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After always being interested in learning more about electronics, I figured LED-strips would be a great start.

I'd like to power a 4 meter WS2812B-LED-strip (60 LEDs/m). These run on 5V and draw about 60mA per LED. That's 14.5A, or 75W. However, I've yet to find any power supplies for these figures, only imported industrial ones - which feels a bit scary with my limited knowledge.

I've understand that powering it through the Arduino is a bad idea, but what's the simplest and cheapest solution for powering it? I do have a bunch of old supplies for laptops and whatnot lying around.

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  • \$\begingroup\$ At those kinds of currents/power, you can set your house on fire, so you'd better find something more tame to make your debut in EE. If using industrial PSUs is "a bit scary", why do you think that improvising something would be safer? \$\endgroup\$ – Fizz Oct 8 '15 at 16:48
  • \$\begingroup\$ @RespawnedFluff I've found several consumer level supplies for 10A (which seems to be the magic limit), I'm confident that I can handle the soldering part. I could reduce the strip to 3 meters and then using the 10A supply -- would you still consider it a bad idea? \$\endgroup\$ – Zar Oct 8 '15 at 16:51
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    \$\begingroup\$ If you cut the strip into two halves, the current for each is 14.5/2=7.25, so two 10A power supplies would be enough (you always want some headroom; I'd be tempted to cut into three pieces and use 3 PSU's to give 100% headroom if it's possible the PSUs aren't well ventilated). Join the data-out of one half to the data-in of the other and drive as one strip, or just drive the two data-in's of the two halves independently. \$\endgroup\$ – gbulmer Oct 8 '15 at 19:51
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I built a screen (total of about 240m @ 60/m, divided into 4 panels) for burning man. Each strip in a panel was 75 LEDs long (1.25m). I tied 8 of the strips together at the ends (so 8 strips of 75 LEDs in parallel) and ran two of these sets of 8 off of one power supply. I calculated out that at half power, (128 to each color for the entire set of strips), 8 strips (75 LEDs x 8, so 600 LEDs) took about 8.5A @ 5V. I used a cheep Chinese 300w smps (well, a total of 8 of them actually). But ya, the Arduino by itself won't do the powering. It can drive the data line just fine (since technically it's only pushing the data to 1 2812).

So as a suggestion, make sure you power each 1m strip individually instead of tying them all together and having every LED in parallel (and the strips themselves in series). What I mean by this is, tie the +V of all the strips together to one power wire, and then tie all the grounds together. Don't just line up all the strips in a single line, end to end, and solder them. Just the data line should be like this.

You will want about a 40W power supply (for 8A @ 5V). And try to avoid turning them on at 255,255,255 (full brightness) as then tend to use a lot of power and get really hot. You can get a Chinese power supply for like $10 from ebay that will power it for you.

PS. My avatar is a 16x16 panel of those WS2812B strips @ 60 LEDs/m

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  • \$\begingroup\$ Thank you very much for your answer! Won't mounting them in parallel (instead of serially) just reduce voltage drops? Or did you mean one 40W power supply for each 1m strip? \$\endgroup\$ – Zar Oct 8 '15 at 18:45
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    \$\begingroup\$ Yes, mounting them in parallel will reduce voltage drops but it also means less current loss on the traces of the strip. It may also have an effect on the performance of the 2812 itself, noise wise. It's not a bad drop over 2m but beyond that you might start getting some heat and the LEDs won't be as bright. However, internal to the chip in the 2812 is a constant current regulator (I believe). But a 40W power supply should be fine for all 4 meters (or 240 LEDs). \$\endgroup\$ – Branden Boucher Oct 8 '15 at 20:23
  • \$\begingroup\$ I think I'll play it safe and order two 10A @ 5V PSUs, which probably is overkill, but I'm sure I can find other usages for them later :-). Thank you very much for your help, it's much appreciated! \$\endgroup\$ – Zar Oct 9 '15 at 12:11
  • \$\begingroup\$ No Problem. And ya, you could make use of the PSUs later anyways! So go for it if you can afford it. Just try not to drive the LEDs at full brightness on any of the colors for too long, especially on all of them at once. \$\endgroup\$ – Branden Boucher Oct 9 '15 at 14:23

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