Author Topic: Data distance  (Read 383 times)

Offline ebrown19721972

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Data distance
« on: December 16, 2018, 06:38:24 AM »
I am sure this has been discussed before but I am not finding the answer. Can anyone tell me approximately how far data can travel before any issues may be seen? Next year I plan to do more power injection and hope to have some runs of 100 feet of pixels. I have considered purchasing some F amps and figure I will need something to boost the data signal. I run almost everything at 50%.


Thanks in advance,
Eric

Offline tbone321

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Re: Data distance
« Reply #1 on: December 18, 2018, 10:21:47 PM »
This is not something that can really be answered because there are a whole lot of variables.  Are you talking about the distance between the controller and first node, the distance between nodes, or the length of the string itself?  The distance between the controller and the first node depends on the controller being used and in some cases the wire type as well.  Some controllers can go 20 or more feet but require CAT 5 cable to work at all while other can go better than 100 feet on standard 3 wire cable.  The distance between the nodes is a bit more consistent but can still vary from 2 to 6 or more feet depending on the node type and electrical noise near them.  The length of the string is more of an issue with power injection than data loss as the nodes regenerate the signal minus the data it used on their outputs.  The only issue there is the total number of nodes in the string because there is a limit on the amount of data that can be sent per frame.

Offline Bwinter

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Re: Data distance
« Reply #2 on: December 18, 2018, 10:58:52 PM »
100ft?  Im sure its possible to get data to travel that far.

But I would consider other options, given that distanceand not try to send pixel-data that far.

Offline JonB256

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Re: Data distance
« Reply #3 on: December 19, 2018, 07:16:10 AM »
Definition time:

Pixel Data - the data format actually used by a string of pixels is called SPI. It is transmitted on a single wire and is a 5vdc square wave. That is important because a single wire is prone to data degradation (signal becomes unusable) over distance. Noise, capacitive losses, poor waveform to begin with.

There are two prominent solutions to SPI data degradation.

1.  Use data amplifiers - (like the F-Amp) These will take a good SPI waveform and make it better/cleaner, therefore letting it travel farther on that single wire to "first pixel."  You could theoretically use multiple F-amps and go very long distances, but at $5 each, it adds up.

You will also see people use CAT5 cable instead of basic 3-wire cable. Because of the twisted pairs of wire in CAT5, the SPI signal is semi-protected from some data loss, but CAT5 wires are small gauge and can be pain to strip and connect.

2.  Convert the SPI to a "long distance" protocol, then at the other end, un-convert it. :)
This is the method used by Falcon (and others) called Differential (Transmit and Receive). There are industrial grade protocols that are designed to carry data long distances without degrading. The Falcon Differentials use RS-485. The SPI data is converted to RS-485 and sent over standard CAT5 cables. Long distances of well over 100ft are easily achieved. At the end, the RS-485 is changed back to a clean SPI signal, ready for Pixels. The Falcon F48 is the epitome of this method.


 

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