RGBW Color Changing Demo System

The UI is simple.  Push down the encoder and turn to select the parameter you want to adjust. Turn encoder without pushing to adjust the parameter.  Hue is adjustable from 0 to 359 and rolls over. Hue of 0 is red, 120 is green and 240 is blue.  Hue is translated using the NTSC SRGB color space.  You may want a different color space depending on your preferences.  Hue translations are not absolute but are extended to get colors as deep as the LEDs are able to generate.  Saturation is from 0 to 100 and doesn’t roll over.  This adjusts how saturated the color is.  Zero saturation is white and as saturation is increased more color is added until a maximum color point is reached at 100.  Brightness is adjustable from 0 to 100.  From 0 to 10 a linear function is used to adjust the brightness from nothing to 1% of maximum brightness when a setting of 10 is used.  From 10 to 100 a logarithmic function is used so that a setting of 10 is 1% of maximum, 20 is 4%, 50 is 25%, 70 is 50% and 100 is 100%.  Using this brightness function is perceptibly fairly linear.  CCT is adjustable from 1700K to 8500K in 20K steps and does not roll over.  Duv is adjustable from 0.05 to -0.05 and doesn’t roll over.  Adjusting Duv adds color to a white while maintaining a particular CCT.  Plus Duv gives the white a green hue and minus gives magenta.

This is the UI with four channels of LED drive mounted in the box.  The drivers will source 0.67A per channel.  This amounts to around 12W per channel.  The current mixing algorithm limits the total panel power to under 20W.  

The attached panel is populated with discrete Cree XQA RGBW LEDs.  The panel may support over 50W of white power if needed.  The white on the panel shown is a 2700K Cree XQE with a CRI of 85.  Modeling shows that with a 2700K 95 CRI white CRI of over 90 can be maintained up to 3200K and CRI over 85 up to 3800K.  The panel will support the addition of another CCT white to increase the white tuning range at high CRI.  White power of the panel can be increased to over 50W if needed.