Basic Schematic for Multiple WS2812 Neopixel Strings-Pixelblaze Capacity

I’ve got this schematic from BTF for their Neopixel strings (50 pixels per string -

BTF FAIRY STRINGSCHEMATIC 2.PNG

Question is, will this schematic work with Pixelblaze? And how many strings is it reasonable to run off each Pixelblaze? Looking at PB 3.0. I am interested in many parallel strings of from 100 to two hundred pixels each.

Thanks so much! And, greetings, since this is my first post here.

It will work. And forking the strands like that is just like running one strand: the data is mirrored not independent.

The “limits” of data are based on how many pixels are in series, not parallel.

If you want that many pixels to be all individually addressable, that is NOT the schematic.

If you want large scale, you add an expander which helps with the data distribution. See other posts on this forum about that.

2 Likes

That schematic shows 4 mirrored/duplicated strings, each that are 3 strings (50px) long, for 150px total from Pixelblaze’s perspective.

With an Output Expander as @Scruffynerf mentions, you can replace the splitters with 4 independent channels and get 4 addressable strings of 150px each, for 600px total.

Its good that they are also showing power injection! In either case, power is still important for the design, and you will want an external supply, it’s too much for USB. Also, it wouldn’t hurt to plan for another power injection point at the tail end if adding another string.

With strings in parallel, either V2 or V3 will be more than capable for 200 pixels.

1 Like

With absolute respect and an interest in understanding, I am wondering where this statement about PB applies, and how -

“Pixelblaze has a single output capable of supporting the various LED types up to 5,000 APA102 LED or 2500 WS2812 LEDs.”

I must be missing something! I really just for now want each string to have the same pattern.

OK. So now I see your comment, Scruffynerf, and thanks!

The “limits” of data are based on how many pixels are in series, not parallel. So, lots of mirrored parallel strings are possible, given adequate power injection. Correct?

1 Like

Hi @Gandalf,

Yep! Pixel data signals can be read by many strings at the same time. Each parallel path does not change how much calculation Pixelblaze has to do.

This line:

“Pixelblaze has a single output capable of supporting the various LED types up to 5,000 APA102 LED or 2500 WS2812 LEDs.”

Means that a very, very long string can be used before you hit hard limits. Practically, the maximum you would design a system for will depend on the frame rate you want to achieve, and for some patterns the memory available. Calculating a huge number of pixels will be slow, and the animation frame rate will be low and won’t look as smooth/fluid and would only be suitable for slow fading patterns.

For your number of pixels, 200, you will not run in to any of these limits or issues, and would have good frame rates and be able to run any of the patterns you like.

Here are the rendering benchmarks listed on the product page which can help you estimate your FPS
(frames per second) capability. I would note that it will be slightly lower for WS2812 type LEDs, and the tests were done with APA102 type LEDs, but you can still use this to get an idea:

Using included patterns as a benchmark, Pixelblaze V2 can generate between 12,000-45,000 pixels per second.

  • 100 LEDs: 120-400+ FPS (very fast animations, special effects, POV)
  • 1000 LEDs: 12-40+FPS (animations, backgrounds)
  • 5000 LEDS: 2-4+ FPS (slow-fading backgrounds, ambiance)

From this data you can see that 200 pixels will give you very good frame rates on V2.

The new Pixelblaze V3 is on average 2.6X faster, while maintaining the same 5,000/2,500 pixel maximum:

Pixel Count FPS Possible Applications
100 300-600+ Extremely fast/smooth animations, special effects, POV (persistence of vision)
1000 30-65+ Beautifuly smooth animations
5000 6-13+ Gradual animations, fading backgrounds, ambiance
3 Likes

Welcome!

This is a topic I feel a little embarrassed about - I wish I remembered more of my undergrad for the fundamentals. But let me share a recent story that covers your situation and matches my experience as well:

So you’ll want to google “'SPI splitters”. Note that most of these devices don’t spec their max bandwidth, so while most Neopixels and SPI or DMX splitters are good under 0.5Mbps, you might need a different type of splitter for APA102/SK9822/Dotstar.

2 Likes

This is ALL great stuff! Such good communication!
I’m wondering if the basic design of your Volumetric Cube could be extended with 64 strings say 50 to 100 pixels long… ?

Last time I thought about this “sloshing about” of signals in electrical circuits it was in the strictly analogue world. This issue will be good to keep in mind as I dig deeper into this. Thanks for commenting!

We’ve answered my basic question, thanks, each channel can run a multitude of LEDs… so, with that info on frame-rate and pixel count I should be golden, this is great!

Wondering how parallel strings are treated in address/mapper-space…

I’m thinking of paralleling strings with pixels back to back for better spatial distribution of light.

Any comments?

Thanks as always!

If you mean forking the data line, so line 1 and line 2 share the data, that’s invisible to PB, and works fine. They will mirror each other exactly.