https://www.youtube.com/watch?v=3g-Vd9gIwZU
DIY Arduino lab bench power supply 0-30v 0-3a cv cc
PART 1: https://www.youtube.com/watch?v=3g-Vd9gIwZU
PART 2: https://www.youtube.com/watch?v=t8EfWlLJVXw
PART 3: https://www.youtube.com/watch?v=3DTpoN7AL14
PART 4: https://www.youtube.com/watch?v=FiBXrJ1YAZQ
This power supply can be built for less than $25 sans enclosure
Code: https://drive.google.com/file/d/0ByGyXp39rbHpZWZXSGd1MllGMXc/view?usp=sharing
Schematic: https://drive.google.com/folderview?id=0ByGyXp39rbHpaGMwWFJXVWdid3c&usp=sharing
Parts List: (see schematic)
http://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.html
https://www.digikey.com/product-detail/en/atmel/ATTINY84A-PU/ATTINY84A-PU-ND/2774082
https://www.digikey.com/product-detail/en/fairchild-semiconductor/LM7805CT/LM7805CT-ND/458698
https://www.digikey.com/product-detail/en/diodes-incorporated/KBP2005G/KBP2005GDI-ND/278620
http://www.banggood.com/1Pc-1602-Character-LCD-Display-Module-Blue-Backlight-p-978160.html
Assorted resistors and capacitors (see schematic)
Optional: (see schematic)
Cool enclosure
Potentiometer knobs
Binding post output
Switches
Leds
Big heatsink for transistors