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Thread: Need refresher about controller power limits

  1. #1
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    Default Need refresher about controller power limits

    So I have an e682 controller. I had an idea in my head, but I couldn't remember if it was correct as I couldn't find any specific documentation, so indulge me. E682 documentation lists that the 16 outputs are divided into two banks. Each bank has a capacity for 32 amps for the 8 outputs in it's bank. Further, each output is fused with a 5 amp fuse. Now, it's not stated that the output has a hard limit of 5 amps per output, as it just mentions that it comes with 5 amp fuse and that the fuse may need to be changed for some configurations. And it also occurs to me that even if you tried to run the full 5 amp worth of pixels on each output, you would technically be hitting 40 amps on the bank that is rated at 32. Now I remember being a little confused when I first was starting out with this, because it was also talking about running large numbers of pixels (both in the documentation and coming across that in multiple posts) on a single input, and the quick math put 100 pixels at 5 amps. So I remember being confused how people were saying they were running 400 pixels+ on an output, without blowing something. Now fast forward, I have it in my head that the reason I was given you could exceed the limits on things like amps per output or per bank, was because when running those kind of numbers, you would also have power injection points. If memory serves, the idea was that these extra sources of power with their own fuses effectively split the load. So to give an example, let's say I was running 40 amps worth of pixels on one side of the e682, bank #1 that states it has a capacity of 32 amps. If I had power injection points throughout, the bank on the e682 wasn't having all 40 amps being drawn through it. The load was spread out a bit. That's what my recollection is, but I have no idea if that is valid? Can anyone refresh my memory and advise on this concept since it's kind of an important one for safety? Electrical theory isn't in my background. IF that's an accurate concept, does it apply the same way to the individual output fuses? That I wouldn't blow a 5amp fuse on an output if I had other injection points?

  2. #2
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    Default Re: Need refresher about controller power limits

    Sounds like you got it. Current through the board is what matters. If you inject downstream then it's not going through your board. The 5 amp fuse only "sees' the current passing from the board to the pixels. (Although, your injection should probably be fused too, but you mention that.) Go to the wiki page and type 'power injection'. Pictures>words


    All that said, you don't have to run any power through your board if you don't want to. You could use ALL power injection.

    Good Luck!


    Power Injection page
    2012 - 12 Channels and an Arduino

  3. #3
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    Default Re: Need refresher about controller power limits

    Quote Originally Posted by rmcgee5 View Post
    Sounds like you got it. Current through the board is what matters. If you inject downstream then it's not going through your board. The 5 amp fuse only "sees' the current passing from the board to the pixels. (Although, your injection should probably be fused too, but you mention that.) Go to the wiki page and type 'power injection'. Pictures>words


    All that said, you don't have to run any power through your board if you don't want to. You could use ALL power injection.

    Good Luck!


    Power Injection page

    Lol, thanks. But me and that page have much history together If only it had a personal hit counter for me..... Yes, I always review that page every season, more than once. I just couldn't find anything specific that was like: "you can exceed this limit if _________". Now, the only question left is how do I get a rough idea how many other injection points I would need to ensure I don't exceed the limit. For example, with the 32 amp bank limit on the e682. Let's say theoretically I was running exactly a 32 amp load (no need to point out the stupidity of this example) and I add one power injection point at the end. I believe it references in the wiki that it should roughly cut or split the draw in half, so that the e682 side and the power injection side each have 16 amps. What I don't know, is if I add a 2nd power injection point, for a total of 3 points of power on that 32amp load, would it be as simple as splitting the load by the number of power points on the string? Like 6 power points on 30 amp run would split each power point to get roughly 5 amps each?

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    Default Re: Need refresher about controller power limits

    I'd never get anything done if I did calculations like that. If you HAVE to know, just put a meter on it. Even a Kill-o-watt meter on the wall would give you a good idea. What goes in must come out, minus small losses.

    One thing to note, I realized this year that one vendors T's can be wired to only provide power one way. So depending on what brand you have, or how your wiring them, you can easily make the controller only power the 1st string, and inject everything else. No overlap in current from the 1st string to the 2nd.
    2012 - 12 Channels and an Arduino

  5. #5
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    Default Re: Need refresher about controller power limits

    A controller board should state the amount of current it was designed to distribute -- more goes into this than just the 5 amp fuse.

    Jim stated that his board is capable of 32 amps - yet he has 5 amp fuses which means it could go as hi as 40 amps -- but THAT is bad thinking.

    If you look at the controller board you will find one trace that comes off the power terminal and the feeds the eight SPI ports. Depending if Jim used 1oz or 2 oz copper - will decide the width of the trace that is capable of conducting 32 amps while staying below a certain acceptable raise in trace/board temperature. I don't know what Jim did but that is one area of PCB design that can be easily "under designed" resulting in hi temperatures and burnt traces.

    As an example -- here is a trace width calculator: https://www.4pcb.com/trace-width-calculator.html If a board uses 2oz copper and wishes to keep the trace rise in temperature at 10C or 18F - the trace (external layer) needs to be just less than 3/4 inch (700 mil). The trace can continue to decrease as more ports consume current with the last ports at 5 amps being .054 inches. Ground lines need to follow the same design criteria.

    If you have to do power injection, design your system to keep current around 3 amps coming off each port - the board will run cooler and last a lot longer.

    When you look at power injection for a string of pixels -- just think of it as a single "resistor between the board and each injection point. The board and each power injection point will supply enough current where the voltages across the pixels (think resistors) come to equilibrium -- ohms law in action.

    A very easy way to reduce the number of injection points and the current coming from each point is to reduce your pixel intensity. Run your pixels at or below 40% and the current requirements drop big time.

    Just some more information to consider.

    Joe
    Link to my DownLoad Site: [B][COLOR=#ff0000][URL]http://www.joehinkle.com/HLS[/URL]

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