One of the problems taken into account when designing electronic circuits is to choose the correct values for the different components. Failed attempts are often made to find the most convenient value for a test circuit.
How does the project work?
This circuit acts as a source of variable voltage between 3 and 25V, which can be easily inserted in any test project. The voltage can be varied with the help of the semi-adjustable POT potentiometer.
List of required components:
1 x Breadboard test board + connecting wires
1 x semi-adjustable POT = 200k
1 x R1 = 10k
1 x R2 = 10k
1 x R3 = 10k
1 x R4 = 10k
1 x T1 = BC547
1 x T2 = BC557
1 x Terminal contact
For a better understanding of the circuit's functionality and to make this assembly on the breadboard we will need the electronic diagram presented below:

Download the manual and the electronic diagram
To carry out this project in your own laboratory, download the manual here and electronic schema in .dsn format (TinyCAD design) by here.
Also for this application is available the following video material in which a similar functionality is presented: