A talking front gate: Sonoff door sensor → Alexa, and why it whispers at dawn

Small, satisfying automation: when the main gate opens, an Amazon Echo announces “Door open.” Battery door sensor, no wiring, done in an evening. But two details make it pleasant to live with rather than annoying.

The hardware#

A Sonoff DW2-Wi-Fi door/window sensor — battery powered, talks to the eWeLink cloud. In Home Assistant I pull it in via the excellent SonoffLAN integration, which gives me a clean binary_sensor that’s on when the gate is open.

One honest caveat: the DW2 is a sleeping cloud sensor. It only phones home on a state change, and Sonoff throttles real-time updates. So there’s sometimes a second or two of lag. For a door announcement that’s fine; for anything safety-critical you’d want a wired or Zigbee sensor.

Detail 1: it whispers early in the morning#

A full-volume “DOOR OPEN” at 6am when someone leaves for a walk is a great way to wake the whole house. So the announcement uses Alexa’s SSML whisper effect between 6–9am, and normal voice otherwise:

yaml

message: >-
  {% set h = now().hour %}
  {% if h >= 6 and h < 9 %}
    <speak><amazon:effect name="whispered">Door open</amazon:effect></speak>
  {% else %}
    Door open
  {% endif %}

Little touches like this are the difference between an automation you keep and one you disable after a week.

Detail 2: only fire on a real open#

The trigger is specifically the off → on edge (closed → open), not just “state is on”:

yaml

triggers:
- platform: state
  entity_id: binary_sensor.main_gate_door
  from: 'off'
  to: 'on'

Why the explicit from/to? Because on a Home Assistant restart, a sensor can briefly report unavailable and then on — which a naive “to: on” trigger treats as an event, announcing “door open” every time HA reboots. Pinning from: 'off' means it only fires on a genuine closed→open transition.

Takeaway#

The gadget is trivial. The polish — whisper hours, restart-proof triggering — is what makes it something the household actually likes instead of tolerates. That’s the recurring theme across all my home-automation projects: the last 20% of thoughtfulness is 80% of whether people keep it on.