Week 8: Electronics Production

Note: My English writing skills are limited. For this documentation, I have used AI assistance for parts of the translation.

Date: March 12 - 18, 2026

What I Did This Week

I made the control board for my Smart Reptile Habitat System. I designed the PCB in Week 6. This week I made it with a CNC milling machine and soldered all the parts.

📋 Assignment

Group Assignment

✅ Characterize the design rules for your in-house PCB production process ✅ Submit a PCB design to a board house

📎 Group Work Page

What We Learned from the Group Work

We tested trace width and clearance limits on our lab's CNC milling machine (LUNYEE 3018 PRO MAX).

Machine setup: - Endmill: 0.4mm and 0.8mm - Material: Copper clad laminate (non-fiberglass, 1.6mm) - Software: CNCjs + MODS

Test results:

Parameter Result
Minimum trace width 10 mil (0.254mm) — below this, traces break
Risky trace width 7–12 mil — sometimes breaks
Minimum clearance 20 mil (0.508mm)

Traces thinner than 0.003 inch (7.5 mil) were broken. Traces between 0.003–0.005 inch were sometimes risky. I used 0.5mm (about 20 mil) for my board design, which was safe.

Individual Assignment

✅ Make and test an embedded microcontroller system that you designed

🔧 Individual Assignment: Make and Test a PCB

I made the Reptile Monitor board. This board controls temperature, humidity, fan, lighting, and humidifier for a reptile cage.

Board features: - XIAO ESP32C6 (WiFi microcontroller) - 4 Grove connectors (I2C × 1, Digital × 3) - LED indicator (D10)

Step 1: Design the Schematic

I used KiCad 9.0 to draw the circuit.

Schematic Reptile Monitor schematic — XIAO ESP32C6 with 4 Grove connectors and LED

Components:

Reference Part Value
M2 XIAO ESP32C6 socket Module_Seeed_XIAO_Generic_SocketSMD
J1 Grove connector Relay (D0/D1)
J2 Grove connector Water Atomization (D2/D3)
J3 Grove connector I2C — SHT31 × 2 + Motor Driver (D4/D5)
J4 Grove connector Spare (D6/D7)
R1 Resistor SMD 1206 / 1kΩ
D1 LED SMD 1206

I ran the ERC (Electrical Rules Check). Some errors appeared, but I fixed them. The final result was 0 errors.

ERC Result ERC — Violations: 0

Step 2: Design the PCB Layout

I placed all components in KiCad PCB Editor. It was my first time using this tool, but I think the routing looks clean.

PCB Layout PCB layout — XIAO socket at top, 4 Grove connectors at bottom

Design rules: - Trace width: 0.5mm - Clearance: 0.5mm - GND copper fill (Direct connection) - No-Net fill zone (to reduce CNC milling area) - 4 mount holes (M3)

I ran the DRC (Design Rules Check). The result was 0 errors. There were 10 warnings for "Isolated copper fill" from the No-Net zone. This is expected — the warnings are not a problem.

DRC Result DRC — Errors: 0, Warnings: 10 (all isolated copper fill — expected)

Step 3: Export Gerber Files

I exported Gerber files from KiCad.

Gerber Export KiCad Plot dialog — F.Cu and Edge.Cuts layers exported

Exported files:

File Purpose
Reptile_Monitor-F_Cu.gbr Copper traces
Reptile_Monitor-Edge_Cuts.gbr Board outline

Step 4: Generate G-code with pcb2gcodeGUI

I used pcb2gcodeGUI to convert Gerber files to G-code.

DXF is a de facto standard CAD format. Many tools can read it — CAD software, CAM software, and CNC machines. I also used KrabzCAM in Week 7 for wood CNC milling. This week I used pcb2gcodeGUI because it reads Gerber files directly and generates clean toolpaths for PCB isolation milling. In fact, I tried KrabzCAM first — the paths were broken and I wasted a lot of time.

pcb2gcodeGUI pcb2gcodeGUI — Gerber files loaded, PCB toolpath preview

Settings:

Parameter Value
Cut depth 0.1mm
Feed rate 240 mm/min
Spindle speed 10,000 RPM

I loaded the G-code in Candle to check the toolpath before milling.

Candle G-code Sender Candle — front.ngc loaded, toolpath preview looks correct

Step 5: Mill the PCB

Board Fixture

Yoshi designed a 3D-printed PCB holder for our lab's CNC machine. It holds the board flat and tight with screws.

CNC Milling The white 3D-printed holder keeps the board in place during milling.

Setting the Origin

  1. Move the endmill to the start position by hand
  2. Click "Set Zero" in Candle
  3. Z height is set automatically by the auto-leveling probe

Auto-Leveling with Candle

Candle has a built-in auto-leveling feature. It scans the board surface and corrects for any tilt automatically. I just attached a probe clip to the endmill and ran the scan.

For more details about CNC setup, see Week 7: Computer-Controlled Machining.

Milling

I used a CNC milling machine to cut the board.

The machine removed copper around the traces to make isolation channels. After milling, the board looks like this:

Milled PCB Milled PCB — traces and pads are visible

Step 6: Solder Components

I soldered all SMD components by hand.

Soldering Soldering Grove connectors and XIAO socket

Soldering Close-up Close-up — 1kΩ resistor (1001) and LED next to XIAO socket

Soldering order: 1. SMD resistor (1kΩ) 2. SMD LED 3. Grove connectors × 4 4. XIAO ESP32C6 socket

Step 7: Test the Board

First I checked continuity with a multimeter.

Continuity Test Multimeter continuity check — no short circuits found

Then I plugged in the XIAO ESP32C6 and uploaded a Blink sketch.

Test code (Arduino IDE):

const int LED_PIN = D10;

void setup() {
  Serial.begin(115200);
  pinMode(LED_PIN, OUTPUT);
  Serial.println("Reptile Monitor - LED Blink Test");
}

void loop() {
  digitalWrite(LED_PIN, HIGH);
  Serial.println("LED ON");
  delay(1000);

  digitalWrite(LED_PIN, LOW);
  Serial.println("LED OFF");
  delay(1000);
}

Result: ✅ LED blinks correctly!

LED blink test — D10 blinks at 1 second interval

📦 Design Files

All files are in docs/files/week08/.

File Description
Reptile_Monitor.kicad_sch KiCad schematic
Reptile_Monitor.kicad_pcb KiCad PCB layout
Reptile_Monitor-F_Cu.gbr Gerber — copper layer
Reptile_Monitor-Edge_Cuts.gbr Gerber — board outline
front.ngc G-code — isolation milling
outline.ngc G-code — board cutout

🔗 Connection to Final Project

This board is the control center for my Smart Reptile Habitat System.

  • XIAO ESP32C6 → WiFi communication + sensor control
  • Grove I2C (J3) → Connect SHT31 temperature/humidity sensors
  • Grove Digital (J1) → Control relay for lighting and heater
  • Grove Digital (J2) → Control ultrasonic humidifier
  • Grove Digital (J4) → Spare for future expansion

🔧 Problems and Solutions

Problem: CAM software — disconnected paths in KrabzCAM

What Happened: I tried to use KrabzCAM (the same tool I used in Week 7). But KrabzCAM only works with closed paths. The DXF from KiCad had open paths. KrabzCAM ignored them.

How I Solved It: I used pcb2gcodeGUI instead. It reads Gerber files directly. Gerber is the standard PCB format. There are no path problems.

What I Learned: Use the right tool for the job. KrabzCAM is great for wood CNC. pcb2gcode is better for PCB milling.

✅ Evaluation Checklist

Individual Assignment

  • [x] PCB milled successfully
  • [x] Components soldered
  • [x] Board tested and working (LED blink)
  • [x] Process documented with photos

Documentation

  • [x] Design files in repository
  • [x] Images compressed (under 500KB)
  • [x] Pushed to repository

💭 Reflection

What Went Well

The CNC milling result was clean. The traces and pads are clearly visible. Soldering small SMD parts (1206) was easier than I expected. The LED blink test worked on the first try.

Lessons Learned

  • pcb2gcodeGUI is the best tool for PCB G-code generation from Gerber files
  • Direct pad connection is better than thermal reliefs for milled PCBs
  • Always run ERC and DRC before exporting

For Next Week — Output Devices

  • Connect a Grove output device to the board
  • Test I2C communication with motor driver or relay

📚 References

Last updated: March 18, 2026