Automation lies at the core of much of our modern lives. However, it evolves at radical speeds. The simple concept, to build a machine to perform a task without human intervention, was the engine of the industrial revolution. Now that concept is the driving force behind robotics, self-driving vehicles, and a wide range of advanced technologies.

Most automated tasks are part of a closed-loop system. This system is designed so that the outputs are monitored and fed back to the controller. The controller changes its operation as needed. An example of a closed-loop system is a home thermostat, which monitors the air temperature. When the low set-point is reached, a contact closes in the thermostat, beginning a furnace lighting cycle. As the furnace runs, the room air temperature increases until the high set-point is reached. The contact opens and ends the furnace burn cycle. This is automation.

With electrical relays, it is possible to achieve a variety of automatic functions. A motor starter uses a relay to close a contact that sends electrical power to a motor. In addition, it closes a set of auxiliary contacts that keep the main relay closed. A control mechanism, such as a temperature input or a stop button, can be wired in series with the auxiliary contact. This allows for control of the motor. An expansion of relay logic is the programmable logic controller or PLC. Instead of mechanical relays, a PLC uses a set of input and output contacts connected to a computer controller. Software in the controller then dictates how the inputs and outputs interact. They additionally execute specific patterns of operations, based on programmed ladder logic.