Can someone tell me in nm what the optimal three wavelengths are for
RGB color?
Since you are talking about LEDs, you will have to work with what
exists or else contract to get some existing LED 'pushed' a little one
way or another. Keep in mind, LEDs emit over a broad range, not some
narrow line. So human perception of all of that will need to be taken
into account for what you are planning to do.
I want to try simulating this on a small scale with three individual,
high intensity LED's.
Some folks have already gone to some trouble to develop tri-color LED
systems that achieve usable range of perceived color and high a fair
degree of brightness, so that they can be used outdoors in broad
daylight. Unless your needs are unusual, this is a market area you
should examine to see what others have done here.
Second, related, question. Please excuse.
By varying the intensity of the three colors of LED's, I am looking to
produce a seamless shift across the entire color spectrum.
Understood.
What kind of dimming circuit would best suit this application? I have
seen current based ones, but was wondering if some kind of PWM might
be more linear.
The systems I've worked on use DACs to set an appropriate "white
point" balance between the LEDs. This may be 100% or 25% or some
other reference figure and the PWM is fixed during this calibration.
But the idea is to tweak the white point to where you want it and then
to PWM for brightness or for relative color change.
However, you will need to be familiar with CIE color curves and how to
compute brightness and normalized (x,y) to use against your white
point to generate an apparent hue. You will need to invert this
process if you intend to drive the hue and need to develop (x,y)
values to get there. That will probably involve a calibration step
with your tri-color LED (can be performed at most any set PWM level --
even different PWMs for each color, if you like) to develop the matrix
and then invert it for use.
I've done some of what you are trying to do in a practical system that
met my needs.
Thank you kindly for any advice.
No problem. I can recommend a book or two, if you are interested in
human perception of colors and brightness. Lots and lots of research
articles (some very fine ones from Edmund Land back around circa the
last 1970s and early 1980s, if memory serves, too.)
Jon
