In many of the project applications and testing applications, Variable DC Power supplies are used. Sometimes it happens that one can not find an AC power socket nearby testing circuit. Also, Power supplies are usually AC powered and are bulky, because of their voltage transformers, to bring anywhere near testing circuit or equipment. Hence, Portable Variable DC Power Supply is required which helps people become mobile in doing electronic projects that will need power supplies.
This project uses a voltage regulator and a potentiometer that allows the user to change the output voltage between 2 volts to 25 volts. It is also equipped with a small seven segment display which acts a voltage meter which lets the user to know how much voltage is being supplied by the regulator. Powered by a 9V battery, this project gives mobility in making circuit projects. It also includes a banana jack that accommodates plugs that can help attach it to different applications.
Source: Portable Variable Power Supply