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I am planning on having a large number of programmable LED strips powered by a 5v 150W supply I got from Digikey. The LEDs (APA102) will be controlled using an Arduino, which will also be powered by the same supply. The 5v supply will be wired to the LED strips individually. The total number of strips will be 32 (30-60cm lengths) hanging from the ceiling. The longest run of the 5v power line will be 10 meters. The highest current, near the supply, will be 25A.

Do you know what gauge wire I should use for the 5v supply line?

I was thinking of sacrificing a good power cable and having the strips soldered to the cable at various points. Do you think this should work well and safely?

Thanks in advance.

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    \$\begingroup\$ Figure out what temperature rise above ambient would be safe, and put all that into one of the dozens of wire gauge calculators across the Internet. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 17 '17 at 17:09
  • \$\begingroup\$ Do you HAVE to have all the strips on the same power line? I think it theory it is possible, but it might be wiser to divide and conquer. \$\endgroup\$ – MAB Jul 17 '17 at 18:08
  • \$\begingroup\$ I have found lots of information and tables regarding AC, as well as higher voltage DC. But I have not found anything for 5 V DC. \$\endgroup\$ – Fed Jul 17 '17 at 18:22
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These are LEDs that have an integrated processor. So unlike a typical LED, controlling the voltage, instead of the current, to each LED is the primary design goal. As such, the issue of wire gauge becomes a question of voltage drop in the wire due to the current passing through the wire.

The LED spec sheet does not specify a minimum voltage but instead lists a typical voltage of 5.0 and a maximum of 5.5. For the purpose of this analysis, we will assume a minimum voltage of 4.75 volts. The maximum current per chip is 26.5 mA. Assuming 60 LED chips per meter, a 60 cm strip would draw 36 * 26.5 mA or ~ 1 amp.

To provide no less than 4.75 volts per strip, the wiring must have no more than 0.25 volts / 1 amp or 0.25 ohms. The longest wire length is 10 meters but there will be twice that in total wire length to account for the positive and negative wires. This gives us a resistance budget of 0.25 ohms / 20 meters or 0.0125 ohms per meter. Consulting a copper wire chart, 15 ga wire or larger would be suitable.

By following the above math, you can calculate the minimum wire gauge for any number of LEDs per wire run.

Given the large total current of the supply, it would be wise to fuse the various wire runs in no more than 5 amps per segment. The fuses should be located at the supply connector.

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  • \$\begingroup\$ That was great, thanks. I was assuming the APA102 can draw a max of 20mA per LED (R G and B) totalling 60mA per chip. At 30/m, that is 1.8A per strip. So, 0.25v/1.8A=0.139 ohms, and so over 20m that would be 0.006 ohms/m. The chart I found indicates I would need 13 gauge minimum. I like limiting the fuses to 5A each, so that would be a fuse for 3 strips. What about the wire limitations due to current at 5v, especially at the power supply output that feeds all the fuses? \$\endgroup\$ – Fed Jul 18 '17 at 10:58
  • \$\begingroup\$ For the distribution bus, use a short section of 10 ga or larger wire. 1 meter of 10 ga wire is 0.00328 ohms. This times 25 amps is an additional voltage drop of 0.082 volts. \$\endgroup\$ – Glenn W9IQ Jul 18 '17 at 11:16
  • \$\begingroup\$ Great. And how can I find out about the high current (25A at source) at 5v? \$\endgroup\$ – Fed Jul 18 '17 at 11:20
  • \$\begingroup\$ I am not sure what you mean by that. Can you clarify? \$\endgroup\$ – Glenn W9IQ Jul 18 '17 at 11:21
  • \$\begingroup\$ Maybe I am wrong, but isn't there a safety concern with too much current moving in a wire, and a certain thickness is needed? I was wondering what that gauge would be for 26A 5v. \$\endgroup\$ – Fed Jul 18 '17 at 11:31

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