particular device, it would be best to ask on the Parallax
support forums since someone there is always willing to
To finish off the installation, I used a small mono audio
amplifier for the RoboVoice chip so it can drive the 8 ohm
speaker on the front of the robot. It is mounted on the
back of the robot and has a volume control which is a nice
option to have.
Building the Arduino-Based
For the Arduino-based MiniBot, I ended up mounting
the RoboVoice chip and audio amp all on a small board
attached to the back of the robot. It has an onboard 3.3V
regulator for the RoboVoice since all the other I/O and
devices are running at 5V.
We just need a generic shield to plug in that we can
use to interface the processor board with all our devices. I
used a Seeed Studio Arduino Protoshield that I picked up at
my local RadioShack store. This board held a two-pin
connector for the head switch, all the three-pin headers to
connect to the servos and PIR, and a four-pin header to
connect to the sonar module.
You can set up the I/O on these anyway you like, and it
can match what you may have done on previous open
chassis robot projects.
Last Minute Upgrades and Fixes
to the MiniBots
After the MiniBots were built, I ran into a few issues
while writing the demo programs for them. The first issue
dealt with servo creep on the main drive wheels. While I
thought I had set the neutral position on the servo to
match the output of the controller, it seemed that one of
the wheels would just barely turn and creep along when it
was supposed to be idle. The first versions used a regular
servo that was hacked for continuous rotation.
Since the adjustments were inside the robot, I had to
remove the head to re-adjust them. Once adjusted, a drop
of glue helps keep the setting from changing. Because of
this, I recommend using the Parallax continuous rotation
servos instead, and put a couple access holes on the back
of the robot near the bottom so they can be re-adjusted
easily without needing to remove the head of the robot.
The next issue had to do with the HC-SR04 sonar
module. Some of the readings I was getting were off. It
seemed that perhaps some of the signal was bouncing back
off the swing lid of the can. To help reduce this, I added a
small piece of foam around the two metal cans of the
sensor. The holes were cut using a small X-acto blade; I cut
The finished insides of the Arduino based robot.
The finished wiring for the Arduino based robot.
The combo RoboVoice and amp board
used on Arduino Minibot.
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