Dim to Warm –
Emulates the behavior of incandescent bulbs where dimming produces a warmer glow. Works with any smart light that has adjustable color temperature.
What it does
When you dim a light down, the color temperature automatically shifts warmer (lower Kelvin). When you turn it up, it shifts cooler. This mimics how traditional incandescent and halogen bulbs naturally behave.
Features:
- Select multiple lights in a single automation – only the light that changed gets updated
- Configurable Kelvin range (e.g. only use 2500–3500K even if the bulb supports 2200–5000K)
- Brightness zones: define flat regions at the top and bottom where Kelvin stays constant
- Linear interpolation in the transition zone between
- Loop prevention with 25K deadband
- Optional apply-on-turn-on
- Uses
color_temp_kelvin(future-proof, no deprecated mireds)
How the zones work
Brightness % Color Temperature
0% ─┐
│ Lower zone → Min Kelvin (constant, warm)
10% ─┘
│ Transition zone → Linear interpolation
90% ─┐
│ Upper zone → Max Kelvin (constant, cool)
100% ─┘
Example with defaults (min=2500K, max=4000K, lower=10%, upper=90%):
- 0–10% brightness → 2500 K (warm, constant)
- 10–90% brightness → 2500–4000 K (smooth transition)
- 90–100% brightness → 4000 K (cool, constant)
Requirements
- Home Assistant 2024.6.0 or later
- Lights with adjustable color temperature
Blueprint code
blueprint:
name: "Dim to Warm"
description: >
Automatically links brightness to color temperature – the lower the
brightness, the warmer (lower Kelvin) the light, and vice versa.
Select one or more lights. All lights share the same Kelvin range
and brightness zone settings. When a light's brightness changes,
only that specific light's color temperature is updated.
Configure:
• Min Kelvin (warmest) and Max Kelvin (coolest)
• Lower zone – below this brightness % min Kelvin is held constant
• Upper zone – above this brightness % max Kelvin is held constant
• In between, color temperature is interpolated linearly
Example with defaults (min=2500K, max=4000K, lower=10%, upper=90%):
0–10 % brightness → 2500 K (warm, constant)
10–90 % brightness → 2500–4000 K (linear transition)
90–100 % brightness → 4000 K (cool, constant)
domain: automation
author: "robblids"
source_url: "https://github.com/robblids/ha-dim-to-warm/blob/main/dim_to_warm.yaml"
homeassistant:
min_version: "2024.6.0"
input:
# ── Lights ───────────────────────────────────────────────
light_section:
name: "Lights"
icon: mdi:lightbulb-group
description: "Select lights and configure the Kelvin range."
collapsed: false
input:
target_lights:
name: "Lights"
description: >
Select one or more lights to apply dim-to-warm to.
All selected lights will share the same settings.
selector:
entity:
domain: light
multiple: true
min_kelvin:
name: "Min Kelvin (warmest)"
description: >
Lowest color temperature. Used when brightness
is at or below the lower zone.
default: 2500
selector:
color_temp:
unit: kelvin
min: 1800
max: 6500
max_kelvin:
name: "Max Kelvin (coolest)"
description: >
Highest color temperature. Used when brightness
is at or above the upper zone.
default: 4000
selector:
color_temp:
unit: kelvin
min: 1800
max: 6500
# ── Zones ────────────────────────────────────────────────
zone_section:
name: "Brightness zones"
icon: mdi:chart-bell-curve-cumulative
description: >
Define the brightness ranges where color temperature
is held constant (lower/upper zone) or interpolated.
collapsed: false
input:
lower_zone:
name: "Lower zone (%)"
description: >
Below this brightness percentage, min Kelvin is always used.
The transition zone starts at this value.
default: 10
selector:
number:
min: 0
max: 99
step: 1
unit_of_measurement: "%"
mode: slider
upper_zone:
name: "Upper zone (%)"
description: >
Above this brightness percentage, max Kelvin is always used.
The transition zone ends at this value.
default: 90
selector:
number:
min: 1
max: 100
step: 1
unit_of_measurement: "%"
mode: slider
# ── Behavior ─────────────────────────────────────────────
behavior_section:
name: "Behavior"
icon: mdi:cog
description: "Additional settings for the automation."
collapsed: true
input:
transition_time:
name: "Transition time"
description: >
Time in seconds for the color temperature change.
Set to 0 for instant changes.
default: 0.5
selector:
number:
min: 0
max: 10
step: 0.5
unit_of_measurement: "s"
mode: slider
apply_on_turn_on:
name: "Apply on turn on"
description: >
Also apply dim-to-warm immediately when a light
is turned on (not only on brightness changes).
default: true
selector:
boolean: {}
# ═══════════════════════════════════════════════════════════════
# Variables
# ═══════════════════════════════════════════════════════════════
variables:
all_lights: !input target_lights
v_min_kelvin: !input min_kelvin
v_max_kelvin: !input max_kelvin
v_lower_zone: !input lower_zone
v_upper_zone: !input upper_zone
v_transition: !input transition_time
apply_on_turn_on: !input apply_on_turn_on
# The entity that triggered the automation
changed_light: "{{ trigger.entity_id }}"
# Calculate target Kelvin based on the triggering light's brightness
target_kelvin: >
{% set br = state_attr(changed_light, 'brightness') | default(0) | float(0) %}
{% set pct = (br / 255 * 100) | round(1) %}
{% set min_k = v_min_kelvin | float(2500) %}
{% set max_k = v_max_kelvin | float(4000) %}
{% set lower = v_lower_zone | float(10) %}
{% set upper = v_upper_zone | float(90) %}
{% if lower >= upper %}
{{ ((min_k + max_k) / 2) | round(0) }}
{% elif pct <= lower %}
{{ min_k | round(0) }}
{% elif pct >= upper %}
{{ max_k | round(0) }}
{% else %}
{% set ratio = (pct - lower) / (upper - lower) %}
{{ (min_k + ratio * (max_k - min_k)) | round(0) }}
{% endif %}
# Current Kelvin on the light – to avoid unnecessary calls
current_kelvin: >
{{ state_attr(changed_light, 'color_temp_kelvin') | default(0) | float(0) }}
# Only update if difference > 25K (prevents loops)
should_update: >
{{ (target_kelvin | float(0) - current_kelvin | float(0)) | abs > 25 }}
# ═══════════════════════════════════════════════════════════════
# Triggers
# ═══════════════════════════════════════════════════════════════
triggers:
# Brightness changed on any of the selected lights
- trigger: state
entity_id: !input target_lights
attribute: brightness
id: "brightness_changed"
# Any of the selected lights turned on
- trigger: state
entity_id: !input target_lights
to: "on"
id: "light_turned_on"
# ═══════════════════════════════════════════════════════════════
# Conditions
# ═══════════════════════════════════════════════════════════════
conditions:
# The triggering light must be on
- condition: template
value_template: "{{ is_state(changed_light, 'on') }}"
# Check if we should apply on turn-on events
- condition: or
conditions:
- condition: trigger
id: "brightness_changed"
- condition: and
conditions:
- condition: trigger
id: "light_turned_on"
- condition: template
value_template: "{{ apply_on_turn_on }}"
# ═══════════════════════════════════════════════════════════════
# Actions
# ═══════════════════════════════════════════════════════════════
mode: queued
max: 10
actions:
# Short delay to let brightness stabilize
- delay:
milliseconds: 150
# Only proceed if an update is actually needed
- condition: template
value_template: "{{ should_update }}"
# Set color temperature on the specific light that changed
- action: light.turn_on
target:
entity_id: "{{ changed_light }}"
data:
color_temp_kelvin: "{{ target_kelvin | int }}"
transition: "{{ v_transition | float(0.5) }}"