I’m building a bartending robot (or barbot) and this is my first really large project that I’m designing from scratch. I’m learning a LOT in the process of researching methods and parts, and I’d like to share some of what I’ve learned with you. I have a few things that I want from my setup; I want to make this as low cost as possible, I want people to be able to replicate this project who are on a budget. The device should be able to use 6 bottles at once, but this should be expandable. It also needs to be relatively quick, I don’t want to have to wait for a full minute for the device to give me my drink. I’ve seen a few out there that are quite slow..
For actually driving the device I’ve opted to use a Raspberry Pi, its low cost, supports a full desktop environment, has gpio pins and can handle wifi. I know there are other options but I already have a Raspberry Pi. Depending on what I’ll be using to pump the liquid, I’ll probably have to set up some relays to power the pumps because you can’t really get that kind of power from a R-Pi.
Moving liquids accurately presents some interesting problems. I’ve found a number of possible methods that I’ll outline below:
The first method I found that looks like it would probably work best is to use a peristaltic pump, they work by rotating rollers against a backstop squeezing liquid through a tube (as illustrated). They are extremely precise, and can work with relatively low volumes. The major drawback with
them is that they are expensive. After a LOT of looking around, the lowest price I could find for 6 pumps is over $250 after shipping. If you have the money then I’d recommend them but I just cant justify that much for a few pumps.
I had a look around for pump designs that I can print on my 3d printer and found quite a few designs on thingiverse. There is one version that is extremely simple to print and run that I would like to test (see below). It does look like it might be a bit slow however. There are designs for rotating peristaltic pumps to but there are some issues with tolerances that might need to be worked out. Unfortunately my makerbot cupcake 3d printer has destroyed itself again and I need to rebuild the hot end before I can test these designs.
These pumps look extremely promising, they work by moving a diaphragm up and down and using valves to control the direction of flow in the pump chamber. They are extremely low cost, and I’ve found a few food safe ones that would work quite well that cost as low as $2 each, unfortunately the only ones that fit my needs that I can find for sale only come in lots of 1000…. I don’t need 1000 pumps.. I’ll keep looking and maybe I’ll find some that I can buy.
It has been recommended that I try a gravity feed system. This would work by inverting the bottles and using an actuated valve to release measured amounts of liquid. I’m a little weary of this method because it seems like it would be quite touchy. Different alcohols and liqueurs will flow out at different rates because they have different viscosity. You can get around that by having a rain gauge style device under each bottle that fills to a predetermined amount, dumps the liquid and signals the valve to close via a momentary switch, but I feel that this would make the system overly complex with too many moving parts.
The final method I’ve seen is to use low pressure (just a few psi) to pressurize the bottles to force liquid out. There are two ways of doing this:
You can pump specific amounts of air into the bottle you want to dispense, the air would force out the liquid. The problem with this method is that air compresses more than liquid so you would get less liquid at the end of the bottle than you would at the start… Ive never worked with pressurized systems before and am unsure how big the discrepancy would be, so this may not be a big deal.
The other way is to keep all the bottles pressurized at all times via a pressure regulator and then use an actuated valve to release liquid on demand. I actually like this method quite a bit, but am unsure how low the cost of the air compressor, pressure regulator and actuated valves would be. I had a quick look and it appears that just one actuated valve would cost around $20… There may be other cheaper methods of releasing the liquid however..
I obviously have a long way to go considering I haven’t even settled on a method of moving the liquid, and I would really appreciate any feedback that anyone might have. Have you or are you planning on building a barbot? What methods are you using? Know where to find low cost parts? Let me know in the comments below!
So I’m going to start posting on the blog again. It’s been quite a long time now. I have quite a few projects that I’d like to document on the site. I finally picked up a raspberry pi and am quite impressed by its capabilities. I’m putting together a wearable computer using a hacked myvu crystal display with the raspberry pi. I also plan on using the raspberry pi to drive a bar tending bot. I’ll be testing and documenting a variety of 3d printed pumps to see what works best for moving alcoholic drinks around. I also plan on hacking my roomba to provide a mobile base which I may end up mounting the bar tending bot on. So stay tuned in the coming weeks, there is some interesting stuff coming up.
There has been a new computer system making its way around the tech sites lately, the Raspberry Pi. It is a small computer about the size of a business card. It runs Linux on an ARM processor. It has a usb port, handles full 1080p HDMI and composite video, it has a 3.5mm audio jack, it uses an sd card for storage and will only cost about $25 dollars. They have already shown a tech demo of one playing quake 3. This little machine has some punch for something this size and price, it would be almost impossible to find anything with these capabilities for under 200$ right now. It runs off of 1 watt of power and should be able to be powered by 4 AA batteries. This is almost exactly what Ive been waiting for to implement a decent wearable computer system. They should be out by the end of november.
Today I saw the most impressive augmented reality application I’ve ever encountered. It really brings to mind the quote “Any sufficiently advanced technology is indistinguishable from magic.”
A company called Quest Visual has created an application for the iPhone called World Lens, it uses a combination of optical character recognition, real time translation and augmented reality. You load it up on your phone, point your camera at some text in a foreign language (currently only works between spanish and english), and it will translate and replace the text on the real world object in real time. For example, if you point your camera at a sign that says ‘Peligro’, the sign will appear to say ‘Danger’ when looking at it via your phone’s display. More languages are currently being added to the software.
Brother, the company famous for it’s printers has been developing a wearable retinal imaging display since 2005 and will be releasing a consumer version of the display by the end of the 2010 fiscal year (March 2011). They have unveiled a number of prototypes, and will be showing a brand new prototype at “Brother World JAPAN 2010″ on September 15th of this year.
The device will be called the AiRScouter and will work by focusing light, of an intensity harmless to the eye, onto the retina. It will then move the light at high speed to create an after image. Images projected onto the retina appear as if they float mid-air in front of the user. The AiRScouter will initially have a resolution of 800 x 600. Brother plans on offering an attachable camera for possible augmented reality applications.
What makes this display so much different from any other wearable display (or head mounted display) is that there is no physical screen, it actually creates a virtual screen that is transparent, allowing you to use this in your daily life without obstructing your vision. If you are having trouble visualizing this, picture what the terminator sees in the movie of the same name.
There is no word on pricing at this point, so let’s hope that it will actually be affordable.
We finally finish the construction of the makerbot cupcake in this video by securing the plastruder assembly to the build platform. I will also cover initial x, y and z stage calibration. Much more calibration will be required in the future, but this will get everything ready for your first print (hopefully).
In this video I make the final connections and then do a test extrusion.
In this video we will be making all of the main electrical connections on the motherboard, stepper motors and the stepper controllers.
This is the build process for the extruder of the Makerbot Cupcake.