One problem with the cocktail robot genre is — at least until recently — everyone’s trying to make money off these devices so no one is willing to go open source. Well, trust our friends the Evil Mad Scientists (Lenore and Windell) to do it right. Their beautiful Drink Making Unit pumps liquids from three different carafes, somewhat limiting their drink options but still serving as a great starting point.
How *do* you build a drink-mixing robot? We spent a remarkably long period of time looking for true food-safe valves and pumps to use for this project. The “standard” way to do this is to use solenoid-controlled valves, or sometimes compressed-air powered valves, but the solenoid valves are notoriously unreliable and we aren’t planning to keep compressed air (or CO2) around. The other obviously safe way to transport liquid in a known food-safe environment is to use a peristaltic pump. These are great, but we felt a little silly either making our own from scratch or paying about $100 each for commercial units that barely move milliliters per minute. We also looked at various diaphragm pumps, aquarium pumps, and so on, but mostly came up with products that were either expensive or of questionable construction for use with food, or gave completely uncontrolled throughput volume.
Finally, after making some progress on a design consisting in part of ketchup bottles and servo motors, we came across an unexpected solution while browsing eBay for other pump types: breast pumps.