4. Electronics production

"make the FabISP in-circuit programmer"
page contents:
production
programming the ISP
learning points

Making the PCB board

For this assignment we built an existing design of an ISP. There are several versions of ISPs at the Fabacademy, and we chose the FabTiny*ISP designed by Zaerc.. The final result:
Instead of etching the PCB, which is a rather toxic process, we use a paperbased material with a copper layer that can be easily milled. At the Waag Fablab, the mill we use is the Roland Modela MDX-20:
4_01_modela We were given instructions on how to set up the milling machine and how to load the the .PNG file that is sent to it. We use fab modules. In the terminal, enter fab. Then, choose pngand the Roland Modela. This opens the application that is used with the Modela.
For milling, there are two milling bits that we use:

Here you can see the first of two PNG files being loaded for milling:
4_01_png When it was time for me to mill, I had to use a piece of used material, so I needed to make sure the file would fit. From measuring I knew I had enough space, but I needed to make sure the bit would not run off from the material.
4_02_align4_02_xy
I used the controls of the software to move the bit a few centimeters to the right to make sure it would stay on the material: 4_02_align2
Here you can see the first run finished. A lot of dust if produced obviously when you mill which you can remove carefully with a small vacuum cleaner or a brush.
4_05_dust
If you want to make sure during everything is going well, pressing 'view' will pause the milling and move your work to the front of the machine. 4_04_view
The first milling job removes the top layer with the copper, leaving the copper where you actually want it for conductivity:
4_06_result14_06_result2
Now, it is time to cut the PCB free. For that we use another PNG file and different settings, including another mill bit of 1/32 inch. One of the settings in this case is the z-position, which is set to -0.6mm in this case, to optimize (= minimize) the amount of cycles the bit has to travel through the material. Setting this value to 0 would actually result in having the bit run across the surface of the material for nothing. 4_07_cutpng4_07_cut
This is what you end up with: 4_07_result
To remove the PCB board you can use a screwdriver or a tool like this: 4_08_remove4_08_out
A few closeups of the result. As you can see, despite using the vacuum, lots of dust still remains on the board. Also, looking closely, you can see how the path of the bit does not always leave precise paths. Keep this in mind when designing the board and setting the path of the bit.
4_09_close1 4_09_close2
4_09_close3 4_09_close4
4_09_close5
A view from the side with the macro lens gives a nice picture of the material that the PCB is made from: 4_09_close6
Close inspection of the board shows a tiny bit of copper that was not cut by the milling bit. this can be easily removed using a Stanley knife:
4_09_finish1 4_09_finish2 4_09_finish3 To remove tiny bits of rough material that might stick out after milling and to remove oils and dust that might damage the circuit over time, the PCB is sanded and then washed with a light soap. 4_10_sand 4_10_wash Now it is time to stuff the empty board with the components. I had the layout of the PCB and a list of components next to me at a soldering station.
4_11_stuff
When soldering, it is important to make sure the soldering iron is hot enough (test it by touching a bit of solder) and to make sure the sponge is wet so you can use it to clean the tip of the iron.
When putting components onto the board, it is good practice to plan which parts you solder first. A rule of thumb is small, then large and inside out.
4_12_close4
When adding components, I first deposited some solder onto the board and then, while simultaneously heating the board and the component added more solder to attach the component. Always check that connections are well made (solder should flow around the feet of the component and onto the board).
4_12_close1 4_12_close2 4_12_close3 Here is the board with all the components soldered onto it: 4_12_result To make sure it fits nicely in a USB port, I glued a bit of cardboard at the back so that the connections would press against the USB connections of my laptop.
4_13_usb4_13_usb2 Here is the finished board, and...it's ALIVE! Yes! What a nice feeling to have made something that works :)!
4_14_alive

Programming the ISP

Learning points:
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