Hello (see my document) I don’t understand why I have a power problem with my LEDs. indeed the white is no longer white after a few meters.
I have 200 LEDs for a 5V 60A power supply, it’s more than enough for this number of LEDs!
in addition, I followed the wiring diagrams indicated in my document, so as not to have a white problem and I still have problems!
at the beginning of my 20 meter cable I have 5V and at the end of 2V…
Someone would have any idea ?
First, when you inject, you need both positive and negative.
Also, maybe your wires are too thin.
That seems like an awfully long run from the power supply to the far end injection point. Anyway to move the power supply so it’s physically more in the middle of that run? Or run the injection feed the other way to it’s shorter?
Also, make sure you are using heavy duty enough stranded wire. I have switched to using polarized, stranded 12ga landscape light cable as my default for any run longer than about 10 feet/3m. It’s prolly overkill, but…
But, even with 12ga wire, distance and power draw (amps/current) are going to put some real practical limits.
In the end, it’s all about wire gauge and distance from the power supply. If you are seeing only 2V, it’s not the power supply, it’s the cable gauge/length/both. And unfortunately, the only way to be sure is to try different lengths and gauges out until you get closer to 5V.
I’ve had issue with long LED runs even with optimally placed wiring and heavy gauge wires. In one really problematic case, I situated the power supply as close to the center (i.e. distance from PS to each end of the LEDs was close to same) and then amped up the power supply to 5.2V (which wound up being about 5V at the injection points). Most PS’s have an adjustment pot, but you have to be very careful to not over-volt and blow out your LEDs - easier than you’d think.
tanks gduprey for the answer.
to test, I tried to pass a “flying” electric wire diagonally to divide the distance by two. actually I have 5v and my white is white but that just moved the problem 4/5 meters further.
As you can see in my photo, the cables pass through the false ceiling, so I can’t move my power supply inside, it’s too big…
Are there any small enough 5v voltage boosters that could fit through a hole the size of a spotlight?
You likely need more than 1 injection. I would have power at the beginning, middle and end. If your wire is not able to bring 5v that far you either need larger wire or need to feed a higher voltage (12 or 24v) down the lines and use buck converters to reduce it to 5v at or near injection points.
with 5v i usually inject every 5m/300 led and have no issues with whites
Certainly power issues.
Have you measured the voltage at point where you are loosing white, I am very sure it’s not even close to 5v.
Use thick copper wires for power injection, Here in India we use 2.5mm pure copper wires to suppress these issues, when distance is large, additional power supply is the best way to solve it.
When doing power injection with thin wire, please check the voltage at injection point before and after the injection for best results.
A skeptical system to work with but would give you very good results.
All the best 
