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