In Chapter 7, Turning Things On and Off, we learned how to use a transistor to turn a DC motor on and off, and we also saw how to control the motor's speed using PWM. One limitation of our single transistor circuit was that the motor only rotated in one direction. In this section, we will explore a way to let us spin our motor in both the forward and backward directions – using what is known as an H-Bridge circuit.

If you search around sites such as eBay for an H-Bridge module, you will identify many ready-made modules for the same purpose that we will cover in this section. What we will do is build a replica module on our breadboard. Once you have your breadboard replica working and understand how it works, you will be in a position to understand the construction of...