Digital and programmable 0-30V/0-3A PWM/R2R Power Supply with AVR Atmega8 in a DIP package on a single sided board. Schematics and software are based on Guido Socher work at tuxgraphics.org
http://www.tuxgraphics.org/electronics/200707/bench-power-supply-unit.shtml
Hardware was designed with Proteus 8 and software with Atmel Studio 7.0
This is an old project build on four hands, me and a intern at our company that has the skill of DIY PCB boards. If you know what copper clad laminate and etching solution, household clothes iron and laser printer can do together, so sure, you know what I am talking about.
Almost all parts came from a waste bucket except for the mcu and some conections pins. Case came from an APS nobreak, toroidal transformer from a thermal printer, LCD from a dispatch indicator etc.
You can view it in action at youtube:
https://www.youtube.com/watch?v=rYz-jPgbcTQ
I am not affiliated with any company or individual cited above. This is a product of free time and has not been intended for profit of any kind.
Use it at your own risk.