## Introduction

An electrical system usually has four key parts to it:

1. the power supply,
2. control method (buttons/switches),
3. the load (light, solenoid, etc.), and
4. overload protection.

Sometimes the load can be controlled directly by a manual switch, like turning on the light in your room. In more complex systems, relays are used to control loads. These electrically controlled switches are used to control one circuit by opening and closing contact in a different circuit. Relays differ from motor starters in that they typically do not control power consuming loads directly, with the exception of small loads drawing less than 15A of current.

## Objectives

- Understand the function of a relay, and where and why it would be used.
- Understand the meaning of SPDT, DPDT contacts.
- Create circuit schematics in Automation Studio that use control relays and timing relays.
- Wire up circuits using control relays and timing relays.

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