Sending data to pixels over 8 bundled (data) wires

corfoto4

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Hello,

In my display, I am having issues regarding interference between the data wires for my display. Currently, I have 8 wires bundled together which run from my power box to my Mega Tree to control the strings. Inside the power box, I have shielded the data wires to protect the data which runs from my ESP controllers to an RJ45 socket. The idea is that I can run a UTP/STP cable from the power box to the tree where it would then split off from another RJ45 socket mounted to the frame of the tree.

In theory, the idea worked well. However, in practice, I am getting a tonne of interference between each data cable in the ethernet cable. After researching, it seems as though you cannot buy ethernet cables where each individual cable is shielded (there can only be shielded in pairs such as Cat7). I thought there may be a different way to transfer the data through a different medium such as optical. Obviously not fibre optic because it is expensive and not necessary in the slightest. But possibly using Toslink cables but even then this seems unnecessary.

Does anyone know of a cheap and easy way to create a bundle of shielded wires that can be easily connected and disconnected to sockets on the tree and in the power box?
A better solution would include 9 wires as I currently have a single wire running beside the UTP/STP cable going to the same location.

Maybe there is a way to convert 'combine' the data wires together on a PCB and transmit properly using the Ethernet protocol to be received and decoded at the other end? Like a serial bridge?

Thank you!
 
Last edited:

merryoncherry

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This kind of cable has twisted pairs, so you should run up to 4 data signals over it. This is called a "differential receiver" and you can get them for many major controllers. You'll just need 2 cables instead of 1, but it's a lot better than 8. Just wrap them together.

Maybe there is a way to convert 'combine' the data wires together on a PCB and transmit properly using the Ethernet protocol to be received and decoded at the other end?
"Sending data properly" using Ethernet is called "E1.31" or "DDP", and the thing that receives it on the other end is called a "controller" 😉. The thing that sends it properly to those is called "xLights", "xSchedule", "FPP", or maybe "Vixen" or something like that. Use a network switch so that data gets sent just down the way you want.

I hesitate to mention this, but I have one hare-brained idea for you. There is at least one vendor who does sell a differential encoder, but you'd need a few to do what you're describing:
 

merryoncherry

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I currently have a single wire running beside the UTP/STP cable going to the same location.
What's the single wire? Common ground? What is the distance you're trying to run?
 

Grozzy

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Is your ESP a diy or is it a espartstick, espixelstick, diguno. If it is diy, are you using a logic shifter/buffer (74LS125) or an famp between the esp and the first pixel. What is the distance between the esp and first pixel.
 

corfoto4

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What's the single wire? Common ground? What is the distance you're trying to run?
The distance could be around 5-10m. Based on my current setup, I am using a cat6 cable to transfer the data in two separate twisted pairs which has improvements but is still not perfect.
 

corfoto4

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Is your ESP a diy or is it a espartstick, espixelstick, diguno. If it is diy, are you using a logic shifter/buffer (74LS125) or an famp between the esp and the first pixel. What is the distance between the esp and first pixel.
From esp, I am running a cable all the way to the first pixel. To add, I am using cheap retic wire as my data cable but I have shielded and grounded those. The Ethernet cable seems to be the problem. I am about to test and see if a cat6A cable will work better.

Does anyone know the data rate for a 400 sting of pixels?
 

merryoncherry

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Oh, only 5-10m? That should be no problem. I suspect your issue is more likely lack of a common ground. If you can use a common ground, don't use twisted pair, use something like these.
20220713_205440.jpg
20220713_205249.jpg
If you don't have a common ground, that's exactly what differential pairs solve... they send signals between isolated areas.
 

David_AVD

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You really want to send pixel data as a RS485 balanced data pair. You'll need to convert from single ended to RS485 at the controller, send over paired cable, then convert back to single ended at the prop. I've done this with some custom boards and it works fine.

There should be a commercial solution out there. Maybe @AAH has something?
 

corfoto4

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I have added 2 videos that show the data setup and what I am experiencing. The ethernet cable I tested is a cat 7 which has been grounded to my power supplies (which are connected to AC ground). The cables wrapped in the aluminium tape are also grounded in the same connection.

 

corfoto4

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You really want to send pixel data as a RS485 balanced data pair. You'll need to convert from single ended to RS485 at the controller, send over paired cable, then convert back to single ended at the prop. I've done this with some custom boards and it works fine.

There should be a commercial solution out there. Maybe @AAH has something?
That's sort of what I was thinking of. But that would mean I need 9 twisted pairs, 3 ethernet cables, or 2 serial cables?

Maybe like this?
 
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Grozzy

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From esp, I am running a cable all the way to the first pixel. To add, I am using cheap retic wire as my data cable but I have shielded and grounded those. The Ethernet cable seems to be the problem. I am about to test and see if a cat6A cable will work better.

Does anyone know the data rate for a 400 sting of pixels?
Reread my question. If you are going directly from an esp chip 3.3v to a pixel you will have problems with a distance greater than about 50cm no matter what cable you use. You need to use a buffer chip or famp to bring the data voltage up to 5V
 

KiwiPhil

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proberbly not your issue but doesnt SFTP / FTP need to be grounded at each end for the shielding to work correctly?

I have similar flickering issues when the negative from the pixel string does not have sufficient enough current path back to the signal source
 

Skymaster

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