Electricity, current and avoiding a meltdown

Hi. There is something I am trying to grapple with especially as it relates to creating circuits that are safe and free of the risk of a meltdown or fire. I have a project that involves 3x 5m strip’s (5v) with 60 LEDs / metre. Not being precise but let’s say that I intend to use a 5v 30A power supply. Now we all know how thin the factory attached wires are on an LED strip. If I construct most of my circuit with the sort of thick wire that is rated to 30A, I still have these bottleneck connections where the circuit goes from very thick to very thin wire. Is this a situation where cable resistance can introduce a risk of heat, melting and/or fire? I can’t see a way to avoid this scenario. It is always playing on my mind whether I am playing safe. Can somebody with more circuit know-how than I offer their thoughts please? Thanks. M

If I am understanding your concern, your injection “trunk” wires are heavier, but what you use to actually connect the strips can be thinner as the copper used on them can’t handle that much current. I’ve seen people use 5A for how much the strips themselves can reliably carry.

Hi @tonyno - thanks for your interest! Perhaps a diagram will illustrate my point more clearly. Attached is an adaptation of the circuit diagram on WLED’s wiki . If my strips - overall require a power supply of 30A, and my injection trunk is of a certain guage. From my basic understanding of wiring circuits - everywhere on my circuit diagram where thick meets thin; there is potential for heat and too much load. Is that clearer?

That’s how you do it and won’t cause problems as long as your injection points are not too far apart. :wink:

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OK, I’ll stop worrying then. Thank you.

That gave me an idea to add to my diagram. Thanks.

My pleasure! But how do you mean? Did you create the original diagram on the wiki?
If so, what’s with the 1000uF capacitor? Should that be in place at each injection point?

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I did. The cap acts as a local, voltage reserve. That could be a good idea.

Fair enough. Thanks again.

If you want to wire to “code” whether it be a CE standard, NEC/NFPA, or some other national or international standard, the basic concept for LED power wiring is never let a wire become a fuse.

For your specific example (to meet the intent of code), a 30A power supply may have 30A output overcurrent protection internal to the supply. It also may not. If it does not, then all the wires need to be rated to carry all the current the supply can produce, or rated to carry 30A.

Since 30A wire is so big, bulky, and expensive, what might work best is to run single pair of wiring rated @ 30A from a 30A fuse at the output of the supply (if your supply does not have internal overcurrent protection, or you don’t trust it), to a distribution block close to the middle of a lengthy LED strip to keep the wire lengths about the same.

From that distribution block, each injection feed can have a separate fuse rated for current needed to power 2x # of LEDs for each section. Then the wire can also be smaller.

     60             60            60          60
╔░░░░░░░░░░░░╦░░░░░░░░░░░░░╦░░░░░░░░░░░░╦░░░░░░░░░░░░░╗ ← LEDS
║            ║             ║            ║             ║
 \           ║             ║            ║            /
  \          ║             ║            ║           /
   \         ║             ║            ║          /
    \        ║             ║            ║         /
     \       ║             ║            ║        /
      ○      ○             ○            ○       ○
       )15A  )15A          )15A         )15A    )15A
      (     (             (            (       (
 │                   Distribution block              │
                  to power supply (30A)
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Thank you @huggy-d1 - that very much confirms my original concern and makes sense from a electrical engineering perspective.

Apologies - @tonyno , but I may mark this as the solution to my question. Hope that is OK by you.

Thank you both!

From your drawing its not clear if you are injecting power at the beginning and end of each strip. If so then does that mean you are injecting power twice where the strips come together? If so that shouldn’t be needed. Power will bridge between strips naturally. You only need to inject power either at the beginning or end of each strip. I had an issue when I doubled up power where the strips come together.

For small voltage drop strips, you can get away with only injecting power in the middle. Just a thought.