🚀 go-pugleaf

In article <1990Nov2.171429.28170@syssoft.com> tom@ssi.UUCP (Rodentia) writes:
>Anyone making a tricolor LED yet?  It seems that you could use 
>pulse width modulation to get a pixel of any color at relatively 
>low power.

Funny you should mention this,  I have been looking for such a beastie.

I programmed an antique MC68705P3L micro to step through R G and B PWM
duty cycles cyclically and Voila- a color pixel that changes through 4096
colors.  It doesn't really look like 4096 colors, but that is the resolution.
The biggest problem with this gadget is that the three colors of LEDs are in
separate packages and don't diffuse together very nicely.  The best mixing I
managed to get was by viewing the three LEDs from about 4 feet away using a
projector lens a few inches from my eyes.  The second method that I have
settled on is to put the 3 LEDs into a flashlight reflector and replace
the clear glass with some diffuse smoked glass.  There are still primary
color fringes on the edges.  A nice 3 color diffused LED in one package
would make for a much better pixel.

Why did I go to all of this trouble, you ask?
Mainly to satisfy my curiosity.
Could the world use an RS-232 controlled color pixel?

>Theoretically, how would power consumpion compare to LCD shutter 
>solutions?

Well, for a worst case scenario:  how about a decent resolution LED
screen of 1024 X 1024 and 3 LEDs per pixel at 20ma per LED:
1024 X 1024 X .02 X 3 = 63000 AMPS! (approximately)
Multiply that by approximately 2 volts per LED and you get 126KW.
That's for an all white screen, of course.
Color balance would be a nightmare too.
Of course, someone could just have a row of 1024 LEDs and a spinning
mirror and cut that down to a reasonable 120 Watts, but I don't know how
easy the optics would be or how bright the display would be.

--
 ^   ^  Forrest Cook - <<< We all P for IP, We all BM for IBM >>>
/|\ /|\ cook@stout.atd.ucar.edu WB0RIO (This posting is my OPINION)
/|\ /|\ {husc6|rutgers|ames|gatech}!ncar!stout!cook