- Project -
- Overview -
- The Switch -
- The Software -
- Email Me -
Chewie!!!
The Project
Of the many interesting projects I've worked on, "Chewie" is probably one of the most
unique. Chewie is a normal computer tower with a fur(I think it's rabbit fur) coat. The
computer has been modified so that it emits a number of sounds when you pet its outer fur coat.
The Chewie project was the product of the Tech293 and Tech294 classes during the winter and
spring quarter of 2004. The "fuzzy computer" or "pimp computer" was built by a previous
class as a project. I don't know exactly what they used to cover to computer case, but it
appears to have been some sort of rabbit fur. In any case, it was quite soft and pettable.
Rudy(our instructor) decided we should pull the fuzzy computer out of storage and use it as
our new router for the lab. While setting up the fuzzy computer, it was hard not to notice how
irresitibly pettable the computer was. The next thing that came to my mind, naturally, was if
it was possible to make the computer purr when pet.
Overview
The basic layout is pretty simple. At the top of the case there is a simple momentary switch
that is connected to the microphone input on the sound card. The switch can be depressed by a
metal plate approximately 2"x5" in size. This was placed under the fur at the top of the case
for easy access.
After a bit of tinkering, I was able to reliably take samples from the microphone input on
the sound card and detect a change when the switch was depressed. The next step was to automate
this and do something interesting with the input. What developed was a perl daemon that runs
at boot time, reads a configuration file, and plays a random .wav file - which can be customized
via the config file - when someone pets the top of the case and depresses the switch. That's pretty
much it.
This development was an immediate success. Suddenly, "Fuzzy Router" or "Pimp Computer" was no
longer an adequate name to describe this machine, which had taken on an entirely new and
interactive personality. In searching for new animal noises and .wav files to play, one of
the students suggested a "Chewbacca" growl(ie. Star Wars) - hence the new name for this
creature, "Chewie". Currently, Chewie makes purring, roaring, growling, and mooing sounds
when pet.
The Switch
The speaker/microphone cable I used had four leads, two for "data" and two for the positive
and ground wires. I simply connected the positive and ground wires to the switch and taped
up the rest. The theory was that if the switch was depressed a circuit would be created that
would be detected as input to the microphone. I didn't care what the input was, only that
there was some sort of change that would indicate that a switch was pressed.
Eventually, the momentary switch proved to be a little too clunky, so I decided to look for a
switch that was thinner and easier to depress. Ideally what I wanted was a 2"x5"(more or less)
pressure mat type of switch with two leads. But this proved to be more evasive than I had
previously thought. I found tons of momentary/tactile/membrane style switches, but nothing
ready made or quite right for my purpose. I guess these types of things need to be custom made
or something. Instead, I built my own pressure mat switch with a metal plate, a small copper
spring, and an anti-static bag. This switch turned out to be much smoother and easier to
depress.
The Software
Chewie is a Linux box. In particular he is running the Sentry Firewall CD which is based on Slackware Linux. The daemon that controls the switch is written in perl. There's
really not much to the software, really. It uses the Audio::DSP module to constantly take
input samples from the microphone. When an altered signal is detected, a threshold number is
decremented. Once this number reaches zero the function returns success and a .wav file is
then played. The sample rate and buffer size can be altered to make the switch more/less
sensitive. Another threshold exists that causes the input function to time out and restart
its sampling process. This ensures that the button is adequately depressed within a certain
time frame. If it is not depressed for a long enough time the function restarts and the
threshold variables are reset.
Here is the code.
Future Enhancements
The project so far has had a tremendous amount of positive feedback. Most of the students
and faculty are amazed and amused with the concept of a purring/growling computer.
There are several problems, however, with the current implementation of Chewie -
Some possible enhancements include the following:
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