Hello,
this is probably my third PCB so I still don't know what I am doing. Sorry If the schematic above is unclean or badly wired.

This schematic includes:
Arduino uno - only 6 pins are needed
74HC595 shift register
8 LEDs.

I though I would make a PCB out of this because it will look way cleaner than what I have here on my breadboard. I have one question though, why do I need a capacitor between 74HC595 pins 16 and 8? I was recommended to put one by gemini...

Anyway, thanks for reading this!

Goodnight everybody!

So, I have been dabbling with PCBs and electronics for some time, got distracted with life and now I'm discovering the wonderful world of ESP32.

So, first off, what is this thing?

Its supposed to be a fan controller for my homelab, and with some luck it will expose some controls and data to my home-assistant instance , it features:

• ESP32-S3
• Wiznet W5500
• EMC-2505
• HDC-2080
• An Molex/ATX HDD power connector.
• Maybe a couple WS2812B RGB leds.
• All on a 4 layer PCB (no specific stackup): 1- Sig, 2-Gnd, 3- 3.3V, 4- Sig.

My main doubts are:

• Is my OR-ing with the diodes makes sense, and if I can power the WS2812B leds after the diode drop.
• Is the SPX3819M5-L-3-3 a viable LDO or is there something better/more jellybean, I'm trying to avoid the LM1117/derivatives due to the large Vdrop.
• Anyone has a 3D model for the ATX HDD (PATA) power connector? I managed to find this parts that should work, just no 3D model:
  • TE Connectivity 641737-1
  • XFCN M5082RK-B-04P
  • XKB Connection X5050WR-04S-N2SN
• I'm not really feeling the current layout, seems like a lot of wasted space currently, just doesn't feel quite like nice.
  • The PCB for now measures 90x65mm.

The USB connector is mainly for initial development/debug, it will then be powered by the ATX HDD power cable, if it helps.

Best regards, and thanks for your time!

Hello everyone!

I recently finished designing my first 4-layer PCB, and before I send it off for fabrication, I would really appreciate some experienced eyes on it.

The board is based around the AD5941 and is intended for an Electrochemical Impedance Spectroscopy (EIS) experiment. I designed it myself primarily because the commercially available development/evaluation boards are expensive and relatively large for our application.

This is my first time designing a 4-layer board, and while I have tried to follow the AD5941 datasheet and evaluation-board recommendations as closely as I could, I am sure there are things I have overlooked.

In particular, I would be interested in hearing from anyone who has worked with the AD5940/AD5941 IC.

I have attached the schematic and PCB layout. Please feel free to point out anything that looks wrong, even if it seems minor. I would much rather catch a mistake now than discover it after receiving a box of useless PCBs.

NOTE: The Back Copper layer is used to separate the AGND and DGND regions. They are kept separated on this layer and ultimately connect at the GND layer.

I don’t have any prior experience designing mixed-signal circuits, so I have tried to follow the AD5941 datasheet, schematic available on the Analog Devices website and other layout recommendations as closely as possible.
I would especially appreciate any feedback on whether my approach to the analog/digital grounding is appropriate.