59 lines
4.2 KiB
YAML
59 lines
4.2 KiB
YAML
date: 2009-06-21
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title: Intelligent Drink Dispenser Details
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---
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I said that I'd post details on my Intelligent Drink Dispenser project "soon". That
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was over a month ago. Whoops. I blame my [new internship](http://nucoryamato.com/) for that.
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For those of you not in the know, the Intelligent Drink Dispenser was my senior design
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project at Missouri University of Science and Technology (which will forever in my heart
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be University of Missouri-Rolla). It's basically a smart drink dispenser that's capable
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of mixing, charging customers, telling the bar/restaurant owner when they need to refill
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the machine, etc.
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---
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If you don't feel like reading the details and just want to look at the pretty pictures,
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you can check out my [Picasa album](http://picasaweb.google.com/nick.pegg/IntelligentDrinkDispenser)
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or watch the [Youtube video](http://www.youtube.com/watch?v=79H5oAS_Y6k).
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The theoretical process is that the customer would go to order a drink, and since they're
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a new customer, they'd have to be entered into the system by the person running the machine
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(bartender, or waiting staff). They would have their name and credit card information taken,
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and would then be assigned a drinking vessel based on the first drink they were wanting to
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order. Multiple vessels could also be assigned to the same person. Once the customer is
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setup and is ready to purchase their drink, they set the fluid vessel on the marked reader
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area on the dispenser. The system then recognizes the vessel, who it belongs to, asks the
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customer for the last four digits of their credit card, and then asks the customer which
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drink they'd like to order. The customer then chooses what drink they'd like to have, the
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system double-checks that the vessel is the right size, and pours it.
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Security and privacy was one of the major goals of the project. The only information stored
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about the user is their name, a secure hash of their credit card number, the last four digits
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of ther card, and their drink order history.
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The project itself can pretty much be split into two major components: hardware and software.
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I would probably say the hardware is more interesting and posed more challenges for us. The
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first thing is how the heck do you pour the fluid? If you take into consideration that we only
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had a $300 budget for the whole shebang, it's not an easy task. The way that the professionals
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do it is with Carbon Dioxide-powered pumps, which are controlled by electronic valves and supplied
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by a tank and pressure regulator. Three pumps, valves, and the feed system would cost us well
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over $300. Our original idea was to use 24 VDC sprinkler valves, but that idea failed because the
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sprinkler valves by their nature require back-pressure to operate. We came up with the idea of using
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windshield washer pumps made for cars. Since this was supposed to be a prototype, we didn't have to
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worry about our components being food-grade. That, coupled with the fact that the pumps operate on
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12V DC and are relatively inexpensive ($15-25 a pop), that's what we went with for our design.
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The rest of the hardware design was fairly straightfoward. We used an 8051 microcontroller to control
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everything, an FTDI UM232 to handle the PC communications and a Parallax RFID reader to read the
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tags that are on the bottom of the drinking vessels. The serial communication is pretty interesting
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since the USB-to-serial device has only one serial port but two devices to talk to (the RFID reader,
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and the PC). Our solution was to have the receive line go to the RFID reader (to the PC), and have
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the transmit line go to the 8051 (from the PC). This meant that our 8051 couldn't talk back, so we
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had to hope that things were working right. Additionally, Richard developed a simple serial language
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for the 8051. If the 8051 received an ASCII 0 through 7, it would turn on that pin on the port we
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were using. This could easily be modified to operate with all the ports on the 8051 to control 24
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pumps, or even with some addressing logic to control a huge number of pumps.
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Below is our hardware schematic, which should give you some idea of how it's all connected.
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In my next post, I'll be talking about the software design. Stay tuned!
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