The ShapeOko stepper motors run on 24 volts DC.
It’s advisable (pretty much required) to run a fan to cool the driver chips.
Most fans require 12 volts.
The Arduino runs on 5 volts. It’s powered by the USB port usually.
However I have some optical limit switches that I want to use, and they require 5 volts. I could pull the voltage off the Arduino board, but I might be reaching the limits of the USB power and there might be some other noise related issues.
So I dug around in my parts box and found a 7805 5 volt regulator and a 7812 12 volt regulator. A couple of hours later I had this:
24 volts goes in, 12 and 5 volts come out. The regulators are rated to 1.5 amps, but I’m pretty sure I’ll never pull that out of them.
I’m not going to show you the bottom of the board, since I’m not proud of the wiring job, but it works. No smoke came out, and that’s what’s important.
Edited to add: Well, after reading the Arduino spec sheet it appears that the recommended input voltage is 7-12 volts if you are using the external power jack. I guess I’ll be using the 12v side of my board for that. And I can pull the 5v for the limit switches off the Arduino board too. Hmm. Oh well, not the first time I did a little extra work.