Mastering KiCAD 9.0: Unveiling the Secrets of Schematic Creation with Basic Components and Nets

1. Starting a New Project in KiCAD 9.0

Launch KiCAD and begin by creating a new project: go to File → New Project, enter a name, and choose a save location. KiCAD will create a project folder containing several key files—most importantly, your .kicad_sch (schematic) and .kicad_pcb (layout) files, both of which are automatically generated when you create the project.

Once the project is initialized, click the Schematic Editor button from the main project window. This opens the schematic workspace, where you’ll begin placing components, connecting nets, and building your circuit logic. This editor is the starting point for nearly every KiCAD design workflow.

2. Placing Core Components

With the schematic editor open, press 'A' or click "Place Symbol" in the top toolbar to access the symbol library. This is where you’ll find every component available for schematic use—organized by category and searchable by name.

To build a basic LED circuit, locate and place the following components:

• Device:R – a generic resistor

• Device:LED – a standard LED symbol

• power:+5V – a 5V power rail symbol

• power:GND – a ground connection symbol

Click once in the schematic to place each component. You can continue placing the same component multiple times, or press Esc to cancel. After placement, you can select any component to move it. Use R to rotate, and X or Y to flip horizontally or vertically. Arrange the parts so that connections will be logical and clean in the next step.

3. Annotating and Setting Values

Before connecting anything, assign unique reference designators to each component using the "Annotate Schematic Symbols" tool in the top toolbar. KiCAD will automatically number your parts—R1, D1, and so on—so each one can be uniquely identified in the schematic and later in the PCB layout and bill of materials.

Once annotated, set the component values. Double-click the resistor symbol, and a properties window will appear. Enter a value such as 330 or 1k in the Value field. This value is used not just for display but also for simulation and documentation. Repeat this process for any other component where value matters—for example, selecting the correct LED model if needed, or labeling capacitors if you add them later.

4. Connecting Components with Nets

To begin wiring, press 'W' or click "Place Wire" from the toolbar. Your cursor will switch to wire-drawing mode. Click on a component pin to start a wire, drag it to the next pin, and click again to complete the connection. Press Esc to exit wire mode or start a new segment.

In the LED circuit:

• Connect the +5V symbol to one side of the resistor.

• Connect the other side of the resistor to the anode (positive side) of the LED.

• Connect the cathode (negative side) of the LED to GND.

Keep these guidelines in mind:

• Wires must meet at junctions marked by a small round dot. Without it, no electrical connection is made.

• Avoid letting wires merely cross—if two lines intersect without a junction, they are not connected.

• For clarity, use the "Place Net Label" tool to name important nets like VCC, OUT, or LED_GND. Any nets with the same name are considered electrically connected, even if there’s no drawn wire between them. This is helpful for managing large or complex schematics.

5. Working with Power and Ground

Power and ground symbols in KiCAD aren’t just visual markers—they define global nets, which means any pin connected to a +5V or GND symbol is electrically linked to every other instance of that symbol across the schematic.

Attach them directly to the appropriate pins on your components. For example, connect +5V to the resistor’s input and GND to the LED’s cathode.

Using these symbols simplifies the schematic by eliminating the need for long wires across the page. Instead of physically connecting every power and ground line, you define the logic with consistent net naming. This keeps the layout clean and makes the circuit easier to read.

6. Running an Electrical Rules Check (ERC)

Before moving on, run an Electrical Rules Check (ERC) to catch common design mistakes. Click "Perform electrical rules check" from the top toolbar to open the ERC dialog.

KiCAD will scan your schematic for issues such as:

• Unconnected pins – components that are missing essential connections

• Power pins without assigned nets – for example, VCC or GND not properly tied to power symbols

• Incompatible pin pairings – such as connecting two outputs directly together

Review the list of warnings and errors. Click on each message to highlight the associated problem in the schematic. Many issues can be resolved by completing connections or correcting net names.

If you intentionally left a pin unconnected (common with unused inputs or configuration pins), place a no-connect flag using the "Place No Connect" tool. This tells KiCAD that the unconnected pin is intentional and suppresses the warning.

Running ERC early and often helps maintain design integrity and prevents avoidable mistakes later in the workflow.

7. Saving Your Work

Use Ctrl+S frequently to save your schematic. KiCAD does not autosave by default, so regular manual saves are essential—especially before running tools like ERC or moving to PCB layout.

At this point, you’ve placed your components, defined the nets, assigned power, and validated the structure with ERC. This schematic is more than a visual—it’s the data model for your entire board. Netlists, footprints, and electrical intent all flow from this file. A clean, well-structured schematic here means fewer problems and clearer decisions later, when you step into PCB layout, routing, and final output generation.