week 06

Electronics Design

1. Idea & Design

Membership Badge

I plan to make a double-sided circuit board.
The front is a heraldry,carved out by the CNC and the back side is a circuit board with a button.
I believe I can make it as a badge or medal and wear it as as an accessory.

Then I have come up with 2 ideal scenes

1. Use it as a VIP Membership Badge of our Fablab,you can

2.Use it as a「Ticket」to participate in our Fab Academy Graduation Party


In front of the badge , I decided to select a Chinese element as heraldry.
In the beginning, I thought of the pattern of goldfish. It means "abundance for every year".
However, it is difficult for fish and LED to be combined appropriately.

My last choice was a classic pattern of "Dragon play pearl " the pearl is LED.
Due to the size of the badges, it is not suitable to mill too many details.
So the last choice was this ancient dragon.

2.Group Assignment: PS + Milling out

I try to use this「Dragon」to test our Roland as a group project.
dpi: 72
size: 3000 x 3000 px
1058.333 x 1058.333 mm
41.667 x 41.667 in

But it's too big, I changed the Dpi from 72 to 1270,the size became 60x60mm Done~
Then need to cut it out and add 2 holes on the board for led later.
Note: Select PCB Outline Selection (1/32) (Ps: we didn't change the Milling cutter, still use the 1/64 and it's works just fine)


3.Individual Assignment: Eagle & Fabricating

CAD modeling with Eagle

Since Eagle was previously installed on my laptop, just open the Eagle new task directly

  • Add Fab.lbr to library file.
  • Then select components under the 「Fab」
  • Attiny44-ssu

  • Then draw a schematic

  • Direct use Command as input: Line / add / rota / move is a convenient operation
  • After the circuit drawing is completed, circuit board can automatically generated by.

    Tools >> Autorouter

  • Automatic connection then modify by hand.
  • The line width in the middle of the cpu is 0.01.
  • Then Export.

  • 3.1 Failure is the mother of success

    First saw the drawings, I thought I would have missed something, but I still wanted to figure out how the fab modules work.
    So I give it a try.
    I tried to mill directly with the exported graph, but the result was not successful.
    Here is the result:

    Then I noticed:

  • input file: dragon_02.png
  • dpi: 1500
  • size: 11816 x 9454 px
  • 200.081 x 160.085 mm
  • 7.877 x 6.303 in

    I don't know how to match the size of the image, so I took a closer look at the assignments of other classmates from 2016 to 2017 and this week's 「tutorial」 , discovery that
  • I used the incorrect default settings when exporting pictures.
  • And I didn't choice: MONOCHROME mode (black and white mode)
  • What's worse is that I ignored DRC (design rule check) in my previous work.
  • The two lines in the red box was mixed.

  • This experience has given me a major lesson:
    「Sharpening your axe will not delay your job of cutting wood」
    If you want to save time and complete your homework and work as quickly as possible, be sure to review the materials carefully before doing your homework. Even if you did same thing before.
    Other seniors' Assignment, as well as official documents, are more useful than I thought.

  • So I changed the width to 0.008 and then repainted the circuit structure which under the chip.
  • There is a clear path through the two lines in the red box.
  • I recheck the size of the exported png image in Eagle: 1969 x 1575 px.
  • Finally, I cut it out with Fabmodules
    (But I'm a bit worried about size, because it's not as same size as my previous setting of dpi:1270)

  • Saddly as a result, I found that there was something wrong with the size, so I checked and changed again.
    Some time there is no problem with the size, but the circuits in the middle of the chip are all connected together.

    3.2 Done

    I finally found the reason.
    The error is due to the png image exported from Eagle, the software will automatically expand more than 200% pixels as a png file.
    After knowing this problem, I immediately re-exported a new image. This time, the circuit and the size are finally work.
    Then I adjusted the circuit again and added our Logo to the circuit diagram.
    The end result is this:

    4. Soldering & Programming:

    Double-sided badge

    Because I had soldered many things before, I quickly made this circuit board.
    It is worth mentioning that the curved needles that are available on the market are too long and are very inconvenient to solder it.
    So I made an AVR ISP suitable pin header
    Then I painted a dragon with solder in the front of the badge. Stick both sides together

    DIY AVR ISP pin header proceed as follows:

  • I took out the iron bar of the straight needle
  • Neatly arranged
  • Clamp with wire pliers
  • Unified bending
  • Then insert it back and solder it on the circuit board

  • Programming


    File list

  • fab_2018.zip
  • rml
  • rml.zip