Electronics Production

This week's assignment is to characterize the design rules for PCB production (in-group); to mill, solder and test an in-circuit programmer (individual).

* All RML files can be downloaded here.

* To me, electronics is a whole new world, and therefore I need to go through tutorials about basic concepts regarding electronic components and circuits.

* This week's group assignment is to mill a line test in order to understand the machining process.

* I need to individually make an ISP, and I randomly chose the FTDI SERIAL board and the UPDI adapter. I also attempted to use another method for fabricating PCBs.

Understanding electronics and the boards

Yes, you're right, I'm that type of person who needs to understand what I'm doing before doing it. After digesting notes from Oscar's classes, I followed this tutorial to organize better all pieces of knowledge. Allow me to go through a very long note without any images attached, or go straight to the assignments below.

Electricity and how it works

Circuit and PCB

Ways to wire components

Basic components

Micro-controller and micro-processor

Communication between circuits

In order for individual circuits to transfer information, they must share a common communication protocol. There are 2 types of communication protocol: parallel and serial.

Available ISPs at Fab Lab Barcelona

In-circuit programmer (ICP): also known as in-system programmer (ISP) or serial programmer, allows micro-controllers to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to being installed. Micro-controllers are usually programmed through an ISP unless there is a bootloader (a piece of firmware) in the micro-controller that allows installing new firmware without the need of an external programmer.

For the different types of chips, there are different dedicated hardware programmers that allow them to communicate with the outside world. At Fab Lab Barcelona, we have:

That's it, enough knowledge for this week. In 2 weeks, I will try to learn more about how to understand circuit diagrams and how to design a circuit board.

Manufacturing the boards

Finally, the nightmare has come. I have never been good at electronics when I was in high school, and no one has ever considered me as a neat-handed person. Fortunately, the workflow was quite simple.

Group assignment - Characterize PCB production rules

The goal of this group assignment is for us to know the potential gaps between our traces, or how thin the traces could be. Since the milling machines were always occupied and the booking system at Fab Lab Barcelona was not really effective, our class couldn't have a chance to do many group tests. In the end, we were able to finish only 1 group test with the participation of the whole class.

We used the Roland MonoFab SRM-20 machine to mill this test file provided by the instructors. Detailed specs of the machine:

We prepared the .rml files using Fab Modules. The workflow of Fab Modules is pretty straightforward, and here are some recaps of steps followed:

We used Roland VPanel controller to adjust the milling start point, the feed rate, and the spindle speed. Detailed summary of how to use the milling machine and VPanel:

And here you go the result of the test:

We had an issue with the outlines cutting. One side was not cut completely. We managed to generate the file multiple times and did the process again, but we still had the same problem. However, we could tell from the failed test that using the default settings of Fab Modules, the machine is able to mill up to 0.01mm thin trace.

What I personally learned

Individual assignment - Mill and solder the FTDI SERIAL board and the UPDI adapter

In order to save time and materials, I teamed up with Roger Anguera, Antoine Jaunard, and Marco Cataffo because all of us were going to make the FTDI board & UPDI adapter. We did not expect that due to this we faced a lot of problems which perhaps we would not know of while milling a single board. I also learned how to mill multiple boards at the same time which is useful for my own Final Project.

mods vs. Fab Modules

We tried to use mods to create our first .rml files for the traces of the FTDI SERIAL board. The workflow is a bit more complicated than Fab Modules, but is still digestible in general.

Some essential steps to follow:

After generating the first .rml file, I decided to go back to Fab Modules for its Tue-friendly UI. In order to mill 4 FTDI boards at the same time, we had to generate 4 files with 4 different origins: 0,0,0; 25,0,0; 0,35,0; and 25,35,0. For milling 4 UPDI adapters, we exported 4 files with 4 different origins: 0,0,0; 25,0,0; 0,25,0; and 25,25,0.

Milling the board

We used the same SRM-20 machine and followed the same above-mentioned steps to mill the 4 boards. Do I look like I was enjoying fixing the milling bit?

Below is a video recording the milling process:

The first time we milled the FTDI boards, the Z-axis wasn't defined correctly and some un-milled parts remained on the PCB after the process. The un-milled parts are a bit coppery shiny compared to the rest. We had to restart the process and mill the boards a little deeper.

We then had a problem with the UPDI adapters. We forgot to set the z-axis of the home point to be greater than 0, and that's why it made a scratch across the milled parts. Since there were places left, we milled 2 more UPDIs with zhome=12mm and the new origins: 50,0,0 and 50,25,0.

Final pieces came out neat!

I used a multimeter to troubleshoot issues with my PCBs. A multimeter is a device used to measure electric current (amps), voltage (volts) and resistance (ohms). After ensuring the necessary connections, I moved forward to soldering the components.

Soldering components

Once I had the milled pieces all-good, I started the soldering process. I wrote down a shopping list of all required components and collected them from available components at the Fab Lab.

It took me plenty of time and patience to solder the components, especially the tiny IC. I even burned my hair while trying to see more clearly with my bare eyes, since the LED light equipped loupe gave me headaches. Then our instructor Rutvij Pathak said one magic phrase that saved my life: "Solder like you're painting with watercolor!" And here you go the pretty, shiny, and conductive (after testing with the multimeter) result:

I tested the board with Santi's computer, and it was detected!

However, when I tried to test it with other computers, it couldn't be detected. After checking whether all connections were in beep-beep mode once again as Oscar suggested, I put more solder to one of the resistors, and finally, the board was detected on my Macbook!

Things I learned during the soldering process:

Additional delivery - Vinyl-cut the SWD adapter

After finishing the minimum requirements of this week, I tried to explore another PCB manufacturing process which is vinyl-cutting the board using copper vinyl sheet. For this extra ball, I chose to cut the SWD adapter. Josep guided me through the process since he had experiences cutting the copper vinyl before.

The steps followed were quite similar to what I did last week with the Roland CAMM-1 Servo GX-24 machine. The only difference was that I had to stick the copper vinyl on top of a plastic sheet, and modify the Force settings to be a bit lower, around 80 gf.

The trickiest part of this was peeling out the parts that I didn't want from a tiny board (those are the parts usually removed in the milling process). The copper vinyl might be thin, but not flexible. A good tip here was to use 2 tweezers at the same time, 1 tweezer to peel and the other to fix the positions of the parts I want to keep. After struggling for a while, I got my pretty cut board which I was quite happy with:

I decided not to proceed with the soldering process since I realized soldering over those not-so-clingy traces can be a real pain. I might want to try it out if I had some extra hands, and if so, I would solder as if I were performing an Ayurvedic massage.

Conclusion

It was a useful week since electronics was one of the most important skills that I would like to acquire during the Fab Academy. This week is all about showing our capabilities of making the PCB, but I feel more confident to explore further the designing and programming process.