This is one of the most effective circuits used to manage the speed of DC motor with the help of pulse width modulation. In this circuit, the DC motor is operated by a 555 integrated circuit. The IC 555 in this circuit is being operated in astable mode. In this mode, the circuit can be used as a pulse width modulator with a few small adjustments to the circuit. For detailed information about this circuit and its applications, read the post: DC Motor Speed Control using Pulse Width Modulation.