W04 Electronics Production
Building FabISP
In-system programming (ISP), also called in-circuit serial programming (ICSP), is the ability of some programmable logic devices, microcontrollers, and other embedded devices to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to installing it into the system.
There are several mutually-incompatible in-system programming protocols for programming microcontroller devices, including PIC microcontrollers, AVRs, and the Parallax Propeller.
The View button located on the right side on the machine pauses the running operation, and brings the base plate to the front, making it possible to inspect the copper blank in between the operation.
The Orange Buttons below the view button, are the buttons to move the end mill in the vertical direction.
PCB Fabrication
Preparing the Modela
A sacrificial board is to be placed on the machine base so that when you cut all the way through the top one, it won't damage the bit or the machine's table. Affix the sacrificial board to the mill's metal table with flat 2 sided tape. In my case, the sacrificial board was already affixed.
Affix the PCB plate to cut on top of the sacrificial material with flat 2-sided tape.
I used a scrap PCB material, so I entered the x and y value as per the placement of the cut piece board.
Turn on the Modela MDX-20
The Roland modela MDX-20 is connected to the fablab laptop with the fabmodules already installed.
- Run fab modules in the terminal
$ fab
Select input as PNG, output as Roland Models .rml and click the "make_png_rml" button to open the new window.
There are two processes undergone:
- Mill traces
- Cut Outline
Mill Traces
For traces, I used the 1/64th inch V bit. Fab modules will automatically calculate the offsets for the thickness of the bit you choose.
- Select the option From "PNG" To "Roland Modela". Click on the make pngrml option
- Load trace png file.
- Select the "Mill traces 1/64" option and verifies appropriate parameters are selected.
In my case, I used
offset=-1,
speed=4mm/s and
2D z=-0.2mm.
- To calibrate the Z-axis, push the Up and Down buttons until the motor is about 5 mm over the surface, then using an Allen key, let the drill touch the copper gently supporting it with your other hand. Once it's touching the board, secure it away with the Allen key.
- "Make path" to review the board, "Make rml" if all set then, "Send IT"
Cut Outline
Once the PCB trace is done, we need to cut the FabISP board from the larger board.
Use the same process as before to change the bit from 1/64th" bit to the 1/32" bit.
To do it, go to fabmodules main window and repeat the procedure, but selecting the
- Load trace png file.
- Select "Cut out board (1/32)" option and verify appropriate parameters are selected.
In my case, I used
offset=1,
speed=0.5mm/s and
2D z=-1.8mm.
- Entered the x and y value as previously entered.
- Calibrate Z axis as done previously
- "Make path" to review the board, "Make rml" if all set then, "Send IT"
Note
- To cross check the position I clicked the "move to Xmin and Ymin" button
- Write down these values as you'll have to use them again for cut outline process or if something goes wrong
- If the spindle doesn't stop on its own, click the button again.
- The 0,0 coordinate of this machine is at the bottom left corner of the grid design on the metal plate
Once the PCBs are finished being milled, you can move on to soldering.
Soldering the Components to the FabISP Board
Order of soldering
- ATtiny45
- Red Led
- Green Led
- Zener Diodes
- Resistors
- Capacitor
- ISP head
Have you?
- I have Shown how I made and programmed the board
- I have explained any problems and how I fixed them
- I have Included a ‘hero shot’ of my board
