Regulated power supply or variable power supply are most common electronic devices that every electronic engineer or hobby electrician must have. Today you can buy lot of power supplies but their can be expensive. So in this steps I will explain you how variable power supply works, put some schematics and components so you can make it yourself! Enjoy :)
Step 1: Regulated Power Supply With LM317 or LM338
This is schematics of LM317 or LM338 regulated power supply. This ICs are not so efficient but they are good for our projects and uses.
C1, C2 and C3 are capacitors in rectifier section. C1 and C2 are for smoothing the voltage. C3 is for stability for high currents and frequency. Diodes D1 and D2 are for discharging capacitors. They prevent discharging capacitors into IC. Potentiometer R1 is 10k multi turn. C4 is for better ripple rejection and better stability for ADJ pin. C5 is for stability for high currents and frequency.
C1, C2 = 4700uF 50V electrolitic
C3 = 0.1uF tantalum 50V or ceramic
C4 = 10uF 50V electrolitic
C5 = 0.1uF tantalum 50V or ceramic
R1 = 10kΩ multi-turn potentiometer
R2 = 220Ω 1/2W 0,5% metal film
D1, D2 = 1N4004 ili 1N4007
IC1 = LM317 ili LM338
B1 = 5A rectifier