Hello all,
I've been tinkering with a 16F88 and some RGB (actually RGBB) LEDs.  I
can successfully PWM the LED at 256 different linear duty cycles per
color resulting in 24-bit color possibilities.  This looks pretty good
when ramping the colors up and down.

Now the crux of the problem.  I would like to vary all three colors
continuously so that I end up with a good assortment of mixes.  The
problem is that no matter what kind of algorithms I come up with they
either take way to long to cycle thru or they repeat and miss allot of
colors I'd like to see.  I can change LED colors up to every 13mS (one
full period time) without causing ugly flashing.  To hit all 16 million
possible values would take about 60 hours, so this is not practical.

What I've been doing is to use a perpetual loop that ramps the dutycycle
all the way up and then ramp it back down (not allowing the value to
stay at 0).  The duty cycle of each color is varied by it's own delta
value (1, -1, 2 etc..).  I've experimented with different delta values
and starting duty cycles.  I get lots of nice colors, but not what I
really want.  What I need is some kind of randomization or some ideas
for a good algorithm that would allow me to cycle thru a virtual rainbow
(ideal).  I need smooth, virtually imperceptible color changing.  I
would like for the "show" to take about 1 or 2 minutes.

I currently use a pot to set the delay between color changes from 0 to
255mS so that I can settle on a final delay value empirically.  The
maximum acceptable update rate for the duty cycles is approx 80Hz or
strange flashing occurs.

Thanks for any ideas


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