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8. Electronics Production

Hero shot
This week I designed and cut the electric board and soldered til it works.

Group Assignment:

  • Characterize the design rules for your in-house PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
  • Document the workflow for sending a PCB to a boardhouse
  • Document your work to the group work page and reflect on your individual page what you learned

Individual Assignment:

  • Make and test a microcontroller development board that you designed

Learning outcomes

  • Described the process of tool-path generation, milling, stuffing, de-bugging and programming
  • Demonstrate correct workflows and identify areas for improvement if required

Group Assignment

This week’s group work page is here

Individual Assignment

First we had small lecture about milling machine.(Roland SRM-20).

Design the board

I wanted to make the board enable to put and out with my Xiao which has already pin headers. However I struggled making design with KiCad, because I couldn’t imagine the board construction. Therefore I draw the sketch several times, but I couldn’t figure it out how it works.
Fortunately, I could ask instructors from the first again on saturday, and I could design what I’m thinking.

Xiao pinout
Xiao pinout

Make the PCB board

After designing the board in Schematic Editor, I opened the PCB editor and clicked “upgrade PCB” button to transfer and update the data.

Then compact data came out.

Input the parameter data.

I moved those parts and make the circuit board.

Then I put a outline.

CLICK Filled Zone by right mouse and click each side of the area!!

Filled zone should be a little smaller than outline.



Make preparation files for milling

After making a PCB board, I have to make “cut information” files(.svg) of each step for the milling machine as follows;
1. Path traces
2. Holes for putting xiao board with header pins
3. Outside line

I used Inkscape for making those files(Instractor advised me not to use Illustrator, as files created by Illustrator are not kept the file size)

My instructors advised me 2 ways to prepare the milling data.

(1) Making one file in all function First, we have to classify the data by function such as cables, holes, and outside line. They are put in separate folders and it becomes easy to see every functional parts.

(2) Making each function files It is made 3 parts files and each has a cutting information.
Path trace file Holes file Outside line file

Put milling data to Mods and make to .rml file

I started mods application on internet mods -> https://modsproject.org/

When you push right mouse at site, the menu bar comes out.
Choose ‘program’ -> ‘open program’ -> ‘Roland mill 2D PCB’

Then the screen as follows comes out and make .rml file.

First it is read input file (svg or png file). As my file is .svg file, clicked ‘select svg file’ and select it.

Then, it is inverted the file by clicking ‘invert’ button.

Next I chose the proper end mill setting. Setting mill are

Path trace holes Outside line
End mill 1/64 1/32 1/32


I also check and modify offset position. We usually set all 0 at “origin”.

I also checked the ‘edit delete’ to ‘ON’.

After finishing the setting, push ‘calculate’ button at mill raster 2D.

When you push that button, new window comes out and show all the mill’s path. We can check how it works and correct it if we need.

I did same things for other 2files.

HOW TO MAKE MILLING DATA FILE WITH HOLES

As I made circuit with holes, I learned how to make those preparations files.

  • Path file
  • Holes file
  • Outline file

After exporting file from KiCad, you can get 2 files such as xiao-F_Cu.svg and xiao-B_Cu.svg automatically.

1) Modify at Inkscape

(1) Path File
We use “xiao-F_Cu.svg”.
xiao-F_Cu.svg
I think you can use without anything, but I paint it black at the circle.
xiao-F_Cu.svg2 -> xiao-F_Cu.svg3

(2) Holes File
First open xiao-B_Cu.svg.
xiao-F_Cu.svg3

You have to paint inside cirles to black and delete all other parts. As it makes easy, I painted another color such as red at the black cirle and then painted inside circle to black.
xiao-F_Cu.svg2 xiao-F_Cu.svg2
Outside line file

(3) Outline File
We use xiao-B_Cu.svg again. This time, we painted all black inside holes and shapes.
xiao-F_Cu.svg3 xiao-F_Cu.svg3

2) Set the data in mods

Items Invert Endmill size
Path File Do Invert 1/64
Holes File x 1/32
Outline File Invert(cut Outside) / x(cut Inside) 1/32

Milling

Tool and Materials

  • We used Roland SRM-20 for milling.

  • The copper clad laminate we used and end mills.

Setting in SRM-20

Origin of x,y and z are set.
For setting z origin, end mill is put down above the ground level and loosen the setscrew. Endmill is moved to the ground gently, and tighten the screw.

Milling data file is transferred to operating pc. Clicked ‘CUT’ button. If there is already output file on the list, you should delete all by ‘Delete All’ button it is cut all the data on the list. Then push ‘Add’ button to load the file. When you check the file and select ‘Output’ button to start cutting.

I cut 2 pieces.
First one(upper) : holes are too big.
Second one(lower) : successful cut

Soldering

I don’t have much experience with soldering, so I started practicing it. (Mines’ are not all)

I started soldering from resistor and led at the bottom.

Here I found big mistakes at the board design. I didn’t connect several gnd parts (indicated as arrow). So a instructor advised me to put a wire for connecting those pins and it worked.

I put female sockets on each port.

Female sockets for putting Xiao are soldered.

5V output male pinheader is put at right side.

Test

I did electric test on my board. First, I checked led light on test with Arduino sample program. 

int Led_pin = D3;

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(Led_pin, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(Led_pin, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(200);                      // wait for a second
  digitalWrite(Led_pin, LOW);   // turn the LED off by making the voltage LOW
  delay(200);                      // wait for a second
}

What I’ve learnt

I’ve learnt a lot this week! I couldn’t have the image of electric circuit and designed it. I learnt through designing and making PCB, now I could understood it. I was glad I could find mistakes of my PCB board by myself(that means I could understand the function!) and could correct the PCB design for future assignment.

Working files