INTRODUCTION

We've talked about some types of power that can move components (for example, electrical and pneumatic) and set it up on our machine (Basic Automation Trainer). Now let's talk about how these components are activated.

The system that controls components is called the control system. A control system is what causes different components on a machine to activate. (How does the conveyor know to turn on? When does the pneumatic cylinder extend?)

Most industrial systems have some sort of electrical control system. Two types of electrical control systems are PLCs and motor control circuits. You will learn about both of these systems in this course.

Many industrial systems use a PLC (sort of an industrial computer) to control the system. However, many older systems—and most simple ones—use a motor control circuit. This means that they have electrical components wired up in a way that provides control, such as Stop & Start or Forward & Backward functions. Below are two simple examples of control circuits.

First Example

In this first example, the button is "Normally Open (NO)," which means that it does not complete the circuit. The power cannot get from the power source (L1) to the light. When it reaches the button, the electricity can't keep going. Once the button is pressed, it closes the circuit, completing the pathway, which just means that electricity can now flow from the power source (L1) to the light.

Simple schematic for a button and light

Second Example

In this second example, When the start button is pushed, it provides electricity to the coil. (The coil is a load, like a light is a load.)

Typical Motor Control schematic

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IMPORTANCE OF MOTOR CONTROLS CIRCUITS

A motor control circuit consists of one or more circuits that run off of low voltage (typically 24VDC or 24VAC) which controls the voltage and function of a higher voltage system (120V, 220V, 480V). So instead of people needing to switch on and off these high voltage systems (which has been proven to be dangerous), we use low voltage switches and components to do this for us. Using buttons and switches helps keep people safe.

Understanding how motor control circuits work can help you not only troubleshoot issues in the workforce, but it can also help give you an edge in building and improving new or existing equipment. In the workforce, employers can give you a schematic of a motor circuit and expect you to know how that circuit would work.