wheel motor so that it is going at the
correct speed. Connecting the wheel
motors, controllers, and battery together is
the humble power distribution system
(Figure 4). It’s easy to allow these wires to
become a rat’s nest, but a few zip ties and
you’ll have nice tidy sets of wires. Keeping
everything organized will help
troubleshooting and prevent wires from
being caught and pulled (Figure 5).
Connecting the Base
with the Manipulator
The manipulator (Figure 6) might look
familiar to you, especially if you’ve spent
any time searching the Web for robot parts.
I followed the basic design of Lynxmotion’s
AL5D arm kit. I especially liked this
manipulator because it is a well thought out
design and uses a custom plastic injected base that is
designed for use with a servo. Just like wheel motors,
manipulators get exponentially more expensive the
larger they are. Your manipulator’s performance will
be the results of its size, components (servo strength),
and the way you use it. Remember, your manipulator
is like your own arm. It’s easier to lift if the object is
closer to the base.
The Controller's Mini Arm
The controller’s miniature arm uses variable rotary
resistors to provide positional feedback. Each joint
consists of one of these resistors that are also called
potentiometers or “pots.” The miniature arm is fairly
delicate because each joint is made up of just the
potentiometer and is not reinforced at all (Figure 7).
You can see in the photo that the potentiometer’s
collar nut is used to attach it to one side of the joint,
then a small bolt goes through a hole drilled in the
shaft and into the other side of
This design was fine for my
limited use, but I would
definitely recommend using
reinforced joints if anyone other
than you is going to use it. I put
a piece of Plexiglass between
the base of the arm and the
board holding the control board
to reduce friction. The gripper
of the manipulator is controlled
with a natural pinching motion
and the help of a tension spring
(Figures 8 and 9).
SERVO 04.2014 49
Figure 6. Nuntius
Figure 7. Base joint of mini control arm showing joint assembly
and Plexiglass sheet for reducing friction.
Figures 8 and 9. Close-ups of miniature control arm joint design (open and closed) for
controlling the gripper portion of the manipulator.