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15 | Diving Deeper into Control Image Source: "VRAYVENUS / stock.adobe.com" The first two articles in this series examined the basic operation of different electrical motors. In some simple applications, such as computer fans, electric motors that operate at a single speed and in a single direction can be run directly from the power source with no control required. No control is needed as the fan is almost always on, and the electronics are cooled when the computer is awake. However, many other installations require motors to be more flexible. Even a basic ceiling fan may have three or more speed settings that require a control circuit. That complexity continues to increase until we reach applications such as multi-axis robots, which use several different types of motors and are required to maintain torque at various speeds with accuracy and precision. Even at the lower end of the market, designers of products that use electric motors are now looking for more granular control to consistently match the motor's speed to the load for maximum efficiency. There are several different types of motors, each with pros and cons. Getting the best performance and efficiency out of these motors almost always involves implementing a suitable control circuit. Some control methods are simple and require only a few basic components, while others are hugely complex and need extensive hardware and software development. This article will look at the different types of control that can be used for each of the main motor designs. Brushed DC The brushed DC motor is an older design used today mainly because of its low cost. In many applications, designers will incorporate brushed DC motors without control circuits to keep costs down. However, if the speed of the motor needs to be changed or the direction of rotation needs to be reversed, a driver circuit will be required. A simple voltage