watt white LEDs that throw off blinding amounts of light, but also a huge amount of heat. If you don't mount those to a great heat sink, the think will cook itself to death in a few minutes. But there is no doubt the day of all LED lighting is on it's way -- probably in a few more years (there is a lot of drive/money behind that goal out there).

Where I really get excited about them is in full-spectrum use. Since LEDs are easy to produce in different colors, you can produce a high powered red, green and blue LED which, with proper controls and mixing, can show any color in the rainbow. In fact, one of my fun (for me) side projects has been creating a controller for driving RGB LEDs so I could start putting them in all over the place and having them do things like change colors for moods, to indicate changes in the house or just generally be cool (you can download all the schematics/firmware/etc at www.rgbled.org).

We're now to the point where RGBLEDs are capable of doing reasonable exterior architectural wall washing and such (i.e. lighting up big areas). Just 2 years ago, that wasn't practically possible. In fact, at least one company is coming out with a rear projection TV (using DLP technology) where the light source is RGB LEDs. There is a single imager, so the flash red, green and blue on the imager really, really fast. Most such systems today use an expensive high powered light and a spinning color wheel to achieve the same effect. There is some hope we'll see full on front projection units with LED light engines within 5 years or less.

My goal is being able to come up with replacement light bulbs with R, G and B LEDs in them, along with a controller in the bulb package and the ability to be commanded over the powerline (or via RF). Screw it into a standard light socket and every light in the house could be any color (including white). While you may think of cool things like bathing the house in blue for a cocktail party, there are other subtler effects like changing the tone of the "white" light ("warm" it up for evenings with friends, "cool" it down for doing work/cleaning, make it more golden at twilight, etc, etc).

Anyway, not a lot to add, but one of my favorite topics mentioned in one of other favorite topics, so I couldn't resist :-)

Gerry

[sixt7gt350]

<snip>
you may want to invest downstream, into applications where LEDs are used. for example, lighting manufacturers who use LEDs for automotive applications (it is only a matter of time before all interior and non-frontal lights to be LED based), home applications - long-life LED bulbs, display panels, portbal devices.

<snip>
<emphasis added>

Don't be so quick there. Frontal illumination is also being investigated and applications are expected to see market in 2008.
Due to their extremely efficient conversion of electricity to light, they make sense as a way to save fuel. (Don't forget that the alternator charging the battery from all the electrical devices on modern vehicles is worth a few horsepower.)

P.S. I'm with Gerry. I can't begin to remember how many LEDs turned to smoke in my young hands.

[tlf9999]

Don't be so quick there. Frontal illumination is also being investigated and applications are expected to see market in 2008.

frontal applications for LED was demo'd by Infiniti, a Borsch design that has multiple LED sources and coupled optical system so that one can change beam pattern, hi-lo beam, or "turn" the beam left or right, up or down by lighting different LEDs in the system.

I am not sure if it will come to market in 2008. my guess is that we need another 5-yr or so before any frontal applications are feasible from technology point of view and then a few more years for that to be feasible cost-wise.

LED-based side markers, safety lights and illuminators are today widely used on trucks, not for cost reasons but for asset utilization reasons.

the energy savings from switching to LED are minimum (non-consequential), even on a truck which has far more lights than a car.

[tlf9999]

When will we start seeing LED light bulbs as a replacement for compact fluorescents in the home?

a typical 5-LED portable light (10-15w equivalent light output) has a manufacturing cost of about $4. of that, $3 go to the LED and electronics. so a 60w-equivalent LED light bulb would use 4-6x as many LED bulbs, and will likely cost you $12 - $18 in the electronics, likely $25 in manufacturing costs, and about $50 - 75 when sold to you by the retailors.

At that price, it has zero market.

[tlf9999]

We're now to the point where RGBLEDs are capable of doing reasonable exterior architectural wall washing and such (i.e. lighting up big areas). Gerry

there was an interesting article in the last couple weeks about that very topic and people are getting quite excited about it. the concept is to do all-wall lighting (2-dimensional lights vs. point / 1-dimensional lights we have now). and the thought is that it may go to a printable LED (not yet mass-produceable) that one can just "tape" to the wall as we do today will wall-paper.

pretty exciting stuff.

[sixt7gt350]

Hella is confident in a VW application in 2008. (http://www.worldcarfans.com/news.cfm/newsid/2050418.005/country/gen/general/hella-led-headlamp-study)

Something else major on the LED front is Cree out-competing Luxeon. Those on the candlepower forums are reporting significant improvements in efficiency. (i.e. twice the light output and twice the battery life for similarly rated lamps)

[dhodory]

[QUOTE=dhodory]

that's true. like all semiconductor products, junction T is very important. However, the usual issue with LED lighting products isn't how much heat they generate but how little heat they do. For example, led-based traffic lights are specifically designed so that the optics wouldn't accumulate snow and if there is accumulated snow, it can be melted by the (little) heat from the leds.


Yes, forward-radiated heat is minimal. The back of the aforementioned traffic light (where the heat sink -- designed or otherwise -- would be) would be warm and quite free of snow.

[icecow]

http://www.stylewillsaveus.com/content.asp?contentid=774

http://www.archpaper.com/feature_articles/05_05_bright_lights.html

http://blog.wired.com/ledarchitecture/

http://www.pulsarlight.com/

http://web.mit.edu/storborg/ddf/video.html

[icecow]

Update:

1000 Lumen LED lightbulb (roughtly same as reg 80 watt lightblub):
http://www.physorg.com/news93198212.html

Screw LCD. 205" LED TV:
http://gizmodo.com/gadgets/home-entertainment/introducing-the-205+inch-technovision-luxio-lcd-hdtv-big-enough-to-park-two-mini-coopers-on-244877.php


commentary: soon, but not soon enough LED chips will miniturize and go cheap, cheap



bonus: (retro) Live video of Tangerine LED zepplin
http://dosetaker.blogspot.com/2007/01/video-led-zeppelin-tangerine-live.html

[Ed Rempalski]

I too have loved leds since they arrived on the scene. I turbocharged a '71 Pinto in '73 while in school and designed an LED speedometer for it. I've put them in everything over the years. I have a few RGB nitelites that do the rainbow thing and agree that it won't be long before we will be able to tune a room to any color.

I have and love my Philips Flat TV with "Ambilight", LED sconce lighting around it's frame that project a halo of light around the TV that matches the predominant color on the screen at rhe moment, very cool.

I'm currently on the quest to lower our power usage as our Kalifornia rates are now triple what they were 5 years ago, even with our consumption being lower. I'm using home control to the max with X-10 and now Insteon on all lights/pumps/HVAC but it's not enough. PhotoVoltiac solar is my next project and possibly these new generation of home LED Lights from this company;

http://www.permlight.com/INDEX.ASP

LEDS are the future.

Oh, and LEDs can flicker like hell, depending on how you drive them. On straight DC no flicker, On 60hz A/C 120V they flicker at 60Hz, just scan your eyes past the new LED christmas tree lights, flicker city. In europe at 50Hz they would be terrible on straight AC!

On the heat, there's no magic, LEDs just put out more light on less watts, but watts are watts. A 10 watt LED would feel like a 10 watt bulb, warm, but the lumens would be equal to a much higher wattage bulb, just like flourescents behave, only better.

[djdementia]

You can already buy very inexpensive LED 'home lighting' for some specialized uses. Here is a link to a LED 'track lighting' type accent bulb for only $5.50:

http://www.geeks.com/details.asp?invtid=WHT-E27-E26&cpc=SCH