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I like the "Colors and materials" section. But some of the numbers are just a little different than what I see elsewhere.
This article implies that green LEDs require "2.18 < ΔV < 4.0". When I look through supplier catalogs [1], I see many green LEDs rated at "1.9 V". So are those "1.9 V green LEDs" really more of a yellowish green, or are the numbers in this article a bit off, or am I misinterpreting something?
Should I pick a LED manufacturer at random and use their part catalog as a reference to update the voltages in that table? -- 68.0.124.33 ( talk) 23:16, 5 August 2009 (UTC)
How is this [1] or this [2] considered an array and not a single diode? In this datasheet [3] it even says "Over 2,750 lumens from a single chip" and again this one [4] says "Over 2,200 lumens from a single chip" If Haitz's Law is expressed in terms of lumens per package then it hardly seems justifiable to differentiate in this section alone. We don't say a quad-core CPU is faster (but only because there is more than one core) or this generation of CPU is faster (but only because it has more transistors) and thus we shouldn't say a quad-die LED is brighter (but only because some excuse here). There are many ways to increase the lumen output of an LED and increasing the substrate surface area is one of them. Are we going to be calculating that surface area and arbitrarily creating new categories now because one manufacturer encased 3 die in a single package? What difference does it make if one die is larger or if you are using 4 smaller die? If you are going to qualify it this way you might as well qualify statements for the whole article by placing that verbiage at the top. Don't forget the RGB white section too as those are also single-package arrays. I agree it should be mentioned that some LEDs come in a single-package array but I would never say I have anything other than a single LED regardless of the die count or substrate surface area. Thepaan ( talk) 00:25, 23 October 2009 (UTC)
References
I notice that Losev is still credited as the inventor. This was discussed here previously, and it appeared some rearrangement was anticipated. Also there doesn't seem to be any source cited for this info. (Never heard of him myself)
The bit about a bipolar transistor emitting light under certain condition, ie. cutting the case open, biasing etc. has been removed. This was also mentioned and it appeared it was staying, but 213.162.105.199 recently edited it out saying "they tried it and it didn't work". I have also heard that this is possible to do. But OR to remove something is surely as bad /worse than trying to publish your own OR. There may be a place for this info (LED trivia?). The fact that they tried it (once or more?) surely isnt right in Wikipedia.
This is a very detailed article, and even though I worked as a Radio 'Technical' Officer, I found the intro a bit too detailed. Now for 'conventional' current versus 'true' current flow!. [Kidding] ;-) -- 220.101.28.25 ( talk) 17:11, 24 October 2009 (UTC)
This graph is meaningless drivel. The only purpose I can see for it is to promote the agenda that "LED's are better". Why do I say this?
-- Juckto ( talk) 20:47, 19 November 2009 (UTC)
It is "very important" to avoid light pollution, is a biased statement that doesn't belong in the LED article. The movement that is against light, has no scientific proof to back up their crazyness. —Preceding unsigned comment added by 93.182.185.88 ( talk) 14:25, 4 December 2009 (UTC)
Why the hell doesn't the pronunciation guide apply to "Light-Emitting Diode" instead of just its abbreviation? You would think most readers would know how to pronounce the letters "LED". —Preceding unsigned comment added by 97.118.146.126 ( talk) 06:00, 26 December 2009 (UTC)
Urm, I new to this game, thought I'd do a quick edit to remove some vandalism. It's something to the order of "GLOBAL WARNING CAN ..." I went to remove it, however, and I can't find that text anywhere in the source for the page. From where is it coming? There are a number of occurrences of it. —Preceding unsigned comment added by 69.134.179.71 ( talk) 02:05, 11 February 2010 (UTC)
'noise diode' should redirect to here: http://en.wikipedia.org/wiki/Hardware_random_number_generator#Physical_phenomena_without_quantum-random_properties How do I setup a link and leave the displayed link text the same? (Add a title to a link)
Specifically, the part where it says "Avalanche noise generated from an avalanche diode, or Zener breakdown noise from a reverse-biased zener diode." is relevant. It doesn't even really need to be a diode. Any gate or resistor will experience some random noise. Even a spark gap oscillator has some random noise in it's output. What matters though is that the definition of a noise diode is included in that article. JWhiteheadcc ( talk) 18:59, 21 February 2010 (UTC)
Anvil being Cathode, post being Anode is not always true. The company I work for produces LED-boards showing prices at fuel stations. While the rest of the circuitry on our boards exactly stay the same every now and then our THT-workers have to place the LEDS in the opposite direction. (De- and Re-soldering isn't an option, so guess who..., as a hobbyist, is benefiting from mistakes made in the past. ;) 62.238.198.129 ( talk) 21:32, 15 March 2010 (UTC)
The section on Narrow band light sensors seems very long for something that has apparently never been used for anything practical - if it has this should perhaps be mentioned. Also the "journal entries" seem to contain very little encyclopedic information. Searching for "mims effect" and LED on google gives 15 hits, most of which leads back to copies of this section. I question whether most of this is notable.-- Thorseth ( talk) 20:50, 9 April 2010 (UTC)
The color table appears to lump all wavelengths from 500 to 570 nm as Green, and does not make any distinction with the between the traditional bright lime green LEDs and the newer Blue-Green traffic signal LEDs. Generally, Green is defined by the LED industry as 540-570 nm, while 500-540 nm is usually defined as Blue-Green. The standard wavelength for "green" traffic signals in most countries is 505 nm. However, I don't have any data on voltages, so I could use a little help. ANDROS1337 04:08, 20 April 2010 (UTC)
I removed that section for at least the following reasons:
I heard there are now LED contacts, can this be verified?-- Chris (クリス • フィッチ) ( talk) 13:57, 5 August 2010 (UTC)
I have a problem with downloading a 1.4MB image (220px-P-hus_Aveny.gif) over my mobile internet connection each time I visit this page. Can it be removed? 110.23.89.159 ( talk) 01:26, 18 September 2010 (UTC)
Anyone want to upload a pic of surface mount (device) led? —Preceding unsigned comment added by 115.70.80.179 ( talk) 23:43, 5 January 2011 (UTC)
A Google Books snippet out of "SAE Ground Vehicle Lighting Manual" says that LED luminous output can nearly double at -40°C. However, I don't like citing a snippet as a reference. -- Wtshymanski ( talk) 03:25, 15 April 2011 (UTC)
We want luminous efficacy in a light-emitting diode, not just efficiency. An IR LED that was 99% efficient would have zero efficacy as a visible light source. It is correct to speak of efficacy when describing visible light sources. -- Wtshymanski ( talk) 13:37, 13 April 2011 (UTC)
-- Alkhowarizmi ( talk) 10:51, 2 August 2011 (UTC)
It states in one of the graphs for the "diode curve" that the LED starts emitting light when the "on voltage" has been exceeded, and that the typical on voltage is 2 - 3 volts. This is not completely accurate, LEDS will start lighting up at forward voltages much lower than 2 - 3 volts, the 2 - 3 volts is the typical forward voltage with a typical current flow to allow it to emit light to a reasonably observable level. If an LED has a forward voltage of around 2V and a current flow of 20mA, it will light up even for around 10 micro-amps at 1.6V, though it would only be really observable at close proximity in a dark room. Veritas Blue ( talk) 06:04, 3 September 2011 (UTC)
Yeah, one of the pictures showing the parts of an LED has a messed up word. It says "die" and not dye. If someone can please fix the image and re-post it I would be very greatful. — Preceding unsigned comment added by 50.84.132.155 ( talk) 15:09, 28 October 2011 (UTC)
The section Light-emitting_diode#Energy_consumption compares a 40 Watt light bulb with a 13 Watt LED. Nowadays, a good 6 Watt LED can easily emit 600 Lumen. Of course, there are also still older, less efficient models on the market. Further, the argument that "in cold climates [...] more heating is needed" is a rather questionable argument as heating by electricity is comparably inefficient and during summer highly undesired. Overall the heating effect is so low that you couldn't sufficiently heat a room with a conventional amount of light bulbs anyway - and wouldn't want to as there are numerous more efficient methods. Especially as heating and lighting are not separately controllable this is rather an excuse against using modern technology than anything else. I've often seen slightly burnt areas around Halogen and conventional light bulbs. Last but not least, the heat of light bulbs is often a fire hazard. I've never even heard about anyone trying to use light bulbs for heating - excluding special purpose devices like lava lamps - before the EU announced to ban them and then it was usually an obvious expression of stubbornness. -- 93.130.51.11 ( talk) 13:10, 8 July 2011 (UTC)
On November 13th 2011, I created and uploaded a schematic showing the typical layout and polarity of a 3528 SMD LED. The image was removed on December 21st without much explanation given by Thorseth, who found "removed image of dubious information value" (his comment for the edit). I think polarity information of an SMD LED is not dubious (a reference was given to the handbook of a producer of SMD LEDS). Any arguments? Spidey71 ( talk) 22:27, 22 January 2012 (UTC)
My original edit to Light-emitting diode was reverted by User:Wtshymanski. I found the edit summary to be incorrect in its characterization of my source (I saw nothing in the source about a press release, and "not from a publicity department" would be a good thing rather than a reason to revert an edit). So I reverted the revert and was reverted again. The edit summary this time was clearer on the Wtshymanski's objection--the event wasn't important enough, which may have been justified--but it seemed to indicate Wtshymanski objected to the reliability of the source as well. The source was a reporter who had worked at the newspaper for many, many years, so I asked on Wtshymanski's talk page what made him the authority to deem this reporter an unreliable source. I confess that I violated WP:CIVIL in my wording, but I felt perfectly justified in my edit and Wtshymanski seemed unreasonable. Wtshymanski reiterated the lack of importance of the event here but indicated willingness to add the edit to Cree Inc.. I indicated a willingness to compromise and Wtshymanski blanked his/her talk page. But the edit summary for Wtshymanski's response to me was "Wikipedia is not for press releases". I don't see where I've done anything wrong, and Wtshymanski seemed happy to let me put the edit in Cree Inc..
So I didn't use a press release as a source (though the reporter might have), and the only justified objection to the edit seems to be the importance of the event. Vchimpanzee · talk · contributions · 20:36, 10 February 2012 (UTC)
There are LEDs now that produce entangled photon pairs, might want to add that... to wit: http://optics.org/article/42841 71.139.160.159 ( talk) 05:25, 8 May 2012 (UTC)
As they currently stand, these sections don't make sense. One cannot speak of advantages without agreeing on the reference. For instance, "efficiency" features both as an advantage and a disadvantage. Moreover, it is implicit in other bullets, such as "color". I see two ways to solve this: Either group these by topic; e.g. all efficiency related considerations could form one section. I did a first step in that direction by merging toxicity consideration into " § Safety and health". Another path would be to have a table that compares different light sources. That would provide a frame of reference for such considerations as efficiency, which would be much more useful for the reader than the current conflicting statements. — Sebastian 02:33, 18 February 2011 (UTC)
This digresses slightly off topic, but the "
§ Disadvantages" section needs a slight revision:
"* Light quality: Most cool- white LEDs have spectra that differ significantly from a black body radiator like the sun or an incandescent light."
The very next point in the section, Area light source:, links to an article on
lambertian distribution:
"The emission of a Lambertian radiator does not depend upon the amount of incident radiation, but rather from radiation originating in the emitting body itself. For example, if the sun were a Lambertian radiator, one would expect to see a constant brightness across the entire solar disc. The fact that the sun exhibits limb darkening in the visible region illustrates that it is not a Lambertian radiator. A black body is an example of a Lambertian radiator."
The link in the Light quality: section,
black body, clarifies further. Stars can be roughly modeled as black bodies, but are not.
I propose a simple revision:
"* Light quality: Most cool-
white LEDs have spectra that differ significantly from the sun or a
black body radiator like an incandescent light."
— Ptericles Ptericles ( talk) 20:56, 20 May 2012 (UTC)
The article states that the index of refraction of silicon is 4.24. I think that's wrong: While the index of refraction of silicon varies based on wavelength, I believe that a value of 3.55 is close to being correct. Perhaps the value of 4.24 was intended to refer to one of the many non-silicon LED combinations. (GaAs, GaAsP, GaAlAsP, etc.) Jamesdbell8 ( talk) 16:04, 14 July 2012 (UTC)
The Phosphor-based LEDs section of the article has this sentence: "The efficiency of a typical YAG-based yellow phosphor converted white LED ranges from 3 to 5 times the efficiency of the original blue LED." I don't see how this could possibly be true, The phosphor coated LEDs loose energy from the Stokes shift, they should be less efficient. Is this statement meant to compare the use of phosphor vs a filter? Does it take into consideration how sensitive the eye is too different frequencies of light? Wingedsubmariner ( talk) 01:40, 20 July 2012 (UTC)
I read that Baltimore and other cities are replacing existing light sources in street lamps with LEDs. Is this text still accurate: "LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output." Thanks -- Jo3sampl ( talk) 20:19, 17 August 2012 (UTC)
No mention at all about this issue. The direct/inverse resistivity is neglectibly small/huge but when groupping lots of LEDs in paralel and/or serial circuits resistivity can grow/drop to significant values. — Preceding unsigned comment added by Srelu ( talk • contribs) 03:50, 29 August 2012 (UTC)
What happens when an LED fails or burns out does it open or short? Just Curious — Preceding unsigned comment added by 209.165.141.254 ( talk) 21:04, 20 April 2012 (UTC)
I would like to simply know which of the available lights offer 5600K, so they can be mixed with available sunlight. Probably the ones that approximate the blue part of the spectrum, but it seems unclear. — Preceding unsigned comment added by 68.175.88.187 ( talk) 14:28, 28 December 2012 (UTC)
Today, my little brother's friend was pulling up to the house, he was parked in the driveway, maybe calling my brother, but we saw him on the camera. On the camera, his LED headlights looked like they were flashing. I thought it was a cop car or something, but my older brother came and saw and he said, no it's our little brother's friend. He tells me that this happens sometimes on cameras with LED lights on cars. I immediately suspected that if there is such a phenomenon, then it has something to do with the LEDs pulsing vs. camera's capture-frame-rate. With a little research, I found that this is a normal thing that happens due to pulse-width modulation. This was a surprise to me because I hadn't heard of LEDs ever being pulsed - I thought they were always just on or off. I don't have any references, I'm not some kind of visual/camera expert, but this all should be pretty obvious to anyone even slightly versed in physics/science. EdwinAmi ( talk) 22:20, 12 July 2013 (UTC)EdwinAmi So anyway, I'm going to be noting this phenomenon next to the mention of pulse-width-modulation in "Advantages:dimming" — Preceding unsigned comment added by EdwinAmi ( talk • contribs) 22:08, 12 July 2013 (UTC)
I understand the desire to credit poor Oleg Losev (who is said to have died at 38, during the terrible Siege of Leningrad).
However, in the absence of better information I would argue against crediting Losev as an "inventor" of the LED. Losev may have been a discoverer, but not an inventor. (I don't know whether the silicon carbide LED that he developed relied on the same physical principles; perhaps another Editor can comment on whether it was a diffused junction or a heterojunction device; or whether as a point-contact device it was based on different, if related, physics. Be that as it may…) Unless Losev's work can be shown to have indirectly given rise to adoption of LEDs in the marketplace or as a necessary element of a product, I can't accept Losev as inventor.
In other words, if his work occurred in isolation, if his ideas did not strongly influence Holonyak or others whose contributions did lead to adoption, or if his work was on a different type of device altogether, then Losev should not be listed as inventor on Wikipedia. On the other hand, I have no difficulty identifying Losev's work as that of a discoverer of electroluminescence. However, an electroluminescent device is not an LED - which must exhibit a reasonable efficiency.
Incidentally, I am well-aware that good work was done in the U.S.S.R. during the pre-WW-II era. I personally studied the papers relating to the invention of the photomultiplier; which invention was claimed by some to have been effected by one Leonid Kubetsky and then was viewed by Vladimir Zworykin during a 1933 trip to the U.S.S.R. (his native land). In that case, Kubetsky would have been inventor since his work led to the adoption of the photomultiplier. However in this case I am not aware that there is any "straight line" that can be drawn between the Losev work and that of Holonyak. If I am not correct, I welcome an authoritative response demonstrating the straight-line connection. — Preceding unsigned comment added by Jabeles ( talk • contribs) 23:26, 6 March 2013 (UTC)
I tried to edit it to show Losev as discoverer, and the other 2 inventors, but the wikicode is beyond me Tabby ( talk) 18:03, 28 August 2013 (UTC)
Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • Sbmeirow • Talk • 23:34, 15 December 2013 (UTC)
I removed the following source: Rensselaer Researchers Identify Cause of LED “Efficiency Droop”, Rensselaer, Mary L. Martialay, 30 July 2013 because the it appears to be a self-published article by a publicist for the institution doing the reported research. The publication lists no sources except for the study that discovered a cause of the effect but the statements the source is used to support are the date of the effect's discovery and the magnitude of the effect. I had originally removed the content as well but have since replaced it with a request for (reliable) citations. Joja lozzo 03:49, 17 December 2013 (UTC)
The derivation of radiant efficiency in section Led#Efficiency_and_operational_parameters reads a little bit like original research. Its not necessarily a simple task to do the spectral calculations with the data from the datasheet and a simple divide and multiply method could give wrong results for the broad sources.-- Thorseth ( talk) 12:21, 31 December 2013 (UTC)
Just thought I'd upload this here, in case someone wants to use it. It's a close-up picture taken with my digital microscope of the actual PN junction and the bondwire leading over to the cathode.
/-\urelius ♠ |)ecimus What'sup, dog? 05:24, 2 February 2014 (UTC)
Light can be used to transmit broadband data, which is already implemented in IrDA standards using infrared LEDs. Because LEDs can cycle on and off millions of times per second, they can be wireless transmitters and access points for data transport.[144] Lasers can also be modulated in this manner.
is using light to transmit data referred to as 'smart lighting'? Jonpatterns ( talk) 16:04, 10 February 2014 (UTC)
I don't believe that it is. I have done a lot of reading on Li-Fi and don't think it has been referred to as that.-- Wyn.junior ( talk) 00:16, 22 February 2014 (UTC)
While it’s well known that natural light is preferable to artificial for a variety of reasons (vitamin-D production, prevention of seasonal affective disorder), new research published in the Journal of Environmental Management shows that nighttime exposure to certain types of artificial light has an even darker side than previously understood. In particular, it suppresses the body’s ability to make melatonin, the hormone that helps regulate sleep and is celebrated for its antioxidant, mood-enhancing and cancer-fighting properties.
The main culprit is artificial light that contains the highest percentage of blue light in its full-spectrum mix. One of the top offenders in this category is the light-emitting diode (LED) bulb, which suppresses melatonin at rates five times greater than bulbs that give off warmer “orange-yellow” light, like incandescents.
LEDs have grown increasingly popular as an environmentally friendly alternative to fluorescent or incandescent bulbs. They contain no mercury, last more than 50,000 hours and use up to 80 percent less energy than traditional incandescent bulbs.
Despite these benefits, scientists encourage consumers to choose bulbs situationally, avoiding LEDs at night. Melatonin-suppressing light is “dangerous only if we expose ourselves to it during the hours when we should be in the dark, and if the exposure is sufficiently intense or long,” says physicist Fabio Falchi, of the Light Pollution Science and Technology Institute in Italy. He advises people to rely more on incandescent light after dark, especially in the bedroom. http://experiencelife.com/newsflashes/the-health-dangers-of-led-lights/ http://www.ledsmagazine.com/articles/2010/11/light-and-human-health-led-risks-highlighted.html — Preceding unsigned comment added by Nmakh ( talk • contribs) 06:03, 23 April 2014 (UTC)
LED street lamps are attracting less insects than incandescent ones. This is because they don't emit UV wavelengths. UV is the main reason why insects are attracted by lamps. (Insect traps often work with UV lamps.) The advantage is not only less insect deaths, which is certainly good for the eco system and all animals that prey on insects, it also means that LED street lamps are less polluted by dead insects and spider webs. Which is good for us because the dirt on the lamps absorbs light.--TeakHoken 213.150.232.3 ( talk) 13:34, 9 September 2014 (UTC)
I wrote this section and I believe it should be included:
LEDs can be used as microphones and can transmit audio over 300 meters away. Newark Liberty International Airport has 171 light fixtures being used as listening devices for security. The lights were manufactured by Sensity Systems and the company says that the potential of LEDs to collect data on the people is nearly boundless.
[3]
The user who deleted it said that any type of lighting device could be used as an audio listening device.-- Wyn.junior ( talk) 02:20, 22 February 2014 (UTC)
At the very least, a simple mention on the LED article of Newark Liberty International Airport's security system still seems appropriate.-- Wyn.junior ( talk) 03:55, 22 February 2014 (UTC)
It might also be appropriate to note that LEDs are not very microphonic and that these devices can be ambedded in any electronic device (if the info can be referenced). Both of those notes are very significant and appropriate.-- Wyn.junior ( talk) 03:57, 22 February 2014 (UTC)
The increased lifespan of LED's in appliances should be mentioned, along with some sidelines on it. For example, TV's are now made with LED's and manufacturers claim a huge increase in life span due to the longer durability of the LED over the cathode ray tube (CRT). Appearantly though, this is all but a sales speech since they now manufacture the other components in the TV to break down much quicker. Appearantly, a comparable TV then and now is about 66% less durable, so I doubt that if you compare an old -well manufactured CRT TV- with a new LED TV, the LED TV will actually even last as long as the old CRT. See Planned_obsolescence
Mention at LED#Lifetime_and_failure KVDP ( talk) 08:50, 23 July 2014 (UTC)
There are too many single-sentence paragraphs and one-paragraph sections in this article. See WP:LAYOUT. Headings are for broad sections of text, not to separate each paragraph. — Designate ( talk) 17:37, 11 October 2014 (UTC)
A light emitting diode (LED) is essentially a PN junction opto-semiconductor that emits a monochromatic (single color) light when operated in a forward biased direction. LEDs convert electrical energy into light energy. They are frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is closed or not.
About LEDs (1/2) The most important part of a light emitting diode (LED) is the semi-conductor chip located in the center of the bulb as shown at the right. The chip has two regions separated by a junction. The p region is dominated by positive electric charges, and the n region is dominated by negative electric charges. The junction acts as a barrier to the flow of electrons between the p and the n regions. Only when sufficient voltage is applied to the semi-conductor chip, can the current flow, and the electrons cross the junction into the p region. 12:34, 26 October 2014 (UTC) 117.199.213.98 ( talk)
Wow, great article.Much thanks again. Keep writing. — Preceding unsigned comment added by 188.26.155.102 ( talk) 16:08, 27 November 2014 (UTC)
"Until 1968, ...LEDs were extremely costly, in the order of US$200 per unit"
Prices were dropping in early 1967:
"Allied Radio's catalog No. 670 offers a GE type LED 9 light emitting diode for only $12"
Popular Electronics, January, 1967, pg 77
http://www.americanradiohistory.com/Popular-Electronics-Guide.htm
PRR ( talk) 04:20, 15 December 2014 (UTC)
UBV
was invoked but never defined (see the
help page).![]() | This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
I like the "Colors and materials" section. But some of the numbers are just a little different than what I see elsewhere.
This article implies that green LEDs require "2.18 < ΔV < 4.0". When I look through supplier catalogs [1], I see many green LEDs rated at "1.9 V". So are those "1.9 V green LEDs" really more of a yellowish green, or are the numbers in this article a bit off, or am I misinterpreting something?
Should I pick a LED manufacturer at random and use their part catalog as a reference to update the voltages in that table? -- 68.0.124.33 ( talk) 23:16, 5 August 2009 (UTC)
How is this [1] or this [2] considered an array and not a single diode? In this datasheet [3] it even says "Over 2,750 lumens from a single chip" and again this one [4] says "Over 2,200 lumens from a single chip" If Haitz's Law is expressed in terms of lumens per package then it hardly seems justifiable to differentiate in this section alone. We don't say a quad-core CPU is faster (but only because there is more than one core) or this generation of CPU is faster (but only because it has more transistors) and thus we shouldn't say a quad-die LED is brighter (but only because some excuse here). There are many ways to increase the lumen output of an LED and increasing the substrate surface area is one of them. Are we going to be calculating that surface area and arbitrarily creating new categories now because one manufacturer encased 3 die in a single package? What difference does it make if one die is larger or if you are using 4 smaller die? If you are going to qualify it this way you might as well qualify statements for the whole article by placing that verbiage at the top. Don't forget the RGB white section too as those are also single-package arrays. I agree it should be mentioned that some LEDs come in a single-package array but I would never say I have anything other than a single LED regardless of the die count or substrate surface area. Thepaan ( talk) 00:25, 23 October 2009 (UTC)
References
I notice that Losev is still credited as the inventor. This was discussed here previously, and it appeared some rearrangement was anticipated. Also there doesn't seem to be any source cited for this info. (Never heard of him myself)
The bit about a bipolar transistor emitting light under certain condition, ie. cutting the case open, biasing etc. has been removed. This was also mentioned and it appeared it was staying, but 213.162.105.199 recently edited it out saying "they tried it and it didn't work". I have also heard that this is possible to do. But OR to remove something is surely as bad /worse than trying to publish your own OR. There may be a place for this info (LED trivia?). The fact that they tried it (once or more?) surely isnt right in Wikipedia.
This is a very detailed article, and even though I worked as a Radio 'Technical' Officer, I found the intro a bit too detailed. Now for 'conventional' current versus 'true' current flow!. [Kidding] ;-) -- 220.101.28.25 ( talk) 17:11, 24 October 2009 (UTC)
This graph is meaningless drivel. The only purpose I can see for it is to promote the agenda that "LED's are better". Why do I say this?
-- Juckto ( talk) 20:47, 19 November 2009 (UTC)
It is "very important" to avoid light pollution, is a biased statement that doesn't belong in the LED article. The movement that is against light, has no scientific proof to back up their crazyness. —Preceding unsigned comment added by 93.182.185.88 ( talk) 14:25, 4 December 2009 (UTC)
Why the hell doesn't the pronunciation guide apply to "Light-Emitting Diode" instead of just its abbreviation? You would think most readers would know how to pronounce the letters "LED". —Preceding unsigned comment added by 97.118.146.126 ( talk) 06:00, 26 December 2009 (UTC)
Urm, I new to this game, thought I'd do a quick edit to remove some vandalism. It's something to the order of "GLOBAL WARNING CAN ..." I went to remove it, however, and I can't find that text anywhere in the source for the page. From where is it coming? There are a number of occurrences of it. —Preceding unsigned comment added by 69.134.179.71 ( talk) 02:05, 11 February 2010 (UTC)
'noise diode' should redirect to here: http://en.wikipedia.org/wiki/Hardware_random_number_generator#Physical_phenomena_without_quantum-random_properties How do I setup a link and leave the displayed link text the same? (Add a title to a link)
Specifically, the part where it says "Avalanche noise generated from an avalanche diode, or Zener breakdown noise from a reverse-biased zener diode." is relevant. It doesn't even really need to be a diode. Any gate or resistor will experience some random noise. Even a spark gap oscillator has some random noise in it's output. What matters though is that the definition of a noise diode is included in that article. JWhiteheadcc ( talk) 18:59, 21 February 2010 (UTC)
Anvil being Cathode, post being Anode is not always true. The company I work for produces LED-boards showing prices at fuel stations. While the rest of the circuitry on our boards exactly stay the same every now and then our THT-workers have to place the LEDS in the opposite direction. (De- and Re-soldering isn't an option, so guess who..., as a hobbyist, is benefiting from mistakes made in the past. ;) 62.238.198.129 ( talk) 21:32, 15 March 2010 (UTC)
The section on Narrow band light sensors seems very long for something that has apparently never been used for anything practical - if it has this should perhaps be mentioned. Also the "journal entries" seem to contain very little encyclopedic information. Searching for "mims effect" and LED on google gives 15 hits, most of which leads back to copies of this section. I question whether most of this is notable.-- Thorseth ( talk) 20:50, 9 April 2010 (UTC)
The color table appears to lump all wavelengths from 500 to 570 nm as Green, and does not make any distinction with the between the traditional bright lime green LEDs and the newer Blue-Green traffic signal LEDs. Generally, Green is defined by the LED industry as 540-570 nm, while 500-540 nm is usually defined as Blue-Green. The standard wavelength for "green" traffic signals in most countries is 505 nm. However, I don't have any data on voltages, so I could use a little help. ANDROS1337 04:08, 20 April 2010 (UTC)
I removed that section for at least the following reasons:
I heard there are now LED contacts, can this be verified?-- Chris (クリス • フィッチ) ( talk) 13:57, 5 August 2010 (UTC)
I have a problem with downloading a 1.4MB image (220px-P-hus_Aveny.gif) over my mobile internet connection each time I visit this page. Can it be removed? 110.23.89.159 ( talk) 01:26, 18 September 2010 (UTC)
Anyone want to upload a pic of surface mount (device) led? —Preceding unsigned comment added by 115.70.80.179 ( talk) 23:43, 5 January 2011 (UTC)
A Google Books snippet out of "SAE Ground Vehicle Lighting Manual" says that LED luminous output can nearly double at -40°C. However, I don't like citing a snippet as a reference. -- Wtshymanski ( talk) 03:25, 15 April 2011 (UTC)
We want luminous efficacy in a light-emitting diode, not just efficiency. An IR LED that was 99% efficient would have zero efficacy as a visible light source. It is correct to speak of efficacy when describing visible light sources. -- Wtshymanski ( talk) 13:37, 13 April 2011 (UTC)
-- Alkhowarizmi ( talk) 10:51, 2 August 2011 (UTC)
It states in one of the graphs for the "diode curve" that the LED starts emitting light when the "on voltage" has been exceeded, and that the typical on voltage is 2 - 3 volts. This is not completely accurate, LEDS will start lighting up at forward voltages much lower than 2 - 3 volts, the 2 - 3 volts is the typical forward voltage with a typical current flow to allow it to emit light to a reasonably observable level. If an LED has a forward voltage of around 2V and a current flow of 20mA, it will light up even for around 10 micro-amps at 1.6V, though it would only be really observable at close proximity in a dark room. Veritas Blue ( talk) 06:04, 3 September 2011 (UTC)
Yeah, one of the pictures showing the parts of an LED has a messed up word. It says "die" and not dye. If someone can please fix the image and re-post it I would be very greatful. — Preceding unsigned comment added by 50.84.132.155 ( talk) 15:09, 28 October 2011 (UTC)
The section Light-emitting_diode#Energy_consumption compares a 40 Watt light bulb with a 13 Watt LED. Nowadays, a good 6 Watt LED can easily emit 600 Lumen. Of course, there are also still older, less efficient models on the market. Further, the argument that "in cold climates [...] more heating is needed" is a rather questionable argument as heating by electricity is comparably inefficient and during summer highly undesired. Overall the heating effect is so low that you couldn't sufficiently heat a room with a conventional amount of light bulbs anyway - and wouldn't want to as there are numerous more efficient methods. Especially as heating and lighting are not separately controllable this is rather an excuse against using modern technology than anything else. I've often seen slightly burnt areas around Halogen and conventional light bulbs. Last but not least, the heat of light bulbs is often a fire hazard. I've never even heard about anyone trying to use light bulbs for heating - excluding special purpose devices like lava lamps - before the EU announced to ban them and then it was usually an obvious expression of stubbornness. -- 93.130.51.11 ( talk) 13:10, 8 July 2011 (UTC)
On November 13th 2011, I created and uploaded a schematic showing the typical layout and polarity of a 3528 SMD LED. The image was removed on December 21st without much explanation given by Thorseth, who found "removed image of dubious information value" (his comment for the edit). I think polarity information of an SMD LED is not dubious (a reference was given to the handbook of a producer of SMD LEDS). Any arguments? Spidey71 ( talk) 22:27, 22 January 2012 (UTC)
My original edit to Light-emitting diode was reverted by User:Wtshymanski. I found the edit summary to be incorrect in its characterization of my source (I saw nothing in the source about a press release, and "not from a publicity department" would be a good thing rather than a reason to revert an edit). So I reverted the revert and was reverted again. The edit summary this time was clearer on the Wtshymanski's objection--the event wasn't important enough, which may have been justified--but it seemed to indicate Wtshymanski objected to the reliability of the source as well. The source was a reporter who had worked at the newspaper for many, many years, so I asked on Wtshymanski's talk page what made him the authority to deem this reporter an unreliable source. I confess that I violated WP:CIVIL in my wording, but I felt perfectly justified in my edit and Wtshymanski seemed unreasonable. Wtshymanski reiterated the lack of importance of the event here but indicated willingness to add the edit to Cree Inc.. I indicated a willingness to compromise and Wtshymanski blanked his/her talk page. But the edit summary for Wtshymanski's response to me was "Wikipedia is not for press releases". I don't see where I've done anything wrong, and Wtshymanski seemed happy to let me put the edit in Cree Inc..
So I didn't use a press release as a source (though the reporter might have), and the only justified objection to the edit seems to be the importance of the event. Vchimpanzee · talk · contributions · 20:36, 10 February 2012 (UTC)
There are LEDs now that produce entangled photon pairs, might want to add that... to wit: http://optics.org/article/42841 71.139.160.159 ( talk) 05:25, 8 May 2012 (UTC)
As they currently stand, these sections don't make sense. One cannot speak of advantages without agreeing on the reference. For instance, "efficiency" features both as an advantage and a disadvantage. Moreover, it is implicit in other bullets, such as "color". I see two ways to solve this: Either group these by topic; e.g. all efficiency related considerations could form one section. I did a first step in that direction by merging toxicity consideration into " § Safety and health". Another path would be to have a table that compares different light sources. That would provide a frame of reference for such considerations as efficiency, which would be much more useful for the reader than the current conflicting statements. — Sebastian 02:33, 18 February 2011 (UTC)
This digresses slightly off topic, but the "
§ Disadvantages" section needs a slight revision:
"* Light quality: Most cool- white LEDs have spectra that differ significantly from a black body radiator like the sun or an incandescent light."
The very next point in the section, Area light source:, links to an article on
lambertian distribution:
"The emission of a Lambertian radiator does not depend upon the amount of incident radiation, but rather from radiation originating in the emitting body itself. For example, if the sun were a Lambertian radiator, one would expect to see a constant brightness across the entire solar disc. The fact that the sun exhibits limb darkening in the visible region illustrates that it is not a Lambertian radiator. A black body is an example of a Lambertian radiator."
The link in the Light quality: section,
black body, clarifies further. Stars can be roughly modeled as black bodies, but are not.
I propose a simple revision:
"* Light quality: Most cool-
white LEDs have spectra that differ significantly from the sun or a
black body radiator like an incandescent light."
— Ptericles Ptericles ( talk) 20:56, 20 May 2012 (UTC)
The article states that the index of refraction of silicon is 4.24. I think that's wrong: While the index of refraction of silicon varies based on wavelength, I believe that a value of 3.55 is close to being correct. Perhaps the value of 4.24 was intended to refer to one of the many non-silicon LED combinations. (GaAs, GaAsP, GaAlAsP, etc.) Jamesdbell8 ( talk) 16:04, 14 July 2012 (UTC)
The Phosphor-based LEDs section of the article has this sentence: "The efficiency of a typical YAG-based yellow phosphor converted white LED ranges from 3 to 5 times the efficiency of the original blue LED." I don't see how this could possibly be true, The phosphor coated LEDs loose energy from the Stokes shift, they should be less efficient. Is this statement meant to compare the use of phosphor vs a filter? Does it take into consideration how sensitive the eye is too different frequencies of light? Wingedsubmariner ( talk) 01:40, 20 July 2012 (UTC)
I read that Baltimore and other cities are replacing existing light sources in street lamps with LEDs. Is this text still accurate: "LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output." Thanks -- Jo3sampl ( talk) 20:19, 17 August 2012 (UTC)
No mention at all about this issue. The direct/inverse resistivity is neglectibly small/huge but when groupping lots of LEDs in paralel and/or serial circuits resistivity can grow/drop to significant values. — Preceding unsigned comment added by Srelu ( talk • contribs) 03:50, 29 August 2012 (UTC)
What happens when an LED fails or burns out does it open or short? Just Curious — Preceding unsigned comment added by 209.165.141.254 ( talk) 21:04, 20 April 2012 (UTC)
I would like to simply know which of the available lights offer 5600K, so they can be mixed with available sunlight. Probably the ones that approximate the blue part of the spectrum, but it seems unclear. — Preceding unsigned comment added by 68.175.88.187 ( talk) 14:28, 28 December 2012 (UTC)
Today, my little brother's friend was pulling up to the house, he was parked in the driveway, maybe calling my brother, but we saw him on the camera. On the camera, his LED headlights looked like they were flashing. I thought it was a cop car or something, but my older brother came and saw and he said, no it's our little brother's friend. He tells me that this happens sometimes on cameras with LED lights on cars. I immediately suspected that if there is such a phenomenon, then it has something to do with the LEDs pulsing vs. camera's capture-frame-rate. With a little research, I found that this is a normal thing that happens due to pulse-width modulation. This was a surprise to me because I hadn't heard of LEDs ever being pulsed - I thought they were always just on or off. I don't have any references, I'm not some kind of visual/camera expert, but this all should be pretty obvious to anyone even slightly versed in physics/science. EdwinAmi ( talk) 22:20, 12 July 2013 (UTC)EdwinAmi So anyway, I'm going to be noting this phenomenon next to the mention of pulse-width-modulation in "Advantages:dimming" — Preceding unsigned comment added by EdwinAmi ( talk • contribs) 22:08, 12 July 2013 (UTC)
I understand the desire to credit poor Oleg Losev (who is said to have died at 38, during the terrible Siege of Leningrad).
However, in the absence of better information I would argue against crediting Losev as an "inventor" of the LED. Losev may have been a discoverer, but not an inventor. (I don't know whether the silicon carbide LED that he developed relied on the same physical principles; perhaps another Editor can comment on whether it was a diffused junction or a heterojunction device; or whether as a point-contact device it was based on different, if related, physics. Be that as it may…) Unless Losev's work can be shown to have indirectly given rise to adoption of LEDs in the marketplace or as a necessary element of a product, I can't accept Losev as inventor.
In other words, if his work occurred in isolation, if his ideas did not strongly influence Holonyak or others whose contributions did lead to adoption, or if his work was on a different type of device altogether, then Losev should not be listed as inventor on Wikipedia. On the other hand, I have no difficulty identifying Losev's work as that of a discoverer of electroluminescence. However, an electroluminescent device is not an LED - which must exhibit a reasonable efficiency.
Incidentally, I am well-aware that good work was done in the U.S.S.R. during the pre-WW-II era. I personally studied the papers relating to the invention of the photomultiplier; which invention was claimed by some to have been effected by one Leonid Kubetsky and then was viewed by Vladimir Zworykin during a 1933 trip to the U.S.S.R. (his native land). In that case, Kubetsky would have been inventor since his work led to the adoption of the photomultiplier. However in this case I am not aware that there is any "straight line" that can be drawn between the Losev work and that of Holonyak. If I am not correct, I welcome an authoritative response demonstrating the straight-line connection. — Preceding unsigned comment added by Jabeles ( talk • contribs) 23:26, 6 March 2013 (UTC)
I tried to edit it to show Losev as discoverer, and the other 2 inventors, but the wikicode is beyond me Tabby ( talk) 18:03, 28 August 2013 (UTC)
Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • Sbmeirow • Talk • 23:34, 15 December 2013 (UTC)
I removed the following source: Rensselaer Researchers Identify Cause of LED “Efficiency Droop”, Rensselaer, Mary L. Martialay, 30 July 2013 because the it appears to be a self-published article by a publicist for the institution doing the reported research. The publication lists no sources except for the study that discovered a cause of the effect but the statements the source is used to support are the date of the effect's discovery and the magnitude of the effect. I had originally removed the content as well but have since replaced it with a request for (reliable) citations. Joja lozzo 03:49, 17 December 2013 (UTC)
The derivation of radiant efficiency in section Led#Efficiency_and_operational_parameters reads a little bit like original research. Its not necessarily a simple task to do the spectral calculations with the data from the datasheet and a simple divide and multiply method could give wrong results for the broad sources.-- Thorseth ( talk) 12:21, 31 December 2013 (UTC)
Just thought I'd upload this here, in case someone wants to use it. It's a close-up picture taken with my digital microscope of the actual PN junction and the bondwire leading over to the cathode.
/-\urelius ♠ |)ecimus What'sup, dog? 05:24, 2 February 2014 (UTC)
Light can be used to transmit broadband data, which is already implemented in IrDA standards using infrared LEDs. Because LEDs can cycle on and off millions of times per second, they can be wireless transmitters and access points for data transport.[144] Lasers can also be modulated in this manner.
is using light to transmit data referred to as 'smart lighting'? Jonpatterns ( talk) 16:04, 10 February 2014 (UTC)
I don't believe that it is. I have done a lot of reading on Li-Fi and don't think it has been referred to as that.-- Wyn.junior ( talk) 00:16, 22 February 2014 (UTC)
While it’s well known that natural light is preferable to artificial for a variety of reasons (vitamin-D production, prevention of seasonal affective disorder), new research published in the Journal of Environmental Management shows that nighttime exposure to certain types of artificial light has an even darker side than previously understood. In particular, it suppresses the body’s ability to make melatonin, the hormone that helps regulate sleep and is celebrated for its antioxidant, mood-enhancing and cancer-fighting properties.
The main culprit is artificial light that contains the highest percentage of blue light in its full-spectrum mix. One of the top offenders in this category is the light-emitting diode (LED) bulb, which suppresses melatonin at rates five times greater than bulbs that give off warmer “orange-yellow” light, like incandescents.
LEDs have grown increasingly popular as an environmentally friendly alternative to fluorescent or incandescent bulbs. They contain no mercury, last more than 50,000 hours and use up to 80 percent less energy than traditional incandescent bulbs.
Despite these benefits, scientists encourage consumers to choose bulbs situationally, avoiding LEDs at night. Melatonin-suppressing light is “dangerous only if we expose ourselves to it during the hours when we should be in the dark, and if the exposure is sufficiently intense or long,” says physicist Fabio Falchi, of the Light Pollution Science and Technology Institute in Italy. He advises people to rely more on incandescent light after dark, especially in the bedroom. http://experiencelife.com/newsflashes/the-health-dangers-of-led-lights/ http://www.ledsmagazine.com/articles/2010/11/light-and-human-health-led-risks-highlighted.html — Preceding unsigned comment added by Nmakh ( talk • contribs) 06:03, 23 April 2014 (UTC)
LED street lamps are attracting less insects than incandescent ones. This is because they don't emit UV wavelengths. UV is the main reason why insects are attracted by lamps. (Insect traps often work with UV lamps.) The advantage is not only less insect deaths, which is certainly good for the eco system and all animals that prey on insects, it also means that LED street lamps are less polluted by dead insects and spider webs. Which is good for us because the dirt on the lamps absorbs light.--TeakHoken 213.150.232.3 ( talk) 13:34, 9 September 2014 (UTC)
I wrote this section and I believe it should be included:
LEDs can be used as microphones and can transmit audio over 300 meters away. Newark Liberty International Airport has 171 light fixtures being used as listening devices for security. The lights were manufactured by Sensity Systems and the company says that the potential of LEDs to collect data on the people is nearly boundless.
[3]
The user who deleted it said that any type of lighting device could be used as an audio listening device.-- Wyn.junior ( talk) 02:20, 22 February 2014 (UTC)
At the very least, a simple mention on the LED article of Newark Liberty International Airport's security system still seems appropriate.-- Wyn.junior ( talk) 03:55, 22 February 2014 (UTC)
It might also be appropriate to note that LEDs are not very microphonic and that these devices can be ambedded in any electronic device (if the info can be referenced). Both of those notes are very significant and appropriate.-- Wyn.junior ( talk) 03:57, 22 February 2014 (UTC)
The increased lifespan of LED's in appliances should be mentioned, along with some sidelines on it. For example, TV's are now made with LED's and manufacturers claim a huge increase in life span due to the longer durability of the LED over the cathode ray tube (CRT). Appearantly though, this is all but a sales speech since they now manufacture the other components in the TV to break down much quicker. Appearantly, a comparable TV then and now is about 66% less durable, so I doubt that if you compare an old -well manufactured CRT TV- with a new LED TV, the LED TV will actually even last as long as the old CRT. See Planned_obsolescence
Mention at LED#Lifetime_and_failure KVDP ( talk) 08:50, 23 July 2014 (UTC)
There are too many single-sentence paragraphs and one-paragraph sections in this article. See WP:LAYOUT. Headings are for broad sections of text, not to separate each paragraph. — Designate ( talk) 17:37, 11 October 2014 (UTC)
A light emitting diode (LED) is essentially a PN junction opto-semiconductor that emits a monochromatic (single color) light when operated in a forward biased direction. LEDs convert electrical energy into light energy. They are frequently used as "pilot" lights in electronic appliances to indicate whether the circuit is closed or not.
About LEDs (1/2) The most important part of a light emitting diode (LED) is the semi-conductor chip located in the center of the bulb as shown at the right. The chip has two regions separated by a junction. The p region is dominated by positive electric charges, and the n region is dominated by negative electric charges. The junction acts as a barrier to the flow of electrons between the p and the n regions. Only when sufficient voltage is applied to the semi-conductor chip, can the current flow, and the electrons cross the junction into the p region. 12:34, 26 October 2014 (UTC) 117.199.213.98 ( talk)
Wow, great article.Much thanks again. Keep writing. — Preceding unsigned comment added by 188.26.155.102 ( talk) 16:08, 27 November 2014 (UTC)
"Until 1968, ...LEDs were extremely costly, in the order of US$200 per unit"
Prices were dropping in early 1967:
"Allied Radio's catalog No. 670 offers a GE type LED 9 light emitting diode for only $12"
Popular Electronics, January, 1967, pg 77
http://www.americanradiohistory.com/Popular-Electronics-Guide.htm
PRR ( talk) 04:20, 15 December 2014 (UTC)
UBV
was invoked but never defined (see the
help page).