DC motor is a device that converts electrical energy into mechanical energy by rotating its shaft.
Sometimes we need minimum rotations and sometimes we need maximum rotation in a DC Motor.
So for this problem we use a motor speed controller to adjust the speed of a motor.
We create this circuit only by using a transistor we don't use any IC here.
What is Motor Speed Controller?
Motor speed controller it's such a circuit through which you can easily control the speed of a DC motor. Through this controller, you can smoothly adjust the motor speed. Simply have to rotate a potentiometer that generates the PWM signal using a transistor and control your motor speed.
In the circuit, we don't use any IC and microcontroller we only use a couple of transistors to make this circuit which you can easily found old circuits.
1) Bd139 and Bd140 Transistor
2) 100uf capacitor
3) 22k, 47Ohm, 220Ohm Resistance
4) 10k Potentiometer