Correspondence Address: (57) ABSTRACT CARLSON, GASKEY & OLDS, P.C. 4OO WEST MAPLE ROAD SUTE 350 BIRMINGHAM, MI 48009 (US) Brushed DC electric motors have a rotor with commutator portions moving into and out of contact with brushes. As each of these contacts end, a back EMF force is induced into a main current Supply signal. The number of these periodic (73) Assignee: Masco Corporation forces can be counted and utilized to identify the position of (21) Appl. No.: 11/134,925 the component being rotated by the DC electric motor. This method is relatively insensitive to environmental changes, (22) Filed: May 23, 2005 and thus more accurate than the existing art.
