41 lines
1.5 KiB
Markdown
41 lines
1.5 KiB
Markdown
# rpi-fan-control
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Daemon that reads CPU temperature and toggles a fan on GPIO pin 17. Uses hysteresis to avoid rapid on/off cycling.
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## How it works
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Polls `/sys/class/thermal/thermal_zone0/temp` every 1.5 seconds. Fan turns on when temperature crosses `threshold + variance`, turns off when it drops below `threshold - variance`. With defaults (55°C threshold, 5°C variance), that means on at 60°C, off at 50°C.
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## Hardware
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GPIO pin 17 → relay or MOSFET → fan. Nothing else special.
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## Install
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Requires `libgpiod`. Build with cargo:
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```sh
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cargo build --release
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```
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For NixOS there's a `service.nix` that wires everything up. Drop it into your configuration and enable the `rpi-fan-control` systemd service.
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## Config
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Copy `example_configuration.toml` to `/var/fan_control/config.toml` and adjust:
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```toml
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threshold = 55.0 # °C
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variance = 5.0 # fan on at threshold+variance, off at threshold-variance
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interval_ms = 1500
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gpio_line = 17
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gpio_chip = "/dev/gpiochip0"
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log_path = "/var/log/fan_control.log"
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```
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All fields are optional, the defaults worked fine for me.
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## Legacy C version
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There's an `archived-c` branch with the original implementation. It's a single C file that runs as a one-shot binary via systemd timer (fires every minute), persisting fan state to `/var/log/fanstatus` between invocations. It uses pigpio instead of libgpiod. Same hysteresis logic, same defaults. It works, but I decided to rewrite it in Rust because it's blazingly faster. /s
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