Master Clock
The aim of the project is to control so called slave clocks without an associated master clock. Batteries are to be used as the energy source.
The type of slave clocks in question were often used for example in factory halls. They are very often found with the imprint of Siemens or similar companies. The slave clocks are designed so that the minute hand advances by one minute at a time with each electric pulse. A positive and a negative voltage pulse must be applied alternately. Clocks are usually operated with ±12 V or ±24 V. There also appear to be a few models with higher voltages.
The operation of the clocks is well explained in German by Rolf Süßbrich in a similar project (archived Version). I used the same basic idea as that project. However, I used a microcontroller to generate the minute pulse, as this should do the job more energy-efficiently than classic CMOS components. Instead of working with 10 batteries for the 12 V input, a small step-up regulator was built, which is also suitable for 24 V clocks. For the output stage, the idea of using an operational amplifier was taken up.
A full description can be found on the project page on GitHub.