kicad-learning-path

LED + Push-Button PCB

A fully documented KiCad 10 project: a 5 V push-button that lights a red LED through a current-limiting resistor. Project 1 of my KiCad learning path, from basic electronics to advanced PCB design.

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Table of contents

• Overview
• Key specifications
• Gallery
• How the circuit works
• Design calculations (summary)
• Bill of materials
• Netlist
• Repository structure
• Getting started
• Testing
• Verification status
• Future improvements
• Learning-path roadmap
• License

Overview

This board is deliberately simple so that the complete professional PCB workflow is covered end to end:

1. Electronics fundamentals and component calculation
2. Schematic capture with power flags and a clean ERC
3. Footprint assignment
4. Board setup: stackup, design constraints, net classes
5. Placement, routing and copper pour
6. DRC, 3D check and Gerber verification
7. Manufacturing file export for a low-cost 2-layer fab

What it does: a 5 V supply is connected to header J1. While push-button SW1 is held down, current flows through resistor R1 and LED D1, and the LED lights. R1 limits the current to about 9 mA.

The full engineering write-up (theory, derivations, KiCad configuration, layout rules, manufacturing settings) is in docs/DESIGN_NOTES.md.

Key specifications

Parameter	Value
Supply voltage	5 V DC (via J1)
LED current (nominal)	≈ 9.1 mA
Current-limit resistor	330 Ω, 0805, 1 %
LED	Red, 0805, forward voltage ≈ 2.0 V
Board layers	2
Board thickness	1.6 mm
Copper weight	1 oz (35 µm)
Board size	18.750 × 11.480 mm
Components	4 (J1, SW1, R1, D1)
Pads / nets / vias	10 / 4 / 0
Minimum track / clearance	0.2 mm / 0.2 mm
Design tool	KiCad 10.0.x
ERC / DRC	0 errors / 0 errors

Gallery

Schematic

Full-size PDF: docs/schematic.pdf

PCB layout

3D views

Top	Bottom

How the circuit works

+5V ──► SW1 (push button) ──► R1 (330 Ω) ──► D1 (red LED) ──► GND

• J1 brings in 5 V on pin 1 and ground on pin 2.
• SW1 is normally open. Pressing it completes the loop.
• R1 drops the surplus voltage so the LED current is safe.
• D1 conducts only in the direction of the triangle (anode to cathode) and lights up.
• The same current flows through every part, because they are in series.

Design calculations (summary)

Ohm’s law:

\[V = I \times R\]

Resistor value for a target LED current:

\[R = \frac{V_S - V_F}{I_F} = \frac{5.0\ \text{V} - 2.0\ \text{V}}{10\ \text{mA}} = 300\ \Omega \;\rightarrow\; \text{330}\ \Omega\ \text{(standard E12 value)}\]

Actual current with the standard value:

\[I = \frac{V_S - V_F}{R} = \frac{3.0\ \text{V}}{330\ \Omega} \approx 9.09\ \text{mA}\]

Power:

\[P = V \times I = I^2 R\]

Element	Voltage drop	Current	Power
R1 (330 Ω)	3.0 V	9.09 mA	27.3 mW (rating of 0805: about 125 mW)
D1 (red LED)	≈ 2.0 V	9.09 mA	18.2 mW
SW1 (closed)	≈ 0 V	9.09 mA	≈ 0 mW
Total from supply	5.0 V	9.09 mA	45.5 mW

Worst-case analysis (supply ±5 %, resistor ±1 %, LED forward voltage 1.8 V to 2.2 V) gives a current between 7.65 mA and 10.56 mA, which is safe for the LED and the resistor. The full derivation is in docs/DESIGN_NOTES.md.

Bill of materials

Ref	Qty	Value	Footprint	Description
J1	1	Conn_01x02_Pin	PinHeader_1x02_P2.54mm_Vertical	2-pin 2.54 mm header (5 V in)
SW1	1	SW_Push	SW_PUSH_6mm	6 mm tactile push-button
R1	1	330 Ω	R_0805_2012Metric	Resistor, 1 %, 1/8 W
D1	1	RED	LED_0805_2012Metric	Red LED, 0805

The same list is available as CSV in fabrication/bom.csv.

Netlist

Net	Connections
+5V	J1 pin 1, SW1 pin 1
Net-(R1-Pad1)	SW1 pin 2, R1 pin 1
Net-(D1-A)	R1 pin 2, D1 anode
GND	D1 cathode, J1 pin 2

Repository structure

kicad-learning-path/
├── README.md                    Index of all projects
├── LICENSE
├── .gitignore
└── 01-led-button/               This project
    ├── README.md                You are here
    ├── 01_led_button.kicad_pro  KiCad project file
    ├── 01_led_button.kicad_sch  Schematic
    ├── 01_led_button.kicad_pcb  PCB layout
    ├── fabrication/
    │   ├── gerbers/             Gerber and drill files
    │   ├── 01_led_button_gerbers.zip
    │   └── bom.csv
    └── docs/
        ├── DESIGN_NOTES.md      Full engineering documentation
        ├── schematic.pdf
        ├── images/              Screenshots and 3D renders
        └── reports/             ERC and DRC reports

Getting started

Open the project

1. Install KiCad 10.
2. Clone or download the kicad-learning-path repository.
3. Open 01-led-button/01_led_button.kicad_pro in KiCad. The project uses only the standard KiCad libraries.

Rebuild the manufacturing files

1. Open the PCB editor and run Inspect → Design Rules Checker. It should report 0 errors.
2. Open File → Fabrication Outputs → Gerbers and Generate Drill Files. The exact settings are listed in docs/DESIGN_NOTES.md.
3. Zip the output folder.

Order the PCB

Upload fabrication/01_led_button_gerbers.zip to a PCB fabricator. Suggested options for a low-cost fab: 2 layers, 1.6 mm, 1 oz copper, HASL finish.

Testing

Bring-up procedure and expected measurements are in docs/DESIGN_NOTES.md. In short: apply 5 V, press SW1, and the LED lights; the voltage across R1 should read about 3.0 V.

Verification status

Check	Result
Electrical Rules Check (ERC)	0 errors
Design Rules Check (DRC)	0 errors, 0 unrouted nets
Gerber viewer check	Passed
Physical board built and tested	Not yet

Reports: docs/reports/

Future improvements

• Add reverse-polarity protection on J1
• Add mounting holes
• Reduce silkscreen text size and keep it clear of the board edge
• Add a second LED as a power indicator
• Replace the header with a USB-C connector (see Project 4)

Learning-path roadmap

#	Project	Status
1	Push-button LED board	Done
2	555 timer LED blinker	Planned
3	Transistor/MOSFET driver	Planned
4	USB-C to 3.3 V power board	Planned
5	Microcontroller board	Planned
6	Advanced capstone	Planned

License

Released under the MIT License. Replace with a hardware license such as CERN-OHL-P-2.0 if you prefer.

Author: Nitish Ghadage · GitHub

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