Book Image

Raspberry Pi 3 Projects for Java Programmers

By : Rajdeep Chandra, John Sirach, Pradeeka Seneviratne
Book Image

Raspberry Pi 3 Projects for Java Programmers

By: Rajdeep Chandra, John Sirach, Pradeeka Seneviratne

Overview of this book

Raspberry Pi is a small, low cost and yet very powerful development platform. It is used to interact with attached electronics by the use of it's GPIO pins for multiple use cases, mainly Home Automation and Robotics. Our book is a project-based guide that will show you how to utilize the Raspberry Pi's GPIO with Java and how you can leverage this utilization with your knowledge of Java. You will start with installing and setting up the necessary hardware to create a seamless development platform. You will then straightaway start by building a project that will utilize light for presence detection. Next, you will program the application, capable of handling real time data using MQTT and utilize RPC to publish data to Further, you will build a wireless robot on top of the zuma chassis with the Raspberry Pi as the main controller. Lastly, you will end the book with advanced projects that will help you to create a multi-purpose IoT controller along with building a security camera that will perform image capture and recognize faces with the help of notifications. By the end of the book, you will be able to build your own real world usable projects not limited to Home Automation, IoT and/or Robotics utilizing logic, user and web interfaces.
Table of Contents (8 chapters)
Integrating a Real-Time IoT Dashboard

How to emulate reading analog values on digital pins

Let us start with some theory. The Raspberry Pi only has digital pins. This results in being unable to read analog values. But with some devices, we are able to read analog values, or rather, create an RC Circuit to cheat a little bit. An RC circuit is a circuitry setup where we place a resistor and a capacitor in series with each other. When a voltage is applied on the circuit, the voltage across the capacitor will rise. The higher the resistor value is, the longer it will take for the voltage to rise across the capacitor.

With a fixed resistor, the time to equalize the voltage before and after the resistor around the capacitor will be the same. When we introduce an LDR, where the resistor value depends on the light intensity, the more light that hits the sensor, the lower the resistance is. With this in mind, we take a look at a feature on the digital pins on...