| 摘要 |
PURPOSE:To repeatedly control between high and low speeds of rotating speed of a motor by detecting the induced voltage of the motor, comparing it with the first and second reference voltages, selecting the reference voltage according to the output, and switching the direction of the drive current. CONSTITUTION:The wound-resistor of a DC motor is represented by RM, the induced voltage is represented by EM, a circuit is formed of the first and second reference voltages E1, E2 and a comparator 2, and two values of +E, -E are obtained at the outputs of the comparator 2 in relation to E1<E2, R2=KR1, R3=KRM. The motor 1 is accelerated while the output +E so that EM does not exceed E2, the output of the comparator 2 is inverted when the EM exceeds the E2, the motor is decelerated at -E, and returned to the original state so that the EM becomes lower than the E1, repeatedly. Accordingly, the rotating speed can be reversely controlled from the first to the second value, or vice versa, and it can be adequately utilized to automatically research the linear speed at the position of a pickup for a player or the like. |
