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A compact single-sided 5V regulated linear power supply designed using KiCad 9 and built around the LM7805 voltage regulator.
This project was developed as part of my PCB design learning journey to gain hands-on experience with the complete hardware development workflow—from schematic capture and PCB layout to electrical verification, 3D visualization, Gerber generation, and project documentation.
In addition to PCB design, this project demonstrates the basic design principles of a regulated linear power supply, including rectification, filtering, voltage regulation, and component selection.
The primary objective of this project was to learn professional PCB design using KiCad 9 while designing a simple regulated power supply suitable for educational and low-power embedded applications.
Although the electrical circuit is based on the widely used LM7805 linear voltage regulator, the project focuses on understanding the complete PCB development process, including:
The completed board is designed as a single-sided through-hole PCB, making it easy to assemble, inspect, and understand for students, beginners, and electronics hobbyists.
The project was developed with the following objectives:
| Parameter | Value |
|---|---|
| Input Supply | 9V AC Transformer |
| Rectifier | Full-Wave Bridge Rectifier |
| Output Voltage | 5V DC |
| Maximum Output Current | 500 mA |
| Voltage Regulator | LM7805 |
| Main Filter Capacitor (C1) | 3300 µF |
| Input Bypass Capacitor (C2) | 0.33 µF |
| Output Bypass Capacitor (C3) | 0.1 µF |
| PCB Type | Single-Sided |
| Mounting Style | Through-Hole (THT) |
| PCB Design Software | KiCad 9 |
| Routing | Manual |
| Ground Plane | Copper Pour |
| Manufacturing Files | Gerber |
The following assumptions were used during the design of this project:
These assumptions are important because component selection, filtering, thermal performance, and regulator operation depend on the expected load conditions.
The circuit converts a 9V AC input into a regulated 5V DC output through four main stages:
A full-wave bridge rectifier converts the incoming AC voltage into pulsating DC.
A 3300 µF electrolytic capacitor (C1) smooths the rectified voltage by reducing ripple before it reaches the voltage regulator.
This larger capacitor was selected to improve ripple performance for the intended 500 mA maximum output current.
An LM7805 linear voltage regulator provides a stable 5V DC output over a range of load conditions.
The regulator includes internal:
making it suitable for educational and low-power applications.
To improve regulator stability, two ceramic bypass capacitors are placed close to the LM7805:
These capacitor values follow the recommendations provided in the LM7805 datasheet and help suppress high-frequency noise while improving transient response.
| Component | Quantity | Purpose |
|---|---|---|
| LM7805 Voltage Regulator | 1 | Regulates the output to a stable 5V DC |
| Bridge Rectifier | 1 | Converts AC input into pulsating DC |
| 3300 µF Electrolytic Capacitor (C1) | 1 | Smooths the rectified voltage and reduces ripple |
| 0.33 µF Ceramic Capacitor (C2) | 1 | LM7805 input bypass capacitor for stability |
| 0.1 µF Ceramic Capacitor (C3) | 1 | LM7805 output bypass capacitor for stability |
| 330 Ω Resistor | 1 | Limits LED current |
| 2-Pin Screw Terminal | 2 | Input and output power connections |
The LM7805 is a widely used linear voltage regulator capable of providing a regulated 5V output with minimal external components. It also includes built-in thermal shutdown and current limiting, making it an excellent choice for beginner-friendly power supply designs.
The bridge rectifier converts the incoming 9V AC into pulsating DC, allowing the regulator to operate from a transformer-based AC supply.
The large electrolytic capacitor significantly reduces ripple voltage after rectification.
For the intended 500 mA load, a higher capacitance improves voltage smoothing and helps maintain sufficient input voltage for proper LM7805 regulation.
These capacitors are placed close to the regulator input and output pins to improve high-frequency filtering and regulator stability.
The screw terminals provide secure and reusable connections for both the AC input and regulated DC output.
Although this project was primarily created to learn PCB design, several engineering considerations were incorporated to improve the reliability and stability of the power supply.
The design follows the typical architecture of a linear regulated power supply:
9V AC
│
Bridge Rectifier
│
3300 µF Filter Capacitor
│
0.33 µF Bypass Capacitor
│
LM7805 Voltage Regulator
│
0.1 µF Bypass Capacitor
│
5V DC Output
Each stage performs a specific function to convert the AC input into a clean and regulated 5V DC output.
The circuit is designed to operate from a 9V AC transformer.
The peak voltage after rectification can be approximated as:
Vpeak = VAC × √2
For a 9V AC input:
Vpeak ≈ 9 × 1.414
≈ 12.7 V
After accounting for the voltage drop across the bridge rectifier (approximately 1.4V), the capacitor charges to approximately:
VDC ≈ 11.3 V
This provides sufficient input voltage for the LM7805 to regulate the output to 5V.
After rectification, the voltage contains ripple.
A large electrolytic capacitor stores energy between the peaks of the rectified waveform, reducing ripple voltage before the regulator.
For this design, a 3300 µF capacitor was selected.
Compared to smaller values, the larger capacitance provides:
Two ceramic capacitors are used near the LM7805.
Value:
0.33 µF
Purpose:
Value:
0.1 µF
Purpose:
Both capacitors are placed as close as possible to the regulator pins to maximize their effectiveness.
The LM7805 is a linear voltage regulator, meaning excess voltage is dissipated as heat.
The power dissipated by the regulator can be estimated using:
P = (Vin − Vout) × Iout
Assuming:
P = (11.3 − 5) × 0.5
P ≈ 3.15 W
A power dissipation of approximately 3 W can cause the regulator to become hot during continuous operation.
For sustained operation at the maximum rated current, a suitable heatsink is recommended to maintain safe operating temperatures.
Several voltage regulation methods are available, including switching regulators and linear regulators.
For this project, the LM7805 was selected because it offers:
Although switching regulators provide much higher efficiency, the LM7805 is easier to understand and is commonly used when learning basic power supply design.
The PCB was developed using the same workflow commonly followed in professional PCB design.
The complete process consisted of:
Following this workflow helped ensure that the design was electrically correct, manufacturable, and well documented.
The project began by creating the complete circuit schematic in KiCad 9.
During this stage:
A clean schematic is the foundation of a reliable PCB design and helps reduce errors during later stages of development.
Each schematic symbol was assigned an appropriate physical footprint before PCB layout.
The selected footprints match standard through-hole components, making assembly straightforward for beginners.
The assigned footprints include:
Correct footprint assignment ensures that the physical components fit properly during PCB assembly.
Once the PCB was created from the schematic, components were arranged before routing.
The placement process focused on:
Proper placement significantly simplified the routing process and improved the overall appearance of the PCB.
Because the PCB is single-sided, all traces were manually routed on one copper layer.
Manual routing provided better control over:
Several component placements were adjusted during routing to achieve a clean and practical layout.
The final routing avoids unnecessary bends and keeps the board easy to understand for educational purposes.
After completing the routing, a Ground (GND) Copper Pour was added across the PCB.
Using a ground plane offers several advantages:
After creating the copper pour, the filled zones were updated to ensure all ground connections were electrically connected.
Before PCB layout, an Electrical Rules Check (ERC) was performed.
ERC verifies the logical correctness of the schematic by checking for issues such as:
Any reported issues were reviewed and corrected before continuing with the PCB layout.
Running ERC helped ensure that the schematic accurately represented the intended electrical circuit.
After completing the PCB layout, a Design Rules Check (DRC) was performed.
Unlike ERC, which validates the schematic, DRC checks the physical PCB layout.
The following items were verified:
Passing DRC provides confidence that the PCB is suitable for fabrication.
Before generating manufacturing files, the PCB was inspected using KiCad's 3D Viewer.
The 3D inspection was used to verify:
This step helps identify placement or orientation issues that may not be obvious in the 2D PCB editor.
The final stage of the project was generating the manufacturing files required for PCB fabrication.
The generated files include:
These files are included in the gerbers/ directory and are ready for submission to a PCB manufacturer.
Although this project was primarily created as a PCB design learning exercise, the circuit was designed using standard linear power supply design practices.
The following electrical characteristics are expected:
| Parameter | Expected Value |
|---|---|
| Input Voltage | 9V AC |
| Output Voltage | 5V DC |
| Maximum Output Current | 500 mA |
| Voltage Regulation | Approximately ±5% |
| Regulator | LM7805 |
Future revisions of the project may include measured performance data such as:
Like any engineering design, this project has certain limitations.
Understanding these limitations is an important part of engineering design and helps determine whether the circuit is suitable for a particular application.
The repository is organized to separate documentation, PCB design files, and manufacturing outputs.
Single-Sided-5V-Power-Supply/
│
├── Docs/
│ ├── schematic.png
│ ├── pcb-layout.png
│ ├── pcb-3d-front.png
│ └── pcb-3d-back.png
│
├── gerbers/
│ ├── *.gbr
│ ├── *.drl
│ └── *.gbrjob
│
├── LICENSE
├── README.md
├── .gitignore
│
├── Single-Sided 5V Power Supply.kicad_pro
├── Single-Sided 5V Power Supply.kicad_sch
└── Single-Sided 5V Power Supply.kicad_pcb
This project successfully demonstrates the complete workflow involved in designing a simple regulated power supply PCB using KiCad.
Through this project I gained practical experience with:
Although the electrical circuit itself is relatively simple, completing the entire hardware development workflow provided valuable practical experience that extends beyond circuit design alone.
Every hardware project presents unique challenges, and this project was no exception. While the electrical circuit is relatively simple, designing a manufacturable PCB and documenting the complete engineering workflow provided valuable practical experience.
One of the first challenges was understanding how each stage of PCB development connects together—from schematic capture to PCB layout, verification, and manufacturing.
Working through the complete workflow gave me a much better understanding of professional PCB development practices.
Achieving a clean component placement required several iterations.
I learned that spending additional time arranging components before routing greatly simplifies PCB layout and results in a cleaner, more maintainable design.
Routing every connection on only one copper layer was one of the most challenging aspects of the project.
Because routing flexibility is limited on a single-sided PCB, I had to reposition components multiple times before reaching a layout that balanced functionality, manufacturability, and readability.
Before this project, I had limited experience using ERC and DRC.
Through this design, I learned that:
Both are essential steps before manufacturing a PCB.
Another important lesson was learning that a good engineering project is not only about creating a working circuit but also about documenting the design decisions.
While improving this project, I expanded the documentation to include:
These additions make the project more useful for anyone reviewing or learning from the design.
This project helped me develop practical experience with:
One of the biggest lessons I learned is that PCB design is an iterative engineering process.
Designing a reliable PCB requires much more than simply connecting components—it involves planning, verification, documentation, and continuous improvement.
Although this project successfully meets its educational objectives, several improvements could be made in future revisions.
Future versions may include:
These improvements would further increase the robustness and practical usability of the design.
This project allowed me to develop and practice the following technical skills:
| Tool | Purpose |
|---|---|
| KiCad 9 | Schematic Capture and PCB Design |
| Git | Version Control |
| GitHub | Project Hosting and Documentation |
The following resources were used during the development of this project:
This project was completed as part of my ongoing journey to learn electronics and PCB design.
It provided valuable hands-on experience in the complete PCB development process, from schematic creation and PCB layout to verification, documentation, and manufacturing file generation.
The project also reinforced the importance of engineering documentation, design verification, and continuous improvement through technical feedback.
I look forward to applying these lessons to more advanced embedded systems, power electronics, and PCB design projects in the future.
This project is licensed under the MIT License.
See the LICENSE file for more information.
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