Assignment 6

Electronics Design

How to:

This week is all about electronics designs, that means getting to know the whole process from designing a schematic and a board, milling the PCB and soldering. In the week's group assignment we tested the test equipment in your lab to observe the operation of a microcontroller circuit board. Detailed information about this can be read on the Group project page.

Except soldering, this field is totally new for me. Therefore, first of all I looked for tutorials that would help me gaining knowledge. Furthermore, our local instructor gave us an introduction into basic electronic topics, designing with Eagle and soldering. In this tutorial we soldered basic elements like an LED and pin headers.

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General steps:

1. Design schematic and board files in EAGLE.
2. Use CAM processor in eagle to produce BOT, .DRD, .TOP, .BOA files.
3. Prepare for milling with CircuitCAM.
4. Using the PCB milling Program BoardMaster.
5. Milling itself.
6. Prepare for soldering and assembling.
7. Assemble and solder components to PCB.

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Schematic and Board Design

1. First of all I installed the Eagle software on my laptop. To get to know how to use the software I had a look into the following tutorial: Eagle tutorial.

2. Our exercise for this week was designing the Hello-World-Board. The link shows the board which and I used it as a template for the design. Additionally, we were asked to add at least one button and one LED (including a current-limiting resistor) into our board design.

3. The most challenging part during the design was finding the correct digital components that represent the desired components on the real world. Eagle is presumably a good software for experienced users. But as a novice learning how to handle the software is hard. The tutorial mentioned before and also asking our local instructor helped me. Furthermore, the archive of the FabAcademy, especially this student's page had a lot of helpful hints. When creating the schematic each component has a little cross, which can be seen as the handle to control/move/edit (move/rotate tool etc. need to be chosen before and can be found on the left of the application) the component.

4. After designing the schematic I started designing the board of my schematic. To start I pressed and allowed the software to draw the board from my designed schematic. The big task now was routing the lines between all components on my board. Before I was able to start routing I had to puzzle the components into a reasonable layout in which the connections of the components do create as less overlaps as possible.
Eagle provides an autoroute option. I tested this several times until autorouting was able to route everything without producing overlaps. Even if the autorouting did produce a working board, I decided to manually route the connections between the components as a human being is most times able to be more clever than the autoroute tool. Additionally, I wanted the routes to have a bigger width than with the autoroute tool. Still, I used the autoroute result as inspiration during my manual routing to assure I do not create overlaps.

5. All in all, it took about an hour to route all connections manually. In the beginning it was hard to route properly as meeting the correct start and end point of a route needs some training. You can find the schematic and board files at the end of the page.

ERC and DRC Check

Eagle provides two tools that help you to check whether your board is correct or not: a.) electrical rule check (ERC) and b.) design rule check (DRC).

a.) The ERC checks e.g. for any open or overlapping pins and ports on your schematic and will give out these errors.
b.) The DRC establishes a set of boundaries for trace widths, component spacing, via diameters that you can check for your board.

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