Week 7 - Electronics Design

June 22018

ELECTRONICS DESIGN

Download all the files for this week from here

  • For group assignment visit here.

  • This week we had to design a PCB with the help of a Deisgning Software. There are several online and offline softwares available for designing a PCB, mostly all of them have the same workflow.

Select Component > Assign Footprint/Package > Design Schematic > Design Board.

  • Components look like these :
  • Footprint is the size and the orientatoin of its’ terminal and pins :
  • Schematic :
  • Board :

Softwares I used :

  1. EasyEDA
  2. Eagle

INTRODUCTION

  • This week we had to Redraw the Hello FTDI board and add a button and LED to it. Hello FTDI had a attiny44, but in the lab we were not able to find the 44s (found them later) so we decided to use the Attiny45 instead.
  • This proved to be a challenge since it only has 8 pins and most of the pins would be taken up by the Hello FTDI components. It was very difficult to stuff extra components, which was later achieved by sharing pins of the MC.
  • * I started by reading the point of the attiny45 and its data sheet.
  • Here are some initial scribbles:

EASY EDA

  • EasyEda is an online software to design your board and simulate it. It was the easiest to use among all of the three softwares that I used. The interface was easy to understand and very intuitive.
  • Like in all the softwares we have choose and place a component built in EasyEDA the component library was like a gallery where you can also search user created parts and footprints.
  • The schematic you make can be posted to an online archive so that other people can use it.

  • Here are screenshots of some schematic and board, I won’t be explaining this since I do not recommend it, also I was not able to get it to work.

easyeda

easyeda

easyeda

easyeda

  • After I finished the board, I couldn’t get export it to the desired output, EasyEDA provides PCB production services which was of no use. Hence, I switched to Eagle.

    EAGLE

  • Eagle is an offline EDA tool, it is one of the most common. The workflow is the same as discussed earlier.

  • I started by importing FAB LIBRARY to Eagle. You can download the library from here.
    Instruction to install the library can be found here.

  • After importing the library I started with the design.

Schematic

  • Schematic is simply a line diagram or connections of all the components that are on your board.

  • In the schematic you can add, select, group, re-arrange etc. the components. Menu on the left side has all these options and are pretty much self explanatory.

  1. Add components from the library, make sure you select the right package.
  2. After adding all the component, select the line tool and draw a small line on the terminals of each component.
  3. Add Label to the terminal lines and then Name them. The terminals which have the same name are automatically connected, you’ll be prompted before that. This way of connecting components rather than drawing lines from one terminal to another is easy, less messy and more understandable.
  • After all the steps are doing, the schematic should look like this

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  • Now from the file tab select switch to board.

FILE Name in the source folder : week7-small.sch

Board

  • The board is the actual representation of the physical board, all the components in the Board window are according to their footprint, size.
  • When you open the barred window, you see all the components on the bottom left. The black space with red outline is your canvas where you have to place your comments.
  • Component is connected with a yellow line which are called air wire. These are there to show the connections between the components.
  • Layer, there are several layers on which you can route the components or add them. For my board the Routing was done on the top layer and the boarder outline was on the bottom layer.
  • Next step is to arrange all the components on the canvas, make sure you hit the Ratnest every time you place or move a component. This will reroute the airwires in a more optimal way.
  • I used Autorouting to route the board, but you can also choose to manual route. Before routing the board, I set the Net Values according to the specification of the tool I’ll be using. week7
  • Autorouting should give you the desired results, if not try to manual route the airwires left, also you can use jumpers if required.
  • Here is my Final Board layout :

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  • After you are satisfied with the board, the next step is to export it to the desired output.
  • For fabmodules we need a Monochrome image, you can select the LAyer you want to export and then click on export image.
  • Now you have the Monochrome Traces and Outiline files.

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FILE Name in the source folder : week7-small.brd

Final Output.

  • I milled the PCB on SRM-20 and then stuff all the components. If you want to know about milling the PCB, visit my [week-4]() page.

  • Here is my final Board :

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  • After Checking the connections with a multimeter, I found out that the MISO of ISP was not connected to the microcontoller. The PAD also burned off where the leg of microcontroller was making contact. So I took a wire and soldered both the components.

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