PWM Motor Speed Control Circuit

Here is a simple PWM motor speed controller circuit that can be used for varying the speed of low power DC motors .The variation in speed is achieved by varying the duty cycle of the pulse supplied to drive the motor.Of the two gates of IC CD40106B ,N1 is wired as an inverting Schmitt Trigger astable multi vibrator for producing pulses and N2 as an inverting buffer to drive the transistor during positive cycles at base.The duty cycle is set from resistor R2. R1 limits the base current of transistor SL 100.The circuit is ideal for controlling toy motors,hand held mini fans , small blowers etc.








Notes .

* By varying R2 duty cycle can be varied from 0% to 100%.
* For identifying pins of SL 100 ,the pin that is connected to casing is collector,the pin near to notch is emitter and the one remaining is base.