Most systems using the Arduino have a similar architecture. They have a way of reading data from the environment—a sensor—they make decision using the code running inside the Arduino and then output those decisions to the environment using various actuators, such as a simple motor. Using three recipes from the book, Arduino Development Cookbook , by Cornel Amariei , we will build such a system, and quite a useful one—a fan controlled by the air temperature. Let's break the process into three key steps, the first and easiest will be to connect an LED to the Arduino, a few of them will act as a thermometer, displaying the room temperature. The second step will be to connect the sensor and program it, and the third will be to connect the motor. Here, we will learn this basic skills.
In this article is written by Mitja Resman , author of the book CentOS High Availability , we will learn cluster resource management on CentOS 6 with the RGManager cluster resource manager. We will learn how and where to find the information you require about the cluster resources that are supported by RGManager, and all the details about cluster resource configuration. We will also learn how to add, delete, and reconfigure resources and services in your cluster. Then we will learn how to start, stop, and migrate resources from one cluster node to another. When we are done with this article, your cluster will be configured to run and provide end users with a service.
In this article by Samarth Shah , author of the book Learning Raspberry Pi ,we will take your Raspberry Pi to the real world. Make sure you have all the components listed for you to go ahead: Raspberry Pi with Raspbian OS. A keyboard/mouse. A monitor to display the content of Raspberry Pi. If you don't have Raspberry Pi, you can install the VNC server on Raspberry Pi, and on your laptop using the VNC viewer, you will be able to display the content. Hook up wires of different colors (keep around 30 wires of around 10 cm long). To do: Read instructions on how to cut the wires. An HD44780-based LCD. Note; I have used JHD162A. A breadboard. 10K potentiometer (optional). You will be using potentiometer to control the contrast of the LCD, so if you don't have potentiometer, contrast would be fixed and that would be okay for this project. Potentiometer is just a fancy word used for variable resistor. Basically, it is just a three-terminal resistor with sliding or rotating contact, which is used for changing the value of the resistor.
In this article by Chamil Madusanka , author of the book Learning Force.com Application Development , you will learn about the custom coding in Apex and also about triggers. We have used many declarative methods such as creating the object's structure, relationships, workflow rules, and approval process to develop the Force.com application. The declarative development method doesn't require any coding skill and specific Integrated Development Environment (IDE). This article will show you how to extend the declarative capabilities using custom coding of the Force.com platform. Apex controllers and Apex triggers will be explained with examples of the sample application. The Force.com platform query language and data manipulation language will be described with syntaxes and examples. At the end of the article, there will be a section to describe bulk data handling methods in Apex. This article covers the following topics: Introducing Apex Working with Apex
In this article by the author, Daniel Hall , of the book, Ansible Configuration Management - Second Edition , we learn to start digging a bit deeper into playbooks. We will be covering the following topics: External data lookups Storing results Processing data Debugging playboks
This article is written by Cecil Costa , the author of the book, Swift Cookbook . We'll delve into what profiling is and how we can profile an app by following some simple steps. It's very common to hear about issues, but if an app doesn't have any important issue, it doesn't mean that it is working fine. Imagine that you have a program that has a memory leak, presumably you won't find any problem using it for 10 minutes. However, a user may find it after using it for a few days. Don't think that this sort of thing is impossible; remember that iOS apps don't terminate, so if you do have memory leaks, it will be kept until your app blows up. Performance is another important, common topic. What if your app looks okay, but it gets slower with the passing of time? We, therefore, have to be aware of this problem. This kind of test is called profiling and Xcode comes with a very good tool for realizing this operation, which is called Instruments . In this instance, we will profile our app to visualize the amount of energy wasted by our app and, of course, let's try to reduce it.
JMeter comes with a built-in test script recorder, also referred to as a proxy server ( http://en.wikipedia.org/wiki/Proxy_server ), to aid you in recording test plans. The test script recorder, once configured, watches your actions as you perform operations on a website, creates test sample objects for them, and eventually stores them in your test plan, which is a JMX file. In addition, JMeter gives you the option to create test plans manually, but this is mostly impractical for recording nontrivial testing scenarios. You will save a whole lot of time using the proxy recorder, as you will be seeing in a bit. So without further ado, in this article by Bayo Erinle , author of Performance Testing with JMeter - Second Edition , let's record our first test! For this, we will record the browsing of JMeter's own official website as a user will normally do. For the proxy server to be able to watch your actions, it will need to be configured. This entails two steps: Setting up the HTTP(S) Test Script Recorder within JMeter. Setting the browser to use the proxy.
In this article by Patrick Li , author of the book JIRA Essentials - Third Edition , we will start with a high-level view of the overall hierarchy on how data is structured in JIRA. We will then take a look at the various user interfaces that JIRA has for working with projects, both as an administrator and an everyday user. We will also introduce permissions for the first time in the context of projects and will expand on this. In this article, you will learn the following: How JIRA structures content Different user interfaces for project management in JIRA How to create new projects in JIRA How to import data from other systems into JIRA How to manage and configure a project How to manage components and versions
In this article by Jayant Kumar , author of the book Apache Solr Search Patterns , we will discuss use cases for Solr in e-commerce and job sites. We will look at the problems faced while providing search in an e-commerce or job site: The e-commerce problem statement The job site problem statement Challenges of large-scale indexing
In this article by Siddharta Govindaraj , author of the book Test-Driven Python Development , we will look at the Event class. The Event class is very simple: receivers can register with the event to be notified when the event occurs. When the event fires, all the receivers are notified of the event. A more detailed description is as follows: Event classes have a connect method, which takes a method or function to be called when the event fires When the fire method is called, all the registered callbacks are called with the same parameters that are passed to the fire method Writing tests for the connect method is fairly straightforward—we just need to check that the receivers are being stored properly. But, how do we write the tests for the fire method? This method does not change any state or store any value that we can assert on. The main responsibility of this method is to call other methods. How do we test that this is being done correctly? This is where mock objects come into the picture. Unlike ordinary unit tests that assert on object state , mock objects are used to test that the interactions between multiple objects occurs as it should.
This article is written by Brenton J.W. Blawat , the author of Mastering Windows PowerShell Scripting . When you are automating tasks on servers and workstations, you will frequently run into situations where you need to manage files, folders, and registry items. PowerShell provides a wide variety of cmdlets that enable you to create, view, modify, and delete items on a system. In this article, you will learn many techniques to interact with files, folders, and registry items. These techniques and items include: Registry provider Creating files, folders, registry keys, and registry named values Adding named values to registry keys Verifying the existence of item files, folders, and registry keys Renaming files, folders, registry keys, and named values Copying and moving files and folders Deleting files, folders, registry keys, and named values To properly follow the examples in this article, you will need to sequentially execute the examples. Each example builds on the previous examples, and some of these examples may not function properly if you do not execute the previous steps.