Voltage drop problem w/power injection

Hi, i have a couple of trees that are experiencing rather severe voltage drop and I don’t understand why…


Each tree is 251x5V WS2811 LEDs powered by it’s own 15A power supply. The size of the tree is 8 columns of 30 LEDs each, plus the 11 LED star. I am injecting 5V at the end of every two columns (the tree is wired in serpentine fashion) and the star is it’s own channel. The LEDs are never powered more than than 1/2 of 255+255+255 (eg. full white is 128x128x128, and other colors are scaled via a human perception algorithm). Power should not be an issue. Oh, and the wire that I’m using to do the injection is 18ga. The power supply is right at the tree, not at a distance. Yet, if I set the whole tree to white, or something plus white, white becomes increasingly orange from the left column to the right.

I measured the voltage at the left column, and it’s 5.06V. At the end of the right column it’s 3.90v. It behaves as it there is no injection at all. I don’t get it.

Are you adding both +5V and Ground lines at each injection point?

In general your math sounds reasonable.
I would have probably used the base of the tree as a “power bus” area.
If you number the strips in your pic 1-8 from left to right, then tie +5 and Gnd together at the base of 1&2, 3&4, 5&6, 7&8.
Those also become 4 injection points to your power supply.
At the top of each pair, you only need to connect the ground lines together.
Data connections remain the same as before, serpentine fashion.

You could even splurge a little and use 14AWG wire for the “base bus” in which case you can tie all the strips +5V and Gnd’s together at the bottom, tie the pair Grounds together at the top and get away with a single PS to “base bus” connection of 14AWG (if it’s reasonably short). I’d do that in the middle of the bus.

Your total base length looks reasonably short so I’d think seriously about my 2nd suggestion to simplify your power wiring and injection points.

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Make sure the brightness limiter in LED Preference is set accordingly or turned off. (Remember it is in mA so 15A would be 15000mA)

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You have to “inject” ground as well as +5V? I only did +5V at columns 1, 3, 5, 7, 8. Also, do you think two 18ga wires are as good as one 14ga?


Power goes in via +5V and returns via Gnd.
If you only add extra on the +5V side, you’re asking the ground to handle twice the returns.
You can think of it as only adding a 20AWG wire for injection when you use 1 line of 18AWG.

There are some multi-wire to equivalent AWG calculators out there, but I think you’re into at least 3x18AWG to get a 14AWG equivalent.
I’d still go the Big Bottom Bus route since the wires are likely short and it’s reasonably cheap to use 14AWG.
Think about putting your PS in a box right inside the base of the tree.
Makes your injection lines very short.

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