I made a speed controller for some old water pump I found. This project was to learn more about the Atmel SAM line of microcontrollers. These ARM based chips are both cheaper and have more features than the AVR line, but it comes at a cost of complexity. For added fun, this project also used size 0603 SMDs extensively on a hand-soldered board.
This was the first board I etched using home-made and recycleable cupric chloride as an etchant instead of the more common ferric chloride. The soldering was done with low-temp solder paste and hot air.
The 0603 size components were like working with dust. I had to wear a mask so I wouldn’t exhale them off the work table. I lost a few that way but thankfully had ordered extras.
The sharpie gives a sense of scale.