Pixel String Differences

Discussion in 'RGB Lights - Intelligent Pixels and 3-Channel RGB' started by bdt, May 10, 2015.

  1. bdt

    bdt Apprentice Elf

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    Can someone explain the differences between the below pixel strings, and recommend which one is best? I plan using one of them for my 360 degree pixel Megatree.


    I believe strings 1 & 2 use the same protocol as the popular strip (http://www.aliexpress.com/store/product/5m-led-digital-strip-DC12V-input-WS2811IC-256-scale-10pcs-IC-and-30pcs-5050-SMD-RGB/701799_568458133.html) and the only difference is voltage. Is it worth paying $3.00 more per string for 12v, or am I missing something?


    Is string 3 a different chip and protocol? Are there any advantages/disadvantages with this string?


    Thanks in advance.


    1- http://www.aliexpress.com/store/product/Promoion-DC5V-50nodes-WS2811-pixel-light-12mm-diameter-IP68-rated-256gray-scale-all-black-wire-epoxy/701799_1549446292.html


    2- http://www.aliexpress.com/store/product/DC12V-WS2811-pixel-node-50pcs-a-string-IP68-rated-epoxy-resin-filled-with-all-black-wire/701799_867072780.html


    3- http://www.aliexpress.com/store/product/BLACK-wire-50pcs-DC5V-UCS1903-full-color-addressable-pixel-node-RGB-12mm-diameter-IP68-rated-all/701799_32272758555.html
     
  2. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    You are correct string 1 and 2 are the same (2811/2812) except for the voltage. The advantage to 12v is that you can connect a longer string which means less power injection (in most cases but not in all)

    See the thread for the differences between 12v and 5v strings
    http://auschristmaslighting.com/forums/index.php?topic=2595.0

    The 3rd string uses the USC1903 chip instead of the 2811 so this is different
     
  3. OP
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    bdt

    bdt Apprentice Elf

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    Fasteddy, read your voltage thread, very helpful thanks.
     
  4. mborg10

    mborg10 Michael Borg

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    Personal preference for me is 12v. Less issues with power injection which means less cables less to do and a neater display. 5v has its advantages as well but it's 12v for me.
     
  5. nzlongfellow

    nzlongfellow Dennis from NZ

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    I agree on 12V but I have a lot of 5V and use 12V - 5V Buck converters.
     
  6. OP
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    bdt

    bdt Apprentice Elf

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    Agree, however having no experience with string pixels I’m still teetering back and forth. I don’t understand why use buck converts vs. 5v power supplies? The savings from using 5v pixels would buy more than enough power supplies. Since this is a tree vs. a roof line it should be fairly easy to inject power.
    I plan on 48 strings with 60 pixels. From what I’ve read there should be power injection every 50 pixels. If I use the 5v strings do you think I will be ok with injecting power every 60 pixels or should I shorten my strings to 50 pixels? I believe I would be ok with 12v strings.
     
  7. fasteddy

    fasteddy I have C.L.A.P Global Moderator Generous Elf

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    If you back inject then you only need to inject every 100, for example if you have 3 strings then if using a cable large enough to supply 2 strings then you only need to inject between string 2 and 3, this way you back inject string 2 and forward inject string 3 thus reducing the amount of injection points

    If you want just a string of 60 then how far the power supply is from the lights and the gauge of the power cable will determine if you can get away with 60 without seeing the effects of pinking when white. So best to test.
     
  8. OP
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    bdt

    bdt Apprentice Elf

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    Makes sense, good news is my design to inject power at the top of every string and start a new universe at the bottom of every other string appears to be very conservative. Bad news is it also appears to be wasteful.
    thx!
     
  9. AussiePhil

    AussiePhil Dedicated Elf Administrator

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    Generally 60 is pushing the limits at 5V and will see pink when set all white, a couple things can and will impact this though.
    1. Total length of pixel string due to the spacing between strings, 100mm wire length between pixels will have more voltage drop than 80mm between pixels, might seem insignificant but 60x20mm = 1.2M or 4Feet and will make a difference.
    2. Total length of power cable from PSU to first pixel, the shorter the better.
    3. The gauge of the wire from the PSU to first pixel, the larger the better.

    All these things combine to cause or reduce voltage drop over the entire string.

    I wouldn't plan the actual injection points till you get and test the strings. It's entirely feasible that you could inject power 20 pixels up the string as an example.

    Cheers
     

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