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Thread: Pixel Cable Lengths - From Controller or Between Pixels - Details on Post 1

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    Havin fun ! kidcole's Avatar
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    Default Pixel Cable Lengths - From Controller or Between Pixels - Details on Post 1

    I don't think we have a decent reference here on CC for cable lengths. Or if we do, would someone post a link for me ...

    Some of us have been helping Scott @scottmcl to plan his new pixel effects, controllers and Pi player(s). And every time I think about a new design, I am concerned about how much distance I can get from controller to pixels. My longest pixel cable is about 18 feet on a E681 (same electrically as an E682) and I have no problems. I have also seen discussion that some people run cables up to 25 or 30 feet. But how far can I push it before I need to update the bridge resistors on the E68x controllers? What we need here is a reference table that shows the cable distance vs. the resistor values used. @Samj435 says he is going over 100' with his E682 outputs. Do any of you know where we can find a quick table of the bridge resistor values compared with distance ?

    Once we've done this for Sandevices, perhaps we could also do it for other controllers such as the J1Sys and Falcon. I know that Falcon offers a daughter board with uAmp(s) that can drive up to 75 or 80 feet. Micro amps (uAmps) clean up the digital signal rather than boosting it (like the bridge resistors). So it's a better way to go. I notice that one FalconChristmas.com they offer individual uAmps in group buys. These can be are inexpensive and can be individually wired to the output of any controller (data, power and ground) to clean up the signals. But frankly I'd like to see all of the controller builders include uAmps in their designs.

    Lastly, each pixel creates the drive to the next one. So when we take the signal from the end of a pixel string and plug it to another string, how long of a cable can be use before the signal fails ?

    I am currently buried between some molding work here at the house, and a huge mailing database that I am trying to create for my antique Outboard club (I became president of the Carolinas Chapter in January). As we create posts and find the details for this topic, I will be happy to accumulate them here on the first post. So I'll change this text over time, until we get a good reference. Now I can see why DoItYourselfChristmas.com uses a wiki. It's not easy on this type of Forum to have a reference section .. Happy hunting !
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Back to Work <unretired> so I went Static in 2017. Planning xLights when I retire <again>. Maybe 2019 ?

    Falcon - 3 F16V3 & 1 PiCap, Sandevices - 2 E681 & 4 E6804, 288 Channels Lynx Express, 108 Channels DC DMX,
    10' Pixel MegaTree, CoroFlakes w/Pixel Modules, Pixel RBLs, 2 Pixel Matrix 16x25, 10" RGB Ornaments, 7x230 Pixel Icicle Matrix,
    Classic 20' AC Megatree, TIR Destiny RGB Spots, RGB Blowmolds, Wireframes, and Inflatables with External Light Control

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    Havin fun ! kidcole's Avatar
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    Default Re: Pixel Cable Lengths - From Controller or Between Pixels - Details on Post 1

    I found this from Jim StJohn (owner/designer for Sandevices). Sadly it is not definitive. He says "test" various resistor values and gives the range. I hope we can find more ..

    **************************************************
    If you are encountering issues such as pixel flickering when trying to drive pixels over a long cable run (say more than 15-20 feet) with the E682, this can sometimes be cured by replacing the pluggable resistor network that drives that output with a different value.

    There are 8 pluggable networks on the E682, each drives the 2 output connectors immediately beneath it. The default value is 270 ohms, indicated by a part number containing "271" 27 followed by 1 zero = 270.

    A smaller value can often help when driving long pixel leads. There are a couple of ways to test this without having to have different resistor networks available.

    You can use individual 1/4W or 1/8W resistors (say from Radio Shack), or you can use small wire jumpers (effectively 0 ohm resistors).

    Remove the resistor pack above the output to be tested. This will leave 8 empty socket holes, 1 thru 8 from left to right. Form the resistor or jumper leads into a "U" shape with the legs equal lengths (about 1/2") and about 1/10" apart.

    For 3 wire pixels such as 2811/2812, only one resistor or jumper is needed per output. For the upper jack of the pair, insert the resistor or jumper between contacts 5 and 6, for the lower jack use pins 7 and 8. Power up and test the output.

    If you are using resistors, I would try starting at 33 ohms and working up. Go one standard value less than the highest value that works reliably. For example, if 56 ohms works, but 68 ohms appears flaky, go with 47 ohms.

    If you are doing the test with jumpers, if the output works properly with the jumper in place, then I would suggest purchasing the Radio Shack resistors to identify the best value.

    The resistor networks can be purchased from any electronic supplier. They are "83" series, 8-pin networks containing 4 individual resistors. A typical part number would be: 83S560. The resistance is shown by the 3 digits after the S. 2 significant digits and the 3rd digit represents the number of 0s. So 83S560 is a 56 ohm resistor, "56" followed by no zeroes.
    83S101 would be 100 ohms "10" followed by 1 0 = 100.
    **************************************************

    Here's a user reply to Jim:

    **************************************************
    I have replace all of my resistor packs with 33 ohms. On short or long runs that solved my flickering problems. I have 5 682's.
    **************************************************

    Here's a user reply that sounds a little more conservative: I guess if you have these bank resistors in stock and you have a problem, these are a simple plug-in to change them. Just keep all your spare stock labeled !

    **************************************************
    I ordered 47, 68, and 100 ohm RNs on Mouser. They didn't have 33's in stock of the brand I was buying so figured I'd see if these work. Glad to know someone else has used the lower values on shorter runs as well. Here's hoping it solves me issues!
    **************************************************
    Thanks,

    Denny Cole
    https://www.facebook.com/groups/Cole...ristmasLights/

    Back to Work <unretired> so I went Static in 2017. Planning xLights when I retire <again>. Maybe 2019 ?

    Falcon - 3 F16V3 & 1 PiCap, Sandevices - 2 E681 & 4 E6804, 288 Channels Lynx Express, 108 Channels DC DMX,
    10' Pixel MegaTree, CoroFlakes w/Pixel Modules, Pixel RBLs, 2 Pixel Matrix 16x25, 10" RGB Ornaments, 7x230 Pixel Icicle Matrix,
    Classic 20' AC Megatree, TIR Destiny RGB Spots, RGB Blowmolds, Wireframes, and Inflatables with External Light Control

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