Book Image

Arduino Development Cookbook

By : Cornel M Amariei
Book Image

Arduino Development Cookbook

By: Cornel M Amariei

Overview of this book

Table of Contents (16 chapters)
Arduino Development Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Relay driver


Sometimes we just need to easily switch on and off an external load. Maybe the load is powered by AC current; maybe it's very high voltage that the Arduino can't handle. A transistor is usually used to power on such things; however, transistors are quite complicated. There is a simpler device that can just switch on or off, at slow speeds, an external load. This device is known as a relay.

Getting ready

To execute this recipe, we will need the following ingredients:

  • An Arduino board connected to a computer via USB

  • A general 5 V relay

  • A resistor between 220 ohm and 4700 ohm

  • A standard NPN transistor (BC547, 2N3904, N2222A, TIP120)

  • A standard diode (1N4148, 1N4001, 1N4007)

How to do it…

The relay coil unfortunately uses quite a lot of current. To prevent this from burning the Arduino pins, we will use a transistor driver to start the relay:

  1. Connect one of the terminals of the relay coil to the 5V pin on the Arduino.

  2. Check the data sheet of the transistor. We need to correctly identify the...