No matter what electronics project you are building, a power supply is an important part of it. For quick tests and prototyping, it is best to use a variable bench power supply that could be reused for different purposes. If you are serious about electronics, it is probably best to invest in a good bench power supply. But this is also fun to build one by yourself. Abhishek decided to make a pretty simple power supply that would fit his needs.
He decided to use linear voltage regulators to get the needed voltages. So the first state he made was stepping down 220V to 20V DC, which then could be regulated with linear regulators. He decided to make 5V and 12V by using 7805 and 7812 regulators. Then he used another LM338 to get variable voltages from 1.2V to 25V. Using separate regulators gives the ability to drive higher loads in parallel. He also wanted some feedback, so he used Atmega8, which drives an LCD. Microcontroller ADC takes voltage and current readings and displays them on the screen. He uses a shunt resistor to read the voltage drop from the current. Few buttons also allow controlling relay, selecting serial data output, and doing other tasks—interesting choice of the enclosure made of the plastic container.