Shelly Plus Add-On

The Shelly Plus Add-on is a galvanically isolated sensor interface that extends the capabilities of a compatible Shelly Plus, Gen3 or Gen4 device, allowing additional analogue and digital sensors to be connected without needing a separate module with its own Wi-Fi connection. In practice, it turns an ordinary Shelly relay into a small monitoring centre, able to read temperature, humidity or other physical quantities and trigger automations based on them.

The add-on supports up to five DS18B20 temperature sensors connected on the same 1-Wire bus, a single DHT22 temperature and humidity sensor, as well as a wide range of analogue sensors with 0-10V output: photoresistors, soil moisture sensors, ultrasonic proximity sensors, capacitive liquid level sensors or sound detectors. The digital input can also be used for a reed contact, useful for monitoring the state of a garage door.

It is the right accessory for anyone who wants to go beyond simple on/off switching: measuring the temperature in an aquarium, controlling irrigation only when the soil is dry, or automatically retracting an awning in strong wind all become possible by combining a compatible Shelly relay with this add-on and the right sensor for each application.

Practical use cases

• Extends the functionality of the base Shelly device, allowing additional sensors or modules to be connected without replacing existing equipment.
• Useful for custom automation projects where more inputs or outputs are needed than the standard configuration provides.
• Simplifies expanding an existing smart home system, without the need for a completely new device.
• Recommended for advanced users who want to tailor exactly the functions of each Shelly module in the installation.

Technical specifications

The Shelly Plus Add-on opens the door to automations based on real environmental data, not just simple on/off commands, for any compatible Shelly relay.