Arduino Companion is an app for people who are usually on the go and would like to have a full Arduino reference at the palm of their hands anytime and anywhere. And since this is an offline reference you won't need to connect to the web for a quick look.
EAGLE is perfect for students and professionals because of its user-friendly interface and lots of features for your simple to hands-down complicated circuit designs. Because of the many things you can do with EAGLE I will not just focus on the tools and the steps that I used in making my VPS and how I did it.
A Variable DC Power Supply (VPS) is a device that supplies electric power to an electrical load and, as the name implies, allows the user to vary or change the DC output voltage within the specified voltage ranges. - which is the only difference compared to a Regulated Power Supply that spits out a constant output voltage.
A well-maintained soldering iron is necessary to properly solder your components, this is to make the solder stick to your iron and to the board for faster soldering. Failure to do so will cause the solder not to stick to your 'burnt' iron and may cause overheating your board.
iCircuit is an easy to use circuit simulator and editor on your iOS and, recently, Android phone. It's a perfect tool for engineers, students, and hobbyists who are on-the-go and need a quick look at how a circuit works.