To make this project even more interesting for me, I added something I hadn’t originally planned, and haven’t done before on the SO2: pcb milling. I designed a little board that takes in the 24V from the power supply, and steps down to 12V, 5V and 3.3V DC. Everything I need for the fans, toggle switch LED’s, and eventually limit/home circuitry. I have found there is a 5V and 3.3V out on the arduino, but for some reason I measure nothing on those pins. I may have done something wrong, but I don’t really care as I have everything readily available with this board.

The schematic is very straight forward: I just use regulators and stabilize with capacitors for the 12V and 5V. The last stage I did with three 10K resistors.

Milling was fast and without issues. I took an 0.8 mm (1/32″) endmill and cut the tracks 0.5 mm deep in 1 pass. The board wasn’t even very flat but everything turned out perfectly.

After milling:

 

After soldering:

I measured and everything checked out!