This project involved a number of mechanical, electrical, and software challenges; these challenges are described in more detail in the “mechanical,” “electrical,” “firmware,” and “software” tabs of this site.
The major mechanical challenge we faced was designing a robust rotating system capable of transmitting power to the display circuitry. We powered the display using a commercially-available rotating connector from Mercotac. The mechanical system also had to be sufficiently reliable to withstand multiple tests at a minimum rotation speed of 10 Hz to achieve persistence of vision. For more details, see the mechanical system description.
The main challenge when designing the electrical system was to control 40 LEDs with a single PIC for the 3D system. To accomplish this, the LEDs were split into four columns of 10 LEDs each which could be selectively turned on and off by controlling the LED ground with a MOSFET transistor. For more details, see the electrical system description.
In order to achieve persistence of vision, the rotating LEDs must be turned on and off at short, controlled time intervals. We initially attempted to control this timing using interrupts on a PIC18F2455 microcontroller, but determined that manual control of motor speed by adjusting input current was sufficient for the display, and added more flexibility in creating animated images on the display. Another key challenge that we encountered when developing the firmware for our system was storage space on the PIC18F2455. We modified our image storage approach to compensate for this to some extent, but were still limited by the amount of space needed for a 3D system. For more details, see the firmware description.
The final consideration for our project was user interactivity. While commercial POV displays present a static image, our display was intended to be customized. Therefore, we created a GUI in Python to enable users to draw an image for the display; it also allows users to save the image they have drawn as a text file. For more details, see the software description.
Another challenging aspect of the project was finalizing a mechanical system in time to test the functionality of our electrical and software systems. As none of the members of our team were mechanically inclined, this took an especially large amount of time and limited our ability to build in additional capabilities to the display.