so they would not bind when trying to slide along
the main tracks.
I made two brackets to attach the ¼" carriage
track rod to the square tubing of the carriage
frame and slipped on a matching internal-diameter
linear bearing from Skycraft to hold the stylus.
With the carriage completely assembled and
sliding along the main track, the Scribbler Bot’s
framework was complete.
I looked at the ordinary plastic straw in my soda
and realized it was the same diameter as the
inside diameter of the sprocket, so I stuck it into
the sprocket, cut it off, and filled it with JB Weld.
Once it cured, I drilled a new, smaller hole in the
center, which fit over the motor shaft perfectly.
Finally, it was time to hook up the controller
board and start testing. I soldered motor wires to
terminals on the controller board and, after some
trial and error, got everything to work. Since then,
the Scribbler Bot has drawn dozens of portraits,
including many at last year’s TED conference
in Monterey, Calif. (
ted.com). Meanwhile, I have
improved things by putting all of its electronics into
a detachable project box that the control board and
motors can easily plug into.
Attaching the Motors and Pulleys
The stepper motors use pulleys and belts to move
the carriage and stylus into position. Getting the
carriage to move along the main tracks (x-axis)
is the heavier problem; the tracks are far enough
apart that the carriage needs to be pulled along
both sides. I decided to use an axle to connect
two pulleys on the side opposite the motor. The
force would transmit in a “C” shape starting
from the motor: motor to belt, to pulley, to axle,
to opposite pulley, to opposite belt.
I used a ¼" automotive timing belt for the belts
on both sides. For the first three points in the
drivetrain, the motor and the two pulleys on the
axle, I attached sprockets to mesh with the belts;
the last point in the drivetrain is just a smooth
drum. I attached all 3 pulleys to spin on bearings
from an old skateboard. For the axle, I used
more ¼" aluminum rod.
I mounted the x-axis motor and the last pulley
onto the baseboard using some shelving brackets
and random bolts. For the pulleys on the axle, on
the opposite end of the main tracks, I fabricated
custom brackets to attach them to the board.
The belts travel directly over the main tracks and
attach to the carriage frame underneath, in order
to pull it along. To make this connection, I drilled
holes through the underside of each belt and
the top of the carriage frame, and secured them
together with small bolts.
The carriage uses just 1 belt to move the stylus.
I mounted the y-axis motor on one side of the
carriage and a pulley on the other. I attached a
sprocket onto the motor shaft using my plastic-straw trick (described next) and fitted more ¼"
timing belt around the motor and pulley.
With both motors, I ran into a problem attaching Douglas McDonald is a multimedia developer from
the sprockets to the motor shafts. I couldn’t find Orlando, Fla., who enjoys working on art robotics in his
sprockets that matched the belts and had the spare time. For more information on his projects, please
right internal diameter to fit over the motor shaft. visit
tek-tonic.com.
Future Directions
The Scribbler projects are constantly evolving. I
am currently working on a web version that will
allow users to scribble images and watch them
be drawn on the Scribbler Bot via webcam online.
Also in the works is a wireless sidewalk-chalk bot
that will drive around and draw images based on
input from users over the internet.
The Scribbler
The Scribbler Bot’s software derives from an online drawing toy called the Scribbler (
zefrank.com/
scribbler), written in Flash by Ze Frank. Since the
Scribbler, Ze and I have collaborated on other
projects based on its algorithms, which generate
complex line drawings out of any image.
With Scribbler Bot, we wanted a machine that
creates keepsake drawings of people’s faces quickly
and recognizably, while maintaining a sense of
originality and surprise. “Analog distortions” from
motor vibrations, broken pencil lead, and other
causes are part of the fun. For the Bot version, I
ported the original Flash code to Director, for better
speed, motor control, and camera integration.
The Scribbler was influenced by the artbot
scene (
artbots.org). For more information on the
Scribbler project, please visit
lotsofwires.com.
