It's not a secret. It's supposed to be a model of an inverse pendulum for my graduation thesis. I need precision of about 0.5 angular degree, but measuring speed is more important than measuring position, and in fact I doubt the analog encoders from the cheap a4tech mouse could provide that much, even with custom code wheel. The "puzzle" encoders from a Logitech Pilot mouse seemed to do the job, a custom 720CPR code wheel worked OK as long as it was connected to the mouse, but they let the magic smoke go and are no longer an option unless I buy another logitech mouse... The encoders from the printer, in the other hand, seem to provide more than enough precision. The QEDS encoder is on a motor I got my hands on, but it's completely unknown.