Soundcard in the current year? I think most people go for a USB DAC or stick with the motherboard audio. Especially on such an expensive mainboard I would expect it to be fine ^^

*goes up in lithium smoke cutely*

Fair. It's just hard to find fans in the 8k+ RPM range that only take 5V that are ALSO 4-wire fans. That's why I wanted to make 12V possible.

Also, with the lithium being handled by a commercial powerbank, I don't feel it's super risky.

I removed the PD trigger chip to save board space and cost.

This has the advantage that this design now works with literally any USB source, even low powered ones like computer USB ports and USB A to C cables!

The USB-C source is activated using two 5.1k resistors on the CC lines now. I had provisioned connections of the CC lines to the microcontroller so I could do spec-compliant voltage sensing before turning the load on.

But luckily even on the highest power settings, I draw less than 500mA.

PCB photos!

Saved:
- chip to request 12V via USB-C PD
- 12v to 5V linear regular

New:
- Boost converter based on the LM2735X

I also made the debug connections pads instead of through-holes to make room on the other side for SMD stuff.

Happy birthday!

PCB Designed with EasyEDA, produced and assembled by JLCPCB.

Software written in Rust, using Embassy and embassy-stm32.

Plastic pieces printed on my Bambu Lab X1C w/ AMS. PETG in Black and Sky Blue, TPU is 95A hardness.

Design files and software available at github.com/RAnders00/us...!

Have some PCB photos.

Nerd statistics:
- STM32 (STM32F103C8T6)
- USB Type C PD-chip HUSB238 (to get 12V)
- LDOs making 5V and 3.3V
- Level shifter to make the correct 25kHz 5V PWM signal for the fan
- Variable dummy load to keep power bank on (for low fan speeds)
- RGB LED to indicate power level

It‘s quite nice to be able to change the speed. Rave at full speed, or have conversations at low speed. Best of both worlds!

Step 4: Final installation. I asked my maker @equinoxkitty.bsky.social to add a pocket in the front neck for this, so that‘s where the controller and powerbank go!

Controller in action! Me cycling through all the available speeds.

Note there is no „off“ speed, you would just unplug the USB for that. This is to save battery, because then the powerbank can also go to sleep.

Cable to the fan goes through a printed TPU (rubber) strain relief/cable grip that should make this end quite durable as well.