Talk:Light-emitting diode

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History of Blue LED[edit]

This is missing from the Blue LED section: Nakamura's GaN types were not the first blue LEDs. Blue LEDs were first developed by RCA in 1972. [1] And SiC-types were first commercially sold in the U.S. by Cree in 1989. [2]. I also know this because I bought & still have them :-) They are not very bright.

Rich S 10001 (talk) 20:26, 26 August 2015 (UTC)

@Rich S 10001: Looks good, and welcome to Wikipedia! This is a volunteer project, as you know, so we generally encourage new editors to be bold, and add new content to the article yourself (as long as it has references, which you have already done). If you don't yet feel comfortable doing it, reply below and I'd be glad to do it. – voidxor 20:25, 27 August 2015 (UTC)
Yes check.svg Done. Since we haven't heard back, I went ahead and added it. Thanks for the submission! – voidxor 20:34, 14 September 2015 (UTC)

Section "Covers" relevant?[edit]

Frankly, I don't see the relevance of the information about LED covers for the article. Besides, said section is written rather poorly (imho), with lots of redundant content. Noggo (talk) 19:28, 16 October 2015 (UTC)

  • Remove. It reads like an advertisement, which is why I tagged it as such in August. I did a little work on it at the time, but it still contributes nothing to this article. Just now, I noticed it only has one reference so I tagged it {{Refimprove section}} as well. Note that the section originated as a separate article, and an AfD discussion concluded it should be merged here. To quote that discussion, "Obviously consensus at the destination is free to determine how much material, if any, should be integrated..." I guess that means we are free to decide what to do with it from here. – voidxor 20:09, 16 October 2015 (UTC)
  • Gone. Andy Dingley (talk) 20:55, 16 October 2015 (UTC)
  • Agreed. It's not relevant to this article. Jeh (talk) 21:34, 16 October 2015 (UTC)

Comments and questions[edit]

This is a very well written article. It flows and it's very clear. However, I feel it contains a little too much information. Also, I feel it is informative but it is not particularly entertaining from a reader's standpoint (my background is technical).

I would like to add a series of comments and questions.

1. "Blue LEDs were first developed by RCA in 1972.[32] SiC-types were first commercially sold in the United States by Cree in 1989.[33] However, these initial blue LEDs were not very bright."

Which ones? 1972 or 1989 versions?

2. "Nakamura, Akasaki and Amano were awarded the Nobel prize in physics for their work."

It would be nice to add the year.

3. "It has been speculated that the use of six-inch silicon wafers instead of two-inch sapphire wafers and epitaxy manufacturing processes could reduce production costs by up to 90%."

This was speculated. What is the actual figure now?

4. "Note that these efficiencies are for the LED chip only, held at low temperature in a lab. Lighting works at higher temperature and with drive circuit losses, so efficiencies are much lower."

As usual, just like with cars and fuel efficiency, LEDs efficiency is biased primarily for marketing purposes since most applications do not work at "low temperatures".

5. "LED light output rises at lower temperatures. Thus, LED technology may be a good replacement in uses such as supermarket freezer lighting, and will last longer than other technologies. Because LEDs emit less heat than incandescent lamps, they are an energy-efficient technology for uses such as in freezers and refrigerators."

The two sentences are redundant.

6. "High-brightness blue LEDs invented by Shuji Nakamura of Nichia Corporation using gallium nitride revolutionized LED lighting, making high-power light sources practical."

What was the year?

7. Why is ultraviolet light called black light if it's indeed violet and not black?

8. What are "pi electrons"?

9. "Ultra-high-output: 20 mA at approximately 2 or 4–5 V, designed for viewing in direct sunlight."

I don't understand what this sentence means.

10. The naming for high-power LEDs (HPLEDs) or high-output LEDs (HO-LEDs) is not consistent (the second has a hyphen while the first doesn't). Is there a reason?

11. The first sentence of most of the subsections of "Application-specific variations" is not in the SVO form.

12. "Usually they are packaged in a sealed enclosure similar to a lamps they were designed to replace. "

This sentence is ambiguous.

13. What are "cool-white LEDs"? Why white light should be "cool"?

14. "Plant growers are interested in LEDs because they are more energy-efficient, emit less heat (can damage plants close to hot lamps)".

This fragment does not make much sense. The sentence needs to be revised.

ICE77 (talk) 03:33, 10 November 2015 (UTC)

Thank you for your read through and helpful cleanup. The ambiguities you're listing should certainly be fixed or mentioned inline in the article. So with that in mind, using your numbering scheme:
  1. Fixed by adding "neither". The ambiguous sentence was purely a transition into high-brightness blue LEDs.
  2. Already done by an anonymous editor.
  3. Crystal Clear action edit remove.png Removed, as I don't think speculation about how to improve manufacturing costs is very encyclopedic. The source was from 2009 and white LEDs are certainly a lot cheaper now.
  4. Symbol question.svg Question: That being the case, how should we address it?
  5. Fixed by rewording for simplicity.
  6. yellow tickY Partly done by tagging {{When}}.
  7. Disagree because it's not violet; it's ultraviolet, meaning that it's higher than violet in the spectrum. See Black light.
  8. Fixed by linking to Pi bond.
  9. Fixed by changing the formatting. You don't understand the sentence because it's not a sentence; it's a sentence fragment and therefore shouldn't have a period. I've converted it to a definition list per MOS:DEFLIST.
  10. Fixed a Google search revealed they should probably all have hyphens. I've added the missing ones.
  11. Fixed by forming complete sentences.
  12. Fixed by making it clear that we're talking about the shape of the enclosure (e.g. a bulb).
  13. Disagree . See Color temperature, which is already linked from that section.
  14. Crystal Clear action edit remove.png Removed as non-encyclopedic ambiguous application-specific anecdotal outdated uncited text.
– voidxor 01:22, 12 November 2015 (UTC)

voidxor, thanks for implementing a variety of improvements after reading my comments and questions.

4. I would probably replace data at low temperatures with data at room temperature.

7. I will have to read the article about "black light" to understand.

13. It looks as if "cool-white" light has a temperature of 5,000 K. I'll have to read about it.

ICE77 (talk) 21:57, 16 November 2015 (UTC)

@ICE77: I agree wholeheartedly on #4, but do you know of any such data sources? – voidxor 22:29, 17 November 2015 (UTC)

4. I don't know of any information on data at room temperature.

ICE77 (talk) 18:28, 18 November 2015 (UTC)

How about we just remove the efficacy table for now? It's pulled straight out of the 2012 Philips catalog and only applies to their specific models. They may or may not have been the top efficiencies at that time, but I doubt they are now, so I don't know why they're noteworthy enough to include here. Doing so implies that all LEDs of each given color operate at nearly that exact efficacy. – voidxor 22:01, 18 November 2015 (UTC)

voidxor, you just hit the bullseye. Marketing figures have a history of being not always practical. I have seen tons of stuff like that in solar cells going into solar panels or cars tested in a lab and hitting the road.

ICE77 (talk) 19:36, 20 November 2015 (UTC)

"wire bond" undocumented, past documentation provided but deleted[edit]

A "wire bond" or jumper is provided in most LED which is not for current flow but to temporarily prevent immediate damage from reverse polarity connections, which small led otherwise would be (Forest Mimms III, Archer notes). The feature is limited since the jumper also must not bypass all forward current; it is a comprimise feature that allows only very brief (circuit on, or test touch) reverse current. (electrons jump the gap which can be seen with a magnifying glass)

(another proof: cpu chips contain min-transistors and DO emit light (which is why they are packaged in DARK glass. do CPU have jumper wires between each transistor or for that matter do transistors or vaccum tubes? NO. neither do LED except as a convenience feature)

(motherboard/cpu also emit radiation while on, so leaving them outside of an enclosed metal box is not suggested)

false information in article[edit]

a picture shows "gold wire bond" i beleive is incorrect. the wires shown appear to be circuity wires not a jumper bridge between the NP layer of the 1/2 transistor (LED, diode)

way too much information on a not-so-important topic, in article[edit]

please make a "infatuated about led" article and move material there

— Preceding unsigned comment added by 72.219.204.96 (talkcontribs) 14 dec 2015 23:40‎ (UTC)

So you only want to read information that you already know?? SpinningSpark 14:59, 12 January 2016 (UTC)

External links modified[edit]

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Question? Archived sources still need to be checked

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Disadvantages - Light Pollution[edit]

Note revision to remove incorrect (yet still widely repeated) statement that Rayleigh scattering increases light pollution, particularly sky glow, from white LED used in outdoor applications. The topic is the subject of recent peer-revewed research (discussed and referenced on Light Pollution and Sky Glow pages, and also referenced here now).

Also previous statements about some dark sky advocacy orgs (i.e. International Dark-Sky Assoc) are not appropriate in this level article on LED. Besides, the IDA recommendation is controversial.

The phrase "Light Pollution" often has much broader meaning than just sky glow (such as ecological impacts, touched on narrowly in another "Disadvantages - Impact on insects" bullet, impacts on human health, glare, etc.). Probably it would be most sensible to continue with "Light Pollution" as addressing sky glow (as seen by humans) as it is arguably the most common meaning for light pollution, then broaden the "Impact on insects" to address "Impacts on ecosystems" and add "Impact on (human) health." Cluginbuhl (talk) 18:35, 15 April 2016 (UTC)