METHOD AND DEVICE FOR DETECTING STOP OF STEPPER MOTOR

PROBLEM TO BE SOLVED: To eliminate the need for adding a detector, such as an optical encoder when stall and speed changes of a motor are detected. SOLUTION: When an electric motor 11, such as a stepper motor, is driven by an amplifier 12 such as a chopper amplifier, the changes with the passage of time for a current I flowing in the motor 11 are monitored. A timer 20 is started by a start trigger 14 for triggering the amplifier 12, while the timer 20 is stopped by detecting the chopping start or the like in the amplifier 12 with an adjustment circuit 16. Consequently, the measured value of the rising time or its partial time can be obtained in the timer 20. Alternatively, the output voltage V of the amplifier 12 is sampled, after a prescribed time from the rising start. A voltage, proportional to the rising time, is measured. An analyzer 30 evaluates the state of the motor 11, on the basis of the measured results. COPYRIGHT: (C)2005,JPO&NCIPI