Switchable Stepper Motor Drag Control
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
This article describes a means of using the back EMF of a permanent magnet (PM) stepper motor to produce mechanical drag effects. Switches in the motor's chopped current drive circuitry are closed to allow current to flow through the motor coil windings as the motor is being driven as a generator. This produces a drag that can be easily turned on or off. There is no interference with the normal operation of the motor and no additional circuitry is required.