GroupTask

This week we went to the lab to use the electronic board milling machine. The task was to characterize as a team the design rules for their printed circuit board production process. Together with the team we reviewed the available materials and got down to work. You can read more about the group task at 💻Mayra Ascencio's web page 💻

Milling machine

This season we were on lockdown because of the Covid-19 pandemic, it was very difficult to access the lab, only a few people could go. So we were able to get into the space to use the CNC milling machine, the Roland Modela MDX 20. Our course partner, Hayashi Mateo recovered the machine that was not working by putting an arduino, a shield and programming it again. So with the machine running we learned the first steps to use the CNC plate milling machine.

Workflow for sending a PCB to a board house

Now we will experience the quote flow for a pack of PCB boards in a Chinese company. For this exercise we choose the company PCBWAY, which is one of the best-known PCB board manufacturing companies in the world.

First ISP PCB design

In this experience we learned how to design in EasyEda, a software to design electrical circuit boards. We investigated together with Mayra in several stores and did not find availability of several SMD components used in the Academy exercises, such as the Attiny45 microcontroller to design the fabISP, so together with the Fab Lab Peru team, we organized a local purchase and an import purchase. What we got locally was with a lot of effort because during this week we were not allowed to leave the city without the corresponding permits. With the available components, some SMD, some not, I decided to develop my Arduino compatible programmer board, using the ATTINY85 microcontroller and the available components, under the guidance of Hayashi Mateo.

Second ISP PCB design

I did the second design, I changed a little the positions and the shape of the card, I was testing the external shape. I improved the quality of the traces, and the separation between them to optimize the cutting.

Starting to solder

At this stage it was fun to get all the soldering implements, and to have my own kit. Although my brother says I wasn't taught how to solder well, I think I learned well and the PCB, the fabISP looked decent.If you are going to buy a soldering iron, I recommend the Goot brand of 20w or 30w, it is good. And well, it is very important to have your own multimeter, just don't forget to turn it off, otherwise, the next time you use it, it won't have batteries.

Second RoundfabISP of Brian

When it was time to program my first two PCB attempts, the opportunity came for Fab Lab Esan and their instructors to support us in making our Fab ISP boards, so we were guided by Brian's tutorial and page to make them. Fortunately by this time Mayra's professional cnc cutters had already arrived in Peru.They also had a Roland Modela MDX 20 in the lab that was in very good condition💎. Finally my PCB board was cut and it has an incredible finish.

Then, I proceeded to solder all the components on the milled plate. I already had some practice so I think I got it right. The components are:

1 Attiny 45 microcontroller

2 x 1k ohm resistors

2 x 499 ohm resistors

2 x 49 ohm resistors

2 x 3.3v Zenes Diodes

1 x red led

1 x green led

1 x 100 nf capacitor

1 x 2x3 pin header

I disassembled many USB sticks, to have the component to connect it to the computer, and I tried to put it in my ISP card, but I was not successful 😥, so I just soldered the terminals and that was it.

Then, together with Mayra, we made the necessary cable to connect our FabTinyISP to the ISP programmer that Fab Lab Esan lent us, but unfortunately the Esan board did not work, maybe because it is many years old. So as another option I decided to program my ISP board from an Arduino UNO.

Programing Bootloader

Burning the bootloader on my FabTinyISP board is an essential step for the ATtiny45 or ATtiny85 microcontroller to work as an AVR programmer. This process allows me to configure the microcontroller's fuses, setting parameters such as the clock source to use the internal PLL, which is necessary for USB communication, and, later, converting the reset pin to a GPIO. I also load firmware into the microcontroller's memory, which gives it the ability to handle USB communication, interpret commands from the computer, and program other microcontrollers. By completing this step, I ensure that my board is configured at both the hardware and software level to operate as a functional ISP programmer. Without this process, my board would be nothing more than an assembled, but non-operational circuit.

Como no tenemos un grabador funcional, lo que hice fue utilizar una tarjeta de Arduino UNO as ISP, para grabar el bootloader de mi FabTinyISP.

AboutLearning

- I learned this week that electronics is a challenge and that if you don't have the right machines and materials on hand, it is difficult to accomplish these tasks.

- For electronics production, it is necessary to have a good bakelite, good milling cutters for precise cutting and also to know how to calibrate the board milling machine very well.

- The collaboration in this first stage was essential for Mayra and for me. With little knowledge in the area we had to do a lot of research on every step we took.

My Verdictfrom what I learned

- Fab Lab Peru's “Modelita” machine is not dead yet. We can revive it if we take the time. I think the Roland machines are of very good quality and last a long time.

- On the other hand, if you do not have the materials for the electronic production it is important that you import the necessary in time, in Peru some materials are still not available.

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