Step 1: Materials
-A 30-32v power adapter. (Mine is salvaged from an old printer)
-A DC-DC buck converter. (1$ on ebay)
-A LED panel voltmeter. (2$ on ebay)
-An audio spring terminal. (0.40$)
-A potentometer, the same value as the one of the converter, mine is 10K (0.60$)
Step 2: No Project Box Needed
I know that kind of power adapters have a lot of empty space inside that we can use to place our components, so i'll open it to se if it can be the project casing.
If you use a transformer with a rectifier circuit, you'll need a different box.
As you can see un the pics, there's enough space for all the components.
Step 3: Electrical Connections
The wiring is pretty easy, you can see it in the diagram.
What you'll need to do first, is replace the small multi-turn potentiometer with the big one, it'll make the voltage controlling easier.
Then connect the voltmeter and the spring terminal in parallel at the converter output.
Step 4: Preparing the Case
Open three holes in the case. one for the voltmeter, other for the terminal and one for the potentiometer.
Then glue them all to the case and cover the connections with tape to avoid short circuit risk.
I didnt have any knob on hand, i recomend you to use one for a better appearance.
Step 5: Final Steps
Now solder the 30v output of the adapter to the converter input and cover it with more tape.
Then close the adapter with everything inside and glue the case with a strong glue as epoxi or cyanocrylate.
Step 6: Ready to Use!
The power supply is ready to power all your projects.
I hope you have enjoyed this instructable.
Feel free to ask me anything you didn't understand or propose upgrades.