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fan-control: continuous linear curve (replaces discrete step-bands)

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Replace the step-band fan curve with a continuous linear ramp — the bands
flapped at edges (e.g. 45<->65%). Web-researched: linear + 2-3C hysteresis
is the homelab standard; PID is overkill for this slow thermal loop.
fan% now interpolates between env-tunable anchors:
  COOL  50C/30% -> 83C/100% (~2.1%/C; ~51% at the ~60C equilibrium)
  QUIET 68C/20% -> 83C/100% (near-silent until ~70C)
Both reach 100% at the 83C ceiling. Anti-oscillation: asymmetric
hysteresis (fc_decide) + a MIN_STEP (3%) min-change threshold.
41 bash tests green; deployed + verified live (59C -> 49%, smooth).

[ci skip]

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Viktor Barzin 2026-06-05 10:29:35 +00:00
parent 945c1936e3
commit 324f2dc3bf
4 changed files with 67 additions and 62 deletions
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docs/runbooks/fan-control.md
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@ -55,7 +55,7 @@ Edit `/etc/fan-control.env` on the host, then `systemctl restart fan-control`.
Common knobs:
- `HOLD_SECS` — how long to stay quiet after the garage door last moved (default 900 = 15 min).
- `CEILING` — temp at which we abandon manual control and let the firmware take over (default 83).
- Curves themselves are arrays (`COOL_CURVE`, `QUIET_CURVE`) near the top of the script.
- Curve shape: **linear anchors** near the top of the script — `COOL_T_LO/COOL_P_LO/COOL_T_HI/COOL_P_HI` (default 50°C/30% → 83°C/100%) and `QUIET_*` (68°C/20% → 83°C/100%); fan% interpolates linearly between them (replaced the old discrete step-bands). `MIN_STEP` (default 3%) = smallest fan-% change worth an IPMI write (anti-jitter); `DEADBAND` (3°C) = ease-down hysteresis. Lower `COOL_P_HI` or raise `COOL_T_HI` to run the top end quieter; steepen by raising `COOL_P_LO` / lowering `COOL_T_LO`.
## Deploy / update