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#4670583 - 02/19/18 08:25 AM Who Knows About LED's ??
billt460 Offline


Registered: 03/30/15
Posts: 4394
Loc: Glendale, Arizona
What is the yellow "stuff" that glows so brightly in a modern LED? These are nothing like the dim red LED's that were in the old 70's Texas Instruments calculators, and the first digital watches. Or like the LED's you see on circuit boards that look like miniature light bulbs. When and where was the big breakthrough? These things went from barely a glow, to all of a sudden becoming blindingly brilliant.

I remember when Surefire Flashlights started out, they didn't have anything that was LED. Now it's practically everything they make. It's becoming much the same in home and automotive lighting. It just makes me wonder when and where the big improvement came along? Because it seems like it happened all at once.

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#4670590 - 02/19/18 08:28 AM Re: Who Knows About LED's ?? [Re: billt460]
Crispysea Offline


Registered: 04/14/17
Posts: 402
Loc: TN USA
Phosphor, much like a fluorescent bulb. The LED itself usually emits a blue and/or UV light that makes the yellow phosphor glow. The blue LED was the last to be invented. Not until about 2000 were they perfected, and white lights were finally available.


Edited by Crispysea (02/19/18 08:30 AM)

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#4670620 - 02/19/18 09:07 AM Re: Who Knows About LED's ?? [Re: billt460]
Virtus_Probi Offline


Registered: 06/25/15
Posts: 3970
Loc: New England
Once a viable blue LED was developed (largely due to Dr. Nakamura now at UC Santa Barbara) to allow the marketing of "white" LEDs that would be useful for general purpose lighting, the race was on to up the lumen output and deal with the considerable heat issues with LEDs. Not that they aren't efficient, just that the materials can't deal with the heat they produce and it's hard to keep them in a temp range where they work properly (unlike a filament bulb that works exactly because it is super hot). One would probably also need to give some credit to GaN products developed largely for military and space applications for laying that background that LED researchers were able to take advantage of.

Most of my professional work has been with red LEDs so I only have a passing familiarity with the white products...red has its own technical issues because the forward voltage is low and accurately controlling a single LED can be a challenge if you also have to cover applications with long strings of much higher voltage.

I had a semiconductor physics professor in college who told us that the first person who mastered blue LEDs would become a billionaire because that would allow super TVs to be built with tiny RGB LED pixels. Imagine my dismay when I learned that the first LED TVs only used that technology as a backlight source for an LCD...I think even now only a prototype TV from Sony actually works the way my professor envisioned it, even OLEDs rely on filters to make colors from white sources.
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#4670673 - 02/19/18 09:48 AM Re: Who Knows About LED's ?? [Re: billt460]
EdwardC Offline


Registered: 11/14/13
Posts: 1862
Loc: Chicago, IL
Like VP mentioned, a large part of the white LED lighting boom came from the creation of the blue LED. I believe the color of most LEDs are due greatly to the specific materials used in the PN junction to achieve the band energy needed to release the specific color of light. Red light, for example is a longer wavelength (lower energy) than blue light.

Once the materials were discovered, they could throw phosphors over the blue to create white light. Since blue is on the highest side of the energy spectrum of visible light, phosphors can much more efficiently convert the high energy blue light down to other colors (like orange, red, etc). The combination of blue light, and the phosphor converted red, orange (and other proprietary mix of down converted light) creates the white light we see.

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#4670789 - 02/19/18 11:35 AM Re: Who Knows About LED's ?? [Re: billt460]
Snagglefoot Online   content


Registered: 12/31/17
Posts: 1720
Loc: Alberta
I first became aware of it when my son bought me a tactical flashlight labeled Ultrafire, a Chinese knockoff of Surefire, around 2014. Then, they were being used in the work light stands, replacing those super hot skinny Halogen bulbs. In 2015 I replaced all the 12 volt bulbs in my travel trailer and last year I started replacing my halogen floodlights in my ceiling with LED bulbs. Glad to have gotten rid of those fluorescent bulbs. All my flashlights are now LED.



Edited by Snagglefoot (02/19/18 11:39 AM)

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#4670791 - 02/19/18 11:38 AM Re: Who Knows About LED's ?? [Re: billt460]
Snagglefoot Online   content


Registered: 12/31/17
Posts: 1720
Loc: Alberta
Here is my favorite LED floodlight bulbs. The light frequency is perfect, being fairly natural and not overly white. Even though they were labeled bright white they seemed closer to a warm white to me.





Edited by Snagglefoot (02/19/18 11:44 AM)

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#4670813 - 02/19/18 11:52 AM Re: Who Knows About LED's ?? [Re: billt460]
Reddy45 Offline


Registered: 08/15/08
Posts: 2968
Loc: USA
It seems like CREE led was the turning point for lights becoming blinding.

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#4670817 - 02/19/18 11:58 AM Re: Who Knows About LED's ?? [Re: Reddy45]
4WD Offline


Registered: 09/21/10
Posts: 6369
Loc: Texas
Originally Posted By: Reddy45
It seems like CREE led was the turning point for lights becoming blinding.


Part of it but that football stadium lighting on the front of the new Ford Super Duty looks halogen - with a poor aim of light

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#4670835 - 02/19/18 12:09 PM Re: Who Knows About LED's ?? [Re: Virtus_Probi]
y_p_w Offline


Registered: 05/06/05
Posts: 3650
Loc: SF Bay Area
Originally Posted By: Virtus_Probi
I had a semiconductor physics professor in college who told us that the first person who mastered blue LEDs would become a billionaire because that would allow super TVs to be built with tiny RGB LED pixels. Imagine my dismay when I learned that the first LED TVs only used that technology as a backlight source for an LCD...I think even now only a prototype TV from Sony actually works the way my professor envisioned it, even OLEDs rely on filters to make colors from white sources.

I remember the first time I heard about blue LEDs. I was thinking what would be the use other than maybe different indicator lights.

There are all sorts of things that sound interesting in theory, but the key is overcoming manufacturing obstacles. LCDs with filters and backlights can be manufactured pretty easily these days. Silicon isn't even the ideal semiconductor, but the consistency and costs of manufacturing are why it still dominates. I remember being shown a microscopic cross-section of a silicon oxide layer next to oxide grown on GaAS, and it was pretty clear that it was far easier to work with silicon.

One of the more interesting uses I've heard of for LEDs is Dolby Labs professional studio displays. They come with a pretty standard, high quality 42" LCD, but the backlight consists of over a thousand individually controlled RGB LED sets.

Quote:
https://www.dolby.com/us/en/professional/cinema/products/prm-4220.html
https://www.dolby.com/us/en/professional...rm-4220-FAQ.pdf
How can the Dolby Professional Reference Monitor achieve true black levels with exceptional dark detail, precise color accuracy, wide dynamic range, and a high contrast ratio when other flat-panel monitors cannot?

The backlight of the Dolby Professional Reference Monitor consists of 1,500 RGB LED triads, with the light from each red, green, and blue element independently controlled frame by frame to create a full-color image. This image, together with the image on the LCD panel, produces the final image—one of extended dynamic range with the widest and most accurate color gamut available in a flat-panel monitor.

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#4670863 - 02/19/18 12:36 PM Re: Who Knows About LED's ?? [Re: billt460]
oldoak2000 Offline


Registered: 07/23/14
Posts: 119
Loc: North TEXAS
Originally Posted By: billt460
What is the yellow "stuff" that glows so brightly in a modern LED? These are nothing like the dim red LED's that were in the old 70's Texas Instruments calculators, and the first digital watches. Or like the LED's you see on circuit boards that look like miniature light bulbs. When and where was the big breakthrough? These things went from barely a glow, to all of a sudden becoming blindingly brilliant.

I remember when Surefire Flashlights started out, they didn't have anything that was LED. Now it's practically everything they make. It's becoming much the same in home and automotive lighting. It just makes me wonder when and where the big improvement came along? Because it seems like it happened all at once.


"... It was while working for Nichia that Nakamura invented the first high brightness gallium nitride (GaN) LED whose brilliant blue light, when partially converted to yellow by a phosphor coating, is the key to white LED lighting, which went into production in 1993...."

That was the spark that started the high-brightness explosion.

The newest/Coolest thing are 'COB driverless led's' that have EVERYTHING right on the metal backer; - https://www.ebay.com/itm/30W-50W-100W-15...aETi1oDwmYfXHqA
12000 lumen!! connect directly to mains power:

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#4670916 - 02/19/18 01:38 PM Re: Who Knows About LED's ?? [Re: billt460]
billt460 Offline


Registered: 03/30/15
Posts: 4394
Loc: Glendale, Arizona
A lot of good information here. Many thinks to everyone who has contributed!

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