Individual WS2812B circuit: Do i need a capacitor?: Power distribution?

Question

I am currently designing a Circuit that is similar to typical WS2812B ARGB strips but seperatet into modules.
In the offical datasheet, there is no mention of using capacitors as noise protection, but in close to all similar models there is one (104, .1uF) for each lamp. As I am not that experienced with electrical circuit, my questions are:

• Is a Capacitor neccessary?
• If so, what type?
• Could I use one big Capacitor instead of the multiple single ones for each lamp?

.

For Power distribution, there will be 18 WS2812B Leds on each module and 6 White LEDs (datasheet)

• Would it be better to run a higher Voltage line to each module and the seperate the needed Voltages of it?
• Or could I connect the power of all of them in one Line?
• How many modules could I connect for each Voltage Level of the Main line if I run one?

You are welcome to point out bad components or mistakes I made.

This is the current circuit:

Answer 1

The capacitors are for decoupling of the supply lines. Each time a chip (inside each WS2812 there's a chip that controls the LEDs) is active, it draws some current from the supply. If that supply is not well decoupled, the voltage can become unstable and that can affect the behavior of the chip, in this case the WS2812. You might get the wrong color for example.

Decoupling capacitors are not always strictly needed in every situation. If your wires are short and your power supply has a high value capacitor at its output, extra decoupling might not be needed.

If you have long (and thin) wires then for sure you might have issues when you don't add any decoupling capacitors.

It is good practice to prevent issues and just add the decoupling capacitors. If you want to save a little cost, make sure there is a capacitor within (for example) 10 cm of each chip.

What you can do is make places available for a capacitor next to every WS2812. That does not mean there needs to be a capacitor in each place! You can try to and use your design without any capacitor and see if that works for you. I would just put a few capacitors here and there and see how that works. If you have issues you can easily add more capacitors (assuming you have added the soldering pads for one capacitor close to each WS2812).

Answer 2

If you have the WS2812B-2020 model then it says many times in the datasheet that the capacitor is not needed.

For any other earlier version of the WS2812B which is not the WS2812B-2020 model the capacitors are needed.

Capacitor is 100nF ceramic. Each chip must have a capacitor near it, one larger capacitor far away will not work.

Answer 3

Look closely at the "LED"s.

Yours may look different, I don't even know if this is a WS2812B. But notice, there is a minuscule capacitor inside! In this case the high frequency decoupling job is already done much closer to the chip than you could ever do by adding more ceramic caps on the board.

If your LEDs don't have a cap, then add one. You can add one anyway, component footprints are pretty much free.

Personally I'd add an electrolytic cap on each module, maybe on the back, if there is enough space. Largest capacitance in 6.3V that will fit into both the available width and ten cents, something like 470µF.

6 White LEDs (datasheet)

Datasheet for these LEDs specs Vf max 3.4V and you use a 3V3 power supply, so perhaps some of the LEDs won't light up properly. Better run it from 5V, but efficiency will be a bit low... unless the 3V3 comes from 5V from a linear regulator, in which case the difference will be wasted as heat anyway.