New Person, First PB Project, Checking on Spec

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#1

Hey all! This looks like a very helpful place, so since I just ordered a full PB setup with an output and sensor expander I wanted to check on something.

I’m building a project that right now has 8 channels (though it might need a few more in the future.) Two of those channels have 203 SK6812 RGBW pixels, two have 59, and four are running 60 LED RGBW Adafruit Neopixel Rings. Grand total of 764 pixels.

Now, I’m not the most technical person, but I’m thinking that my 5V40A power supply should be sufficient if I’m not running them all at full brightness, but I wanted to check on the individual channels. I see that the expander has an amperage limit of 3A, but it should be fine if I’m powering them separately, correct?

I also see that I can power the PB off the 5V going into the strips, but is there a best practice for that?

Super excited to receive my kit and start making awesome animations with you all!

#2

Welcome!

It sounds to me like your setup should work just fine. PB is one of those astounding things that ‘just works’.

I think you’re right that the 3A limit on the expander is just for power going through it, so powering the strips directly will work fine. I have strips with a 3 or 4 wire 5V/data/[sometimes clock]/ground JST connector beside two 5V/ground wires. I use the separate wires to supply power at the data-in end, then I plug the PB into the JST connector and it works fine.

A capacitor might help shield the PB from power fluctuations but I’ve never had to do that.

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#3

Great! Thanks! I was planning to use a 1k uf cap for all of the power hookups.

#4

Yep, you just don’t want 40A running through the small expander board. It’s happy to drive data for that many LEDs. Just connect GND as well so the data signals have a nice solid reference.

The Pro Expander can do 15A (based on connector ratings), and has fuse protection. Either way I’d recommend fuses in case there’s ever a short.

Ideally you want solid power to PB, as much as possible. Keep PB on the closer side of wiring to the power supply. Put another way: when sharing with LEDs avoid powering PB from the far end of the strip/string, since that is the noisiest and has the most voltage drop. Running a separate set of power to PB can also help reduce how much drop/noise it sees when the LEDs draw power.

#5

Thanks! I’ll make sure the 5V to the PB is solid or separately wired, and throw some fuses on the lines as well.

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#6

Quick question, I might post a video link later if i can’t figure it out.

Got my PB all set up, works great, but I’m getting some random seeming white led flashing on both my rings and strips. White LED at the start of the pixels, and then randomly running up and down the line. I have a 1k cap across the 5v in, but removing that didn’t do anything.

Double checked all my settings, and I seem okay on all of them. Any ideas? Thanks!

#7

I fixed my problem. I disconnected the ground between the PS and the PB at some point. Doh!

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