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

Flash firmware and open the serial monitor at 115200 baud.
Confirm TCA9548A detected and four valid sensor channels (ch2–ch5).
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).
Tune heat PI (stored in EEPROM on autotune complete):
```
target 0
pid default
autotune 50
```
Cutoff follows target (target + 12°C, max 95°C) — e.g. ABS at 55°C trips at 67°C corner, nylon at 80°C at 92°C.
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

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