Week 4 Electronics Construction I: Fab ISP

This week we followed a fab module to make the fab ISP. This was done in three steps. First, we used the Roland Modela to make the PBC. Next we used a vinyl sticker to apply solder to the contacts, populated the board with components, and then they were fused into place with a toaster oven. Finally, we made a wire and programmed the ATtiny.


Milling the PBC
File here
We used the Roland Modela to mill the FabISP using a fab module called make_png_rml. Instructions for instillation and running are here.

Setting up the Modela Double sided tape is used to attach a sacrificial layer of a blank PCB to the bed of the Modela. Double sided tape is then used to attach a board to mill onto the sacrificial PCB. Take care to avoid air bubbles in the tape, as you wan the surface to be as flat and smooth as possible.

A 1/64" drill bit is used for milling traces. This drill bit is tiny and fragile. Handle with care. Only use one set screw in setting up the bit. Workflow consists of:
1) Unscrewing the set screw on the drill of the modela and putting a 1/64" inch bit in deep, reattaching the set screw.
2) Pressing the view button the the modela, moving the drill and bed into place.
3) Aligning the drill bit above the lower left corner of your board to be drilled using the fab module settings (more about this below.)
4) Pressing down on the Modela, lowering the bit close to the PCB.
5) Unscrewing the set screw, being careful to not let the bit drop onto the board. Instead, hold the bit and let it set onto the top of the board gently.
6) Rescrew the set screw with the bit touching the board.
The module has various settings.

1 is the size of the bit. A 1/64 inch bit is used to make the traces.
2 All of the settings at 2 are automaticly changed after you set the bit at 1. I never messed with them.
3 is used to line up your the lower left corner of the png file you are milling to the lower left corner of the place where you want the board to be drilled on the Roland. These numbers need to be manually set each time you mill a board.


Populating the Board
The first step was to use the vinyl cutter to make a vinyl stencil where solder would go on the FabISP board. I used the stencil to quickly cover the contacts with a thin layer of solder paste. The stencil was then removed. Then, the board was populated with the appropriate parts. Finally, the board was baked in a Cuisinart toaster oven on convection bake at 500F until the solder started to shine (began to melt.) The board was immediately pulled from the oven, allowed to cool, and all the components were firmly in place.






Programing the Board
Preparation: The two jumpers, one just below to the right of the ATtiny, one in the lower right corner need to be soldered manually.

This firmware was used to program the ISP. The FabISP board connects to the computer through the micro USB port. Then, using the command line in the firmware directory, the following four commands were issued:

sudo make clean
sudo make hex
sudo make fuse
sudo make program

Disconnect from the computer, disconnect the jumpers, and we have a programmed FabISP.


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