| 摘要 |
PURPOSE:To surely apply control with simple constitution, by switching a control direction by a speed change detecting output in the turntable of a record player, etc. CONSTITUTION:A signal with a frequency proportional to the rotating speed of the turntable 1 is outputted from a head 2, and is converted to a voltage V at a frequency- voltage converter 3. The voltage V is compared with reference potential at a differential amplifier 4, and a driving motor 6 is servo-controlled via a power amplifier 5. When the table 1 is rotated reversely by a manual operation and rotating speed becomes less than reference rotating speed, the output of the amplifier 4 goes to a negative value, and the motor 6 is turned in a direction opposite to the same direction of manual turning, thereby, erroneous brake is applied. Then, the inversion of the output of the amplifier 4 to the negative value is detected by a comparator 9, and also, the output of an acceleration detector 7 goes to a positive value, and an FF11 is set via an AND circuit 10, then, the output of an amplifier 5 goes to 0 or the positive value, thereby, the erroneous acceleration of the motor 6 can be prevented from being generated. In such a way, it is possible to apply turning control surely with the simple constitution without necessitating the detection of a turning direction.
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