LEDs as lamp replacements
 

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote:

Have you never wondered why most prefer the colour temperature of
tungsten
for domestic lighting?

It's not tungsten we prefer, I don't think, but rather a color
temperature that's close to that of a flame. That's what the human race
used for artificial lighting for the very vast majority of its
existence. It shouldn't be surprising that we still find it more comfy
than cold lighting, at night.

My warmest CFLs are now 2700 K. Not bad, but I'd still prefer a little
warmer. The 4100 tube fluorescents we have are not in the least
attractive.

Don Pearce posted this:

Nice chart here

http://www.olympusmicro.com/primer/l...colortemp.html

Candlelight is 2000 K
60W incadescent bulbs are about 2500 K.
100W are slightly cooler, but still well under 3000 K.
Photofloods, which seem quite cool, are around 3500 K.

Nor surprising that something up around 6000 K would be annoying.

Bert

LEDs as lamp replacements
 

LEDs as lamp replacements
 

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in
:

Have you never wondered why most prefer the colour temperature of
tungsten for domestic lighting?


Familiarity, and because it embodies a kind of neat simple magic, a safe
capturing of fire in an idealised form. It's a scientific form that almost
everyone can grasp. It's as iconic as the wheel, it's just not been around
as long.

I guess the truth of 'natural daylight' emulations is that they make people
feel agoraphobic if they can't withdraw from that light. Bring on LED
colour mixing. Or at least a nice emulation of firelight.

LEDs as lamp replacements
 

In article , "Albert Manfredi" wrote:
"Dave Plowman (News)" wrote:

Have you never wondered why most prefer the colour temperature of
tungsten
for domestic lighting?

It's not tungsten we prefer, I don't think, but rather a color
temperature that's close to that of a flame. That's what the human race
used for artificial lighting for the very vast majority of its
existence. It shouldn't be surprising that we still find it more comfy
than cold lighting, at night.

My warmest CFLs are now 2700 K. Not bad, but I'd still prefer a little
warmer. The 4100 tube fluorescents we have are not in the least
attractive.

Most CFL's I have used are too orange for me. I have one of those bargain dollar store
blue ones, and those suck. I bought one at The home Depot many years ago.
paid $20 for a dimmable type. It ended up being the best color I have seen, in my
opinion. They quit selling dimmable lamps. I hate when stores change stocks all
the time, especially Wal Mart.

greg



Don Pearce posted this:

Nice chart here

http://www.olympusmicro.com/primer/l...colortemp.html

Candlelight is 2000 K
60W incadescent bulbs are about 2500 K.
100W are slightly cooler, but still well under 3000 K.
Photofloods, which seem quite cool, are around 3500 K.

Nor surprising that something up around 6000 K would be annoying.

Bert

LEDs as lamp replacements
 

LEDs as lamp replacements
 

In , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

The steepness of that curve alone is enough to make large changes in
output of visible lumens with small changes in voltage.

Yes, quite true. But at full voltage most 120V incandescents 60
watts
or more are about 4.5-8% efficient at converting electricity to
radiation in the 400-700 nm range.

Is this by calculation or measurement? I was hoping you or someone else
would comment on that from experience with it. Those lower figures are so
common that they must have come from somewhere, and not all from looking
only at the strongest wavelength or omitting something in calculation. I've
never seen claims of 6 to 7% for a 100W lightbulb before, and I'm sure I
would if measurements routinely reported it.

They do lots of photometric measurements, while radiometric figures for
incandescents appear to me to be rather rare. More common than actual
measurements I see comments in the direction of "close enough to
blackbody".

http://www.uwsp.edu/cnr/WCEE/keep/Mo...Conversion.htm
says most incandescents are about 5% efficienct

http://www.iiasa.ac.at/Publications/.../IR-04-027.pdf
also gives a 5% figure

Osram says 5% he
http://catalog.osram-os.com/catalogu...do;jsessionid=
337BCEEB510F317E25E607F73C895CFB?act=downloadFile& favOid=
020000020003caf0000100b6

http://www.healthyhomemagazine.ca/light.html
says 4-6%, attributed to someone at Natural Resources Canada.

http://www.eia.doe.gov/kids/energyfa...ingenergy.html
says 10%

http://oikos.com/esb/40/kitlight.html says 10%

10% I find to be a somewhat common figure, though rather optimistic.
Some of those 10% figures may be based on an alternative definition of
visible light as 380-760 nm rather than 400-700 nm.

- Don Klipstein )

LEDs as lamp replacements
 

In , Lostgallifreyan wrote:
(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%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm
range
is around 250 lumens.

places the Cree XR-E's 50+ l/W at 3 times that, up to 6%.

Figure around 250-300 lumens per watt of "white LED light". Looks
like
those achieve about 20%.


Watts of emitted light? I just saw a later post of yours that mentioned
"lumens per visible radiated watt". I think that's why we're discussing
such different values. I'm talking about input watts. I thought we all
were, at least Eeyore certainly was, as that's ultimately watt (haha) is
consumed no matter watt is emitted.

Cree themselves don't claim anything like 250-300 l/W for input watts, at
least not yet, though that might not be long awaiting.

So how does a 100W incandescent look in that context?

I am saying that a watt of white light is about 250 lumens, not the 683
some use as the lumen/watt figure for a 100% efficient light source. A
100% efficient white light source would achieve about 250-300 or so
lumens/watt, depending on what they call "white".

Most of those generating figures of incandescents being 1-2% efficient
are assuming that they would achieve 683 lumens/watt if they were 100%
efficient.

- Don Klipstein )

LEDs as lamp replacements
 

In article ,
Albert Manfredi wrote:
Have you never wondered why most prefer the colour temperature of
tungsten
for domestic lighting?

It's not tungsten we prefer, I don't think, but rather a color
temperature that's close to that of a flame.

Err, isn't that what I wrote? It's the colour temperature that matters
rather than the source.

--
*Some days you're the dog, some days the hydrant.

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

LEDs as lamp replacements
 

LEDs as lamp replacements
 

In , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

In , Lostgallifreyan
wrote:
(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%

More like 6-7%. Each watt of tungsten radiation in the 400-700 nm
range
is around 250 lumens.

places the Cree XR-E's 50+ l/W at 3 times that, up to 6%.

Figure around 250-300 lumens per watt of "white LED light". Looks
like
those achieve about 20%.


Watts of emitted light? I just saw a later post of yours that
mentioned "lumens per visible radiated watt". I think that's why we're
discussing such different values. I'm talking about input watts. I
thought we all were, at least Eeyore certainly was, as that's
ultimately watt (haha) is consumed no matter watt is emitted.

Cree themselves don't claim anything like 250-300 l/W for input watts,
at least not yet, though that might not be long awaiting.

So how does a 100W incandescent look in that context?

I am saying that a watt of white light is about 250 lumens, not the
683
some use as the lumen/watt figure for a 100% efficient light source.
A 100% efficient white light source would achieve about 250-300 or so
lumens/watt, depending on what they call "white".

Most of those generating figures of incandescents being 1-2%
efficient
are assuming that they would achieve 683 lumens/watt if they were 100%
efficient.

- Don Klipstein )


Ok, I see that lumens depend on the spectrum, not just the actual visible
watts emitted, but given that there is convection in an incandescent lamp
that makes some of its power emit in the IR, does enough leave that way to
bring the lumens per input watts down to levels that can account for stated
line-power-to-light efficiences of 3% and lower?

Most of the output of an incandescent is IR.

I think when Cree talk of lumens per watt, they're talking of lumens for
each watt of electrical input, and that's how I want to make the
comparison.

I was only mentioning figures of lumens per watt of visible light output
to explain that an incandescent achieving 17.1 lumens per input watt is
nearly 7% efficient.

Put 100 watts into an incandescent that chieves 17.1 lpw. You get 1710
lumens. Each lumen is about 1/250 watt of "white light", not the 1/683
watt assumed by those claiming incandescents are only 1-2% efficient.

- Don Klipstein )

LEDs as lamp replacements
 

On Wed, 11 Jul 2007 15:10:28 +0000 (UTC) in sci.electronics.basics,
(Don Klipstein) wrote,
Personally, I like more like 3500K at most brighter indoor lighting
levels, closer to 3,000 for dimmer indoor lighting.

Higher color temperature often appears "dreary" unless illumination
level is very high.

Do you put orange gels on your windows?

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote:

Albert Manfredi wrote:

It's not tungsten we prefer, I don't think, but rather a color
temperature that's close to that of a flame.

Err, isn't that what I wrote? It's the colour temperature that matters
rather than the source.

Well, you wrote may things, including this:

"Lighting which is used to replace daylight - like that most of us have
at home for use when daylight fades - ideally shouldn't give such a
sudden change in temperature that it is noticeable. In the same way as
lighting used to supplement daylight - like in say an office - should
also be an approximate match to that daylight. It's common sense,
really."

I do agree that if we are supplementing daylight, e.g. in work spaces
with large windows during the day, rather than providing lighting at
night, a cooler light (hotter temp) is probably preferable. But for
night time lighting, I think what we are looking for is the color of
flame.

I'm saying, it's not that we are conditioned to the color of tungsen,
it's that we are looking for something close to 2000 K at night. Much
cooler cooler light than that (higher temp) is stark and generally
unpleasant.

By the way, this also applies to xenon headlights in some cars. They are
superbly obnoxious at night, to other drivers. Even if they aren't
brighter than halogens, the bluish color is very distracting.
Fortnunately, there seem to be fewer of the really annoying ones around
these days. Maybe the auto makers got too many complaints.

Bert

LEDs as lamp replacements
 

LEDs as lamp replacements
 

In article , David Harmon wrote:
On Wed, 11 Jul 2007 15:10:28 +0000 (UTC) in sci.electronics.basics,
(Don Klipstein) wrote,
Personally, I like more like 3500K at most brighter indoor lighting
levels, closer to 3,000 for dimmer indoor lighting.

Higher color temperature often appears "dreary" unless illumination
level is very high.

Do you put orange gels on your windows?

No, I don't.

But if the light level is neither in kilolux nevels nor a recent uptick
from something lower, I find daylight to usually have no warmth or "cheer".

If the ceiling is dark but the windows are bright, then things can look
cheerful - sometimes - for some reason.

- Don Klipstein )

LEDs as lamp replacements
 

"Albert Manfredi" wrote in
:

I'm saying, it's not that we are conditioned to the color of tungsen,
it's that we are looking for something close to 2000 K at night. Much
cooler cooler light than that (higher temp) is stark and generally
unpleasant.


It is conditioning, but it's worth thinking about what the conditioning is.

First, how can a hotter temperature be cold?? The only way to account for
that is to look at the environment. Blue sky accepts radiant heat from the
earth so nights chill faster on clear evenings, pale light from the moon or
stars accompanies those same conditions within hours, and those sources are
so pale that we have scotopic vision to cope with them.

The whole thing is based on comfort. There is one exception to the usual
perception of cool faint lights. The whole midsummer night's dream idyll is
based on this, the almost magical inversion that allows a warm night to
make perception of these 'cold' lights seem something other than
threatening to our health.

I bet we could get used to 'cold' light plenty fast so long as we weren't
actually cold ourselves. Conversely, Dickens and many others have commented
on the bleakness of a small flame when there isn't enough heat to warm the
people who need it. It really has to do with our ambient conditions, not
direct colour perceptions at all.

LEDs as lamp replacements
 

In , Lostgallifreyan wrote:
(Don Klipstein) wrote in
:

Ok, I see that lumens depend on the spectrum, not just the actual
visible watts emitted, but given that there is convection in an
incandescent lamp that makes some of its power emit in the IR, does
enough leave that way to bring the lumens per input watts down to
levels that can account for stated line-power-to-light efficiences of
3% and lower?

Most of the output of an incandescent is IR.

What I meant was, might more heat be carried away by the convection in the
argon fill, and be either conducted or radiated away at far longer
wavelengths? I mentioned convection specifically to be clear I'm not
talking about directly radiated energy.

As far as I understand what goes on there, around 10-15 watts is
convected from the filament in a 100 watt "USA-usual" "standard" A19.

I think when Cree talk of lumens per watt, they're talking of lumens
for each watt of electrical input, and that's how I want to make the
comparison.

I was only mentioning figures of lumens per watt of visible light
output
to explain that an incandescent achieving 17.1 lumens per input watt
is nearly 7% efficient.

Put 100 watts into an incandescent that chieves 17.1 lpw. You get
1710
lumens. Each lumen is about 1/250 watt of "white light", not the
1/683 watt assumed by those claiming incandescents are only 1-2%
efficient.

I've managed unintentionally to get you to say that three times now. :)

I'm not always quick on the uptake, but I try... what I'm getting at, is
can any other evaluation result in that lower figure? I'm not convinced
that taking only the lumens at 555 nm accounts for this. Lumens seem
slippery enough if they depend on spectra and photopic sensitivity anyway.

Wikipedia again:
"In photometry, luminous flux or luminous power is the measure of the
perceived power of light. It differs from radiant flux, the measure of the
total power of light emitted, in that luminous flux is adjusted to reflect
the varying sensitivity of the human eye to different wavelengths of
light."

I believe some who are not aware that the lumen is a unit of luminous
and not radiant flux, or not aware of visible wavelengths other than 555
nm having less than 683 lumens per watt, divided a lumen/watt efficacy
figure by 683 to come up with incandescents being only 1-2% or 2.6%
efficient.

I guess that much can be relied on. So try it this way:

Take a 100W incandescent, and a large ellipsoidal mirror to gather as much
of its radiant flux as you can, throwing it to the other focus of the
ellipse where a black painted thermopile awaits. The incoming light is
passed through a dichroic filter at 700 nm to send the IR elsewhere and
pass only the visible light to the thermopile. Assuming you get close to
ideal light gathering for the visible wavelengths (and IR rejection), how
many watts will be read from the thermopile?

I expect about 6.7 watts in the case of a 1710 lumen 100W incandescent,
if the ellipsoidal mirror is a whole ellipsoid and 100% reflective and the
dichroic filter passes all 400-700 nm light.

As for the rest, approximately or "educated guesses":

UV passing through the glass: .12%
UV absorbed by the glass: .02%

Heat conducted/convected from the filament: ~13%

IR passing through the glass: ~60%
IR absorbed by the glass: ~20.16% ("rounded oddly" to make figures add to
100%)

I understand that photometric measurements abount, and radiometric ones are
rarer, but that's what I want to look at, as without that grounding the
rest seems most insecure.

- Don Klipstein )

LEDs as lamp replacements
 

LEDs as lamp replacements
 

LEDs as lamp replacements
 

"Lostgallifreyan" wrote in message
...
(Don Klipstein) wrote in
:

I expect about 6.7 watts in the case of a 1710 lumen 100W
incandescent,
if the ellipsoidal mirror is a whole ellipsoid and 100% reflective and
the dichroic filter passes all 400-700 nm light.

As for the rest, approximately or "educated guesses":

UV passing through the glass: .12%
UV absorbed by the glass: .02%

Heat conducted/convected from the filament: ~13%

IR passing through the glass: ~60%
IR absorbed by the glass: ~20.16% ("rounded oddly" to make figures add
to 100%)


I was trying to keep the lumens out of this entirely, but I'll buy it. :)
It makes me wonder what the fuss is about actually. While it's better to
get more efficiency, it seems that incandescents aren't so bad we need to
consider banning them, we just need to think more about what source we use
for a given task. As for the case to ban all but halogen types, how much
might be gained? With IR reflection to make them keep the tungsten hotter
for a given input, we get more light, but even so, is there that much
difference? Enough to say that they stay and standard incandescents go?

If LED's ever get a spectral match for a small efficient low-volt halogen,
at least the choice will be easy.

OK, I'm following all this - just about, I think. So let me now throw in a
slightly new set of questions. Back to LED halogen substitutes. Some
distance back up the thread, consideration was being given to losses in the
control circuitry for the LEDs. So, the first question is, just exactly how
are these things ballasted ? The reason that I ask this is that I was in an
electrical cash and carry warehouse tonight, and I picked up a couple of
LED-based GU10 replacements to have a look at. I didn't count the actual
LEDs, but I'm guessing at about 15 or so - let's say 15. Let's also say that
they are bluish types and let's guess at a forward drop of 4 volts. With
them all in series, that's going to be around 60v DC that's needed to run
them.

Now, these lamps were of exactly the same dimensions as a standard GU10
lamp, with the same 'nail head' pins, set in the identical ceramic base.
240v AC rating, stated on the packet. The glass 'cone' was exactly the same
as on a standard GU10, and it appeared, as far as I could see, that for the
most part, it was filled with the LEDs, which looked like 5mm types, and
their support plate. So that leaves very little space for any drive
electronics - certainly not a switch mode PSU, or even for a smoothing cap
on the end of a simple reccy / resistor combination. Not that there would
have been room even, for a resistor of a sufficient power rating to handle
this kind of drop.

Next question. There were two types on offer, one rated at 1 watt, and one
at 1.3 watts, both with a quoted lifetime of 50k hours. So what exactly is
being said here ? Is that 1 watt input from the mains supply, or 1 watt used
by the LEDs or 1 watt of visible luminous output power ? A website that I
looked at quoted the output of a 0.62 watt one, at 20-30 l - I'm assuming
that to be 'lumens'. If correct, and not a misprint, that seems to be a
piddling amount compared to the 950 lumens quoted for an incandescent 240v
50 watt GU10, and yet the text suggests that they are only 'slightly
dimmer'. It also says that these lamps give off almost no heat, and that
they consume only around 10% of the energy of a conventional equivalent
halogen GU10. So for a 50 watt type, that's about 5 watts, suggesting that
around 4 watts is lost in ballasting ??

Setting aside the issues of colour temperature and CRI, which I am sure will
shortly be overcome, it seems to me that these halogen replacement lamps are
even now on their way to bettering CFLs in that they are already exactly the
same pattern as the lamps that they are replacing, so must have sorted the
ballasting problem. And yet there are no plans to phase out the incandescent
version. This flies directly in the face of the proposals to ban standard
incandescents, when the advocated replacement technology (CFLs) is far from
being a satisfactory replacement, on several counts.

Arfa

LEDs as lamp replacements
 

"Albert Manfredi" wrote in message
...
"Dave Plowman (News)" wrote:

Albert Manfredi wrote:

It's not tungsten we prefer, I don't think, but rather a color
temperature that's close to that of a flame.

Err, isn't that what I wrote? It's the colour temperature that matters
rather than the source.

Well, you wrote may things, including this:

"Lighting which is used to replace daylight - like that most of us have at
home for use when daylight fades - ideally shouldn't give such a sudden
change in temperature that it is noticeable. In the same way as lighting
used to supplement daylight - like in say an office - should also be an
approximate match to that daylight. It's common sense, really."

I do agree that if we are supplementing daylight, e.g. in work spaces with
large windows during the day, rather than providing lighting at night, a
cooler light (hotter temp) is probably preferable. But for night time
lighting, I think what we are looking for is the color of flame.

I'm saying, it's not that we are conditioned to the color of tungsen, it's
that we are looking for something close to 2000 K at night. Much cooler
cooler light than that (higher temp) is stark and generally unpleasant.

By the way, this also applies to xenon headlights in some cars. They are
superbly obnoxious at night, to other drivers. Even if they aren't
brighter than halogens, the bluish color is very distracting.
Fortnunately, there seem to be fewer of the really annoying ones around
these days. Maybe the auto makers got too many complaints.

Bert


Don'cha just hate the way they swing from blue through stark white to green,
when they come round a bend in front or behind you ... Also, having sat
behind some, the perceived ability to light the road, does not seem to be
any better than halogens, which may again come down to colour temperature
and the human vision comfort zone.

Arfa

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in message
...
That's more to do with the relative sensitivity of film color layers
etc.
They are specifically balanced for Daylight or Tungsten, and are wildly
innacurate when used with the wrong light source.

In which way are they 'inaccurate'? They will look wrong to the eye on a
'cut' but as with real life if all shots are matched the eye will
accommodate.

Not so. They ARE wrong. The relative densities of the individual film layers
will be quite innacurate when exposed with the wrong light.

The monitor you're reading this on is unlikely to match
*exactly* another one in colour temperature but will look ok to the
individual. The eye compensates, as I said, as it must do given that
daylight changes. Unless it has a reference to match to.

Which is everything else within your field of view. Only if *everything*
changes will the *brain* correctly compensate.

Err, yes. That's what I said. But it doesn't react instantly. Hence it
notices a sudden change in colour temperature. Like switching on 4500K
lights in a house when it gets dark.;-)

So a couple of minutes readjustment is abhorent to you?
Doesn't bother me too much.

Have you never wondered why most prefer the colour temperature of tungsten
for domestic lighting?

No, as I already stated it was simply conditioning from fires, candles, oil
lamps and tungsten filament globes.
Have you ever wondered why people aren't bothered by the change from
daylight, or in fact are able to wear coloured sun glasses, but can readily
pick an off balance color photo?

MrT.

LEDs as lamp replacements
 

"Don Klipstein" wrote in message
...
Moonlight's color temperature at its highest is about 4000.

I haven't seen a reference for this, but even assuming it is so, it's still
higher than many people here prefer it would seem.

Meanwhile, at illumination level so low that color vision does not work
well, color temperature matters less. At illumination levels an order of
magnitude or two or three above that of moonlight, most people like it
warm (lower color temperature).

Which is my point. People simply prefer something, then try to introduce
pseudo scientific rationalisation to claim anybody who disagrees with them
is wrong.

MrT.

LEDs as lamp replacements
 

In article , Mr.T wrote:

"Dave Plowman (News)" wrote in message
...
That's more to do with the relative sensitivity of film color layers
etc.
They are specifically balanced for Daylight or Tungsten, and are wildly
innacurate when used with the wrong light source.

In which way are they 'inaccurate'? They will look wrong to the eye on a
'cut' but as with real life if all shots are matched the eye will
accommodate.

Not so. They ARE wrong. The relative densities of the individual film layers
will be quite innacurate when exposed with the wrong light.

The monitor you're reading this on is unlikely to match
*exactly* another one in colour temperature but will look ok to the
individual. The eye compensates, as I said, as it must do given that
daylight changes. Unless it has a reference to match to.

Which is everything else within your field of view. Only if *everything*
changes will the *brain* correctly compensate.

Err, yes. That's what I said. But it doesn't react instantly. Hence it
notices a sudden change in colour temperature. Like switching on 4500K
lights in a house when it gets dark.;-)

So a couple of minutes readjustment is abhorent to you?
Doesn't bother me too much.

Have you never wondered why most prefer the colour temperature of tungsten
for domestic lighting?

No, as I already stated it was simply conditioning from fires, candles, oil
lamps and tungsten filament globes.
Have you ever wondered why people aren't bothered by the change from
daylight, or in fact are able to wear coloured sun glasses, but can readily
pick an off balance color photo?

An off-balance color photo has its surroundings as a color reference.
It would be like having colored sunglasses coloring only a small portion
of your field of vision.

- Don Klipstein )

LEDs as lamp replacements
 

"Don Klipstein" wrote in message
...
Unless it has a reference to match to.

Which is everything else within your field of view.

snip

An off-balance color photo has its surroundings as a color reference.

Which is what I said already. That was my point.

MrT.

LEDs as lamp replacements
 

"Mr.T" MrT@home wrote in
u:

Moonlight's color temperature at its highest is about 4000.

I haven't seen a reference for this, but even assuming it is so, it's
still higher than many people here prefer it would seem.


Nice way to test: Take a camera and tripod, do a long exposure shot of a
moonlit scene. Then view the phtot on a monitor in a context you know. I
haven't done this but I think it will bear out the claim that the moon's
light is brownish, as it looks when you look directly at it. The blue comes
from a combination of scattered light and scotopic sensitivity to the blue
part of its spectrum.

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in
message
In article ,
Albert Manfredi wrote:
Have you never wondered why most prefer the colour
temperature of tungsten
for domestic lighting?

It's not tungsten we prefer, I don't think, but rather a
color temperature that's close to that of a flame.

Err, isn't that what I wrote? It's the colour temperature
that matters rather than the source.

There many kinds of preferences. One is the preference for that which is
traditional and familiar, and another is the preference for that which is
most effective for the purpose at hand.

I've found that if the goal is reading accurately with limited light, then
higher temperatures even 5000 degrees and up, can be preferable. I've read
far into many a dark fall or winter evening in a tent, using a pretty blue
LED headlamp.

I did some tests of people reading Bibles and hymnals which tend to small
print, in a congregational setting with fairly high light levels, and found
that my readers were most comfortable with color temperatures in the 3200
degree range.

I suspect that preferences for color temperatures below 3200 degrees are
heavily influenced by tradition and past experience.

LEDs as lamp replacements
 

"Arny Krueger" wrote in
:

"Dave Plowman (News)" wrote in
message
In article ,
Albert Manfredi wrote:
Have you never wondered why most prefer the colour
temperature of tungsten
for domestic lighting?

It's not tungsten we prefer, I don't think, but rather a
color temperature that's close to that of a flame.

Err, isn't that what I wrote? It's the colour temperature
that matters rather than the source.

There many kinds of preferences. One is the preference for that which
is traditional and familiar, and another is the preference for that
which is most effective for the purpose at hand.

I've found that if the goal is reading accurately with limited light,
then higher temperatures even 5000 degrees and up, can be preferable.
I've read far into many a dark fall or winter evening in a tent, using
a pretty blue LED headlamp.

I did some tests of people reading Bibles and hymnals which tend to
small print, in a congregational setting with fairly high light
levels, and found that my readers were most comfortable with color
temperatures in the 3200 degree range.

I suspect that preferences for color temperatures below 3200 degrees
are heavily influenced by tradition and past experience.





Yes. Been saying similar stuff here last night. Also, quite apart from
preference and convention and all that, there is a stark fact that we use
shortwave light to resolve fine detail without strain. That's a basic
physical fact. So it makes NO sense at all to suggest that reading is best
done in a low colour temperature. Same goes for any other detailed small
scale activity such as most indoor hobbies involve.

The only reason we need bright incandescent to read by is that it is the
ONLY way we can get enough shortwave light. I've found that so long as you
have a decent continuum such as the newer Cree Xlamps have, and a tint that
favours the long end, such as the WG tint, you can be comfortable with much
lower lumen counts than when using low colour temperatures. This is exactly
what many here said was 'dreary' or similar, but I tried it last night. I
went outside to see the orange light in the clouds over the city, the many
tungsten lamps all around in windows, waited till I was thoroughly
adjusted, then went inside. Far from looking dreary, it was invitingly
bright and easy to see things by, and this was ONE single emitter aimed at
the ceiling. It had the same cosy quality that a pressurised paraffin
(kerosene) lamp has in a country kitchen during a power cut. I remember
that well enough, and this new light was similarly pleasing, if a little
different, sharper perhaps.

LEDs as lamp replacements
 

In article ,
Mr.T MrT@home wrote:

"Dave Plowman (News)" wrote in message
...
That's more to do with the relative sensitivity of film color layers
etc.
They are specifically balanced for Daylight or Tungsten, and are
wildly innacurate when used with the wrong light source.

In which way are they 'inaccurate'? They will look wrong to the eye on
a 'cut' but as with real life if all shots are matched the eye will
accommodate.

Not so. They ARE wrong. The relative densities of the individual film
layers will be quite innacurate when exposed with the wrong light.

You conveniently snipped the part about video. And a daylight film can
also look 'wrong' when taken in daylight of the wrong colour temperature.
Which can be corrected by filters when taking the pic or processing it.

The monitor you're reading this on is unlikely to match
*exactly* another one in colour temperature but will look ok to the
individual. The eye compensates, as I said, as it must do given that
daylight changes. Unless it has a reference to match to.

Which is everything else within your field of view. Only if *everything*
changes will the *brain* correctly compensate.

Not so - do you change the colour temperature of your TV or monitor
according to the ambient light? The brain focuses on the important part
after time - within reason.

Err, yes. That's what I said. But it doesn't react instantly. Hence it
notices a sudden change in colour temperature. Like switching on 4500K
lights in a house when it gets dark.;-)

So a couple of minutes readjustment is abhorent to you?
Doesn't bother me too much.

Fine - but you're in a minority if you like cold domestic lighting.

Have you never wondered why most prefer the colour temperature of
tungsten for domestic lighting?

No, as I already stated it was simply conditioning from fires, candles,
oil lamps and tungsten filament globes.

Fluorescent lights have been around for a long, long time. And early ones
were all cold compared to tungsten. People could easily have got used to
them for domestic light, but very few chose to.

Have you ever wondered why people aren't bothered by the change from
daylight, or in fact are able to wear coloured sun glasses, but can
readily pick an off balance color photo?

Can they? Depends on their skills. Have you never noticed how many people
are happy with a TV where the grey scale is miles out?

--
*Sometimes I wake up grumpy; Other times I let him sleep.

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

LEDs as lamp replacements
 

In article ,
Arny Krueger wrote:
I suspect that preferences for color temperatures below 3200 degrees are
heavily influenced by tradition and past experience.

Perhaps if it were only working light. But at home it's usually comfort
light.

--
*Who is this General Failure chap anyway - and why is he reading my HD? *

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

LEDs as lamp replacements
 

"Arfa Daily" wrote in
:

I could see, that for the most part, it was filled with the LEDs,
which looked like 5mm types, and their support plate. So that leaves
very little space for any drive electronics - certainly not a switch
mode PSU, or even for a smoothing cap on the end of a simple reccy /
resistor combination. Not that there would have been room even, for a
resistor of a sufficient power rating to handle this kind of drop.


There might.. First, it needs to control a fixed current, and an efficient
power converter can be tiny, flat, like this: http://tinyurl.com/ypenut
That's 95% efficient at converting voltage ranging from 5~32 VDC into a
current source that can manage up to 7 LED's in series. A converter from
240 VAC to low volt DC can be had with similar efficiency (I hope), to feed
what I already have. Ideally I can find a single module that does the
entire power conversion at 95% or better.

Next question. There were two types on offer, one rated at 1 watt, and
one at 1.3 watts, both with a quoted lifetime of 50k hours. So what
exactly is being said here ? Is that 1 watt input from the mains
supply, or 1 watt used by the LEDs or 1 watt of visible luminous
output power ? A website that I looked at quoted the output of a 0.62
watt one, at 20-30 l - I'm assuming that to be 'lumens'. If correct,
and not a misprint, that seems to be a piddling amount compared to the
950 lumens quoted for an incandescent 240v 50 watt GU10, and yet the
text suggests that they are only 'slightly dimmer'. It also says that
these lamps give off almost no heat, and that they consume only around
10% of the energy of a conventional equivalent halogen GU10. So for a
50 watt type, that's about 5 watts, suggesting that around 4 watts is
lost in ballasting ??


That one sounds like a marketing hype. The first thing is that it has lots
of standard 5mm LED's. Avoid like the PLAGUE, seriously. All that voltage
drop, and no cooling to speak off, what kind of thermal coupling can be had
for a 5mm LED?

The ones to look for are the Cree and Luxeon types. The easiest way to look
for them is a single emitter, or at least very few of them, with high
output claims. Look into one (unlit!, they WILL damage your eyes if you do
that to lit ones at close range), amd you'll see a distinctive fluorecent
dayglo green yellow cast to the phosphor unlike the chalky phosphors of
weaker white LED's.

Re wattage claims, it's hard to say, without evaluating all the evidence
you can find together. In short, a lamp that needs several emitters to
manage 30 lumens is a joke, when you can cheaply get a single emitter that
puts out 200 lumens with 1 amp pushed through a voltage drop of around 3
volts.

Setting aside the issues of colour temperature and CRI, which I am
sure will shortly be overcome, it seems to me that these halogen
replacement lamps are even now on their way to bettering CFLs in that
they are already exactly the same pattern as the lamps that they are
replacing, so must have sorted the ballasting problem. And yet there
are no plans to phase out the incandescent version. This flies
directly in the face of the proposals to ban standard incandescents,
when the advocated replacement technology (CFLs) is far from being a
satisfactory replacement, on several counts.


I think the ban is 'being seen to be done' kind of reaction. It's got more
to do with trashing an icon known for inefficiency, but there are better
ways to make people change than all-stick-no-carrot.

If governments really want to reduce power consumption I think they should
be subsidising the public to buy computer mainboards based on Nehemiah
CPU's and such. Turning a domestic computer into a fan heater just to run
Windows Vista as a private office is a sick joke! Far more worrying than a
few lightbulbs.

LEDs as lamp replacements
 

"Dave Plowman (News)" wrote in
:

Have you never noticed how many people
are happy with a TV where the grey scale is miles out?


Actually that kind of refutes a point that many including you claim. People
WERE happy for the most part with b/w TV's when that's all they had, and
with colour they liked a sharp clean white and a bright vivid image, and
they were happy, and they'd even fall asleep in front of them with the
other lights out, at times, it's an iconic movie thing, often seen, often
shared. Funny behaviour don't you think, given the high colour temperatures
involved?


People tell themselves they don't like stuff the way kids tell themselves
they don't like their greens, or the way they tell themselves they need
heavy clothes on winter days even when those days are warmer and drier than
many summer ones. They even tell themselves that what they read in the
newspapers must be true.

Back to lights: I refer again to the point that reading and detailed indoor
hobbies need shortwave light to avoid eye strain, and the only reason
people turn up the tungsten is because that's the only way they actually
get enough of the shortwave light they need.

LEDs as lamp replacements
 

"Lostgallifreyan" wrote in message
...
"Arfa Daily" wrote in
:

I could see, that for the most part, it was filled with the LEDs,
which looked like 5mm types, and their support plate. So that leaves
very little space for any drive electronics - certainly not a switch
mode PSU, or even for a smoothing cap on the end of a simple reccy /
resistor combination. Not that there would have been room even, for a
resistor of a sufficient power rating to handle this kind of drop.


There might.. First, it needs to control a fixed current, and an efficient
power converter can be tiny, flat, like this: http://tinyurl.com/ypenut
That's 95% efficient at converting voltage ranging from 5~32 VDC into a
current source that can manage up to 7 LED's in series. A converter from
240 VAC to low volt DC can be had with similar efficiency (I hope), to
feed
what I already have. Ideally I can find a single module that does the
entire power conversion at 95% or better.

Next question. There were two types on offer, one rated at 1 watt, and
one at 1.3 watts, both with a quoted lifetime of 50k hours. So what
exactly is being said here ? Is that 1 watt input from the mains
supply, or 1 watt used by the LEDs or 1 watt of visible luminous
output power ? A website that I looked at quoted the output of a 0.62
watt one, at 20-30 l - I'm assuming that to be 'lumens'. If correct,
and not a misprint, that seems to be a piddling amount compared to the
950 lumens quoted for an incandescent 240v 50 watt GU10, and yet the
text suggests that they are only 'slightly dimmer'. It also says that
these lamps give off almost no heat, and that they consume only around
10% of the energy of a conventional equivalent halogen GU10. So for a
50 watt type, that's about 5 watts, suggesting that around 4 watts is
lost in ballasting ??


That one sounds like a marketing hype. The first thing is that it has lots
of standard 5mm LED's. Avoid like the PLAGUE, seriously. All that voltage
drop, and no cooling to speak off, what kind of thermal coupling can be
had
for a 5mm LED?

The ones to look for are the Cree and Luxeon types. The easiest way to
look
for them is a single emitter, or at least very few of them, with high
output claims. Look into one (unlit!, they WILL damage your eyes if you do
that to lit ones at close range), amd you'll see a distinctive fluorecent
dayglo green yellow cast to the phosphor unlike the chalky phosphors of
weaker white LED's.

Re wattage claims, it's hard to say, without evaluating all the evidence
you can find together. In short, a lamp that needs several emitters to
manage 30 lumens is a joke, when you can cheaply get a single emitter that
puts out 200 lumens with 1 amp pushed through a voltage drop of around 3
volts.

Setting aside the issues of colour temperature and CRI, which I am
sure will shortly be overcome, it seems to me that these halogen
replacement lamps are even now on their way to bettering CFLs in that
they are already exactly the same pattern as the lamps that they are
replacing, so must have sorted the ballasting problem. And yet there
are no plans to phase out the incandescent version. This flies
directly in the face of the proposals to ban standard incandescents,
when the advocated replacement technology (CFLs) is far from being a
satisfactory replacement, on several counts.


I think the ban is 'being seen to be done' kind of reaction. It's got more
to do with trashing an icon known for inefficiency, but there are better
ways to make people change than all-stick-no-carrot.

If governments really want to reduce power consumption I think they should
be subsidising the public to buy computer mainboards based on Nehemiah
CPU's and such. Turning a domestic computer into a fan heater just to run
Windows Vista as a private office is a sick joke! Far more worrying than a
few lightbulbs.

I don't have a problem with a switch mode converter being small - just with
the front end to get from 240v AC down to some realistic DC level, also
being small. I work with switch mode power supplies of every size on a daily
basis, but I've yet to see the front-end electrolytic, which would fit in
any space that was closed in so that you couldn't see it, on one of those
GU10-s.

As far as 5mm LEDs needing a lot of cooling, I've played with all manner of
superbright emitters from white thru' traffic light colours all the way to
red, in 'standard' packages, and never found cooling to be especially a
problem. Although these are not hyper bright Luxeon-style emitters that I'm
talking here, which I know *do* require external cooling, They are
never-the-less still bright enough to hurt your eyes, and light a dark room
up quite well. Where I have found theremal issues, is in the current control
circuitry, even if just a simple resistor.

I agree that the potential ban on incandescents is just a government
knee-jerk reaction, brought on by hysterical claims from their 'scientific
advisors' that these things are going to bring about the end of the world,
but not if we use the marvelous direct replacement CFLs instead (ha!) ...
I was just interested what others' opinions on this were.

So, I'm still no closer to knowing how the multi-LED GU10-s or even single
LED types, are actually ballasted for 240v AC use, and whether the claim
that "these lamps put out almost no heat at all" is at least basically true
overall, in which case the ballasting arrangement must be *very* efficient,
or refers specifically to forward IR radiation in the same direction as the
light, which obviously will be minimal, or is a fundamental marketing hype
lie. Maybe I'll just buy one, and see if I can figure out just what its guts
are.

Arfa

LEDs as lamp replacements
 

"Arfa Daily" wrote in
:

So, I'm still no closer to knowing how the multi-LED GU10-s or even
single LED types, are actually ballasted for 240v AC use, and whether
the claim that "these lamps put out almost no heat at all" is at least
basically true overall, in which case the ballasting arrangement must
be *very* efficient, or refers specifically to forward IR radiation in
the same direction as the light, which obviously will be minimal, or
is a fundamental marketing hype lie. Maybe I'll just buy one, and see
if I can figure out just what its guts are.


I'm not sure yet either, if it has to be really tiny. I'd allow for the
mains to low-volt part to be done in something about matchbox size, not
sure about smaller though.

The point with the 5mm LED's is that don't need much cooling, because they
don't put out much heat. If they did they'd burn because they really ARE
terrible for thermal coupling, thus proving that any claim to get high
output from such isn't a good claim. Not even the best LED's are that
efficient.

I agree that some strong output can be had but it's usually directional,
and close to monochrmatic. As soon as that energy is spread in a broad
spectrum by phosphor, you need a very strong source of shortwave light to
pump the phosphors, and the clue is a heatsink, or a diode that is clearly
made for mounting on one.

One thought, maybe not wildly helpful: I remember being suprised as a kid
by a NiCd charger that was as small as the 4 x AA battery pack. It had no
transformer. It had a rectifier and current limit resistor and did not run
hot. I guess the unhelpful part of this observation is that it didn't have
to provide one amp of current. On the other hand, power conversion needs to
provide that amp at low volts, so as it's a lot less than an amp at 240V,
the smoothing capacitor might not need to be large. There might be
efficient circuits that don't even need one.

LEDs as lamp replacements
 

"Lostgallifreyan" wrote in message
...
"Arfa Daily" wrote in
:

So, I'm still no closer to knowing how the multi-LED GU10-s or even
single LED types, are actually ballasted for 240v AC use, and whether
the claim that "these lamps put out almost no heat at all" is at least
basically true overall, in which case the ballasting arrangement must
be *very* efficient, or refers specifically to forward IR radiation in
the same direction as the light, which obviously will be minimal, or
is a fundamental marketing hype lie. Maybe I'll just buy one, and see
if I can figure out just what its guts are.


I'm not sure yet either, if it has to be really tiny. I'd allow for the
mains to low-volt part to be done in something about matchbox size, not
sure about smaller though.

The point with the 5mm LED's is that don't need much cooling, because they
don't put out much heat. If they did they'd burn because they really ARE
terrible for thermal coupling, thus proving that any claim to get high
output from such isn't a good claim. Not even the best LED's are that
efficient.

I agree that some strong output can be had but it's usually directional,
and close to monochrmatic. As soon as that energy is spread in a broad
spectrum by phosphor, you need a very strong source of shortwave light to
pump the phosphors, and the clue is a heatsink, or a diode that is clearly
made for mounting on one.

One thought, maybe not wildly helpful: I remember being suprised as a kid
by a NiCd charger that was as small as the 4 x AA battery pack. It had no
transformer. It had a rectifier and current limit resistor and did not run
hot. I guess the unhelpful part of this observation is that it didn't have
to provide one amp of current. On the other hand, power conversion needs
to
provide that amp at low volts, so as it's a lot less than an amp at 240V,
the smoothing capacitor might not need to be large. There might be
efficient circuits that don't even need one.

Points well taken, but I'm gonna reserve judgement at this time, until I can
find out how it's done. If the whole string of LEDs is in series, and they
are not super high power types requiring an amp continuous, then we could be
talking just 150mA or so. Alternatively, we could be talking pulsing the
whole string at an amp or so. I really think that I'm going to have to buy
one, and attack it with the Dremmel ... I can't think that I have ever seen
any kind of switching supply that works from low frequency AC input power,
that doesn't have a smoothing cap. It's hard to see how it could be done
without, unless you employ 'electronic' smoothing using a regulator with
feedback, as I have sometimes seen done in 'professional' equipment, but
even then, you're going to be talking circuitry that is as big as a
smoothing cap of as little as 22uF at the required 400v working, would be.

Looking at the pictures of the Cree GU10 replacements, it's hard to say if
the enclosure is a 100% ringer for the incandescent version, but even if
it's not, it still looks pretty tight to get any kind of 'conventional'
switcher squeezed into.

Arfa

LEDs as lamp replacements
 

"Arfa Daily" wrote in
:

I really
think that I'm going to have to buy one, and attack it with the
Dremmel

Set to with zeal, my son. :) If I had a dremel, I would. Probably.

Did find this though:
http://www.claremicronix.com/datashe...0Sheet%20Rev05
3107.pdf
Again, clickable: http://tinyurl.com/2kf3jv

That's interesting because it shows 90% efficiency as I hoped might be
had, from a circuit with no large smoothing capacitor. It's just one tiny
IC driving a MOSFET and using an inductor. I don't know how big that
inductor is, but not very, I imagine. Maybe similar to the one on the
module on the eBay page I linked to earlier. A series chain of three or
four LED's might well be driven directly from the mains, and all fitted
inside one of those small lamp capsules. Heat dispersal might be tight, but
doable, especially in those lamps with the fine louvre shells to allow
convection to get in amongst the doings.

LEDs as lamp replacements
 

On Thu, 12 Jul 2007 17:42:44 GMT, Lostgallifreyan
wrote:

Did find this though:
http://www.claremicronix.com/datashe...0Rev053107.pdf
Again, clickable: http://tinyurl.com/2kf3jv

That's interesting because it shows 90% efficiency as I hoped might be
had, from a circuit with no large smoothing capacitor.

There might need to be some amount of filtering done on the input
that is not shown on the sample schematic. The chip needs a
minimum of 8 VDC input, so to for an AC bulb replacement, you'd
need to add a bridge rectifier and probably a small filtering cap.

LEDs as lamp replacements
 

"Lostgallifreyan" wrote in message
...
"Arfa Daily" wrote in
:

I really
think that I'm going to have to buy one, and attack it with the
Dremmel

Set to with zeal, my son. :) If I had a dremel, I would. Probably.

Did find this though:
http://www.claremicronix.com/datashe...0Sheet%20Rev05
3107.pdf
Again, clickable: http://tinyurl.com/2kf3jv

That's interesting because it shows 90% efficiency as I hoped might be
had, from a circuit with no large smoothing capacitor. It's just one tiny
IC driving a MOSFET and using an inductor. I don't know how big that
inductor is, but not very, I imagine. Maybe similar to the one on the
module on the eBay page I linked to earlier. A series chain of three or
four LED's might well be driven directly from the mains, and all fitted
inside one of those small lamp capsules. Heat dispersal might be tight,
but
doable, especially in those lamps with the fine louvre shells to allow
convection to get in amongst the doings.

Well, that's not strictly true. The issue of where the input voltage comes
from, is carefully avoided in the data sheet. It only shows that the chip
can operate from a DC input range of 8 to 450v. To get the DC input from the
mains, would still require a bridge and smoothing cap. However, looks like a
useful chip, and a good candidate for the back end processing. It claims
that it can drive "hundreds" of LEDs in series / parallel strings. Still
reserving judgement at this time ...

Arfa

LEDs as lamp replacements
 

"Arfa Daily" wrote in message
...

"Lostgallifreyan" wrote in message
...
"Arfa Daily" wrote in
:

I really
think that I'm going to have to buy one, and attack it with the
Dremmel

Set to with zeal, my son. :) If I had a dremel, I would. Probably.

Did find this though:
http://www.claremicronix.com/datashe...0Sheet%20Rev05
3107.pdf
Again, clickable: http://tinyurl.com/2kf3jv

That's interesting because it shows 90% efficiency as I hoped might be
had, from a circuit with no large smoothing capacitor. It's just one tiny
IC driving a MOSFET and using an inductor. I don't know how big that
inductor is, but not very, I imagine. Maybe similar to the one on the
module on the eBay page I linked to earlier. A series chain of three or
four LED's might well be driven directly from the mains, and all fitted
inside one of those small lamp capsules. Heat dispersal might be tight,
but
doable, especially in those lamps with the fine louvre shells to allow
convection to get in amongst the doings.

Well, that's not strictly true. The issue of where the input voltage comes
from, is carefully avoided in the data sheet. It only shows that the chip
can operate from a DC input range of 8 to 450v. To get the DC input from
the mains, would still require a bridge and smoothing cap. However, looks
like a useful chip, and a good candidate for the back end processing. It
claims that it can drive "hundreds" of LEDs in series / parallel strings.
Still reserving judgement at this time ...

Arfa
Here's a really interesting site

http://www.oksolar.com/led/led_color_chart.htm

Follow the various page links to the chromaticity chart, and " More
information on LEDs" at the bottom. I didn't realise that they were already
in use in street lighting. There is mention of higher colour temperatures
improving human night vision. There is also an interesting LED colour chart,
which shows one at 4500K called "incandescent". A couple of years back, I
was in Disney when they put on a show in front of the Magic Castle. There
was a stage spot set up on the top of a pole, projecting a brilliant white
beam of considerable strength. I didn't take much notice of it, until it
suddenly changed colour. During the show, it produced a whole range of
colours, but I couldn't see that the enclosure was anything like big enough
to accommodate a coloured gel wheel. I remember wondering at the time, if
this had been implemented using very high power RGB LEDs. I suppose that it
is also possible that it could have been a plasma lamp with dichroic mirrors
and LCD panels. Are any LEDs actually powerful enough to make stage lighting
from ? Can they be mounted in any way that allows light collection and
direction through beam forming optics ?

Arfa