How can you build a circuit to control the speed of a DC motor?
To build a circuit to control the speed of a DC motor, use a Pulse Width Modulation (PWM) controller, typically involving a 555 timer IC or a microcontroller. The PWM signal regulates the motor's speed by adjusting the duty cycle of the voltage applied to the motor. A transistor or a MOSFET is used to interface the PWM signal with the motor.