This is a project that I've been working on recently. What this gizmo does is simply turn a low voltage output on and off at intervals determined by the user. It could be looked on as a square-wave function generator, with low frequency outputs.
It was originally conceived for testing the actions of electro-pneumatically controlled pipe organs!
The accompanying pdf file explains its duties in greater detail. Feel free to probe around the schematics provided. If you really feel your life would be incomplete without one, I can supply the processor chip ready programmed at a small cost (I need to make small gains for the hours of programming!)
Included below is a MS Excel spreadsheet file, also a Lotus 123 file (whichever is your preferred number-cruncher,) from which you can glean all the Maplin part numbers. The prices are valid at the time of releasing these pages. The labour cost can be disregarded if you're the one doing the labour (as a hobby!)
Also included are the Coreldraw files for the panels and PCB's. These are only suggestions of how things could be laid out.
At the time of writing, only the negative version has been assembled and tested. The positive version should theoretically work however. Scroll down to below the pictures for the relevant files.
A view of the inside.
It's hard at work here...
...because it's driving this load!!!
Schematics altered on 15th August, 2006 to include "brownout protection" circuitry, as the units were affected by slowly decaying, or rough power sources. In the worst cases, the data, and even the program memory was permanently corrupted!