FIGURE 5. By controlling
the servo motors, the
robot can be made to
travel in straight lines or
make turns. By reversing
the motors relative to one
another, the robot will
spin in place.
FIGURE 6. Each
attaches to the
bottom base of
the ArdBot II
with a pair of
44 SERVO 08.2013
FIGURE 7. The ArdBot II bottom base showing mounted
servo motors. Note the orientation of the motor shafts
relative to the front of the robot (the front is pointing left).
Making Your Own Deck Risers
The ArdBot II uses risers — also called standoffs — to
separate the top and bottom decks. Long ( 2" or more) standoffs
for the deck risers can be hard to find and expensive. Full retail
for each standoff may cost a dollar or more, and you need four
of them. Options include screwing together shorter standoffs or
use long 6-32 machine screws and nuts, along with aquarium
tubing as spacers.
A 3" machine screw will provide a riser length of about 2",
which is perfect. You need to allow for the thickness of the two
body pieces (about 1/2" total), plus another 3/8" or so for
securing the nuts. To use this method, thread the screws up
from the bottom, and attach the precut lengths of tubing.
Lightly compress the tubing by hand-tightening a nut over it.
Do the same for all four risers. When it's time to attach the top
deck, position it over the machine screws and secure with four
more nuts. Hand tighten only.
parts in upcoming installments as they are described and
Assembling Your Robot
With the body pieces constructed (or purchased) and
all other parts in hand, you’re ready to build your ArdBot II.
Note that not all of the components listed are used in this
first article. Some (like the piezo speaker and switches) are
explained in more detail in upcoming articles in the series.
Before assembly, you may want to use 150 grit
sandpaper to smooth the edges of the base parts.
Orient the bottom deck so that the holes are aligned
as shown in Figure 3. Note that the holes for each servo
are not symmetrically placed on the deck. This is to
accommodate the offset of the servo drive shaft. While
there is technically no “front” or “rear” of the ArdBot II,
for the purposes of assembly, the top of the illustration in
Figure 3 is the front, and the bottom is the rear.
Insert a servo into a servo mount by sliding it back-end
first through the mount. The fit may be tight, depending on
the make and model of the servo. (As necessary, enlarge
the rectangle for the servo using a file or coarse
sandpaper.) Do not force the servo into the mount, or the
mount may be damaged.
Secure the servo to the mount with 4-40 x 1/2” screws
and hex nuts (Figure 5). You can use either four screws for
each servo or only two. When using two screws, position
them on opposite corners of the servo mounting flange as
Repeat for the opposite servo and mount. Be sure to
construct the second servo and mount in mirror-image to
the first! Refer to Figure 7 in Step 3 to see how the motors
should be inserted into the mounts.
Using 4-40 x 1/2” machine screws and nuts, attach
two plastic L brackets to each of the servo mounts. You’ll
make a “left” and a “right” mount assembly.