Author Topic: Wiring two outputs on a single CAT 5 / 6 cable  (Read 2286 times)

Offline gadgetsmith

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Wiring two outputs on a single CAT 5 / 6 cable
« on: August 06, 2015, 08:56:16 AM »
I read a question from PatDelaney in another thread ( http://falconchristmas.com/forum/index.php/topic,667.msg29143.html#msg29143 ) about wiring two outputs on one CAT cable, I decided just to share what I do in case anyone were interested.

In my application (pictured) I was controlling a single string of 50, 5v pixels on each of the two outputs.  I use 12v to distribute power, and 5v to drop it down at the beginning of the string. I've also tested this with 12V pixels, but only strands of 50, so beyond that length, YMMV.  I also use stranded, pure copper, CAT 6 cable.

On the controller end.

Output 1 -
GND - o/w + g/w (also jumper this ground to output 2 ground using a spare pair of jumper wire, color doesn't matter but use o/w + g/w if you want to make it less confusing)
DATA - o
PWR - br + br/w

Output 2 -
GND - jumpered to Output 1 GND
DATA - g
PWR - bl + bl/w

On the light string ends:
Just match the colors up.  Be sure to tie both o/w + g/w GND wires to GND on both strings being controlled.

HTH someone.


Offline Steve Gase

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Re: Wiring two outputs on a single CAT 5 / 6 cable
« Reply #1 on: August 06, 2015, 09:40:51 AM »
Just thinking here...

In situations where you will be doing power-injection at the nodes anyway...  if you used cat5 from controller to a bunch of strings you could use one wire for ground, and the other 7 for data from 7 separate controller ports.
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Offline CaptainMurdoch

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Re: Wiring two outputs on a single CAT 5 / 6 cable
« Reply #2 on: August 06, 2015, 09:45:32 AM »
In situations where you will be doing power-injection at the nodes anyway...  if you used cat5 from controller to a bunch of strings you could use one wire for ground, and the other 7 for data from 7 separate controller ports.

Could work.  If I were doing this, I might choose to go a slightly safer route and have data/ground pairs that were twisted rather than having two separate data lines twisted together.  This limits to 4 data lines, but should eliminate any potential for crosstalk between data lines.
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Offline gadgetsmith

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Re: Wiring two outputs on a single CAT 5 / 6 cable
« Reply #3 on: August 06, 2015, 11:34:41 AM »
If doing power injection at the nodes, then this type of wiring isn't needed.  I've not done any testing without a data/ground twisted pair, but seeing Dave's recent success doing this at 60+ ft makes me want to go and test some more!  :)

Offline AussiePhil

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Re: Wiring two outputs on a single CAT 5 / 6 cable
« Reply #4 on: August 07, 2015, 04:30:38 AM »
In situations where you will be doing power-injection at the nodes anyway...  if you used cat5 from controller to a bunch of strings you could use one wire for ground, and the other 7 for data from 7 separate controller ports.

Could work.  If I were doing this, I might choose to go a slightly safer route and have data/ground pairs that were twisted rather than having two separate data lines twisted together.  This limits to 4 data lines, but should eliminate any potential for crosstalk between data lines.

For single wire protocols like 2811 this is actually a bad idea as the signal line should be unbalanced and treated like coax, certainly not twisted around an earth. The twist in network cable is specifically designed for balanced signals.

The fact that we seem to be able to send the data over the proverbial piece of wet string speaks more about the receive side of the pixel.

Crosstalk reduction for unbalanced lines can only be dealt with be using single wire shielded cables.
 

Offline CaptainMurdoch

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Re: Wiring two outputs on a single CAT 5 / 6 cable
« Reply #5 on: August 07, 2015, 09:31:48 AM »
For single wire protocols like 2811 this is actually a bad idea as the signal line should be unbalanced and treated like coax, certainly not twisted around an earth. The twist in network cable is specifically designed for balanced signals.

The fact that we seem to be able to send the data over the proverbial piece of wet string speaks more about the receive side of the pixel.

Crosstalk reduction for unbalanced lines can only be dealt with be using single wire shielded cables.

Yeah, I'm not saying it's perfect and my comment about being better has nothing to do with the twist itself but the isolation of using a twisted pair for data and ground keeps two data from running together (in the same twisted pair) for the length of the cable.  The best solution would be to use the cable used for CCTV systems which has a coax cable for the video and a separate set of lines in the same cable for power.  That gets expensive though.

I would disagree a little on the crosstalk reduction requiring shielded cable comment though.  I believe crosstalk elimination is part of the reason that the newest PATA cables in computers had data and ground interleaved while the original cables didn't.  Granted the frequencies and amount of data we are dealing with are a lot lower, but physical separation or partial sheilding is better than no shielding.  Hence the reason for my comment about not running two data in the same twisted pair.

 

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