WS2812 fliker, only when bright white

Troubleshooting
1

I’ve run across a strange problem…

WS2812 running at 444ns - 15Amp 24Volt power supply, Grounds tied together
14ft or so long strip, which is fed by a 20ft long 18awg, 3 conductor cable

Only when sending white, there is a flicker…

Turning brightness down, and it goes away
Send any pattern, or solid color, and there is no problem, even at full brightness

Is this a voltage drop issue at the far end of the strip?
Could I solve it by wiring 24V to the far end?

Could I solve it by using a pattern for white that only sends it once, as opposed to re-sending it constantly?

Currently for “white” I’m using the following patterns…

export function render(index) {
hsv(1, 0, 1)
}

or…

export function render(index) {
rgb(1, 1, 1)
}

Is there a clever way to just send it once and leave it?

2

That it’s only at full brightness white says it’s entirely power related. Is it fed with power at the far end? (Oh, clearly not, since you asked if this would help. Yes. It would.)

3

Hi @jpm,
That sounds like a power issue.

Voltage drop works both ways. Both the positive and negative side get closer to each other in voltage. The positive side droops, and the negative side rises!

You didn’t say how many LEDs or the total current draw, but if you are getting anywhere near 15A with a 20ft run of 18 AWG will drop (or raise) almost 2V to the first pixel on each side, both the positive and negative side. Thats enough to really mess with the data signal.

It could also be really noisy (non-stable voltage) at those high current draw levels. You could try adding some capacitors near the LEDs to smooth things out.