Hi,
I would like to show you my own automatic soda maker machine. It is based on board like Arduino Pro Mini. It's connected to fresh water and CO2 tank. There are five valves and 1,2 liter stainless steel tank. At first, tank is filled by water. When is full, water valves are closed and open CO2 valves. They repeatedly fill tank of CO2 and depressurize. Make of 1,2 liter carbonated water takes about half minute. It is depend on volume of tank, pressure of CO2 and our taste.
There is small menu too. I can fill and empty the tank manually, set number and time of filling of CO2. In second menu I can test all valves separately. There is prepare for cooling system based on peltier elements.
It is my first "invention" based on Arduino... My Arduino code is not soo good, because I have never programmed in C++. I am beginner and I prefer VB.NET. Visual Studio by Microsoft is much better than Arduino IDE...
More information and pictures you can see my website - www.mylms.cz/sodobar. You have to use translate from czech language to your language.
Sorry for my english...