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Review Smart Switch Sonoff 4CH Pro R2 as an irrigation control unit with smartphone and Alexa

Recensione Smart Switch Sonoff 4CH Pro R2 come centralina di irrigazione con smartphone e Alexa

If there is a tool to automate any type of device that is enjoying success among DIY and electronics enthusiasts, surely the Sonoff 4CH Pro R2 Wi-Fi and RF multiswitch available in many online electronics stores and that finds dozens of different applications.

We have ventured into one of the most interesting ones pending the arrival of the summer season: that of creating a programmable irrigation control unit to be managed both manually and with our iOS or Android smart phone and with voice commands (for now by Alexa) .

The old concept automatic control units are certainly comfortable but programming is always an ordeal and if you do not have automatisms based on the weather conditions or the humidity of the ground, it is always very boring to have to change the settings. So very often you have to manually operate the valves of the system again to manage irrigation even on the days when the water is not supplied by the local administration.

As we will see the programming or re-programming from the smartphone quite simple and in some cases just check the days of the week. Or you can use "semi-manual" routines with rotation through Alexa.

Sonoff 4CH Pro R2: let's take a closer look

By connecting them to the dry contacts located on the bottom, the smart Switch manages up to 4 devices in 3 modes

– independently Self Locking the devices activate or switch off independently of each other:you can use the physical buttons individually to activate or deactivate the connected device

Interlocking or autobloccante: when you switch on one device, all the others switch off. This is surely the most comfortable mode for irrigation because, especially in times of water scarcity, it manages to maintain a constant flow and good power.

The mode inching dedicated to impulse systems (garage opening, gates etc) with an impulse with a programmable duration from 1 to 16 seconds. Each switch can have its own different timer.

Review Smart Switch Sonoff 4CH Pro R2 as an irrigation control unit with smartphone and AlexaThe door that protects the wiring that comes out of the terminals

In addition to this we could have both an on-off direct ignition on the device and in Wireless mode with Wi-Fi (typically from your smartphone or with tools such as Alexa, Google Assistant and IFTTT) or in radio frequency with a 433 MHz RF remote control

You can also program 8 hourly timers, independent of the presence or absence of the wi-fi network and using the internal memory of the smart switch to regulate the system on and off.

The ability to interface with Alexa, Google and IFTTT comes from the application eWelink (for iOS and Android) that allows you to connect the Sonoff to a server and from here manage it with voice commands also in Italian: we will be able to ask Alexa Activate Irrigation 1 scene and start the hydrant or drip of the chosen area.

Let's create an irrigation control unit

Since Sonoff 4CH Pro R2 is powered by 24 Volt we need, in addition to the Sonoff itself:

In our case, we started from a wired system: an excellent 4-zone Orbit control unit that, like many analog devices, is very versatile but has a little difficulty in being programmed and we cannot control it remotely. The valves were already assembled and connected to the control unit as shown in the photo below: the neutral arrived at one end and the 4 wires of each single pump arrived at only one connector.

We connect and configure Sonoff 4CH Pro R2


Depending on the use we want to make of it, we will have to follow a wiring diagram (in the images you can see the connection of the 4 irrigation pumps with the common neutral).

In our case we have bridged the neutral for the 4 connectors and connected the 4 different pumps to the four different switches and connected the power supply and thermal magnetic circuit breaker.

Direct activation

From here we can act directly on the 4 channels: activating one will turn off all the others. Or we can manage the 4 irrigation channels with a radio frequency remote control. (see below)

Pair the remote control in Radio Frequency

Review Smart Switch Sonoff 4CH Pro R2 as an irrigation control unit with smartphone and AlexaThe possibility of controlling the 4-channel Sonoff directly, via Wi-Fi or with a timer is combined with the availability of a remote control at very low costs that you can use as a gate opener or as in this case to manually manage the activation of one or more valves ( always alternate since we have set the 4Channels in this mode).

We recommend in any case to buy the remote control sold in combination as some compatible remote controls have had problems in the past.

So here's how RF Remote pairs with the 4-channel Sonoff: each channel supports 1 button on the remote control and therefore each channel remembers the RadioFrequency button paired last with this mode: quickly press – twice – one of the switches from 1 to 4 and then press one of the ABCD buttons on the remote control.

If pairing is successful, the button will light up red and the corresponding status LED will flash green 4 times. At this point you can press the button to turn the corresponding channel on or off.

The fifth button is used to cancel the RF coding. Press it and keep it pressed until the 4 LEDs of the other buttons light up green and then go off.

Pair remote control over Wi-Fi

Surely this is the ideal option for those who want to manage the irrigation control unit in domotoca mode.

Once the Sonoff is powered, we hold one of the 4 switches corresponding to the channels for 7 seconds, waiting for the green LED to flash.

On the eWelink application that you have downloaded from the App Store or PlayStore press (+) to add the new device and continue by entering the password of your Wi-Fi, continue and wait about three minutes to register and find your Sonoff: at the end you will have the Wi-Fi LED lights up in fixed mode.

Now that we are connected we can move on to distance management or programming.

Let's see the screenshots below

The Wi-Fi synchronization more or less immediate and, using the European server in the trial week we had no problems with disconnection. Thanks to the possibility of having up to 8 memorized timers, we can choose the most suitable day of the week and the duration of delivery of each sprinkler. But we may also need to irrigate only one area of ​​the garden or increase the amount of water by increasing the duration: in this we can increase the days of action.

Command the sprinkler verbally with Alexa

It is quite simple: as you can see from the screens in the gallery above, just add the eWelink skill which works with the Italian version of Alexa.

Once we have looked for new devices as home automation components, we can rename the four channels with the name of the sprinklers to recall them individually. It is possible to create a complex routine with a complete cycle and with a delay (or more delays between one sprinkler and another to have different cycle lengths) between the activation time and the stop time to rotate the 4 sprinklers automatically .


If you get by with the connections or better yet if you have a valid electrician you can set up your smart irrigation control unit in less than an hour (if you already had valves mounted and wired). The management software is not the latest in terms of graphical interface but does its duty in function of a device with a very high versatility and numerous control modes.

Retail price

Smart Switch Sonoff 4CH Pro R2 is located at around 27 Euros on Ebay while remote control in RF costs around 6 Euros.