COMPONENTS

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HARDWARE AND MECHANICAL DESIGN

The structural design of The Alcotron consists of three plexiglass disks that are held in place by four aluminum bars to create support platforms. The disks are 14 inches in diameter and 1/2-inch in thickness. The bars have an initial diameter of 3/4-inch and are stepped down at each support level by increments of 1/4-inch. This change in diameter creates a "shelf" for the disks to rest on. The diameter is also stepped down to 1/2-inch at the bottom of the bars, where they are secured into the base by counter-sink screws. The base supports the turntable, which has a rotary encoder embedded into its center. The turntable has a non-slip surface to keep the cocktail glass stable and in the proper position. A 12-Volt DC motor is secured to one of the bars and has a large, frictional rubber disk attached to its shaft that makes contact with the turntable. When the computer code actuates the motor, the rubber disk spins, turning the turntable until the glass is at the desired position. At this point, the rotary encoder senses the cup's position and tells the computer to stop the motor. This prototypical version of the automatic bartender holds four bottles, which are arranges with circular symmetry. The bottles are suspended upside-down, with the mouths of the bottles securely fit into holes in the middle disk. Large holes in the top disk support the sides of the bottle, keeping them vertical. Four 24-V solenoid valves are mounted to the bottom side of the middle disk, where they are linked to the bottles through hose barbs that pierce the bottle caps. When the glass is under the appropriate valve, the computer sends a voltage through a relay to the valve for a set amount of time, which opens the valve long enough to pour the proper amount of liquid into the glass. See pictures of The Alcotron.

CONTROLS

Our device is controlled by a Technosoft MSK243 board that runs off of a 5V (+/- 10%) power supply. We accessed the board via a program called DMC (Digital Motion Control) Developer Pro on a host PC. We then wrote our program in DMC Developer Pro in the C language.

Schematic and photograph of the Technosoft MSK243 Board

The software we wrote has four main functions: (1) to read two switches, (2) to read the position of the encoder, (3) to turn on the motor, and (4) to open or close the valves as needed via the relays. First, the program initializes variables and starts a clock for the timing of the valve. Then, the software waits for one of the two switches (indicating which drink the operator chooses) to be pressed. Depending on which of the two switches is pressed, the program then sets the variables determining how far to turn the turntable, and thus the glass, (i.e. the bottle position), and how long to turn on the valves once the glass is in position. After a button is pressed, the motor spins the turntable until the rotary encoder registers that the turntable (and thus the glass) is in the correct position--underneath the appropriate bottle of the first ingredient of the drink. Next, the valve is switched open for a predetermined amount of time corresponding to a specific amount of fluid. When the valve is switched back off, the motor engages the turntable again and rotates the glass to the bottle of the next ingredient. Once again, the valve is powered open, allowing fluid to fill the glass. When all of the ingredients are added to the drink, the motor spins the turntable until the glass is back at its initial position and the beverage is ready for consumption. At this point, the software loops back to the beginning and waits for one of the switches to be pressed again. Click here for a flowchart of the code.