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I have a 5 metre strand of WS2812B LEDs, at 18W per metre.

I also have a 120V to 5V-30A power supply I plan to connect them to. The data pin will be connected to (for now), a PWM pin on an Arduino Uno R3.

Now, I've found documentation that states:

Before connecting NeoPixels to any large power source (DC “wall wart” or even a large battery), add a capacitor (1000 µF, 6.3V or higher) across the + and – terminals

You can find that reference in Adafruit's Best Practices.

I don't have any 1000 µF caps. I do have a dozen 470 µF caps rated at 25V.

First question: Can I put two (or more) of these in parallel in order to get the same effect?

Second question: If I connect power to both ends (or even three locations) of the strip, can I run each feed from this single amalgamation of capacitors, or does each feed into the LED strip require its own?

Third question: Will it be safe to use just a single 470 µF cap in place of 1000 µF?

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  • \$\begingroup\$ "1kμF" is certainly an unusual thing to see! (the proper way of writing that would be 1mF) \$\endgroup\$
    – Hearth
    Sep 14 '19 at 23:29
  • \$\begingroup\$ @Hearth I'm sorry. I meant 1000µF, per the doc I referenced. \$\endgroup\$
    – stevieb
    Sep 14 '19 at 23:32
  • \$\begingroup\$ Right, and 1000 microfarads is 1 millifarad. \$\endgroup\$
    – Hearth
    Sep 14 '19 at 23:34
  • \$\begingroup\$ @Hearth, just think of it like old documents that talk about "kilomegacycles" instead of gigahertz. \$\endgroup\$
    – The Photon
    Sep 14 '19 at 23:36
  • \$\begingroup\$ @stevieb You might want to look up the SI prefix system. It's a standard system that applies to all units. Well, mostly just SI units, you'll get weird looks if you start talking about milligallons. \$\endgroup\$
    – Hearth
    Sep 14 '19 at 23:41
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yes, two 470uf parts in parallel is almost as good as 1000uF, and Adafruit is being over-cautious to prevent disappointment, three would be better than two, but honestly, one is probably sufficient.

If powering from multiple locations it's probably a good idea to put capacitors at each junction with the strip.

But the strip already includes small capacitors next to each module so they probably not needed. having the capacitors where the signal enters the strip will help prevent ground bounce which could otherwise mess up the signal resulting in the wrong pattern being displayed.

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  • \$\begingroup\$ Assuming they are electrolytic, I would argue that two parallel 470μF caps will have superior performance in comparison to a single 1mF cap in most cases due to reduced ESR and increased ripple current capacity. \$\endgroup\$
    – Caleb Reister
    Sep 19 '19 at 18:30
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1) Using the capacitors in parallel works the same as a single, bigger capacitor in this case. 940uF Should be good enough, hell, might even work, but if it were my project I'd use three just to be sure.

2) Again, you'd probably be fine routing all three power lines through the capacitor amalgamation, but its probably a good idea to protect each line individually

3)I probably wouldn't, but, if you're REALLY strapped for caps, it might be okay. If you're working with LED tape I'd probably test it on a small strip before hand just to make sure you're safe.

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