I have a lightbulb connected to a remote.
I also have a Hue Light Strip not connected to any remote.
I would like the light strip to copy the state of the lightbulb, whenever the state changes.
Typically on/off/brightness.
I am pretty blank on where to start with this, would greatly appreciate if anyone could help me out.
You would need to create an automation that triggers on state change of the bulb.
Then the action would need to be templates like.
{{ state_attr('light.bulb', 'brightness') }}
Easy button would be to make a group with HA helpers (assuming they are both “light” entities)
After you make said group, you can just control the fake/helper entity and both devices will respond with the same states / brightness etc
I did this with my hallway lights. I have 3 lights and for whatever reason, 1 switch turns on 2 of them and the other switch turns on the 3rd on by itself… soo i combined those switches in a group and they now mirror eachother. I also did this with my undercabinet lights (3 seperate entities now as one)
Not sure this is a nodered answer (as thats the tag on the post) but if it helps here is a script I use to copy one bulb to another with various colour and brightness changes (to create different lighting effects), I use it to copy my hue ceiling bulb settings (when they change state, hue or brightness) to two tp_link lamps in the room corners - so similar problem.
alias: Copy Bulb
sequence:
- variables:
src_state: "{{ states(from) }}"
- if:
- condition: template
value_template: "{{ src_state == 'off' }}"
then:
- service: light.turn_off
data: {}
target:
entity_id: "{{ to }}"
else:
- variables:
src_hs: "{{ state_attr(from, 'hs_color') }}"
src_br: "{{ state_attr(from, 'brightness') }}"
h_mode: "{{ hue_mode if hue_mode is defined else \"none\" }}"
s_mode: "{{ sat_mode if sat_mode is defined else \"none\" }}"
b_mode: "{{ brightness_mode if brightness_mode is defined else \"none\" }}"
rl: "{{ range_low if range_low is defined else \"30\" }}"
rh: "{{ range_high if range_high is defined else \"60\" }}"
dst_br: >-
{%- macro b_random_dimmer(c,l,h) -%} {{- (c * ((range(l,h) | random)
/ 100)) | round(3) | float -}} {%- endmacro -%} {%- macro
b_random_brighter(c,l,h) -%} {{- (c + ((255 - c) * ((range(l,h) |
random) / 100))) | round(3) -}} {%- endmacro -%} {%- if b_mode ==
"brighter" -%}
{{- b_random_brighter(src_br, rl, rh) -}}
{%- elif b_mode == "dimmer" -%}
{{- b_random_dimmer(src_br, rl, rh) -}}
{%- else -%}
{{- src_br -}}
{%- endif -%}
dst_h: >-
{%- macro h_complementary(c) -%} {{- ((c + 180) % 360) | round(3)
-}} {%- endmacro -%} {%- macro h_random_analogous(c) -%} {{- ((c +
([-30, 30] | random)) % 360) | round(3) -}} {%- endmacro -%} {%-
macro h_random_triadic(c) -%} {{- ((c + 120 * ([1, 2] | random)) %
360) | round(3) -}} {%- endmacro -%} {%- macro h_random_tetradic(c)
-%} {{- ((c + 90 * ([1, 2, 3] | random)) % 360) | round(3) -}} {%-
endmacro -%} {%- if h_mode == "complementary" -%}
{{- h_complementary(src_hs[0])|float -}}
{%- elif h_mode == "analogous" -%}
{{- h_random_analogous(src_hs[0])|float -}}
{%- elif h_mode == "triadic" -%}
{{- h_random_triadic(src_hs[0])|float -}}
{%- elif h_mode == "tetradic" -%}
{{- h_random_tetradic(src_hs[0])|float -}}
{%- else -%}
{{- src_hs[0] -}}
{%- endif -%}
dst_s: >-
{%- macro s_random_desat(c,l,h) -%} {{- (c * ((range(l,h) | random)
/ 100)) | round(3) | float -}} {%- endmacro -%} {%- macro
s_random_resat(c,l,h) -%} {{- (c + ((100 - c) * ((range(l,h) |
random) / 100))) | round(3) -}} {%- endmacro -%} {%- if s_mode ==
"desaturate" -%}
{{- s_random_desat(src_hs[1],rl,rh)|float -}}
{%- elif s_mode == "resaturate" -%}
{{- s_random_resat(src_hs[1],rl,rh)|float -}}
{%- else -%}
{{- src_hs[1] -}}
{%- endif -%}
- service: light.turn_on
data:
hs_color: ({{ dst_h }}, {{ dst_s }})
brightness: "{{ dst_br }}"
target:
entity_id: "{{ to }}"
mode: parallel
icon: mdi:lightbulb-multiple
max: 30
You can call it like this - this call copies the colour and increases the colour saturation by a random amount (30-60% by default):
- service: script.copy_bulb
data:
from: light.fhl2
to: light.fhlp1
sat_mode: resaturate
or desaturate and make it dimmer:
- service: script.copy_bulb
data:
from: light.fhr1
to: light.fhlp2
sat_mode: desaturate
brightness_mode: dimmer
The script takes the following options, miss any out to just copy from one bulb to another without change:
sat_mode: desaturate or saturate
brightness_mode: brighter or dimmer
hue_mode: complementary, analogous, triadic, or tetradic
range_low: 0-100 (defaults to 30) - lower bound of randomness applied
range_high: 0-100 (defaults to 60) - upper bound of randomness applied
To copy my hue ceiling lights (light.fhl2 and light.fhr1) settings to the tp_link lamps (light.fhlp1 and light.fhlp2) in the same room I use this automation (copies the ceiling bulb to the nearest lamp but marginally more saturated so the room looks better 
):
alias: Hall Copy to Lamps
description: Copy lighting triggered by attribute change of corner ceiling bulbs to corner lamps
trigger:
- platform: state
entity_id:
- light.fhl2
- light.fhr1
attribute: hs_color
- platform: state
entity_id:
- light.fhl2
- light.fhr1
attribute: brightness
condition: []
action:
- parallel:
- service: script.copy_bulb
data:
from: light.fhl2
to: light.fhlp1
sat_mode: resaturate
- service: script.copy_bulb
data:
from: light.fhr1
to: light.fhlp2
sat_mode: resaturate
mode: restart