How to Set Up Your Sonoff S40 Smart Plug

Beginner 5-10 minutes

What You'll Need

  • Sonoff S40 Smart Plug
  • eWeLink app (iOS or Android)
  • eWeLink account
  • 2.4GHz Wi-Fi network

Step-by-Step Setup

  1. Download the eWeLink app and create an account or sign in.
  2. Plug in the Sonoff S40. The LED will light up to confirm it has power.
  3. Enter pairing mode by pressing and holding the button until the LED starts blinking. A 5-second hold puts it in Quick Pairing mode.
  4. Add the device in eWeLink:
    • Tap "+" and follow the pairing wizard
    • Select "Quick Pairing" for the fastest setup, or "Compatible Pairing" (AP mode) if Quick Pairing does not work
  5. Connect to Wi-Fi by entering your 2.4GHz credentials and waiting for the pairing to complete.
  6. Name the plug and organize it into a room.

Key Features

  • Wi-Fi smart plug with compact design
  • 15A capacity for most household appliances
  • Alexa and Google Home compatible
  • eWeLink app for control, scheduling, and automations
  • Countdown timers and repeating schedules
  • LAN mode for local control without internet

LAN Mode and Local Control

One standout feature of Sonoff devices is LAN mode. When enabled, the plug can be controlled from the eWeLink app over your local network without needing internet access:

  • Enable LAN mode in the eWeLink app's device settings.
  • When your internet goes down, the plug still responds to commands from the eWeLink app as long as your phone and the plug are on the same Wi-Fi network.
  • Schedules set on the device continue to run even without internet, since they are stored locally on the plug.
  • LAN mode also reduces latency since commands do not route through the cloud.

eWeLink Scenes and Automations

The eWeLink app supports basic automations and scenes:

  • Scenes: Create one-tap scenes that control multiple eWeLink devices at once.
  • Automations: Set up triggers based on time, device state, or other eWeLink devices. For example, turn on a fan when a Sonoff temperature sensor reads above a certain threshold.
  • Inter-device control: If you have multiple Sonoff products, they can trigger each other through the eWeLink app.

Practical Use Cases

  • Reliable appliance timer: Use the built-in scheduling for devices that need to run on a predictable pattern, like aquarium lights or a dehumidifier.
  • Sonoff ecosystem: Pair with Sonoff sensors and other Sonoff plugs for a coordinated smart home setup managed entirely through eWeLink.
  • Backup local control: The LAN mode makes this a solid choice for situations where internet reliability is a concern, like vacation homes or workshops.

Troubleshooting

  • Quick Pairing vs. Compatible Pairing: Quick Pairing (5-second hold) is faster but does not work on all routers. If it fails, try Compatible Pairing (press the button 3 times quickly) which creates a Wi-Fi hotspot you connect to directly.
  • Wi-Fi band: 2.4GHz only. If your router auto-steers devices to 5GHz, you may need to temporarily separate the bands or use AP mode pairing.
  • LAN control not working: Make sure LAN mode is enabled in the device settings within the eWeLink app. Both your phone and the plug must be on the same local network.
  • Factory reset: Press and hold the button for about 10 seconds until the LED flashes rapidly in a reset pattern. This clears all settings.
  • Firmware updates: Check the eWeLink app periodically for firmware updates. These can improve Wi-Fi stability, add features, and fix bugs.

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