Electronics production

Week 5

The assignment this week was in 2 parts one group project and one individual assignment.
The group assignment is to characterise the specifications of our PCB production process.
The individual assignment is to make an in-circuit programmer by milling the PCB,
then optionally trying other processes.

Group Assignment

In the group project we tested the Rolland mill. We are checking how thin the lines can be. The documentation is on our group website.

FabISP

I started by using the modela milling machine.
First find everything you need. You need scissors, double sided tape, copper plate, small hexagon, milling cutter and a putty trowel.

Make sure the machine is turned off and put the right milling cutter in, in my case a 1/64”,
and put the copper plate on the milling machine. Download the png files for the traces and outlines. I made the FabISP from David A. Mellis.
Next I have to connect the computer to the milling machine and make it “listen”. To do that I have to first turn on the machine and press view.
Open terminal in Linux, go into the folder for mod_server and then write "node mod_server.js".

Then open fabmodules.org in an internet browser. I used the old one but you can also use the new version.
I go into input format and choose image and find the png image for the traces.
In output format I choose Roland mill because that is the milling machine we have but if you have some other kind just pick that one.
In process I choose PCB traces (1/64). In machine choose MDX-20 and choose a starting point for x and y.
When the milling machine is in the right x-y position press the down button until it is around 12mm from the copper board,
release the milling cutter down so it touches the copper plate, do this gently so the milling cutter won´t brake,
and tighten the screw, now you have set the z position.
If the machine is connected differently then with a USB you have to change the command line,
in my case I have to take out the U and the B in USB and change the cut depth to 0.2.
Press calculate and the machine will calculate how it will cut out the hello board.
Double check if your settings are right and if everything looks good press send and the machine will start cutting.

To do the outlines you have to change to the right milling cutter, 1/36”, and do everything over,
the things you have to do different is in process choose PCB outline (1/32) and do not change cut depth.
Make sure you have the same x-y position and that you press calculate before you press send.

When the circuit board is all cut out press view and turn off the machine.
Take the board out and clean it with water and soap.

here is a video in Icelandic about how to use the milling machine

I printed the picture of the board and started soldering on the right components.
It is best to start with the small parts and end with the bigger ones and start in the middle and work out.
Some people like to find everything first and then start soldering but I like to find each component as I go.

To program the circuit board I took an old fabisp from Frosti and connected it to my fabisp.
Make sure the ribbon cable is connected correctly, vcc to vcc. And that the jumper is soldered. Then save the firmware zip file, Can be found here.. Unzip the firmware using the command line "unzip firmware.zip"
Next write "make clean" then "make hex" then type "sudo make fuse". Next type "sudo make program" Now your fabisp should be ready.

The ISP workes and can be found in the device management when plugged in to the computer.

Step response

I also made a step response. I made the hello.load.45 that Neil Gershenfeld made.
You do the same steps as before to mill it and to solder it.

When I was done soldering I found a 2*2 FCI header that already had a ribbon cable stuck to it
but if it was not already stuck to it you can easily do it yourself. Then I solder a copper foils to the wires.

To program it I used my fabisp and connected it to the hello.load.45, here I also had to make sure the ribbon cable was correctly connected,
the vcc in the fabisp and the v in the load, to check if it is right I use the multipurpose meter and if it makes sound it is correctly connected.
Then I connect the Ftdi and I also have to make sure it is correctly connected. When everything has been correctly connected.

I got the drawings in the archive for FabAcademy 2018 under input devices.
Then I saved the "hello.load.45.c", "makefile", and "hello.load.45.py".
The hello.load.45.py is to check if it works so you do not need it if you do not want to check it later.
Then I open terminal, open the folder I put this into and write "sudo make -f hello.load.45.make program-usbtiny" and it should be good to go.

To check if it works write "python hello.load.45.py /dev/ttyUSB0" and the program to check it out should open.
I soldered 4 copper foils to the FCI header, 1 to each wire, but only one wire works at a time it just depends on which way the header is put on.

Problems and solutions

To make it easier to connect the ribbon caple and the Ftdi I used a marker and marked the VCC on the fabisp and marked the V,
the Ftdi where the black ribbon should be connected and the sensor.
The problem I had in this week was only soldering, it was not going to well for my and a lot of ugly soldering was happening.
The circuit boards did both work even tough the soldering was not the best.
I think the only solution to that is just practice.

Software I used

Microsoft Photos - For photo editing.
Gimp -For photo editing.
Windows Movie maker -For editing the video.

Files from this week