Hello you all,
first of all thank you in advance for reading me and sorry for my english!

I'm going to install in the ceiling some leds, 15m of ws2812, but i'm a little afraid about the size of the cables that the calculator suggests because the leds amperage are high, specs say 3,6A/m @full load, which is 54A for the whole length (15m) and i need 8m cables long (putting the power supply in the middle of the track); the calculator outputs 5awg (18mm2), which is really too much, specially compared to my goal which is 2,5mm2 (13awg)

So I thought how to resize them and researching on the internet i found two main solutions, but i really appreciate if you would please help me!

First idea was to split the strips, 1m (18w) short so they need less current and the cables could be thinner , but also this way it seems they have to be too big.
Second idea was to use higher voltage dc power supply, like 24v, to cover the area of the ceiling and lowering the voltage @ 5v just for the strip, but even this way seems to be hard to do (i should split every strip in 2 parts, which results in 6 dc-dc stepdown, too much money).

Fyi, the measured voltage drop per 1m seems to be 0.30V, and to be honest the measured amperage seems to be 1.5A/m @full load, not the declared 3.6.

Do I miss something? Am i wrong about all that stuff?
And other noob questions..if i use downsized cables, what is the risk? Just too much voltage drop (so yellowish leds) or too burn something?

Many thanks in advice!!

 

It seems to be common for LED lamp and luminaire manufacturers to publish power ratings that are much higher than the actual requirement.

This means that it is not a big surprise that you measured less than half the specified current.

Your idea of breaking the circuit up into several parallel strings with separate feed wires is a very good idea.

Assuming the power is coming from the AC mains locating a power supply near each strip or small group of strips is one way to cut down in high current wiring and is probably the best way provided that such wiring meets relevant safety codes.

You seem to already understand that the risks of using under-sized wiring are excessive voltage drop and the wires running warmer.

 

Many thanks for the reply Dick!

I was thinking another solution but I may lack of bases and i don't know if it's correct: can i use thinner cables if i "inject" current every (for example) meter, or less?

Thanks in advance!

 

Maybe, but I don't get a picture from your question.

 

My bad I'm sorry, i'll try to explain.

If i use a 5m straight strip led (without cuttting it in short pieces), and i connect DC power cables at the beginning of the strip, at the end of it and even every (for example) meter, i guess that the current flowing through the cables is less because it splits over every connection (they are in parallel in fact).
It seems to me (but in don't want to be wrong!) that the longest cable (the one that goes from the power supply to the beginning of the strip) should carrie less current because there are many other to "help".

And again, i'm sorry if i can't be clear!
Thanks and have a nice day

 

Ahhhhh..yes, driving the strip from both ends. Thomas Edison was given much praise in his (commissioned) biography for thinking of this as a way to save on the cost of copper for wires. Yes, that will allow you to reduce the size of your wire.

 

Thank you Dick for being so helpful!

I think i will do this (first on the bench to test): here in Italy we use mostly 2,5mm cables in houses (i think 13awg), and they are supposed to carry safely 16A. I will calculate how many centimeters the strips have to be to absorb at most half of that current, and i will connect every strip at least 2 times (both end), to help each cable to carry less amperage. And if i will see the leds fading to yellow (cause of voltage drop), i will inject power even in the middle. Obviously with a fuse for each power supply output. If that work on the bench i will install everything!