FIGURE 17. Control the motion of the BeginnerBot by
flipping the position of the two switches. To make the
robot stop, let go of the switches and have them spring
back to their center off position.
alkaline or rechargeable) into the battery holder. Place the
BeginnerBot base on a small book to lift its wheels from the
ground, then try each of the control switches. The motors
should turn as you flip the switches.
Test the operation of the BeginnerBot by putting it on
the floor, motor-side up. With the control panel in your hands
(see Figure 17), press both switches forward. The robot
should move forward. (“Forward” and “backward” are
arbitrary on the BeginnerBot, but for our purposes here, the
back of the base is the end with the skid.)
MAKING ROUNDED BASES
circles by lopping off
more corners from
an octagonal base.
with their corners
as shown in Figure
A. To make these
cuts, mark directly
on the wood or
plastic — you don’t
have to be precise —
to the nearest 1/4”.
Or, use a piece of graph paper lightly glued to the wood. You
can use paper paste — the kind you ate in grade school — or a
non-permanent glue stick.
If you have the proper tools, you can make circular bases
using a circle cutting jig for a power router or jigsaw. The kind
for jigsaws is fairly easy to use, and is the least expensive. It
works just like a beam compass.
Start by drilling a hole in the approximate center of the
wood, then adjust the circle-cutter to one-half the diameter of
the circle you want. For instance, to make a 6” circle, you
adjust the cutter to the 3” mark. You need to also make a
starter hole for the jigsaw blade. Position the hole anywhere
along the circumference of the circle.
Seat the anchor point of the cutting jig inside the center
hole. Starting from the center hole you previously made, cut
out the circle with the saw.
FIGURE A. Optional: Make even more
rounded bases by lopping off the eight
corners of an octagonal base.
52 SERVO 08.2011
If instead the robot moves backward, loosen the nuts on
the switches and rotate both 180 degrees. Retighten the
switch nuts. If the robot turns in a circle, loosen the nut on
the switch controlling the motor that’s going in the wrong
direction. Rotate the switch 180 degrees, then retighten the
nut. If the right and left switches control the wrong motor,
flip the control panel around. Or, remove both switches,
reverse their position on the panel, and put them back in.
Place the BeginnerBot in the center of the room. Practice
steering the robot around the floor. You’ll note that tight,
spinning turns are performed by pulling back one switch
while the other is pushed forward. A slower “pivoting” turn is
accomplished by releasing one of the switches (depowering
its motor) and letting the other motor continue. Have your
BeginnerBot move toward a corner in the room, then see
what kinds of motor control actions are needed to reverse its
direction so it doesn’t get trapped. The techniques you
discover here are the same ones you’ll use when the
BeginnerBot is under automated electronic control (which will
be covered later).
Next Phase: Electronic Control
So, now you’ve been introduced to the BeginnerBot. If
you’ve followed along, you’ve constructed your bot, wired
everything together, and tried it out in front of the family cat.
You’re now ready to move to Phase 2 which is converting the
entry-level BeginnerBot from manual switch control to
In the next part, you’ll discover how to use rudimentary
circuitry to give your BeginnerBot the sense of touch. It’ll
detect obstacles — even your friendly feline — and
automatically steer around whatever doesn’t get out of its
1 6” x 6” piece of 1/4” thick aircraft-grade plywood or
1/4” ( 6 mm) expanded PVC plastic
1 6-1/2” x 4-1/2” piece of 1/8” thick aircraft-grade
plywood, acrylic plastic, or picture frame mat board
2 Tamiya #70093 three-speed crank axle gearbox
1 (pair) Tamiya #70096 off-road tires
4 4-40 x 7/16” pan or flat head machine screws
4 4-40 nuts
3 6-32 x 1/2” pan head machine screws
4 6-32 x 1” pan head machine screws
8 6-32 nuts
4 6-32 acorn nuts
2 1/4” cable management clips
2 DPDT center off momentary bat handle miniature
toggle switches (for 1/4” mounting hole, threaded
bushing, with nut)
1 Three-cell ( 4. 5 volt) AA battery holder
Misc. 24 or 26 gauge stranded hookup wire, eight or 10
foot length of four-conductor modular telephone
A kit of mechanical parts consisting of a precut and
predrilled base and control board, and all assembly
hardware is available from Budget Robotics,
www.budgetrobotics.com. See the Sources box for a
selected list of where to find other parts used in the
BeginnerBot. Gordon may be reached at rbb@robotoid.