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Electronics production

Week 4

PCB . fabrication





For the experiences in PCB manufacturing I used the FabTinyStar - another version of an AVR ISP programmer/board.


Several group experiments were made in the fab lab from the examples: Ali (microUSB) and Brian (USB).

  • Ali link
  • Brian link





    • We used a Hartpapier-Platte, cu, FR2 with 1.7mm thickness.

    FR1 and FR copper sheets are made of paper and FR4 sheets are made of fiberglass. Type FR1 or FR2 are lowcost, more flexible and easily machined. Besides, they do not need a chemical bath.




    The copper sheet was attached to the Carvey milling machine with double fix tape on the bottom, so as not to come loose from the base when the cut was started.




    I used the Illustrator program to handle the FabtinyISP image and export with SVG.

    Another option is to use fab.modules.org to export the image in svg.

    Using . easel.inventables software








    Then the easel.inventables software was used to export to the Carvey milling machine.


    Using this software is very simple. You should open import an SVG file and then set the cut type, and the direction you want to give your plate.



    In this software there are also some basic drawing functions, such as rotating, copying, drawing, erasing, etc ...




    You should put the following settings in easel:


    General:

  • Material: PCB cooper
  • Bit: 0.4 mm or 0.8 mm

    • Cut settings:

  • Feed Rate: 150mm / min
  • Plunge rate: 100mm / min
  • Depth per pass: 0.1 mm




    • The process of make PCBs in the milling machine is done in two parts - First remove the copper around the tracks of electronic circuit and then cut out the exterior and the holes of the board.

    First it is necessary to remove the copper around the electronic circuits.

    For this we use a tip of 0,4mm. In the software is set:


    Cut parameter:

  • Fill
  • Depth: 0.1mm


    • Then it is necessary to cut the copper plate.

    For this we use a tip of 0,8mm. In the software is set:


    Cut parameter:

  • Outline
  • Depth: 1,7 mm (cooper sheet thickness)


    • At the end the plates were cleaned and passed with steel wool to remove some imperfections.

    Assembling . PCB


    The electronic components were then soldered to the PCB using a soldering iron.


    After soldering the components in the PSB it is necessary to verify that all are properly welded and if the copper line has not risen.


    A multi-meter was used to check for short between Vcc and GND.


    PROGRAMING ISP








    Last week 4 I drew an ISP, now it's time to program it.


    I started by following the instructions on the site "FabISP: Programing", to program the card on my Mac computer.



    I started by downloading and installing on my Mac from:

  • Crosspack AVR
  • XCode from the Apple App Store
  • FabISP Firmware for MacOS 10.8.2




    • I connected the FabISP Board I made, in the programmer plugged in to the 6-pin programming header. The light from my ISP came on.


    Then I edited Makefile with TextEdit, putting the "atmelice" in the line corresponding to the white programmer with a blue line, which is what I was using. As an example:

  • AVRDUDE = avrdude -c atmelice -P usb -p $ (DEVICE)

    • I saved the file and ran on the command line, the commands:

  • Make clean
  • Make hex

    • They ran successfully.


    Then I prescited to set the fuses on your board with the external clock, so I ran the command:

  • Make fuse

    • That did not work.


    The mistake was that the Mac did not have the drives to read the correct ISP. I tried installing the drives but I could not solve the problem.


    So I went to a computer with Ubuntu and repeated the process. When it came time for set the fuses, I also could not program the board.




    At this point I realized that my problem was not in the programmer, but in my ISP board. Some component was badly welded and the connections were not being done well.



    So I started soldering a new ISP board.


    I made several attempts to program my second ISP board that also did not work.


















    I was about to give up, but I decided to re-produce a new ISP board.

    This time I was more careful with the board. After cutting the board at the milling machine, I rubbed the board very well to remove some burrs and started to weld again.











    And I ran the command:

  • Avrdude -P com18 -b 19200 -c avrisp -p attiny45 -U flash: w: main.hex

    • This time my ISPboard started programming. Wooo! Success!








    After that I connected my ISPboard directly to the computer to verify if myISP is working correctly.

    I wrote "lsusb" at the command line on a ubuntu and mac computer and did not recognize my ISP. On windows I tried to look for the USB and also did not recognize.

    This time the problem was because it had a wrong resistance. I changed resistance and it was okay.



    The last step was to remove the 0 ohm resistor and solder bridge.

    And now my ISP can be used as a programmer to program other boards.

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