Paralysis of Analysis – Pixel types – My first display journey

[ThomasCee]

What a refreshing group. You Christmas loving peeps are amazing. I'm new, and thought I better start my own thread rather than inadvertently hijacking others with my learning.

That GS2808 thread sold me on starting with them, either China-direct from Ray Wu, Paul from Etop, Shiji-leds, or alternatively a local reseller.

@merryoncherry, you mentioned:

I run a few thousand of the duos. There are reasons 8208 haven't really taken off, despite technical merits.

Can you or others elaborate? Am I shooting myself in the foot going the 8208 route? They look great on paper as you say.

Furthermore, I asked about the NBG type pixels on the image below and you mentioned:

All of these little 12V pixels like the ones in your image have the power efficiency of the 8208s also (and generally use less current, so have much lower peak power usage). They're not based on discrete chips (WS2811, GS8208) on PCBs, they're based on little LED modules that are soldered directly to the wires. They're wonderful in the cases where you can use them (HDPEs, tree strips), but mixed results in coros. You can get just about anything on Ali, but there are several US vendors stocking a variety of these domes if you need them in a hurry. (Scott, Yvette, Wally's lights, etc.).

So I guessssssss.....
To tie together my question...

– 8208 looked promising for a pixel/node type.
– NBG/Dome style (not sure what else to call them; but not chip based, only an LED module (I'm seeing RGB and RGBW, the latter of which I would assume would be the most efficient) )
– Evo's (or are they "Duo's?"; they are yet a different type? Related to the NBG/Dome style? Or are they a completely different animal?

Hope that wasn't too many questions in one post

 

[Skymaster]

– Evo's (or are they "Duo's?"; they are yet a different type? Related to the NBG/Dome style? Or are they a completely different animal?

EVOs and Duo's are two different thing.

Duo's are essentially GS8208, aptly named because of ther "Dual Data" - this is more just fancy branding by YourPixelStore than anything official.
EVO's are a seed pixel in a tranparent 12mm encasing. Similar to the gumdrops pictured above, but more directed. They were first marketed by Mattos I believe, and others have copied them.

 

[merryoncherry]

Analysis paralysis, one of my favorite games. There are so many dimensions one can look at: voltage tolerance, brightness, color reproduction (gamma, RGB vs RGBW WW A UV etc), reliability, efficiency, form factor and other mechanical considerations, price, availability, connectors, protocol compatibility, power injection requirements (which involves the wire used in final assembly, not just the chips), software support, etc. But I've bought a lot of samples and tried a lot of things... and so much of it just works that it's more fun to "just do it". If it looks good, it is good.

Before diving in, here's some fun background watching about how the modules are made (see thread https://auschristmaslighting.com/th...-tour-of-pixel-panel-etc-manufacturers.15938/). The modules have the LEDs and a little control chip embedded inside, and are suitable for soldering directly onto flexible PCBs to make strip, or onto wires to make seed pixels (which, in turn, can have various shapes molded around them, little seeds, gumdrops, domes, blackout gumdrops/domes, gems, discs, etc.

View: https://youtu.be/pMjhJ9kcaU4


The other common way is the discrete chip (WS2811, GS8208, UCS1903, etc.) that is soldered onto a board with an LED and embedded in epoxy.

View: https://www.youtube.com/watch?v=AIAhI841nFE


But, rather than wandering aimlessly through let's pick apart the GS8208 as a specific example (and whether it should be popular or not).
The GS8208 is a discrete chip, and its tells us a lot about its voltage tolerance, brightness, power use, etc. Unlike the WS2811, it is a series design, meaning that the same current flow goes through the R, G, and B LEDs, and the design current is 18-20mA. This means about 75% of the voltage goes to the LEDs rather than being wasted on the board, that the peak power use would be ~.25W, and that the brightness would be "20mA worth". Relative to 5V WS2811 LEDs, this is the same brightness, and a slight efficiency boost. Relative to 12V regulated designs (which take .6-.7W for the same brightness), this is a huge efficiency boost. Relative to 12V resistor designs (still the most common design for bullet pixels), this is a huge efficiency boost, and a max brightness boost, as the resistor pixels are usually limited to 10-11mA per color instead of 18-20. Note that the peak 8208 brightness is far more than most people want... a lot of people are dimming even the 10mA pixels.

You might think that the efficiency win of the 8208 would lead to it needing less power injection. This is not true in practice. As the LEDs are in series, it needs 9-10V to operate, whereas the resistors will work (albeit dimly and greenishly) at 6V, and regulators continue to work normally at that voltage. Also, the 8208 is a 4-wire design, and the manufacturers often use a thinner wire to squeeze that in, which means more voltage drop. So there is not a win here vs the 2811.

As the GS8208 is a discrete chip, the form factor tends to be bullet nodes and square nodes. The bullet nodes are great for coros, as coros are designed for this. They "drop in", where a lot of the module-based pixels do not, or bleed throught the coro, etc. (Note that all the little seed pixels, gumdrops, gems, evos, and other module-based pixels generally have the same series design, and half the current rating, so they are tiny, efficient, and low power.) Anyway, this is a "pro" if you are using coros, and a "con" if you are using anything else as there are lighter and tighter solutions.

The gamma correction in the GS8208 makes it reproduce dim colors better than pretty much anything else that is RGB. It's totally true, and easy to contrive situations where you can see it clearly, but not a lot of viewers are going to notice this.

Reliability-wise, the dual data is supposed to make it so that loss of a pixel does not disrupt the rest of the string. In practice, reliability has a lot more to do with the implementation than the theory. I've had to replace a few of my YPS duos because they wouldn't turn off, and started to get warm. My best guess is that it is the epoxy on some is softer than it should be, and this is allowing moisture in, so not a problem with the chip itself. On the other hand, WS2811s have been largely solid, excepting a lot of bad batches in 2022 that had to be completely replaced. Modules are much simpler, a lot more automation in production, a lot less components, so in theory they will be more reliable, but only time will tell for sure. Anyway, from a popularity perspective, dual-data solves a problem that a lot of people don't think they have.

Price/Availability: GS pixels cost a lot more and are available in a lot less places (direct from China, YPS).

Connectors: 4-pin xConnect is another thing to deal with. To make matters worse, I got incorrectly-wired adapters with my first batches of GS pixels, and the 4-wire evo pixels use a different pinout, and all the 3->4 pin adapters are visually identical. I finally tossed out all the defective adapters, and also gave away the incompatible pixels to make my life easier, but what a mess!

Protocol compatibility and software support: They just work with all the rest.

Other: The GS8208 has built in self testing stuff. If you supply power and no data, they will eventually start doing a little synchronized light show all by themselves, which may not be what you want. Also, as the dual-data design would obscure manufacturing defects in the data lines, the pixels self-test for this, lighting up the ones that are not working properly. However, the manufacturer did not care to use this / sent out strings regardless of these defects, so a couple pixels stay on during the self tests. This does all have a workaround - send black data all the time.

Recap as to why the GS8208 probably hasn't stormed the market despite some technical merits:
Pros:
Brightness (albeit that a lot of people won't use it)
Efficiency
Color reproduction (as far as RGB goes)
Works like "WS2811" from a controller and software perspective

Cons:
Price
Availability
4-pin connectors
Self-test dances require black data be sent all the time
Distance to power (depending on wire and dimming used)

Situational:
Bullet form factor fits perfectly in coros, but is not the lightest / tightest solution for most other use cases
Reliability

 

[ryanschristmaslights]

Great informative post @merryoncherry ! Just on the price, they are coming down. From the same supplier in 2021 where the GS8208 cost US$0.35 per bullet pixel, this year they were only US$0.17 (for same string specification).

 

[merryoncherry]

Just on the price, they are coming down. From the same supplier in 2021 where the GS8208 cost US$0.35 per bullet pixel, this year they were only US$0.17 (for same string specification).

Wow, I have to keep an eye out for that ... the only pixel I can get delivered right now for ~$.17 is plain resistor pixels from ScottLED (USA).