Reviving an
Androbot BOB
by Robert Doerr
I enjoy restoring early personal robots to their
original working condition. Most of my time is spent
working on the HERO robots, but I always have
other projects going on. One robot in particular — an
early Androbot BOB prototype — was missing all of
his brains and had been sitting for years as an empty
shell. That was just not acceptable! Since the original
electronics would probably never be found, I decided that
I should at least use some of the extra robot parts from past
projects to get BOB rolling again.
These new electronics would be
something that could plug in so
that no alterations would be done to
the original shell. After all, I would like
to keep him intact since I hope to find
the original brains and properly restore
him someday! As this project progress-es, it will be documented and present
some cool ideas that can be used on
your own robots. This first article will
cover a modification I made to the
Handy Board to make it safer to use on
large robots and how I enabled it to
run the larger motors on the BOB base.
There are a few other modifications
that are going to be done to the Handy
Board controller but those deal with
power and expansion and will be
addressed later.
For the moment, the new brain for
BOB is going to be an MIT Handy
Board with the optional expansion
board. It is a 68HC11-based controller
designed for experimental mobile
robotics work. Although there are
more powerful boards on the market,
it is still a great little controller for many
projects. The Interactive-C environment
already provided a lot of the required
functionality and it is easy to add on as
needed. (There is already a library of
extra add-on code and examples on
the Handy Board users group.)
Since the Handy Board is normally
used on smaller robots, something
would need to be done to drive BOB’s
larger motors. A couple of issues
needed to be addressed to make this
happen. One is the way it handles the
initialization of the motor logic. The
other is the limited ability to drive large
motors. Many of the ideas to get
around these issues will apply to other
controllers besides the Handy Board.
The Issues
The firmware for the Handy Board
and the users program is stored in a
single 32K static RAM chip at U2. It will
only keep its contents as long as there
Here’s a photo of poor old BOB
in the state I found him in.
is power. When the Handy Board is
switched off, this static RAM chip is still
powered by the battery to preserve its
contents. Even though the SRAM chip
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