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.
Best Answer
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.