New electronic brains for Halfmann telescopes

Many components of our STELLA telescopes located on Tenerife, which were built by Halfmann in the 2000s have reached the end of their life with no replacement parts available. A solution was necessary to guarantee continuous operation and support for the next ten years. The prerequisite for the retrofit, however, was that the mechanical components remain largely untouched in order to simplify the upgrade. We decided to remove all the existing electronics in the main control cabinet. In order to avoid electronic interference in the scientific instruments, we took several precautions. This included an isolating transformer, line filters and power chokes for the servo drivers. All of the control electronics as well as the sensory inputs is now handled by Beckhoff components. A Beckhoff PLC CX5140 is the new "electronic brain" replacing a Linux computer running the telescope control firmware. The new telescope control firmware written in TwinCAT3 is available as open source. MQTT messages are used to command the telescope and report sensor values and position information. Sensor measurements and the state of the telescope are logged in an Influx-database and visualized using Grafana(dagger). Future enhancements include an improved guiding of the telescope using machine vision and a GigE camera in a closed loop on the PLC.