Although you can buy a wide range of shields for Arduino, making your own will not only save you money, it will give you more flexibility and control of your designs. This book shows you how to connect sensors and other devices to your Arduino inputs and outputs using basic components like resistors, diodes, transistors, and op-amps. All of the components used in this book can be purchased cheaply on eBay or Amazon, as well as other electronics outlets. Dozens of generalized circuits that you can modify for your needs are shown, complete with the necessary equations to select the proper component values for your needs. Heavy emphasis is placed on connecting sensors not originally designed for Arduinos to the analog inputs, as well as connecting signals other than 5 volts to digital inputs. Connecting heavy loads to the outputs is also discussed. Protecting your Arduino is the topic of one chapter, and specific tips for doing this are given for individual circuits throughout the book. This is a practical guide to designing electronic circuits to connect to your Arduino. Although it will be helpful if you already have a basic knowledge of electronics, this book provides a basic background, like reading schematics and choosing components.