Drawing Schematics & Wiring

Workspace Tips

• KiCAD schematics are split into separated sections
  • The workspace - this is where your schematics are drawn which will be registered as components and wiring for your PCB
  • The toolbar - a list of commonly used tools to select components, generate a wiring diagram, add comments, update PCB, etc.
    • Here we’ll just refer to each tool by its position on your display
• The workspace, by default, is set in inches; we want to change this to mm

  • To do this, click the ‘Use millimetres’ on the left side of the window

    

  • We do this as any component and wiring will immediately snap to align with the grid

    • In the case we don’t want this to occur, hold control (command for mac) on your keyboard to place your component anywhere without grid restrictions

Placing Symbols

• PCB software design often follow hand drawn conventions for PCB schematics, which allows a much easier process to draw and understand the wiring

• To select a symbol to place down

  • Click the ‘Add a symbol’ located on the right side of your window, or

    

  • Type ‘A’ on your keyboard then click anywhere on the work surface

• Here a symbol library is present which also has options to attach a footprint

  • A footprint is just the layout for the physical PCB

• This example is looking for a resistor to place down

  • Type “Resistor” then search for the desired footprint
    • For a resistor, look for “R” with the following footprint

• You can also select your footprint which matches the physical hardware that you have

  • Click on the “No default footprint” section of the menu and select your footprint
    • When you choose a footprint, the footprint will be displayed in the black box showing the dimensions of the physical hardware. Use this to aid your footprint selection for parts you have

• Click ‘OK’ once everything is selected and you are happy with the parts
  • If your desired footprint is not available, you can still click ‘OK’ without a footprint
    • Refer to the ‘KiCAD Footprint’ section of this worksheet to learn to make your own footprint if you are interested
• Click where you want to place your symbol in the workspace to place your symbol
  • To rotate your part, press ‘R’ before you place your symbol
• If you want to another part, click left click again, otherwise hit the ‘esc’ key on your keyboard to exit the tool

Change component values

• Each component has values and can be labelled to add parameters
• Parameters and values are useful to keep track of what component does what for hardware debugging as well as the type of part you are using
  • To change your parameters/values for a symbol, double click your symbol
  • A ‘Symbol Properties’ menu will pop up with a set of options to adjust
    • Your ‘Reference’ section is used to give a unique identity for each component labelled by XY
      • X being a letter representing the type of component
      • Y being a unique number for your component
    • Your ‘Value’ is a numeric or worded value which dictates the part number or value
      • For resistors, capacitors or inductors, this will be your value
      • For other components, this will be parts number which is usually automatically filled if you find your desired part in the library
    • Once any changes are made, just click ‘OK’

Wiring & Connections

• To begin wiring

  • Click the ‘Add a wire’ located on the right side of your window, or

    

  • Type ‘W’ on your keyboard

• You’ll notice that a green wire would immediately trace from your mouse when doing this
  • To stop this current trace, press ‘esc’ once

Connecting Components - Direct

• First type of connection that can be made between two symbols is directly
  • Click on the end of a component and move your mouse around
  • Click on the end of another component you want to connect, which will complete your wiring
    • If you click your mouse on the workspace without connecting to a component, you will place your trace in that position and continue from there
• Once wires are placed, they can be moved
  • To do this, just click on the wire then drag the wire
• Note that sometimes that you may find that you have nodes which connects three or more wires together
• To create a node to an existing wire, extend your current wire that you want to add and click at any point on the wire you want to move
• To delete an existing node, click on the node and hit ‘delete’ or ‘backspace’ on your keyboard