Project Hub /Basic Analog & Power Electronics/Power Supplies & Voltage Regulators/Variable Power Supply For Up To 3A Current

Intermediate

ANALOG / DISCRETE

₹500 – ₹1,500

3 – 6 Hours

Partial Kit

Variable Power Supply For Up To 3A Current

A variable power supply circuit capable of delivering up to 3A of current for 5V, 6V, 8V, or 9V outputs using an LM317 regulator and a TIP127 PNP transistor.

Originally published on ElectronicsForU

View original tutorial

Parts You'll Need

This project is sourced from another site, not written by us — this list is our best match of their components against what we stock, not a verified bill of materials. Always check the original blog (linked above) for the actual parts list before buying.

LM2596 Step Down DC-DC Buck Converter Rs. 99.00
10pcs 5mm RED Diffused Light Emitting Diodes - LEDs Set Rs. 39.00
10pcs - 220 ohm 1/4 W Resistor Set Rs. 39.00
DC Motor Plastic Fan Blade Rs. 19.00
400 Points Mini Solderless Prototype PCB Breadboard High Quality Rs. 89.00
MB102 Adjustable Breadboard Power Supply Module (3.3V & 5V) for Arduino & Raspberry Pi Rs. 139.00
Jumper Wire 10 Pin Male To Male 20cm Rs. 45.00
Jumper Wire 10 Pin Male To Female 20cm Rs. 45.00

Selected: Rs. 0.00

This list includes a generic resistor set as a placeholder — it is not matched to the exact value or part number this circuit needs. The correct one is specified on the original source page linked above; check it before buying.

We don't carry yet: Diodes (1N4007 / 1N4148 / Schottky / Zener)
Transistors (BC547 / 2N2222 / TIP / MOSFET)
Voltage Regulator IC (7805 / LM317 / 1117)
9V Battery + Snap
Potentiometer / Trimpot
DC digital panel meter

Browse all components

How It Works

This variable power supply circuit steps down an AC mains voltage using a step-down transformer, which is then converted into pulsating DC using a bridge configuration of 1N5408 rectifier diodes. The LM317 adjustable voltage regulator IC1, working alongside a potentiometer VR1 and a 22-ohm 2W resistor R1, controls the target output voltage level. Because standard adjustable regulators have limited output current capabilities, a TIP127 PNP transistor T1 is integrated into the design to boost the total delivery capacity up to 3A, allowing the supply to handle heavier loads for outputs like 5V, 6V, 8V, or 9V. A separate 9V voltage regulator IC2 provides a stable auxiliary voltage line, while an LED indicator shows when the system is powered on. A DC digital panel meter (DPM) displays real-time voltage readings to the user. Because regulating high currents creates significant thermal energy, both the LM317 and the TIP127 transistor require properly sized heatsinks paired with an exhaust fan to dissipate excess heat and maintain safe operating temperatures.

Why Build This

Create a reliable, adjustable benchtop power supply for testing and prototyping electronic circuits and DIY hardware projects.

Practice designing intermediate power regulation circuits capable of delivering up to 3A of continuous current.

Gain hands-on experience handling thermal management challenges in linear power supplies using heatsinks and active cooling fans.

Real-World Application

Benchtop power supply for testing electronic circuits, prototyping, and powering various DIY hardware projects requiring adjustable low voltages up to 3A.

Skills You'll Learn

Linear power supply design

AC to DC rectification

transistor current boosting

voltage regulation

thermal management and heatsinking

panel meter integration

Safety Precautions

Ensure proper heatsinks are attached to the LM317 and TIP127 transistors along with an exhaust fan for cooling, as handling mains voltage (230V AC) requires caution.

Technology Tags

LM317

TIP127

VOLTAGE REGULATOR

POWER SUPPLY

TRANSISTOR

RECTIFIER DIODES

HEAT MANAGEMENT

Frequently Asked Questions

Why is a TIP127 transistor used alongside the LM317?

The TIP127 acts as a current booster, allowing the circuit to supply up to 3A of current safely without overloading the LM317 regulator.

Do I really need heatsinks and an exhaust fan?

Yes. Linear voltage regulation at higher current levels generates considerable heat, which can damage the LM317 and TIP127 if not properly dissipated.

What is the purpose of the 1N5408 diodes?

The four 1N5408 diodes form a bridge rectifier that converts the incoming AC voltage from the step-down transformer into usable DC power.

Gallery

This page is part of Kitkraft's Project Hub — a curated collection of electronics & robotics projects gathered from the maker community to help students and hobbyists discover and learn to build. Kitkraft does not claim authorship of the original project, and makes no representation as to the accuracy, completeness or safety of third-party source material. The summary and "How It Works" explanation above are AI-generated, rewritten with reference to the original tutorial — not a reproduction of it. Full credit and a direct link to the original source are provided above. If you're the original creator and have a concern about how your work is represented here, please contact us and we'll address it promptly.

Kitkraft Project Hub — curated from the maker community, credited at the source.

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