Version 5.22, centrifugal fan model
This uses the same firmware as the 5.0 model, for now, I will improve and change it later. I will put the improved firmware here.
There are documents that discuss the design and assembly of the unit on the website, openerv.org.
You can buy a kit of parts on tindie.
A file with printing tips is in the docs section of the website (google docs).
The schematic is an image, included. The reset pin indicated on the stepper driver is actually the UART pin of the TMC2209.
I should really combine everything into a single repository, and I will over the long term, I keep waiting till things stabilize a bit.