Can deliver up to 5V. Low cost so it can be build for/by beginners. Easy to build.
For powering it up you connect it to USB adapter. You can controll voltage on output by rotating potentiometer. Arduino calculates voltage and ampers(in miliamps) on output. Mini variable supply has got a short circuit protection so you cannot short your arduino. When you make short circuit LED turns on and one of transistors starts to worm up(over 70°C) so you need to be careful and turn off output switch.
It uses: arduino uno, lcd(16, 2), 2x potenciometers, 2x transistors (npn), LED, resistors and 2x switches.
Included diagram and arduino code.
If you try to make this please share with me what you think about it(on mail).
If you have some questions or issues send them to my email.
my mail: email@example.com