Greetings, fairly new to this group and fastled. Been learning arduino and fastLED over the winter. Working on upgrading an art installation i made last year with higher quality lighting using fastLED. last year i had 12v addressable led’s that came with a controller. My big question right now is power. I am going to have about 800 led’s which are in a circle. there will be 4 strips, 2 strips will be 5m and be 60led/m and 2 strips are aprox 4m and can be either 60leds/m or 30led/m. this installation will be outside at festivals and needs to be safe from the elements. I used 12v waterproof power supplies last year but i can’t find 5v power supplies that deliver enough power. at 800leds (this is with 2 strips being 30led/m) at 30ma per leds thats 24amps or 120watts. I am considering using a few buck converters to inject 5v power every meter or so around the circle. what i can’t figure out is what size 12v power supply will i need? Any thoughts or suggestions are greatly appreciated. you can see the art im talking about at http://www.inthecircle.ca … Thanks
Great piece! Very cool how people can move through it. Love that photo of it in the snow.
Using bucks for 12V to 5V and injecting every meter should work fine.
@marmil do you know how to figure what size 12v power supply i will need? does whats stay the same and amps and v change?
Basically you need to calculate the maximum wattage required on the 5V apply the efficiency of the buck converters and the calculate the amps required on the 12V PSU.
For example, if you will have all the WS2812 on full brightness white that would be 60 milliamps X 800 LEDs so 48 amps. That means a wattage of 5 X 48 = 240 watts.
If I assume 90% efficiency of the buck regulators that would mean the 12V PSU must be able to deliver 240 watts / 90% = 267 watts.
Therefore your 12V PSU must be able to supply 267W / 12V = 22.2 amps. I would round that up to at least 25 amps maybe even 30 amps !!
Ooops I think I totally missed that you were already using 12V strips.
Why do you want to inject 5V on those strips ??
@JP_Roy Sweet thanks. In the last couple hours thats what I came up with. Thanks for your help.
I believe the amount of Power used has to be equal on both sides of the buck. (Not accounting for efficiency losses in the buck. Which probably should be considered.)
So for example, on the 5V side, lets assume you need 50 Amps to power all the LEDs. Power = Amps x Voltage, so 50A x 5V = 250W. Therefore on the 12V side 250W / 12V = 20.83A.
Am I thinking about this correctly @JP_Roy ?
@JP_Roy Last years version was 12v strips which came with its own controller. now im upgrading to 5v individualy addressable lights to use Arduino and fastLED so i can program my own patterns.
i don’t think i’ll be running all the lights at full brightness as with the amount of lights it would be blinding. The lights behind the symbol i think we can assume will be half brightness. and the lights pointing inwards will generally be at half brightness. but i am thinking i’ll put a sensor in that makes the inside lights flash brighter for a moment when someone passes through it.
Hi @marmil , I think the buck converters are actually more efficient than 90% in general but I would still factor them in just to be on the safe side.
I should have hit refresh before posting. @JP_Roy you answered my question without you even knowing I was going to ask you. 
Hi @Eric_Inthecircle , ok that is what I initially thought but got confused after posting my comment and reading your post more carefully.
If you are sure to never go above 50% brightness, I would use that in your calculations but still… I always add an ‘overdesign’ factor to all my PSUs.
Another thing is that with all the WS2812 strips or WS2811 LEDs I got, I never measure 60 milliamps of current when driving them at full brightness white but more like 45 milliamps per LED.
You can safely use let’s say 25 miliamps (more than 50% ) X 800 = 20 amps ==> 100 watts so I would suggest a 150 watts 12V supply or more. It never hurts to overdesign a PSU, they tend to have bigger heatsinks and will run cooler and therefore are not likely to fail.
Thanks for all the information. that clears up a bunch of confusion i had about it. Im looking at getting this PSU http://www.meanwell.com/webapp/product/search.aspx?prod=HLG-320H which is 12v 22a
@Eric_Inthecircle Looks like a good PSU choice !!
Thanks… and it just fits inside the portal also.
That is some truly amazing work!!! I want your workshop!!!
@James_G Thanks im glad you like it. What do you mean by workshop?
@Eric_Inthecircle All your cnc tools 
@James_G Oh… haha it’s not my workshop. It’s a maker space that I’m a member of… I don’t even have my own shop… Yet