Rotor movement warning device for use in stepper motors

A rotor movement warning device for use in a stepper motor has a stator provided with a plurality of windings and a rotor rotatably provided in associated with said stator. The rotor movement warning device includes a power source, a plurality of switching transistors provided in association with the plurality of windings, respectively, for controlling power supply from the power source to the windings, and a driving pulse producer for producing driving pulses to the plurality of switching transistors for effecting the rotation of the rotor. Further provided are detector for detecting, when the rotor stops, at least one switching transistor which is provided with the last driving pulse, and low frequency signal producer for producing low frequency signals which are applied to the switching transistor detected by the detector.