Week 8 – Electronics Production

pitch timer PCB connected to Nextion display and components — ESAN Fab Lab

Fab Academy

Electronics Production — Milling and Assembling the pitch timer PCB

June, 2026

Group assignment
Measure the power consumption of an output device.

Individual assignment
Add an output device to a microcontroller board you've designed, and program it to do something.

What I knew beforehand

Before this week I had no experience milling PCBs or producing a physical circuit board from scratch. My background is in economics and entrepreneurship — the closest analogy I had for this process was managing a production workflow: a sequence of steps where each one has a precise specification, and an error at any stage propagates into every stage that follows.

What I did bring from previous weeks was the schematic and PCB layout I had designed in KiCad for my final project, pitch timer. This week was the moment to take those files off the screen and turn them into copper and FR4. The individual assignment asked me to add an output device to a board I had already designed and program it to do something — which for pitch timer meant connecting and programming all three output devices together: the Nextion HMI display, the WS2812B LED strip, and the passive buzzer.
This week's documentation covers a critical milestone: taking the PCB I designed in Week 6 off the screen and milling it in copper on the Makera Carvera. The workflow — KiCad → Gerber → Gerber2PNG → Mods → Carvera Controller — was new to me in every step. What made it significant was that this was not a practice board; it was the actual PCB for my final project, and by the end of the week it was milled, soldered, and running firmware that coordinated the Nextion display, the LED strip, and the buzzer simultaneously. The process also gave me a concrete appreciation of something abstract: that in hardware, iteration is expensive in a way that software iteration is not. A bad trace on a milled board means starting the milling process over.

Group assignment

I worked with my colleague Jhasmin Ayala

Check this link

Individual Assignment — The Pitch timer PCB

I modified the PCB I originally designed in Week 6 to use it in my final project. The updated board is designed to connect:

(01) WS2812B RGB LED strip
(01) Passive buzzer
(01) Nextion NX4832T035_011 HMI display
Three 2-pin screw terminals for 5V external power input

The result is shown in the schematic and PCB layout below:

KiCad Schematic Editor — pitch timer Final_PCB schematic with XIAO RP2040 and all connectors

KiCad PCB Editor — Final_PCB routed layout, board dimensions 57 x 40.51 mm

The Machine: Makera Carvera

At the ESAN Fab Lab we have the Makera Carvera — a smart desktop CNC router designed for milling, drilling, engraving and turning diverse materials from home or the workshop. It stands out for automating complex manual processes such as bit changes and leveling.

Makera Carvera desktop CNC router — official product photo

Key technical specifications:

Specification	Value
Work area (X × Y × Z)	360 × 240 × 140 mm
Spindle	200 W motor, up to 13,000 RPM
Automatic Tool Change (ATC)	Multiple bits, automatic change in <10 seconds, no manual intervention
Auto-leveling probe	Integrated — adjusts height to the millimeter to avoid machining errors on uneven surfaces
Movement precision	0.01 mm
Axes	3-axis; compatible with optional 4th rotary axis module
Laser module (optional)	10 W — engraving and light cutting of soft materials
Compatible materials	Wood, acrylic, PVC, aluminum, brass, carbon fiber, resins, PCB (FR4)
Dimensions / Weight	580 × 520 × 540 mm / ~42–50 kg
Connectivity	USB and Wi-Fi

PCB Milling Workflow on the Carvera

Step 1 — Export Gerber Files from KiCad

File → Fabrication Outputs → Gerbers (.grb)

In KiCad's PCB Editor I opened File → Fabrication Outputs → Gerbers, selected all required layers, set the output directory to Gerber\, clicked Plot and then Generate Drill Files to produce the complete Gerber package.

KiCad PCB Editor — Plot dialog with all layers selected for Gerber export

Step 2 — Convert Gerber Files to PNG

gerber2png.fablabkerala.in

Mods does not read Gerber files directly — it works from PNG images. I used Gerber2PNG to convert the Gerber files into high-resolution PNG images. Two separate images are needed: one for the traces and one for the outline.

For the traces image: I enabled only the Top layers — Trace and Pads — and clicked Generate PNG. I saved the file.

Gerber2PNG — Top layer Original color mode

Gerber2PNG — B/W Invert mode: white traces on black background, ready for Mods

For the outline: I enabled only the Outline layer and set Canvas Background to White, producing a black board perimeter on a white background.

Gerber2PNG — Outline layer only, black board perimeter on white background

Step 3 — Generate NC Toolpath Files in Mods

modsproject.org → Programs → Machines → Carvera → mill 2D PCB

With both PNG files ready I opened Mods and selected the Carvera → mill 2D PCB program. Mods is a browser-based CAM tool that converts PNG images into G-code toolpath files (.nc) for the Carvera.

Mods — Programs panel showing Carvera / mill 2D PCB selected

I loaded the traces PNG into the Traces image block. The full Mods canvas connects four sections: Traces image, Exterior image, the central Calculate block (mill dual-tool 2D), and the Tabs and save file blocks.

Mods full canvas — Traces image, Calculate block, Exterior image, Tabs, and save file blocks connected

I used the default values and verified that the tool slots on the machine match the positions indicated in Mods. The Calculate block has settings for two tools:

Tool 1 — Fine isolation bit (1/64" / 0.4 mm), ATC slot 4:

Mods Calculate block — Tool 1 settings: diameter 0.397 mm, cut depth 0.12 mm, offset number 2

Tool 2 — Outline bit (1/32" / 0.8 mm), ATC slot 3:

Mods Calculate block — Tool 2 settings: diameter 0.8 mm, cut depth 0.6 mm, max depth 1.75 mm

I clicked Calculate and verified the toolpaths in the 3D viewer:

Mods 3D toolpath preview — traces isolation passes shown in yellow-green

Mods 3D toolpath preview — outline cutout in blue with tab gap visible

I saved the traces toolpath using the save file block:

Mods save file block — job.nc ready, 2028 bytes

Then I repeated the process for the outline from the Exterior image section. The image must be inverted. I used the default configuration and saved the generated file.

Mods — Exterior image section with outline PNG loaded and Tabs block configured

Step 4 — Load Files into Carvera Controller

I loaded the NC files into the Carvera Controller desktop application one at a time, and verified the toolpaths in the 3D preview before running the machine.

Traces NC file:

Carvera Controller — traces NC loaded, green isolation toolpath preview and G-code listing

Outline NC file:

Carvera Controller — outline NC loaded, blue perimeter toolpath preview

Step 5 — Milling the PCB

With the copper-clad board secured on the Carvera bed and Z-zero set to the board surface using the auto-leveling probe, I ran the traces NC file first. The Carvera then automatically changed to Tool 3 via the ATC and ran the outline NC file to cut the board free from the sheet.

Makera Carvera milling the pitch timer PCB — ESAN Fab Lab

Step 6 — Result: Milled PCB

After both toolpaths completed, the board was removed from the sheet (the tab was cut with a blade) and inspected. The isolation channels between traces are clearly visible and no copper bridges or broken traces are present.

Freshly milled pitch timer PCB on the workbench — isolation channels visible, connector for scale

Step 7 — Soldering, Assembly and Testing

With the board milled and inspected, I soldered all components: the XIAO RP2040 module, the connectors for the LED strip (J4), buzzer (J5), and Nextion display (J6), and the three 5V power screw terminals (J1, J2, J3).

Assembled pitch timer PCB — XIAO RP2040 and all connectors soldered, ready to connect peripherals

I then connected all three output devices to the board and uploaded the firmware to the XIAO RP2040 using the Arduino IDE.

pitch timer system fully connected — Nextion display, PCB with XIAO RP2040, buzzer, and wiring

The firmware uses a non-blocking state machine with millis() to coordinate all three output devices simultaneously:

Output Device	Protocol	XIAO Pin	Function
Nextion NX4832T035_011 HMI display	UART — Serial1, 9600 baud	TX / RX	Shows countdown MM:SS; sends touch commands (START, PAUSE, RESET, PRESET:3/4/5)
WS2812B LED strip — 16 LEDs	NeoPixel single-wire	D0	Green → Yellow → Red as time decreases; solid Red at finish
Passive buzzer	PWM tone — 2 kHz	D1	5-second alert tone when countdown reaches zero

The video below shows the complete system running — the Nextion display counting down, the LED strip changing color, and the buzzer triggering at zero:

pitch timer running: the Nextion 3.5" HMI display shows the PITCH TIMER interface with START, PAUSE, and RESET touch buttons and the MM:SS countdown. The WS2812B LED strip responds in real time as the countdown progresses and the XIAO RP2040 receives touch commands from the display over UART.

Reflections

This week made the connection between digital design and physical fabrication concrete and irreversible. Once you mill copper off a board there is no undo — which forces a precision of thinking at the design stage that is genuinely different from iterating on a screen. Every trace width, pad clearance, and component placement has a consequence in copper and FR4 that you live with.

The Makera Carvera's automatic tool change was impressive in practice. Switching from the fine 1/64" isolation bit to the 1/32" outline bit happened automatically and cleanly, without any manual intervention. For a board as intricate as the pitch timer PCB, that automation is what makes in-house milling a realistic production method and not just a demonstration.

The most striking insight was the compression of the value chain. The full path from schematic to physically running board — KiCad design, Gerber export, Gerber2PNG conversion, Mods toolpath generation, Carvera milling, soldering, and firmware upload — is achievable in a single working day in a Fab Lab. That speed of iteration is a genuine competitive advantage for early-stage hardware ventures.

Resources

XIAO_code_01.ino — pitch timer firmware (Arduino) final_project_hmi.tft — Nextion HMI display file