Abstract

An apparatus for controlling conditions in response to an operator input, the apparatus including a rotary knob coupled to the shaft of the rotor of a stepper motor having first and second stator windings, in quadrature, with each winding being center tap grounded to provide first and second winding portions for each winding. One pair of first winding portions are used for providing pulse inputs to a microprocessor on rotation of the knob, in either direction, via a pulse control system, with the microprocessor providing command signals to a braking control system, which includes a direct current power control source, which may be either a voltage or current control source. The power control source, in turn is in circuit relation with the pair of second winding portions. On command of the processor, a force or torque is applied to the rotor, by means of energization of the other pair of winding portions, with the force being in opposition to the direction of rotation of the knob, the force being in proportion to the applied power. Under control of a microprocessor, the force may be intermittently applied to simulate a mechanical detent arrangement, or a constant force for braking, either of which provides tactile feedback to the operator.