Home


Week #6 ELECTRONIC DESIGN




Assignment





Week workflow

This is how I see my week


Softwares used


Eagle



Getting Started With Eagle



EAGLE (Easily Applicable Graphical Layout Editor) is a flexible and expandable EDA schematic capture, PCB layout, autorouter and CAM program. EAGLE is popular among hobbyists because of its freeware license and rich availability of component libraries on the web. We will use Eagle to layout and modify a circuit board for this assignment.

To get familiar with EAGLE, I started by watching the following tutorials on Youtube and read the one that we got in Fab Academy

Tutorial 1 for Eagle: Schematic Design

Printed Circuit Board Layout

Edit the Schematic



First thing I did, was to redraw the design schematic from Neil "hello World" board following the Week6 - Introduction Tutorial to EAGLE adding the following components:



Add / Connect Components in the Schematic


To add a component, you can either type "add" or select the "add icon from the toolbar". The add menu will open. You can either look through the listed libaries for a component to add or you can type it into the box above the "drop" button.

Add AVRISPSMD Connector (in the FAB_Hello library)

I've followed the same procedure with the others components

Schematic before connecting the nets

To connect components in the schematic, I've used two different ways:

  1. You can connect the components with a wire (also called a "net" in Eagle). This may make connections obvious at first, but can get really messy quickly as nets cross over each other.
  2. You can also name the nets attached to components that need to be connected by naming them with the same name. Eagle will ask you if you want them to be connected. (Say yes!). After you name the component - label it so the name appears in the diagram.

Naming the nets attached to components

This is the resulting schematic.

Neil "hello World" board schematic

Add / Connect LED + Button components in the Schematic


On the top of Neil board schematic, we had to add / connect the extra following components following the same process as described before:



Adding a button and LED to Neil echo hello-world board schematic

Route the Traces on the Board



Once you have the schematic, switch to the board view 


Use "move" to move each individual component around.

Adding a button and LED to Neil echo hello-world board schematic

Once placed components, there are few features to understand before tracing the routes



Understanding Layers settings


There are a lot, but it is not important to understand all of them but let's talk about the important ones.

Importants Layers to understand

Understanding GRID settings


In the schematic editor we never even looked at the grid, but in the board editor it becomes much more important. As EAGLE forces your parts, traces, and other objects to “snap” to the grid defined in the Size box, it is good to know that you can adjust the granularity of the grid, by clicking on the GRID icon. 


If you need finer control, hold down ALT on your keyboard to access the alternate grid, which is defined in the Alt box.

Grid settings adjusted

Change BACKGROUND settings


Having a Black background is more convenient to edit the board

White versus Black Background

Change NET settings


The above picture shows very tiny traces on my circuit board. The reason is during my first attempt to mill the board, I didn't pay attention to the default presets associated to the width of vias on Eagle.

In Eagle you can associate a class with a net. The class defines some information to control the width, clearance and drill of vias. By creating a specific class for the ground, the power supply and normal signals, we can control quite easily the width of each signal. The feature is quite hidden in Eagle and I think it is not well explained. First, in the Eagle board editor, activate the class editor.

To fix that, I went to:

. 
Edit / Net Classes / Nr 0 (which is the class associate to the vias) / Change default values from "8 mil " to "16 mil" everywhere

Net Clases settings

Ready to route the traces


To route the traces, you can either do it manually or do it automatically with the "autorouter" option. I decided to do it manually.

My board routed

Checking for Errors


Before we package the design up and send it off to the Roland MDX, we can use to check our design for errors:

Adapting DRC values to our milling 1/64 bit dimensions

DRC sent me back 4 errors

DRC found 4 errors message 

Once you’ve seen both “No airwires left!” and “DRC: No errors.”, your board is ready to send to the fab house, which means it’s time to generate some gerber files.


Exporting the Board Design to be Used with Modela



To prep board for milling:

I've used GIMP to edit the board files and create the traces and mill-out files.

Milling the traces

Milling the outline

Milling the board

Welding the board



This board is not very difficult to weld, the chip is large enough to be welded with a low power welder seamlessly, maybe the most complicated piece for soldering is the resonator, to facilitate welding of this part, it is best to use a little FLUX.

Hello World board

Final Project evolution




Download


You access and download all the files generated during this week from my google drive:




Conclusion


I was completely new to Electronic design and it has been a great introduction week. One of the great learning of this week is about the settings you need to take care (i.e. grid settings, net settings ) before starting editing the traces on the board. What's more, it is essential to adapt the Design Rules according to your local machine / tools and check if DRC are all respected before exporting your your file.