This circuit lets you design your own robot to suit your own
taste. It would not be difficult, for instance, to convert this design to a
credible R2D2, without any modification to the PC board. With a little
imagination, the possibilities would be even wider. The circuit could operate a
pulley system, serve as a line-tracker or rotate motors in response to broken
beams of varying intensity, without modification to the PC board.
As noted, the robot is programmable. Therefore, the drive
circuit is merely a slave to the software and is of a relatively simple design.
The circuit is based on a PICAXE-08 micro, as has been featured previously in
SILICON CHIP. Although more limited than a "raw"
microcontroller, it is a small marvel nonetheless – both for cutting out the
need for a costly programmer and for placing respectable power at the service of
the constructor with great simplicity.
All that the Programmable Robot requires in its support is a PC
and a serial cable. The programming software is free www.rev-ed.co.uk and comes in the
form of a telegram-style BASIC and flowchart programming.
Note that the Programmable Robot’s memory is limited – not all
the features listed above can be used at the same time. However, with careful
programming, the robot will perform most dual or even triple tasks with aplomb.
As an example, light-seeking, bump-and-respond and sound can all be incorporated
in a single program.
Since the PICAXE-08 microcontroller represents the Programmable
Robot’s "control room", this is where we shall begin. Unfortunately, the
PICAXE-08 is confusing in its pin numbering, which has become something of a
legend in its own time – therefore we shall resort to the standard IC pin
numbering here; ie, pins 1-8, with pin 1 being situated next to the small
indentation on top of the IC.
Table 1: PICAXE Motor Control Outputs
|Pin 7 (P0)||Both motors on||Both motors off|
|Pin 5 (P2)||Left motor backwards||Left motor forwards|
|Pin 3 (P4)||Right motor backwards||Right motor forwards|