In the late 80s, early 90s I was fortunate to be recruited by Martyn Wilson of the Hampshire Microtechnology Centre to the Acorn Horizon Project. This ground breaking project provided the tools and resources for a team of teacher to create their own multimedia applications.
System Designer was my offering to this project. At the time the recently invented subject of CDT (“Craft, Design and Technology”, then “Design Technology”, then more recently “Technology”) was having a lot of fun with the recently invented BBC computer (BBC Model A, then BBC Model B, then the rather fantastic Archimedes RISCOS computers). Alongside this was a growing interest in all things electronic and the teaching of electronics found its way into most CDT schemes of work. It was, however, a fact that many teachers of CDT were at this time still based in the traditional Woodwork and Metalwork disciplines and many departments carried forward traditional themes into the new curriculum. A theme I noticed was gardening. I remember moving into a new workshop and clearing storage areas of garden dibbers which was a standard introduction to the mortise and tenon joint to year 8 pupils. When I took over a metal workshop I cleared out garden trowels which were the standard year 8 job for introducing brazing. When electronics was introduced to the year 8 scheme of work the standard introduction to electronics was a transistor sensing circuit. The standard job for this was…. a plant moisture sensor. This innovative device was intended to replace your finger to feel the dampness of the soil in your houseplant flowerpots so you could tell if they wanted watering or not.
Now, I may have missed something about the interests of the average 12 year old, but I never reckoned gardening as being amongst them. Judging by the number of dibbers and trowels that I that threw out that were never taken home by their year 8 crafters, I was fairly confident that that a moisture sensors would meet the same fate.
Actually, there are quite a number of sensing applications for a basic transistor circuit. For instance, if you replace the moisture sensing probes with an LDR (light sensor) you can sense light. If you transpose the potential divider you can sense darkness. If you use a thermistor (heat sensor) instead of an LDR you can detect heat, or conversely, coldness (relatively speaking). So with the original option of moisture probes pupils can choose from five different options. The original moisture sensor indicated that it had found moisture by lighting up an LED or sometimes by sounding a buzzer. If pupils could be allowed to choose their output options they could make one of 5 x 2 = 10 circuits, all with similar educational value. But there are other output options, such as a bulb or a motor. That gives 5 x 4 =20 different circuits. Even then there are some options for the transistor process. The standard arrangement for the moisture sensor uses a single transistor, but a Darlington pair (two transistors) is an arrangement that can make your circuit respond to smaller changes in its environment. This gives the pupil even more choice 5 x 2 x 4 = 40 different circuits.
These choices allow the student to engage in a more personal design exercise as the circuit can be used to solve a problem that has been identified by the student, and not just the moisture sensing non-problem traditionally provided for pupils. The remaining problem was how does the teacher provide the resources to cope with all these permutations? Pupils will need a circuit diagram, PCB (printed circuit board) layout showing the copper tracks needed to make the proper connections, and a drawing of what the circuit looks like so they can assemble it correctly. That is a total of 120 different illustrations, obviously not a practical prospect for even the most enthusiastic teacher.
System Designer allowed pupils to select input, process and output options and then print the various drawings required to build the chosen circuit. It is a pretty simple idea, in fact, the whole project was completed by authoring just three pages of Genesis code, and two of those were the title screen and an error page. But it is a simple idea one that opens up the design experience significantly for pupils.
You might ask where System Designer is now. Although shipped with the Horizon Project CDROM at the time, and by all accounts quite popular in Australia, I never worked-up versions for Windows based PCs and my version died alongside the doomed Acorn RISCOS PC. The idea was subsequently “adopted” by D&T Online who have reproduced my original idea and added a few bells and whistles and I am grateful that they have kept the idea alive (although I do twitch when I see the copyright notice on their site).
With the resurgence of electronics in the curriculum I hope to build on this page over the coming months and provide teaching resources that will support the use of the D&T Online version in the classroom.