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Tomsauy , 01-13-2025, 10:00 AM

Hi all,
I am try to create my own LED stick with Easy EDA Pro.
I use SK6812 Mini LED, and I read on technical spec that it is better to put 0.1F capacitor short to the LED.
But I am not sure how to place it on PCB.
I have put 3 screens of 3 different ideas I have, but not sure sure which is the better or if there is wrong design.
I am clearly a beginner, no electronical formation (except many videos of @Robert Feranec thanks to him for his amazing job 🙂 )
Thanks in advanced for your help 🙂

Robert Feranec , 01-13-2025, 10:31 AM

direct track connection on the same layer between the pins is the best connection

Robert Feranec , 01-13-2025, 10:32 AM

https://youtu.be/XumNc480qYo

Tomsauy , 01-13-2025, 11:30 AM

Thanks for your answer 🙂
I watched this video, but I think it's beyond my skill level 😦 , and I had a hard time understanding it.
So, if I understand correctly, it is better to route like in the picture instead of using inner layer for 5V and route with VIA ? (I keep VIA and inner layer for GND only)

Robert Feranec , 01-13-2025, 11:34 AM

you can route power in inner layers. just the connection between cap and led pin is the best to have on the same layer

Robert Feranec , 01-13-2025, 11:35 AM

for this kind of circuit I don't think it is critical. but because you have the components on the same side of the pcb then it is good to connect decoupling capacitor pin with the led power pin with a direct track between them. power itself can be routed on other layers.

Tomsauy , 01-13-2025, 11:40 AM

OK so like this ?
Thanks again for your help ! 🙂

Tomsauy , 01-13-2025, 11:59 AM

And last question... sorry for been so beginner...
Is there any difference if I put my VIA like this ? Is it considered as "direct route" ?

Robert Feranec , 01-13-2025, 01:59 PM

I don't think it plays any role in this kind of circuit

QDrives , 01-13-2025, 04:52 PM

Why do you draw the connection lines from the LED out that way?
Why not as the green lines shown here?
What is the frequency of the signal?
I assume a 2 layer board, right? If so, leave the bottom to Gnd in my opinion.

Tomsauy , 01-13-2025, 05:08 PM

Because I thought it was better to take the pad in the correct orientation to start route... horizontally, in this case. But I am a beginner 😛

Initially, I started with a 4-layer PCB to also learn how to use the two inner layers. The bottom layer is unused in my initial configuration

For the signal frequency, I couldn't find anything relevant in the technical specification (https://jlcpcb.com/api/file/downloadByFileSystemAccessId/8554724280193294336).
Do you think I'm missing something ?

QDrives , 01-13-2025, 09:27 PM

No not missing something.
You could also use a bigger capacitor, something like 0805 or 1206 and have the command signal go under it. The capacitor would be more like parallel to pin 1-2 (now 2-3).

Tomsauy , 01-14-2025, 08:18 AM

thanks for your feedback !
So the left one is "theoretically a better route drawing" than the right one ?
(I know that in this case there is no importance but to be sure I understand well)

Robert Feranec , 01-14-2025, 05:19 PM

some people don't like this sharp angle here, otherwise ok

Robert Feranec , 01-14-2025, 05:21 PM

possibly, some people like to place the vias closer ...

Robert Feranec , 01-14-2025, 05:22 PM

Robert Feranec , 01-14-2025, 05:30 PM

but personally I am not that picky as often there is not really much options where exactly to place VIAs. Or even if there is space for vias, in many simple designs I just place the vias the way so the layout looks nice. also if vias are placed as I draw them above, some people will be saying that is the way how it should be done and other people may start saying that it is bad for assembly as the component may move during cooling down process etc .... but in reality I have not seen any problems. All these (sharp angle, vias close to each other, component movement during cooling down process, ...) I mostly only know them from internet and I have not done much investigation, tests or experiments by myself, just the via placement in the video I attached above. I have asked some people about them, but everyone will tell something different.

QDrives , 01-14-2025, 08:32 PM

"...but everyone will tell something different...." -- You get that too 😟 ?

Tomsauy , 01-15-2025, 02:41 PM

Thanks to all your feedback and comments @Robert Feranec & @QDrives, I was able to improve the design of this very simple board, so thank you for sharing your thoughts 🙂
Here are some screenshots of the design incorporating all your input and with both inner layer (Ground & 5V). Feel free to let me know if you think there’s room for improvement, even though I understand that design has a somewhat ‘personal’ aspect 🙂

On another note, regarding the technical specification of the LEDs, I read the following:
‘In practical application circuits, to prevent instantaneous high voltage damage to the internal signal input and output pins of the IC caused by live plugging and unplugging during testing, protective resistors should be connected in series at the signal input and output terminals. In addition, in order to ensure more stable operation between IC chips, the decoupling capacitance between each LED is essential.’
and
‘For soft or hard light strips with short transmission distance between lamp beads, it is recommended to connect protective resistors in series at the signal input and output terminals, R1, R2, about 500 ohms.’

So I added these two resistors, but I don’t understand the purpose of the resistor at the end of the circuit. If anyone has an explanation, I’d love to hear it.
Thanks again for your help!

QDrives , 01-15-2025, 08:06 PM

1) I think the output can be left open as you are not using it to daisy chain any further.
2) The capacitor is probably to close the the LED. Leave some room or expect production problems.
3) Eliminate the "acute angle" on teh 5V between the cap and LED.
4) For a simple board like this, I would go 2 layer. Saves you a few cents.
5) I would position the input resistor center-center to the LED.
6) I noticed that your 5V and ouput pads are now bigger than in the 'old' design.

Tomsauy , 01-16-2025, 09:11 AM

As usual, thanks for your feedback! 🙂
1 - I removed the resistor on the output.
2 - I moved down the capacitor (LED1 is the new placement, LED2 is the old one for comparison).
3 - Normally, there are no more acute angles with the new placement.
4 - I know that it could be possible, but as I said, this is also a learning experience for me, and the price for 10 boards is not too high. 🙂
5 - Done! 🙂
6 - Yes, the LED has changed due to an LCSC stock issue. The new one is the same but with a black front instead of a white one, and the footprint is slightly different.
New screenshot :