12 VDC solenoids mounted to the bottom of the shelf.
The control housing. It takes a 12 VDC 2 A wall adapter to power on. The controls are an on switch (top), an "add a 2 oz shot" button (black), and then two different 6 oz/2 oz mixed beverages with the red buttons. It's PIC 16 controller with simple digital inputs (out push buttons) and digital outputs on delays that correspond in time with the amount of beverage poured.
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pro(of) mixology
Pro(of) Mixology was born of a mechatronics (ME430) project at Rose-Hulman Institute of Technology. My partner Abram Summerfield (Rose '13) and I made it in about a weekend. It's a basic proof of concept for an automatic bartender. It uses a constant-velocity siphon and time delays on solenoid valves to poor accurate amounts.