Variable Power supply unit or Variable PSU is a must requires tool for electronics and electrical engineering related works. This is a necessary tool or device which should be there on your workbench. Here is an online variable power supply calculator tool for you. While designing a variable Power supply ( by LM317 OR LM338) we need to make sure about the desired output voltage and current specs. For that we need to take specific desired values for the resistors and some other components of fixed values. Like if you are making a VPSU( Variable Power supply unit) using LM338, then you need to use calculated values of R1 & R2. To get the desired output in a specific range like for e.g 1.5-28v DC.
So, below here is such a variable power supply calculator that shows you what will be the output voltage according to the resistor’s choice(R1&R2). But first, read this article (click here) if you are not familiar with all these and how to use it.