| 摘要 |
PURPOSE:To simplify automatic stopping structure for a tape recorder, by detecting variations of current waveform of a brushed DC motor in order to detect existence of rotational pulse of a reel motor. CONSTITUTION:A reel motor M consisting of a brushed DC motor is controlled by a drive circuit 11 including transistors Q1-Q6, and playback, fast forward, and rewind are performed. Voltage variation of a resistor R1 for motor torque setting is detected by a rotational pulse detector 12 consisting of a differential amplifier 122 and a mono-multivibrator 123. Its output is induced to a logic LC via an integrator 124 and a switching circuit 125. And a control signal is produced. Therefore, existence of a rotational pulse can be detected by utilizing the indication of characteristics that current waveform shows different from those of revolution when the motor M is locked at a tape end. Accurate automatic stopping operation can be made possible. |
