Old Lexan chassis from Lynxmotion.
motor controllers due to their servo-like control and ability
to not only handle these motors in pairs, but also to scale
up should a larger robot chassis be used.
The first thing I did was assembled the chassis which
was being repurposed from a previous robot project. The
HB- 25 motor controllers were installed in the belly of the
chassis in between the motors. As you can see from
Figure 2, it is somewhat of a tight fit. However, with
proper cable routing, you can almost say it fits like a glove.
The only thing I had to be cautious about was clearance for
the fans on each HB- 25. Figure 3 shows the lower section
of the robot assembled with one PING))) sensor installed
and a power switch for the motors. Batteries were added,
then the lower plate was installed along with some padding
to hold the batteries in place (see Figure 4).
Two batteries are used in this design. One is dedicated
to the motors and is switched independently using the
power switch shown in Figure 3. The other battery powers
the Super Carrier Board which, in turn, powers the GPS and
FIGURE 3. Lower section assembly.
FIGURE 2. HB- 25 motor installation.
LCD (which both consume a lot of power). The batteries are
standard 7.2V R/C battery packs from a hobby store. They
are rated at 2,600 mAh each.
A separate switch controls power to the Super Carrier
Board. As you can see in Figure 5, several three-pin headers
have been mounted for connecting the various sensors and
motors. The lower pins provide a provision for a pushbutton
which is used to set waypoints for the GPS navigation.
Figure 6 shows how the LCD and GPS mount to the top
plate, as well as the additional PING))) sensors and the
thermal array sensor. This plate is then installed on top
of the lower section of the robot using standoffs (see
Once the robot construction was completed, it was
time to download the program code (see Figure 8). The
program has a main loop that does the following tasks until
the last waypoint has been reached:
• Obtain current GPS coordinates.
FIGURE 4. Batteries installed.
SERVO 04.2010 39