Week 8: Electronics Production

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

I used a CNC milling machine to cut the board.

CNC Milling CNC milling the copper isolation channels

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