| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect a speed of a motor without influence of a circumference such as a temperature or the like. SOLUTION: The rotational speed detector for a motor comprises a control IC for controlling the motor so that a rotational speed per unit time of the motor becomes a predetermined speed (target rotational speed) based on a phase output of an encoder, a counter 21 for detecting a rising edge from a waveform of the output of the encoder to count a period of the phase output at the edge as a starting point, a holding circuit 22 for holding the period counted by the counter, a register circuit 23 for setting a minimum value and a maximum value of a predetermined range containing a period of the phase output of the encoder at the time of the predetermined speed, a comparator 24 for comparing the period held by the holding means with a period of a predetermined range set by the register circuit to produce different outputs according to whether the period held by the holding means falls within a predetermined range or not, and a tristate buffer 26 for outputting the output of the comparator to a data bus of a microprocessor. |
