anders tonfeldt

WS2811 LEDs / neopixels, cap them all!
2015-11-23 22:30

I just facepalmed harder than I have in years. I've been working with ws2811 through hole rgb leds, they're usually referred to as neopixels these days. For some reason strips of the stuff would work great, but the regular led format would blink or flash the wrong colour every now and then.

Driving myself nuts in the process I tried -everything- going so far as plugging my bench power supply into another room and even changing out the prototype board. Then I realized I had broken the cardinal rule, if there's voltage in then cap it!

If your leds are flashing or blinking erratically every now and then then simply put a 0.1uf bypass cap on its vin and ground. It'll stabilize its drain preventing timing errors.

Do -not- be tricked by the data signal getting mangled by the 2811s, apparently that's normal. I spent oh so much time trying to clean up the signal as it got passed from led to led to no avail. Below you can see the data-in for the first led in the chain indicated by the blue/ch1 line. As you can see, very clean due to the resistor. But then the second led's data-in, yellow/ch2, is spiking. This seemed like an obvious problem to me, but it wasn't. It was just the drain.

Cap dem inputs!


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