| 摘要 |
A speed regulating circuit for a motor of a power coping saw includes a DC voltage circuit, a manual speed regulating circuit, a feedback controlling circuit and a motor driving circuit. The DC voltage circuit includes a diode, a resistor, a capacitor, and a Zener diode. The manual controlling circuit includes a Zener diode and a resistance. The feedback controlling circuit includes an amplifier, a transistor, a pulse transformer. The motor driving circuit includes an SCR and a diode. The manual controlling circuit may first be set with a reference voltage signal corresponding to the intended rotational speed of the motor. The reference voltage signal is sent to the feedback controlling circuit to get a rotational speed controlling signal of a motor with respect to the variation of loads. A DC current is then supplied to the motor driving circuit for constantly rotating the DC motor despite the variation of the load.
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