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Earth Bondhon
Last updated: Jun 12, 2026

Adjustable Voltage Regulator Project

Learn how to make an adjustable voltage regulator using LM317 or LM338. Perfect for DIY electronics projects requiring a variable DC output voltage.

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Components List

TIP41C Transistor

TIP41C Transistor

NPN power transistor with high current (6A) & voltage (100V) ratings

50K Fixed Resistor

50K Variable Resistor

Adjustable resistor with 50,000 ohm resistance

6.8R Fixed Resistor 5W

6.8R Fixed Resistor 5W

A 6.8-ohm resistor rated for 5 watts

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Adjustable Voltage Regulator Project

Learn how to make an adjustable voltage regulator using LM317 or LM338. Perfect for DIY electronics projects requiring a variable DC output voltage.

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Simple variable voltage circuit

A Voltage adjustable circuit is one of the easiest and effective methods of regulating the output voltage of a power supply. It is common in electronic laboratories and Do-It-Yourself projects as a means of providing power to other devices that need a different amount of voltage. The circuit schematic is usually constructed with an LM317 adjustable regulator so the output can vary anywhere between 1.25V to up to 30V, depending on what input and resistor combinations are hooked up.

variable voltage diy kit Formula:

  • Output Voltage: Vout = 1.25 × (1 + R2/R1) + Iadj × R2
  • R1: Typically 240Ω
  • R2: Adjustable resistor or potentiometer
  • Input Voltage: Minimum 3V higher than desired output
  • Capacitors: Cin = 0.1µF, Cout = 1µF or more
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adjustable voltage regulator project

A voltage adjustable circuit is made to adjust the output voltages over a range best suited for testing, prototyping, and a variable power supply. The components that are incorporated in this project generally include variable resistors (potentiometers), LM317 or LM338 regulators, capacitors, and heat sinks so that adjustable results can be handled in a reliable and efficient manner. The users can adjust resistance in the circuit by rotating the potentiometer and affecting the output voltage. It has many applications in self-construct projects, charging batteries, and power management customized set-ups.

diy variable power supply

R1 (Ω) R2 (Ω) Output Voltage (V)
240 470 3.7
240 1000 6.5
240 1800 10.6
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Frequently Asked Questions - Adjustable Voltage Regulator Project:

It is a circuit that allows output voltage control using components like LM317.
LM317 is widely used for 1.25V to 37V output range.
Yes, a potentiometer is used as R2 in the voltage divider.
Typically 3V to 40V depending on the application.
Yes, if output current exceeds 500mA, a heatsink is recommended.
A small adjustment pin current, often neglected in calculations.
It provides ±1.5% voltage accuracy under typical conditions.
Yes, but with current limiting and careful design.
Input and output capacitors improve stability and filtering.
Yes, LM338 handles up to 5A with proper heatsinking.
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