Barbot, the Automated Bartender

What's the perfect drink for a hacker party? Anything, so long as it's mixed by a robot

At NYC Resistor, a communal hacker space in downtown Brooklyn, N.Y., we do two things really well—hack and party. An automated bartender seemed like a natural, but as we searched the U.S. patent database for ideas, it became clear we’d have to hack one up ourselves. And so we have. An ongoing series of them, in fact.

Believe me, we looked. For example, U.S. Patent No. D496657, with the promising title ”electronic bartender,” turned out to be nothing more than a design for a curved flask with a flat LCD display. And while patents 3428218, 3930598, 4278186, 4411351, 4433795, 5731981, and 5913454, for ”beverage dispensing systems,” seem fine for pouring beer, wine, or liquor, none of them is going to mix you, say, a Sazerac (a New Orleans concoction of rye whisky—or absinthe, if you can get it—with bitters that may well be the first cocktail invented in the New World).

Barbot Series v3 is the third incarnation of our own electronic bartender. (Luckily, Barbot’s first two incarnations are documented on NYC Resistor’s wiki, as they are otherwise mere evanescent memories barely discernible through the fuzzy and sticky haze of parties past.) Barbot has been passed from friend to friend at NYC Resistor as an evolving and collaborative project. Raphael Abrams, a 30-year-old freelance designer and electrical engineer, is its current maestro. He pulled together most of the parts from the cabinets that line the walls of our mad-scientist workspace.

hands on
Photos: Bre Pettis

Hacker haven: The heart of an automated bartender is its Geneva drive [bottom right], which divides a continuous rotation into discrete station stops for alcohol, mixers, and bitters; NYC Resistor member Raphael Abrams [top] oversees the Barbot as it mixes the first of many Sazeracs, a classic New Orleans cocktail [bottom left]. Click on image for a larger view.

For the latest version, our normally freewheeling collective laid down one firm rule: no random drink button. Past Barbots had a large and fatally tempting random drink button that, when pressed (despite its bright red warning color), incited the machine to create hangover-inducing drinks containing random combinations of tequila, gin, and vodka.

The brain of Barbot is a configurable Twitchie microcontroller board. The Twitchie, in turn, is based on the Arduino platform, a collection of development tools based on open-source hardware designs and software. Arduino-based devices interact with the world through attached sensors, controllers, motors, and other actuators. As you can see, Arduino is an ideal robot development environment—it is, in fact, crack cocaine for 21st-century hackers.

The Twitchie variant of Arduino has at its heart an Atmega168 chip running the Arduino coding environment and optimized to drive servos. Raphael originally designed the Twitchie to be part of a kit for creating quivering and twitching dolls, but its simplicity, size, and ease of use make it ideal for service as the Barbot’s central brain. With a series of pins that can be brought high and low and use pulse-width modulation—a way of encoding the level of an analog signal digitally to control the amount of power sent to a load—the Twitchie receives input from a control panel and then drives a series of servos, metal-oxide semiconductor field-effect transistors, and a relay to control the Barbot’s arms and liquid-delivery mechanisms.

The control panel is a shifting display of LEDs and antique glass domes with lights that indicate power and status. To initiate drink making, you key a sequence of five buttons (picture unlocking one of those spy-movie doors that sport an encoded door-entry keyboard). Upon the last button push, Barbot Series v3 lurches to life.

The robot starts moving your drink from one filling station to the next so that alcohol, mixers, and bitters can be added in succession. For this it uses a Geneva drive, a mechanism that translates rotary motion from a continuous into an intermittent form. The most common application of a Geneva drive is a motion picture projector, where each frame is advanced and held still for a fraction of a second before moving on to the next. At the first station, a servo-controlled arm swings out and delivers alcohol to the glass in exact measures, through hoses made from 1/4-inch (6-millimeter) tubing, using peristaltic pumps.

A peristaltic pump uses bearings that, when they turn, put revolving pressure on a tube and force liquids onward, the way you’d force toothpaste out of a tube. Peristaltic pumps are commonly used in dialysis machines to transfer blood, because the parts that squeeze the tube never touch the liquid, thus keeping it from being contaminated.

In the next station, the mixers are gravity-fed from the top of the machine and measured with precisely timed 12-volt solenoid valves (driven by n-channel MOSFETS), which let the liquid into the drink. My contribution to the machine is a little bottle attachment that swings out over the glass and sprays homemade bitters into the drink. It uses two servos, one to lower the spray bottle and another to push the spray-bottle cap down with a cam gear.

Development on Barbot Series v3 began on 15 May. By early July, it was time to find some beta testers. In other words, it was time to throw a party. As the preparations at NYC Resistor began, a final check of all the fittings ended in a deluge of rye over the electronics. A short wash in the sink and a pass with a hair dryer brought it back online.

To the thumping sound of 8-bit electronic music, Barbot’s whirring pumps, swinging arms, clicking solenoids, and spraying bitters held partygoers spellbound as they waited for their turn to taste the sweetness of a robot-served Sazerac.

Automation is a form of magic. The spell of watching Barbot is broken only when the machine pushes a glass in your direction and its LEDs wink at you, encouraging you to drink up. A bystander remarks, ”Wow, this is an actual cocktail!”

To Probe Further

Learn more about Barbot Series v3 at http://wiki.nycresistor.com/wiki/Barbot. You can also watch a video of the machine in action at http://www.spectrum.ieee.org/video/robotics/diy/barbot.

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