5 weeks went quickly (where are all the hours?) and it's time for a short summary. The main intention of this section of HackadayPrize2016 was to evaluate motion sensing. As shown in the past 2 logs, optical sensors from old printers or scanners and even en electromechanical solution work fine. I wasn't successful in using an optical mouse (yet) since the two devices I own don't support the PS2 protocol (they talk definitely USB only). The Arduino software works in principle as I could test with my ball mouse:

The cheap optical mice I have ordered did not arrive yet. I will make a video about those interesting option of motion sensing later.

The analog reading of optical sensors as suggested in a comment might become an option in the next section when I'll try to examine the accuracy of DIY linear drives.

Using hall sensors does not have significant advantages (if at all) over the optical sensors and since I am short in time I won't use them in my design (but keep them in mind).