RGB Led Strip

Hi,

I’m trying to control a rgb led strip with my FEZ Domino. I wan’t to cycle through colors in the end with a webpage where I can select a color and the strip is set to that color.

This is what I tried:


static PWM red = new PWM((PWM.Pin)FEZ_Pin.PWM.Di10);
static PWM green = new PWM((PWM.Pin)FEZ_Pin.PWM.Di9);
static PWM blue = new PWM((PWM.Pin)FEZ_Pin.PWM.Di8);

red.Set(20000, 10);
blue.Set(20000, 0);
green.Set(20000, 0);

The red lights up more then the other colors, but I can’t set the other colors to “black” (off). Does anyone have some sample RGB PWM code?

Thanks!

Ramon

This looks correct, you probably have the wiring wrong?

Well, actually it does work, I can set the different colors, but I just can’t seem to set it to one color only… if I set red to 10, blue to 0 and green to 0 I expect only the red led’s to light up (a bit) and the blue and green stay off, but they all light up a bit, the red a bit more then the others…

10 and 0 are very close numbers

Try 90 and 10, instead of 100 and 0.

The human eye does not see pwn pulsed light as a linear scale. Usualy devices using PWM to dim lights are using a “gamma table” for convert linear human light levels to PWM %. For an example the human eyes sees no difference between 75 and 100% PWM.

This is all about the difference between Luminance vs. Brightness

Some interesting information : http://arduino.cc/forum/index.php?topic=69083.0

Have fun :wink:

Hi

The eye responds differently to the different colors. Try to use for green 0.5 of what you want.
At least my RGB leds show white only with R and B values doubled compared to the G value.

Normally RGB Leds are designed taking this into account and the 3 chips are of different “light-power” (given either in millicanda or lumen) so that the sum of all 3 with the same current should give white.