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Thread: Power injection clarification

  1. #1
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    Smile Power injection clarification

    First time with 5v pixels and power injection. Planning on doing a mega tree with 16 legs of 35 pixels each. Ws2811. I have 16 inputs but need to save some for other parts of the display, so I was thinking of running strands of 70 for each 2 legs, starting at the bottom, then reversing to finish at the bottom of the second leg. I've heard the rule of thumb to power Inject after 50. In this case, I wondered if I could get away without injection at 75? The power supply would be less than 1 ft away from the start of the pixels. E682. If I really had no choice but to power inject, would I have to do it after 50? At the halfway point? Or at the end of 70? This setup is far from set in stone, so I'm open to any suggestions. I picked the 70 figure per strand without reasoning other than trying to not push the limit on each output, so I'd be fine to join more strands if it made sense. These are 12mm bullets @ 5v

  2. #2
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    Default Re: Power injection clarification

    Hi, if it was me I would power at the start (pixel 1 - normal connection) and the end (pixel 70) that way no pixel is more than 35 from power.

    Pixel 1 and pixel 70 can both connect to the same power and ground cables from the E682 no need to run 2 sets of cables.

  3. #3
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    Default Re: Power injection clarification

    I might choose to cheat a bit on this one based on feedback from others on this forum. I'd just inject at the start BUT I'd also reduce my intensity at the controller to 80% or less. You'd be surprised how little difference there is between even 50% and 100% especially when viewing the pixels at night. You might just start at 100% and see if you get any of the last pixels turning pink. If so, reduce power and you should be good without additional injection. I have some lengths of 75 pixels that do just fine with only one power source. Also note that usually the problem with power is not the distance from the source but the voltage drop through the wiring in the pixel string. Some pixels come with only 20 gauge wire which will definitely cause issues for longer strings. I always make sure to get 18 gauge wired strings from reputable sources to minimize the voltage drop in the string.
    Ed
    Happily retired

  4. #4
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    Default Re: Power injection clarification

    Power inject at the first pixel on each leg and you are good to go. No need to reduce intensity or run wires up your legs to get to the top.


    2018 - Moving and going to visit my Daughter in New Zealand. Most likely I will be dark or nearly dark, Some static stuff that is simple to put up.

  5. #5
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    Default Re: Power injection clarification

    Quote Originally Posted by MartinMueller2003 View Post
    Power inject at the first pixel on each leg and you are good to go. No need to reduce intensity or run wires up your legs to get to the top.
    Sorry, just to clarify, I was going to do 1 strand of 70 pixels, then spread that over 2 tree legs. Up one, down the other. Do you mean just power the start of the strand? Or power the start of each of 16 individual legs?

  6. #6
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    Default Re: Power injection clarification

    Why do so many DIYers buy a 16 port controller to avoid injection?

    Hey Developers.....what we need is a distribution board with data jumper terminals. See Picture below...like this Falcon F8-Distro, except with the data jumper terminals.

    NewDistBoard copy.jpg
    In Lights Therapy

  7. #7
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    Default Re: Power injection clarification

    Quote Originally Posted by XmasinVancouver View Post
    Sorry, just to clarify, I was going to do 1 strand of 70 pixels, then spread that over 2 tree legs. Up one, down the other. Do you mean just power the start of the strand? Or power the start of each of 16 individual legs?
    You said you wanted to preserve a few ports. Two groups of 8 legs per port = 285 pixels per port. This allows you to go at 40 frames per second (25ms) refresh rate. Zig-Zag just like you planned. Inject power at the base of EVERY leg (16 injection points). Run data and ground between the legs at the top or bottom (as appropriate for zig or zag). You have 35 pixels per injection point. This means you can run at full brightness without any issues.

    FYI: At 35 pixels per leg and 16 legs, you are only using 560 pixels. That means you can run your entire tree on a single port and still get full motion video. I would use the other 15 ports for other interesting things.


    2018 - Moving and going to visit my Daughter in New Zealand. Most likely I will be dark or nearly dark, Some static stuff that is simple to put up.

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