The Legobug is well-suited to applications where touch sensors or a single
front-mounted light sensor are adequate for navigation. Although it was
designed with lego motors and sensors in mind, the LegoBug can use
handyboard components with minor modifications and a little tape. To
accommodate our 9v motors and their extended axles, we moved the last
little wall of bricks by the gear train back one lego unit.
Coincidentally, the axles of the motors fit nicely into the holes in the
bricks in the back wall. The LegoBug's original back end support structure
will be largely discarded to accommodate the motors. To keep the motors
in place on the underside of the robot, apply tape liberally. The bars
that hold the wheel axles provide additional support for the motors. A
simple stabilizer may be added between the two axles to keep the motors
properly aligned. It may be necessary to add a few 1/3 tall plates or
bricks underneath the axle bar so the 24-tooth gears will mesh properly
with the worm gears (make sure that you add the same amount of height to
the front of the robot as well).
Mounting the touch sensors is more difficult, as there is a large disparity of size between Lego and Handyboard touch sensors. Lego sensors are rather oblong, while handyboard sensors are more square and compact. Align both touch sensors so the bumpers depress the touch bars adequately. We obtained a good connection when the sensors were mounted with a two-unit wide space between them and with a slight upward angle (the bumpers and touch bars shouldn't match up exactly, or else the hook end of the touch bar may fall into the bumper's hollow underside. If this happens, the sensor will not register a touch if the bumper is pressed). A 1/3 tall gap is the perfect size to string wires through. If the axles of your motors protrude through the rear of the motor, it may be necessary to align one of your gaps with the axle end.
Adding a light sensor to the robot is comparatively easy. Attach a beam of a size of your choice perpendicular to the 2x8 beam located above the bumpers and below the front wheels, as in the photo above. For light sensor mounting ideas, click here.