Light Your Bot!

In most of our projects, it seems like we always relegate LEDs to the backburner while we focus on everything else. Fortunately, we had the forethought on Bartendro to squeeze the hardware in at the design phase, even though we didn't get to work on the software side for a long while. Good LED effects are undeniable. With good placement and intelligent programming, they can make a product sing. Bartendro is case in point. The LEDs in the back are dual purpose, they light the bot with a silky purple haze for people to enjoy the view of the innards, but the color can be changed to pure white for brighter easier debugging in a perfectly dark room. The ring of RGB LEDs which hover directly over a user's cup serve many purposes. They let us know when the bot has booted and is ready for communication, and they let users know what's going on in the process of their drink creation. A pattern while it pours, and flashing green when the drink is done being poured. When all is said and done, a soft blue lets the user know that the machine is in an idle state and ready to take on more drink orders. There are even more LEDs that aren't powered up yet, which are supposed to emit focused light from the faucet. The intent is that they cue users as to where their cups should be placed. So when working on your projects, make sure to let your LEDs shine!

The Setup

Designing a cocktail dispensing machine may not sound very difficult, but when one considers that most of the components are not readily available for purchase off the shelf, one must design their own. There are a lot of tools that go into creating a complex electro-mechanical machine like a drink bot. There are solid modeling tools, like SolidWorks and Alibre, CAM tools like SprutCam and the software that runs a the CNC machine, like Mach 3. The CNC machine is a PCNC 1100 made by Tormach, and it is a joy to use. All of the tools need to work in unison to achieve the desired results. These tools cover the basics required for machining parts. When it comes to the electronics, schematic and layout tools are required. In my case, I used EagleCAD because of the existing community and pre-made parts that allowed for fast development time. Boards can be cheaply fabricated in China by Golden Phoenix and modules from Sparkfun and Pololu make development even easier and more modular.

All software tools have their quirks, and when it comes down to it, it is just a matter of patience to learn how to use things in an efficient matter. Having these hardware and software tools in place allows us to iterate over and over tuning and refining until we are happy with the quality and performance of our creations. The tool set allows us to also make a wide array of parts, mechanisms and machines that make people's lives easier and more enjoyable. So, get some tools and start creating!

Peristaltic Pumps

Peristaltic Pumps are not new, they are pumps that mimic peristalsis, a biological mechanism most commonly depicted as the muscle contractions of a swallowing esophagus. The vast majority of these pumps serve the medical and pharmaceutical industries. This does not bode well for hobbyists because the pumps are priced at an average of $300 each. When attempting to build a cocktail machine that dispenses over a dozen liquids, the cost becomes prohibitive.

"Why use a peristaltic pump in the first place?", you might be thinking. Well, for many reasons. The first and most obvious reason is maintenance. Since liquid does not pass through any moving parts, it becomes easy to swap out or clean hoses when necessary. In the same vein, reliability. Syrupy liquids like grenadine and Bailey's tend to gum up mechanical pumps and valves pretty quickly. Sanitation then becomes another issue when liquids become trapped in the crevices of a mechanical assembly and become impossible to clean. Finally, accuracy and simplicity are the final components that put the nail in the coffin on other approaches. While gravity valves and simple diaphragm pumps are a possibility, there is still a big issue with dealing with different densities and viscosity of liquids. Since peristaltic pumps are positive displacement, meaning they dispense the exact same amount of volume with every revolution of the motor and gearhead, it simply becomes a software problem to account for the number of motor rotations for accuracy. This is much easier and cheaper than fashioning some sort of flow rate meter.

When designing the pump, several factors need to be taken into account such as the occlusion of the tubing, the ease of assembly/dis-assembly of the tubing, maintainability and modularity. The picture shows the parts for the first batch of peristaltic pumps I made. There is a plate that the motor mounts to, a hub with sleeve bearing rollers, a shoe which is replaceable and provides the right amount of occlusion, and a support for the hub that prevents lateral motions from causing it to run to eccentrically. All in all they can be built for under $100 given the right amount of tools and resources.

Bartendro 2 Frame and Enclosure Build

We built the frame using 1" aluminum square tubing, which seemed to offer the best balance between weight and strength. The individual pieces were cut to length on a milling machine and the edges that were going to be butt or T-joint welded were chamfered to reduce the amount of weld bead that would need to be ground down afterwards. Jerad TIG welded the frame together using his new beefy Bessey corner clamps, it only took him a couple of hours. 

The enclosure itself was made of 16 gauge 304 stainless steel. 12 and 14 gauge were considered at first because less structural members would be needed, but the cost of thick stainless was prohibitive. The 32" overall length emerged from the hassles of transporting the original Bartendro. Two people were required to move the machine, and it could only fit into a sedan that had its passenger seat removed, and still it would gouge chunks out of the interior in the process. The design criteria were simple: fit through a door frame, fit in the trunk of my Honda Accord, and be able to be carried by one person. Getting the sheet metal sheared and bent took about a week to get from the metal workers. Then the stainless steel tee fittings were post-machined and welded to the enclosure. Their precise outer diameters helped maintain a consistent and repeatable weld joint. 

The PVC coating on the sheet metal was really important in ensuring the finished product looked good and wasn't scratched up from the cutting and bending processes. I learned that it is really important to make holes in the stainless steel sheet first before making holes in the aluminum. Aluminum is really soft relatively, and is very easy and forgiving to make holes in later compared to stainless steel. Stainless work hardens quickly, meaning one cannot be timid when making a hole or cutting because it only makes matters worse.

Unfortunately, when the tee fittings were welded in place, the sheet metal warped a little on the narrow stretches, alternating between concave and convex. The additional members that were welded across helped to keep things uniform, but it was the use of panel clamps that made keeping things straight possible. They are quite useful tools, used frequently on auto body work, they allow sheet metal to be held in place yet still allow for minor shifts to help in the alignment process. Once the main panel was lined up, it was secured with  an abundance of clamps. Holes were drilled and tapped into the frame and the panel fastened with shiny button head screws. 

Water to Wine. Sacrilegious fun for all.

Yesterday, Lauren Blomberg and Brian Matis came over to drink wine and help me with a photo shoot for Make magazine. Brian had taken dozens of shots in August '11 of the broken down components and assembly procedure from start to finish. The shots were well lit and well composed. Fancy white photo umbrellas go a long way apparently, when it comes to taking good shots.

The editor at Make recently started working on the article so it can go into their next issue, I believe volume 30. He found that he was missing some action shots though, with wine actually coming out of the machine. When we disassembled the machine for the August shoot, connectors, tubing and wires were cut and it sat that way for a while. Needing to take the action shots was good motivation to put it all back together. I used some new food grade tubing from the local beer brewing supply and put it all back together.

We took dozens of shots in the kitchen while spilling water and wine now and again as we tried to work air out of the lines. After about half an hour of fussing, everything was primed and ready. That's when the silliness began. As we drank more and more wine, we began to become more intimate with the machine. Finally, Lauren thought it would be a good idea to put her mouth up directly to the outlet and consume that miraculous goodness. It was priceless.