This post shows how to use a relay module with an Arduino board. A relay is an electrically operated switch that you can use to control mains voltage appliances
How to Use a Relay Module with Arduino
Guide for Relay Module with Arduino
A Beginner's Guide to Using Relay Modules in Arduino Projects
Relay Module with Arduino – Step by Step Guide - Circuit Magic
How to use 5v relay module Arduino UNO with 5v relay module [Code and circuit diagram]
Handson Technology MDU1137 Capacitive Touch Sensor Relay Module User Guide
In-Depth: Interface Two Channel Relay Module with Arduino
Relay Module: A Complete Guide
Relay Module - Brown Dog Gadgets Guides
8 Channel 5V Relay Module - Wiki
How to use a 5V Relay with Arduino