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Thread: How to calculate size of wire needed to use as a bus wire for injection

  1. #1
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    Default How to calculate size of wire needed to use as a bus wire for injection

    So when I first started with 5v pixels, power injection was annoying to wrap my head around despite being a relatively straight forward concept. My original thinking on the actual wiring layout was could I have a bigger wire coming from the source, and then have it branch or tee off like short feeders where injection was needed. Or even one bigger wire splitting into multiple smaller ones at the end for injection. I can't recall the specific reasons, but when I brought it up, I was talked out of it as being a bad idea. I wanted to avoid a long run of wire for every injection point since I was running everything off of a handful of psu's, not to mention the drop from the long lead wire. Recently, on another post, someone had actually validated doing those original ideas as feasible. I'm perfectly fine at math, as long as I know what the formula or mechanism is. So in this case, if I was wanting to have a bigger "bus wire", and have smaller wires tapping off or something like this, say 18awg feeders, how do I figure out how big the source wire would have to be?

  2. #2
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    Nov 2011
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    Default Re: How to calculate size of wire needed to use as a bus wire for injection

    It's fundamentally pretty simple. Just addition. You need to figure out the total amount of current on each section of wire and size it appropriately. Each section needs to carry the sum of all downstream loads. If you've got small lines fused at 5A each, then the bigger wire needs to be sized for and fused at 20A. And where ever you tap from a larger wire to a smaller one, you fuse that branch for the smaller wire.

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