KiCad 9.0 – Getting Started Part 4- Finishing the Schematic - DigiKey

Episode 4: Using Your Custom Symbol and Completing the Schematic in KiCad In this episode of our KiCad water alarm project, we take your custom buzzer symbol from Episode 3 and bring it into the schematic. This is where everything starts to come together—you’ll wire up your components, add important net labels for clarity, and learn to properly define power sources and external connections for the Bill of Materials (BOM). We begin by placing the buzzer symbol using the 'A' hotkey in the Schematic Editor. You’ll learn how to rotate or flip the symbol (using the toolbar or ‘X’ key), then wire pin 1 to the Vcc line, power jack, and terminal block—ensuring a clean and understandable layout by avoiding unclear 4-way wire junctions. Next, we wire the buzzer’s negative pin to the drain of the MOSFET and walk through best practices for net labeling. We show how to rename important nets like the gate line using the ‘Place Net Label’ tool—making things easier later during PCB layout. We also explain how power symbols like Vcc and GND automatically assign names to the connected nets and how to visualize or customize them further. You’ll also learn how to change the appearance of a net using the ‘Select Connection’ shortcut (Ctrl+4), how to adjust wire width and junction dot size, and why visual clarity can really improve the readability of your schematic—especially when working in teams or revisiting the design later. We then cover how to represent off-board components (like power supplies or batteries) in your BOM without placing them on the PCB. Using placeholder symbols like “Housing” and “Battery,” we set the reference designators (Z1 and Z2), add descriptive values, and flag them as “Exclude from board” so they show up in your part list, but not in layout. To wrap up the schematic, we run KiCad’s Electrical Rules Checker (ERC) to look for issues. We address common warnings like unpowered nets by adding ‘Power Flags’ and teach how to use the ‘No Connect’ flag on unused pins—especially useful for off-board placeholder components. Finally, we highlight the importance of keeping your schematic editor grid at 50 mils. Changing it can lead to disconnected wires that look visually correct but fail to connect electrically—an easy mistake to avoid. By the end of Episode 4, your schematic is fully wired, net-labeled, power-ready, BOM-complete, and ERC-approved. In Episode 5, we’ll move on to assigning footprints and even creating a custom one.

KiCad 9.0 – Getting Started Playlist: https://youtube.com/playlist?list=PLEBQazB0HUyQ5YJSdCBb79orXaR3Uk5vm&si=g02iKeCVmimoCheH Intro to KiCad V4.07 Playlist: https://www.youtube.com/watch?v=vaCVh2SAZY4&list=PLEBQazB0HUyR24ckSZ5u05TZHV9khgA1O&pp=gAQB Water Alarm Project: https://www.digikey.com/en/maker/projects/water-alarm-priceless-protection-crazy-simple/ee442d13e7164b99acb52793b56af391 KiCad Download: https://www.kicad.org/download/ TechForum KiCad Category: https://forum.digikey.com/c/design-tools-and-resources/kicad/19 DKRed Service: https://www.digikey.com/en/resources/dkred

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