3V DC power supply circuit

Most of the Electronic Components, Microcontroller and some sensors requires 3V Direct Current (DC) Supply with constant Regulation. When we put additional components to the main power source then there will be a chance to excessive load occurrence. If the power source is capable then its okay. Here 3V DC power Supply circuit designed by using IC LM317 to give Regulated constant 3 volt DC power supply.




This Simple 3V DC Voltage Regulator circuit can be used in any circuit or device that requires constant 3V DC supply. Here this circuit converts 230V AC to 3V DC with the help of Stepdown transformer, Bridge Rectifier and Voltage Regulator IC LM317.

Circuit Diagram

Components Required (BOM)

S.NoDesignatorValuePart NumberQuantity
1TR1230V to 0-6V AC0-6V Stepdown Transformer1
2C1
C2
10µF/10V
0.01µF
Electrolytic
Disc capacitor
1
1
3R1
R2
330Ω/0.5W
470Ω/0.5W

1
1
4D1Bridge Rectifier Module1
5LED1, LED2Red, Greeneach one
6U1LM317LM317_TO-2201

Construction & Working

This Circuit designed to convert 230V AC to 3V DC, As we know in order to obtain low voltage from high voltage AC we need to use Stepdown transformer. Here 230V AC to 6V AC output Stepdown transformer used. 6V AC supply from secondary winding of stepdown transformer is directly applied to the Bridge Rectifier module, you can use either bridge rectifier module or four 1N4007 diodes in bridge rectifier form. Here the 6V AC Converted into 6V DC supply then this unfiltered DC applied to the filter capacitor C1 and then filtered DC applied to the Regulator IC LM317 (Package To-220) this IC has three terminals, terminal 1 (Adjust) and terminal 2 (output) are connected with feedback Resistor R1 and R2, by Varying these two Resistors value we can get our desired output voltage from 1.25V to 37V (if we apply enough input voltage to the terminal 3) and output current up to 1.5 Amps.

We Can Calculate Output Voltage of LM317 as,

For this Circuit,

Vout = 1.25(1+ (470/330))

Vout = 3.0V

After filter Capacitor C2, We can get Constant Regulated 3.0V DC supply as output. For Standalone Circuits, you can use LED indicator to know the Input voltage and Output voltage Status.

LM317

LM317 is a three terminal Adjustable Voltage Regulator Capable of Supplying up to 1.5 Amps output current and 1.25 to 37 Output voltage.

Pin Configuration of LM317

Most Interesting thing about this Regulator is we just need two external Resistors to Adjust the output voltage. This Regulator gives good voltage Regulation and current limiting and also thermal overload protection.

Datasheet of LM317.




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