| 摘要 |
PURPOSE:To eliminate a detector for detecting the full open and full close of a valve by detecting that a pulsation of a current flowing to a DC motor is eliminated to stop supplying a current to the motor. CONSTITUTION:When a power source is supplied so that a terminal 3 becomes + pole and a terminal 4 becomes - pole, the polarity is switched in a polarity changeover switch 6 so that a terminal 6a becomes positive pole and a terminal 6b becomes negative pole, a DC motor 1 is normally rotated to open a valve 2. When the valve 2 is fully opened, the rotation of the motor 1 is stopped to eliminate the periodicity of a current flowed to the motor 1. The period detected by a period detector 10 becomes larger than a set value, a signal is applied from a comparator 11 to the switch 6, the switch 6 is operated to stop supplying a current to the motor 1. |
