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Thread: Some advice for a beginner…

  1. #1
    Join Date
    Mar 2019
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    Ohio
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    Question Some advice for a beginner…

    I’ve been researching, reading, and experimenting with some pixel lights (ws2811 and ws2812b) for a few months. My goal is to outline the entire perimeter of my roof on my ranch house. I plan to mount the lights in a diffuser channel so that they are essentially hidden when they are off. I have access to a 20amp/120volt circuit at the peak of both ends of the house and plan to have 2 runs of lights start at each for a total of 4 runs. Based on my house layout and the location of my power, my plan is as follows:

    Run 1 = 48’
    Run 2 = 48’
    Run 3 = 61’
    Run 4 = 69’

    For the purposes of my planning, let’s talk in terms of the 69’ run since that is the longest. Each run will have its own power supply and my intent is to use an arduino compatible board (Wemos D1 mini) as a controller on each run to receive e1.31 data via wifi in multicast from FPP to display. A few questions about this portion:
    • Is the D1 mini not advisable? I see most posts are talking about the various controllers like the falcon, etc. but that seems overkill to me if I’m essentially controlling one “string” of lights and the D1 mini cost me less than $3.
    • Would the D1 be able to control 1260 pixels (see calcs below) or am I asking for trouble here? I understand the longer the run, the more time it takes per frame, but will this be horribly slow?


    I would like to use 12v lights so that I can minimize my power injection. I am considering using the WS2815 five meter strips from Ray Wu and injecting power at the beginning and end of each strip. I would like to use 60 pixels per meter. Based on the specs I see on Ray’s site, I have computed the following:
    • 14.4 watts per meter / 60 px = 0.24 watts per px (14.4 is from Ray’s website)
    • 0.24w / 12v = 0.02 amps per px
    • 21 meters (69ft) x 60 px per meter = 1260 pixels
    • Totals:
    • 25.2 amps
    • 302.4 watts


    Now a few questions:
    • One thing that seems unclear to me is the following: Do power injection points require a “home-run” back to the power supply OR, can I run a single power injection line of X gauge, and simply splice in at each beginning/end?
    • What gauge of wire would be needed? (I’ve tried running the calculations online, but I’m also a bit confused by those)


    Now for the final questions:
    • Am I on the right track for accomplishing my goal?
    • I’m sure there are many different ways to do it, but if it were your house, given the constraint of the 120v power location, how would YOU do it?


    Thanks to any/all that can help

  2. #2
    Join Date
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    Default Re: Some advice for a beginner…

    You are on the right track. A run of 1200 pixels will limit you to a refresh rate of 50ms or longer. This means you cannot get true motion from those pixels. Not a problem for the roof and other "strings", a bit of an issue when using a matrix or other graphic capable prop. I do not know of a way to do multiple refresh rates in a show. Meaning that if you add a matrix in the future and up the refresh rate, those string with lots of pixels may need to be rewired.


    I use that WeMos device along with a pixel driver to control strings of pixels. You will need that driver right at the output of the WeMos because the WeMos output pins are not that strong.


    2019 - Going to visit my Daughter in New Zealand (again). I will be dark for the 2nd year in a row. Sigh..

  3. #3
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    Default Re: Some advice for a beginner…

    Thanx for the confirmation on the approach. Which pixel driver do you use? I've got a 74AHCT125 on hand, but haven't experimented with it yet.

  4. #4
    Join Date
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    Default Re: Some advice for a beginner…

    I actually use the "Null pixel without a pixel" driver that was available in the group buy. I suspect just about any device with a good darlington transistor will do.


    2019 - Going to visit my Daughter in New Zealand (again). I will be dark for the 2nd year in a row. Sigh..

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