3D Printing
Enclosure and hardware
Printable case (top, bottom, handle, feet, standoffs), power supply mount, and an OnShape CAD model you can modify. PLA works fine; paint for a finished look.
A home coffee roaster you can build yourself.
Modified popcorn popper. ESP32 controller. PID temperature control. Roast profiles. Artisan logging. All open source.
What's in the repo
This isn't just firmware. The repository covers the full build — enclosure, electronics, software, and operating docs.
PCB
Custom control board
Eagle schematic and board files for the interface PCB. Hosts an Arduino Nano ESP32, fan speed controller, and JST connectors for the display, thermocouples, and SSR. Order from JLCPCB, PCBWay, or similar.
Firmware
ESP32 control software
State machine for roast lifecycle. PID temperature control. Dual thermocouple monitoring. Profile-based setpoint interpolation. WiFi with WebSocket streaming. OTA updates. REST API.
Popper Mod
Roasting chamber
Step-by-step guide to disassemble a 1200W popcorn popper, rewire the heater and fan, remove the stock thermostat, and install a thermocouple in the roasting chamber.
How the build works
Four phases — printing, popper mod, assembly, and software setup.
1
Print the enclosure
Print the case parts in PLA. Optionally sand, prime, and paint for a finished appliance look. The 3MF file is in the repo.
2
Modify the popper
Disassemble the popcorn popper. Rewire heater and fan. Remove the bimetallic thermostat strip. Drill and install the thermocouple.
3
Wire and assemble
Mount the PCB, Nextion display, power supply, and SSR in the case. Build the wire harnesses and connect everything.
4
Flash and roast
Upload firmware via USB or OTA. Load Nextion display firmware from SD card. Connect WiFi, create a profile, and go.
Software
The firmware runs on an Arduino Nano ESP32. It includes a touchscreen UI, web interface, and Artisan integration.
Roast profiles
Define time / temperature / fan setpoints. The firmware interpolates between them during the roast. Profiles are stored on-device and editable from the browser.
PID temperature control
Closed-loop PID keeps the roasting chamber on target. Dual thermocouples monitor chamber and exhaust temperatures.
Nextion touchscreen
3.5" display shows real-time temps, profile progress, and settings. Start/stop roasts and edit profiles on the device.
Web interface
Profile editor, debug console, and live status at roaster.local. OTA firmware updates without opening the case.
Artisan integration
Streams roast data over WebSocket to Artisan for real-time curves, logging, and analysis. Config files included.
REST API
Full API for profiles, PID tuning, roast control, and system status. OpenAPI spec in the repo.
Safety
This project controls line voltage and high temperatures. The firmware has safety systems, but understand the risks before building.
Over-temperature cutoff — heater shuts off if chamber temp exceeds safe limits.
Sensor validation — thermocouple faults and implausible readings trigger error state.
Fail-safe defaults — heater OFF, fan ON. Unknown states enter ERROR, not IDLE.
Cooling lockout — can't skip cooling until chamber is below a safe threshold.
Parts list
Everything needed for the build. Most parts ship from Amazon and AliExpress.
| Part | Source |
|---|---|
| 1200W Popcorn Popper | Amazon |
| Arduino Nano ESP32 | Amazon |
| Nextion 3.5" Display | AliExpress · Amazon |
| Custom PCB (Rev I) | Eagle files in repo |
| 24V Power Supply | Amazon |
| DC-DC Buck Converter | Amazon |
| Solid-State Relay (SSR-40DA) | AliExpress |
| K-Type Thermocouple + MAX6675 | Amazon |
| Motor Dimmer Module | AliExpress |
| Power Inlet Socket | Amazon |
| JST XH2.54 Connector Kit | Amazon |
| Silicone Wire (22ga + 16ga) | AliExpress |
Get started
Clone the repo, print the case, order the PCB, and start building.