RGB LED colour mixing

[Dave_H]

I came across this interesting (though very detailed) article on calculation of RGB mix
ratio for LEDs to get "white", whatever it might amount to.

https://www.ledsmagazine.com/smart-...-optimal-color-in-signs-and-displays-magazine


Apart from background info, it might come in useful for at least a good starting point to
synthesize white from RGB. I came close to this, but the PWM controller at the time had
only two channels (!) so ended up getting shades of aqua, purple etc. just playing around.

It also helps to explain why some low-cost LED products don't always do such a great job
of this. A couple of RGB strips and ac bulbs I have tried tend to create distinct bluish-white,
which seemed to get more pronounced with cold temperature (outside). Other factors would
include initial LED matching/binning and changes over aging.

One battery-powered bulb uses RGB plus white LEDs to get around this, although has a fixed
tint for white.

Another colour mix is orange from red plus green, which I've seen used in a few products.
LEDs were placed close together and light mixed in lightpipe.

Also interesting that early Red/Green LEDs in 5mm 2-lead package were connected inverse
parallel so could only light one at a time, so could not get orange; but if alternated
at high speed, gives appearance of yellow (not orange), a sort of "optical illusion".

Dave

 

[DIWdiver]

Dave,

Interesting article.

I often put battery indicators in my products. You can get red, orange, and green from just red and green, but you have to get the right wavelengths or the red and orange are hard to distinguish.