| 摘要 |
PURPOSE:To produce highly accurate speed electromotive force from a motor in a simple construction by constructing a resistor bridge with a drive coil disposed at one side and controlling the current amount of the drive coil via the detected voltage produced from the detecting terminal of the bridge. CONSTITUTION:The other end of a drive coil 11a is connected to a resistor R1 to form a resistor bridge 14 with other resistors R2, R3 and a coil 11 disposed at one side. The detecting terminals A. B of the bridge are connected through resistors 15, 16 to an amplifier 17. The output terminal of the amplifier 17 is connected through a smoothing circuit 22 consisting of a resistor R and a capacitor C to the bases of control transistors 23a, 23b, 23c. The emitters of the transistors 23a-23c are grounded, and the collectors thereof are connected to the bases of transistors 13a- 13c. Thus, speed electromotive force can be detected in repsonse to the rotating speed of the motor from the drive coil always energized to thereby control the speed of the motor in high accuracy. |
