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What is the purpose of this cable? http://www.aliexpress.com/store/product/3-co

Discussion in 'Computers, Cabling & Other Miscellaneous Hardware' started by Greg.Ca, Nov 1, 2015.

  1. Greg.Ca

    Greg.Ca Apprentice Elf

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    To make things work better, I want to start using '4 core' cables instead of '3 core' cables when hooking up my three wire 5 volt WS2812b' pixels. If I utilize an additional ground wire in every cable, I should get less voltage drop and therefore obtain better data integrity when hooking up my 5V WS2812b's.

    As it stands now, I have been using '3 core' cables from Ray when hooking up my 5V WS2812b's. So far, everything is working well however, in the past year or two, almost every controller manufacturer now offers multiple universes per output and I am starting to take full advantage of that. In my latest designs, I now use 336 pixels out of 340 pixels per output. I feed voltage at both ends with three core cables but it just seems that because Ray has 18-19 thin gauge wire in his cables that I could easily attach the grounds to TWO wires in each 4 core cable instead of having a single ground wire in a 3 core cable. Everybody with me so far?

    I would be changing from 3 core cables to 4 core cables. On both the 3 core and four core cables, it indicates that the gauge is 75mm squared. Those wire are the same diameter in both the 3 core and the 4 core cable. I would now be hooking up 2 wires to the ground thus essentially 'doubling' the gauge of the ground wire. To us American's, it appears that this metric wire size is equivalent to about American 18-19 gauge. Way to thin for higher current draws for 2 universes of pixels per output as almost all controllers have now.

    Ray sells a 3 to 4 wire tee. Go to the subject line and click on the link. It will take you to a page where you will see the wiring diagram halfway down the page. What would be the possible purpose of having a data in and data out on the same connector? What am I missing here? I don't know what this T is designed for. Anybody know?

    What I would want is a simple cable that has a female 3 core on one end that attaches to the beginning of the pixel string (which has a 3 core male) and a 4 core male on the other end that has the black and green tied together. Does Ray make that? This would quickly give me two grounds on a 4 core cable from the pixels back to my Pixlite 16 controllers. Still with me?

    Anybody see any problem or issue with going from a simple time proven design that is working ok to changing the way I now want to hook up my pixels? If Ray had thicker conductors in his cables, none of this would be necessary. The conductors seem way to thin to carry the higher current required by the higher number of pixels/output. Since the 5 volt WS2812b's require only three wires, it should be easy to convert from a 3 core cable to a 4 core cable and have an extra ground wire.

    See below. This ALMOST works but the info indicates that the green and black are not wired together on the male end. If it was, then my problem would be solved. I don't know what or how this cable is used or designed for. Not a clue?

    I need something very similar to this. The ground wire on the 3 core female end would need to be connected to two pins on the 4 core male end.

    http://www.aliexpress.com/store/product/15mm-series-4-core-male-to-3-core-female-adaptor-compatible-with-Sandevices-s-controller/701799_1075599516.html

    Anybody using 4 core cables to attach to their 3 wire pixels? Thoughts? --Greg--
     
  2. MikeKrebs

    MikeKrebs New Elf

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    The 3 to 4 to 3 tee is used for something like ws2811 flood. The data goes in and comes out so you can continue to the next flood.

    As to the rest of your questions...I do not know but I am sure someone will understand the math. The wiring in the pixels is probably not much bigger than the tails and extensions so not sure having those extra ground would help. Since you are using the return to do power only, could not you just use 3 core wired ground, ground, plus?
     
  3. kane

    kane Dedicated Elf

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    The subject cropped the URL, but as Mike mentioned, those T's are most likely for things like floods, or perhaps icicles which have both a data in and out. I remember seeing some led strip that had an additional trace for the "return" data going the length of the PCB for this purpose.

    In terms of doubling up the ground wire to reduce voltage drop, I'm pretty sure that this wouldn't help you, as you're always bound by your weakest point (in this case it would be the +5v) It's like having a two lane highway that merges into one lane halfway - you're only going to get one lanes worth of traffic through.

    Kane
     
  4. i13

    i13 Senior Elf

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    Kane I disagree with your second paragraph. The voltage drop is due to the total resistance in the wires running both directions. Doubling both of them halves the resistance and therefore roughly halves the voltage drop between the supply and lights. Doubling one of them halves half of the total resistance (hard to say clearly) which reduces the voltage drop to 3/4 of what it would be if you hadn't doubled anything. In reality the negative has sightly more current than the positive because of the data circuit returning through it so it is slightly better to double the negative than the positive if you can't double both.

    Anyway I don't want to get too off-topic; the connector linked to within the post is a different URL to the one chopped off in the title. It might be worth asking Ray for a wiring diagram.
     
  5. kane

    kane Dedicated Elf

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    Cool - you're obviously better versed than me on this - I just seem to remember someone mentioning this a while back, so that's what I was basing my info on.

    That's one of the things I love about this forum - some very switched on people (no pun intended).. And hacks like myself who do our best!!

    Cheers

    Kane
     

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