Making yellow from bi-color (red/green) LEDs
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Posted by Joel Kolstad on February 14, 2007, 7:42 pm
Please log in for more thread options 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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Posted by John Popelish on February 14, 2007, 8:01 pm
Please log in for more thread options Joel Kolstad wrote: 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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Posted by Joel Kolstad on February 14, 2007, 8:11 pm
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> 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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Posted by Terry Given on February 14, 2007, 9:32 pm
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Joel Kolstad wrote: >
>>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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Posted by Rich Grise on February 15, 2007, 6:29 pm
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On Wed, 14 Feb 2007 17:11:05 -0800, Joel Kolstad wrote: >> 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 | |||||||||||||||||||
> 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?