I'm just genuinely confused.
And so are we. What you report is not possible so there is something wrong that you are not telling us. We have had some guesses and you say it is not that so we are waiting for your schematic to throw some light on the situation.
Yep, I'm just at work at the moment so once I get home I'll be making a schematic. Any particular recommendations for a software package to do that with? Otherwise I'll go with ExpressSCH.
My very first test with these pancake RGB LEDs was with a multimeter on diode/continuity mode. I use that to test LEDs a lot, since it's high enough voltage to light one up, but is current-limited enough that it's not particularly bright.
So, with one of these LEDs in hand, I tested all the pin combinations (my data sheet was a little more helpful, but not much) to find the one pin that seemed to be the constant required to illuminate all of the colors. Great. So, then, I tried shorting the R and G pins to make yellow. Nope. The R and B pins to make purple. Nope. The B and G pins to make cyan. Nope. If I set the tip of my probe on one color and rocked it over to touch another, the first would be lit up until I touched the second, which would stay lit until I rocked the other way, then the first would come back on.
I think Grumpy is on to something here. I bet what is happening is that the lower forward voltage diode is pulling the supply down enough that the higher forward LEDs are no longer lit. Isolating each internal diode with current limiting resistors would probably fix that . . . Huh, glad I stopped by this thread.
centizen:
Any particular recommendations for a software package to do that with?
It is called pencil and paper, photograph the results and post.
thank you for the recommendation for the three grounds and resistor on Adafruit.
Three things. First, you need 3 separate resistors, one in each Led cathode line, in
case you're not doing that.
Secondly, if you check the datasheet [which is one of the worst I've seen yet - they
show no schematic and 2 A's and 2 C's, rather than 1 A and 3 C's like adafruit says],
you'll see the d/s mentions needing 3.8V to turn on the green Led, so it won't light if
you have only 3.3V.
Thirdly, the d/s says 3.8V for green, but it's usually the blue that takes the most voltage
to turn on.