Voron filament dryer

Arduino Nano firmware for a chamber dryer with four SHT31 humidity/temperature sensors, PID heater control, and PWM fan mixing.

Pinout (Arduino Nano)

All settings below are defined in include/config.h.

Signal	Nano pin	Notes
I2C SDA	A4	Shared bus (Wire)
I2C SCL	A5	Shared bus (Wire)
TCA9548A mux	I2C 0x70	8-channel I2C multiplexer
SHT31 sensors	Mux channels 2, 3, 4, 5	One sensor per channel
SHT31 address	0x44	ADDR pin low; use 0x45 if ADDR is high
Fan	D5	24 V fan via N-channel MOSFET (hardware PWM)
Heater	A2	Solid-state relay (burst control)

USB serial: 115200 baud.

Dev setup

PlatformIO

This repo uses the PlatformIO CLI (see .vscode/tasks.json). If PlatformIO is already installed under ~/.platformio/penv/, use that directly — you do not need to run the web installer again.

~/.platformio/penv/bin/pio --version
~/.platformio/penv/bin/pio run              # build
~/.platformio/penv/bin/pio run -t upload    # flash
~/.platformio/penv/bin/pio device monitor   # serial monitor

On Arch Linux / CachyOS, install via the package manager if you prefer:

sudo pacman -S platformio

If upload cannot find the port, add to platformio.ini:

upload_port = /dev/ttyUSB0    ; or /dev/ttyACM0, or a /dev/serial/by-id/... path
monitor_port = /dev/ttyUSB0

List available ports:

ls -la /dev/serial/by-id/

Serial port permissions (Linux)

Recommended — udev rules (one-time, works in Cursor without re-login):

sudo ./scripts/install-udev-rules.sh
# unplug and replug the Arduino

This installs PlatformIO’s 99-platformio-udev.rules (covers CH340 clone Nanos and other common adapters).

Alternative — group membership:

# Arch / CachyOS
sudo usermod -aG uucp $USER

You must fully log out of the desktop (not just reboot or open a new terminal) so id shows the new group. Cursor’s terminal often keeps the old group list until you restart Cursor after logging out.

Immediate workaround (no sudo, current terminal only):

sg uucp -c "$HOME/.platformio/penv/bin/pio run -t upload"

Verify access: test -w /dev/ttyUSB0 && echo ok

First run

1. Flash firmware and open the serial monitor at 115200 baud.

2. Confirm TCA9548A detected and four valid sensor channels (ch2–ch5).

3. Find stir fan speed (optional — default is PWM 178, ~70%):

   target 0
   fanchars
   

   Sweeps 30%, 100%, 60%, 80% fan — heats to max 60°C corner at 100% heater. Cools to 40°C avg between runs. Skips a fan speed if 60°C isn't reached in time. Optional midpoint refine if best isn't at 30% or 100%. Or: python3 scripts/fan_characterize.py. When done, fanchars save writes the winner to EEPROM (or skip and keep the 178 default).

4. Tune heat PI (stored in EEPROM on autotune complete):

   target 0
   pid default
   autotune 50
   

   Emergency cutoff is fixed at 70°C — you can autotune at 50–55°C with ABS in the chamber while hot corners stay below that.

5. Dry at your target — fan runs at stir PWM (default 178) whenever target > 0, including heat-up. Override with fan <pwm>; fan auto returns to default. Fan auto-off below 40°C applies only in idle (target 0).

Send help over serial for all commands (target, fanchars, fan, log on/off, status, pid, etc.).

Raspberry Pi control

On the Pi, use the curses TUI to set targets and monitor the chamber (SSH with a TTY: ssh -t):

python3 scripts/capture_csv.py tui

Keys: 0 idle · t target · p material presets · f/F fan · l CSV log · a autotune · : command · q quit

Headless CSV-only logging (e.g. systemd) is documented in pi-instructions.md.

Filament drying table

Filament	Dryer temperature	Drying time (hours)
PLA	50–55 °C (122–131 °F)	> 6
ABS	60–65 °C (140–149 °F)	> 6
PETG	60–65 °C (140–149 °F)	> 6
Nylon	70–75 °C (158–167 °F)	> 24
Desiccants	60–65 °C (149 °F)	> 12
PVA	40–45 °C (104–113 °F)	> 24
TPU/TPE	50–55 °C (122–131 °F)	> 8
ASA	60–65 °C (140–149 °F)	> 8
PP	50–55 °C (122–131 °F)	> 6
HIPS	60–65 °C (140–149 °F)	> 8
PC	70–75 °C (158–167 °F)	> 12
PEEK	120–125 °C (248–257 °F)	> 24