Pixels in parallel yet still addressable

Notenoughlights · Sep 25, 2021

Bunnings have this interesting tree this year, and yes it uses pixels. I am trying to figure out how it works.
The image below shows the center topper, inside that topper is a round PCB with no components attached. It has a common + - and Data track that every single string attach to, there is no Data in -> Data out. Each of the strings only contains 3 wires.

Each pixel has been numbered in the image, pixel 1, pixel 2, pixel 3. The first pixel in every single string appears to be able to operate independently from that of every other pixel yet they get the same data feed.
I believe these run the ws281x protocol as I have attached pixels to the end of these strings and they operate without issue.

This is all I have been able to find at the moment.

View: https://www.youtube.com/watch?v=Mt_jUdF3mBw

View: https://i.imgur.com/gFEKaeR.jpg

View: https://i.imgur.com/AtnEN9J.png

JohnsRdChristmas · Sep 25, 2021

Interesting, wonder if there is more to that pcb then meets the eye,
The bottom of each string definently arnt connected??

My theory would be, if they are connected then,
(thinking the data may run down and back up, and that pcb traces it to the next string, so that the data is all in series) but the ring also power balances as the ground and positive are all tied into the common rings,
If each of the strings are not connected at the end then not sure what trickery is going on,

Also do you know what voltage it runs at?

Notenoughlights · Sep 25, 2021

Cathelest said:
Interesting, wonder if there is more to that pcb then meets the eye,
The bottom of each string definently arnt connected??

My theory would be, if they are connected then,
(thinking the data may run down and back up, and that pcb traces it to the next string, so that the data is all in series) but the ring also power balances as the ground and positive are all tied into the common rings,
If each of the strings are not connected at the end then not sure what trickery is going on,

Also do you know what voltage it runs at?

I toned out the PCB with a multimeter and looked at the track physically. They're all connected as if it was just a bunch of wires twisted in the top for each line

This runs at 5V, tree comes with a USB plug

No data returns to the top, the strings are cut at the bottom.

JohnsRdChristmas · Sep 25, 2021

The controller wire 4 wires?

Notenoughlights · Sep 25, 2021

4 wires, + - D L - The L wire comes from a transistor and goes to the star plug, it's not connected to anything else. It's so when you push the remotes power button, the star also turns off as it's just DC fed.

JohnsRdChristmas · Sep 25, 2021

Ah, yeah interesting,
I know theyre sold as indore use, how ya think it would go outdoors?
If were cutting off the controller, the rest of the strings might be ok?

Notenoughlights · Sep 25, 2021

Cathelest said:
Ah, yeah interesting,
I know theyre sold as indore use, how ya think it would go outdoors?
If were cutting off the controller, the rest of the strings might be ok?

I'm yet to test removal of the existing controller, I might give it a go tonight to see how it plays out, it might even lead to more discoveries that these might not infact be 281x pixels, but I'm doubtful on that part as when I connected some 2811 pixels to the end of one of the strings, they worked fine.

Mark_M · Sep 25, 2021

3 wire pixels wired in parallel... hmm.

My realistic idea is that one string has power applied and data sent to it at a time. Then all these strings are strobing so fast we cannot see it turning off.
But I don't think you've found each string to be on a different power output?

Notenoughlights · Sep 25, 2021

Mark_M said:
3 wire pixels wired in parallel... hmm.

My realistic idea is that one string has power applied and data sent to it at a time. Then all these strings are strobing so fast we cannot see it turning off.
But I don't think you've found each string to be on a different power output?

There's nothing on the PCB in the topper, just tracks that link all + - D together like a multiboard
I'll try the camera on slow motion and see if I can see anything weird - And this showed nothing out of the ordinary

AAH · Sep 25, 2021

Without seeing the tree in person and doing some experimentation my guesses are
1) it could be that the first pixel in each string has a chip in it that runs a sequence and that sequence is replicated with a time shift to each of the other strings. I think this is unlikely as you would undoubtably get a drift over time. This method would only need power going to the first pixel in each string.
2) it would be fairly easy to have a simple chip at the first pixel in the string that strips off the first "n" channels. This would be 0 for the 1st string, 12 for 2nd string etc. On a simple scale this is kinda what is done with the Falcon smart receivers. The WS281x protocol is so simple that a simple counter can remove the channels.

If you wanted to experiment then tapping some pixels in before and after the first pixels in the strings will show what funny business is going on.

Notenoughlights · Sep 25, 2021

I have hooked in a couple of strings of 5v 2811 pixels. Both strings of pixels mirror each other perfectly, so something is being done on a string level with this light setup.

I have further investigated by disconnecting the data from the supplied controller and feeding in a signal from a pixel stick running WLED.
They do work on the ws281x setting however they flicker and don't really respond all that well colour wise. I have found that using the 400khz option in the protocol selection list lets them run correctly without flickering, colours are correct etc.

View: https://i.imgur.com/mjCQm3o.png

It appears that each pixel in each string strips the last 13 pixels worth of data out before doing its bit, this is repeated for every pixel. The first in line does not do this. This then causes the setup to act as one long string of end to end connected pixels

In order to run this tree in a light show you will require a controller that can run 400kHZ output (Pixel stick/esp8266...) and set your connected leds to 195. Set this as 15 strings of 13 nodes in your sequencer and I believe this would work without issue.

i13 · Sep 25, 2021

Judging by the photograph, these pixels look like the 3-wire pixels that are discussed part-way through this thread: https://auschristmaslighting.com/threads/13341/

AAH · Sep 25, 2021

Notenoughlights said:
I have hooked in a couple of strings of 5v 2811 pixels. Both strings of pixels mirror each other perfectly, so something is being done on a string level with this light setup.

I have further investigated by disconnecting the data from the supplied controller and feeding in a signal from a pixel stick running WLED.
They do work on the ws281x setting however they flicker and don't really respond all that well colour wise. I have found that using the 400khz option in the protocol selection list lets them run correctly without flickering, colours are correct etc.

View: https://i.imgur.com/mjCQm3o.png

It appears that each pixel in each string strips the last 13 pixels worth of data out before doing its bit, this is repeated for every pixel. The first in line does not do this. This then causes the setup to act as one long string of end to end connected pixels

In order to run this tree in a light show you will require a controller that can run 400kHZ output (Pixel stick/esp8266...) and set your connected leds to 195. Set this as 15 strings of 13 nodes in your sequencer and I believe this would work without issue.

Did you connect the pixels to the end of the string or somewhere else?
I suspect that almost all of the pixels are just the slow version of WS2811 which would allow the processor built into the first pixel to process stuff easier.

Notenoughlights · Sep 26, 2021

AAH said:
Did you connect the pixels to the end of the string or somewhere else?
I suspect that almost all of the pixels are just the slow version of WS2811 which would allow the processor built into the first pixel to process stuff easier.

I tried adding pixels after the existing strings as well as soldering directly to the data pins on the PCB. The pixels after (Was very difficult to tell) looked as if they were doing what the first pixels in line were doing as in repeating the same effects, the pixels I joined in at the very start mirrored each other.

Being 400kHz sounds about right, standard ws2811 we use daily are 800kHz if I am correct?

Grozzy · Sep 26, 2021

Notenoughlights said:
I tried adding pixels after the existing strings as well as soldering directly to the data pins on the PCB. The pixels after (Was very difficult to tell) looked as if they were doing what the first pixels in line were doing as in repeating the same effects, the pixels I joined in at the very start mirrored each other.

Being 400kHz sounds about right, standard ws2811 we use daily are 800kHz if I am correct?

The ws2811 chip can do both speeds (taking pin7 high puts it in slow mode)

The motivation always seems to be a cost saving exercise (remember the old 3 wire to to 2 wire lights) so whatever they have done would have to be cheaper than just running a return data wire or running them in a zigzag pattern.

Extra circuitry on the first pixels should be visible.
Can you take a close up photo of the first pixel on either the second or third string.

I don't believe the ws2811 is reprogrammable outside the factory and imagine how messy it would be from a QC point of view ensuring you solder a different 1st pixel for each string to shift or ignore the data of the the preceding string(s)

Pixels in parallel yet still addressable

Notenoughlights

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JohnsRdChristmas

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