What's the most efficient LED _color_?

[William P.N. Smith]

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just
visibility for a given input current.

And for a given color, who makes the most efficient/brightest ones?

Thanks!

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Don Klipstein]

In article <fe3rhvoehlod253q0ibnse5jek1le174p7@4ax.com>, William P.N.
Smith wrote:

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just
visibility for a given input current.

And for a given color, who makes the most efficient/brightest ones?

The most efficient LEDs that I know of are Lumileds "Luxeon" orange
ones with the "Lambertian" radiation pattern (or "high dome"), which
are rated for 1 watt (350 mA) and most efficient with somewhat less power.
According to the Lumileds datasheet, their overall luminous efficacy is
typically 53 lumens per watt. Ones with other radiation patterns have a
less efficient chip.
Their red 1-watt Luxeons with the "Lambertian" radiation pattern should
get about 40 lumens/watt.

Next seems to me to be Nichia green LEDs. In my experience at .07 watt
(20 mA), their overall luminous efficacy is about 35 lumens/watt. They
are even more efficient when underpowered, perhaps 45-50 lumens/watt at a
few milliamps (.01-.016 watt).

- Don Klipstein (don@misty.com, http://www.misty.com/~don/led.html)

 

[Lewin A.R.W. Edwards]

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically been green?

The human eye is most sensitive to yellow-green light.

 

[Lewin A.R.W. Edwards]

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically been green?

The human eye is most sensitive to yellow-green light.

 

[Lewin A.R.W. Edwards]

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically been green?

The human eye is most sensitive to yellow-green light.

 

[William P.N. Smith]

larwe@larwe.com (Lewin A.R.W. Edwards) wrote:
[I wrote]

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically been green?

Have you ever wondered why LEDs started out red? LED efficiencies are
much higher in the red area than green, blue, white, etc, and I'm
interested in visual impact per watt, which appears to be Luxeon
orange as per other respondents.

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[R.Lewis]

"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0307221725.7426b9d4@posting.google.com...

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically
been green?

The human eye is most sensitive to yellow-green light.

Which has nothing to do with which colour is chosen for use use in
cellphones etc.

 

[Watson A.Name - 'Watt Sun]

In article <b3bthvo9ctp1e4fbbhatkjupjtkidp897l@4ax.com>,
wpns@compusmiths.com mentioned...

larwe@larwe.com (Lewin A.R.W. Edwards) wrote:
[I wrote]
If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just

Have you never wondered why cellphones, dashboards etc have historically been green?

Have you ever wondered why LEDs started out red? LED efficiencies are
much higher in the red area than green, blue, white, etc, and I'm
interested in visual impact per watt, which appears to be Luxeon
orange as per other respondents.

Luxeon Stars take several hundred mA, are you aware of that?


--
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Just when you thought you had all this figured out, the gov't
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[William P.N. Smith]

Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:

Luxeon Stars take several hundred mA, are you aware of that?

I think I'll be able to crank my pulse current up to at least 50
milliamps, which is the low end of the spec for the red-orange
Star/Emitter.

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Watson A.Name - 'Watt Sun]

In article <608b6569.0307240547.62f127f9@posting.google.com>,
larwe@larwe.com mentioned...

Have you never wondered why cellphones, dashboards etc have historically been green?

Have you ever wondered why LEDs started out red? LED efficiencies are
much higher in the red area than green, blue, white, etc, and I'm

LED efficiencies are typically measured in *light output per input
watt* (IOW they are a measure of how much input power is converted to
heat),

Or more to the point, converted to light, not heat.

but *visual impact per watt* is not the same thing, n'est-ce
pas?

Battery-operated appliances have used green LEDs since forever. The

Green LEDs have been much more expensive in the recent past, so most
equipment used the much cheaper red LEDs. This is still true but to a
lesser degree. And I would guess that for the first decade, maybe
longer, red was the only color available. So does that mean that red
LEDs were used for forever +10 years? I don't think so. AAMOF it
wasn't until the '70s that any color LED was cheap enough to be in
commercial use. See the ledmuseum.org for more historical info and
timelines. Some great pics of old LEDs, too.

assumption I make is that the engineers looked at the available LED
options and decided that for a given battery drain, green LEDs made
for the best *visibility*.

Not really.

PS: Sorry about the triple post, it's Google's fault, not mine!

BJotD:

A blonde girl enters a store that sells curtains. She tells the
salesman: "I would like to buy a pink curtain in the size of my
computer screen".

The surprised salesman replies:
"But, madam, computers do not have curtains.... "

And the blonde said:..........
"Helloooo.... I've got Windows!!!!!!!!!!!!!!!"


--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@

 

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"Lewin A.R.W. Edwards" wrote:

LED efficiencies are typically measured in *light output per input
watt* (IOW they are a measure of how much input power is converted to
heat), but *visual impact per watt* is not the same thing, n'est-ce
pas?

LED efficiencies are typically measured in candela (= lumen/sterad) for
a fixed current (typically 20 mA), or more generally in lumen/watt.
These units do refer to the visual impact on the human eye, and not
simply to the power converted to light. Thus, 1 lumen of orange light
represents many times the power (in watt) of 1 lumen of green light.

You may want to look at the thread "efficiency of yellow LEDs" where
this has recently been discussed on this group.

Martin.


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[William P.N. Smith]

don@manx.misty.com (Don Klipstein) wrote:

William P.N. Smith wrote:
Watson A.Name - 'Watt Sun' <alondra101@hotmail.com> wrote:
Luxeon Stars take several hundred mA, are you aware of that?

I think I'll be able to crank my pulse current up to at least 50
milliamps, which is the low end of the spec for the red-orange
Star/Emitter.

You're probably better off with 5 mm Agilent "Sunpower" series or the
like. Check out my efficient LED web page,
http://www.misty.com/~don/led.html

Yeah, that's where you pointed me to originally, and where I found the
55 lumens/watt Luxeon red-orange 'Lambertian' LEDs. The data sheets
for those show I/V curves and luminous flux are fairly linear down to
50 mA.

They arrived today, and I was _very_ impressed by the brightness,
these are going to make great beacons!

Thanks!

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Eric Smith]

William P.N. Smith <wpns@compusmiths.com> writes:

If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just
visibility for a given input current.

Depends on whether you define efficiency by energy output, or by
perceptual brightness. They're not the same, since the eye's frequency
response curve is not flat.

 

[R.Lewis]

"William P.N. Smith" <wpns@compusmiths.com> wrote in message
news:qlqkivkr116ccjs0c66qavh6goidmghpvg@4ax.com...

Eric Smith <eric-no-spam-for-me@brouhaha.com> wrote:
William P.N. Smith <wpns@compusmiths.com> writes:
If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just
visibility for a given input current.

Depends on whether you define efficiency by energy output, or by
perceptual brightness. They're not the same, since the eye's frequency
response curve is not flat.

My mistake, for "visibility for a given input current" read
"perceptual brightness for a given input current". This appears to be
"lumens per watt", yes?

You are correct in that you require the most lumens per watt - also called
efficacy.

 

[William P.N. Smith]

"R.Lewis" <h.lewis@connect-2.co.uk> wrote:

William P.N. Smith <wpns@compusmiths.com> writes:
If I want to make some beacons with very low power consumption, what's
my best bet for efficiency? I don't really care about color, just
visibility for a given input current.

You are correct in that you require the most lumens per watt - also called
efficacy.

How about dark-adapted versus light-adapted eyes? A friend just
pointed out that
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/efficacy.html#c1
shows that the dark-adapted eye is (3X) more sensitive in Cyan, where
light-adapted eyes are more sensitive in (yellowish) Green. I can get
Cyan LEDs in 30 lumens per watt, or red-orange in 55 lumens per watt,
which is better for seeing at night?

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

[Don Klipstein]

In article <tmdniv8c240mp1hcvlqgoj3ea08h7jk9gt@4ax.com>, William P.N.
Smith wrote:

How about dark-adapted versus light-adapted eyes? A friend just
pointed out that
http://hyperphysics.phy-astr.gsu.edu/hbase/vision/efficacy.html#c1
shows that the dark-adapted eye is (3X) more sensitive in Cyan, where
light-adapted eyes are more sensitive in (yellowish) Green. I can get
Cyan LEDs in 30 lumens per watt, or red-orange in 55 lumens per watt,
which is better for seeing at night?

Cyan works better when the illumination level is low enough for
scotopic vision (night vision) to be significant.
The lumen is defined in terms of photopic vision (bright-adapted eye).
More specifically, the lumen is defined in terms of the "photopic
function", which is (in my words) the spectral response of a
bright-light-adapted "official average human eyeball" in central vision.

- Don Klipstein (don@misty.com)

 

[Fred Abse]

On Fri, 01 Aug 2003 14:28:30 +0100, William P.N. Smith wrote:

My mistake, for "visibility for a given input current" read "perceptual
brightness for a given input current". This appears to be "lumens per
watt", yes?

No, lumens are actual light energy _without_ taking into account human
perception.

--
Then there's duct tape ...
(Garrison Keillor)
nofr@sbhevre.pbzchyvax.pb.hx

 

[William P.N. Smith]

Fred Abse <excretatauris@cerebrumconfus.it> wrote:

On Fri, 01 Aug 2003 14:28:30 +0100, William P.N. Smith wrote:

My mistake, for "visibility for a given input current" read "perceptual
brightness for a given input current". This appears to be "lumens per
watt", yes?

No, lumens are actual light energy _without_ taking into account human
perception.

We keep going around and around on this. What's the "perceptual
brightness" metric?

--
William Smith wpns@compusmiths.com N1JBJ@amsat.org
ComputerSmiths Consulting, Inc. www.compusmiths.com

 

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Fred Abse wrote:

No, lumens are actual light energy _without_ taking into account human
perception.

This statement is plain wrong.

You may want to look at the thread "efficiency of yellow LEDs" where
this has recently been discussed on this group.

Martin.


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[Don Klipstein]

In <pan.2003.08.01.20.36.24.521972.759@cerebrumconfus.it>, Fred Abse wrote:

On Fri, 01 Aug 2003 14:28:30 +0100, William P.N. Smith wrote:

My mistake, for "visibility for a given input current" read "perceptual
brightness for a given input current". This appears to be "lumens per
watt", yes?

No, lumens are actual light energy _without_ taking into account human
perception.

ABSOLUTELY FALSE!!!

A lumen of visible light that is monochromatic and of a single
wavelength/frequency is watts of optical output multiplied by 681 (or is
it 683?) times the "photopic function" (spectral response of an "official
average bright-adapted human eyeball" in my words) of the wavelength.
Should the light in question consist of different wavelengths, then take
an appropriately weighted average.

The lumen is a photometric unit (designed to take into account the
spectral response of human vision, specifically bright-adapted as opposed
to dark-adapted). Other photometric units are the candela (lumen per
steradian, which is "primarily defined" and from which other rphotometric
units are supposedly derived from), the lux (lumen per square meter), the
footcandle (lumen per square foot), and the like.
There are radiometric units of light, which as opposed to photometric
units, are not designed to take into account for the spectral response of
human vision. Radiometric units would have usual power (or energy) units
such as watt, joule, or in some cases either of these per unit area,
angular coverage or the like.

- Don Klipstein (don@misty.com)