Patent ID: 6924616

Claim:
A rotational driving apparatus comprising: a stepping motor supported by a housing; an output shaft rotationally supported by the housing and driven by the stepping motor; a rotational position detecting sensor for outputting a detected voltage in response to a rotational position of the output shaft; and a position detecting means for detecting the rotational position of the output shaft in accordance with the detected voltage from the rotational position detecting sensor, wherein the position detecting means comprises; a means for determining that the output shaft is in a good operational order when a first detected voltage of the output shaft at its first detection position (Step=0) and a second detected voltage of the output shaft at its second detection position (Step=n), to which the output shaft has been rotated by the stepping motor by a predetermined number of control pulses, are respectively within a predetermined error range; and when a deferential voltage between the first and second detected voltages corresponding to the predetermined number of control pulses between the first and second detection positions is within a certain deferential voltage span.