The Blue LED can be kept as an indicator for positive power and Red indicator can be kept as an indicator for negative power. A Blue LED can be connected across U1 and GND and a Red LED can be connected across U2 and GND.
If needed two LED indicators can also be connected to indicate the positive and negative power outputs. This circuit is a must on an electronic hobbyists workbench. R1 and R4 can be turned to vary the positive and negative voltages. Resistors R3 & R4 controls the output of LM337. Resistors R1 & R2 controls output of LM317. The capacitors C1 to C8 provides filtering and ripple rejection. Here the circuit is wired to produce a dual adjustable output of ( +15, 0, -15 ). They also have a built in short circuit protection. These IC’s also have a special TO3 package and if assembled with a large heat sink (HS07051 preferably), the power supply can be designed to handle load current to its max. The LM317 IC is a 3-terminal voltage regulator that is designed to supply in excess of 1.5 Amps of a DC output voltage range of (1.2-30) Volts. LM317 is a positive voltage regulator and LM337 is the negative compliment voltage regulator IC of LM317. LM317 is able to deliver a maximum of 1.5 A at a range of 1.2 V to +30V. This is the circuit diagram of a dual adjustable power supply using IC’s LM 317 & LM 337. The aim of the dual adjustable power supply circuit is to provide power for other projects that require a dual (+/-) adjustable power supply. The power supplies that we are going to discuss are more discrete and are useful for simple projects and minor electrical applications.
In such devices the power supply unit is inbuilt along with their loads.
Power supplies are used in everyday consumer devices and PC’s. Power supplies can also be named as electric power converters as they are used to convert electrical energy from one form to another. A power supply is a circuit based electronic device that supplies the needed electrical energy to an electrical load.
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