newbie here: what does LED stands for?

flashniac

Newly Enlightened
Joined
Jan 6, 2005
Messages
42
Location
caribbean
Iwould like to know what LED stands for and what are the advantages in front of an incandescent bulb?
 

CroMAGnet

Flashlight Enthusiast
Joined
Sep 4, 2004
Messages
2,540
Location
Los Gatos, CA
Here is a link to a place that has info on lots of things. HowStuffWorks

Here is a little snippet "LEDs have several advantages over conventional incandescent lamps. For one thing, they don't have a filament that will burn out, so they last much longer. Additionally, their small plastic bulb makes them a lot more durable. They also fit more easily into modern electronic circuits.

But the main advantage is efficiency. In conventional incandescent bulbs, the light-production process involves generating a lot of heat (the filament must be warmed)."

I also learned the other day about why it is so hard to get the color to be a consistant white. Someone correct me as I miss things here... LEDs are blue as they are made and coated with phosphor which is yellow and the process is not exacting as to how much phosphor to create the exact white so they somehow get labeled in bins or groups. ... My first stab at understanding this /ubbthreads/images/graemlins/smile.gif

LED Museum Has a lot of answers to your questions and more.
 

WildRice

Flashlight Enthusiast
Joined
Nov 30, 2003
Messages
1,135
Location
SW Michigan
Close enough for govt work CromagNet... This process is for a select number of LED's. There are White, and also Pink LEDs that are a blue 'die', (the "crystal" part of the LED that generates the light), that are coated or sprayed with a yellow emitting phosphor, (or pink).
All other colors are generated in the LED 'crystal', as the color that you see.

Jeff
 

CroMAGnet

Flashlight Enthusiast
Joined
Sep 4, 2004
Messages
2,540
Location
Los Gatos, CA
LOL govt... So what about the coveted XO bin. Why are they so hard to get. Or sell for more. I was 'assuming' that it was because of the imprecision of the process of coating the blue LEDs with yellow phospor. I've always wondered this but only recently figured it was the phospur. /ubbthreads/images/graemlins/icon3.gif
 

Surefire_Rocks

Newly Enlightened
Joined
Dec 24, 2004
Messages
156
Location
Kansas
Hi flashniac,
LED stands for Light Emitting Diode, and I personally find them better than their rival incandescent bulbs. First of all, they are more efficient in terms of run time and output. They will also never burn out on you, and they are usually more durable.
However, a typical LED will cost you a significant amount more than a similar incandescent bulb, but it is usually worth it.

-Ian Tracy-
 

WildRice

Flashlight Enthusiast
Joined
Nov 30, 2003
Messages
1,135
Location
SW Michigan
Not sure of XO is just color and or flux. LEDs are 'grown' inlayers from the 'bottom' up. It is called a L.E.Diode because it contains a P-N junction. As different layers are grown together there are going to be 'differences' across the wafer. the LED wafer is cut up into its pieces. (at least I think they are cut up from a large wafer), at any rate, there will be differences from die to die, even in a batch. This will lead to differences in brightness, color, and PN bias voltage. As far as color, FWIR, the original LUXI's had a mode crude form of phosphor coating.

To get PRIME binned emitters now is hit as miss, as far as production goes. Couple perfect crystal growth with a perfect layering of phosphor (which would have minor differences from batch to batch), and you can kind of see the uniqueness of the XO's.

Jeff

BTW, I hope I am correct about the above.
 

lahjik

Newly Enlightened
Joined
Dec 12, 2004
Messages
83
Location
Western NY
The cost issue on here isn't so much with the LEDs as it is with the LED "holders". Since the LEDs last so very long (we are talking about 5-10 years constant burn time) that the flashlights tend to be over-built to last as long as the LED. With cheap plastic incandescents, you can pay a dollar and then through them away without worry when the bulb burns out or breaks in a year (or when the batteries die). 50 years from now I will be looking for some of these flashlights to show up on the future version of the Antiques Roadshow. There will be a guy on there waxing poetic about how someone brought in the nicest 3rd_shift mod he has seen in many years.

There are inexpensive LED flashlights (20 keychain lights for $20 at CountyComm for example) but most of the LED lights discussed on here are built out of rather impressive quantities of machined metal.

As I was told before...welcome to CPF and I hope you either have deep pockets or strong willpower!
 

TORCH_BOY

Flashlight Enthusiast
Joined
Jan 25, 2004
Messages
4,242
Location
Australia, Vic
Welcome to the Jungle, LED= Light emitting Diode,
it is a solid state Light source. It has no filament.
More robust than a Light bulb.
 

idleprocess

Flashaholic
Joined
Feb 29, 2004
Messages
7,197
Location
decamped
[ QUOTE ]
CromagNet said:
LOL govt... So what about the coveted XO bin. Why are they so hard to get. Or sell for more. I was 'assuming' that it was because of the imprecision of the process of coating the blue LEDs with yellow phospor. I've always wondered this but only recently figured it was the phospur. /ubbthreads/images/graemlins/icon3.gif

[/ QUOTE ]
Any manufacturing process has acceptable tolerances. If the # of parts out of tolerance are low enough and the parts cheap enough, you can just scrap, repurpose, recycle etc the rejects.

In the case of LEDs, tint/wavelength are a tolerance. All semiconductor manufacturing operations have yield issues - a signifigant percentage of parts are out of tolerance that they have to be rejected - that require broader tolerances than many other manufactured parts. Cutting-edge processors reputedly have a yield rate of approximately 20%. In order to increase yields without, bins have been devised. This lets the customer know what they're getting without making a product with huge margins on specifications. Imagine if white LEDs weren't binned and the Vf could be anywhere from 2.8V to 4.2V, or if brightness varied by up to 100%...

In the case of flux and tint for white LEDs you have two factors with their own major tolerance issues - the diode itself (wavelength, flux), and the phosphor (spectrum, efficiency, quality of application).

The fact that it's rare to see a "poor-performing" Luxeon III indicates that Lumileds has improved their processes.

Specific bins are difficult to get for a variety of reasons...
It's cheaper to order unspecified bins and hope for the best
They're made in limited quantities
Volume buyers can afford to pay a premium for specific bins
Lumileds doesn't assign part numbers by bin, just by overall product, so you can't just spec a part number and get exactly what you want
 

PhotonWrangler

Flashaholic
Joined
Oct 19, 2003
Messages
14,432
Location
In a handbasket
LEDs are neat because they're technically quantum lamps; they make photons directly from electrons, rather than heating up a wire until it gets white-hot.
/ubbthreads/images/graemlins/cool.gif
 

CroMAGnet

Flashlight Enthusiast
Joined
Sep 4, 2004
Messages
2,540
Location
Los Gatos, CA
Very good info guys. Thanks a lot for trying to clear that up. I for one, hove a lot more to learn. This is always a good thing. /ubbthreads/images/graemlins/smile.gif
 

IsaacHayes

Flashlight Enthusiast
Joined
Jan 30, 2003
Messages
5,876
Location
Missouri
Also LED's (white) have a nice white color to them. They aren't yellowish like incandecents. Also, as the batteries get low LED's stay the same snow white color. Icandecents get a nasty yellow dim color. Take batteries out of a dead incacedent flashlight and put them in an led flashlight and you got light that is white and useable.

There are variations in the tint of white leds. You normaly can't tell unless it's sever by itself until you comepare several LED's side by side. They all will look whiter than icandecents..
 
Top