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Birth of the MiniBot
My youngest son asked me to
build up another custom robot. I
enjoy working on all sorts of robot
projects and didn’t need much
encouragement to start another one.
For years, people have been using
trash cans as bodies for robots. They
work out great for providing a
protective cover for all the electronics
and can also serve as the chassis.
We had gone to the local Target
and while browsing the isles, I
noticed a small trash can that looked
ideal as the basis for a new robot. It
was a 1.32 gal (5L) swing can that
seemed to be Target’s own ROOM
ESSENTIALS brand. The base is about
8-1/2” tall and 7-7/16” in diameter.
With the top installed, the overall
height is 12”.
I saw they carried these small
trash cans in both black and a frosted
white/clear version. At under $8 a piece, I bought one of
each to use as the base/frame for the new robot. Since I
now had two different ones (funny how one project easily
turns into two!), I decided that I would build one using a
Parallax P8X32A Propeller QuickStart board as the brain and
the other would be based on the popular Arduino
Duemilanove/UNO board using an the Atmel ATMEGA328
To keep the costs down, I wanted to use many of the
inexpensive robot sensors that have been showing up on
propellerpowered.com and on eBay. In particular
are the HC-S04 sonar rangers, PIR sensors, digital
voltmeters, and small 9g servos that are right around $3
each. There is also a relatively new text-to-speech chip
called the RoboVoice that has been on sale for about $17
NOTE: Since this trash can had a
top cover with the swing lid, I added a
servo to control the movement of the
lid similar to what another prolific
robot builder (Steve Norris) had done
on his BAXTER robot. His robot is a
much larger scale build than presented
here, but both are based on swing
trash cans and use a servo to move
His robot is a great example on
where you can go when you want to
step up to even larger robots. Check
out the links in the sidebar to get
more details on his robot. PIR sensors.
The finished robot next to a bare trash can.
Preparing the Drive System
in the Base
The MiniBot uses a pair of standard size continuous
rotation hobby servos for the main drive system. These are
the easiest way to get a small robot mobile. I’ve used them
before on my SpindleBots which I wrote about back in the
April 2012 issue of SERVO Magazine.
On all of these robots, I modified standard servos for
continuous rotation. The method I prefer is to bring the
adjustment potentiometer outside of the servo. With the
potentiometer exposed, the servo can be calibrated and
adjusted at any time to set the center/neutral point.
If you want to go that route, you can get details from
my SpindleBot article or from numerous places on the Web.
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