Is the pixelblaze v3 compatible with GS8208 LED strips?

Hello,

I am doing a lighting project and my client wants to use GS8208 LEDs. From what I’ve seen only the difference is whether or not the resistor and capacitor are in the pixel(WS) or outside on the PCB(GS).

Looking through the compatibility list, I am not seeing the GS8208 listed. Are these strips compatible, or do I need to request WS2018 strips?

Thanks in advance!
Mike

Hi Mike,
These are WS2812/WS2815 compatible but often come with default patterns that start up when they dont see data for a while. This can cause undesirable effects/glitches, but they are otherwise compatible. I don’t recommend them. I have heard that these have a variant without default patterns, but sourcing them might be a challege.

I ordered some GS8208 and have a much more favorable view now.

Summary:

  • Great 8 → 12 bit gamma correction
  • No default patterns on the ones I received
  • Power use is similar to the 12V WS2815
  • Unusually slow on v2
  • Backup data line
  • High (8000Hz) PWM films well

Sourcing

I bought this GS8208 strip at 5m, 60/m, IP67. It was $33 ($.11 per pixel in IP67) with free shipping and arrived in 15 days. Here’s the Datasheet. I wired the backup signal path, labeled D2 on the strip, to GND as it says to.

This version/vendor does not have any default patterns built-in. They do, however, all flash white for a quick moment when powered on, which helps scare the :poop: out of you for a brief moment every time.

Gamma curve

It’s really good - much better than the WS2812 or WS2815. It’s perceptually linear across the full range of the global brightness scale. It’s kind of like having APA102 / SK9822 dynamic range but at the lower Neopixel data speeds. The low end has rich minor gradations: Driving at 1/255 of red, green, or blue creates a tiny amount of light, so you can mix for browns and very low whites, and fine tune the color temperature of whites.

Pixelblaze v2

On a v2, they are very sensitive to timing. The only output settings that will work are the “Buffered (x2 rate) WS2812 / Neopixel” setting at the slowest possible timing, “1.3us / 2.6us”. This limited output to about 5,500 pixels / sec for trivial patterns (18 FPS for 300 pixels).

Pixelblaze v3

On a v3, the default WS2812 driver with it’s only data speed of 800 Kbps 270/630ns worked great. Trivial patterns got 25,800 pixels / sec out the door (95 FPS for 300 pixels)

Power and voltage drop

Like the 12V WS2815 and most 12V LEDs I’ve used, the current usage for any one color being on is the same as when all three LEDs in a chip are on.

As a 12V strip, powering all 300 LEDs across 5 meters at full white did not result in noticeable discoloration or red shift. Vin was 12.0 V, and voltage at the end was 9.4 V.

Nice!
Looks like a very in-depth test.

Do they only flash once, when they are powered on?
Or also periodically doing patterns?

Only once, very briefly, at initial power-on.

Hi @jeff ,
Interesting!!! I wonder what interaction is going on with V2, that setting was added in direct response to the first time I’d seen those type of LEDs and was the only setting I could get them to work on. I hadn’t seen that since (until recently), and figured it was a weird variant. There must be something particular about how the data lines are being interpreted that puts the GS8208 into a low speed 400KHz mode.

I think this can happen in other circumstances too. I’ve recently heard of some issues with these, but it wasn’t easily reproducible. I’d be interested in figuring out what triggers it exactly.

Without knowing more I’m hesitant to recommend these LEDs with PB officially, mainly because it could cause mysterious behavior that might be hard to troubleshoot. Also because if you do get a variant with the built-in patterns, they are aggressive enough on timeouts that it starts to play when there is the slightest pause in data stream (like on V2, loading the interface would trigger it), and it looks glitchy as it switches back and forth. I can imagine a pattern with a long beforeRender might trigger it too.

I think the white flash could be the “test” mode, which I’ve seen referenced in datasheets. I suspect they didn’t really disable “built in patterns” but replaced the pattern with something boring like white (and hopefully increased the timeout). I’m curious what happens if you disconnect data while leaving them powered. Thankfully the power use doesn’t increase with white compared to some full brightness color, but might prevent someone from under-budgeting power as the built in test mode wouldn’t care what max brightness setting you had.

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