John Doe wrote in
. net:

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.


In your infinite wisdom, how do you explain this?

http://www.cree.com/products/xlamp.asp

NIST confim the brightness, so you don't have to believe the 'hype', you
only have to ask a few basic technical questions: How efficient is it?
Is there enough light to fit purpose at given cost?


"LED luminaires can only be considered high efficacy if the LED can be
tested (according to UL) to be at least 40 lm/W on the line voltage input
side of any power supply or other device.” Otherwise the fixture is not
considered high efficacy."
Source: http://www.icfi.com/Markets/Energy/d...d-lighting.pdf


Light Type: lm/WW CRI Life (hrs)
Incandescent 17 100 3k
Halogen 20 100 10k
Cree XLamp 7090 XR 48 80 50k
T12 flourescent 60 75-85 20k
Metal halide 70 70 20k
Cree XLamp 7090 XR-E 70 80 50k
T8 flourescent 74 75-85 20k
High-pressure sodium 91 22 20k
Low-pressure sodium 120 5 18k
Source: http://www.cree.com/products/pdf/XLamp7090XR-Esheet.pdf

Even if you lose nearly half the light you can still claim high efficiency
to UL standards given the 95% efficient power converters made to run LED
lamps. It would be a poor luminaire that lost that much.

As for actual light output, newer LED's put out 176 lumens or more. That's
still a tad short of what's wanted in many cases, but not by much. 7 to 10
emitters would match a standard 100W incandescent (7 for the 240V type, 10
for the 110V type). Given that the cost of the first CFL's was around £26
in the UK, maybe £40 in todays money, that puts LED's in a good position,
you can get a lot better device for a lot less than that, even now, and
it's improving fast, a lot faster than the time CFL's took to develop, and
there are probably more ways to cut costs without sacrificing safety.

It would take only a fourfold increase in output from a single emitter at
same cost to make them compete with any other light source for domestic
use, and I think we'll only need to wait a few months for that.

"Mr.T" wrote:

"Eeyore" wrote

There are plenty of countries where you'll find an ambient temp close
to 40C. Imagine they want CFLs too.

I imagine they want house cooling too.

LOL !

You need to get out a bit.

Maybe you can tell us exactly which houses have electric lighting and 40degC
temperatures at night.

I didn't say specifically at night.

There are plenty of tropical places where temps are that high. And there are
planty of ppor perolpe whi can't afford air conditioning in such places too.

Graham

Arfa Daily wrote:

"John Doe" wrote in message
"Albert Manfredi" wrote:
wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very
heavily skewed to the blue end of the spectrum in order to get
sufficient brightness, and require multiple LEDs to get even a
minor beam with very poor diffusion.

But you can use a combination of red, green, and blue high intensity
LEDs, to create any variant of "white" that you prefer. From what
Ive read so far, the efficiency of the new high intensity LEDs is
almost identical now to that of CFLs, which means about the same
lumens for 1/4 or 1/5th the power of an equally bright incandescent
bulb.

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.


I have a friend who has LED downlighters as the only source of light in his
shop. They are perfectly bright and adequate for the job, if a little 'cold'
in colour temperature. Also, a local photography shop uses similar ones for
its window display, and again, the only comment you would make is that they
are a little cold. The specifications for up to date ones would certainly
suggest that they are on a par in terms of light output and beamwidth, with
comparable fitting halogens. With a bit of work, I'm sure that they will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast. I
think it might be a case of 'ya gets wot ya pay fer'

The brightest LEDs do unfortunately have that cool blue 7000K or so colour temp.
There's a significant trade off in efficiency for the 3000K ones.

Graham

"Eeyore" wrote in message
...
Maybe you can tell us exactly which houses have electric lighting and
40degC
temperatures at night.

I didn't say specifically at night.

Then as I said, why do they use the lights during the day, rather than
operate some form of cooling?
IF they don't, your argument is totally irrelevant.

There are plenty of tropical places where temps are that high. And there
are
planty of ppor perolpe whi can't afford air conditioning in such places
too.

And plenty who have no electric lighting either, but that has nothing to do
with the claim of 40degC ambient temperature at the light fitting when
operating.
Your whole argument is thus pointless. No real surprise there.

MrT.

"Mr.T" wrote:

"Eeyore" wrote

There are plenty of tropical places where temps are that high. And there
are planty of ppor perolpe whi can't afford air conditioning in such places
too.

And plenty who have no electric lighting either, but that has nothing to do
with the claim of 40degC ambient temperature at the light fitting when
operating.
Your whole argument is thus pointless.

Not at all. What kind of CFLs do you sell in tropical or desert countries ?

Graham

"John Doe" wrote:

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.

Suggest you do some searching he

http://www.ieee.org/web/publications/xplore/index.html

Bert

On Sat, 07 Jul 2007 06:47:31 GMT, John Doe
wrote:

Experience is the best teacher.

Yes. Had someone told you there would be pocket sized radio telephone
equipment in the 50's you might not have believed it.

Agreed LEDs aren't quite there yet, but they are almost there, and
that is pretty exciting stuff. (or at least it is compared to the
LEDs we were using in the early 70's)

Experience with electronics suggests things will get smaller lighter
cheaper and work better over time.

You'd condemn the whole industry, and research effort, because some
charlatan wants to make a quick buck on TV?
--

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

In article ,
John Doe wrote:

"Albert Manfredi" wrote:

wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very
heavily skewed to the blue end of the spectrum in order to get
sufficient brightness, and require multiple LEDs to get even a
minor beam with very poor diffusion.

But you can use a combination of red, green, and blue high intensity
LEDs, to create any variant of "white" that you prefer. From what
Ive read so far, the efficiency of the new high intensity LEDs is
almost identical now to that of CFLs, which means about the same
lumens for 1/4 or 1/5th the power of an equally bright incandescent
bulb.

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.


http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

I'm using 8 of the older Luxeon K2 LEDs in a bicycle light. The output
is nothing short of impressive. It's brilliant at just 5W of input
power. Crank it up to 40W and it puts car headlights to shame.

Kevin McMurtrie wrote:


http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens

No. NOT TYPICAL. That's the highest output (most expensive) grade.
LXML-PWC1-0080
http://www.lumileds.com/pdfs/DS56.pdf


from 700mA @ 3.6V, or 58 lumens per watt.

In 'cool white' i.e, the very blue light with a 6500K colour temp. Not very
suitable for domestic lighting.

More like 95 lumens for a warm white, which works out as 43 lumens/W
http://www.lumileds.com/pdfs/DS56.pdf

Graham

Kevin McMurtrie wrote:

In article ,
John Doe wrote:

"Albert Manfredi" wrote:

wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very
heavily skewed to the blue end of the spectrum in order to get
sufficient brightness, and require multiple LEDs to get even a
minor beam with very poor diffusion.

But you can use a combination of red, green, and blue high intensity
LEDs, to create any variant of "white" that you prefer. From what
Ive read so far, the efficiency of the new high intensity LEDs is
almost identical now to that of CFLs, which means about the same
lumens for 1/4 or 1/5th the power of an equally bright incandescent
bulb.

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.


http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

I'm using 8 of the older Luxeon K2 LEDs in a bicycle light. The output
is nothing short of impressive. It's brilliant at just 5W of input
power. Crank it up to 40W and it puts car headlights to shame.

In article
,
Kevin McMurtrie wrote:
http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

That's poorer efficiency than a CFL can manage. Chances are the colour
temperature is poor too - if tungsten is your norm.

--
*If your feet smell and your nose runs, you're built upside down.

Dave Plowman London SW
To e-mail, change noise into sound.

Kevin McMurtrie wrote:

http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

The colour temperature won't be anywhere near comparable.

In any case don't 'white leds' use the same phosphor method of producing light
that CFLs do ?

Graham

Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

Graham

In article , Eeyore wrote:


Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum, and a fan.
DC drive is nice.

greg

GregS wrote:

Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum, and a fan.
DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting and how much power does that
dissipate ?

Graham

In article , Eeyore wrote:


GregS wrote:

Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active
electronics.
I see no-one ever factors in the power losses that'll be associated with
that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?

Just uses a small CPU fan. I'm actually using a CPU sink/fan combo, but the LED's are epoxied to a copper
plate. I even have diamond dust as a buffer/insulator. To close space the LED's
I needed the best thermal transfer. Did I forget to mention the Peltier device.
I am also using unmounted LED's.


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum,
and a fan.
DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting and how
much power does that
dissipate ?

Nothing is compact. I use a large variable supply. There is 45 watts going to the LED's.
About 20 amps. 3 series sets of LED's. You cannot look at the light.
The device was intended to be flashed in the final form. peaking at about 60 watts.

greg

Eeyore wrote in
:

To run LEDs efficiently from 240V AC will also require some active
electronics. I see no-one ever factors in the power losses that'll be
associated with that.


95% efficient power conversion from 5 to 32V and I think I saw similar
claims for a small module that can power a series chain of LED's from a
mains input. Can't cite a source right now, I just got you one already for
the 176 lumens claim. If I can find the other I'll cite it.

(GregS) wrote in
:

Just uses a small CPU fan. I'm actually using a CPU sink/fan combo,
but the LED's are epoxied to a copper plate. I even have diamond dust
as a buffer/insulator. To close space the LED's I needed the best
thermal transfer. Did I forget to mention the Peltier device.


I can see why diamond dust might help, but why a TEC? The LED's can operate
at temperatures great enough to pour heat through a decent thermal coupling
to a heatsink, no need to pump it through by force, that just makes work
for work's sake unless you are forced to drop the temperature in a confined
space, which is doubtful given the size of heatsink you need to dissipate
LED heat + TEC work heat.

Eeyore wrote in
:

In any case don't 'white leds' use the same phosphor method of
producing light that CFLs do ?


Higher intensity. Might be nonlinear, as in greater efficiency if you pump
them harder. Might be different materials. I don't know for sure though.

Definitely smaller size, so if you're going to be a stickler for full
context such as analysis of lumens per watt of actual mains input, you must
take all of the context. People have alreay said (rightly) that LED lamps
won't have the trouble that CFL's have in fitting most current luminaries.
That's obviously important regarding watse and expense.

Mo LED's are growing more efficient all the time. It might be that in
future these lamps might be directly driven by encapsulated laser diodes
emitting near UV to pump phosphors. Laser diodes have efficiencies beyond
low pressure sodium, they leave it in the dust. It's likely that this
technology will quickly make CFL's look barbarous.

GregS wrote:

Eeyore wrote:
GregS wrote:
Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?

I have one here that's 40mm sq. It still uses 1W.


I'm actually using a CPU sink/fan combo, but the LED's are epoxied to a copper
plate. I even have diamond dust as a buffer/insulator. To close space the LED's
I needed the best thermal transfer. Did I forget to mention the Peltier device.
I am also using unmounted LED's.


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum,
and a fan. DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting and how
much power does that dissipate ?

Nothing is compact. I use a large variable supply.

And the efficiency of that is ?


There is 45 watts going to the LED's.
About 20 amps. 3 series sets of LED's. You cannot look at the light.
The device was intended to be flashed in the final form. peaking at about 60 watts.

So how do you control the LED current ? I imagine you may have current sharing issues with parallel chains
too.

What's the AC input watts ?


Graham

Lostgallifreyan wrote:

Eeyore wrote

In any case don't 'white leds' use the same phosphor method of
producing light that CFLs do ?

Higher intensity. Might be nonlinear, as in greater efficiency if you pump
them harder. Might be different materials. I don't know for sure though.

Definitely smaller size, so if you're going to be a stickler for full
context such as analysis of lumens per watt of actual mains input, you must
take all of the context. People have alreay said (rightly) that LED lamps
won't have the trouble that CFL's have in fitting most current luminaries.

Well actually I wonder about that. Especially replacements for those 'low
voltage halogen' types like these.
http://www.lightingfx.com/item--Halogen-GU10--51

There's not actually any easy way to lose the heat. The 'enclosure' is very
small.


That's obviously important regarding watse and expense.

Mo LED's are growing more efficient all the time. It might be that in
future these lamps might be directly driven by encapsulated laser diodes
emitting near UV to pump phosphors. Laser diodes have efficiencies beyond
low pressure sodium, they leave it in the dust. It's likely that this
technology will quickly make CFL's look barbarous.

I'm not so sure about the quickly bit.

Graham

Eeyore wrote in
:

Definitely smaller size, so if you're going to be a stickler for full
context such as analysis of lumens per watt of actual mains input,
you must take all of the context. People have alreay said (rightly)
that LED lamps won't have the trouble that CFL's have in fitting most
current luminaries.

Well actually I wonder about that. Especially replacements for those
'low voltage halogen' types like these.
http://www.lightingfx.com/item--Halogen-GU10--51

There's not actually any easy way to lose the heat. The 'enclosure' is
very small.


No fair! You try fitting a CFL in there. That's why you're pulling
teeth out of the biting argument in favour of LED's isn't it? Most of the
time in this thread you're advocating CFL's, so this is a spurious issue.

Actually, the Cliften Suspension Bridge in Bristol has its chains entirely
lit by exactly the type of LED-based lamp that replaces little tunsten
halogens. There are three emitters per lamp. The lowest is too high to get
a good look at, but they appear to be Cree or Luxeons in small parabolic
reflectors. Sure, a bridge doesn't have many cooling problems most times,
but those 'chains' are mighty plates of iron, and on summer nights they are
hot. Doesn't stop those lamps working though.

Lostgallifreyan wrote in
:

Cliften Suspension Bridge

That is so embarrasing I have to correct it. 'Clifton'.

Lostgallifreyan wrote:

Eeyore wrote

Definitely smaller size, so if you're going to be a stickler for full
context such as analysis of lumens per watt of actual mains input,
you must take all of the context. People have alreay said (rightly)
that LED lamps won't have the trouble that CFL's have in fitting most
current luminaries.

Well actually I wonder about that. Especially replacements for those
'low voltage halogen' types like these.
http://www.lightingfx.com/item--Halogen-GU10--51

There's not actually any easy way to lose the heat. The 'enclosure' is
very small.


No fair! You try fitting a CFL in there. That's why you're pulling
teeth out of the biting argument in favour of LED's isn't it? Most of the
time in this thread you're advocating CFL's, so this is a spurious issue.

To be honest, I'm not actually advocating any specific technology. I am however
very interested on Philips new compact 'CHLi' halogens.
http://www.lighting.philips.com/gl_e...n_news&lang=en

I have seen LED 'replacements' for that GU10 type touted, but it's clear they
must have very much lower light output.

Graham

Eeyore wrote in
:

To be honest, I'm not actually advocating any specific technology. I
am however very interested on Philips new compact 'CHLi' halogens.
http://www.lighting.philips.com/gl_e...innovations/pr
ess_2006/ecoboost_technology.php?main=global&parent=4390&id =gl_en_news&
lang=en


I'm keen on the developments in halogen lamps too. They have a light
quality I consider second to none. I hope broadband phosphor mixes will be
improved, but they still don't work like a small efficient halogen does.

I need to stop now, want to watch Minder. I need a rest.

In article , Eeyore wrote:


GregS wrote:

Eeyore wrote:
GregS wrote:
Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb,
in
the same sized package, unlike a CFL which has to accommodate the
ballast.

To run LEDs efficiently from 240V AC will also require some active
electronics.
I see no-one ever factors in the power losses that'll be associated with
that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?

I have one here that's 40mm sq. It still uses 1W.


I'm actually using a CPU sink/fan combo, but the LED's are epoxied to a
copper
plate. I even have diamond dust as a buffer/insulator. To close space the
LED's
I needed the best thermal transfer. Did I forget to mention the Peltier
device.
I am also using unmounted LED's.


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper,
aluminum,
and a fan. DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting and
how
much power does that dissipate ?

Nothing is compact. I use a large variable supply.

And the efficiency of that is ?


There is 45 watts going to the LED's.
About 20 amps. 3 series sets of LED's. You cannot look at the
light.
The device was intended to be flashed in the final form. peaking at about 60
watts.

So how do you control the LED current ? I imagine you may have current sharing
issues with parallel chains
too.

What's the AC input watts ?

Not sure, but I am not concerned with efficiency. I am concerned with heat dissapation.
With same batches I have. the individual specs are very close together, so
load distribution is no problem at all. I use a variable voltage/current supply. I
just have to watch to easily move the controls. This is just a test hookup
for now. I am using blue and green colors, they will be strobed to get effects.

A few months ago I bought a batch of cool white 3 watters. I intended to put
some around the house and control them with X10. It
got too complicated with the X10, and I didn't really like the cool white.
The blue LED's are really neat. I have never seen that mystical color temperature
out of LED's before.

In article , Arfa Daily wrote:

"Albert Manfredi" wrote in message
...
wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very heavily
skewed to the blue end of the spectrum in order to get sufficient
brightness, and require multiple LEDs to get even a minor beam with
very poor diffusion.

But you can use a combination of red, green, and blue high intensity LEDs,
to create any variant of "white" that you prefer. From what Ive read so
far, the efficiency of the new high intensity LEDs is almost identical now
to that of CFLs, which means about the same lumens for 1/4 or 1/5th the
power of an equally bright incandescent bulb.

I think we shouldn't get stuck on any supposed problem with CFLs, as if
they are the only alternative here.

The weird thing about LEDs is that they would last such a long time that
they wouldn't need replacement. In principle, you can build them right
into the lamp itself. Or in walls, or whatever.

Bert


The length of service issue with LEDs is very dependant on the way they are
driven, if you are to get the maximum of 100,000 hours plus out of them.
However, that said, even if not driven properly - ie not pulsed - from what
I have read, they are still good for 40k hours, before the light output has
dropped by 50%.

White LEDs do better unpulsed. Used as directed, most are rated for
50,000 hours. The main reason for pulsing LEDs nowadays is to dim them in
a linear manner, such as in variable color fixtures and large video
screens. LEDs often have efficiency and color varying when instantaneous
current is changed, and output and color are often specified only at the
"characterizing current". Different color LEDs have different general
trends in how efficiency varies with current.

As far as colour rendering goes, I agree that this can be
achieved with combinations of RGB LEDs, and I'm sure can be made as good or
better now, as CFLs are ( not that I'm saying theat CFLs are good of course
... !) Just a few days ago, I saw somewhere that one of the manufacturers
has come up with LED chips bonded to a sort of 'ball on a stick' shape, so
many small chips face in virtually every direction around a sphere, to get
over the point-source poor beamwidth issue.

BTW, Philips CFLs = China ? Not any more, it would seem. I picked one up in
the supermarket tonight to have a look. It said " Made in Poland " ...

- Don Klipstein )

In article , Don Pearce wrote:
On Fri, 06 Jul 2007 22:03:44 GMT, "Arfa Daily"
wrote:

"Albert Manfredi" wrote in message
...
wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very heavily
skewed to the blue end of the spectrum in order to get sufficient
brightness, and require multiple LEDs to get even a minor beam with
very poor diffusion.

But you can use a combination of red, green, and blue high intensity LEDs,
to create any variant of "white" that you prefer. From what Ive read so
far, the efficiency of the new high intensity LEDs is almost identical now
to that of CFLs, which means about the same lumens for 1/4 or 1/5th the
power of an equally bright incandescent bulb.

I think we shouldn't get stuck on any supposed problem with CFLs, as if
they are the only alternative here.

The weird thing about LEDs is that they would last such a long time that
they wouldn't need replacement. In principle, you can build them right
into the lamp itself. Or in walls, or whatever.

Bert


The length of service issue with LEDs is very dependant on the way they are
driven, if you are to get the maximum of 100,000 hours plus out of them.
However, that said, even if not driven properly - ie not pulsed - from what
I have read, they are still good for 40k hours, before the light output has
dropped by 50%. As far as colour rendering goes, I agree that this can be
achieved with combinations of RGB LEDs, and I'm sure can be made as good or
better now, as CFLs are ( not that I'm saying theat CFLs are good of course
... !) Just a few days ago, I saw somewhere that one of the manufacturers
has come up with LED chips bonded to a sort of 'ball on a stick' shape, so
many small chips face in virtually every direction around a sphere, to get
over the point-source poor beamwidth issue.

BTW, Philips CFLs = China ? Not any more, it would seem. I picked one up in
the supermarket tonight to have a look. It said " Made in Poland " ...

Arfa

Currently, white LEDs are in fact blue LEDs coated with a fluorescent
substance, so probably the overall light quality will be quite similar
to CFL.

Actually, it's more like that of somewhere between a "cool white" and a
"daylight" old-fashioned fluorescent, with similar color distortions.
There are now some warmer white and higher color rendering index white
LEDs.

- Don Klipstein )

In article , Eeyore wrote:

Arfa Daily wrote:

"John Doe" wrote in message
"Albert Manfredi" wrote:
wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very
heavily skewed to the blue end of the spectrum in order to get
sufficient brightness, and require multiple LEDs to get even a
minor beam with very poor diffusion.

But you can use a combination of red, green, and blue high intensity
LEDs, to create any variant of "white" that you prefer. From what
Ive read so far, the efficiency of the new high intensity LEDs is
almost identical now to that of CFLs, which means about the same
lumens for 1/4 or 1/5th the power of an equally bright incandescent
bulb.

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.

I have a friend who has LED downlighters as the only source of light in his
shop. They are perfectly bright and adequate for the job, if a little 'cold'
in colour temperature. Also, a local photography shop uses similar ones for
its window display, and again, the only comment you would make is that they
are a little cold. The specifications for up to date ones would certainly
suggest that they are on a par in terms of light output and beamwidth, with
comparable fitting halogens. With a bit of work, I'm sure that they will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast. I
think it might be a case of 'ya gets wot ya pay fer'

The brightest LEDs do unfortunately have that cool blue 7000K or so colour temp.
There's a significant trade off in efficiency for the 3000K ones.

They are now getting color temperature as low as mid 4,000's with no
compromise in light output.

- Don Klipstein )

In article , Eeyore wrote:

GregS wrote:

Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum, and a fan.
DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting
and how much power does that dissipate ?

Electronic ballasts for fluorescent lamps (including the ones in all
spiral and most other screw base CFLs) require DC, so require conversion
of AC to DC, and for that matter back to AC of a higher frequency. Many
of those don't have huge losses, in fact usually less loss than iron core
inductive ballasts.

- Don Klipstein )

In , Kevin
McMurtrie wrote:
In article ,
John Doe wrote:

"Albert Manfredi" wrote:

wrote:

Issues with LEDs today:

Color rendering
Diffusion

Once those are solved effectively, they will be excellent
alternatives. My guess is 5 years to color rendering, and 5 more to
diffusion. Most LEDs today filter a single color to a specific
monochromatic output. Even the LED-type flashlights are very
heavily skewed to the blue end of the spectrum in order to get
sufficient brightness, and require multiple LEDs to get even a
minor beam with very poor diffusion.

But you can use a combination of red, green, and blue high intensity
LEDs, to create any variant of "white" that you prefer. From what
Ive read so far, the efficiency of the new high intensity LEDs is
almost identical now to that of CFLs, which means about the same
lumens for 1/4 or 1/5th the power of an equally bright incandescent
bulb.

Don't believe everything you read.

Experience is the best teacher.

In other words, LEDs suck for bright light sources.

However, the hype is good for selling them to fools over the
TV/Internet. Like that one guy selling LED light bulbs on TV (USA). He
doesn't explicitly say that they're bright as a lightbulb, but they
are in a lightbulb package and used in the commercial as if they were
a lightbulb. Some people probably fall for that.

The weird thing about LEDs is that they would last such a long time
that they wouldn't need replacement. In principle, you can build
them right into the lamp itself. Or in walls, or whatever.

Right, but pointless except for low light applications.


http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

145 typical lumens at junction temperature 25 degrees C for the highest
brightness rank in the datasheet. Now, what about with a heatsink
temperature of 35 degrees C and for the highest brightness rank in the
Future Electronics website?

30 watts into these means probably about 25 watts of heat. Hmmm, what
if you mount a dozen of those onto a heatsink the size of the tip and
heating element combined of a 25 watt soldering iron? What would the
heatsink temperature reach then? What does the datasheet say performance
is at that temperature?

With a good size heatsink to stay at a comfortable temperature with 25
watts, I don't see it looking like a universal incandescent or CFL
replacement just yet.

I'm using 8 of the older Luxeon K2 LEDs in a bicycle light. The output
is nothing short of impressive. It's brilliant at just 5W of input
power. Crank it up to 40W and it puts car headlights to shame.

That I believe!

- Don Klipstein )

In article , Eeyore wrote:

Kevin McMurtrie wrote:

http://www.lumileds.com/products/line.cfm?lineId=19

145 Typical lumens from 700mA @ 3.6V, or 58 lumens per watt. The LED is
a surface mount chip 3.1 x 4.6 x 2.1 millimeters in size. A thin strip
of 12 of these chips puts out light comparable to a 100W tungsten lamp
but only uses 30W.

The colour temperature won't be anywhere near comparable.

In any case don't 'white leds' use the same phosphor method of producing light
that CFLs do ?

No, they use a different phosphor made for LEDs. Color rendering of
white LEDs is more like that of "old tech" halophoaphate fluorescents than
like that of CFLs. At least the color rendering index is somewhat better
than that of "old tech cool white".

- Don Klipstein )

In article , Lostgallifreyan wrote:
Eeyore wrote in
:

In any case don't 'white leds' use the same phosphor method of
producing light that CFLs do ?


Higher intensity. Might be nonlinear, as in greater efficiency if you pump
them harder. Might be different materials. I don't know for sure though.

White LEDs are nonlinear, generally with efficiency maximized at some
fraction of rated power.

Definitely smaller size, so if you're going to be a stickler for full
context such as analysis of lumens per watt of actual mains input, you must
take all of the context. People have alreay said (rightly) that LED lamps
won't have the trouble that CFL's have in fitting most current luminaries.
That's obviously important regarding watse and expense.

When an LED or an LED cluster has to dissipate 20 watts of heat, it will
probably have to be bigger than a CFL of same power input.

Mo LED's are growing more efficient all the time. It might be that in
future these lamps might be directly driven by encapsulated laser diodes
emitting near UV to pump phosphors. Laser diodes have efficiencies beyond
low pressure sodium, they leave it in the dust.

There are some high power IR laser diodes more efficienct than LPS.
Other than those, laser diodes are less efficient than most sodium lamps.

Phosphors have a loss. I expect the ultimate in LED efficiency in the
future will have at least some of the light being the radiation produced
by the LED chips, rather than by phosphors.

- Don Klipstein )

"GregS" wrote in message
...
In article , Eeyore
wrote:


GregS wrote:

Eeyore wrote:
GregS wrote:
Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament
bulb,
in
the same sized package, unlike a CFL which has to accommodate the
ballast.

To run LEDs efficiently from 240V AC will also require some active
electronics.
I see no-one ever factors in the power losses that'll be associated
with
that.

When you use up the watts, you get heat. The lamp has to efficiently
get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?

I have one here that's 40mm sq. It still uses 1W.


I'm actually using a CPU sink/fan combo, but the LED's are epoxied to a
copper
plate. I even have diamond dust as a buffer/insulator. To close space
the
LED's
I needed the best thermal transfer. Did I forget to mention the Peltier
device.
I am also using unmounted LED's.


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper,
aluminum,
and a fan. DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting
and
how
much power does that dissipate ?

Nothing is compact. I use a large variable supply.

And the efficiency of that is ?


There is 45 watts going to the LED's.
About 20 amps. 3 series sets of LED's. You cannot look at the
light.
The device was intended to be flashed in the final form. peaking at
about 60
watts.

So how do you control the LED current ? I imagine you may have current
sharing
issues with parallel chains
too.

What's the AC input watts ?

Not sure, but I am not concerned with efficiency. I am concerned with heat
dissapation.
With same batches I have. the individual specs are very close together, so
load distribution is no problem at all. I use a variable voltage/current
supply. I
just have to watch to easily move the controls. This is just a test hookup
for now. I am using blue and green colors, they will be strobed to get
effects.

A few months ago I bought a batch of cool white 3 watters. I intended to
put
some around the house and control them with X10. It
got too complicated with the X10, and I didn't really like the cool white.
The blue LED's are really neat. I have never seen that mystical color
temperature
out of LED's before.

They are changing over the emergency vehicle beacons here in the UK now to
blue LEDs, and as you say, the colour is such a brilliantly intense blue,
that they are far more visible as being emergency vehicles over a much
greater distance, than ever the blue plastic-filtered zenon flashes were.

Arfa

(Don Klipstein) wrote in
:

When an LED or an LED cluster has to dissipate 20 watts of heat, it
will
probably have to be bigger than a CFL of same power input.


Ok, but try thermally coupling a CFL, or any part of one, to a heatsink.
LED's and their drivers are much more easily adapted to use existing
structures to carry the heat away. That's why they can occuppy smaller
volumes. This is actually done, I mentioned the Clifton Suspension Bridge
in another post, that's covered from end to end in them, they're tiny, and
extremely bright, and they use a small metal cowling to carry heat from the
emitters. They're not 20 watts, more like 10, but the total size of the
lamp is similar to a low-volt halogen, far smaller than an 11 watt CFL.

(Don Klipstein) wrote in
:

Phosphors have a loss. I expect the ultimate in LED efficiency in the
future will have at least some of the light being the radiation produced
by the LED chips, rather than by phosphors.


I think so too. And I hope so. Phosphors don't allow colour mixing, and
that's one of the biggest strengths of LED's.

(Don Klipstein) wrote in
:

There are some high power IR laser diodes more efficienct than LPS.
Other than those, laser diodes are less efficient than most sodium lamps.


Ok. I thought more laser diodes were but never mind.. Aren't most class 3B
visible red diodes around 20% efficient or more though? That still leaves a
lot of headroom. Tungsten is often said to be 1% to 2% efficient at making
visible light. So a 100W incandescent 17 l/W at 1% to 2% places the Cree
XR-E's 50+ l/W at 3 times that, up to 6%. These are loose figures but they
suggest that if LED's reach efficiencies like DVD writer diodes, maybe 3 to
4 times the current efficiency can be had. (Not including phosphor losses,
but including LED driver losses). These figures are assuming Imax, 1A per
emitter, if LED's become cheap enough to double the emitter count and drive
each at 500 mA, the efficiency will go up by 50% or more.

Don Klipstein wrote:

Don Pearce wrote:

Currently, white LEDs are in fact blue LEDs coated with a fluorescent
substance, so probably the overall light quality will be quite similar
to CFL.

Actually, it's more like that of somewhere between a "cool white" and a
"daylight" old-fashioned fluorescent, with similar color distortions.
There are now some warmer white and higher color rendering index white
LEDs.

I've yet to see a spectrum published for those 'white' leds. I assume it must be
similar to CFLs.

Graham

Don Klipstein wrote:

Eeyore wrote:

The brightest LEDs do unfortunately have that cool blue 7000K or so colour temp.
There's a significant trade off in efficiency for the 3000K ones.

They are now getting color temperature as low as mid 4,000's with no
compromise in light output.

4500K is still somewhat blue for most peoples' taste.

Graham

Don Klipstein wrote:

Eeyore wrote:
GregS wrote:
Eeyore wrote:
Arfa Daily wrote:

With a bit of work, I'm sure that they [LEDs] will
also get to the point where they can replace a standard filament bulb, in
the same sized package, unlike a CFL which has to accommodate the ballast.

To run LEDs efficiently from 240V AC will also require some active electronics.
I see no-one ever factors in the power losses that'll be associated with that.

When you use up the watts, you get heat. The lamp has to efficiently get
rid of it. May even need a fan.

Quite possibly so. How many watts does the fan need ?


In my experimental 45 watt, 9- 5 watt Luxeon array, I use copper, aluminum, and a fan.
DC drive is nice.

The normal home doesn't have DC. What do you use for current limiting
and how much power does that dissipate ?

Electronic ballasts for fluorescent lamps (including the ones in all
spiral and most other screw base CFLs) require DC, so require conversion
of AC to DC, and for that matter back to AC of a higher frequency. Many
of those don't have huge losses, in fact usually less loss than iron core
inductive ballasts.

I was asking about LED drivers not CFLs.

CFLs already include those losses in their stated power. LED fans only ever quote the DC
input power required for the 'chip'.

Talk about an uneven playing field !

Graham