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Science Forum Index » Electronics - Design Forum » Making yellow from bi-color (red/green) LEDs
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| Joel Kolstad |
 Posted: Wed Feb 14, 2007 8:42 pm |
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Guest
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Just curious... if you're trying to use a bi-color (red/green) LED to make
yellow, how well does it work using an LED with a clear "lens" along with a
(clear) light-pipe (mounted above the PCB, going through the case)? I've used
diffused LEDs in the past to do this with no problem, but I'm thinking that
with a clear lens there won't be enough mixing of the red and green and the
user will just perceive the two distinct colors rather than yellow as
intended. Thoughts?
Given a choice of packages (e.g., 1210 vs. 0605), presumably I'd want the
smallest one available so that the red and green LED chips are as close
together as possible, right?
Thanks,
---Joel |
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| John Popelish |
| Posted: Wed Feb 14, 2007 9:01 pm |
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Joel Kolstad wrote:
Quote: Just curious... if you're trying to use a bi-color (red/green) LED to make
yellow, how well does it work using an LED with a clear "lens" along with a
(clear) light-pipe (mounted above the PCB, going through the case)? I've used
diffused LEDs in the past to do this with no problem, but I'm thinking that
with a clear lens there won't be enough mixing of the red and green and the
user will just perceive the two distinct colors rather than yellow as
intended. Thoughts?
Given a choice of packages (e.g., 1210 vs. 0605), presumably I'd want the
smallest one available so that the red and green LED chips are as close
together as possible, right?
As long as the viewer does not have a clear image of the two
die in the LED, the light will appear to be a single color.
The only problem with not diffused sources like this is
that the apparent hue may vary a bit with viewing angle. |
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| Michael A. Terrell |
| Posted: Wed Feb 14, 2007 9:07 pm |
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Joel Kolstad wrote:
Quote:
Just curious... if you're trying to use a bi-color (red/green) LED to make
yellow, how well does it work using an LED with a clear "lens" along with a
(clear) light-pipe (mounted above the PCB, going through the case)? I've used
diffused LEDs in the past to do this with no problem, but I'm thinking that
with a clear lens there won't be enough mixing of the red and green and the
user will just perceive the two distinct colors rather than yellow as
intended. Thoughts?
Given a choice of packages (e.g., 1210 vs. 0605), presumably I'd want the
smallest one available so that the red and green LED chips are as close
together as possible, right?
Thanks,
---Joel
Just wait till they decide to build cheaper traffic lights by using a
single light housing, with bi-color LEDs to get Red, Green and Yellow.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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| Joel Kolstad |
| Posted: Wed Feb 14, 2007 9:11 pm |
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"John Popelish" <jpopelish@rica.net> wrote in message
news:cdKdnSV8qfhFME7YnZ2dnUVZ_r3inZ2d@comcast.com...
Quote: As long as the viewer does not have a clear image of the two die in the LED,
the light will appear to be a single color.
Thanks John; I'm ordering a few to play with and see how it does. In an 0605
package I suspect that unless you're within inches of the LED you wouldn't be
able to discern the colors individually. (Harkening back to the time as a kid
you put your face up to the glass and realize that there are actually three
different colors there, all arranged in nice little triads...)
---Joel |
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| Terry Given |
| Posted: Wed Feb 14, 2007 10:32 pm |
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Joel Kolstad wrote:
Quote: "John Popelish" <jpopelish@rica.net> wrote in message
news:cdKdnSV8qfhFME7YnZ2dnUVZ_r3inZ2d@comcast.com...
As long as the viewer does not have a clear image of the two die in the LED,
the light will appear to be a single color.
Thanks John; I'm ordering a few to play with and see how it does. In an 0605
package I suspect that unless you're within inches of the LED you wouldn't be
able to discern the colors individually. (Harkening back to the time as a kid
you put your face up to the glass and realize that there are actually three
different colors there, all arranged in nice little triads...)
---Joel
its called pixel convergence ;)
followed by image convergence (when there are more than one pixel).
Cheers
Terry |
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| mkaras |
| Posted: Thu Feb 15, 2007 12:04 am |
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On Feb 14, 5:07 pm, "Michael A. Terrell"
....snip...
Quote: Just wait till they decide to build cheaper traffic lights by using a
single light housing, with bi-color LEDs to get Red, Green and Yellow.
I recall reading someplace that the multi-position lights are
necessary because of both color blind people and high sunlight
conditions where even people with normal vision cannot distinguish the
light color due to the ambient brightness.
- mkaras |
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| Michael A. Terrell |
| Posted: Thu Feb 15, 2007 1:45 am |
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mkaras wrote:
Quote:
On Feb 14, 5:07 pm, "Michael A. Terrell"
...snip...
Just wait till they decide to build cheaper traffic lights by using a
single light housing, with bi-color LEDs to get Red, Green and Yellow.
I recall reading someplace that the multi-position lights are
necessary because of both color blind people and high sunlight
conditions where even people with normal vision cannot distinguish the
light color due to the ambient brightness.
- mkaras
That won't stop some greedy politician from trying to have them
installed, so he can pocket the difference.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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| Rich Grise |
| Posted: Thu Feb 15, 2007 7:29 pm |
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On Wed, 14 Feb 2007 17:11:05 -0800, Joel Kolstad wrote:
Quote: "John Popelish" <jpopelish@rica.net> wrote in message
news:cdKdnSV8qfhFME7YnZ2dnUVZ_r3inZ2d@comcast.com...
As long as the viewer does not have a clear image of the two die in the
LED, the light will appear to be a single color.
Thanks John; I'm ordering a few to play with and see how it does. In an
0605 package I suspect that unless you're within inches of the LED you
wouldn't be able to discern the colors individually. (Harkening back to
the time as a kid you put your face up to the glass and realize that there
are actually three different colors there, all arranged in nice little
triads...)
I was absolutely astonished when I did this the first time - I could
resolve the individual dots, but I still saw the overall picture in
my peripheral vision, as if it were superimposed over the little dots.
Kinda boggled my mind, but when you're 8 or 10, that's not hard. ;-)
Cheers!
Rich |
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