Talk:Light-emitting diode

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Flashing when seen on camera[edit]

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 (talkcontribs) 22:08, 12 July 2013 (UTC)

A/an LED[edit]

Since I started watching this page 2-3 months ago, I've noticed that several different people have mistakenly changed "an LED" to "a LED", presumably mispronouncing the name. I was just about to insert an HTML comment near the first mention of "an LED" noting its correct usage, but since it appears many times throughout the considerable-length article that's unlikely to be effective. Instead, I propose we create Template:Editnotices/Page/Light-emitting diode (i.e. an edit notice which will appear when editing the article) with a brief but fairly visible note explaining why "an LED" is correct. Any thoughts on this? GiftigerWunsch [TALK] 22:52, 26 October 2010 (UTC)

Why does everyone on this talk page seem to be unable to understand the fact that "LED" is very commonly pronounced as "led", in the same manner that NASA, NATO and ASAP are pronounced as words rather than acronyms? "Scuba", "laser" and "radar" all originated from acronyms. I'm not directing this at anyone, I'm just saying, it really doesn't matter. Sorry to rant, but let me respond to the matter at hand: I don't thing Giftiger's suggestion is necessary. Why? Because people can't read IPA pronunciations (another thing Wikipedians seem to have a hard time grasping :P) I'm just going to include a correct pronunciation that normal people can understand: "L-E-D". Swarm X 11:54, 4 December 2010 (UTC)
No. No it's not pronounced "led" (added to my comment). GiftigerWunsch [TALK] 11:59, 4 December 2010 (UTC)
No what's not? Swarm X 14:25, 4 December 2010 (UTC)
Oh, it's not pronounced "led". While you're correct on that count and I'm well aware of the fact that doesn't change anything of what I said. If my response to your actual section was clouded by my ranting, let me clarify:
  • Many people pronounce "LED" as "led" (as is common with acronyms). Though the article contains the correct pronunciation, it's in IPA, which few know how to read, therefore, they continue editing the article thinking "led" is the correct pronunciation. A simple solution to this problem would be to add a pronunciation that people actually know how to read (!). Hence me doing so. Problem solved? We'll see. Swarm X 01:01, 5 December 2010 (UTC)
While you have a point about the IPA pronounciation, I'm not convinced this'll make a difference to the a/an thing. It's only an intermittent issue though so it's not a huge problem. GiftigerWunsch [TALK] 01:04, 5 December 2010 (UTC)
I don't really think people believe "a L" to be correct, as opposed "an L". I'm under the impression that a large part of this happens because of people who think "a 'led'" is the correct pronunciation, rather than "an L-E-D" (which is technically correct). Swarm X 02:08, 5 December 2010 (UTC)

WHAT? Does anyone here even know basic english??? The prefix "an" is ONLY used when the proceeding word starts with a vowel. Some example are: an apple NOT a apple, an orange NOT a orange, a car NOT an car, a led NOT an led. If it starts with A,E,I,O,U, then you use "an", otherwise it a prefixed with just "a". The correct usage of l.e.d (spelling out the letters if you desire to say it that way) or led (say: lead (rythming with head, bed, said, etc.) are the correct usage terms.

It is NEVER "an LED". — Preceding unsigned comment added by (talkcontribs)

You use an if the pronounciation starts with a vowel sound. LED is pronounced "el ee dee", so it is an LED, and not "a LED". GiftigerWunsch [TALK] 00:01, 6 January 2011 (UTC)
Note also that LED is never pronounced as a word like "lead", it's spoken as its individual letters. GiftigerWunsch [TALK] 00:04, 6 January 2011 (UTC)
'Does anyone here even know basic english???' 'The prefix "an" is ONLY used when the proceeding word starts with a vowel.'
An historic event. Giftiger wunsch is correct and the guy above him must not know basic english.

I just added both pronunciations to the article; not sure how that affects this rather crunchy discussion. I think both an elly-dee (individual letter names; UV LED rhymes) and a led (as a word; red LED rhymes) are both widely used pronunciations. But pronunciation as lede is incorrect and therefore the ambiguous lead should be avoided. However it is pronunced in the Wikipedia article, it should be done consistently. As for adding special hacks so that editors will see the rule, why not simply add it to the article so that all readers see it? Something like “LED, pronunced elly-dee or led, the first/second being used in this article”. Vadmium (talk) 06:53, 22 June 2011 (UTC).

But it's through ignorance that people say led (like red) so should it not explicitly say that it is pronounced as individual letters so that people don't think it's in any way correct to pronounce it wrong. The only people that are getting bothered are those that are in the habbit of calling them led (red) and refuse to admit they are wrong and get on with it. Hasn't someone already mentioned that the dictionary states it is L-E-D. — Preceding unsigned comment added by (talk) 17:32, 22 June 2011 (UTC)

I'm afraid that this is one of those British/American English things. Those people who have pointed out that in English 'an' only ever precedes a word that actually starts in a vowel are entirely correct. Thus 'an history' is actually wrong (this seems to have come about as a form of snobbery by people who know that the original French word of pronounced 'otel'). Equally if you accept 'led' as a word then it is 'a led'.

Unfortunately, the Americans haven't used English for nearly two and a half centuries, and have adopted many rules (and spellings) of their own - largely through laziness at learning anything remotely complex. Thus the Americans will add an 'an' to any word whose pronounciation starts with a vowel. Thus they may say 'a led', but will incorrectly say 'an ell-ee-dee'.

Wikipedia's style guide cuts straight through the problem and although it requires that the English used throughout an article is consistently British or American, it does state that the use of 'a' or 'an' depends on the pronounciation (i.e. the American system). DieSwartzPunkt (talk) 18:23, 23 November 2011 (UTC)

Are you seriously saying that "a hour" is correct opposed to "an hour"? It's not snobbery - you're just wrong. You seem to suggest that it's Americans that have added 'an' before words that start with a vowel sound, but ask any native British English speaker. They will tell you it's "an hour" because the word starts with a vowel sound. — Preceding unsigned comment added by (talk) 17:02, 18 March 2013 (UTC)
Wow, what a discussion! It is most certainly an LED, and an hour. LED should definitely be pronounced ell-ee-dee. I just asked a couple of electronics hobbyists these questions, and it was as obvious to them as it was to me which was correct.
“I have desoldered an LED for you” vs “I have desoldered a LED for you”
“I will be back in an hour” vs “I will be back in a hour”
However, this would be misuse of an: “I have desoldered an single LED for you.” See how different “wrong” sounds?
BTW, I saw the word “pronounciation” appear above; the correct spelling is “pronunciation.” Oh well. (talk) 13:29, 24 March 2013 (UTC)

SMD Leds[edit]

Anyone want to upload a pic of surface mount (device) led? —Preceding unsigned comment added by (talk) 23:43, 5 January 2011 (UTC)

I'll see if I can take a decent picture of one if I get time tomorrow. I don't think I have a free SMD LED, but I'm fairly sure I have a PCB or two with one on which I could photograph. I'm surprised there isn't one in the image on the article with various different types of LEDs. GiftigerWunsch [TALK] 00:08, 6 January 2011 (UTC)
Looks like I forgot; I'm unlikely to get time to do this in the especially near future, but next time I have a spare minute and remember about it I'll see if the article still needs one and make one if it does. GiftigerWunsch [TALK] 23:49, 8 January 2011 (UTC)

Advantages and Disadvantages sections[edit]

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.

Effective temperature of a black body compared with the B-V and U-B color index of main sequence and super giant stars in what is called a color-color diagram.[1]

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)

Efficacy vs efficiency[edit]

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)

As LED's have been known for decades as having high efficiency and (when emitting in the visible spectrum) luminous efficacy, and the article gives considerable detail of the progress of luminous efficacy in the development of white light LEDs, I have deleted the spurious markup that labelled the claim of high efficacy as dubious. I don't know whether it was originally inserted due to ignorance or because an earlier form of the article did have something dubious. I also reworded the comment on the high efficacy, to link to the luminous efficacy article. I removed the phrase 'as measured by its light output per unit power input', superfluous in context, but added the word 'sources' to eliminate the possibility that we refer to luminous efficacy of radiation. (LED's offer high luminous efficacy in either sense of the term, but it is the efficacy as a source that offers advantages as lighting sources.)
By the way, the high luminous efficacy of a LED as such is not actually suitable for comparing with, say, an incandescent light bulb. The latter, though poor in efficiency and luminous efficacy, does run directly off the mains (or battery, etc), whereas a LED (whether powered by a dc source or from the mains) usually requires a power supply that also dissipates power. So the 'input power' for relevant comparisons must be the total power drawn from the power sources (mains, battery, etc) rather than just the input to the LEDs. This issue is discussed in the luminous efficacy article, where various alternative phrases are mentioned, such as wall-plug luminous efficacy, for being more explicit that the efficacy is calculated on the entire power consumed. One of these phrases is 'lighting efficiency', which would be much nicer if only we could be sure that everyone would agree on what that means. I doubt it.

--Alkhowarizmi (talk) 10:51, 2 August 2011 (UTC)

Efficacy at low temperatures[edit]

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)

Outdated information and questional section "Energy consumption"[edit]

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. -- (talk) 13:10, 8 July 2011 (UTC)

Indented line FYI - Incandescent lamps have been used for food warming, incubators, personal heater (such as valets) and for cooking, such as the Easy Bake Oven. In lighting, discussions of which is more efficient in winter has been debated, since incandescent is an efficient heater. --Danpeddle (talk) 06:05, 12 November 2011 (UTC)
Electricity is almost always generated by heat - in coal, natural gas or nuclear power plants. You generate heat to generate electricity to generate heat. Converting electricity into heat may be very efficient but the vice versa conversion isn't. There's always loss. That is what makes heating with electricity inefficient. For example, using the heat generated as an otherwise unneeded by-product of industrial factories and heat-pipelines is much more efficient because you virtually get your heating for free. Similar goes for solar collectors, geothermal heat, organic gas etc. -- (talk) 14:49, 13 January 2012 (UTC)

Inaccurate Diode curve description[edit]

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)

I guess you’re talking about the graph under LED#Physics. I agree it’s a bit misleading; maybe it would be better to avoid talking about light because the graph only covers current and voltage. My understanding is LED light is approximately proportional to the forward current, and the forward current of any diode is roughly an exponential of the forward voltage. A particular diode’s “on” voltage depends on the order of magnitude of the forward current in this “on” mode. Vadmium (talk) 06:51, 3 September 2011 (UTC).

Semiconductor "die"[edit]

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 (talk) 15:09, 28 October 2011 (UTC)

"Die" is all around the article and it means die (a small block), not dye (paint). Materialscientist (talk) 23:58, 28 October 2011 (UTC)

Pulsed LEDs[edit]

The article talks about pulsed LEDs in the context of dual brightness systems:

"In a dual intensity circuit (i.e., rear markers and brakes) if the LEDs are not pulsed at a fast enough frequency, they can create a phantom array, where ghost images of the LED will appear if the eyes quickly scan across the array."

However, LEDs are visibly pulsed in many situations where there appears to be no obvious reason. For example, the turn signal indicator on cars where there is no dimmed option (or requirement). Brake lights in the same application where they are separated out from the tail light cluster (and the tail light cluster is pulsed as well). Front mounted side lights on cars. Traffic lights (some dim at night but the lights are still pulsed during the day). The list goes on. Any ideas anyone? DieSwartzPunkt (talk) 18:10, 23 November 2011 (UTC)

I'm not sure what you're actual question is - but the quoted line refers to the stroboscope effect. There's no such effect - to the human eye - for low frequencies ("visibly pulsed" qualifies)and therefore no issue. -- (talk) 13:46, 27 November 2011 (UTC)
“There's no such effect”!! Maybe for your eyes. Not mine, I can see this on many cars with LED lit taillights, especially when the eye is glancing from one object to another. On a few occasions, I have been following behind a car that had very bright taillights running at a frequency so low that I could see it continuously, without averted gaze. I would get a strong headache/eyeache within a minute. Very annoying. (talk) 13:18, 24 March 2013 (UTC)
My question is: why go to the trouble? Why bother including a complication to cause the LEDs to flash when a simple resistor that will give a continuous light output will do an equally good job (as far as the eye can perceive at least). Now knowing how car manufacturers penny pinch at the slightest excuse, they must have a very good reason for including an apparently redundent flasher circuit. DieSwartzPunkt (talk) 19:15, 5 December 2011 (UTC)
Are you talking about Pulse width modulation? If you want to run, say, a 10 watt LED at half brightness, if you're using a linear resistor you must dissipate about 5 watts in the external resistor so that the LED only gets 5 watts. Or, you can use a switch which dissipates almost no power, and duty-cycle the LED at 50% on time so as to appear half-bright. Sometimes a switch that dissipates no power is cheaper than a relatively high-powered resistor. You have to do the PWM at a frequency high enough to avoid visible annoying "strobe" effects. --Wtshymanski (talk) 19:36, 5 December 2011 (UTC)
I follow your point, and I was aware of this. However, my fundamental point remains: what car manufacturer is going to install a PWM when a simple resistor is a much cheaper option? The difference in power consumption is hardly a problem in this application being, as it is, less than a watt ot two.
I have just erected my Christmas tree for this year and decced it out with LED lights. These flash as well (very rapidly). Why? What's the point? The LEDs connected in series/parallel can easily be run from the 24 volt power supply without any series resistor at all. DieSwartzPunkt (talk) 12:05, 11 December 2011 (UTC)
PWM is typically used when a variation in the light output is needed. It is rather more complicated to control the light output using the voltage then the current. --Thorseth (talk) 09:10, 12 December 2011 (UTC)
I understand that point. But in both the applications I have mentioned, there is no requirement (or provision) for dimming the light output. DieSwartzPunkt (talk) 16:33, 12 December 2011 (UTC)

There is an effect that I read about 30-40 years ago. Multiplexed LED displays are brighter in appearance than they would be if driven staticly: In other words, drive an LED with 100 milliamp rapidly pulsed (say, over 100 hz), 10% duty cycle, and it will appear brighter than the same LED driven with 10 milliamp driven continuously. A small portion of this effect is that LEDs are more efficent driven at higher current levels, but most of this is related to the sensitivity of the (human) eye. Jamesdbell8 (talk) 16:00, 14 July 2012 (UTC)

I remember reading somewhere that an LED is at its brightest during the first few micro or milliseconds after it is turned on, which is why the high frequency PWM DC driving circuit is used, providing more light for less total Amps.
(Thus presumably allowing the car manufacturer to make a cost saving by fitting smaller cables to the light fittings in the vehicle. Having more copper wire in a vehicle can be more expensive than having more (incredibly cheap Chinese) microcircuits.)
This is quite important to the "Considerations for use": `Power sources' section. If anyone has more information on this, please add it to the article or possibly put a link to a site with the data. Thanks. Darkman101 (talk) 19:49, 19 September 2012 (UTC)
I added a little about pulsed operation to LED circuit#Pulsed LED operation. I agree that many people think that pulsing LEDs somehow makes them brighter or seem brighter, but I suspect that is an urban legend, caused by a misunderstanding of the *other* reasons people pulse LEDs. --DavidCary (talk) 00:32, 28 December 2012 (UTC)
Certainly for white LEDs, it's no longer the case that brightest operation (i.e. a pulsed current greater than the largest constantly sustainable current) uses pulsed drives. This may still need updating or expanding. Andy Dingley (talk) 00:47, 28 December 2012 (UTC)

Layout & polarity 3528 SMD LEDs[edit]

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)

The arguments could go something like this: The image was placed in the lead. We would like that ... "The image helps to provide a visual association for the topic, and allows readers to quickly assess if they have arrived at the right page." From the style manual Wikipedia:Images#Images_for_the_lead I do not think that this images does any of this. Further more, I do not find the polarity of the LED to be obvious from the ajacent diode symbol. I am also missing a scale, to see how big the thing is. The caption (which is placed inside the image??) states that it is a "Typical 3528 SMD LED layout" ... Does this mean that there are other layouts of this type of LED? This is difficult to find out, because this particular type is not mentioned in the main text. I not saying the image can't be used, just that I have some questions my self: Does this LED have a special signifigance or is it representative of other LEDs since it belongs in the lead? Why does it need two captions? Perhaps it could be used to illustrate a section on SMD components or similar?--Thorseth (talk) 06:28, 23 January 2012 (UTC)

Is this important enough to mention?[edit]

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)

Copied from WP:VPP:Vchimpanzee · talk · contributions · 18:47, 11 February 2012 (UTC)
One of the sections of our verifiability policy is titled Exceptional claims require exceptional sources and is relevant here. Your edit states that Cree's new LED "delivers twice as much light for the same price", which I would qualify as an expentional claim. Accordingly you would need multiple high quality sources to back it up. The source you give is barely one step up from a press release, the guy is obviously just repeating what he heard from the PR guys. Yoenit (talk) 00:07, 11 February 2012 (UTC)

LED Failure[edit]

What happens when an LED fails or burns out does it open or short? Just Curious — Preceding unsigned comment added by (talk) 21:04, 20 April 2012 (UTC)

They can fail either way, or sometimes they jsut get really dim - either there's less light emitted or the package turns yellow or clouds over. Probably worth some text here. --Wtshymanski (talk) 15:35, 25 April 2012 (UTC)
In my experience (probably not good enough for Wikipedia articles :), I can only think of diodes failing on my with a short circuit, mostly due to overcurrent or overheating. This includes LEDs with way too much current, the silicon diode used as a reverse power polarity shunt on a hard disk controller (despite blowing the diode casing apart), and zener diodes. Anecdotes aside, people do write that having LEDs go open circuit is a potential problem for connecting them in series, and I think I saw LEDs advertised somewhere that had integrated zener diodes to avoid this problem (at least until the zener went open-circuit). BTW did you see the link to List of LED failure modes? It briefly mentions short circuits but not open circuits. Vadmium (talk, contribs) 12:54, 27 April 2012 (UTC).
In my experience, an LED (yes, an LED, not a LED) always opens when it burns out. 100% of the time. And I have burned out dozens of them. LEDs that burn out from long-life in a stressful application start getting dimmer, and may start flickering as well. Their zener voltage (and thus resistance) may start increasing at this point, until the LED stops lighting at all. At this point, the LED will be open (or nearly so); but because of the zener effect, one may be able to make it conduct (and light) again by increasing the available voltage. This is why on graphic equalizers that have an LED on each slider, the whole group of LEDs may start flickering if just one LED goes bad (wired in series). LEDs that are forcefully burned out (from serious overcurrent), usually burn out because the little wire going from the anode to the chip sitting on the cathode vaporizes, thus disconnecting/opening the LED. This opening behavior in LEDs is the opposite from switching (or rectifier) diodes, which always short when they fail; however, sometimes even these will open due to the fuse effect, if the current increases greatly when the device shorts. (talk) 13:07, 24 March 2013 (UTC)

Entangled photons[edit]

There are LEDs now that produce entangled photon pairs, might want to add that... to wit: (talk) 05:25, 8 May 2012 (UTC)

Index of Refraction of Silicon may be wrong.[edit]

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)

Fixed it, thank you!--Thorseth (talk) 07:14, 15 July 2012 (UTC)

Phosphor-based LEDs Efficiency[edit]

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)

The only way that makes sense if it means "efficacy" (visible light (lumens)/watt) instead of "efficiency" (total radiation, watts/watt) - a monochromatic blue light will have a low efficacy,even if it's very good at changing electric power into blue light. Using the curve in Luminous efficacy, if the lamp was blue enough, a 5-fold increase looks possible to me. Probably wants a reference or deletion. Stokes shift is where most of the energy is lost in modern fluorescent lamps, too. --Wtshymanski (talk) 16:44, 20 July 2012 (UTC)
Ok, I've gone ahead and deleted that sentence, since even if it means efficacy it seems silly to compare the bare blue LED to anything, since no one would use a blue LED for lighting. Data on the relative efficiency/efficacy of the phosphor-coated LEDs to CFL/RGB LED would be useful, but I haven't found any good references. Wingedsubmariner (talk) 01:22, 21 July 2012 (UTC)

Update needed?[edit]

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)

Someday, yes. But right now $1.50 CFLs are putting out the same lumens as $30 LED, so as of 3rd Q 2012 it is still a valid observation. --Wtshymanski (talk) 20:40, 17 August 2012 (UTC)
Ah -- thanks! -- Jo3sampl (talk) 12:29, 18 August 2012 (UTC)

Internal resistivity[edit]

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 (talkcontribs) 03:50, 29 August 2012 (UTC)

Led lights[edit]

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 (talk) 14:28, 28 December 2012 (UTC)

Wikipedia is not a product catalog. Jeh (talk) 21:45, 26 April 2013 (UTC)

crediting Oleg Losev…[edit]

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 (talkcontribs) 23:26, 6 March 2013 (UTC)

A reliable source that credits Losev for the invention is present in the article ([1]).G_PViB (talk) 01:33, 11 April 2013 (UTC)
So why not H. J. Round? Clearly predates Losev, and about as much practical impact. --Wtshymanski (talk) 01:43, 11 April 2013 (UTC)
I'm not opposed to crediting him as well. G_PViB (talk) 01:56, 11 April 2013 (UTC)
Sure, and Tesla. Hey, let's put in Thales of Miletus while we're at it. That would make this a Greek invention. But seriously, the device invented at GE is the light emitting diode, and all these mad laboratory experiements are just that...not practical devices. --Wtshymanski (talk) 13:25, 11 April 2013 (UTC)
As long as their work is deemed important enough by a reliable source. G_PViB (talk) 17:41, 12 April 2013 (UTC)
I'm sorry, I think this is ridiculous. Losev discovered the phenomenon that underlies the LED's operation, but he didn't invent anything like the modern device. To say he did is like saying that William Crookes invented the cathode ray oscilloscope, complete with triggered sweep. Same for Round. I have no problem identifying Loseg and Round as independent discoverers of the phenomenon, however. Jeh (talk) 21:04, 20 April 2013 (UTC)
Regarding your objection - you'll need to achieve a consensus to delete the contents which warrant the categories before deleting the categories themselves. G_PViB (talk) 08:33, 21 April 2013 (UTC)
A critical reading of the reference given, and related material, does not support the claim of "Russian invention" or "Soviet invention". Discovery of principle, yes, but there was no discernible contribution to the line of development that led to the device we today call "Light emitting diode". A category of "Russian discoveries" would be supportable, particularly if it was on an article entitled "electroluminescence" rather than "Light emitting diode". Jeh (talk) 16:45, 26 April 2013 (UTC)
I'd rather go with the opinion of the Nature Photonics editors board. G_PViB (talk) 16:47, 26 April 2013 (UTC)
What you would "rather go with" cannot override consensus. As far as I can see you are one person trying to add the "Russian inventions" category to a number of different articles, even creating otherwise-unnecessary redirect pages just so you can slap this category on them. As to this particular question, yes, Nature has their boards of editors, but WP has its editors as well. It is not the job of WP editors to blindly copy what we find, even in sources normally as reliable as Nature. That is why competence is required here. Jeh (talk) 17:01, 26 April 2013 (UTC)
Perhaps if User:Jabeles didn't write his post in such a patronizing tone we could have had a more constructive debate. I argue knowing well from my area of expertise (firearms) that a swarm of editors expressing a biased opinion do not make it more verifiable. G_PViB (talk) 17:42, 26 April 2013 (UTC)
I see no patronizing tone in Jabeles' post at all. It is reasonable, reasoned, patronizes no one, and is well grounded in WP policy and precedent. Regardless of whether s/he intended to be patronizing or not, you do not get to excuse yourself from WP's requirements (such as WP:CIVIL) for resolving content disputes just because you don't like the tone you think was presented by someone else. Labeling others' opinions as biased does not help you either. Jeh (talk) 21:56, 26 April 2013 (UTC)
I'm sticking to the principial Wikipedia policies. On the other hand we have a bunch of users who got upset when they were reminded that their opinion is worth squat. Do mind that by the way of priority of policies, if infringing on your inflated ego causes you to lose sight of the content dispute it is your problem first. (Personally, I think that if we get rid of the oversensitive people it would only benefit the project.) As for User:Jabeles - his tone does represent the complex phenomenon of latent Russophobia. G_PViB (talk) 01:06, 27 April 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)

Request for Discussion of {{Semiconductor packages}} in electronic articles[edit]

Please see the corresponding discussion thread at Wikipedia talk:WikiProject Electronics. Thanks! • SbmeirowTalk • 23:34, 15 December 2013 (UTC)

Unreliable efficiency droop source removed[edit]

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. Jojalozzo 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)

Picture of Die & Bond-wire[edit]

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.

This is a second shot of a surface mount LED, showing the PN junction and the bondwire.

/-\urelius |)ecimus What'sup, dog? 05:24, 2 February 2014 (UTC)

smart lighting[edit]

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)

Section deleted should be included[edit]

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.[2]

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)

Please sign your post. I'll respond after that. Jeh (talk) 01:21, 22 February 2014 (UTC)
(Thank you.)
The referenced article does NOT support the editor's claim that "LEDs can be used as microphones." (Like most diodes, LEDs are only very slightly microphonic.) It does say that monitoring devices (it does not say "listening") are being built into LED-lit lighting fixtures. There is nothing about an LED lighting fixture that makes it any more suitable for concealing a monitoring device than any other sort of lighting fixture—or, for that matter, a painting hung on a wall, or a potted plant, or a trash can.
That some company is building light fixtures that happen to both a) use LED lamps and b) include some sort of monitoring devices (never claimed, by the way, to be sound pickup) is not germane to this article. Nor did the company rep interviewed in the video say anything about the LEDs being used to transmit the collected data (a la IrDA or similar), so that claim is unsupported too.
The editor misquoted the reference a second time: the company representative never said "the potential of LEDs to collect data on the people is nearly boundless", rather that "the potential for the advanced lighting is nearly boundless." And the video interview with that representative never mentioned listening at all!
The referenced page does link to another page with a completely unsupported claim about "one modified LED bulb that will send audio over 300 meters." Well, sure. There was a project like this in Popular Electronics decades ago. (It didn't use an LED, though, just an incandescent bulb.) The LED is still not being claimed to be the actual microphone. If it did, then as someone who has been working with both LEDs and microphones for literally decades, I would find that claim to be completely specious unless some better references were found.
I repeat: An LED is simply not very microphonic. If you want to build a listening device, you'd best start with an actual microphone. These can be so small as to be virtually unnoticeable: a little smaller than a typical T1-3/4 LED. You could modulate the LED and use that to send the audio somewhare, but the claim that "LEDs can be used as microphones" is not supported, and in this editor's opinion, is ridiculous on its face. Jeh (talk) 03:12, 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)

Sorry but you need to counter the points I made, not just come back with "well I think it should." I could certainly see mentioning the EWR system in the Surveillance article. But in the video interview with the company rep there was not one mention of any way that the LED light sources contributed to the surveillance function of the fixtures... so what is the relevance here?
These lighting fixtures no doubt employ plastic; should we mention them in the "Plastics" article too?
As for the note that LEDs are not very microphonic, first things first: you need to make a case that a mention to these monitoring devices belongs here. You haven't done that. After that... there is no claim in the article you linked to nor in the video interview therein that the EWR system is picking up sound, so "LEDs are not very microphonic" would be irrelevant, even puzzling. And to anyone in the field it is also a "the sky is blue" claim, not really needing a reference. Our own article on Microphonics details the components that typically are microphonic; diodes, light-emitting or otherwise, are not among them. There really isn't any doubt or ambiguity about it. Jeh (talk) 05:20, 22 February 2014 (UTC)
To Wyn.junior, please do not confuse an "LED" with a "light fixture". A light fixture consists of many parts that can include LEDs, power conversion circuitry, and perhaps other things like a microphone. Be aware that sloppy editing in some articles might use the term "LED" to refer to larger assembly or fixture instead of the discrete component. Rich S 10001 (talk) 18:06, 5 October 2014 (UTC)

The Health Dangers of LED Lights[edit]

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. — Preceding unsigned comment added by Nmakh (talkcontribs) 06:03, 23 April 2014 (UTC)

LED TV's[edit]

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)

Going to need some extra-reliable sources for such claims. The CRTs in TV sets were almost never the primary point of failure or the limiting factor on lifetime. Yes, CRTs did go bad and needed to be replaced now and then, but failures in other components were far more common. Nor do we write WP articles based on what is "apparently" true (note correct spelling) And "about 66% less durable"? Where did you find that number? Are you sure it isn't 65%? Jeh (talk) 10:05, 23 July 2014 (UTC)
AFAIK, most consumer-grade LED TVs use organic LEDs. For them, it is just the opposite. While the typical lifespan of anorganic LEDs is magnitudes greater than that of CRTs or LCDs, the lifespan of OLED displays is considerably lower. It is typically estimated to be between 1 and 4 years, depending on various conditions. I don't have sources at hand right now, but I have seen several (including some studies) in the past. These short lifespans are not considered a problem by manufacturers, because the devices incorporating these OLEDs are considered "outdated" and "obsolete" even earlier (not my opinion). --Matthiaspaul (talk) 11:55, 23 July 2014 (UTC)
First, inorganic LEDs are used in place of cold-cathode-fluorescent-lamps (CCFLs) in the backlight assembly of LCD TVs. CRT TVs are not really the issue. CCFLs are reasonably efficient, effective and long-lasting as a light source, but they do contain a small amount of mercury. LEDs have challenged CCFLs because they are even more efficient, longer-lasting, low enough in price so the cost-add to consumer is not enormous, and backlight assembly designs have been well adapted to efficient use of LEDs. Second, organic LED (OLED) TVs are a more recent display type. They are emmisive displays, like CRTs and plasma TVs, where the pixellated image comes from glowing dots. LCD TVs (with either CCFL or LED backlights) are transmissive displays -- the pixellated image comes from liquid-crystal cells of variable light density, and a color-filter matrix.Rich S 10001 (talk) 18:22, 5 October 2014 (UTC)

Another advantage: less insect deaths[edit]

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.--TeakHoken213.150.232.3 (talk) 13:34, 9 September 2014 (UTC)

Quantum Dots[edit]

This technology has been commercialized, and is no longer "experimental", in the form of plastic sheets or films. QD Vision received a technology award ( The QD film is used in Sony LCD TVs (with the TRILUMINOUS trademark) since 2013, and more recently, Amazon Fire tablet computers. The film converts blue light from LEDs into red and green, to provide the RGB emmisions in balance to achieve the desired white-point (e.g. 6503 K). Rich S 10001 (talk) 18:47, 5 October 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)

light emmiting diode[edit]

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) (talk)

light emmiting diode[edit]

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.

12:44, 26 October 2014 (UTC) (talk)

  1. ^ Cite error: The named reference UBV was invoked but never defined (see the help page).
  2. ^ Don't look now but the LED light fixtures are spying on you, Computer World, 18 February 2014, Darlene Storm