LED Lighting 101

Today and tomorrow ... and then some

dummy book fun -- LED there B light for YoyoEye

Let's clarify some myths and problems about LEDs - step by step. Also, find more in-depth resources.

Important simple problems

and how to Go About Them

LED is short for Light Emitting Diodes
  1. Most LED lights are cool white, not warm yellow white.
    See how to use this problem to your advantage in your home with LED rope lights, then you can apply this to other lights too.
  2. White LEDs fade over time - low quality LEDs fade sooner then you might think.
  3. Lifetime of LEDs can be very much color dependent.

ALSO Important ...

Now, this is not just simply bad news, it can be dangerous too. We had a very important discussion about this with other visitors and I put up a page where this apply most -- for blinding or strobing tail lights. Also, learn a bit about persistence of vision that creates the problem in the first place.

Because it can also give you very enjoyable experiences.

Other problems

For the Slightly Less 'Techno-Challanged'

Don't believe me? I don't blame you. But ...

With even the best of intentions, manufacturers and dealers are NOT bound by a coordinated code of standards and terminology. At least not yet.

Truth is, the industry is quite young. Standards covering them can not be fully formed. And so the terms (sometimes basic concepts) about LEDs out there are at times inconsistent -- even contradictory.

As a result, dealers may use wording and descriptions that can be misleading. Small surprise then, that there is more than a little misconception out there about LEDs.

Why is it worth a look into this now?

Technology is rapidly expanding. And since LEDs are chips, Moore's Law of rapid advancement applied to microprocessors is very likely to work just as well with LEDs. What was true yesterday might not hold today and will surely be irrelevant tomorrow. So let's take stock.

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Are LEDs lasers?

This is worth to clear up for many reasons.
LEDsMagazine, a notable source of reliable information actually toys with the idea that this is not always clear cut. Here: http://ledsmagazine.com/articles/features/2/6/4/1

FACT: the excitement of LEDs is also a source of lasers. 
Q: Does that mean that LEDs are lasers too ... ?
Let's find out.
Let's investigate:
I have been discussing this with some helpful lighting gurus at a tech-head forum at some length at LightNetwork.com.

LED light beam properties ...
There are semiconductor lasers, but a typical LED is NOT a laser. By definition a laser must have coherent beam (meaning similar wavelength and frequency.) Now, most LEDs have incoherent though narrow spectrum beam.

LED diode structure ...
A laser diode has a different silicon structure from a typical LED, even though is uses some of the same principles.

LED standards
Led standards are regional and not yet coordinated even though markets are clearly global. It is easy to pick up a LED on the Web that was manufactured to standards other than ours.

US standards ...
"laser products are covered by Federal Law 21CFR 1040.10 where LED products are excluded. It seems that US standards regard all LEDs as safe and not because thye separates them from LEDs.
However, compliance with [the EU standard] 60825-1 is acceptable.

UK standards ...
When it comes to safety one current influential position is that LEDs and lasers should be treated equal, because: "...the properties of some LEDs are so close to those of lasers that they could be dangerous..."

And further:

"What’s important is the size of the image formed on the retina, since a larger image relates to a lower power density" which I like in particular, because automotive LEDs are typically focussed individually in fairly a narrow beam.

EU standards ...
The most important regulation it seems is "IEC 60825-1. It was published by the International Electrotechnical Commission (IEC), which has been adopted later as EN 60825-1. This standard is commonly known as the Laser Safety Standard"... [and also covers]... "LEDs – at least for now – and treats them as lasers."

Update: LEDs have now been removed from EN 60825. if you are technically inclined, check this out here.
(Pretty sure LEDsMagazine folks will soon update their info on this too :)

However, "Until quite recently, very few people realized there was a legal requirement ...for LED products sold in the EU to be actaully tested according to 60825-1, but awareness ..." is growing.

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A quick conclusion, before we move on...

This is also useful to see how careful we should be with LEDs.
Even though LEDs may not be lasers they might be piercingly bright if not well tuned. Quite unlike any other lamps or light sources you currently use.

The great spectrum debate

FACT: A Nanometer is the measurement of Light Wavelength.

Wide vs narrow spectrum

Narrow spectrum is a light with the strongest light output (called peak) at a certain nanometer point.

The wider the nanometer range where your light source can produce its peak light output the wider spectrum light you have.

Broad vs full spectrum

On the other hand full spectrum is a light if it can mimic day light sun light including but not necessarily both infra red and uv light. Now bright white LED actually actually utilises blue or UV light.

More recently and more often in general terms we talk about broad spectrum if the light source reproduces day light sunlight without but not necessarily both infra red (that is very long wavelength) and uv light (very short wavelength.)

That said, the picture is changing. Broad spectrum and broad angle LEDs WILL hit the market, though not with a break neck speed yet.
  1. Quantum dots from the accidental discovery at Vanderbuilt University promise broad spectrum light in general. The concept will be based on coating, much like current white leds or compact fluorescents.
  2. BivarOpto, the Optoelectronics Division of Bivar, Inc., has 1 Watt LED module that is said to have broad spectrum wavelengths from 465nm to 635nm, and also in white to 8000K color temperature. Viewing angle is fairly wide too -- at 100°. It employs Cree Xlamp technology and an alu PCB base.

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How to best compare LEDs

FACTS: Candela is the measurement of Luminous Intensity.

Lumen is the measurement of Luminous Flux.

1 Lumen divided by 12.566 rougly equals to 1 candlepower (measured as spherical)

HID stands for High Intensity Discharge
Price per lumen

The usual comparison is based on watt per lumen.
However, cost per lumen can be a much more tell-tale comparison.  When we talk about high intensity for LEDs the following is an interesting comparison: High intensity discharge (HID) bulbs can jump one thousand lumens for spending one dollar more. And LEDs not nearly as good. So all things being equal my money is currently on HIDs and not on high intensity LED lighting. (Sorry to say, but true nonetheless.)

Candela / Lumen free calculator:
Luminous intensity: measured in candela
Luminous flux: mesured in lumen
An application (WIN) that will convert candelas to lumens with a reasonable degree of accuracy. Requires vbrun32.dll to be present on your computer - most computers have this .dll already. http://ledmuseum.candlepower.us/second/ledcalc3.zip

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Future Trends

Let's Peek Under the Hood

The future of LED lighting is so bright it is already around.

Related Articles. Resources, Products:
Basics of bright LED diodes

White LED basics is about the role of coatings and light engines.

Organic LED basics is about paper thin, flexible, liquid, rollable, bright, wide angel viewing ... and that's just the start.

Superbright leds put out an awesome brightness for their tiny size

LED Faq will have many of your most frequently asked common questions answered.

LED dimmer problem - external dimmer or propriatory controller?

Very detailed information about laser safety authored by www.hpa.org.uk. Some advanced stuff though!

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Go to Bright Light Emitting Diodes

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