Multi-speed motor

Abstract

Control circuitry for a multi-speed, rotational, direct current motor can include a means to select one of a plurality of discrete circuits to select a desired speed of the motor, each circuit being activated by a separate analog switch which can complete the circuit to select a potentiometer voltage which then becomes a speed reference voltage output; a motor encoder which generates a pulse train proportional to motor speed and is converted to a proportional voltage by means of a frequency-to-voltage converter; an error amplifier, connected to the outputs of the speed reference voltage and the motor speed voltage such that when the speed reference voltage differs from the motor speed voltage, an error signal is produced; a pulse width modifier circuit which is driven by the error signal and which adjusts motor logic outputs so as to adjust the speed of the motor to produce an essentially zero error; a power supply circuit to feed voltage to the controlling circuitry and motor. Optional reset and start-up circuits can initialize various circuit time constants so as to produce a controlled ramp upon start-up of the motor, especially for applications to dynamometry such as with rotational viscometers. The motor with such circuitry and/or components is provided as well.