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'[EE]: LEDs vs Bulbs (was: Bulb Life)'
2001\07\07@104454 by David W. Gulley

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Roman Black wrote:
{Quote hidden}

I do not believe you can just take the 6000mCd output
of a directional LED and assume it is spread over the
sphere.

As I see it,
Assume 6000mCd provided by a LED equally distributed
in a 200 cone from the LED.
If the surface to which the intensity is measured
is 1m from the LED then the total surface illuminated
is approximately 0.098m2.
That is 6 Cd of intensity over an area of 0.098m2.
Therefore, this is 61 lm/m2 or 61 Lux for the LED

Assuming the 60W bulb provides 820 lumens and
does yield a full spherical coverage, then
820/12.57 = 65 lm/m2 or 65 Lux for the bulb

However, the LED is illuminating a much smaller area.
It looks to me that it would take about 135 LEDs to
provide the total lumen output of a 60W bulb!


David W. Gulley
Destiny Designs

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2001\07\07@105717 by David W. Gulley

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This is a repost of my previous message, since the server apparently
removed some of the degree and square symbols I used...

Roman Black wrote:
{Quote hidden}

I do not believe you can just take the 6000mCd output
of a directional LED and assume it is spread over the
sphere.

As I see it,
Assume 6000mCd provided by a LED equally distributed
in a 20degree cone from the LED.
If the surface to which the intensity is measured
is 1m from the LED then the total surface illuminated
is approximately 0.098m(squared).
That is 6 Cd of intensity over an area of 0.098m(squared).
Therefore, this is 61 lm/m(squared) or 61 Lux for the LED

Assuming the 60W bulb provides 820 lumens and
does yield a full spherical coverage, then
820/12.57 = 65 lm/m(squared) or 65 Lux for the bulb

However, the LED is illuminating a much smaller area.
It looks to me that it would take about 135 LEDs to
provide the total lumen output of a 60W bulb!


David W. Gulley
Destiny Designs

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2001\07\07@130503 by Alexandre Domingos F. Souza

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> However, the LED is illuminating a much smaller area.
> It looks to me that it would take about 135 LEDs to
> provide the total lumen output of a 60W bulb!

       But maybe we can use a spherical/parabolical reflector to spread the light, and diffuse it with a white plastic. As the older lamps. Whattadoyathink? :o)



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2001\07\08@011147 by Roman Black

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David W. Gulley wrote:


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Yeah, that's what I was hinting at with the LED "beam"
problem, all their light is very directional. OK, you
could use a parabolic reflector etc, but that would
reduce the light intensity a lot.

I tested a 6000mCd white LED just now, it gives a
very bright 3" spot at 12" distance, and a dim 8"
diameter glow around that. My "guestimation" would
be 90% of its light energy is in that 3" spot.

However, when shone upwards at a white ceiling from
about 24" below, it does give a nice diffuse glow
circle on the ceiling. Big difference between 12"
and 24".

I think you could make some nice up-lights, very
small and unobtrusive on the wall, which throw
a nice pattern of glowing light on the ceiling
and may not be lights to read by, but very usable
for dining rooms or entertainment areas.

Maybe getting a good result is going to be more
an artistic or decorating challenge than an
engineering challenge...
:o)

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2001\07\08@143804 by Mark Newland

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There is a company that already makes LED light bulbs that can be used
as a direct replacment for incandesant bulbs.  Check out the following
page from http://www.ledtronics.com

Roman Black wrote:

{Quote hidden}

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2001\07\08@231235 by Roman Black

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Mark Newland wrote:
>
> There is a company that already makes LED light bulbs that can be used
> as a direct replacment for incandesant bulbs.  Check out the following
> page from http://www.ledtronics.com


Thanks Mark! I saw their LED bulb products
but they look underpowered, hence the calcs.

I am going to order a heap of white 6000mCd
LEDS, do a few "real world" lighting tests and
see what i can come up with. Should be fun.
:o)
-Roman

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2001\07\09@020554 by Bala Chandar

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 Roman Black wrote:

> I am going to order a heap of white 6000mCd
> LEDS, do a few "real world" lighting tests and
> see what i can come up with. Should be fun.

Hi Roman,

Sound very interesting!

As per your normal practice, please inform us in detail through your
site, what you come up with!

When white LEDs become available here in India at affordable prices, I
certainly would like to try my hand at "LED Bulb" projects, taking the
valuable practical hints that you are sure to provide.

Regards,
Bala

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2001\07\09@023543 by Chris Carr

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I saw an Advert for LED Light Bulbs some time ago and since this thread
started I have being trying to find any reference to it. I have finally
decided to be a bit creative in my search (I activated the second brain cell
8-) ). Of course I was starring at the thing all the time.

Go to
http://www.philips.com/indexie4-5.php and click on LED Light Bulbs

you will eventually end up at a joint venture between Agilent and Philips

http://www.lumileds.com/illumination/

Health Warning 8-) You need to be sat down and on Prozac before you enquire
about the price. At the moment they only make economic sense in certain
difficult locations (Auditorium Ceilings) and in High Wage, Over Regulated
Markets (The EU) where the cost of conventional bulb is minuscule in
comparison to the cost of replacing a failed bulb.

On swanning around the lumileds site I notice that they are supplying LED
Taillights for the Cadillac 2000 DeVille, one of the quoted advantages being
they will not need servicing throughout the entire life of the car.

So they are good for one year without failure 8-)

Regards
Chris Carr

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2001\07\09@071822 by Alexandre Domingos F. Souza

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>I saw an Advert for LED Light Bulbs some time ago and since this thread
>started I have being trying to find any reference to it. I have finally
>decided to be a bit creative in my search (I activated the second brain cell
>8-) ). Of course I was starring at the thing all the time.

       Please, do not activate the third (there are 3: input cell, output cell and an interference cell that sits between the other two)


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