UpgradingtheBoe-Bot
Part 1
by William Henning
For those of you who are not yet familiar with the Boe-Bot, it is a small
(approximately 5” x 6”) robot with two wheel drive and a small spherical ball
acting as a third wheel. You steer the Boe-Bot by controlling the speed and
direction of the two continuous rotation servos. Due to the differential drive,
Boe-Bot can turn on a dime and even spin in place!
[The Parallax Boe-Bot is probably the most successful robot for the educational
market in North America – and it is also very popular with hobbyists. Recently,
the Boe-Bot became a recommended platform for completing the Boy Scouts of
America Robotics Merit Badge.]
FIGURE 1. Board of Education mounted on the Boe-Bot chassis.
The standard Boe-Bot kit uses a Parallax Board of Education
(BOE) as the “brain” of the robot,
and the BASIC Stamp processor
(BS2) provides a total of 16 I/O lines
to experiment with — four of which
go to three-pin servo connectors.
The excellent Robotics with the
Boe-Bot book initially configures
Boe-Bot with two “whiskers”
(basically, momentary contact
switches) to sense if it runs into
anything. Later experiments use the
included two IR LEDs and 38 kHz IR
detectors as distance sensors so
Boe-Bot won’t have to bump into
objects.
The BASIC Stamp used on the
Board of Education does not have
any “real” analog-to-digital
converters (ADC) in it. It does
include an “RCTIME” command that
can be used to measure the time
required to discharge a capacitor.
However, that can take many
milliseconds — time that cannot be
48 SERVO 09.2011
