Light Sync Master for Home Assistant

A custom Home Assistant integration that creates a virtual master light to synchronize multiple slave lights in real-time.

Why

Controlling multiple lights individually is tedious. Grouping them in Home Assistant makes them act as one, but you lose per-light control.

Light Sync Master gives you both: change the master and all ON slave lights follow. Turn a slave OFF and it's independent again. Simple.

How It Works

graph LR
    M[Virtual Master Light<br>color · brightness · temperature] -->|sync when ON| S1[Slave Light 1 💡]
    M -->|sync when ON| S2[Slave Light 2 💡]
    M -->|skip when OFF| S3[Slave Light 3 🔌]
    SW[Sync Switch] -->|enable/disable| M

Loading

• Master changes → all ON slave lights update instantly
• Slave turns ON → automatically adopts master state
• Slave is OFF → not affected by master changes
• Sync switch OFF → no propagation, lights keep their state

Features

• Virtual Master Light — always-on entity that stores color, brightness, and temperature
• Real-time Sync — event-driven, no polling
• Sync Switch — enable/disable with one tap
• Auto-sync on Turn On — slave lights match master when turned on
• Persistent State — survives Home Assistant restarts
• Smooth Transitions — configurable 0-10 seconds
• UI Configuration — no YAML required
• Multi-language — English and Italian

Installation

HACS (Recommended)

1. Open HACS → Integrations → ⋮ → Custom repositories
2. Add https://github.com/gabry-ts/ha-light-sync-master (category: Integration)
3. Install Light Sync Master
4. Restart Home Assistant

Manual

1. Copy custom_components/light_sync_master/ to your HA config directory
2. Restart Home Assistant

Setup

1. Settings → Devices & Services → + Add Integration
2. Search for Light Sync Master
3. Name your master light (e.g., "Master Bedroom")
4. Select the slave lights
5. Done — two entities are created:

Entity	Description
light.lsm_<name>	Virtual master light
switch.lsm_<name>	Sync enable/disable switch

Options

Click Configure on the integration card to modify:

• Slave lights — add or remove
• Default sync state — sync ON or OFF after restart
• Immediate sync on enable — sync all ON slaves when switch is turned on
• Transition time — 0-10 seconds for smooth changes
• Debug logging — detailed logs for troubleshooting

Use Cases

• Synchronizing bedroom lamps
• Coordinating living room lighting
• Managing multiple RGB strips as one
• Creating unified scenes across rooms

Example Automation

automation:
  - alias: "Disable sync at bedtime"
    trigger:
      - platform: time
        at: "23:00:00"
    action:
      - service: switch.turn_off
        target:
          entity_id: switch.lsm_master_bedroom

  - alias: "Enable sync in morning"
    trigger:
      - platform: time
        at: "07:00:00"
    action:
      - service: switch.turn_on
        target:
          entity_id: switch.lsm_master_bedroom

Lovelace Card

type: vertical-stack
cards:
  - type: light
    entity: light.lsm_master_bedroom
    name: Master Bedroom Light
  - type: entities
    entities:
      - entity: switch.lsm_master_bedroom
        name: Sync Enabled
  - type: entities
    title: Slave Lights
    entities:
      - light.bedroom_lamp_1
      - light.bedroom_lamp_2
      - light.hallway_spots

Troubleshooting

Problem	Solution
Master doesn't sync slaves	Check sync switch is ON and slaves are turned ON
Slave not in selection list	Verify it's a light entity, restart HA
Sync feels slow	Reduce transition time, check HA performance

Enable debug logging:

logger:
  default: info
  logs:
    custom_components.light_sync_master: debug

Technical Details

• Platform: Home Assistant 2024.1+
• Language: Python 3.11+
• Configuration: UI-based (config_flow)
• State: RestoreEntity for persistence
• Architecture: Event-driven (no polling)
• Color Modes: RGB, HS, XY, Color Temperature

Limitations (v1.0)

• Master light is always ON (by design)
• Light effects are not synchronized
• No bidirectional sync (slave → master)
• No per-slave attribute selection

Contributing

Contributions welcome! Fork, branch, and submit a PR.

License

MIT