It was "let's get technical" at the third monthly meeting of the new
Pittsburgh Robotics Society, held April 2.  The arcana of
analog-to-digital converters and mouse maze races held sway as we
welcomed new members, munched on free muffins, and enjoyed robotic
chit-chat.

Mike Timko once again brought his amazing one-cubic-inch nanobot, this
time clothed in a perforated metallic skin of repurposed PC speaker
grille.  It's working great - reacting instantly to rude fingers in
its path (with what I imagine as a peeved expression on its stern,
sensor-studded "face"). When Mike mentioned difficulties creating an
onboard low-battery monitor for the bot, a tech advice pile-on ensued,
with several members lending their know-how.

Should the monitor's analog-to-digital converter get its reference
voltage from the battery, or a separate precision bandgap reference?
Should the monitored input voltage be tapped off through a voltage
divider?  What resistor values to use in the divider?  Is the input
impedance of the ADC something to consider?  Is noise a factor?  If
so, should it be bypassed with a capacitor, filtered out by averaging
successive readings, or mitigated using the microcontroller's
sleep-like noise-reduction mode?  Which bits in the ATMega8 uC control
the ADC?  And how the heck do you set, reset, and read those bits in C
code, anyway?

Bob Nansel, always a fount of robotic wizardry, gave an impromptu
tutorial on the internal workings of ADCs, clearing up confusion over
why the battery won't work as the reference voltage if the battery is
what's being monitored.  Newcomer Mike King was another major
contributor to the discussion.  Bringing embedded control experience,
Mike adds to our club's engineer count.  He'll be another great
resource for club members needing some expertise in taming their
little monsters!

Mike T. also showed off a prized personal possession - one of the
Alice nanobots built by the Swiss Federal Institute of Technology for
research on robot swarms.  Powered by watch stepper motors custom made
by Swatch, it's even more lilliputian than Mike's nanobot - about the
size of a sugar cube. 

The Robot Demo Corollary to Murphy's Law, an old acquaintance, made an
appearance - Mike's infra-red-based remote for controlling Alice
manually didn't work (although, "it works at home!").  Alice was
apparently allergic to the library's fluorescent lights.

First-time attendee Mary Bates brought questions about getting
started, along with her copy of "The Ultimate Palm Robot."  Hoping to
build that book's bot, she got answers on where to buy parts,
reassurance about soldering, and some pointers on other intros to the
hobby.

Our club exhibit for this fall's SciTech Spectacular at the Carnegie
Science Center is making progress.  I delivered the plywood bases for
the two mouse maze races to Dan, and both Dan and Bob Nansel had good
ideas on how to make the mazes adjustable (giving credit where due,
Dan's idea originated with his young son!).  Bob Greene will create a
video loop of robot clips to run continuously in the booth.  He also
volunteered to assemble the second sumobot kit, donated by Parallax.
Dan showed off the control console he built for the human-controlled
mouse.  In the true spirit of amateur robotics, he incorporated the
salvaged console from an old video arcade game, complete with
joystick.  I can hardly wait to see how the buttons picturing masked
bandits get integrated into the plan!

One cool idea discussed was selling our own kit for building the maze
mice.  Bob N. suggested using his BreadBot design, featured in his
early Nuts & Volts columns.  We mulled over issues of size
modification, low cost, programming, and which microcontroller to use.

Pick your ped - biped, quadruped, and hexaped walkers were all seen in
"Dan's Robot Menagerie, Part Deux", a continuation of his video
presentation from last month.  Particularly smile-inducing was a clip
showing a gaggle of giggling teenagers having a grand old time pitting
their sumos together.

Hey, we must be official now - we've got a treasurer!  Mike Timko took
the role, and our money, too!  Can't complain, though - $20 yearly
dues (for adults) is a bargain for all the fun we're having.

I'll mention one other experience I had the morning of our meeting.
After checking out robotics projects (an autonomous helicopter, and a
study of motor driver circuitry) at the Pittsburgh science fair, held
at Heinz Field, I wandered next door to the Carnegie Science Center,
and quickly got snagged by the guys at the amateur rocketry booth.
When I mentioned my interest in robotics, I was told about a group
working on launching their own miniature rovers!  Can you picture a
sleek, meter-long rocket gently parachuting to a touchdown a few
thousand feet downrange of launch, popping open, and a
nanobot-inspired rover crawling out, carrying a tiny video camera and
transmitter?  Could a future collaboration with the Pittsburgh
rocketry club be in store?

Jeff Rice
Morgantown

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