Roboni-i’s inversion would be a fine analog to the
Skinner box, and we could program an unpleasant
response to coincide with the inversion. We could
program the Roboni-i to shiver upon activation of
the sensor (kind of like a rat on Skinner’s
So, what kind of device would we want to
use? We played with the idea of a mercury switch,
but that seemed ill-suited to a bot that targeted a
younger demographic. A gravity switch would be a
much safer way to go, and it would be easy
enough to make from scratch.
Getting Our Bearings
Our plan was to use a ball bearing in a
cylinder that would roll to the other end when the
Roboni-i flipped over, thus completing a circuit
between two wire ends. Technically, that would be
all we needed for a bare bones circuit, but where’s
the fun in that? We wanted to include an LED in
the circuit for cool factor as a debugging tool. As
we constructed the circuit on the breadboard, the
LED would be a convenient way to check that the
switch was working, and it would also provide for
a more multisensory reaction when Roboni-i
engaged in the unconditioned behavior of flipping
over. The circuit was still devilishly simple, of
course, because in addition to the LED we would
just need a pull-down resistor to eliminate floating
voltages. We sketched out the circuit and began
gathering the supplies.
We were hoping to find some ball bearings
for sale at our local home improvement store, but
our search was fruitless. Thankfully during the
heyday of Robot Central, we had acquired a
multitude of useful parts, and bearings were part
of our collection. Liberating the balls from the
bearing, however, would require some finesse.
CUTTING OPEN THE BEARING.
Our preferred form of finesse was to use a
radial cutting wheel, and we were sure to don
our safety glasses before letting the sparks fly.
We cut through the outer casing of the
bearing and we took care to penetrate only the
outer layer to avoid scuffing up the balls. Even
after cutting the casing we had to use a
screwdriver to pry the bearing apart, and we
were cautious in our application of force to
ensure that our fears of flying ball bearings
were not realized.
We needed a cylinder to encase the ball
bearing, and a straw happened to be the perfect
size. It might have been too perfect, however. We
wanted the ball bearing to complete a circuit
when the robot inverted, so we had two wire
ends poke through the sides of the straw. The
tolerance was so tight though that even the
slightest touch from one wire would stop the ball
in its tracks. We needed the ball bearing to
contact both wires, so we had to find a cylinder
that had a slightly larger diameter.
We noticed the cap on the pen that we used
to draw our circuit diagram. A quick snip with the
flush cuts eliminated the extra plastic, and we had
a perfect cylinder already sealed on one end. Also
useful was the fact that the more rigid plastic of
the pen cap was much less prone to squishing and
deformation than the flimsy straw.
To determine what kind of connector we
needed to attach to our circuit, we needed to take
a look inside the Roboni-i. We have to admit, we
approached this task with a hint of trepidation.
Many robot kits are designed to be hacked and
are correspondingly easy to crack open. However,
many bots that are targeted to a younger
RESULTS OF THE DISSECTION.
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