Stepper motor driving apparatus

A stepper motor driving apparatus, comprising:

• a stepper motor, which includes an excitation coil, and a rotor rotating in accordance with change of excitation state of the excitation coil;
• a driven member, which is interlocked with the rotation of the rotor;
• a stopper, which mechanically stops the driven member in a zero position;
• a controller, which controls the excitation state of the excitation coil;
• an induced voltage waveform detector, which detects an induced voltage waveform generated on the basis of change of magnetic flux in accordance with the rotation of the rotor;
• and
• a zero position detector, which detects whether the driven member is stopped in the zero position by the stopper or not, on the basis of the induced voltage waveform detected by the induced voltage waveform detector,
• wherein the zero position detector includes:
• a comparator, which compares the number of sampling cycles in which each induced voltage waveform sampled in predetermined sampling timing in a predetermined sampling time exceeds a predetermined threshold value with a predetermined contact determining reference number;
• and
• a determinant, which determines whether or not the driven member is stopped in the zero position by the stopper based on a result of the comparison by the comparator.