A novel signal processing circuit for contactless motion detection

This paper presents a novel electronic circuit to determine the speed and direction of motion of a trackball through a non-contacting motion detection mechanism. The trackball comprises of a ball and a pair of electromagnets made of magnetic grade stainless steel material. The electromagnets, placed substantially orthogonal to each other, record the magnetic information onto the ball surface. The electronics described herein make use of the Hall sensors which act as reading heads to retrieve the magnetic information off the magnetized ball surface. The signals generated by the Hall sensors are then acted upon by logic and analog circuits to convert the ball motion into the X and Y components of the cursor position on the screen. The new circuit ensures motion detection even in harsh environments and hence overcomes the limitations faced by existing trackballs. (C) 2009 Elsevier B.V. All rights reserved.