The polar coordinates plotter developed as a thesis in the NwT (Science and Technology) class. The task was to work through a scientific or technical topic and to design an experiment or a model for it. David recounts, how his project emerged:
“I decided to construct a polar coordinates plotter. In contrast to the usual plotters controlled with the commonly used Cartesian coordinates, the construction of my plotter suggests a control by polar coordinates. A circular paper is turned by the rotary table, simultaneously, the pen moves over the paper along the diameter. Various drawings can be put on paper through this overlapping movement.
I realised the mechanical assemblies mostly with fischertechnik parts since fischertechnik offers a stable and precise foundation for the widest range of technical applications. An interesting detail is the pen’s lifting mechanism: An XS motor moves a cam disc, which presses the pen down on the paper during rotation. When the XS motor moves the cam disc back, a return spring presses the pen in the initial position again. This construction facilitates the lifting and lowering of the pen in a very short time period.
An Arduino Mega takes over the electric control. I created a circuit board that allows the control of fischertechnik sensors (here: Limit switch of the axes) and fischertechnik actuators (here: Electric motor) using the Arduino platform. The Arduino forms the interface of the drawing machine to a computer, which computes the movements of the individual axes. I have described the plotter in great detail in the periodical ft:pedia 2018/02. There I go into the details of the mathematical backgrounds as well as the technical details of the machine.”