Linked Sync Group for Samotech SM-Series Dimmers and Switches

Most UK homes built before the year 2000 don’t have the traveler wire required for hardware 2-way (or 3-way) switching. Retrofitting that wire usually means lifting floors, chasing walls, or pulling cables through ceilings – fine if you’re already renovating, prohibitively disruptive otherwise.

This Home Assistant blueprint solves the problem in software. Pair two or more Samotech SM-series Zigbee devices into a synced group, and a press, toggle or dim at any one of them carries across to the others. The wall switches at both ends of a hallway, or top and bottom of a staircase, become indistinguishable from a true hardware 2-way circuit.

What it does

• Mirrors on/off state across every device in the group
• Mirrors brightness between dimmer-capable devices (SM323, SM325-ZG, SM309-S)
• Skips brightness on switch-only devices (SM308-S) so they just track on/off
• Configurable transition time keeps the mirroring smooth
• Loop prevention via Home Assistant context tracking – the sync only fires from user interaction, never from itself

Tested combinations

• SM323 wall dimmer + SM325-ZG wall dimmer (full brightness sync)
• SM323 + SM325-ZG + SM308-S in a single three-device group (state and brightness across the dimmers, state-only on the switch module)
• Mixed dimmer/switch groups with up to five devices

End-to-end testing was carried out in a live Home Assistant instance with the SM-series integrated via ZHA. All four interaction paths – wall press at each device and HA UI toggle – behave as expected with no perceptible delay or flicker.

Use cases this is built for

• Hallways and landings with switch positions at either end
• Staircases – top and bottom of the stairs
• Open-plan kitchen / diner / living rooms where a single coordinated lighting level should track across multiple circuits
• Annexes, extensions and garage workshops added without re-cabling
• Master bedrooms with switches both at the door and bedside, where no traveler wire exists

Compatible with smart bulbs and mixed device groups

The Linked Sync Group blueprint isn’t restricted to Samotech devices – any Zigbee or Wi-Fi light entity in Home Assistant can be added to the same group. This makes it the ideal blueprint for the “wall control of smart bulbs” use case where one SM323 wall position should control multiple bulbs simultaneously, also known as decoupled mode or smart bulb mode on other brands.

Typical configuration:

• One SM323 wired with L+N only, no load – acts as the wall input. Installed at any wall switch position in the house.
• Two to four smart bulbs (Philips Hue, IKEA Tradfri, Innr, Aqara, generic Zigbee, or any Wi-Fi bulb exposed as a light entity) – the controlled outputs, typically a room’s worth of lighting
• All entities go into the same Linked Sync Group instance

Wall presses and rotations on the SM323 propagate to all the bulbs simultaneously. App or voice commands on any bulb propagate back to update the SM323’s tracked state, so the wall position always stays in sync with reality.

This is the practical equivalent of decoupled mode / smart bulb mode on Aqara H1 wall switches or Inovelli Red/Blue dimmers, achieved with UK-engineered Samotech hardware (no-neutral, trailing-edge MOSFET, BS 7671:2018 aligned, 35 mm UK back-box fit) and free open-source Home Assistant automation.

For a 1:1 wall-to-bulb mapping with exactly one bulb, the Direct Mirror Pair blueprint is the cleaner choice. Use the Linked Sync Group when you have multiple bulbs in one room, multiple SM323 wall positions, or you want to mix smart bulbs with conventional Samotech dimmers in the same group.

What mirrors and what doesn’t:

• On/off state – mirrors across the entire group
• Brightness (0–255) – mirrors across dimmer-capable entities in the group
• Colour (RGB) and colour temperature (CCT) – not mirrored. Bulbs keep their last colour. Set colour via HA scenes or automations.

How to install

1. In Home Assistant: Settings → Automations & Scenes → Blueprints → Import Blueprint
2. Paste this URL: https://raw.githubusercontent.com/samotech-ltd/home-assistant-blueprints/main/samotech-sm-series-linked-sync.yaml
3. Click Preview Blueprint then Import Blueprint
4. Create a new automation from the blueprint
5. Add the Samotech lights you want to sync (two to five devices, any mix of dimmer and switch)
6. Choose whether to mirror brightness (default on)
7. Set the transition time (0.5 seconds is a good default)
8. Save and enable the automation

Compatible Samotech devices

• SM323 Zigbee Rotary Dimmer – wall, no neutral, dimmable
• SM325-ZG Zigbee Dimmer – wall, dimmable (new for 2026)
• SM308-S Zigbee Switch Module – inline, on/off
• SM309-S Zigbee Dimmer Module – inline, no neutral, dimmable

Any combination of the above works in the same sync group. The blueprint handles mixed dimmer/switch hardware automatically.

Technical notes

Integration: Built and tested against ZHA (Zigbee Home Automation). A Zigbee2MQTT-specific variant may follow if there’s demand.

Loop prevention: The blueprint only reacts to user-initiated changes – pushes at the wall, rotations of the dimmer knob, and direct toggles in the HA UI or via voice. Automation-driven changes elsewhere in your HA configuration do not trigger the sync. This is by design, to prevent feedback loops.

Concurrency: Parallel mode with a max of five runs, so simultaneous changes across multiple devices in the group don’t deadlock.

Download: The raw blueprint YAML is hosted at github.com/samotech-ltd/home-assistant-blueprints.