Fernwood Tech
Shelly Plus Add-On
Shelly Plus Add-On
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Verified / from Shelly specs: The Shelly Plus Add-On is a galvanically isolated sensor interface for compatible Shelly Plus, Gen3, and Gen4 devices. It allows you to connect temperature, humidity, analog, and digital sensors to expand your Shelly relay or controller into a more capable automation device.
Use it for projects such as hot water cylinder temperature monitoring, fridge/freezer alerts, soil moisture sensing, motion-triggered lighting, liquid level detection, garage door position monitoring, or other smart home and light commercial automation tasks.
It connects directly to supported Shelly devices and adds extra sensor inputs without needing a separate hub. Sensor data can then be used in the Shelly app, local web interface, Home Assistant, MQTT, or other compatible automation platforms, depending on your setup.
Key Features
| Feature | Details |
|---|---|
| Sensor expansion | Adds 1-Wire, analog, and digital sensor support |
| Isolation | Galvanically isolated interface for safer, more reliable sensing |
| Temperature sensing | Supports up to 5 × DS18B20 temperature sensors |
| Humidity sensing | Supports 1 × DHT22 temperature/humidity sensor |
| Analog input | Supports 0–10 V analog sensors |
| Digital input | Suitable for switches, reed sensors, PIR sensors, and similar devices |
| Power source | Powered from the connected Shelly device |
| Automation ready | Use sensor readings to trigger scenes, alerts, relays, or Home Assistant automations |
Supported Sensor Types
| Sensor type | Example use |
|---|---|
| DS18B20 temperature probes | Hot water cylinder, fridge/freezer, aquarium, room temperature |
| DHT22 | Temperature and humidity monitoring |
| NTC 10 kΩ thermistors | Temperature measurement |
| PIR motion sensors | Motion-triggered lighting or occupancy detection |
| Reed/contact sensors | Garage door or gate open/closed status |
| Photoresistors/LDR | Light level sensing |
| Soil moisture sensors | Smart irrigation |
| Ultrasonic sensors | Distance or level measurement |
| Capacitive liquid level sensors | Tank or water level detection |
| 0–10 V analog sensors | General analog monitoring |
Compatibility
Verified / from Shelly specs: Compatible device families include selected Shelly Plus, Gen3, and Gen4 devices. The product page lists examples such as Shelly Plus 1, Plus 1PM, Plus 2PM, Plus i4/i4DC, Plus RGBW PM, Shelly 1 Gen3, 1PM Gen3, 2PM Gen3, Shelly EM Gen3, and selected Gen4 devices.
| Compatible range | Examples |
|---|---|
| Shelly Plus | Plus 1, Plus 1PM, Plus 2PM, Plus i4/i4DC |
| Shelly Gen3 | 1 Gen3, 1PM Gen3, 2PM Gen3, i4 Gen3, EM Gen3 |
| Shelly Gen4 | 1 Gen4, 1PM Gen4, 2PM Gen4 |
Technical Specifications
| Specification | Value |
|---|---|
| Dimensions | 37 × 42 × 15 mm |
| Power supply | 3.3 V DC from Shelly device |
| Power consumption | < 0.5 W without sensors |
| 1-Wire support | Up to 5 × DS18B20 or 1 × DHT22 |
| Analog input | 0–10 V |
| Voltmeter threshold | 0.1 V configurable |
| Analog report threshold | 1% configurable |
| Analog/voltmeter accuracy | Better than ±5% |
| Operating temperature | -20°C to 40°C |
| Humidity range | 30% to 70% RH |
| Max conductor size | 1 mm² / 17 AWG |
Typical Uses
| Use case | How the Add-On helps |
|---|---|
| Hot water cylinder monitoring | Add temperature probes to track top/bottom cylinder temperature |
| Fridge/freezer alerts | Monitor temperature and trigger warnings if limits are exceeded |
| Smart irrigation | Use soil moisture data to control watering |
| Garage door status | Use a reed switch to show open/closed state |
| Motion lighting | Connect a PIR sensor to trigger lights |
| Tank or water level monitoring | Use liquid level or analog sensors |
| Light-based automation | Use an LDR to automate blinds, lights, or shading |
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