Week 8: Electronics Production

For this week's group assignment, we explored our machine specifications and capabilities. We also tried to estimate how much it could cost to produce different PCBs.

For the individual assignment, I designed and cut a PCB so I could use it for the input and output devices weeks.

Here is a hero shot of the finished PCB:

To do my assignment, I used the Roland SRM-20, as it is the one available in our lab.

To design my PCB, I used KiCad software, which I used in the electronics design week and felt comfortable with.

Here are the steps to design the PCB:

First, I had to check which components were available in the lab so I could design the PCB around them and select the footprints in my design accordingly.
Then, I created the schematic and layout for the PCB by selecting my components and setting their footprints. Here is the schematic:

My idea was to create an expansion board for the Xiao Seeed ESP32C3. Here are the details of the design:

Red Boxes: These represent the source nodes for 5V, 3V, and GND.
Green Boxes: These represent the input and output pins for the microcontroller.
Purple Boxes: These represent external nodes that could be used to expand any node in the future.
Yellow Boxes: These represent I2C connections, so I can connect any I2C device easily.

After that, I selected the footprint for each component. Here are the details for each one:

Pink Box:
- Value: Module_XIAO-ESP32C3
- Footprint: Module_XIAO-ESP32C3
Blue Box:
- Value: PinHeader_01x04_P2.54mm_Horizontal_SMD
- Footprint: PCM_fab:PinSocket_01x04_P2.54mm_Vertical_SMD
Green Box:
- Value: PinHeader_01x07_P2.54mm_Vertical_THT_D1.4mm
- Footprint: Connector_PinSocket_2.54mm:PinSocket_1x07_P2.54mm_Vertical_SMD_Pin1Left
Yellow Box:
- Value: PinHeader_01x04_P2.54mm_Horizontal_SMD
- Footprint: PCM_fab:PinSocket_01x04_P2.54mm_Horizontal_SMD
Red Boxes:
- Value: PinSocket_01x06_P2.54mm_Horizontal_SMD
- Footprint: Connector_PinSocket_2.54mm:PinSocket_1x06_P2.54mm_Vertical_SMD_Pin1Right
Purple Box:
- Value: PinHeader_01x05_P2.54mm_Vertical_THT_D1mm
- Footprint: Connector_PinSocket_2.54mm:PinSocket_1x05_P2.54mm_Vertical_SMD_Pin1Right

💡 Note: If you cannot find the exact value (Symbol), that is sometimes fine. You just need to select the important feature, such as the number of pin headers. What matters most is selecting the correct footprint for the component you want to use.

Then I transferred my schematic to the PCB and set the design rules.

Next, I routed the connections on the PCB.

Finally, I ran the design rule checker.

After finishing the design, I exported the cutting files for the CNC machine. Here are the steps:

Go to the "File" menu and select "Plot"

In the plot menu, select "SVG" as the plot (output) format, choose the layers you want to export, then click "Plot." In my case, I exported the F.Cu layer for milling and the Edge.Cuts layer for the PCB outline.

💡 Note: Don't forget to set the correct output directory before clicking "Plot."

You can download the KiCad files and the cutting files for my PCB design: Download PCB Design Files

After exporting the cutting files, I had to prepare them for cutting on the CNC machine using the MODS website.

Here are the steps to prepare the files for cutting:

First, I resized the cutting files in Inkscape by pressing "Ctrl + Shift + R" to set the canvas size to the board size.
Then, go back to MODS, open Programs, search for SRM, and select "mill 2D PCB."

Next, I uploaded the cutting file for the F.Cu layer by pressing "select SVG file" on "read SVG" block and selecting the correct file.

💡 Note: You could also upload PNG files.

After that, I had to change some settings such as:

Select the correct cutting tool. For milling, I used a 0.4 mm tool diameter.

Check the origin, because by default it is set incorrectly, so reset it to zero.

Then, press "calculate" in "mill raster 2D" block to generate the cutting paths.

After that, check the PCB result simulation so you can verify the cutting paths.

As you can see, this path isn't correct; it is cutting the path instead of what's around it.

To fix this issue, I had to press "invert" in "convert SVG image" block

Now recalculate and see the new simulation.

As you can see, the cutting paths are now correct and it is cutting around the traces instead of cutting the traces.

Finally, enable "on/off" block before the save block so when you press recalculate the file downloads automatically.

Now you can recalculate and the file will be downloaded automatically.

Redo the same steps for the other layer.

💡 Note: I edit the stroke size for the edge cut layer in Inkscape to be 0.8 mm to match the cutting tool size, since I forgot to do it initially.

You can download the prepared files for CNC cutting: Download Prepared CNC Files

and here is the Inkscape files: Download Inkscape Files

After preparing the files, I set up the machine for cutting the PCB. Here are the steps:

First I prepared the pcb board since the one we have in our lab is big which make it not 100% flat.
To prepare the board, I had to cut it into smaller pieces that fit the machine and are easier to work with.

So I have now a flat board that make the cutting in all point equal.
Then put a double face sticky in the board so we ensure that the board will not move during the cutting process.

💡 Note: When put the double face sticky make sure that the sticks dont overlap to ensure that the board will be flat and the cutting will be accurate.

Second, I clean the machine bed to remove any debris or dust that might interfere with the cutting process and ensure the PCB board stays well secured.

Third, I placed the PCB board on the machine bed and secured it with the double-sided sticky tape.

Next, I need to set the cutting tool and adjust machine origin , here is the steps:

First, I installed 0.4 mm cutting tool in the machine.

Then, I set the X and Y axes origin by moving the tool to the top-left corner of the PCB board and setting that position as the origin for both axes.
Then, I set the Z-axis origin by lowering the tool until it just touches the surface of the PCB board, then set this position as the Z-axis origin.

💡 Note: Setting the correct origin is crucial for accurate cutting, so take your time to ensure it is done correctly.

💡 Note: I use VPanel for srm 20 software to control the machine.

Then, I started the cutting process by running the first file for the F.Cu layer.

After the cutting process finished, I clean the board to remove any debris or dust that might be on it to be ready when cutting the edge.

Next, I install the 0.8 mm cutting tool for the edge cutting and reset the origins.

Finally, I remove the PCB board from the machine bed and inspect it for any defects.

After cutting the PCB, I soldered the components to the board. Here are the steps:

First, I gathered all the components and tools I needed for soldering, including the soldering iron, solder wire, flux, and the components themselves.
Then, Started soldering the components to the PCB by following the schematic and layout I designed. I made sure to apply flux to the pads before soldering to ensure good solder joints.

Here is the finished PCB:

Here is an example of how I can use this PCB to connect a sensor to the Xiao ESP32C3 microcontroller:

Here is the physical connection:

Here is the connection diagram using Wokwi:

Here is the code I used :

// Ultrasonic Sensor Code for Xiao Seeed ESP32-C3
#define TRIG_PIN 2
#define ECHO_PIN 3
#define LED_PIN 4

long duration;
float cm, inches;

void setup() {
  Serial.begin(115200); // ESP32 usually uses higher baud

  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  // Clean trigger
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(5);

  // Send pulse
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);

  // Read echo
  duration = pulseIn(ECHO_PIN, HIGH);

  // Convert to distance
  cm = (duration / 2.0) / 29.1;
  inches = (duration / 2.0) / 74.0;

  // LED control
  if (cm < 18) {
    digitalWrite(LED_PIN, HIGH);
  } else {
    digitalWrite(LED_PIN, LOW);
  }

  // Print
  Serial.print(inches);
  Serial.print(" in, ");
  Serial.print(cm);
  Serial.print(" cm");
  Serial.println();

  delay(250);
}

I took this code from this reference above to test the sensor and change the pin numbers to match the Xiao Seeed ESP32-C3.

You could download the full code from here.

💡 Note: here is full code explanation using ChatGPT

Before I upload the code to the board, I simulated the behavior using Wokwi.

You could see the simulation from here.

💡 Note: To make the serial monitor work correctly, don't forget to enable "Use CDC on Boot", which you can find under the Tools tab in the Arduino IDE.

After simulating the code, I uploaded it to the board .

Week 8: Electronics Production

Group Assignment

Individual Assignment

About The Machine

Design Process

Export Files

Prepare files for CNC cutting

Machine Setup and Cutting

Welding

Usage Example

Ultrasonic Sensor Code:

Simulation:

Connect to the board: