0.7V - 24V DC Variable Power Supply Circuits >>

Voltage range: 0.7 - 24V
Current limiting range: 50mA - 2A

Parts:

P1____________500R   Linear Potentiometer
P2_____________10K   Log. Potentiometer

R1,R2___________2K2  1/2W Resistors
R3____________330R   1/4W resistance
R4____________150R   1/4W resistance
R5______________1R     5W resistance

C1___________3300µF   35V capacitance (see Notes)
C2______________1µF   63V Polyester electrical device

D1,D2________1N5402 200V 3A Diodes
D3_____________5mm. Red LED

Q1____________BC182  50V 100mA NPN semiconductor unit
Q2____________BD139  80V one.5A  NPN semiconductor unit
Q3____________BC212  50V 100mA PNP semiconductor unit
Q4 __________2N3055  60V 15A   NPN semiconductor unit

T1_____________220V Primary, 36V Center-tapped Secondary
               50VA Mains electrical device (see Notes)

PL1____________Male Mains plug

SW1____________SPST Mains switch
Device purpose:

A Variable DC Power offer is one in all the foremost helpful tools on the physical science hobbyist's work table. This circuit isn't Associate in Nursing absolute novelty, however it's straightforward, reliable, "rugged" and short-proof, that includes variable voltage up to 24V and variable current limiting up to 2A. compatible to produce the circuits shown during this web site. you'll be able to adapt it to your own necessities as explained within the notes below.

Notes:

• 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.
• 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.
• 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.
•  Electronics Circuit Application