Best driver for WS2811?
Phil Pilgrim (PhiPi)
Posts: 23,514
I've been tasked with creating special effects for a high school play. I was planning to use a "wall" full of WS2811 LED strings:
I received the strings today and hooked one strand up to my Propeller Activity Board through a 3.3V - 5V level translator and powered it with a 12V DC supply. I wrote a quick program that uses the attached LED driver, but I'm getting weird behavior. It seems that this driver keeps sending data streams even though use is not called again. As a consequence, I get a lot of flicker on the selected LEDs , and the colors are wrong. If I force the driver to stop, some of the LEDs display the correct colors without flicker. I think this driver would work if the PASM portion would send the data stream only once after use is called and let the WS2811s continue to refresh on their own.
Is this still the best driver for the WS2811s, or is there an update I'm not aware of — or better a driver?
Thanks,
-Phil
Comments
In my opinion and a lot of people in the tv/movie business who use it, it is!
The reason for the auto refresh is to allow dynamic animation. Several people that use the driver will modify the buffer on-the-fly. The use() method allows you to change the buffer pointer or output pin.
When there is color wonkiness it's usually caused by a short reset period. Consider extending that to a millisecond or two (10 or 20 for reset parameter).
Even thought I used this driver with WS2811 Christmas bulbs last year without troubles, I had a look and did a little tuning with an LA. My preferred board is an EFX-TEK HC-8+ that has TC4427s to provide stiff 5v outputs for servos and signals like this.
Hi Jon,
Thanks for the quick response! The updated driver didn't change anything. But now I'm tracking down some noise on the 12V power supply that might be the culprit.
BTW, I'll be using RS485 signalling for the data line, since the distance to the first LED could be quite long. In my test setup, I'm using one LTC485 set up to echo its output in order to simulate what the WS2811 will experience. The signal looks very clean, except for the glitches that I suspect are coming from the 12V supply.
-Phil
It was the power supply, which outputs huge switching spikes. It's going back to Amazon.
Hooked up to my bench supply now, and things work as expected.
Thanks, Jon!
-Phil
Great detective work, Phil!
I'm actually glad that things turned out the way they did with the bum PS. I had to demo one strand at the HS yesterday, and the only portable power supply I could find in my shop was a regulated 12V 2A wall wart. It worked fine.
So today I decided to stress things to see how many strands I could light up with full-on white and the power supplied just at one end. I got up to four when I decided to quit, since the voltage at the end had dropped to just over 5V. But the last LED was just as bright as the first. This is way better than my experience with WS2812B strands that run on 5V.
This tells me that I really don't need a 200W supply after all, and can settle for something smaller but of better quality, such as a supply made by Mean Well.
Still, I'll probably provide power to every other strand just to maintain a good margin against voltage drop.
-Phil
I haven't used the WS2811, but they sound like a lot of fun, for Halloween coming up say. Phil, and Jon, are all the strings you find on Amazon the same as far as addressing and color rendering; some you would prefer, some not? Either strips or strings.
I acted in Midsummer myself in high school. A minor part. I'd hooked a few electroluminescent panels to the sound system. But one of them blew out, loaded the system and cut the volume. The director was not pleased.
Tracy,
This is the kit I bought for the play:
https://www.amazon.com/ALITOVE-Diffused-Individually-Addressable-Waterproof/dp/B06XSFT1VK/ref=sr_1_8
I've had good luck with Alitove products overall. And I highly recommend the WS2811 strings over the WS2812's, just because they operate on 12V, and you can operate a lot longer continuous string without an additional power-tap cable. I'm operating 350 LEDs, just end-fed with power. (Of course, if I set them all to white, I'd see some fall-off in the blues at the end.)
Be sure to use a good-quality PS with minimal switching noise. Also, I recommend the RS485 approach if the cable from the controller to the LED string is long. Oh, and Jon's LED driver is great! I'm making very extensive use of his fade (scale_rgbw) method.
I'll take your HS experience as a warning and be careful not to connect anything to existing systems!
-Phil
P.S. I haven't forgotten your inquiry about air-quality PCBs. Other stuff has intruded.
I'll get one of the short strings to try. Am I right in thinking that any of the strips, strings, circles, badges, plaques, Christmas trees etc. etc. found for example on the Adafruit web site would be fair game for Jon's driver? I see that the driver accommodates slight differences from various chips.
I do still like the subtle effect of electroluminescence. Ghostly and of course big on the Playa. The ones I had back in high school were panels from night lights.
Yes. I've run that driver with lots of pixel types (hence the various start methods in the driver).
I'm virtually certain that that's a fair conclusion.
I remember those blue-green night lights from my childhood: round discs about three inches in diameter. We had one in our entry foyer. They wore out over time, as the phosphors seemed to degrade -- not sure of the process, though.
BTW, you can create a reasonable nightlight by applying 110VAC to the opposite ends of a dill pickle.
-Phil