An adjustable power supply is pretty handy for any electronics or low-voltage electrical work. I made a simple one from a readily-available DC-DC converter board called the DP30V5A-L, rated to 30 volts and 5 amps. I got it for USD $12 from AliExpress.
3D printed case
I made a box for it using the Ultimate Box Maker on Thingiverse and added an acrylic window into it. I 3D-printed it and cut out the window opening with the Dremel. One of these days I’ll figure out how to edit the shape file before printing to do things like that. For now the Dremel did fine.
I needed to extend the little buttons from the circuit board up to the top of the box. I designed a post in FreeCAD which fits over the button. It pokes through the top of the box, and has a lip to keep it from falling out.
I first made a simple cylinder, but it was too fat to fit two side-by-side. I refined it to make it thinner. But then it was too tall. Third time fit right.
This is one of the advantages of 3D printing: the ability to quickly design and try out a part, and then edit and reproduce it again.
I added an old laptop power supply to provide 20V input, using “Dean’s” or “Tee” plugs as a generic DC connector.
The DB30V5A-L board now gives me 0-20V output, with current limiting controlled down to a few milliamps. Great!