Talk:Light-emitting diode

Calculator Picture

Is it just me or does this display look remarkably like Nixie Tubes?

not particularly, no. Anastrophe (talk) 08:10, 17 January 2008 (UTC)

Section layout

Some of the layout of the sections don't make much sense. My section numbers are from [1]. Section 1 is the history and then Section 7 is "a" history? Sections 7.x are unrelated to the history, altho 7.2.1 might be related. Yngvarr 18:44, 30 January 2008 (UTC)

fixed --Thorseth (talk) 07:26, 15 October 2008 (UTC)

What a mess

Seems there are people editing that don't understand the subject, and are drawing numerous oversimlified conclusions from references. The article currently contains an awful lot of misinformation, due I think to misunderstnding material. Personally I'm not interested in editing things that are changed by various folk that lack understanding of the subject material, its just pointless.

Are there any mechanisms in wikipedia to help improve this problem? If not the article will continue to contain a fair amount of misinformation, since its what unqualified people have been told by enthusiastic promoters with $ signs in their eyes. Tabby (talk) 19:35, 21 February 2008 (UTC)

A or B class

Meanwhile I think its time to consider changing A class to B class, due to the many errors in an otherwise thorough article. Tabby (talk) 19:48, 21 February 2008 (UTC)

History section

There were two history sections, one at the beginning and one at the end of the article. I moved the content at the end toward the beginning, but there are some points of redundancy that an expert on this article should try to remove: for example, Losev's invention is mentioned twice. Shalom (Hello • Peace) 15:21, 10 March 2008 (UTC)

fixed --Thorseth (talk) 07:27, 15 October 2008 (UTC)

Removed section from article

Removed this sentence: In early 2008, researchers at Bilkent University in Turkey demonstrated a new technique for producing white light from blue LEDs coated with nanocrystals. This approach was shown giving off "more than 300 lumens per watt".

This is about visible lumens per watt of emitted light, not about lumens of visible light per electrical watt, as the others, and therefore not comparable. -- 87.187.10.235 (talk) 18:25, 8 April 2008 (UTC)

That DNA crap is unwikilike

and quite frankly I'm not sure if every single new piece of research belongs on Wikipedia. Unless someone comes along and edits it for style, I'm deleting it. eigenlambda (talk) 18:51, 8 April 2008 (UTC)

please see WP:IDONTLIKEIT. it's interesting, and describes genuine research. your justification for removal doesn't seem to be based on policy. Anastrophe (talk) 03:58, 20 April 2008 (UTC)

i should add that this research is very exciting. it could mean dramatic reduction in the cost of manufacture of LEDs. it belongs in the article. if you don't like how it's written: fix it. don't just delete sourced material. Anastrophe (talk) 04:01, 20 April 2008 (UTC)

Overly-technical lead?

Is it just me, or is the first paragraph of the lead a tad overly-technical? Things like that belong in the article, of course, but the first paragraph of the lead should probably have more of a layman's description, useful for people with no background in the subject. The second paragraph of the lead seems to work quite well for this; I'm just wondering if it's good to have such a technically-oriented paragraph before it. Maybe they should just be swapped. --Aquillion (talk) 03:02, 29 April 2008 (UTC)

I agree, a simple explanation at the top would be great. —Preceding unsigned comment added by 84.216.47.83 (talk) 19:21, 17 May 2008 (UTC)

Should this get a mention?

This development. Kaiwhakahaere (talk) 20:17, 8 May 2008 (UTC)

This important thing should be added

http://en.wikipedia.org/wiki/Haitz's_Law (talk) June 20 2008 --Reachtokaushik (talk) 09:46, 20 June 2008 (UTC) I put it in the history section and I am compiling a new graph. Available graphs are from around 2000 --Thorseth (talk) 12:40, 29 July 2008 (UTC)

Why is this article so long and unorganized?

There is a lot of good information in this article but is also has many problems:

There is a big paragraph/section on the history _before_ the discovery subsection which actually only has a small part about the discovery. A subsection of the history is about LED panels (should maybe be under applications). Then, very prominently there is a subsection about touch sensing with a reference to one paper and no examples of applications (how relevant is this?).

In the "physical function" subsection semiconductor physics is mixed with light extraction and after that a long list of materials that relate back to the semiconductor part.

The White LEDs section is a small article in itself that actually starts by talking about RGB systems that are in fact NOT white LEDs. The section (in my view) lacks organization and subsection. Maybe it should be its own article since the white LEDs are becoming so important.

The diagram in the OLED section have nothing to do with OLED, and why is "potential of OLED"s a subsection of "Efficiency and operational parameters"

There is a huge amount of information in this article but it seems to have been arranged with at shovel. If someone could explain the reasoning behind these "issues" I would be most grateful if not I will get to work on them since this is a subject I care a lot about.

--Thorseth (talk) 02:35, 4 July 2008 (UTC)

Take the shovel and go (and remove oled which isn't led). Mion (talk) 11:26, 4 July 2008 (UTC)

Proposal to put white LEDs in its own article

White (light) LEDs are becoming increasingly important, but the section is lacking in many ways so i suggest it gets moved to its own article. —Preceding unsigned comment added by Thorseth (talk • contribs) 14:05, 4 July 2008 (UTC)

We have Solid-state lighting and LED lamp if thats what you mean, please sign with ~~~~ at the end. Mion (talk) 14:32, 4 July 2008 (UTC)

Sorry that I forgot --Thorseth (talk) 12:07, 5 July 2008 (UTC)

I think the White led section should be cut in two "RGB systems" and "Phosphor coating"(or something) that could very well be much shorter. I also think that LED lamp is a very broad article that does not adress the issue of white light generation very much. --Thorseth (talk) 12:24, 5 July 2008 (UTC)

True, i also think that the white led section belongs to LED, you can take whatever type of led to make a led lamp, including white leds. Mion (talk) 12:51, 5 July 2008 (UTC)

White is not the only phosphor-based LED

I just bought some pink-magenta LEDs and it has a phosphor coating. I don't think the section on phosphor LEDs should be limited to white. Ginbot86 (talk) 20:25, 18 July 2008 (UTC)

"LED panels" should be put in its own article

This is a very long section on a single use of LEDs that says more about sinage and not so much about LEDs. If all the possible applications of LEDs had similar treatment the LED article would several MB in size.--Thorseth (talk) 13:15, 29 July 2008 (UTC)

Materials and colors

I just grabbed this table from the french wikipedia. I like how it relates color, material, voltage and wavelength. I just translated it and have not checked it for facts. It could replace the material section and the "voltage-color" table under "considerations". Any objections?

Color	Wavelength (nm)	Voltage (V)	Semi-conductur Material
Infrared	λ > 760	ΔV < 1,63	Aluminium gallium arsenide (AlGaAs)
Red	610 < λ < 760	1,63 < ΔV < 2,03	Aluminium gallium arsenide (AlGaAs) Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP)
Orange	590 < λ < 610	2,03 < ΔV < 2,10	Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP)
Yellow	570 < λ < 590	2,10 < ΔV < 2,18	Gallium arsenide phosphide (GaAsP) Aluminium gallium indium phosphide (AlGaInP)
Green	500 < λ < 570	2,18 < ΔV < 2,48	Gallium(III) nitride (GaN) Gallium(III) phosphide (GaP) Aluminium gallium indium phosphide (AlGaInP) Aluminium gallium phosphide (AlGaP)
Blue	450 < λ < 500	2,48 < ΔV < 2,76	Zinc selenide (ZnSe) Indium gallium nitride (InGaN) Indium gallium nitride (InGaN) Silicon carbide (SiC) as substrate Silicon (Si) as substrate — (under development)
Violet	400 < λ < 450	2,76 < ΔV < 3,1	Indium gallium nitride (InGaN)
Ultraviolet	λ < 400	ΔV > 3,1	diamant (C) Aluminium nitride (AlN) Aluminium gallium nitride (AlGaN) Aluminium gallium indium nitride (AlGaInN) — (down to 210 nm)
White	Broad spectrum	ΔV = 3,5	Blue/UV diode with phosphor

--Thorseth (talk) 11:32, 14 August 2008 (UTC)

Updated the table with information from the materials section--Thorseth (talk) 08:30, 15 August 2008 (UTC)

updated two links, missing a more specific link to Δ (delta has many uses) , support for the table. Mion (talk) 11:42, 15 August 2008 (UTC)

Δ = Modern Greek ? Mion (talk) 15:53, 18 August 2008 (UTC)

It is my understanding that Δ can also denote an interval of possible values, but i have been unable to find a good reference for this, but perhaps its use here is not entirely correct as Δ would be the interval and not the specific range. What do you think? --Thorseth (talk) 08:03, 19 August 2008 (UTC)

Well, if you mean a specific range ΔV = 0 < 2,48 V, its correct, but its not my field, so any suggestion is better than mine. Mion (talk) 21:58, 19 August 2008 (UTC)

Color VS. Operating Temperature

I recently took a science course in which one of the lessons involved dipping LEDs of various colors into liquid nitrogen to cool them. This caused the wavelength of the emitted light to shift towards the blue end of the electromagnetic spectrum (i.e. the yellow LED turned green, the green LED turned blue, etc.). This had something to do with band gap energy or something. Should this be mentioned in the article? Ilikefood (talk) 18:19, 29 August 2008 (UTC)

The effect you describe is important for understanding the basic physics of LEDs but still comparatively small for normal operation temperatures. I think it could be mentioned, but should perhaps be elaborated on in an in-depth article on LED physics.--Thorseth (talk) 07:01, 1 September 2008 (UTC)

Latest Discoveries

I really like Wikipedia as a news source and have a 'latest discovery' that I think should be added:

http://news.uns.purdue.edu/x/2008b/080717SandsLighting.html |Title=Advance brings low-cost, bright LED lighting closer to reality | Publisher=Purdue University

I believe that when applied, this possible reduced cost manufacturing process will have a profound impact on the enlarged use of LEDs for many lighting purposes, even though a time line for practical use has not been established. LED manufacturing, like all electronic device manufacturing, uses many toxic materials, but LEDs have less harmful materials contained within than say CCFLs and their mercury concerns.

I think more of these types of items could be included in Wikipedia as soon as published, for reference at least. Walrus Webtech (talk) 05:20, 1 September 2008 (UTC)

I think it might be included under experimental technologies, but on the other hand there are many scientific papers on LED every month. We can't reference all of them especially since this is a overview article.--Thorseth (talk) 07:24, 1 September 2008 (UTC)

Laptops with LED Screens

Which type of LED technology does Laptops with LED screens most commonly use? Blue LED, White LED or Colored LED. I am a bit confused about the different types of LED's.

Netbooks like the ASUS EEE PC and the Acer Aspire One, which type of technology do they use - do they just use white LED to light up the screen?

And do LED notebook screens pose a health hazzard if they are white LED or Blue LED? ("Blue Hazzard")? —Preceding mesmerator

To answer all three of your questions:

Netbooks probably use LED on higher-end models, and maybe fluorescent to cut costs.

LED-lit LCD screens use white LEDs.

I think the eye hazard of LED backlighting is minimal, and about the same as a standard fluorescent backlight. Ginbot86 (talk) 03:28, 2 December 2008 (UTC)

Green/Pure Green distinction

I have a comment to make about the table. I noticed that InGaN and GaN are both listed in the Green category. However, they are not the same shade of green as the others listed, they are a shade known as Pure Green or Emerald Green. I personally think that Pure Green should be listed separately from the other Green LEDs, not simply because they are a different shade, but they are considered a distinct category from traditional green LEDs. If anyone knows the difference in wavelenghts between Green and Pure Green, please post it here. ANDROS¹³³⁷ 02:29, 16 October 2008 (UTC)

Putting this here because as of now it's little more than random trivia.

Research on DNA

At the University of Cincinnati the DNA in salmon sperm has recently been discovered to amplify the effects and quality of an LED light[2] [3].

Christmas lights ...

Ok, my rather rash edits was reverted, so ill put my suggestion up here and see what happens. The subsection "Christmas light" under the section "Considerations for use" is, I think, misplaced and unnecessarily long. Non of the other niche applications are given more than a line or two. However I think that the application is interesting enough to be put in a separate article. Any objections or suggestions?

--Thorseth (talk) 15:12, 3 January 2009 (UTC)

I agree. But there already a lot in Christmas lighting technology so perhaps just merge with and link to that.Ccrrccrr (talk) 22:00, 3 January 2009 (UTC)

I hadn't noticed that article. I think you are right. --Thorseth (talk) 09:52, 4 January 2009 (UTC)

Overly confusing and technical Lead.

Please revise the lead to use some simpler terminology. 'p-n Junction' could instead say "junction of two different semiconductors, or 'p-n junction' ". Use of some dependent clauses to explain the rather technical terminology would be better. I had to reaad four articles to understand one lead, and that's not how a wikipedia article should go. I get the basic idea now, electricity goes into the element, light comes out, but it took way too much effort to have to learn that. ThuranX (talk) 00:01, 5 January 2009 (UTC)

Well, LEDs are pretty complex devices to begin with. The problem as I see it is that the lead is either going to be very technical or very long. I have made a suggestion below that I would like you to comment on:

A light-emitting-diode (LED) (Template:PronEng), is a semiconductor component, of the diode type, that emits light when an electric current is supplied in the forward direction of the diode. The effect is a form of electroluminescence where electrical energy is converted to light when electrons and electron holes are joined in the junction between a two semiconductor materials (p-n junction). The light is incoherent and narrow-spectrum.

The last sentence might be expendable, but besides that I don't think I can make the lead both easier and shorter without removing essential information. --Thorseth (talk) 09:30, 5 January 2009 (UTC)

copyright problems

The user User_talk:WikiEditorContributor has copy-pasted material from industri news web sites

please compare

ledjournal

wiki edit

and

ledinsider

wiki edit

The material is unreferenced and almost a direct copy. Can someone please take the nessesery steps as I don't have time--Thorseth (talk) 09:28, 12 January 2009 (UTC)

Removed section: Christmas lights

Maybe this section can be inserted somewhere else?, rather than being lost. Electron9 (talk) 14:09, 12 January 2009 (UTC)

xxxxxxxxxxxxxxx

Most LED Christmas lights (at least in 120-volt North America) are operated directly from mains electricity, with an in-line resistor (molded inside a small cylinder the same green or white color as the wire insulation) for each circuit. Older colors are operated in circuits of up to 60 LEDs, while newer or mixed colors are normally in one or two circuits of 25, 30, or 35. An example of Halloween lights is two different sets of 70 LEDs: the orange set is divded into two circuits with a one-kiloohm resistor each, while the purple (blue with red phosphor) set is three circuits with a 1.1 kΩ resistor each. Each circuit uses 2.4 watts, and from this it is derived that the LEDs are about 5 kΩ in total.

he alternating current can be seen in these sets by spinning one end of the string around. It is then apparent that the LEDs are on less than half of the time, being off when the voltage is negative (reverse-biased) or too low. The slightly-delayed rise and slow decay of phosphors can also be seen in each flash, depending on their phosphorescence. While inexpensive, the flickering caused by this method can be annoying to some people. Additionally, the unsmoothed peak voltage of nearly 170 total volts in each cycle shortens the life of the LEDs, though they are still rated for a service life (MTTF) of around 25 000 hours (if moisture does not rust them first). However, blue and deep-green ones are more prone to failure, especially early in their use.

There is already a rather extensive at Christmas_lighting_technology#LEDs so I think it would be safe to remove it.--Thorseth (talk) 13:57, 15 January 2009 (UTC)

Cree diode WP:OR WP:RS delete?

I'm concerned about the following paragraph:

Cree issued a press release on November 19th, 2008 about a laboratory prototype LED achieving 161 lumens/watt at 350 mA (Over 10 times more efficient than incandescent lightbulbs). Output was 173 lumens. Power works out to 1.075 watts. Voltage drop works out to 3.07 volts. Correlated color temperature was reported to be 4689 K.[4]

LED manufacturers and researchers tend to quote luminous efficacy of radiation (LER), rather than the overall ("wallplug") luminous efficacy of their devices.[5] This gives numbers that are larger than the overall efficacy, which is undoubtedly convenient for marketing, irrespective of any technical justification for its use. The cited press release does not give sufficient information to establish that the value cited is overall luminous efficacy, not LER. The paragraph above, however, gives a value for the voltage which is not given in the press release. If this were a true value, it would support the conclusion that the LE value given is wallplug luminous efficacy not LER. From the wording, however, I suspect that this uncited voltage was calculated by a Wikipedia editor from the values of luminous efficacy and current, assuming without justification that the efficacy given is the wallplug value. Besides being wrong, this is original research.

Finally, note that manufacturer's press releases are not reliable sources. They can be used as sources for Wikipedia articles only when they meet certain conditions, including that the information not be self-serving. Inflated luminous efficacy figures probably count as self-serving.

I am removing the sentences that are uncited and probably original research. I suggest that editors of this article delete the entire paragraph until it can be confirmed by a reliable source.--Srleffler (talk) 05:15, 13 January 2009 (UTC)

Thanks for removing the portions that were clearly OR. The 350 mA number is not OR, but was removed. That's OK with me, but if someone think's it's valuable you should feel free to add it back in.

I'm in favor of keeping the rest. Taking the issues one-by-one:

First is this luminous efficacy of radiation (LER) or luminous efficacy of a source (LES)? If it were LER, it would be lower than the products they have on the market already which are right near the 100 lm/W LES point, and about 250 to 300 lm/W LER. So it wouldn't be newsworthy. It is not, however, true wallplug efficacy, which would include ballast (drive circuit) losses, as it is a report on the performance of an LED, not an LED fixture or screw-in incandescent replacement which would include ballast losses. The LED can't be plugged into the wall, and thus wallplug efficacy is not the proper term. LES is the terminology established by international convention for what is measured here. We also know that LEDs of the type Cree makes have about 3 to 3.3 V voltage drop, so although the OR calculation of voltage doesn't belong in the article, one can reassure oneself that the 161 lm/W LER is consistent with expected voltages.

As far as the use of a press release, I note that 1) Cree is a pretty reputable company, and for example works closely with NIST on measurement of a lot of their devices. 2) Aside from being self-serving, this meets all the conditions mentioned above, and 3) The article says "Cree issued a press release..." rather than just stating the 161 lm/W as fact.

I do have a concern about quoting this value in a way that leads people to think it corresponds directly to what would be achieved in a fixture--an LED in a typical fixture is operating well above room temperature and that can degrade efficiency greatly. And, though this can be a small effect, drive circuit losses also need to be factored in.Ccrrccrr (talk) 12:44, 13 January 2009 (UTC)

Operating Room Surgical LED lights

For me this section looks like advertising and it should be removed. If nobody objects Ill do it within this week--Thorseth (talk) 14:01, 15 January 2009 (UTC)

Its certanly a very long section (in an already long article) for such a niche application. If it was forked to its own article it would likely be speedy'd as advertising. At least trim to much shorter (i.e. a bullet point, as elsewhere in the article) and remove all pov/adspeak. Wouldn't oppose complete removal. StealthFox 14:14, 15 January 2009 (UTC)

Peer review...

I will try to get the article ready for Wikipedia:Peer_review which means getting rid of all major clean up banners. The objective is of cause to get to featured article (WP:FA) status at some point.--Thorseth (talk) 14:31, 15 January 2009 (UTC)

Lens

A LED flashlight uses a small convex lens to create a beam from the light generated by the white LED. I have these type of lights. Powerzilla (talk) 21:01, 21 January 2009 (UTC)