HomeHome AutomationMonitor 2 gangs at once with Shelly 2.5

Monitor 2 gangs at once with Shelly 2.5

Shelly 2.5 was the inspiration for Sonoff Dual R3

With a recent release (and the untimely demise caused by my foolishness) of Sonoff DualR (review), it would be irresponsible for me not to mention another product from Shelly team. Clearly, a product that was the inspiration for the previously mentioned compact switch. I’m talking about Shelly 2.5. A device you should really check out if you are in the process of automating lights, garage doors and other fun things.

Shelly 2.5

Until you hold one in your hand, you won’t believe how small this thing is. While Shelly Motion (review) hovers on another side of the size spectrum, Shelly 2.5 is just a little bit bigger than original Shelly 1 (review) device and it brings so much more to the table. Don’t be fooled, Shelly 2.5 isn’t a replacement for any other Shelly devices. It comes with unique and very useful features.

Shelly 2.5 is a connected dual switch that comes with power consumption monitoring available for each channel. It’s designed to work existing wall switches, being hidden behind the wall switch or in the ceiling fitting (depending on the wiring schema available in your location).

Technical specification:

  • input 110-230V ±10% 50/60Hz AC
  • input 24-60V DC
  • max load per channel 10A/230V, 50/60Hz
  • WiFi: WiFi 802.11 b/g/n

The switching output will depend on the input used to power the device. Unlike Shelly 1, this dual-channel relay isn’t decoupled, You won’t be able to take the advantage of “dry contacts” but you gain the power metering capabilities. to increase the safety of operation, Shelly app also comes with a limit on current use. If the power draw exceeds a certain value, Shelly 2.5 will turn off. It won’t protect your device from shorts, but it will manage situations where spikes in current can cause heat damage.

Upclose and personal

Shelly 2.5 tiny. It’s smaller than both Sonoff Mini (review) and Sonoff Mini ZigBee (review) and yet it packs the support for 2 gangs and 2 switches. This comes at the price. It comes with a minimal number of terminals needed to get it to work. If you pay closer attention to the wiring diagram, you will have to split the electrical cable using WAGO connectors to power all inputs correctly. Tighter spaces may have a problem accommodating extra connectors and it was one of my main complains about Shelly 1.

I’m convinced that all my readers are smart, and will take extra care when wiring the device especially when used with mains. The wiring guide shows what to connect where, but please don’t be me and double check everything before flicking the power back on. Manual shows 3 types of installation: AC/DC and motors. In doubt, reach out to a professional.

Inside sealed enclosure sleeps, a familiar to anyone interested in DIY, microcontroller – ESP8266. There are a couple of dev pins exposed (GND, GPIO00, RST, 3.3V, RX, TX) if tinkering is your thing and a physical button. All this is dry information really as the next chapter will defer you from trying to alter the software.

Good online, better offline

The cloud support isn’t exactly anything new, but Shelly Cloud app found an interesting take on how to present data and controls. Of course integration with major players like Alexa and Google Home are present, but the app itself offers unique features.

One of my favourites is the power consumption data displayed by room. While the individual channels of Shelly 2.5 can be monitored, it’s interesting to see aggregated data of all power meters in a single room. It gives you instant feedback on how much electricity your automation is using altogether without the need for napkin math. In case you ever wondered how much do you save by running smart lights and switches, I did all the maths for you in this article about the yearly cost of automation.

Power metrics available via Shelly 2.5 include current power consumption in Watts and the electricity used in Wh. Unfortunately, there are no other metrics available, but with a little bit of math, you can calculate amps and other values based on the information given and the input voltage.

Cloud services (and web interface too) also offer special web requests triggered by switching lights (or motor) on/off. Multiple requests can be made based on a single trigger, but it’s not advisable to make more than 2 calls per trigger. It’s a useful feature if you want to ping your Home Automation server when lights got turned on or command another integration outside of Shelly Cloud.

What’s impressive, is the list of modes that your switch can be set to work at. Shelly Cloud has every option covered! From toggles, through edge pulses to completely decoupled operation. Regardless of the switch on your wall, you will find a perfect way to operate Shelly 2.5.

Lastly, the app comes with usual options: timers and schedules and automation panel to link other Shelly devices together.

Privacy first

If the cloud isn’t your thing, but privacy is, logging into web interface exposes not only a similar interface but enables control over MQTT and REST. If you opt-out for MQTT, Shelly Cloud will be the sacrificial lamb as you can’t use both services together. If you want to retain Google Home and Alexa integrations and use the device in the development mode, pick the REST API. Alternatively, take a look at Alexa and Google Home integrations for NodeRED.

Web interface has most of the features available in the app. You won’t see usage graph or fancy graphics but you won’t feel restricted.

I will cover use of Shelly 2.5 with NodeRED in one of my follow up articles, so if that’s your thing, follow me for updates.

Buy Shelly 2.5

Buy it using these links to support NotEnoughTech.

Final Thoughts

Shelly 2.5 is seriously impressive inside and functions. While personally, I’d like to see terminals on the device being mapped better. I had issues fitting Shelly 1 and all required connectors in my ceiling rose and Sonoff Mini proved that while being slightly bigger in size, having all terminals built-in, can decrease the footprint inside the electrical box. If you want to see how Shelly 2.5 fares against Sonoff DualR3 – I wrote an article about it. I will praise Shelly 2.5 for excellent firmware, great development support which is what DIY enthusiasts look for in various devices to make their home automation truly custom. If you have any questions, feel free to leave it in this Reddit thread.

🆓📈 – See the transparency note for details.


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