| 摘要 |
PURPOSE: To detect the abnormality immediately and send out an alarm signal by determining that a stepping motor gets out of step when the counter electromotive force generated in a coil which was excited on a drive signal one signal prior to the one which excites a now excited coil is the same or lower than a specified value. CONSTITUTION: A CPU 25 outputs drive signals to excited coils of A phase, B phase, reverse A phase, and reverse B phase of a stepping motor sequentially. According to a drive pulse, current is allowed to flow in the excited coils 26, 27, 28, and 29 of the stepping motor. Comparators 34, 35, 36, and 37 determine whether the counter electromotive force generated in non-excited coils is a specified value or not. When the counter electromotive force generated in the coils other than the excited ones is detected and the detected value is the same or below the specified value, it is determined that the stepping motor did not work in correspondence with the driving signal from the CPU 25 and then an alarm signal 54 is generated. |
