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PICList Thread
'[BUY]: LED sources...'
2002\03\11@144529 by Pic Dude

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(1) Looking for low-cost bargraph LED's.  Mostly all-reds, 10-seg.  Anyone
know of good low-cost sources for these (~qty 10 - 20)?  So far I've found
JDR at $1.59 ea.

(2) What's up with blue LEDs?  Why are these things 10x to 20x the price
of their R/Y/G counterparts?

Cheers,
-Neil.

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2002\03\11@175156 by David Duffy

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At 01:51 PM 11/03/2002 -0600, you wrote:
>(1) Looking for low-cost bargraph LED's.  Mostly all-reds, 10-seg.  Anyone
>know of good low-cost sources for these (~qty 10 - 20)?  So far I've found
>JDR at $1.59 ea.
>
>(2) What's up with blue LEDs?  Why are these things 10x to 20x the price
>of their R/Y/G counterparts?

Because it's new(ish) technology. With time comes higher quantity & lower
price.
Regards...

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2002\03\11@181256 by michael brown

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> >(2) What's up with blue LEDs?  Why are these things 10x to 20x the price
> >of their R/Y/G counterparts?
>
> Because it's new(ish) technology. With time comes higher quantity & lower
> price.
> Regards...

That and the fact that there is still a valid patent on them (they were only
recently invented).  Plus they look really good.  ;-)

michael brown

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2002\03\11@182337 by Pic Dude

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Other than just looking good, blue is supposed to be one of the
best LED colors for sunlight viewing.  I have to test that for myself
but so far, I'm willing to accept it.

Cheers.

{Original Message removed}

2002\03\11@190847 by Benjamin Bromilow

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Give it a few years and they'll come down in price even more. Every year
(year upon year), when I read the new components catalogue I'm amazed at how
much blue LED prices have dropped (okay I should get out more!).... So if
you think they are expensive now...... White LEDs which came out a couple of
years later as (I recall) should show a similar decrease in price. At the
moment they're a bit painful on the budget...

Ben

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2002\03\11@191323 by Sid Weaver

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Mouser has blue diffused T1 -3/4 LEDs for 2.32.  That's not really too bad.

Sid

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2002\03\11@193223 by Pic Dude

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The thing is that it is bad when you compare the red versions
at $0.07 to $0.20 each.

Thanks,
-Neil.


{Original Message removed}

2002\03\11@202259 by Pic Dude

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I guess the technology to produce blue must be different, cause it would
take some mental coaxing to get me to accept that one can now patent
a color.  That and the fact that R/Y/G has been around for so long, but
not blue.

Last time I ran into a hard-to-accept patent, it was the PBJ.


{Original Message removed}

2002\03\11@210011 by Jeff DeMaagd

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True, It's not the blue itself, it is the process used to make a diode in
such a way that it happens to emit blue.  IIRC, it wasn't easy, many
researchers had tried and given up.  There are limitations in the
semiconductors needed to emit such a wavelength that was ridiculously hard
to fabricate and get reliable, due to the elements involved in the fabbing.

And you have a point, if you don't like the price, pick another color.

Jeff

At 07:29 PM 3/11/02 -0600, you wrote:
>I guess the technology to produce blue must be different, cause it would
>take some mental coaxing to get me to accept that one can now patent
>a color.  That and the fact that R/Y/G has been around for so long, but
>not blue.

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2002\03\11@211303 by Spehro Pefhany

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At 05:30 PM 3/11/02 -0600, you wrote:
>Other than just looking good, blue is supposed to be one of the
>best LED colors for sunlight viewing.  I have to test that for myself
>but so far, I'm willing to accept it.

I have a blue display on my office stereo. It looks "cool" but it is
a horrible thing to have to read from any distance (like the eight or
ten feet to my Aeron chair). Look at tall office buildings with blue
logos on them sometime- much more blurry than the red colored logos at the
same distance. Blue LEDs, yes, but for displays f'getaboudit.

Best regard,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
@spam@speffKILLspamspaminterlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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2002\03\11@214312 by Jinx

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> take some mental coaxing to get me to accept that one can
> now patent a color

Patenting or copyrighting a colour is quite common - Coca
Cola's red, Cadbury's purple, yellow / blue telephone pages

Not as scary as patenting human genomes though........

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2002\03\11@221031 by Jeff DeMaagd

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At 03:42 PM 3/12/02 +1300, you wrote:
> > take some mental coaxing to get me to accept that one can
> > now patent a color
>
>Patenting or copyrighting a colour is quite common - Coca
>Cola's red, Cadbury's purple, yellow / blue telephone pages

You mean trademarking, right?

Jeff

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2002\03\11@230700 by Herbert Graf

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> At 05:30 PM 3/11/02 -0600, you wrote:
> >Other than just looking good, blue is supposed to be one of the
> >best LED colors for sunlight viewing.  I have to test that for myself
> >but so far, I'm willing to accept it.
>
> I have a blue display on my office stereo. It looks "cool" but it is
> a horrible thing to have to read from any distance (like the eight or
> ten feet to my Aeron chair). Look at tall office buildings with blue
> logos on them sometime- much more blurry than the red colored logos at the
> same distance. Blue LEDs, yes, but for displays f'getaboudit.

       Yes, I have noticed that too, I believe it has something to do with our
eyes, perhaps they just aren't tuned to focus in on the blue part of the
spectrum in low light conditions (which tends to track since red displays
are as sharp as during the day). TTYL

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2002\03\11@233510 by Karl Seibert

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The last thing I heard, there was an ongoing patent fight between
Nichia and its former employee Shuji Nakamura.

http://www.eetimes.com/story/OEG20010824S0051 is a news story about
it.  I don't know how accurate or current the info on the page is.

Karl

Quoting Jeff DeMaagd <RemoveMEjeffspamTakeThisOuTDEMAAGD.COM>:

{Quote hidden}

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2002\03\11@234130 by Karl Seibert

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The problem is chromatic aberration.  Blue light is bent
more than red light by the lens, so the blue focus point
is in front of the retina when the red light focuses on
the retina (or even more in front of the retina in my case).

I don't know why red is right and blue is focused short
instead of blue being focused right and red focused long.

Karl

Quoting Herbert Graf <RemoveMEmailinglistEraseMEspamEraseMEFARCITE.NET>:
{Quote hidden}

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2002\03\13@200606 by Rodrigo Valladares P.

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And red is a good color to use in poor light condition, where eyes need a
rapid shift from light (red) to darkness. Inside ship at day the lights are
white, and at night (no laught!) are red, so when people go outside, and is
a black night, the eyes accomodate faster than with other light color.

Also i don4t know why.

RVP.

>
> I don't know why red is right and blue is focused short
> instead of blue being focused right and red focused long.
>

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2002\03\13@212115 by michael brown

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> And red is a good color to use in poor light condition, where eyes need a
> rapid shift from light (red) to darkness. Inside ship at day the lights
are
> white, and at night (no laught!) are red, so when people go outside, and
is
> a black night, the eyes accomodate faster than with other light color.
>
> Also i don4t know why.

Because your eyes are the least sensitive to red light (as far as pupil
dilation/contraction is concerned).  IOW, red light does not cause your
pupils to respond as much as bluer light.

michael brown

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2002\03\13@233937 by Jinx

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> Because your eyes are the least sensitive to red light

Peak response is at green (night vision viewers) and
yellow (warning signs / emergency vehicles)

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2002\03\14@020119 by Pic Dude

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Missed part of this thread, so sorry if this went past, but I'd like
to know what's the best LED color for dashboards, and viewing
in indirect sunlight.  I remember seeing a study about this some
months back, but can't find it now.



{Original Message removed}

2002\03\14@025219 by Brandon Irwin

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At 11:06 PM 3-13-2002, Pic Dude wrote:
> > > Because your eyes are the least sensitive to red light
> >
> > Peak response is at green (night vision viewers) and
> > yellow (warning signs / emergency vehicles)


It makes you wonder what the world would look like if our eyes had a flat
response. I read somewhere that for red light to look the same amplitude,
it had to be same large number, like 1000, times brighter. This makes me
imagine how painful a sunset would be. :)


Brandon Irwin

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2002\03\14@032632 by Dave King

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At 11:49 PM 3/13/02 -0800, you wrote:
>At 11:06 PM 3-13-2002, Pic Dude wrote:
>> > > Because your eyes are the least sensitive to red light
>> > Peak response is at green (night vision viewers) and
>> > yellow (warning signs / emergency vehicles)
>
>It makes you wonder what the world would look like if our eyes had a flat
>response. I read somewhere that for red light to look the same amplitude,
>it had to be same large number, like 1000, times brighter. This makes me
>imagine how painful a sunset would be. :)
>
>Brandon Irwin

If you look for the CIE charts and know what the wavelength is it's very
easy to figure out
the effective output of a color. For example a green might be .785 while
the red is .48
and a blue .28. In other words if you had a 100 candela white, the red
would appear to output
78% of that and so on. There are some colors that are under 1% effective.

There are a couple of other standards but the CIE one has been around since
the mid 30's
and is generally accepted by everyone.

Dave

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2002\03\14@080651 by Olin Lathrop

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> > Because your eyes are the least sensitive to red light
>
> Peak response is at green (night vision viewers) and
> yellow (warning signs / emergency vehicles)

He should have said "iris" instead of just "eyes".  The retina (the imaging
part of the eyes) is most senstivie to green as you said.  The iris (the
automatic F-stop adjustment) is least sensitive to red.


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Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, EraseMEolinspamspamspamBeGoneembedinc.com, http://www.embedinc.com

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