"white" LED's vs. incandescent and halogen lights

Brendan Gillatt k wrote in
:

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dlzc wrote:
Dear me:

On Dec 4, 3:50 pm, me wrote:
It's obvious that the mundane "white" LED bicycle
lights do not light up the asphalt roads very well.

Emitted watts in the fraction or single digit watts.

Incandescents, halogens, and sodium lights
do better.

Tens to hundreds of watts.

That is an unfair comparison--the _light_ power output of a halogen bulb
is much less than a modern LED for the same electrical power input.


The latest LEDs from Cree now produce more than twice the amount of light
that a compact fluorescent tube (CFT - otherwise know as an energy-saving
lamp) produces for the same amount of electrical power. CFTs produce
around 3-4 times the light of a halogen lamp.

"Mr. Benn" wrote in message
...
Brendan Gillatt k wrote
in
:

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dlzc wrote:
Dear me:

On Dec 4, 3:50 pm, me wrote:
It's obvious that the mundane "white" LED bicycle
lights do not light up the asphalt roads very well.

Emitted watts in the fraction or single digit watts.

Incandescents, halogens, and sodium lights
do better.

Tens to hundreds of watts.

That is an unfair comparison--the _light_ power output of a halogen bulb
is much less than a modern LED for the same electrical power input.


The latest LEDs from Cree now produce more than twice the amount of light
that a compact fluorescent tube (CFT - otherwise know as an energy-saving
lamp) produces for the same amount of electrical power. CFTs produce
around 3-4 times the light of a halogen lamp.


The latest fireflies from Nature now produce more than a million times the
amount
of light that a compact LED produces for even less electrical power.

Dear Brendan Gillatt:

On Dec 5, 6:45*am, Brendan Gillatt
k wrote:
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dlzc wrote:
Dear me:

On Dec 4, 3:50 pm, me wrote:
It's obvious that the mundane "white" LED bicycle
lights do not light up the asphalt roads very well.

Emitted watts in the fraction or single digit watts.

*Incandescents, halogens, and sodium lights
do better.

Tens to hundreds of watts.

That is an unfair comparison--the _light_ power
output of a halogen bulb is much less than a modern
LED for the same electrical power input.

How is that an *unfair* comparison? The LED energy goes nearly
straight to making light, so you can get light from smaller
batteries. The other technologies get a subset of mass to a "natural"
emission temperature, so there is significant heat storage (lost at
end-of-cycle), and heat losses while operating.

You can get more light from a halogen (etc) source, because you don't
have to construct it out of unitary cells of "fixed" output. You just
need a bigger battery...

Not unfair, just physics.

David A. Smith

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dlzc wrote:
How is that an *unfair* comparison? The LED energy goes nearly
straight to making light, so you can get light from smaller
batteries. The other technologies get a subset of mass to a "natural"
emission temperature, so there is significant heat storage (lost at
end-of-cycle), and heat losses while operating.

Because you are saying that LED lights emit power in the "fraction or
single digit watts" and that "Incandescents, halogens, and sodium lights"
emit with "Tens to hundreds of watts". This is only true if you supply
the former with a smaller amount of electrical energy than the later.
Hence it is an unfair comparison.

You can get more light from a halogen (etc) source, because you don't
have to construct it out of unitary cells of "fixed" output. You just
need a bigger battery...


Huh?

You can make an LED driver of close to 90% efficiency with inputs above
and/or below the battery voltage. There is no need for unitary cells of
fixed output.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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Androcles wrote:
"Mr. Benn" wrote in message
...
Brendan Gillatt k wrote
in
:

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Hash: SHA1

dlzc wrote:
Dear me:

On Dec 4, 3:50 pm, me wrote:
It's obvious that the mundane "white" LED bicycle
lights do not light up the asphalt roads very well.
Emitted watts in the fraction or single digit watts.

Incandescents, halogens, and sodium lights
do better.
Tens to hundreds of watts.
That is an unfair comparison--the _light_ power output of a halogen bulb
is much less than a modern LED for the same electrical power input.

The latest LEDs from Cree now produce more than twice the amount of light
that a compact fluorescent tube (CFT - otherwise know as an energy-saving
lamp) produces for the same amount of electrical power. CFTs produce
around 3-4 times the light of a halogen lamp.


The latest fireflies from Nature now produce more than a million times the
amount
of light that a compact LED produces for even less electrical power.



Do they come in a dynohub model? :/

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

On Dec 5, 1:57*am, " wrote:
On Dec 4, 10:18*pm, pm wrote:



On Dec 4, 9:30*pm, " wrote:

On Dec 4, 2:50*pm, me wrote:

It's obvious that the mundane "white" LED bicycle lights do not light
up the asphalt roads very well. *Incandescents, halogens, and sodium
lights do better. *There seem to be a lot of oranges and yellows on
the illuminated asphalt surface.

My question is why does it appear this way?

I presume that the yellow-orange-red spectral emissions from the LED's
are weaker than the blues. *The blues are voltage induced while the y-
o-r's are secondary from phosphors in the casing. *Therefore to help
refine my question,

1. *Do the stronger blues in the LED cause the weaker yellow/orange/
reds to be less perceived?

* "White" LEDs have a strong peak in the blue and a nearly Gaussian
curve centered in the green, extending from the blue-green to the red..
They're kinda weak in the tails. Do a Google Image search for "white
led spectrum" and see for yourself.

* The other lamp types you mention are stronger in the red, which the
eye is more sensitive to, particularly at night.

Red map lights are used to preserve dark adaptation because rods _do
not_ respond to them. Rods are most sensitive somewhere in the blue-
green. Do a google image search on "rod sensitivity," etc. Combine
with your previous google image search and you will find that the peak
sensitivity for rods coincides with the "dip" in the typical white LED
spectrum.

* The ~430 nm rod peak (beware line wrap):

http://www.ecse.rpi.edu/~schubert/Li...-dot-org/chap1...

* is a bit offset from the LED dip at 475 nm.

http://www.mvlc.info/images/photos/led/spectral3.jpg

* Also, I should have been clearer; cones are more sensitive to red
than to blue.

Maybe you were thinking cones, but still I don't buy it as an
explanation for perceived LED problems. The yellow phosphor is almost
exactly (and not by accident) where you'd want it to be to maximize
luminous efficiency (the CIE y-bar color matching function and the
yellow phosphor both peaking at about 550 nm)


IMO though WRT the OP's question the deal-breaker is the greater
reflectivity of asphalt in the red independent of light intensity;
illuminated by incandescent etc. lamps it has red-orangish highlights
as the OP says, but under LED illumination it's just black.

I think this is part of the problem for sure.

Dear Brendan Gillatt:

On Dec 5, 10:04*am, Brendan Gillatt
k wrote:
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Hash: SHA1

dlzcwrote:
How is that an *unfair* comparison? *The
LED energy goes nearly straight to making
light, so you can get light from smaller
batteries. *The other technologies get a
subset of mass to a "natural" emission
temperature, so there is significant heat
storage (lost at end-of-cycle), and heat
losses while operating.

Because you are saying that LED lights emit
power in the "fraction or single digit watts"
and that "Incandescents, halogens, and
sodium lights" emit with "Tens to hundreds
of watts".

I'm talking about power *draw*.

This is only true if you supply the former with
a smaller amount of electrical energy than the
later.

Which is what I was talking about, even though that was absolutely not
clear.

Hence it is an unfair comparison.

As I wrote it, you are correct.

You can get more light from a halogen (etc)
source, because you don't have to construct
it out of unitary cells of "fixed" output. *You just
need a bigger battery...

Huh?

LEDs are, in the cheap ones I have seen, makes of small individual
units. Maybe they don't have to be, but they have been so far.

You can make an LED driver of close to 90%
efficiency with inputs above and/or below the
battery voltage. There is no need for unitary
cells of fixed output.

Yes, thank you. I like LEDs too, in case that was not clear.

David A. Smith

On Fri, 4 Dec 2009 14:50:04 -0800 (PST), me
wrote:

My question is why does it appear this way?

Because fluorescent LEDs emit light almost exclusively in the
frequencies that hurt, which makes them look glaring-bright when they
are really quite dim.

--
Joy Beeson
joy beeson at comcast dot net

On 6 Dec, 03:25, Joy Beeson wrote:
On Fri, 4 Dec 2009 14:50:04 -0800 (PST), me

wrote:
My question is why does it appear this way?

Because fluorescent LEDs emit light almost exclusively in the
frequencies that hurt, which makes them look glaring-bright when they
are really quite dim. *

Which is why my 'old' technology work lamp with 24 LEDs works so well
on urban roads. The roads are already lit with yellow sodium and the
blueness picks up the colours the yellow does not. It's stark enough
to stand out from the surroundings as a positional marker yet not pin
point bright to glare other road users. I've been quite surprised at
how well it has done. I think that my desire not to outshine the
brighter streetlights works in my favour because of the resulting
colour balance seems normal.

In article
,
" wrote:

On Dec 4, 2:50Â*pm, me wrote:
It's obvious that the mundane "white" LED bicycle lights do not light
up the asphalt roads very well. Â*Incandescents, halogens, and sodium
lights do better. Â*There seem to be a lot of oranges and yellows on
the illuminated asphalt surface.

My question is why does it appear this way?

I presume that the yellow-orange-red spectral emissions from the LED's
are weaker than the blues. Â*The blues are voltage induced while the y-
o-r's are secondary from phosphors in the casing. Â*Therefore to help
refine my question,

1. Â*Do the stronger blues in the LED cause the weaker yellow/orange/
reds to be less perceived?

"White" LEDs have a strong peak in the blue and a nearly Gaussian
curve centered in the green, extending from the blue-green to the red.
They're kinda weak in the tails. Do a Google Image search for "white
led spectrum" and see for yourself.

The other lamp types you mention are stronger in the red, which the
eye is more sensitive to, particularly at night.

The human eye is not more sensitive to red.
It's peak sensitivity is ~560 nm---between yellow and green.

--
Michael Press