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Electronics Design

Designing a PCB using EAGLE

To create our own circuit board, we have to use a CAD tool to design the schematic and drawing its layout. Autodesk EAGLE is a software that helps us do just that.

In EAGLE, there are two windows called SCH and BRD. We can switch between the schematic and board button to design a pcb.

Assignment: Redraw an echo hello world board (add at least a button and led)

I will be making an echo board using the ATtiny85 chip. This is the datasheet summary for ATtiny85 found on Microchip website.

To get started, I will need to download and install the component library. The library I’m using is fab.lr.


Steps to download fab.lr

In my file manager, I place the downloaded fab.lr (named eagle_fab) in the EAGLE library.

Now for me to use it, at the EAGLE control panel, go to the directory and select the library. A green dot indicates that it is in use.

Create a new project.

We will have to add and connect components in the schematic window first. To add components, select the add parts icon . You can either look through the listed libraries for a component to add or you can type it into the box above the “drop” button.

Editing the schematic

  1. Add in the right components for your board.
  2. Use NET tool to wire our parts together.
  3. Use NAME tool to identify our components/name our nets.
  4. Use VALUE tool to set resistors resistance or capacitors capacitance.
  5. Verify the design using ERC.
  6. Go to board view to position our components and route traces.

Refer to this Sparkfun link for detailed explanation on wiring up schematic on EAGLE. https://learn.sparkfun.com/tutorials/using-eagle-schematic


This is a screenshot of my completed schematic

Editing the Board

When we move to Board view, the components that we have just wire will be jumbled up. We will have to re-arrange the traces accordingly, up to the user’s design.

  1. Move individual components around. Rotate to figure out the simplest pathway.

  2. Route all the traces. Or use the autorouter feature.

  3. Use DRC to select wire dimension.

  4. Create a border under the milling layer. (blue)

It it safe to say, to cnc a pcb in fablab, use this parameters to determine width of traces:

  • 10mil / 0.25mm for very fine traces
  • 16mil / 0.4mm for traces
  • 32mil / 0.8mm for board outline


Finalised board design before generating Gcode

Export board design

Select the LAYER icon located on the top left of the screen.

From here you may use EAGLE’s pcb-gcode setup or export a high resolution png image. Since EAGLE has a setup to generate Gcode, i’ll would like to try exporting my board design directly from EAGLE software.

Run pcb-gcode ULP.