I would be grateful for feedback on whether driver 1000-2000 WS2811 pixels would benefit from a [Pro] Output Expander. Specifically I’m wondering whether the splitting the data lines from the controller would improve the performance in any way (e.g. refresh rate) compared to using a single data line.
More detail about my use case
I plan to migrate from a home-made setup to Pixelblaze in order to use Pixelblaze’s 3D mapping capabilities. I currently drive 1000 WS2811 pixels using a RaspberryPi Zero with a level shifter, and 60 W A power supply. There is a single data line, running from the level shifter through all the light strings in series, with power injection points spaced throughout the line. I may soon expand to 2000 pixels, still well below the limit of what one Pixelblaze controller can drive (5000 pixels).
It seems the simplest thing would be to swap a Pixelblaze V3 Standard to replace my RaspberryPi Zero, and leave everything else as it is. Would adding the [Pro] Output Expander bring any advantages in this case? It wouldn’t help with power distribution: the Pro only scales to 15 A, which I’m well beyond (~30mA/pixel x 1000 pixels = ~30 A), and I already have an adequate power supply with safety features. Would there be any advantages to using the multiple data lines instead of one long data line? My guess is “no”, that what matters is the number of controllers, and that splitting one controller across multiple data lines cannot improve the refresh rate. But I would be interested in an opinion from someone with hands-on experience.
Use a Pro Expander (over a normal expander) when the pluggable terminals or fused power distribution make it worth the premium to you. They’re especially good for 12V projects, given the 15A distribution limit. A calculation that a lot of people don’t do is the value of their time in all the wiring, which is why I commonly reach for a Pro expander whenever I’m billing a client for my time. If it saves me an hour of making wire harnesses, it’s worth it.
I see you meant 60A supply; so yes, you’ll want to do your own power distribution and fusing, and the Pro could work for power distro if you wanted to wire <=500 pixels per expander. Fast frame rates for sure using one expander per 500 pixels, but also consider the overall pixel render rate per PB: ~48Kpixels per second. So while it will allow you to compute up to 5000 pixels of data, when you configure it for 2000 pixels, you’re getting 48K/2K = 24 FPS - you’re right on the margin where splitting the project to a second PB in sync mode may give you the frame rate flexibility (up to 48 FPS) that will look best.
Multiple data lines, or “channels”, do the following:
They’re a nice wiring convenience for star topologies
They can double the data rate possible when limited by WS281X protocol speed
They can provide isolation so sections can fail independently
They let you keep your serial runs under some number of pixels (500, 250, or 170 per channel are common choices) which is better for signal reliability over longer distances.
The following threads will give you some more insight into how to do the math to predict the speedup from using an output expander with WS2811s:
To summarize my understanding for anyone finding this later:
A solid implementation for my use case would involve 2 synced PBs (for frame rate) and an output expander for each PB (for convenience, failure isolation, reliability, and some additional frame rate). The choice of Pro vs not is time versus money. The value-add is diminished in this instance by my choice of 5V pixels and a total current which requires that I do my own power distribution, but there would still be some benefit to the convenient data channel hook-ups on the Pro.