Parallel DC Conductors - Need Multiple Grounds?

Question

I'm working to power a 5m long strip of 60 WS2812B LEDs per meter. I have a 5V 300W DC power supply and am using 14 AWG wire. During my initial testing, the maximum distance between the strip and the power supply was ~2 feet, if not significantly less, so I never really had to worry about voltage drop.

However, my actual final product will have the LEDs ~10-25 feet from the power supply, but I'm working on a tight budget and attempting to be as economical with the wire as possible. (I need to wire up a bunch of strips, so I'll probably be buying more like 250' of wire -- that gets very expensive as the gauge goes up.) Since I have a 5V power supply and the WS2812B are happy with anything between 3.5 and 5.3V according to their datasheet, fiddling around with this voltage drop calculator tells me that, with the following settings, I can expect a final voltage of 3.71V at the strip:

• Material: Aluminum (My top contender is CCA wire.)
• Wire Size: 14 AWG
• Voltage: 5.5 (My PSU has a +/- 15% voltage adjust, so I'm assuming I'll dial it up to maximum and probably get more like +10%. If I actually get +15%, even better!)
• Number of Conductors: 2 conductors per phase in parallel.
• Distance: 25 feet (The absolute maximum distance I expect to have to run power.)
• Load Current: 18A (Maximum full-white current draw of one 5m 60LED/m strip)

I'm looking at buying 14/4 CCA wire for this project, but I'm not sure what the best practices are for running my power over multiple conductors, then combining them both at the PSU and at the strip. (The theory here is that I'm splitting the current over multiple conductors, so less current-per-conductor = less total voltage drop, right?)

For "2 conductors per phase in parallel," does that refer to, in 14/4 wire with individual insulation colors of red, black, white, and green:

A:

• Green: Connect to GND @ LED strip and V- on PSU.
• White: Connect to GND @ LED strip and V- on PSU as well.
• Red: Connect to +5V @ LED Strip and V+ on PSU.
• Black: Connect to +5V @ LED Strip and V+ on PSU as well.

or B:

• Green: Connect to GND @ LED strip and V- on PSU.
• White: Unused/Disconnected
• Red: Connect to +5V @ LED Strip and V+ on PSU.
• Black: Connect to +5V @ LED Strip and V+ on PSU as well.

In other words, does each positive connection need its own ground/return? I worry that A would create a ground loop, which would be especially bad considering I'm expecting to be working in an environment with a lot of nearby AC lines to induce current. (I'm in a theater, so lots of conduits everywhere carrying power to stage lighting, etc.) If B is the way to go, would I be able to use the unused conductor in the 14/4 as another positive conductor (essentially having "3 conductors per phase in parallel") and reduce my voltage drop even more? Is there an option C that I actually should be considering?

Answer 1

A is smart. B is not. 1 you are wasting a conductor. 2 no ground loop exists in A. Both ground connections are basically equal and act as a single path, and your setup won't know the difference between two 14 awg wires in parallel and one 12 awg wire.

B also results in twice the current in the green wire, which means higher power loss.

While two power cables do not need two ground returns, the facts of this setup show that it's better to use two. A ground loop normally happens when you have two power sources, not just one source on two wires.