Preliminaries

As an introduction, our students carry out control experiments with lights and switches. They get the necessary bits and pieces in a Fischertechnic box, and assemble circuits on the lid, using that ubiquitous engineering standby Blu-Tack for the non-Fischertechnic parts such as the PICAXE project board and the battery holder. The screw terminals we have fitted to the project boards greatly simplify connection.

It starts very simply, with switching on a lamp for a few seconds, and progresses to traffic light sequences which, in the final version, change on the press of a button. This requires students to deal with inputs as well as outputs, and also to get to grips with the inconvenient realities of interfacing to mechanical switches which have to be "debounced" in software, and may be sampled thousands of times by a program loop during a single button-press.

A speaker is connected for experiments with the sound command and, finally, students get to connect up and investigate the IR reflective sensors using a small section of printed track.