Quezon City University

College Of Engineering
Electronics Engineering Department
AY 2024-25, 2nd Semester

Project: ADJUSTABLE 0-30 V, 10 A REGULATED POWER SUPPLY

Submitted by:

Group No: 1

Leader:

Fernandez, Yves P.

Members:

Alayon, Marc Daniel C.

Fostanes, Caesar Julius C.

Ramirez, Jose Mari R.

Santiago, Joanna Mae F.

Submitted to:

Engr. Leonard A. Catchillar

Comments Particulars

___________________________________ Min Req’ts:_______________________

___________________________________ Data:____________________________

___________________________________ Analysis:_________________________

___________________________________ Conclusions:______________________
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I. Objectives

This project aims to design and construct a regulated DC power supply capable of delivering
an adjustable output voltage from 0V to 30V and a maximum current of 10A. The power supply
should provide stable and noise-free DC output for various electronic applications, including
circuit testing and powering devices requiring high current.

The main objectives are:

1. To apply the principles of voltage regulation, rectification, and current amplification in

designing a high-power adjustable power supply.
2. To analyze the performance and efficiency of the power supply under different
electrical loads.
3. To ensure thermal stability and protection mechanisms to prevent overheating and
component failure.
4. To construct the power supply using PCB fabrication techniques for efficient circuit
assembly.
5. To evaluate the accuracy and reliability of the digital voltmeter display in providing
real-time voltage readings.

II. Conceptual Framework

A reliable power supply is a fundamental component in electronics, ensuring that circuits

receive a stable and regulated voltage. This project focuses on designing an adjustable linear
power supply capable of converting AC mains voltage into a stable DC output with adjustable
voltage levels. The conceptual framework is based on key electrical engineering principles,
including rectification, voltage regulation, current amplification, and thermal management (Sedra
& Smith, 2020).

The first stage of the power supply design involves transforming the AC mains voltage
into DC using a step-down transformer, rectifier, and filtering capacitor (Boylestad & Nashelsky,
2019). A 30V 10A transformer steps down the AC voltage, which is then converted into pulsating
DC by a 10A bridge rectifier. A 4700µF capacitor smooths out voltage ripples, providing a stable
DC output.

To ensure a stable and adjustable voltage, an LM317 voltage regulator is used, allowing
the output voltage to vary from 0V to 30V via a 10k potentiometer. Additionally, an L7805
regulator provides a fixed 5V output for control circuits and accessories (Malvino & Bates, 2022).
This regulation mechanism ensures a consistent power supply to different electronic
components.

The BD139 transistor acts as a driver for 2N3055 power transistors, which amplify the
current to provide a maximum of 10A output. This configuration ensures efficient current
handling and prevents excessive voltage drops across the regulator (Floyd, 2021). With effective
current amplification, the power supply can sustain high-current loads without significant
fluctuations.

To prevent thermal failure, heat dissipation is managed using a large heatsink attached
to the 2N3055 transistors. A 1Ω 5W resistor is integrated into the circuit to limit current surges
and improve overall stability (Theraja & Theraja, 2018). Effective thermal management ensures
the longevity and reliability of the power supply unit.
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A digital voltmeter is incorporated to provide real-time monitoring of the output voltage,

ensuring precise adjustments and safe operation. Banana plug connectors serve as secure
interfaces for external devices, facilitating efficient connectivity (Alexander & Sadiku, 2017). By
integrating real-time monitoring, the power supply guarantees operational accuracy and user
control.

This conceptual framework provides a systematic approach to designing a robust adjustable

power supply. By integrating AC-to-DC conversion, voltage regulation, current amplification,
thermal management, and real-time monitoring, the project ensures a reliable and efficient
power source for electronic applications.

III. List Of Materials / Tools/ Equipment

Electronic Materials Quantity

30V 10A Transformer (AC To AC Conversion) 1

10A Bridge Rectifier Diode (AC To DC Rectification) 1

4700µF 50V Capacitor (Ripple filtering) 1

LM317 Adjustable Voltage Regulator 1

L7805 Fixed Voltage Regulator 1

BD139 Transistor (Current Amplification) 1

2N3055 power transistors (High current handling) 2

0.1µF 104J 83V polypropylene film capacitor (Noise suppression) 1

1Ω 5W resistor (Current limiting) 1

10k Multiturn Trim potentiometer (Voltage adjustment) 1

5k Multiturn Trim potentiometer (Current control) 1

Digital voltmeter (Real-time output monitoring) 1

Banana plugs connectors (Output terminals) 1

Construction Materials Quantity

Printed Circuit Board (PCB) 1

Etching solution 1

Black acrylic for casing 4

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Soldering iron and solder wire 1

Heatsink 1

Drill and Cutting Tools 1

IV. METHODOLOGY

This section details the systematic approach employed in designing, fabricating, assembling,
and evaluating the 0-30V, 10A adjustable power supply. Each phase was meticulously executed
to ensure optimal circuit performance, reliability, and safety.

1. Component Selection and Procurement

• Identified and specified all necessary electronic components, tools, and materials
required for the project.
• Conducted an evaluation of alternative components to optimize efficiency, thermal
management, and overall circuit performance.

2. Circuit Design and Schematic Development

• Created the circuit schematic through manual drafting and subsequently refined it using
Canva for digital traceability and accuracy.
• Conducted a thorough validation of the schematic to ensure design integrity prior to PCB
layout implementation.

3. PCB Layout Design and Transfer

• Designed the PCB layout in accordance with the finalized schematic, ensuring optimal
component placement to minimize signal interference and enhance thermal dissipation.
• Printed the PCB layout onto glossy paper using a laser printer for precise toner transfer.
• Employed the toner transfer method or UV exposure technique to imprint the circuit onto
a copper-clad board, ensuring accurate alignment and track definition.

4. PCB Etching and Preparation

• Prepared an etching solution using Ferric Chloride to selectively remove excess copper,
leaving only the conductive traces.
• Thoroughly rinsed, dried, and cleaned the PCB post-etching to eliminate residual
chemicals.
• Drilled precise component mounting holes using a high-speed rotary tool to facilitate
secure soldering and connectivity.

5. Component Soldering and Assembly

• Sequentially soldered components onto the PCB, beginning with low-profile passive
components (resistors, capacitors, diodes) followed by larger active components
(transistors, voltage regulators, and connectors).
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• Ensured robust solder joints, eliminating potential defects such as cold joints or solder
bridges.
• Trimmed excess lead lengths to prevent electrical shorts and maintain circuit integrity.

6. Electrical Connectivity and Functional Testing

• Conducted a preliminary inspection of PCB connections using a multimeter to verify
continuity and detect potential short circuits.
• Validated voltage regulation functionality across the 0V to 30V range while assessing the
circuit’s ability to handle up to 10A of current.
• Adjusted potentiometers to fine-tune voltage output and ensure smooth control variability.

7. Enclosure Fabrication and Final Assembly

• Designed and fabricated a custom black acrylic enclosure to provide structural protection
and heat dissipation.
• Precision-drilled ventilation holes and mounting points for the voltmeter display, output
terminals, and control interfaces.
• Securely mounted the PCB within the enclosure, ensuring mechanical stability and ease
of maintenance.
• Implemented clear labeling for user interface elements to enhance accessibility and
usability.

8. System Validation and Performance Evaluation

• Verified the operational integrity of switches, indicators, and external interface
components.
• Performed load testing to assess the power supply’s stability, efficiency, and thermal
response under varying electrical loads.
• Documented performance metrics to confirm compliance with the design specifications.

V. Electronic Circuit Set-Up

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Figure 1. Schematic Diagram

Figure 2. PCB Layout

VI. Data And Results

The power supply was tested under different load conditions, and the following results were recorded:
• Voltage Stability: The output voltage was adjustable from 0.2V to 30.1V, maintaining a
±0.3V accuracy across the range.
• Ripple Voltage: Measured ripple voltage remained below 50mV peak-to-peak, ensuring a
clean DC output.
• Thermal Performance: The 2N3055 transistors reached a maximum temperature of 64°C
under a 9A load, with the heatsink effectively dissipating heat.
• Digital Voltmeter Accuracy: Displayed output voltage with a deviation of ±0.2V from
multimeter readings.
• Load Handling: The power supply successfully delivered 10A at 12V, 15V, and 24V,
maintaining stability without significant voltage drops.

VII. Observations

• The digital voltmeter displayed accurate voltage readings without noticeable lag.
• Transistors heated up under high current loads, emphasizing the need for an efficient
cooling system.
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• The ripple voltage remained low, confirming the efficiency of capacitor filtering.
• The power supply-maintained stability, even under varying loads.

VIII. Analysis

• The LM317 and L7805 regulators effectively controlled the output voltage.
• The current amplification system (BD139 and 2N3055 transistors) performed well in
providing high current.
• The voltage ripple was negligible, indicating effective capacitor filtering.
• The heat dissipation system worked adequately, but a cooling fan may improve
performance under continuous high-load conditions.

IX. Conclusion

In conclusion, this project successfully achieved its objective of designing and constructing a
regulated DC power supply that delivers an adjustable output voltage from 0V to 30V with a
maximum current of 10A. By applying the principles of voltage regulation, rectification, and
current amplification, the design met the requirements for stable and noise-free DC output,
making it suitable for various electronic applications, including circuit testing and powering high-
current devices. The power supply’s performance was thoroughly analyzed, demonstrating
efficient operation under different electrical loads. Additionally, thermal stability was ensured
through effective heatsinking, preventing overheating and component failure. The use of PCB
fabrication techniques streamlined the circuit assembly, and the digital voltmeter provided
accurate real-time voltage readings, further validating the system’s reliability and precision.
Overall, the project not only met the specified objectives but also delivered a highly functional
and dependable power supply for diverse applications.

X. Recommendations

It is recommended that future iterations should incorporate active cooling, like a fan, to
prevent thermal overload during high-current use. Replacing 2N3055 transistors with MOSFETs
would improve efficiency and reduce heat loss. Adding an ammeter to the digital display enables
real-time current monitoring. Lastly, overload protection (fuses or circuit breakers) would
enhance safety and reliability.

XI. References

Alexander, C. K., & Sadiku, M. N. O. (2017). Fundamentals of Electric Circuits (6th ed.).
McGraw-Hill Education.

Boylestad, R. L., & Nashelsky, L. (2019). Electronic Devices and Circuit Theory (12th ed.).
Pearson.

Floyd, T. L. (2021). Electronic Devices (Conventional Current Version) (11th ed.). Pearson.

Malvino, A. P., & Bates, D. J. (2022). Electronic Principles (9th ed.). McGraw-Hill Education.
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Sedra, A. S., & Smith, K. C. (2020). Microelectronic Circuits (8th ed.). Oxford University Press.

Theraja, B. L., & Theraja, A. K. (2018). A Textbook of Electrical Technology (Vol. 1). S. Chand
Publishing.

Documentation: