DIY Power Supply

Introduction

Building a DIY power supply is an essential project for anyone interested in electronics. This guide will walk you through designing a power supply that converts 240V AC to a stable 12V DC output and further steps down to 5V and 3.3V for powering microcontrollers, sensors, and other devices. With clear schematics, step-by-step instructions, and waveform analysis, you’ll learn how to create a reliable power source for various projects. Whether you’re a beginner or an experienced hobbyist, this DIY power supply tutorial offers practical insights to help you succeed.

Materials Required

• 12-0-12V Center-Tap Transformer
• Bridge Rectifier (KBP310) (MB10F)
• Voltage Regulator (LM7812)
• Filter Capacitor: 100 µF, 16V (for smoothing)
• Oscilloscope (for waveform analysis)

Circuit Design: Unsmoothed 12V DC Supply

1. Step 1: Use a 12-0-12 transformer to step down 240V AC to 12V AC.
2. Step 2: Connect the transformer’s secondary winding to the AC inputs of the KBP310 bridge rectifier.
3. Step 3: Connect the output of the rectifier to the input of the LM7812 voltage regulator.
4. Step 4: Connect the ground pin of the LM7812 to the transformer’s center tap and take the regulated 12V DC output.

Smoothed 12V DC Supply

1. Step 1: Follow steps 1–4 from the unsmoothed supply design.
2. Step 2: Add a 100 µF capacitor across the output of the LM7812 for smoothing.

Schematic: Refer to the second schematic labeled “12V supply (smoothed).”

Waveform Analysis

• Unsmoothed Output: The waveform shows significant ripples due to the lack of a filtering capacitor.
• Smoothed Output: After adding the capacitor, the ripples are significantly reduced, resulting in a cleaner DC waveform.

Graphs:
Observe the provided oscilloscope outputs for the unsmoothed and smoothed configurations.

Testing and Verifying Performance (Exercise)

• Use a multimeter to measure the output voltage (12V DC).
• Connect an oscilloscope to visualize the waveform at different stages (rectified and smoothed outputs).
• Load Test: Connect a 12V load (e.g., a motor or LED strip) to verify stability under real-world conditions.
• The IC’s used here are old as well as have low current/power rating take that into consideration and use regulators rectifier IC accordingly.
• Try to make your DIY power supply without IC and check its footprint and other factors

Try our calculators

Part 2: AC to 5V and 3.3V DC Conversion

Introduction

• After obtaining a 12V DC output, stepping down to 5V and 3.3V is essential for powering microcontrollers and sensors.
• This section uses the LM7805 (5V) and LM1117-3.3 (3.3V) voltage regulators.

Materials Required

Voltage Regulators: LM7805, LM1117-3.3

• Filter Capacitors: 100 µF and 0.1 µF for input/output stability
• 12V DC Source: Output from Part 1

Circuit Design

• Step 1: Connect the 12V DC input to the voltage regulators.
• Step 2: Add filtering capacitors (100 µF) output sides of regulator.
• Step 3: Use the LM7805 for a stable 5V DC output and LM1117-3.3 for a stable 3.3V DC output.

Schematic: Refer to the schematic labeled “240V AC to 5V & 3.3V DC.”

Waveform Analysis

• After regulation, the output is a clean DC signal with no visible ripples.
• Use an oscilloscope to confirm the stability of the 5V and 3.3V outputs under load.

Testing and Verifying Performance (Exercise)

• Measure the output voltages (5V and 3.3V) using a multimeter.
• Load Test: Connect a microcontroller or LED to verify the stability of the regulated outputs.
• Ensure the regulators remain cool; add heatsinks if necessary.
• The IC’s used here are old as well as have low current/power rating take that into consideration and use regulators rectifier IC accordingly.
• Try to make DIY power supply without IC and check its footprint and other factors

Real-Life Applications

• 12V DC Output: Suitable for motors, LED strips, and general-purpose power supplies.
• 5V and 3.3V Outputs: Ideal for Arduino, ESP32, and other low-power devices.

Note:- The output graph are under no load conditions, hence it is necessary to do analysis under load and choose appropriate regulators and rectifiers according to load necessity, but this schematic will help you to understand various insights about power supply.

Conclusion

• This guide demonstrates the use of a 12-0-12 center-tap transformer for efficient AC to DC conversion.
• By adding filtering and regulation stages, you can achieve clean 12V, 5V, and 3.3V outputs for various applications.
• The provided schematics and waveform analysis ensure a practical understanding of the circuit.
• Encourage experimentation and customization based on project needs.