Dual Curve

All Revisions

Works with all hardware revisions (Rev 1.0 through Rev 3.3).

Purpose

The Dual Curve module holds two complete 5-point temperature-to-speed curves, A and B, and lets you switch between them from Home Assistant with a single switch. Curve A is meant to be an aggressive profile (cools hard, early) and curve B a defensive one (stays quiet longer, spins up later), but both are fully configurable.

When to Use

Choose Dual Curve when you want two distinct fan profiles you can flip between, instead of constantly re-tuning a single curve. The classic case is pairing it with an air-quality automation: when the air is bad, a Home Assistant automation flips to the defensive curve so the fans stay quiet and ramp up later.

The module is sensor-agnostic. It does not read any air-quality sensor itself. Curve selection is just a switch; the automation logic lives in Home Assistant. For a single fixed curve, see Temperature Curve. The modules overview has a comparison table.

One temperature module at a time

Dual Curve is a temperature control module. Do not enable it together with Temperature PID, Temperature Linear, or Temperature Curve. They share the auto_control_fan1—auto_control_fan4 switches and would fight over the fan outputs.

Works with Stall Guard

This module cooperates with Stall Guard via the safety floor mechanism. If a fan stalls, Stall Guard sets a minimum speed that Dual Curve respects during recovery. No extra configuration needed, just include both modules.

Configuration

Variable	Default	Description
friendly_name	"Fancontroller"	Device name prefix for the output sensor
curveA_temp1	"20.0"	Curve A temperature point 1 (C)
curveA_speed1	"0.0"	Curve A fan speed at point 1 (%)
curveA_temp2	"22.0"	Curve A temperature point 2 (C)
curveA_speed2	"30.0"	Curve A fan speed at point 2 (%)
curveA_temp3	"28.0"	Curve A temperature point 3 (C)
curveA_speed3	"60.0"	Curve A fan speed at point 3 (%)
curveA_temp4	"35.0"	Curve A temperature point 4 (C)
curveA_speed4	"85.0"	Curve A fan speed at point 4 (%)
curveA_temp5	"40.0"	Curve A temperature point 5 (C)
curveA_speed5	"100.0"	Curve A fan speed at point 5 (%)
curveB_temp1	"25.0"	Curve B temperature point 1 (C)
curveB_speed1	"0.0"	Curve B fan speed at point 1 (%)
curveB_temp2	"35.0"	Curve B temperature point 2 (C)
curveB_speed2	"25.0"	Curve B fan speed at point 2 (%)
curveB_temp3	"45.0"	Curve B temperature point 3 (C)
curveB_speed3	"50.0"	Curve B fan speed at point 3 (%)
curveB_temp4	"50.0"	Curve B temperature point 4 (C)
curveB_speed4	"65.0"	Curve B fan speed at point 4 (%)
curveB_temp5	"55.0"	Curve B temperature point 5 (C)
curveB_speed5	"80.0"	Curve B fan speed at point 5 (%)

How It Works

Every 10 seconds the module reads the board temperature, picks the active curve based on the Curve Selection switch (off = A, on = B), sorts that curve’s five points by temperature, and linearly interpolates the fan speed. Below the lowest point it holds the first speed; above the highest point it holds the last speed.

The result drives all four fans, gated per fan by the Auto Control Fan 1—Fan 4 switches and by any active user override, and clamped by each fan’s safety floor (the floor only applies to non-zero speeds; a commanded 0% always turns the fan off).

Entities

Entity	Type	Purpose
Curve Selection	switch	Selects curve A (off) or B (on). Remembers its last state across reboots.
Curve A/B Temperature 1—5, Speed 1—5	number (20)	The two curves’ points, editable live
Auto Control Fan 1—4	switch (4)	Per-fan enable for automatic control
$friendly_name Curve Output	sensor	The active curve’s computed fan speed (%)
Curve Configuration Warning	binary_sensor	Flags a non-monotonic curve at boot

Switching Automatically

Pair the Curve Selection switch with a Home Assistant automation. For example, switch to the defensive curve when an air-quality sensor reports poor air:

automation:
  - alias: "Defensive fan curve on poor air quality"
    trigger:
      - platform: numeric_state
        entity_id: sensor.living_room_pm2_5
        above: 35
    action:
      - service: switch.turn_on
        target: { entity_id: switch.my_fancontroller_curve_selection }

See examples/with-dual-curve-rev-3.1.yaml for a complete configuration.