Week 6 - Electronics Design


Redraw the echo hello-world board, add (at least) a button and LED (with current-limiting resistor)
check the design rules, make it, and test it extra credit: simulate its operation extra credit: measure
its operation

First of all I would like to point out the electronic production week, in which we also designed our fabisp based on the work of Brian's programmers, based on Zaercs programmers.
In the 4th week we have therefore already insights in the design of elektonic with eagle received and it was easier for us in this week to design the hello board

Why I use Eagle?

The software eagle was first recommended by my instructor. Eagle is the standartool in our fablab when it comes to the design of pcbs. In the lesson of technical computer science it is used by the students to make their first experiences with the design of pcbs.

Since I also use the software of autodesk (fusion360) for the 3d-design, I decided to test eagle. After the first tests with eagle, it was for me directly a good expirience to work with it. I also like that Autodesk is in planing to integrate eagle in fusion360. In addition, the ERC function is very useful for me as a beginner. A further reason is that my instructor Tobias could give me a good introduction into the software eagle.

1. First I had to add the fab library to the program Eagle:

Download the eagle fab libary here

Fablab component library: Copy the library into the install directory of eagle into a folder called "lbr"

2. Start to design the Schematic in Autodesk Eagle:

I have kept myself for this assignment to the tutorial given to us by the fabacademy. You can find the tutorial at the following link: Fabacademy Tutorial website

After the libary has been downloaded in the program eagle still everything is to be updated and you have to click on the menu "use library". Then you can enter the word "add" in the command line and it will open a window, where you can find the various libraries:

To find the fab-libary type *fab*

At first I insert the Attiny 44 by using the fab-libary and searching it with *attiny44*:

After adding all needed components, my schmetic was complete:
Further down on this page you can download the complete part-list of eagle, as well as the whole board designs.

At next, the layout of the board must be created. All routes must be set to connect the parts. To switch to the board layout view, change to the board view at the top of the toolbar.

Now it is important that you arrange all the components in a poligon sequentially prepared in the field:

On the following photo you can see that you can switch to the red marked area in the board layout view to start now the board layout:

My instructor Tobias told me about the rastnest function. (A function in the circuit board layout, with the possibility to connect a signal to the entire copper area, which is located between all parts on the board).

It is a really good technique to use the GND signal Over the entire layout, set the 'name' of the rect to GND, and press the rastnest button

    Partlist exportet from Eagle:

Checks design rules.

The command DRC checks a board against the current set of Design Rules.

Only those signal layers that are currently active will be checked, so in order to make sure everything is ok all used signal layers should be active when running the DRC (at least for the final check before manufacturing).

At the design rule check, among other things, still existing air lines are displayed, which one could have forgotten to route. In my case, the check was successful and I had nothing to edit in the design:

If for example one or more airwires has forgotten to route, you will see the following at DRC (If you klick on the error message it is displayed directly):

3. Mill, equip and heat the Board:

At the next 2 following Pictures you can see the ready milled pcb board. Before I could equip the board now with components I had to sand it and paint a thin layer of so-called solder varnish, which hardened very quickly. For the solder paint I have used This stuff

A view through our microscope from the company Vision Engineering can help to detect possible errors in the board at an early stage. After the milling, as well as after the assembly or soldering it should be examined not only optically but also with the multimeter!

The next photos show the dispensing with the soldering paste, as well as the mounting of the individual components. The dispenser is led by hand to the appropriate places and then deposited with various time intervals solder paste on the pads.
For stats bigger pads we took an intervall of 0.6 seconds and for narrow pads
(eg the pads for the attiny44) we used intervals of 0.3 seconds. For the assembly of the board, the protoplacer was converted into an assembly machine. The cannula from which the solder paste came before was unscrewed and a clean cannula was inserted. The smd components were so deposited that we could easily reach them with the cannula. By suction, the smd components were now captured by the cannula and I could bring this into position.

Please finde here the Partlist exportet from Eagle: Download the Partlist from Eagle

In the following 1 minute video the process of formation of my hello-board on the LPKF milling machine is illustrated. First the conductor lines are milled into the board. In the last step, the outer contour is milled out, a Curcuit Pro- software Tutorial for single sided pcbs please find in Week 4 - Electronics Production.

PCB off into the oven

The finished stocked pcb gets into the reflow-ofen done

  • First pre-heat 3 minutes at 170 degrees celsius reflow.
  • Then another 90 seconds at 225 degrees celsium.
  • The cool down mode finally ended with opening the door of the reflow oven.
  • After I still had some time to think about a cool design for a small housing of my Hello-Board for the 3d printer is then born the small brother of HAL 9000 ;)
    The "eye" in the case is with the laser cutter made of satinated acrylic. The top of the box and the cover is designed in Fusion 360:


    Partlist from Eagle

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