WS2811 limits? Some colors don't work

L

Leea

New member
I am having a problem getting a long string to stay in the right color. I am a Newbie.
I have a Uno R3. The 2811 are 12V and I have a good power supply. The Arduino is powered by the USB cable.

If I make all my LEDs white it works good. If I try to make them blue it does not. The last ones either don't light or have the wrong color. I have 200. If I change the numpixels to 100 (leaving the other ones still connected) then the blue works. Why does white work and not blue? It is the same code, I just change from (250, 250, 250) to (100, 100, 250).

Thanks
Lee
 
Do you have grounds all connected from uno to the 12v supply and the leds?

Are your sure your strip/stings are all the same RGB/GRB/BRG protocol?

Have you tried supplying power to the back end or the middle of the strings?

Are you using fastled, neopixel or your own invention to drive the bits? If you are using a library, it is updated to latest? Or maybe you should roll back a few?

How are the strip/stings connected together?

BTW 100,100,250 is mainly but not really blue. Kind of pretty blue? What happens if you drive it with 0,0,250? or 250,0,0? or 0,250,0?

Put in a ramp from 0 to 255 and watch for glitches. If it starts out okay and then gets messed up as it gets brighter, check voltage at end of line.
 
Interesting test idea. (The ramp) I was being stubborn and thought that since white worked white must draw the most power therefore power must be good. Well ramping up told me that it gets to a point where the power drops off. So I measured the voltage at the end and wow, is it low.
I have to fix that first. Back to the drawing board.
Thanks
Lee
 
I was going to suggest that you put the first and last pixel in the string next to each other. I suspect you will notice a significant difference in hue and brightness. That is an indication of voltage drop.
 
Good idea but I already had it mounted so I can't do that. I suspect they will be different.
 
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