Small DC motor control circuit (1)

Circuit working principle: The core of this circuit is the 40106 multivibrator IC . The input
level is below its low threshold, so Ic,. The output (pin 2) is high level, C1 is quickly charged through VD1 and , and the voltage at both ends rises to IC
within 1.5 ms . . high threshold, so its output goes low, and c1 is discharged through VD2, R2, and RP1. The discharge time of this circuit prototype is set at 0.2~25 ms. Therefore, the duty cycle of the output signal varies from 5% to 90%.