Talk:Light-emitting diode/Archive1

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IR laser diodes in remotes

Can anyone provide evidence that infrared laser diodes are used in remote controls? A quick scan of the laser diode article and the remote control article doesn't seem to support this wording. The remote for my VCR, for example, does use an infrared diode, but certainly doesn't use an infrared laser diode to lase and emit an infrared laser beam - that would mean you'd have to point it RIGHT at the remote sensor for the signal to be received.

If someone can justify leaving the "infrared laser diode" entry in the applications section, reply here, but otherwise I'll change it to read "infrared diode" instead.

Abqwildcat 18:18, 28 May 2004 (UTC)

I do not really know, but I also think it unlikely that a laser would be used. I agree that, besides issues of cost, the beam would be too directional. My understanding is that a fairly wide beam is desireable to reduce the need to aim. One system was described to me (long ago) as having two LEDs, both transmitting at once, one very wide angle, so that when the user was close by very accurate aiming would not be necessary, and one with a narrower angle (maybe 10 or 15 degrees) so that the user could aim from a distance.AJim 05:03, 29 May 2004 (UTC)

Actually, the issue of the beam opening depends also on the coupling between the emitting device and the air, so you could potentially have a laser source with a wider spread. But cost is the main factor of choice.[islay16years]

My remote requires me to point it directly at the receiver. Usually I get tired of trying to get it right and shove it up against the TV. It's a really cheap TV. I don't know whether it's laser or anything, it's probably just a cheap-ass TV. But I figured this was relevant. - Vague | Rant 09:48, Dec 14, 2004 (UTC)
It's probably an LED with a very narrow spread -- LED with a clear case (as opposed to the more common milky case) emit a beam of light, which can be adjusted to spread out more or less depending on the shape of the reflector and casing. --Carnildo 05:12, 15 Dec 2004 (UTC)
It is more than likely a bad design (he said it was a cheap TV). It probably uses a typical pulse pattern in it's pulse bursts. Better designs incorporate a digital communication to employ a CODEC (COde -DECode) algorithm and some include bit detection and correction (like a Hamming CODEC). This is the same technique used in many types of communication, including computer interfaces, computer bus', computer networks and telecommunications. A clear case does not determine the angle, it is the lens of the case. The "milky" cases are called diffused lenses. A diffuser spreads light in many directions, but also has much loss do to light being reflected back to the source. A diffused lens will not be used on a remote, these are used for illuminating (including indication). Clear LEDs are used for communication or illumination (book lights, fiber optic holiday decorations, etc...). Danpeddle 17:23, 24 December 2006 (UTC)

Actually, I believe diode lasers generally have a pretty darn awful angle of divergence and without a collimator lens they don't create anything close to a beam. But despite the zoomy name, their output power isn't much different from that of an IR LED (if not inferior). They're easily fried and require a monitoring circuit, and at maybe 100 times the cost I can't think of a single reason why one would use a laser in a remote. Typical IR LEDs are available with 'angles of half intensity' ranging from ±10° to ±60°. Remote LEDs are driven with short but intense bursts of current and the driver circuit may become tricky (read: half a cent more). A narrower beam needs much less power for the same angular intensity than a wide beam that illuminates half the room. Guess which LED type gets chosen. Femto 11:27, 15 Dec 2004 (UTC)

I would like to make a note of the 'angles of half intensity.' As I recall, this is also called the beam spread and is shown in the manufacturer's data sheets as the symbol 1/2 Theta. Theta, as many here know, is use for angles. This is measured relatively from vertically through the die (perpendicular to the dies base) where the light eminates. Danpeddle 17:23, 24 December 2006 (UTC)
Another note is that I recall that LED Lasers emit a rectangular spread, not round. This is caused by the beam being sandwiched to get it to LASE. The collimator, as I recall, is not just to keep the LASER from spreading, but to bring it to a more acceptable rounded point of divergence. The materials to make a LASER diode and a typical diode or infrared diode used to be the same, it was the design of the lenses and die that make the difference, perhaps this is the same today? Danpeddle 17:23, 24 December 2006 (UTC)
The current to drive both the wide angle and narrow angle LED is the same, given the same die. It is the lens of the LED package that determines it's spread. So, for an electrical engineer, the circuit is exactly the same. Hence, power is the same. While the measured light output is the same (there is a standard for this), the more narrow the beam, the great intensity of the beam. So, from a design standpoint, it will allow you to turn on your consumer equipment from across the room. It also reduces the chance your device will interfere with other equipment (poor designs). Danpeddle 17:23, 24 December 2006 (UTC)

I have noticed that if you own a camera with a "nightvision" mode, you are able to see the IR LED transmitting to the receiver. Turn all your lights off, turn nightvision on, and then press some buttons. I have tried this with many remote controls and they all do this. Therefore that leads me to believe that they are in fact regular LED's.

It's not a laser diode. Lots of digital cameras respond to IR. Try camcorders, webcams, etc. You can see the output pattern of the LED this way. - Omegatron 17:59, July 21, 2005 (UTC)
You are more likely seeing the pulse-train bursts, the pulses themselves are typically much to fast for the human eye. It was common in the hobby electronics world to use a camcorder to determine if the remote still worked. Older camcorders have an image intensifier, a mini crt, to amplify light. These are similar in construction to Night Vision Goggles (NVGs) and will amplify the near-infrared spectrum which remotes work in. Danpeddle 17:23, 24 December 2006 (UTC)
Most any black & white camera, too (e.g. older analogue surveilance camera). You don't need to turn off the light, either. [Side note on C player lasers: i've found that most of my remote controls are much brighter than the `dreadfully hazardous' laser of my portable CD player (in spite of the remotes being non-continuous).]
—Brian Patrie 04:19, 26 March 2006 (UTC)
You do not need to turn off the lights to detect the infrared from your remote, the emitted infrared light is very bright to any IR detector/receiver. However, lighting does emit more than visible light, it also emits infrared light too (and ultra-violet for some lighting). This can be a noise distraction to a poorly designed transmitter and or receiver system (the communication and filtering method is what is the problem, so it is the system design). Danpeddle 17:23, 24 December 2006 (UTC)

LED lamp fixtures

What is the proper terminology when referring to a light fixture that uses LED technology, would I call it an LED lamped fixture? reply to klewis@cncarley.com

google finds very few matches for "LED lamp fixture"; a few more for LED "lamp fixture" Waveguy
They are all called luminaires. It doesn't matter if it is LED, HID, Fluorescent or Incandescent. ~DP 12/12/2006 Danpeddle 19:03, 15 December 2006 (UTC)

OLED efficiency

So OLED LEDs are 10% efficient? What does that mean? How efficient are other types and colors? Can someone connect the dots between the percent efficiency and the lumens/watt? Omegatron 21:45, Feb 19, 2004 (UTC)

I think most people, when they talk about efficiency, are concerned with the fraction of the power that is put into the device that becomes useable light. Useable is a bit slippery though, because the eye responds differently than electronic detectors, so you need to specify useable by what or whom. Lumens are used for measuring light intended for the eye. Lumen measurements take into account the variable response of the eye to different colors. Which brings me back to efficiency. Some LED manufacturers employ a bit of specsmanship, and gleefully quote how many lumens per watt their LED's produce. But these, rather enormous numbers, are lumens per watt of emitted power, and are not specific to the LED, but simply reflect the physiology of the eye. A yellow LED rates very high compared to red or blue because the eye is very sensitive to yellow. However, this spec says nothing about how much electrical power must be put in to obtain a watt of emitted light of each color, so it is not really useful, by itself, for comparing lamps. You also need to know the radiant energy (raw photon energy) at the specified operating conditions, then you can weight this by the luminous efficiency for each color to get comparable input versus illumination numbers (if you are concerned about people). If you are very concerned with efficiency, you also need to take into account the losses in the driving circuits, which can be considerable.AJim 05:03, 29 May 2004 (UTC)
If you measure efficiency of a light source, you do not measure the driving device into it's equation. If you are a system designer working for an architect, you measure the driver with the light. Efficiency is the difference between what goes in and what is supposed to come out. Danpeddle 17:37, 24 December 2006 (UTC)
There exists a standard device to measure light in lumens per watt. The device is a circular chamber and can measure the light spectrum, visible and non-visible. It reflects light and focuses it to a point within the chamber to where a sensor exists. The meausring device does get calibrated by a certified metrology outfit. When refering to the lighting industry, it is the visible light that is typically measured. More than likely, for LEDs, this will change because of accent lighting and mood lighting that imploy RGB. Danpeddle 17:37, 24 December 2006 (UTC)

I cleaned up the section on OLEDs, which was unclear. I had to infer some of the information -- I'm not a domain expert. Care to verify I haven't introduced inaccuracies? --Anonymous

I can't believe that NOONE talk about Luxeon yet :o

No one talk about Luxeon yet. :o). D@mn, I wish I have enough technical English to write an article about it.

Helloooooooooooo, any flashaholics/CPFer here?

There is a description of 1W and 5W LEDs near the end of LED technology section. It does not mention Luxeon by name; there are other manufacturers of high-power LEDs.

no one talks lysdexia 10:57, 21 Oct 2004 (UTC)

Units

From the SI article:

  • Symbols are written in singular, e.g. 25 kg (not "25 kgs").

Similarly it is 'candela' not 'candelas', 'metre' not 'metres' or 'meters'. 213.51.209.230 11:29, 9 Oct 2004 (UTC)

Ooops. Confusion arising, very simple. Technically 60 W, or 60 Watt lamp. No problem. In common language (anywhere) one has: "I was 3 meters away from him, and I could not hit him with a 2 meter (2 m) rod". End of story.

Clearly, in common usage (at least here in the US) the more common SI units are suffixed with a plural "s" nearly always. Professors, students, professionals, etc. would all agree that common usage is "5 meters" not "5 meter". Using the second can actually cause confusion as there are multiple definitions of the word "meter" (argue spelling, if you like, but when spoken metre = meter). I think for the purposes of clarity, when the unit suggests a natural pluralization (i.e. if "meter" singular sounds wrong compared to "meters") we should err on the side of clarity rather than grammar. Also, the article only seems to mention that symbols are always singular. I would not argue with that; if abbreviated, I have never seen 5 m's or anything of the sort. 5m would be the standard, as the article describes. --ABQCat 18:20, 9 Oct 2004 (UTC)
Whichever source says that written out units aren't pluralised is wrong. It's wrong because it's dumb.. and wrong. They're singular though, and hyphenated, in the adjectival form: 45-metre. lysdexia 10:57, 21 Oct 2004 (UTC)
Unit symbols (such as "kg") should not have the "s" for plurals but unit names (e.g., "kilogram") should. Annex 5 to the Convention on International Civil Aviation, Units of Measurement to be Used in Air and Ground Operations (which is heavily SI orientated), Attachment B says, in part:
5.1 Rules for writing unit symbols
5.1.2 Unit symbols are unaltered in the plural.
5.2 Rules for writing unit names
5.2.2 Plurals are used when required by the rules of grammar and are normally formed regularly, for example, henries for the plural of henry....
So it should be "600 cd" or "600 candelas". This is correct.
EdDavies 17:42, 2 December 2005 (UTC)

Bizarre and inappropriate color related paragraph

I removed a dispute tag (no actual dispute ever existed so far as I can see) and the following paragraph:

"The above list is taken from public sources, but at least one LED given as blue does not produce blue light. (There is a good chance that almost none do, because of the higher frequency of blue.) This is a common problem in daily life due to the majority of mankind being ignorant of colour theory and conflating blue with light blue with cyan, the latter often called "sky blue". A cyan LED may be distinguished from a blue LED in that adding a yellow phosphor to the output makes green, rather than white light. And often aqua is called blue-green when in actuality the latter is cyan, and light cyan-green would be aqua. What adds to the confusion is that cyan LEDs are enclosed in blue plastic. A great amount of work is needed to dispel these intuitive myths of colour mixing before accurate descriptions of physical phenomena and their production can happen."

An article on LEDs is definitely NOT the place to post this sort of pedantic (and factually highly suspect) rant. Furthermore the definition of blue is readily recognized in the general public and the above paragraph merely serves to convolute the issue.--Deglr6328 04:13, 13 Nov 2004 (UTC)

It is true that some LEDs marketed as "blue" wouldn't make a lousy excuse for that name, even to the general public (show them a LED and a color chart, and they'll point at 'cyan'). I for one am inclined to share the rant about the everyday language mixup between cyan and blue (just not here or in the form of the justifiably removed paragraph). It would very well make sense to address the issue in an article about a product that is otherwise distinguished between red, super-red, hyper-red, orange, amber, ultra-yellow, green, true-green, etc. Femto 18:45, 15 Nov 2004 (UTC)

Largest display questioned

The page lists the one in times square at 118 feet. However the one on the Fremont Street Experience is over 1,500 feet long so it would seem that one is larger. For details on the display look at [1] for the size information look at [2]

Could we picture the NASDAQ LED display in Times Square too? It may not be the largest, but it's probably one of the most famous. [3] Gordeonbleu 21:25, 3 October 2006 (UTC)

Light output characteristics?

Anyone care to address the differences in the light output profiles? Some types of lighting are better for human eyes than others...
~ender 2005-04-16 11:00:MST

Diffuse light is always the best for all animals, even plants, because of the envinronment where they have developed for millions of years. Collimated light is an artifice created by humans to save energy. This is why Leds are best for displays, and lasers for transmission. Of course, applications are many and every case requires analysis, but this is a general feature of the distinct light sources.

disambiguate through-hole LED and LED chip?

It seems that this article is mostly about through-hole LEDs. I think this should be altered so that this page is more about the LED chips and their technology generally, with more specific articles to talk about the various modes of packaging: T1, T1-3/4, the Luxeon technology, various surface mount packages, the large arrays produced by Lamina Ceramics, etc.

Is there any significant difference between through-hole and surface-mount LEDs, other than the packaging? --Carnildo 20:47, 22 May 2005 (UTC)
Yes! Some SMD LEDs, luxeon in particular, are mounted to and aluminum substrate PCB to remove the heat from the die. And, yes, LEDs get extremely hot. Also, I would like to point out, if it hasn't already been pointed, is that the T1 and T1-3/4 reference is based on the diameter. A T1 diameter is 1/8 of an inch. A T8 is 8/8 of an inch (see Fluorescent). More information for lighting, including LED and color mixing, can be found in The Illuminating Engineering Society of North America (IESNA) book. ~DP 12/12/2006 Danpeddle 04:06, 15 December 2006 (UTC)
Extremely hot? LEDs are more efficient than incandescent lamps because they don't produce a lot of heat. Try touching an LED even after it has been on for a while. Feel any heat?

Thanks, Jonabofftalk

20:10, 16 January 2007 (UTC)
Then I would like to see how long you can hold a Luxeon type LED! I have plenty here at work. The ones that you probably refer to are the little ones that cannot be used for room lighting, but more for novelty items. Ours are used for room lighting, accent lighting, landscape lighting, etc... These are about as efficient as a CFL (Compact Fluorecent Lamp). Maybe you would like to hold a lit CFL in your hands too? Hmmm... thank god for "Free Enrgy," right??? The LEDs used for lighting are expressed in lumens per watt for a reason, they give off heat! Danpeddle 03:30, 24 January 2007 (UTC)

diagram

we need a close-up diagram that shows the internal structure, like [4], [5], [6], [7] but better. Like the first one but more close-up would be ideal in my mind. - Omegatron 15:05, Jun 8, 2005 (UTC)

I would like to point out that the flat or short lead of an LED does not always mean that it is the cathode. A flat or short lead can also represent the anode. SMD LEDs have other methods that you need to be careful with. The best thing to do is to read the manufacturer data sheets. For some proof, see my links under "potentiometer." Danpeddle 04:05, 15 December 2006 (UTC)
I would also like to know why LED matrix and digit displays are not covered? Doesn't anyone here work in the electronic field? Danpeddle 04:05, 15 December 2006 (UTC)

Life span

What is the life span of an LED light? Is it true that they last "forever", or are the people who market this saying that if not used continuously, they seem to last forever?

Also, what is the maximum and minimum size of an individual LED?

I didn't seem to find answers to these questions in the article -- they should be included.

LED lifespans are usually best measured in terms of half life: the time it takes for the LED to fade to half its original brightness. Half-lives for LEDs are usually quoted in the range of 10,000 to 100,000 hours, but I don't know if these are the real numbers, or just something marketing came up with. For most purposes, an LED used as an indicator light can be considered as lasting forever. LEDs used for illumination will need to be replaced eventually. --Carnildo 01:13, 29 July 2005 (UTC)
Life spans are calculated and emperically and statistically tested. They change in both intensity and color. OLEDs are worse and have a very short life span in comparison. LEDs used for lighting, even signage, are "Binned" for color and intensity. This is one of several reasons they cost much more. To understand, imagine these enormous displays with hundreds of luxeon LEDs. Imagine the blues, greens and reds all being shades different. Sort of splotchy apparence! So, they "Bin" them so all the blues are about the same wavelength and intensity, same for greens and same for reds. Danpeddle 04:06, 15 December 2006 (UTC)

New White-Light LED Discovery

[8] This accidental discovery may replace light bulbs. Simesa 18:43, 22 October 2005 (UTC)

The link doesn't work I'm afraid - do you wish to clarify?
Here's one link Google turned up, but it's impossible to tell if this was what Simesa was referring to. This link discusses Nichia achieving increased efficiency through roughening the surface of the LED, promising efficiencies well in excess of what we can achieve today with fluorescent lamps.
http://www.theinquirer.net/?article=29472
Atlant 13:32, 3 February 2006 (UTC)

Organization

This article needs to be reorganized. It just doesn't make much sense, it doesn't have a logical flow. Also, it should have some statistics, like how long they last, what their efficiency is, how bright they generally are and how bright the brightest are. And you shouldn't have to sift through the whole article to find the information (like you currently do with the efficiency). Twilight Realm 02:23, 3 November 2005 (UTC)

Another White Light LED discovery, split them out.

The Inquirer reports another approach to generating white light: purple LED with a silicon carbide substrate, developed by Professor Satoshi Kamiyama of the Meijo University and producing 130 lm/W

I think the White LED section should be separated from any blue LED section, as many of the alternative approaches don't use blue LED's.

Skierpage 05:22, 17 November 2005 (UTC)

Hmmm, the inquirer isn't exactly, ohhhh what's the word I looking for here....uhhmmm....ahhhh..reputable. Yeah that's the one. --Deglr6328 06:56, 17 November 2005 (UTC)
The Inquirer is not to be confused with The National Enquirer. They are utterly unrelated.
—Brian Patrie 04:50, 26 March 2006 (UTC)
Purple LEDs themselves are based of blue LEDs. Andros 1337 23:41, 15 January 2006 (UTC)

"Analogues" should explain topic

I've reverted out the butterfly wing "analogue" since I doubt it would be useful to a reader trying to learn about LEDs. Just because Wikipedia is much less limited in space than a paper encyclopedia doesn't relieve us of the necessity to be on-topic and concise - we can't drag in every peripheral reference or notion. --Wtshymanski 14:36, 18 November 2005 (UTC)


Colour for night vision

The article says ...and situations where dark adaptation (night vision) must be preserved, such as cockpit and bridge illumination, observatories, etc. Yellow LED lights are a good choice to meet these special requirements because the human eye is more sensitive to yellow light.... Usually red light is used in these circumstances, not because the eye is more sensitive but because the eye's night-vision mechanism is less sensitive at these wavelengths so not harmed by the light. EdDavies 18:03, 2 December 2005 (UTC)

I do not believe he is talking about the sensitivity of the human eye. Cockpit instruments can also be green or blue (I was in Army aviation). The reason for the colors other than red is because red iterferes with the Night Vision Goggles (NVGs - I worked on these in the military too). The NVGs are a starlight device that amplify small amounts of light to make objects more visible to the human eye. These NVGs work very well in the near-infrared spectrum and red spectrum. The PVS-5s (infantry goggles) are equipped with an infrared LED and a toggle switch (possibly different today) to illuminate in very dark regions and to provide a very bright beam of light for a long distance. All the NVGs are sensitive, including the AVS-6s the pilots use. Note: It is possible the numbers PVS-5 and AVS-6 could have and probably have changed in todays military as they are equipped with new generations. I ended my military career in January of 1992. Danpeddle 15:59, 24 December 2006 (UTC)
There's always some confusion in the use of colour and night vision. Red illumination does not have as great an effect on dark adaptation as does other colours. However, if you want to see something with the least light output, the scotopic and photopic peak sensitivities are in the yellow-green colour (550 nm IIRC for one but the two sensitivities are slightly different). Red light illumination of instruments is problematic for older individuals due to a condition that is very common - the name of which I can never remember and can't ever find online. I believe that the end result is choose red for general illumination and yellow-green for detail. A past acquaintance and professor of optometry always cursed his Audi for its red-illuminated dashboard - as drivers reach an age when they are inclined to buy such a car, they do not benefit from the red-illuminated dash... but then no one does, since you can't dark adapt while driving a car. Michael Daly 23:35, 12 July 2007 (UTC)

Current source for LEDs

Image:constant_current.jpg

Luxeon LEDs

Any of you guys seen the new LUXEON LED flashlights yet ? I have two of these, both sold in the SEARS franchise, both are CRAFTSMAN. These are WHITE LEDS w/ NO other color in them at all. Other companies make these lights as well. Martial Law 07:27, 7 March 2006 (UTC) :)

I reverted this, and Martial Law asked me if it could be restored. Even if probably not intended as an advert, it comes as close as you can get. Links to retailers are generally to be avoided if there's any alternative (such as may be the http://www.luxeon.com/ website). These LEDs are notable and should be mentioned, focusing on the technology itself, how they work, what they're made of, their differences to the Nichia type, etc. This article isn't the place to mention specific product applications though.
Luxeon redirects here, which I think it should not. Maybe we could expand that to a proper company profile article that may mention their products, and only link to that from here. Not me, any takers? Third opinions? Femto 12:22, 21 April 2006 (UTC)
Now that we have a proper website/source, can the LUXEON LEDs be mentioned here in the article ? Martial Law 23:47, 21 April 2006 (UTC) :)
I have corrected a sock-bug. This thing has been reported. Why is this bug not fixed ? Martial Law 23:47, 21 April 2006 (UTC) :)
You get logged out when your browser clears cookies, or sometimes the servers just forget our login information. Then you edit from the default anonymous account of your IP address. Make sure your login name appears at the top of the page.
Sure, make it similar in style to the existing content on the Nichia type, that is, explain the technology, not the products, and all is fine. Femto 11:46, 22 April 2006 (UTC)
I'm quite surprised there is no mention of the Luxeon LED's at all in this document, they are substantially brighter than ordinary LED's and are revolutionising the modern flashlight. They are now available in a 5 watt class that offers 120 lumens of output and there is a Lenser Police Tech flashlight with a 1.25W (60 lumens) LED that has a unique focusing design that copes with the unusual angles of light output from the LED due to its physical characteristics. Maglite are offering them as replacements for the traditional xenon bulbs and have a comparison chart of discharge times on their web site. I would be especially interested in the physics that makes these LED's so much more powerful if anyone can explain it. Mrheritage 07:26, 17 October 2007 (UTC)

LED's: Too big for computer displays?

It seems LED's would be ideal for computer displays. Energy consumption would depend only on the average brightness of each pixel being displayed and black would be pure black, unlike today's LCD's. Also response time would be orders om magnitude better than LCD's. I see that there are plenty of large LED displays, but not small ones, so I assume they cannot be minaturized enough to be made into a high resolution device like a PC display. TimL 21:06, 19 March 2006 (UTC)

LEDs are in current use, at least for small displays (as in cell phones and the like). These tend to be Organic light-emitting diode rather than inorganic diodes.
Atlant 23:09, 19 March 2006 (UTC)
OLEDs are not used in devices such as computer monitors as they have very short useful lives (with blue OLEDs having a half-life of only 5000 hours) -- I would add this to the article if I could cite it, but can't remember where I read it. Actually, it might have been on Wikipedia *goes to look*

Thanks, Jonabofftalk

20:20, 16 January 2007 (UTC)
Oops! Sony invent an OLED TV that is a mere 3mm thick with 30,0000 hours viewing; [9] the article also cites "Other firms are also working on OLED screens - Samsung has shown off a 40-inch TV using the technology..."Mrheritage 07:27, 17 October 2007 (UTC)
The sony panel may be close to production but it is both tiny and expensive, to me that just screams that they are having big yeild problems. The samsung panel is unintersting unless there is proof that it is more than a short lived concept. Plugwash 10:18, 17 October 2007 (UTC)

LED applications as warning lights on vehicles

While the applications section talks about LEDs in traffic signals, it doesn't talk about their application in cars. Cars with LED stop lights and indicators are now common and their advantages, particularly quick illumination, are well advertised. Could somebody add this in?

Some manufacturers have also shown LED headlights at various automotive shows, I believe. Bicycle lights are also commonly LED.

http://www.electronicsweekly.com/Article4455.htm

(84.98.245.104)

mmm horrible things those LED indicators. Have thier been any studies that show that a faster rise time on the lights is actually a good thing? surely you wan't an indicator to be just attention grabbing enough that you notice it at first not something that its virtually impossible to take your eyes off? Plugwash 20:57, 4 April 2006 (UTC)
Yes, studies do show that faster rise and fall times are better. They can provide many milliseconds of breaking before an incandescent is visible (it needs to heat up). We used to design these, but we offloaded this to our European counterparts. If properly designed, they do not flicker like some of the cheap ones. They also have to have a certain PWM rate for tail lighting. The headlamps are comming in the future, currently they need to make LEDs more efficient. Also, LED are being used in freezers, they are much better, reliable and more efficient in the cold than a fluorescent lamp. ~DP 12/12/2006 —The preceding unsigned comment was added by Danpeddle (talk • contribs) 03:39, 13 December 2006 (UTC).
LEDs are also now used in light bars on emergency and utility vehicles for the higher conspicuousness because of the quick illumination and the fast that they can be quickly and repeatedly flashed, and because LED light bars can have a much shallower form factor, reducing drag.

Thanks, Jonabofftalk

20:28, 16 January 2007 (UTC)
Also, I notice that Danpeddle has added a lot of posts regarding the heat produced by LEDs, their inefficiency and their need to be made more efficient (here). I was under the impression that they are (much) more efficient than conventional lamps and that the current limitation is that they are not available above ~5 watts power. If he wishes to dispute this, I would be grateful if he would post to my talk page.

Thanks, Jonabofftalk

20:28, 16 January 2007 (UTC)

OK, for you experts that believe LEDs do not give off heat, please check out the DOE website on SSL (Solid State Lighting). http://www.netl.doe.gov/ssl/ and this article dated December 2006 http://www.netl.doe.gov/ssl/PDFs/CPTP%20Pilot%20Testing%20Results%20Summary--draft-12-06-06.pdf Danpeddle 00:49, 21 February 2007 (UTC)

interwiki: vi:

The Vietnamese link is Luxeon, which although relevant, is not exactly a synonym of LED. Somebody should correct it. Wek1 19:47, 8 April 2006 (UTC)

messed up edit

I removed the branchlist template. I did not see how most of the links in there had anything to do with LED's. Wouldn't be so bad if it wasn't right there at the top. I messed up the edit comment, so this is it. TimL 20:27, 10 April 2006 (UTC)

Tim, You and other editors may have an interest in the proposal to delete that template. -- The Photon 05:26, 11 April 2006 (UTC)

Mess

I may have made a unintentional mess w/ the Luxeon reference. Can someone straighten this out ? Martial Law 21:51, 22 April 2006 (UTC) :)

No problem, I removed it. TimL 00:40, 23 April 2006 (UTC)

P.S. Just about any light will blind you if you stare directly into them long enough. TimL 00:42, 23 April 2006 (UTC)

I would have added a simple reference to Luxeon, probably in the Blue and white LEDs section. No idea though where between the europium, Ce3+:YAG, and homoepitaxial zinc selenide this technology should go. Unless this type of technical detail is included, any mention of these products will remain little more than an unencyclopedic advertisement I'm afraid. Femto 12:40, 23 April 2006 (UTC)

Blue led mankind to doom

It should merit a mention that blue LEDs are no longer "fashionable", but rather categorized as one of the more serious crimes against humanity. Chinese manufacturers have a fancy to put blue leds on any possible device in any possible position and their brightness is so high it drives people mad. Here in Hungary there is actually a movement for the ban and destruction of blue LEDs. Blue leds are probably the most evil use of quantum mechanics ever known to man and certainly a crux of bad taste.

quote: "This blue LED madness has to stop. Altec Lansing, with their FX6021 Speaker System is only one of the manufacturers guilty of falling victim to this abominable trend, but the degree to which they’ve fallen for it is worse than most. The control pod’s power LED alone lights up a room at night, and with one or two volume LEDs illuminated, the overall brightness becomes uncomfortable. If you’re sending a very low-level audio signal into the system and have to keep it turned up to maximum volume, you’ll have six of these brilliant LEDs turning your ceiling into Rave Central, making it difficult to sleep if you’re facing the system."

Write to the manufacturers and tell them to use bigger resistors. — Omegatron 23:36, 24 May 2006 (UTC)
Or get out your soldering iron and its finest tip...
Atlant 23:54, 24 May 2006 (UTC)
hehe made me lol--Deglr6328 06:49, 25 May 2006 (UTC)
Snort. Blue LEDs are dead and rotting. The really cool people know that they've already been superseded by flashing purple ones. Femto 11:51, 25 May 2006 (UTC)

Questionable explanation of touch-sensing

The second paragraph in Multi-Touch Sensing is questionable. My understanding of it is as follows: LEDs emit light on fingers or stylus; then LEDs are switched off and receive THE SAME light reflected from fingers or stylus. It is impossible (or at least impractical) to build such a system, because light will travel to the fingers and back in a fraction of nanosecond while indicator LEDs used in matricies are not that fast (not to mention wiring delays and microprocessor timing).

I didn't find any info supporting abovementioned explanaition neither in the paper by Dietz, Yerazunis nor on the Jeff Han's page.

I think LED matricies are used as touch-sensitive devices a little different way, for example even and odd matrix rows can be switched on and off in turns, and the light from even rows, reflected from user's fingers, is detected by odd rows and vice versa. --Ilkuch 08:02, 30 June 2006 (UTC)

Your explanation certainly sounds better; I've edited the article to reflect (oops!) that. CHeck it out and see if you agree with the new wording, and feel free to be bold and improve it further!
Atlant 10:47, 30 June 2006 (UTC)
Couldn't the LED be used as both an emitter and a sensor at the same time, by the principle of superposition? Seems like photons reflected back into the PN junction would cause the same effect as ones that hit it from other sources. Is the change caused by reflected light too small to measure? — Omegatron 21:34, 25 October 2006 (UTC)
Is the change caused by reflected light too small to measure?
I'd guess that's right, but it's just a guess. I think the "separate emitters/detectors" scheme would probably work with ordinary digital electronics whereas the "superposition" scheme would probably require classy (read "expensive") analog electronics. But that's all just a guess on my part.
Atlant 00:05, 26 October 2006 (UTC)
"Couldn't the LED be used as both an emitter and a sensor at the same time, by the principle of superposition?"
Superposition only works when dealing with linear devices, diodes are about as nonlinear as you can get in electronics. To get light out you put a diode in forward bias and send a flood of current through, to detect light you have to put it in reverse bias and measure the leakage. Plugwash 10:39, 17 October 2007 (UTC)

Where to Buy?

Does anyone know of a major corporation that sells LED lights? I know you can buy them off the internet [10] but I would prefer to buy them in a store. Like does Walmart or some of place like that sell a bag of 100 of them? Thanks. sharpdust 18:05, 21 July 2006 (UTC) (a beginner to LED lights)

No. Radio Shack doesn't even sell them anymore. The Internet's all we have left. — Omegatron 18:20, 21 July 2006 (UTC)
Hmm, Radio Shack stores in Canada changed names a year or so ago but the last time I looked they still sell blister packs of LEDs. If you want scores of any given model,depending on where you are there are electronics wholesalers. In California you've got Frys, for instance. DigiKey isn't too scary to deal with, and they're really quick for me because their Canadian warehouse is in my city. --Wtshymanski 22:16, 21 July 2006 (UTC)
American Radio Shacks removed their parts drawers in the last few months. No LEDs. :'( Digikey is probably your best bet. — Omegatron 14:13, 22 July 2006 (UTC)
What??!! I just went to Radioshack last week!? The drawers are definitely still there. LEDS FOR ALL! YAY!!!!!! Anyway, no need to wait for a website to deliver one, just walk down to your nearest Radioshack to get some. Ilikefood 00:35, 29 October 2006 (UTC)
Thank you for the reponses, reluctantly I will try the Internet. I would think that most suppliers would carry LEDs with the popularity of Throwies. sharpdust 16:39, 22 July 2006 (UTC)
If you want a lot of LEDs, go for ebay. You can always find cheap stuff on there because no one's really looking for electronics components. Here's 38 bags for $15, for instance. — Omegatron 17:15, 22 July 2006 (UTC)
Right now, you can get them at your local Wal*Mart SUPERCENTER, Sam's Club, Radio Shack. @ Wal*Mart, find them in the Camping/Sporting Goods section, they now sell the "Everlife" flashlight which is a light that does'nt use batteries. The demand is up for these things, due to natural disasters, camping, emergency preparedness protocol, terrorisim threats, use in prospecting,etc. Martial Law 05:33, 5 August 2006 (UTC)

bicolor/tricolor

Should Bicolor and/or tricolor leds have their own separate page(s)? There is only a small mention of them on the led page. Pi.1415926535 17:06, 27 August 2006

In (just) my opinion, no. Atlant 02:45, 28 August 2006 (UTC)
No. They belong here. — Omegatron 03:07, 28 August 2006 (UTC)
no. --Deglr6328 05:11, 28 August 2006 (UTC)
Don't forget RGB. And... It is possible some future LEDs will have 4 colors and others with 5 colors to properly represent a color spectrum. They are also looking into incorporating some sort of feedback for intensity, color or both. (read about RGB and LED at univeristies) Many simple (T1-3/4 four leaded devices) RGB LEDs incorporate RGGB or RGBB dies, probably some I may not even had mentioned. ~DP 12/12/2006 Danpeddle 04:09, 15 December 2006 (UTC)
Why are >3 colour LEDs needed, when the full spectrum can be represented using RGB? Or did I misunderestimate you when really you meant doubling up of colours? Again, could Danpeddle contact me at my talk page? No worries if not... (en-GB ftw!)

Thanks, Jonabofftalk

20:37, 16 January 2007 (UTC)
Sorry Jonaboff, I'm still new to this and I have not taken the time to learn wikiworld processes. I'll be more than happy to discuss in further detail, just need your directions to get there. As for the four and five color, you heard me right. I'll explain later in your talk. Danpeddle 03:50, 24 January 2007 (UTC)
No, they're the same technology, just different packaging.

Thanks, Jonabofftalk

20:37, 16 January 2007 (UTC)

PlanetAnalog.com article

Did anyone else notice the article in the PlanetAnalog insert in EETimes magazine on Aug 28, 2006, by Karl Schlossstein? The title was "LED's diverse advances lead to numerous possibilities". Unfortunately I can't find an online version of the article --- I only have the paper version.

At least three sentences seem to be "borrowed" from this article.

Schlossstein Wikipedia
"Gallium nitride (GaN) and indium gallium nitride (InGaN) blue LEDs enabled white LEDs by adding a combination of red and green LEDs or by covering the blue LED with a yellowish Ce3+:YAG (cerium-doped yttrium aluminum garnet) phosphor, the most common technique today." "Most 'white' LEDs in production today use a ... GaN (gallium nitride) or InGaN (indium gallium nitride) LED covered by a yellowish phosphor coating usually made of cerium-doped yttrium aluminum garnet (Ce3+:YAG) crystals..."
"New methods of creating white light from LEDs use no phosphors... One method uses a homoepitaxially grown zinc selenide (ZnSe) on a zinc selenides substrate to produce a blue light from the active region and a yellow light from the substrate at the same time." "The newest method used to produce white light LEDs uses no phosphors at all and is based on homoepitaxially grown zinc selenide (ZnSe) on a ZnSe substrate which simultaneously emits blue light from its active region and yellow light from the substrate."
"Michael Bowers, a grad student at Vanderbilt University...found that blue light caused his quantum dots to emit a white light simlar to an incandescent bulb." "A new technique just developed by Michael Bowers, a graduate student at Vanderbilt University in Nashville, involves coating a blue LED with quantum dots that glow white in response to the blue light from the LED. This technique produces a warm, yellowish-white light similar to that produced by incandescent bulbs."

Schlossstein has done some notable copyediting, improving the flow of these sentences, and adapted them to the rest of his article. He's also located sources for some statements that are presented in Wikipedia with no citation. But it looks to me as if his article skates close to the edge of plagiarizing Wikipedia, and he gives no credit to this site. If you agree with this judgement, consider letting the editors of PlanetAnalog and EE Times, and Schlossstein's employers (he's an applications engineer at National Semi) know what you think.

-- The Photon 03:54, 4 September 2006 (UTC)

haha! wow that's pretty funny. kinda reassuring in a way though, I mean, at least it let's me know that those bits I did were apparently accurate enough to be quoted practically verbatim in EE times! cool! (/scary?) --Deglr6328 05:02, 4 September 2006 (UTC)

leds explode

an Led can explode if there is no resistor on it.

this is true. why not add it. though its more of a *pop* than a BOOM.--Deglr6328 21:57, 5 September 2006 (UTC)
:NOT TRUE.. I have had plenty of LEDS burn out on me and the worst that happened was when one heated up hot enough to melt plastic and then the inside started turning brown and it melted the plastic down and it dripped down one of the leads about a milimeter. Ilikefood 00:38, 29 October 2006 (UTC)

i added the LED explode

i added a little information to disadvantages of leds. i said they explode without a resistor —The preceding unsigned comment was added by Atlfalcons866 (talk • contribs) .

"Explode" is a little dramatic; I've never heard of it happening. The wire-bond to the LED die will probably melt long before anything as exciting asan explosion occurs.
Atlant 23:27, 9 September 2006 (UTC)
It will only happen if you connect them to a hugely inappropriate power supply. eg. if you connect the tiny ones to the 12v supply from a wall plug transformer they will often pop from the internal pressure created by the burning plastic. there's no way its EVER going to happen during any normal use.--Deglr6328 23:35, 9 September 2006 (UTC)
LEDs will "EXPLODE" when the current through the device is not limited. A 12V supply is OK to use as long as the current limiting resistor is sized appropriately. A prefered method is to use a constant current (CC) supply rated at the proper LED current. The Luxeon LEDs typically use a CC supply and are called LED Drivers. If the current is not limited, then the energy will cause the device to rapidly heat up. This heating is between dissimilar materials with different coefficients of thermal expansion and the acceleration of expansion of one material over the other will cause the component to "explode." This is no different than any electronic component, be it LED, IC, capacitor, resistor, etc... So, if you include "explode" with LEDs, then it should be included with all electronic components. You should never connect an LED directly to a constant voltage (CV) supply (including batteries) unless the impedance is such that it is self limiting with the LED across it. Otherwise you will damage the LED ("explode" it possibly). Cheap LED Keychains are a prime example, they use the internal resistance of the battery to limit the current. Do not connect too many in parallel, including Luxeon types, to a battery. The battery will oxide faster, it's internal resistance will increase and, as it increases, it gets hot. This cycle will continue until the battery is no longer useable or it explodes from the heat. ~DP 12/14/2006 Danpeddle 03:40, 15 December 2006 (UTC)


LEDs exploding is a known problem with IR LED therapy. A safety screen must be used. Tabby (talk) 06:08, 24 January 2008 (UTC)

Sort List of Applications?

Should we sort the list of applications somehow. I just added one and I had no clue where to put it in the existing list. ForestJay 17:29, 13 September 2006 (UTC)

Some of them can flash, huzzah.

I really don't understand what is thought to be so special about LEDs with a chip in them that makes them periodically flash. Honestly, why is this news. you can make almost any other electronic light source do the same thing by adding flashing circutry. big deal. It tells the reader nothing fundamental about how an LED actually operates and produces light and does not belong in the physical function section. Can't we at least move it to the LED advantages section?--Deglr6328 19:04, 21 September 2006 (UTC)

How do they flash without circuitry outside of them? Is there an IC built into the leads inside the plastic shell? Ilikefood 00:39, 29 October 2006 (UTC)
Yes. LEDs can be had with several different extra internal components:
  • Simple resistors
  • Current-regulating ICs
  • Flasher ICs
Usually, the extra bit is mounted on one leg, the LED chip on the other, and a bond wire connects the two.
Atlant 00:57, 29 October 2006 (UTC)

cost over life expectancy

The higher efficiency and life expectancy of LEDs in comparison to the common light bulb or possibly even the neon tube should result in lower cost over their life span. To look at cost in lumens per dollar tells about upfront cost but not overall cost.

I could calculate that properly but I would need more appropriate data. Can anybody help with that? Walter Hartmann 23:18, 13 October 2006 (UTC)

I heard LEDs had similar efficiency to incandescents. — Omegatron 01:34, 29 October 2006 (UTC)
A reference would be good. Hit the books,people! "Efficiency" is too general to be a useful term - "efficiency" of what? We shouldn't be making calculations on the Wikipedia for fear the WP:NOR people will be after us. --Wtshymanski 18:50, 30 October 2006 (UTC)
Calculations are ok sometimes. The important part is that the info on the page is verifiable. If the reader can verify it by looking at the page itself, it's fine. If it weren't for calculations, we'd need to have references for every mathematical proof. — Omegatron 00:58, 1 November 2006 (UTC)
LEDs are more efficient than incandescents and some are now near as, if not more, efficient as compact fluorescent lamps. The lighting industry is currently reviewing the cost of fluorescent versus LED. While LED cost more upfront, they last much longer and have less field/warranty returns. It may be more fiscally beneficial to all parties (lighting electronics Mfrs, luminaire Mfrs and facility owners) now to push LED technology in certain areas of fluorescnet and [definitely] incandescent. Efficiency is really an ambiguos term, since it could include the ballast or driver device, such as a light engine (combined lighting electronics with LEDs on a PCB). The lighting handbook put out by the IESNA explains how to properly test lamp devices, including LEDs, without the lighting electronics. Yes, we have standards in the lighting world! Some people point out a light bulb has the benefit of lighting all around, while the LED has a half angle (1/2 Theta) that limits it. But, look up at your ceiling and tell me why you need 360 degree lighting coverage? (much waste here) Especially in downlight (ceiling can) applications. Danpeddle 04:10, 15 December 2006 (UTC)

Huh?

What is that LED with three leads in the picture that has a whole bunch of LEDs? Why does it have three? Is it one of those bicolor ones or something? Someone should put that in the picture description. Thanks. Ilikefood 20:41, 20 October 2006 (UTC)

Yes, bicolor with either the cathodes or anodes in common. (The other kind of bicolor LED puts the two diodes in inverse parallel and depends on the polarity of the applied voltage to select the color.) Please feel free to be bold and edit the article appropriately!
Atlant 00:08, 26 October 2006 (UTC)
I once tried making an inverse parallel 2-colour display using a red and a green LED. I applied p.d. and both LEDs lit. Can anyone explain this? (the LEDs were opposite polarity...)

Thanks, Jonabofftalk

20:44, 16 January 2007 (UTC)

Not making sense

one part says that LEDs are more cost-efficiant than regular lights, while another part says that they're less efficient. Which one is correct? Ilikefood 22:12, 30 October 2006 (UTC)

Today's LEDs are more electrically efficient than incandescent. When I say "Today's" LEDs, I am refering to the higher brightness ones that have become so mainstream, not the old panel indicator types. Small incandescent lamps used in automotive (including instrument clusters), holiday lighting, night lights, candela lights, etc... are horribly inefficient and are much better heaters. An LED lamp fixture is more cost effective in certain areas and should be costed beforehand, since the techonolgy is still much more expensive than incandescent (same holds true for those fluorescent lamps used to replace incandescent). An incandescent lamp is a better heater than it is a light source. Please note, LEDs used for lighting (the luxeon types) DO get hot and are designed to be mounted to a heatsink. You can also purchase these already mounted to an aluminum substrate PCB, but that still requires further heatsinking, depending upon application. ~DP 12/12/2006 Danpeddle 04:11, 15 December 2006 (UTC)

LED History

LED history goes back a long time. Next year, 2007, it will be 100 years old. However, I am not a historian and leave to this group to debate. I do think history and dates are important for any reference document. Here is a link from the Cambridge University Press http://www.deastore.com/pdf/cambridge_03302006_093610/0521823307_excerpt.pdf I've also read about this in other electronic magazines or journals, which is why I looked for a document online. Danpeddle 03:50, 15 December 2006 (UTC)

In 1962, Nick Holonyak Jr. of General Electric did not invent the first practical visible LED. He was the first to construct a visible-spectrum semiconductor laser. For this work he is considered the inventor of the first practical LED, the red GaAs1-xPx LED. Ref; http://www.micro.uiuc.edu/ssdl/ Danpeddle 20:11, 23 December 2006 (UTC)

Just because electroluminescence was discovered in 1907 doesn't mean that the led was too. That would be like saying Stokes invented the fluorescent lightbulb in the mid-ninteenth century when he observed the visible light glow of fluorspar under UV irradiation.--Deglr6328 21:29, 23 December 2006 (UTC)
The 1907 discovery was a Schottky diode that emitted light. The discovery was used in future experiments which directly led to the invention of the more modern LED. It has been attributed as the first LED as much as the discovery of ELD. What you are saying then, is we should not include this detail in modern ELDs either. If I had made the argument that the inventor of the SiC sandpaper should be given credit for the LED, then I would agree with your argument. Since Stokes observations only led to the concept of fluorescence in materials, not a lamp, it is only a component of, but not the concept of a fluorescent lamp. However, I am not an expert in the history of the LED. I am just making a case for it and arguing your point where I see it's difference, so I am open for it's debate. This still does not address the fact that some information of history is still incorrect. If you are going to provide a brief account of history, then it must be accurate. What is currently written about Nick Holonyak Jr. is inaccurate and misleading. The link I provided is from his own brief biography web page at the University Of Illinois, Champaign-Urbana. Danpeddle 11:44, 26 December 2006 (UTC)

Why is there not a section on History? I read other components and they provide a history. Danpeddle 11:44, 26 December 2006 (UTC)

Because you haven't begun one. Why not start one and try to work in some of your ideas about the history of electroluminescent phenomena and how they are related to the LED's development. It is VERY well established however, that Holonyak is the inventor of the visible light LED and I would not want that changed in the article. Is he also the inventor of the first solid state visible laser diode too? Maybe, I don't know. But he is certainly the father of the LED as we know it today.--Deglr6328 18:59, 26 December 2006 (UTC)
Touché! I haven't tried to start one because I have not learned how to do this yet and I am not sure how much time I may be able to dedicate (I am on vacation right now). I got started in this because I saw errors with some of the electronic components that I've worked with or continue to work with, such as LED lighting. I thought it better to just insert my thoughts to let the community debate it and the experienced people work on adding it. Danpeddle 23:26, 26 December 2006 (UTC)
As for Holonyak, I believe more research needs to be done. His own accounts are a tad confusing and his web pages at U of I are conflicting. Nonetheless, he invented the visible-spectrum LED LASER. Perhaps we can contact him for further details? (He's still at U of I) I do recommend reading his accounts in articles, especially the 1980 (date ?) IEEE article and his (many) biographies. I believe he would want the truth, especially after reading his account of the transistor. What I also believe is that it was the alloy that gave birth to the practical LED and it was implemented in the form of a LASER LED in 1962 (invention on one hand, credit on the other - in this case, credit to the practical LED). I am curious, how can you say for certain on the LED when you do not know he invented the visible-spectrum LASER (solid state) LED? His work is more into switching, such as transistors and thyristors. Currently (since around 1980) he is working on the LET (Light Emitting Transistor). And LASERs certainly are part of switches in communications and full spectrum ability allows several communications along the same fiber optic. A practical LED would not be so good at this, but is better for illuminating. But, then you never know, right? Danpeddle 23:28, 26 December 2006 (UTC)
Umm well, he HAS received practically countless awards and medals for the invention of the led. One particularly important one being the 2002 national medal of technology. [11] They don't hand those things out like grammys you know! --Deglr6328 09:10, 29 December 2006 (UTC)
First, please read what I am debating. His university website at http://www.micro.uiuc.edu/ssdl/ states "He was the first (1960) to grow GaAs1-xPx (an alloy) and in 1962 the first to construct a visible-spectrum semiconductor laser [3]" and "For this work he is considered the inventor of the first practical LED, the red GaAs1-xPx LED. This marks also the beginning of the use of III-V alloys in semiconductor devices, including in heterojunctions and quantum well heterostructures." Words like "considered" and "first practical" jump out at you. Even the Japanese prize states "first practical light emitting diode." Again, you see the words "first practical," which tells me that there was an impractical one before it! In fact, many times. There were also LEDs developed before this that were not visible. Second, I believe it to be the III-V epitaxy and that he was the first to grow GaAs1-xPx that he is "considered" the inventor of the "first practical" visible-spectrum LED. I believe "first practical" refers to the ease and cost effectiveness that this component can be readily manufactured. AND in 1962 it was a visible-spectrum "semiconductor" LASER (as I said, this is from his unversity's website). What I am arguing is the importance of the facts, how we word information to promote a source of reference and learning. It must be accurate. So, therefore, we must read and dissect correctly the information researched. Danpeddle 05:37, 24 January 2007 (UTC)

For reference, there is his citation when awarded the Japan Prize: [12]. There is also his article

Holonyak, Nick Jr. (Nov./Dec. 2000). "From transistors to light emitters". Journal of Selected Topics in Quantum Electronics 6 (6): 1190-1200. ,

where he says, "The first practical visible-spectrum LED, GaAs1-xPx, came into existence in 1962 (based on work from 1960 to 1962) ..." (with citation to an article on the epitaxial growth technique, and US Patent 3 249 473 (Google link)). The attached biography of that article states, "His work from 1960 to 1962 on GaAsP ... led to the commercial introduction of GaAsP LEDs."

Hope this helps. -- The Photon 02:02, 30 December 2006 (UTC)

A recent article points out that a Russian scientist first described in an academic paper the principles behind the LED, back in the 1920's. See: [13] - maybe this could be used to update the article? User:Kena

This really appears legit [14] it may not have been the first practical led but he had light emission onset vs. current curves, recorded light emission spectra and everything. This goes way beyond simple observation of electroluminescence, I think we have a new inventor of the led here. Its a very important development.--Deglr6328 08:37, 12 April 2007 (UTC)

LED Christmas lights

I've added a photo with a caption stating that LED Christmas lights are becoming popular in "some North American cities", but can anyone back this up? I know they are extremely popular this year in Ottawa, but I haven't a clue if this popularity is only a local thing, a national thing, or something sparking (haha, pun) across the continent. Are LED X-mas lights popular where you live? Eiffelle 05:15, 24 December 2006 (UTC)

I feel like a jerk doing this but....I moved your image to the article on christmas lights. I just removed two other images from the article today because I felt that they were not unique and did not offer the reader any new or interesting information that wasn't already in the article's other images. I think that if we are going to add images to an already somewhat cluttered page like this it should be of LEDs in TRULY novel applications or showing parts of them not already clear in other images on the page. sorry.--Deglr6328 05:33, 24 December 2006 (UTC)
LED Christmas lights seem to be growing in popularity. I'd guess that about 10% of the lights at the local home-improvement stores (in New Hampshire, New England, USA) were LED lights this year, and in my household, our indoor/outdoor SAHLD (Seasonally-Appropriate Holiday Light Display) is about 25% LED. There's no doubt that the LED Christmas Lights are far more energy-efficient than the old incandescent lights and the colors produced are much more pure (saturated), but for white lights, you just don't get that same "warm" color temperature nor the shift towards "ever-warmer" color temperatures when dimmed.
Atlant 14:40, 26 December 2006 (UTC)
I think the LED Christmas lights should be called Holiday lighting or LED Light Strings (but in accent lighting they also use a type of LED light string), especially since there are LED Light strings for other holidays. Also, this is just another application for lighting. I don't believe we need to detail so much the applications. I also do not think that providing a cost is good unless that figure is referenced to something like the lighting industry or a government study, it needs credibilty (I saw LED strings much cheaper than what is mention in this article). Personally, since you do not cost anything else, leave out the cost. Better is the approximate cost difference this year, projected cost difference by year and percent savings over incandescent holiday lights in terms of energy (or typical efficiency difference), especially since these incandescents are one of the least efficient forms of incandescent lighting. Danpeddle 23:53, 26 December 2006 (UTC)


could someone add mention to the pros and cons of how leds compare to other forms of lighting environmentally? How much and what kind of waste is produced manufacturing them and disposing of them compared to other sources?65.96.190.159 04:28, 4 January 2007 (UTC)

Who invented blue LEDs?

User Miwaya seems intent on removing all information in the article relating to Shuji Nakamura's invention of the blue led and replacing it with the "official Nichia" version of history where he is completely absent. No surprise considering they lost a 7 million dollar lawsuit from Nakamura. In any case Miwaya (who has obviously begun sock puppeting as user "Maslinka" and who began these edits with an IP that traces to Nagoya Japan) refuses to discuss his edits and as long as he does so I will revert them out of hand as being bad faith and unsubstantiated.--Deglr6328 09:45, 17 January 2007 (UTC)

"As is known throughout the world, Blue LEDs have been developed based upon the pioneering technology of Professor Isamu Akasaki of the School of Engineering, Nagoya University (currently, Professor Emeritus of Nagoya University, and a Professor of Meijo University). "
This sentence is 1 sentence of press release by Nichia Corporation [15].
Therefore, it is a mistake that Nichia developed LED for the first time. I think that an encyclopedia should mention the truth
. With best regards—Preceding unsigned comment added by Miwaya (talk • contribs)

Do you work for nichia? Because that is the only possible way I could see someone taking such a statement a face value. Nichia, being sued by Nakamura at the time, obviously had a vested interest in claiming that he had nothing to do with the invention of the LED. I am not going to allow you to whitewash the led article of all information about Nakamura based on a press release. If you want to state that "Nichia claimes such and such in this press release" ON THE NICHIA PAGE, that's fine. It does not belong on the LED page. Please place all further correspondence on the TALK page of the articles in question. Also see articles Wikipedia:Policies and guidelines and Wikipedia:Sock puppetry. --Deglr6328 18:19, 17 January 2007 (UTC)
(copied from somewhere by user:Miwaya) You have presented no convincing evidence of the inventio of the blue led by any other person than nakamura. If you continue to add this bias misinformation to the led article I will initiate a request for comment.--Deglr6328 03:18, 20 January 2007 (UTC)

Why do you say a partial bias misinformation? I write an article based on a perfect evidence. About first nitride based p-n junction UV/blue-LED, it is mentioned in this manuscripts in 1989, which reported by the "Jpn. J. Appl. Phys. Vol. 28 (1989) L2112-L2114" [16]. Moreover, Prof. Nakamura does not begin a study about nitride based blue LED then. Prof. Nakamura should have begun a study in 1990. I want to prepare further evidence if you think it not to be good for evidence.


Getting high crystalline quality of GaN and conductive control in GaN were important technology to realize GaN based UV/blue LED. Prof. Akasaki and his group succeed in realization of high crystalline quality GaN in 1986 which reported by "H. Amano, N. Sawaki, I. Akasaki and Y. Toyoda: Appl. Phys. Lett. 48 (1986) 353[AIP]." . Moreover, they realized pn junction and realized GaN based LED in 1989, which report by the "Jpn. J. Appl. Phys. Vol. 28 (1989) L2112-L2114" [17]. You should be able to read "The p-n junction LED using Mg-doped GaN treated with LEEBI as the p-type material showed strong near-band-edge emission due to the hole injection from the p-layer to the n-layer at room temperature. " in abstract of this manuscript [18].
The low temperature buffer layer technology and Mg-doped technology are used approximately entirely with marketed LED now.—Preceding unsigned comment added by Miwaya (talk • contribs)

SIGN your edits! User Miwaya continues to add the erroneous information about Isamu Akasaki "inventing the blue led" based on Mg doped GaN. This is no more true than claiming that Herb Maruska, the man who first observed violet electroluminescence from an Mg doped GaN crystal in 1972 invented the blue led. Isamu Akasaki's discovery of annealed Mg doped GaN no more resulted in a commercial blue led than did Maruska's. Efficient blue GaN emitters were developed by Shuji Nakamura's invention of the InGaN/AlGaN double heterostructure system. [19] No one attributes the invention of the blue led to either Maruska or Akasaki except you, wikipedia is not the place to push your agenda. STOP REMOVING THIS INFORMATION FROM THE ARTICLE. --Deglr6328 08:20, 20 January 2007 (UTC)

Listed at RfC http://en.wikipedia.org/wiki/Wikipedia:Requests_for_comment/Maths%2C_science%2C_and_technology#Technology_and_engineering --Deglr6328 08:29, 20 January 2007 (UTC)

Did you read the following the manuscript? Japanese Journal of Applied Physics Vol. 45, No. 12, 2006, pp. 9001-9010 [20]. A photograph of world's first blue light-emitting diode carried at figure 7 of this manuscript. In addition, it is LED of MIS structure that was realized by Maruska. Because pn junction LEDis realized by Akasaki and his group, they should be inventors of blue light-emitting diode. Moreover, Matsuoka and NTT group developed heterojunction of InGaN and GaN system.—Preceding unsigned comment added by Miwaya (talk • contribs)

I'm afraid you are up against a nearly complete worldwide consensous of Nakamura inventing the blue LED, not Akasaki and you are going to need a better source than a press release from Nichia saying otherwise. --Deglr6328 19:38, 20 January 2007 (UTC)
Came here from the RfC. If you want to say that Nichia invented it (or even has a claim to inventing it), you'll need to quote an independent reliable source, which a Nichia press release certainly isn't. Deducing the inventor from sources that don't explicitly say it qualifies as original research and so can't be included. I've got to side with Deglr6328 here. Trebor 23:01, 21 January 2007 (UTC)
Came here from RfC, too. I didn't register to view Japanese Journal of Applied Physics Vol. 45, No. 12, 2006, pp. 9001-9010, but at least that seems to be a peer reviewed article. However, it's from 2006 - many years after the invention. Is there no patent information available for Japan? — Sebastian 05:45, 22 January 2007 (UTC)

Who invented what

Blue LEDs existed before Nakamura's invention. What Nakamura invented was a high-brightness blue LED. In his 1993 patent application (US Patent No. 5,578,839), he refers to several prior publications, the earliest being "Jpn. Pat. Appln. KOKAI Publication No. 64-17484". Here are its details from the Japanese Patent Office website:

  • Title: Semiconductor Light Emitting Element
  • Applicant: NTT
  • Date of filing: 13th July 1987
  • Inventors: Hidenao Tanaka, Takashi Matsuoka, Kunishige Oe

This patent describes an LED that emits blue light with a "wavelength of 4800 nm" [sic]. As far as I can tell, all the other publications referred to in Nakamura's patent also relate to blue LEDs. But he goes on to say that "All conventional light-emitting devices are unsatisfactory in both output power and luminance, and have no satisfactory luminosity."

So basically, blue LEDs have been around since the mid 1980s, but Nakamura was the first to develop a practical device. -- Sakurambo 桜ん坊 10:31, 22 January 2007 (UTC)

Wonderful! This is the best contribution in this discussion so far! So, I'm changing the article to include this fact. — Sebastian 22:38, 22 January 2007 (UTC)
Thanks :-). Your edit is wrong however. The fact that Tanaka et al. (1987) is the earliest patent referred to by Nakamura in his 1993 patent doesn't mean that they were the first to develop a blue LED. Jacques Pankove made one as early as 1971, and the earliest (albeit unreliable) reports go back as far as 1861 (that's right, eighteen sixty-one). The blue LEDs you see everywhere these days largely owe their existence to Nakamura. I'd put this in the article myself but I don't have time right now. Maybe tomorrow. -- Sakurambo 桜ん坊 00:30, 23 January 2007 (UTC)
Sorry about that. I won't interfere with the article again until you edit it. I'm impressed again, and delighted about the Ernest Glitch gem you dug up! Weren't those people polymaths!? Do you know if anyone ever tried to reproduce his experiment?
Back to our topic: You already rewrote the title to contain two wildcard words; maybe we should add a third "who did what?" Maybe asking who invented it is the wrong question. It's sounds like asking who invented the transatlantic telephone cable. I wouldn't say Cyrus Field invented it - there have been phone cables and transatlantic telegraph cables before, so the idea was already there. The interesting question is who realized it, and it seems like all the names you mention should be in the article. — Sebastian 06:44, 23 January 2007 (UTC)
ZOMGZLOL! The "Ernest Glitch" article is a joke!!! I once had correspondence with the author of that website a few years ago in which I commended him for his absurdly elaborate ruse and worried that they were so good they would fool people into thinking things like the nitrogen laser were actually invented in the Victorian age. It seems I was right! :) :) --Deglr6328 08:45, 23 January 2007 (UTC)
Oops! :-D I'm glad you pointed that out. In that case I guess we should credit Jacques Pankove as being the first to make a blue LED. -- Sakurambo 桜ん坊 09:34, 23 January 2007 (UTC)
Well, then, tell your friend it's nice to see that there is still at least one polymath alive today! It is a well written piece. I don't think it's too harmful - or else I wouldn't believe in Wikipedia! — Sebastian 09:44, 23 January 2007 (UTC)

NOTE: I should probably also point out that the assignee of Nakamura's 1993 patent is Nichia Chemical Industries. If someone from Nichia is trying to claim that highly efficient blue LEDs existed before Nakamura's invention, then this document should put an end to the argument. -- Sakurambo 桜ん坊 11:30, 22 January 2007 (UTC)

Intro

WHy so much about the first few years in the intro? The first few patents seems like some quite trivial for the overview...

24.95.50.181 03:33, 24 March 2007 (UTC)

Color lumens

It would be good to have a table of lumens vs. color for various typical current LEDs. This is a product of the efficiency of the devices and the response of the human eye. The article is kind of a hodge-podge collection of exotic info, not so good for typical current info.-69.87.200.211 10:17, 15 May 2007 (UTC)

I believe you are talking about a color efficiency curve. It's better to understand a given amount energy used to determine the amount of lumen's produced for each color OR a given amount of lumens used to determine energy needs for each color. This way you relative comparison. Danpeddle 00:12, 3 October 2007 (UTC)

Typical LEDs are not bright or efficient

This article is currently quite misleading about typical current LED brightness and efficiency. And there is no mention of mcd, which is the most commonly used term for rating ordinary LEDs.-69.87.203.48 21:10, 19 May 2007 (UTC)

The lighting industry doesn't use mcd, some LED manufactures do. We use a defined standard from the IESNA (Illuminating Engineering Society of North America). Here we define the efficiency in lumen's per watt and brightness in lumen's, but we can convert from candelas too (milli candelas are too small). The problem with the candela is it is based on the brightest (pin) point of the LED instead of light as a whole. We measure the LEDs (and other lighting) in a spheroid chamber where the total light output is collected and measured. This gives us a direct comparison between different forms of lighting, such as incandescent and fluorescent. Danpeddle 00:38, 3 October 2007 (UTC)

LEDs are getting more and more efficient and in many cases are more efficient than currently used light bulbs. What is misleading?--Gloriamarie 21:16, 3 August 2007 (UTC)

The glowing comparison to incandescents is misleading because it leaves open the question of how they compare with fluorescent, which is a more appropriate standard of comparison if you care about efficiency. It would be good to see a good sourced comparison. Dicklyon 22:28, 3 August 2007 (UTC)
The comparison to incandescent is normal, this is the light source people prefer based on the output color it typically generates. When comparing light sources, you must take into account the color that is cast by the light source. People today still feel the CFLs used for residential (incandescent replacements) are too white (caused by the blue white light). If you are comparing energy, then we use lumen's per watt and we can compare to any form of lighting, including the more efficient HID. However, the standard for measurement has come under fire lately. Some manufacturer's, seeing the fad for LED technology, have interpreted the test slightly different to allow their LED products to "achieve" a higher lumen's per watt. You will see companies making claims of 100 lumen's per watt, but this might be the result of measuring the light output when a momentary and destructive pulse is used on the LED. This, in turn, produces a brighter than normal light for less than a millisecond before the LED is destroyed. Currently, newer LEDs are about as efficient as fluorescent lighting. Unfortunately, they are also more expensive to produce for room lighting applications. Danpeddle 00:38, 3 October 2007 (UTC)

ballast buzz

It is absurd that someone just censored mentioning the traditional buzz of (some) ballasts. WP articles are not advocates of any tech, nor unconcerned with history!-69.87.203.17 23:28, 27 May 2007 (UTC)

One of the two removed statements was "CFLs do still emit a quiet buzz, while LEDs are completely silent." This statement, containing no qualifiers, is flatly wrong. Most electronic CFL ballasts are as quiet as the control circuitry of any line-powered LED lamp.
Atlant 01:18, 28 May 2007 (UTC)
In today's ballast, if a buzz is heard, it is because the core and bobbin of the transformers (we just say magnetics, they might also be inductors) are not glued or taped to prevent them from resonating. However, these days, ballast manufacturers are very aware of this and have very good process control. Today's ballasts are high frequency, running from approx. 40KHz to approx. 100KHz when dimmed. They are, essentially, a complicated switch-mode power supply. Ballasts of the past were large bulky inefficient transformers that operated on line frequency, 60Hz, or rectified line frequency, 120Hz and produced that audible hum, mostly from corona (around the insulating paper/mica). Danpeddle 00:02, 3 October 2007 (UTC)

white LED I-V curve

who can show me the white LED I-V curve?? thanks!! —The preceding unsigned comment was added by Ryan siow (talk • contribs) 08:19, August 22, 2007 (UTC).

Are variable color LEDs practical?

I understand that some LEDs can be manufactured that will change color with the applied voltage. Are these commercially available at the moment, and are they practical in terms of expected life, reliability. etc? —Preceding unsigned comment added by 68.162.238.162 (talk) 02:26, 5 September 2007 (UTC)

This sounds confused. Each LED die will not change colour, however one can put 2 or 3 in a package and vary the supply to each. Tabby (talk) 06:19, 24 January 2008 (UTC)

please note that article talk pages are for discussion of the article, not general discussion. please see WP:FORUM. Anastrophe (talk) 06:23, 24 January 2008 (UTC)

Pronunciation

I hear LED pronounced like the word 'led' much more often than L-E-D and think 'lead' may be the generally accepted pronunciation. So maybe all the "an LED"s in the article should be changed to "a LED"s. Keep in mind words like 'LASER' and 'SCUBA' before writing off this proposal. The dictionary doesn't make the definitions and pronunciation, it just keeps track of them -- meaning it isn't always up to date. Just check google. "a LED" 224k results. "an LED" is 199k results.—Preceding unsigned comment added by 75.72.206.28 (talk) 02:56, 11 December 2007 (UTC)

it should go without saying that google search count results have virtually no probative value. i've been pronouncing it "el-ee-dee" for some forty years or so, and i've never had anyone ask "what are you talking about". i've never heard anyone refer to them as "leds". and... mirriam webster online corroborates. i'm going to cite and change it. Anastrophe (talk) 08:41, 4 January 2008 (UTC)
I work within the technical community in the United States and although I have always said "L-E-D(s)", you do hear it pronounced as "led(s)". To me, though, that's too ambiguous with the element lead as in "ROHS has forced us to use lead-free leds".
Atlant (talk) 14:02, 4 January 2008 (UTC)
That explains why I see "an LED" here and there. I believe I used to say "el-ee-dee" years ago before dealing with them on a regular basis, at some point I switched to "led" because it's quicker. Having forgotten this I was wondering what bizarre rule for acronyms was being applied to make people say "an led". As LEDs are rarely written as L.E.D. I believe it is an acronym like NASA, and I personally believe all instances in this article should be changed to "a LED" because reading "an led" is distracting to me, and also uncommon in my everyday readings of them (mostly dealing with LEDs used in torches). - 124.254.121.73 (talk) 17:10, 8 February 2008 (UTC)
There is nothing bizarre about "an el ee dee". The only question is whether it should it be "a led" or "an el ee dee". Personally I've never heard it pronounced "a led". Thunderbird2 (talk) 17:27, 8 February 2008 (UTC)