controller for WS28xx series digital LED tape

[KevinE]

I've been handed some WS28xx (prob 2811) based RGB digital tape and asked to sort out a controller for it...preferably one that's DMX controllable.

 

There's plenty of WS28xx 'DMX decoders' for sale on ebay etc. It appears to becoming a rapidly standard system for digital tape or addressable LED strings.

 

My question is, are all WS28 series tapes pretty compatible, data-wise (protocol)? It's apparently 24-bit data word 400khz serial, with RGB data arranged as 8-bits for each colour. DMX must of course be able to command the 'controller' to do the clever stuff/patterns/dimming etc.

 

I havent got time or the budget to reverse-engineer it or get involved in writing programs for arduino or pic etc.

 

Any prior experience gratefully received :)

[timsabre]

There are 2 flavours, 400khz and 800khz. All the stuff I've got seems to be 800. The ebay Chinese type controllers mostly do extremely boring / basic patterns. I've spent the last few months writing software for a controller for AbstractAVR which does some more imaginative stuff; there are a few others out there mostly designed for TV set work.

[gyro_gearloose]

The WS2812/WS2812B are basically LEDs with a WS2811 chip embedded in them, so they use the same protocol. The WS2801 needs ann additional clock line running to it, whereas the WS2811/12/12B don't. I foundthis controlleron ebay which would appear to control all variants of the WS28xx family. The same guy also has some Artnet/ACN to DMX convertors for very little money.

[maeterlinck]

As gearloose says WS2811/12/S/B etc all use the same serial 1 wire protocol. WS2801 use a 2 wire protocol (Clock and Data). So first require 3 lines, power and data, second require 4, power, data and clock.

 

If there is a chip on the tape then that will tell you what is driving it, if there is no chip on LEDs in 5050 form, then it will be WS2812. (I'm not aware on another all in one chip..?)

 

Most tape is 5vDC.

 

It's pretty trivial to control them, hence the large number of cheap controllers.

 

Enttec do a nice all in one controller with transcoder and power supplies all in one unit. DMX4all also do board only and boxed controllers (no PSU) which will control most varities of string.

[musht]

Remember that you only get 170 pix to the universe.

[timsabre]

Only if you address the Leds individually. If you use a controller with built-in macro patterns, which is what I think Kevin was referring to, then you only need a few channels to control all the Leds. Finding one of these with good macro patterns is the hard bit. Most do very basic chases.

[Geetrt]

You can ofcourse get a Sandevices or j1sys controller,, and use chamsys magicq to control them via 64 artnet universes.. Then you can do whatever you want.

[maeterlinck]

Only if you address the Leds individually. If you use a controller with built-in macro patterns

I've seen a few that allow user programmed sequences to be recalled via DMX. Think one of the DMX4all products allows this. There are lots of chinese controllers that allow user recordable shows, how good the software is though...

 

Edit: Pixel grouping is also an option.

[KevinE]

That's all very useful. I've peeled the tape apart and it uses an RGB led module driven off WS2811B ic's. The tape is 3-wire 12V. I might try one of the cheap chinese controllers to see what happens.

 

NJD do a handheld programmable LCD controller for their own digital tape, would be interesting to see what system that uses.

[timsabre]

Are you sure it's 12V? These individual pixel tapes are normally 5V. The 12V tapes usually have the LEDs grouped in 3's.

[KevinE]

Yeah the tape is marked 0V, DAT and 12V. But I can wind it up on the thurlby just to be safe

[KevinE]

In the end I bought the board linked-to by gearloose.

 

It works just fine, is nicely built and comes with jumpers to run either 5V or 12V tape. However it's very fussy about noise on the power line in 5V mode as the micro isn't adequately decoupled from the supply...I will look into this for 5V applications.

 

I've sourced the DMX via Freestyler PC and the latest revision can drive 2 universes. There's an RGB matrix utility (LEDTrix) with that and after some time trying to get it to work, finally managed to do it..it has a bug which means that certain vga colour modes can 'block' the generation of any DMX data at all..I had to set windows to 24-bit colour even before the on-screen previews would work.

[gyro_gearloose]

However it's very fussy about noise on the power line in 5V mode as the micro isn't adequately decoupled from the supply...I will look into this for 5V applications.

One idea I had while looking at these controllers is to use a simple transformer based 24vdc/DMX supply box, exactly like a scroller power supply. Power and data would then be fed down 4 pin XLRs. Each controller would then have a 5v dc-to-dc supply (probably switched mode) local to each 2812 controller board. Would this help with power supply noise issues?

 

Edit: I had a email conversation with the guy that makes the boards I linked to a few posts back. I had an idea for his boards where instead of controlling each pixel individually, each pixel gets the same RGB data. The tenth DIP switch would be used to switch between modes. Seems that he was already ahead of me on that one. Although he doesn't list it on his ebay shop, he has already written the firmware to do just what I suggested. Email him if you want some of these boards.

 

The ability to control a lot of pixels with just three channels means that you can use lots of pixels in props or set, for example, and not chew through universes of DMX. Of course if you need to control groups of pixels separately then you'll need several controllers, but they're cheap enough for this not to be too much of an issue.

[cedd]

My plan for controlling my units (when they get here from China) was to have a tiny project box on each end of each string (mine are strings of lights with wires between the LED's). The box would contain a buck converter at one end, so each strip could be fed its' own higher voltage DC supply (or have a local supply each). It'd also contain a line driver transceiver at each end. Then I could link my strings via DMX cable knowing that the links could be longer because the data is balanced. The line driver circuit is simplicity itself.

 

Part of me wondered about RJ45 link cables. If your DC supply to the buck converter is at 24V then current-wise you'd be able to drive a string over cat5 by putting your DC and ground up pairs (so using 2 wires each) with a pair for data and a pair spare. It's a handy and readily available cable type.

[KevinE]

I'm actually thinking of building a data line buffer/driver off the end of the control board so I can drive many short strings of parallel tape all starting with the same address..a sort of active DMX splitter for tape. This will allow the client to run multiple tapes in parallel around his venue without risk of data corruption. <_<