I made my first schematic for an electronics project. Since this is the first time there'll probably be a lot of beginner mistakes and it would be really helpful if someone could check it for wiring errors.

I try to make a Controller for LED-Strips like the ws2812b that can read animations from an micro sd card. So Vin is a 5V supply for higher currents (e.g. 6A) to drive at least some of the LEDs. Since regulating high currents on the pcb seems to be too complicated for my first project I chose to only regulate the voltage for the Microcontroller. Will this be sufficient for the LEDs?

The 5V and 3.3V regulator are wired like suggested from their datasheets.

The MCU is a ATMega328P. The wiring is almost identical to an Arduino Nano without USB to Serial Chip.

For the Micro SD card there is a logic level shifter (5V from MCU to 3.3V for Micro SD Card) to convert the SPI signal.

The breakout for SPI is for programming the MCU. Those for I2C and UART are there to allow me adding further functions later (It is a first test version after all).

The last three breakouts are for a powerswitch, a button (I tried to pull it down and to debounce it) which will make it possible to switch the animation and a potentiometer to control the lightness.

I hope the description is detailed enough. I'm thankful for every tip I can get.

Circuit Schematic

  • 1
    \$\begingroup\$ Regarding some general structuring aspects for a schematic, you might find some points of this useful electronics.stackexchange.com/questions/28251/… \$\endgroup\$ Aug 9, 2020 at 12:59
  • \$\begingroup\$ Thank you! Those are really helpful tips for making better schematics. \$\endgroup\$
    – Mt_266
    Aug 9, 2020 at 14:30
  • \$\begingroup\$ It's nice to see net-names used instead of a rats nest of wires. When you turn this into a PCB layout, remember to place your decoupling caps C4 & C5 right next to the power pins on the micro. Compare this schematic & layout for lots of 'what not to do' examples. \$\endgroup\$
    – brhans
    Aug 9, 2020 at 15:02
  • \$\begingroup\$ Okay, I’ll try to lay it out that way! Thank you a lot for helping me! \$\endgroup\$
    – Mt_266
    Aug 9, 2020 at 18:05
  • \$\begingroup\$ Just a suggestion, perhaps you can power up the MCU with 3.3V so you can communicate directly with the SD Card? Then use a level shifter with a lower pin count for the WS2812B? MCU with 3.3V also provides better interfacing compatibility for your SPI/ I2C/ UART. \$\endgroup\$
    – Carla H.
    Mar 22, 2021 at 16:15

1 Answer 1


Not bad for a first try!

  • I'd connect the OE pin of the TXB0108 to VCCA, not sure from the datasheet if it's OK to leave it floating.
  • If you want to use the I2C interface, you need a pullup resistor on both SCL and SDA. If you want to do that on the extension board, that's alright.
  • Maybe include a GND pin on the UART connector as well?
  • Is the EN pin of the TPS63002 actually connected? Looks like a junction is missing.
  • 10uF output capacitance seems to be on the low side for the TPS63002, but with the low power consumption of this circuit it's probably fine.

The rest looks good to me, no guarantees though as always. Just build and test it. If your VIN stays between 4.5 and 5.5V the WS2812 should be happy.


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