Power005

                                          

Variable DC Power Supply
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Schematic design of Variable DC Power Supply
Technical Data
Input voltage:.................36, 40 or 48 V center-tapped Input current:.............................500 mA (max) Output voltage:...................0.7 - 240 V (adjustable) Output current:..................50 mA - 2 A (adjustable)
Part of Components:
Capacitors	Resistors
C1      = 3300 μF / 35V Electrolytic C2      =      1 μF / 63V Polystyrene Diodes D1,D2 = 1N5402 (2A Diodes) D3      = LED 5mm Red Others T1 Mains transformer : 220V Primary., 36V Center- tapped Secondary 50VA.  PL1      = Male mains plug SW1    = SPST Mains switch	R1,R2 = 2K2 Ω ½W R3      =  330 Ω ¼W R4      =  150 Ω ¼W R5      =      1 Ω 5W P1      =   500 Ω Lin. Potentiometer P2      =  10 KΩ Log. Potentiometer Transistors Q1      = BC182 Q2      = BD139 Q3      = BC212 Q4      = 2N3055
Notes
A Variable DC Power Supply is one of the most useful tools on the electronics hobbyist's workbench. This circuit is not an absolute novelty, but it's simple, reliable, "rugged" and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A. It's well suited to supply the circuits shown in this website. P1 sets the maximum output current you want to be delivered by the power supply at a given output voltage.  P2 sets the output voltage and must be a logarithmic taper type, in order to obtain a more linear scale voltage indication.  Capacitor C1 can be 2200 to 6800μF, 35 to 50V. Q4 must be mounted on a good heatsink in order to withstand sustained output short-circuit. In some cases the rear panel of the metal box in which you will enclose the circuit can do the job. The 2N3055 transistor (Q4) can be replaced with the slightly less powerful TIP3055 type. You can choose the Transformer on the grounds of maximum voltage and current output needed. Best choices are: 36, 40 or 48V center-tapped and 50, 75, 80 or 100VA.

Source : Electronics Lab