Nick Johnson’s barbot project has a lot of fun little details, like the laser cut pinch valves he uploaded to Thingiverse. Nick used an Android ADK board to talk to a tablet which provides the drink menu. I love how he solved the problem of dispensing liquids while keeping them food-safe.
One problem with any drink-dispensing machine is the difficulty of sourcing parts for interacting with food liquids. Pumps are expensive or impractical, valves are likewise problematic and difficult to obtain. My original intention was to use syringe pumps – effectively a DC motor hooked up to a threaded rod that pushes a syringe plunger in and out – and that was the reason behind my making the motor driver shield I wrote about previously. Unfortunately, syringe pumps turned out to be too fiddly and unreliable to use for the barbot, so I had to look for an alternate solution.
I ended up using a similar approach to that used by the DMU2.0, employing a battery powered aquarium pump to pressurize the bottles. For the outlet, however, I’ve taken an entirely different approach, and designed and fabricated my own laser cut pinch valve design. Pinch valves are handy because they don’t require interrupting the tubing through which the liquid flows, and hence they’re perfectly foodsafe.