Given the following "circuit", I'm trying to find out what the correct wires gauge should be for the points: A,B and C.


  • I have 15 LED strips (WS2815, DC 12V / 60 LEDs per meter).
  • Each segment is ~ 90 cm / 30 ft long
  • Each segment is separately connected to the power-bus (parallel).
  • Each segment contains 54 LED's
  • Each LED uses (according to the datasheet) 15 mA

I made the following calculations:

  • Current per segment is: 54 * 15 = 810 mA
  • There are a total of 15 segments, which makes the total current 15*810 mA = 12.5 A (~ 150 Watts total).

What I wanna know are the correct wire gauges for: A, B and C.

I used some online wire-gauge-calculations for this, so I take it with a pinch of salt. If the above calculations are correct:

  • A = the main power, a minimum of 2.5 mm2 (14 AWG) would be needed?
  • B = the segment power, a minimum of 1 mm2 (17 AWG) would be needed?

C wires are connected in series, which makes the cable much longer. I have no idea how to deal with this?

Maybe someone can tell me if the basic calculations are correct? And what would be the best way to deal with the C wire?

  • \$\begingroup\$ Aside from using online calculators, you can look up the resistance of each wire gauge per length, multiply times your length, and then calculate the voltage drop across it using Ohms law (V=I*R). Your goal is to keep that drop on all segments small, maybe half a volt summed across all segments. The gauge of the data lines is irrelevant, but at those lengths you may have signal integrity issues, so a twisted pair cable and a 5V driver that is impedance matched to it is a good idea. \$\endgroup\$ Aug 5 at 17:08
  • \$\begingroup\$ For the A power cable, you need to specify the spacing of the taps. Are they all equal? I would suspect that the portion from the power supply to the first strip is longer. \$\endgroup\$
    – Mattman944
    Aug 5 at 21:40
  • \$\begingroup\$ The strips have significant resistance on the power lines. If you are only powering from one end, you should measure the voltage at the other end and account for this. The vendor often recommends that you power long strips from both ends. \$\endgroup\$
    – Mattman944
    Aug 5 at 21:42
  • \$\begingroup\$ if the strips are laid side by side, then alternate the orientation of the strips, so that the data lines are kept short \$\endgroup\$
    – jsotola
    Aug 5 at 21:56


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.