PSU Voltage Adjustment how far can you push it?

[Matt Smith]

Hi There,

I'm designing a setup where I will always be using a 10m extension cable (whether or not I need it) for each strip. Obviously this is inefficient but it means that I can always have the correct voltage going to the led strips without having to consider changing cable thickness loads etc.
Setup
10m 2.5mm "extension" cable from psu to led strips, strips then power inject in a y split fashion for 4m each (4a per led strip)
4m of WS2812B 12v led strip with 12v-5v DC DC convs
50 Amp eBay PSU running max 35 amps (70% capacity)
Total voltage loss from 10m cable at 8a load is approx 1.03 volts.

So I'm hoping I can just run my PSU at 12.8-13.0 volts to counteract it so that the led strips get full 12v. Will this cause them to overheat or be unstable?

 

[David_AVD]

Increasing the source (power supply) voltage to make up for cables losses is generally not a good idea.

While the load (the LED strips) may see the correct voltage when drawing higher current, the voltage to them will rise (less drop in the cable) when they are not.

This may not be an issue if the LED strips are rated to handle a higher voltage (the same as the adjusted power supply). However, some LED strips will start to glow even when they are supposed to be off when the applied voltage it too high.

Alternative solutions such as thicker cabling or the use of DC-DC converters close to the load are preferred. YMMV and all that of course.

 

[AAH]

I was about to type exactly what David said.
Unless you are running the leds at all 100% white at all times then you are going to be supplying the leds (particularly the 1st ones in string) with higher than 12V. When you turn on only a few leds they will be getting 13V vs 12V when all the leds are on at 100%. A 1V is usually well within the tolerance before you get any voltage drop issues. Supplying power injection from 1 end of the string to the other will probably overcome any issue that you could have. Running 10m of 2.5mm2 extension cable shouldn't give you much drop at all imho (and without crunching numbers).

 

[Matt Smith]

Ahh yes thank you I didn't even consider when not at full load. I spoke to Ray and he thinks it's safe to run the LED's between 14 and 11.5 volts which is way more variation than I need. Keep in mind this is only for the WS2812B 12V version and might vary depending on strip choice

2.5mm2 @10m is 1.03V loss. so nothing too major. Cable arrives today so I'll do some experimenting and post the results!

 

[djgra79]

I'm by no means an expert but I take on board what David & Alan have said.
I too thought similar in my early days and had a PSU nudged up above 12v, and I had issues with pixels not actually working proper, if at all. Bringing the PSU back down to 12v solved that issue, so now power injection along every 100 or so pixels (at 12v) works for me. No such thing as over injecting from the same PSU so there should be no reason to have the PSU above the voltage of the pixels.
Another thing to note is the total capacity of the PSU. If its a cheap Ray Wu PSU, I only ever max it out at 80% of the 350w capability. Sure this is assuming full white which hardly ever happens during the show, but these PSUs have a history (with others) of not lasting the distance when pushed to the max. Meanwell PSU on the other hand I understand will work regardless of how they are pushed, as they are built to much higher standards, but you'll pay more for these.

 

[fasteddy]

I would normally use the 5% rule when applying overvoltage. Because most electronics have a tolerance of approx. 5%, anything above 5% and then your risks of cooking something increase