Electronics Cookbook

Chapter 13. Motors

13.0 Introduction

This chapter looks at various types of motors and how both their speed and direction can be controlled. This involves the electronics of controlling fairly high load currents as well as the software needed. This chapter will cover examples for Arduino and Raspberry Pi.

When people talk of motors, what tends to spring to mind are the small DC motors that you might find in a battery-powered toy car. DC motors are common and often combined with a gearbox to reduce their high speed of rotation into a single unit called a gearmotor.

Stepper motors operate on a different principle and are found in printers of all sorts including 3D printers as they can be advanced in small steps (typically 1/200 of a revolution or more).

Servomotors fit a different niche, allowing accurate positioning of their “arm” in a restricted range of angles (about 180°). Servomotors are often found controlling the steering of a remote-control car or the control surfaces of a remote-control plane or helicopter.

All of these types of motors are available in various sizes to meet the power requirements of different applications. Whatever the size, controlling such motors follows the same basic principles.

13.1 Switch DC Motors On and Off

Problem

You want to control a DC motor using a small control voltage—typically from a GPIO pin.

Solution

Use a transistor switch, but add a snubbing diode as shown in Figure 13-1. This is based on Recipe 11.1, which is fine for a small ...