This is the circuit diagram of a dual adjustable power supply using IC’s LM 317 & LM 337.LM 317 is able to deliver a maximum of 1.5 A at a range of 1.2 V to +30V .LM 337 is the negative complement of LM317.They also have a built in short circuit protection.

Here the circuit is wired to produce a dual adjustable output of ( +15 , 0 , -15 ).The capacitors C1 to C8 provides filtering and ripple rejection.Resistors R1 & R2 controls output of LM 317.Resistors R3 & R4 controls the output of LM 337 .R1 and R4 can be turned to vary the positive and negative voltages.This circuit is a must on an electronic hobbyists workbench.Notes

The transformer should be anything that produces a min of 3 A with (24 0 24 ) output voltage. The voltage range can be further increased by increasing transformer output within the limits of IC. Do not connect a load drawing more than 2A at output.The IC,s must be fitted with heat sinks for better protection.

Parts List

C1, C2 2200 uF 50V Electrolytic CapacitorC3, C4, C5, C7 2.2 uF 50V Electrolytic CapacitorC6, C8 100 uF 50V Electrolytic CapacitorR1, R4 5K PotentiometerR2, R3 220 Ohms 1/4 W ResistorD1 to D4 IN 4007 DiodesU1 LM317 U2 LM337 T1 24 0 24 Center Tapped 2 Ampere TransformerS1 SPST 2 Ampere SwitchExtra Heat sinks for two IC’s , Power Cord, Casing, Wire etc