#Test: unpacking the SONOFF 4CH PRO, 4 relays operated in WiFi & RF on DIN rail, test with the EWelink app

Table of Contents

Itead, the Chinese manufacturer of SONOFF marketed the SONOFF 4CH Pro, an improved version of 4CH. You are most likely familiar with the power supplies and the connected SONOFF module. In the previous article we saw how to install the ESP Easy firmware to the connected SONOFF S20. Itead proposes a new range more Pro of its products. The Sonoff 4CH Pro is a very economical module (about $22.50 in china) which allows to control 4 relays that can be integrated into an electrical panel on a DIN rail. In this first article, we will discover how to activate the 4CH, the main features proposed by the firmware and to test the mobile application EWelink (for iOS and Android). In the next article we will see how to replace the original firmware. This will allow us to directly integrate 4CH or 4CH Pro to a home automation box.

Technical specifications and operating modes of the Sonoff

4CH Pro

The SONOFF 4CH Pro (and 4CH) is built around an Espressif ESP8285 WiFi module. We therefore remain on familiar ground in the field of DIY home automation. Itead, as usual, left the door open to do-it-yourselfers by placing on the PCB the location to weld a serial connector :-D. Compared to his little brother, the 4CH, the Pro also has a 433MHz receiver. It is possible to control the relays from a remote control (the procedure is explained in paragraph 4 here) and probably from a home automation server using the RFLink gateway (to be tested …).

Each relay can power a device in 220V/10A (max. 2200W). Be careful not to exceed 16A on the total of 4 relays. This should suffice very widely for most home automation applications.

Itead designed the case well. Several operating modes are available, which can be selected with the help of a DIP switch S6 (Work mode switch). To access the various selectors, the housing must be opened.

No fear to open the case. There is no warranty cancellation label.


Summary of technical characteristics. The Pro version is marked in bold

  • Connectivity: WiFi (antenna engraved on the PCB, no external antenna connector), 433 MHz radio receiver with integrated antenna
  • WiFi Module: ESP8266 reprogrammable using a serial connector to be soldered to the free slot on the PCB
  • Relay: 4 relays HUIKE 230V / 10A or 30VDC / 10A. Max. 16A and 2200W per relay. Connection NC (Normally Closed) or NO (Normally Open)
  • Configuration switches
    • K5 and S6 (4-position DIP): operating mode (see below)
    • K6: duration of the relays in the Inching mode (see below)
  • Power supply
    • 5-24VDC
    • 90-250V
  • Voice Assist Compatibility
    • Google Home
    • Nest Thermostat
    • Amazon Alexa
  • Other
    • A red status indication LED for each relay
    • A blue LED status indication of WiFi.
    • Blinks if the case is not connected to the WiFi network. The WiFi configuration is done from the EWelink application
    • Flashes 3 times and starts again during inclusion (press 5 seconds on any command button to start inclusion)
    • On continuously when the module is operating normally
    • A relay control button
    • A button to erase radio codes

Differences between ESP8285 and ESP8266 modules

Both housings are built around an ESP8285 WiFi module. Compared to the ESP8266, the ESP8285 has only 1MB of flash memory (instead of 4MB). The other characteristics are grouped in the table below

Both housings are built around an ESP8285 WiFi module. Compared to the ESP8266, the ESP8285 has only 1MB of flash memory (instead of 4MB). The other characteristics are grouped in the table below

ESP8285 ESP8266
CPU Tensilica L106 32-bit@80MHz…160MHz Tensilica L106 32-bit@80MHz…160MHz
2,412G…2,484GHz 2,412G…2,484GHz
Receiver Sensibility b: -91 dBm, g: -75 dBm, n: -72 dBm b: -91 dBm, g: -75 dBm, n: -72 dBm
Power supply 3…3.6V DC 3…3.6V DC
Mounting SMD SMD
Housing QFN32 QFN32
Network Protocole FTP, HTTP, IPv4, TCP, UDP FTP, HTTP, IPv4, TCP, UDP
Transmitter power, dBm 20dBm 20dBm
Flash memory size 1MB 4MB
Dimensions 5 x 5mm 5 x 5mm
Datasheet ESP8285 ESP8266EX

Differences between SONOFF 4CH and 4CH Pro

Here is a comparison table of the main features of SONOFF 4CH and 4CH Pro.

4CH 4CH Pro
WiFi module ESP8285 ESP8285 + STM32
433MHz receiver Yes
230V/16A relay 4 4 isolated relay
5VDC power supply Yes
90-250V power supply Yes Yes
Technical datasheet Wiki Itead Wiki Itead

How to choose the mode of operation?

The SONOFF 4CH Pro offers 3 modes of operation.

  • Interlock mode : Only one relay can be activated at a time. For example, if R1 is activated, when R2 is activated (manually u from the app), R1 is deactivated and R2 is activated. This is the default mode for unpacking.
Sonoff 4CH pro interlock mode

Source : Itead

  • Self-locking mode: Each relay can be switched on and off independently.


Sonoff 4CH Pro self locking new

Source : Itead

  • Inching mode: Each relay is activated for a duration set by the K6 (delay) selector when activated from the appliance, the control knob or a 433MHz remote control. It is very useful to control the opening of a gate or the electric trigger of a gate.
Sonoff 4CH Inching mode

Source : Itead

The S6 selector switches between Interlock mode (default) and Self-locking / Inching mode.

0 Interlock CH1 – CH4
1 Self-locking/Inching CH1 – CH4

For Self-locking / Inching, it is possible to choose the operating mode for each relay using the K5 selector

Position Status Mode Relay
1 0 Inching CH1
2 0 Inching CH2
3 0 Inching CH3
4 0 Inching CH4
1 1 Self-locking CH1
2 1 Self-locking CH2
3 1 Self-locking CH3
4 1 Self-locking CH4

For example, if only relay 4 is to be able to control an electric trigger (Inching mode), the selector S6 must be set to 2 and then configure the selector K5 as well

Position K5
1 0
2 0
3 0
4 1

The activation time is then configured using the selector K6 according to the following table. The time is indicated in milliseconds. It applies to all relays.

Sonoff 4CH Pro K6 duration

What can you drive with the 4CH Pro?

Itead gives some examples of applications. The most classic is the piloting of lamps of course. The advantage is that you can control an existing installation without having to replace all the bulbs. It is much cheaper than to equip with connected Philips Hue bulbs for example.

One can imagine many other applications:

  • Order the opening of an electric gate
  • Driving the gate trigger
  • Control the opening of a garage door
  • Piloting a garden sprinkler

Itead also offers other mounting examples for controlling two motors. It is possible to control a maximum of 2 90-250V motors or 2 DC motors 5-30VDC.

Please note that only one motor can be operated at a time.
Sonoff 4CH Pro AC motor Sonoff 4CH Pro DC motor

Install the EWeLink app for iOS or Android

Go to the store of your smartphone or tablet (iOS, Android) to install the application. The application is totally free and without any additional InApp purchase. Attention, there are two versions. Do not take the BLE version for controlling home automation devices in bluetooth (strange that Itead has developed two applications)

ewelink apple store

There is no advertising on the app and the icing on the cake, it is translated into French (except for a few messages from time to time, but nothing blocking).

To run, you will need to create a user account. Itead is satisfied with an email (advised) or a phone number. This account allows Itead to drive devices compatible with WiFi or 4G even out of your home. After entering your details, you have one minute to validate the registration by entering the PIN sent by email (or SMS) and your password, it’s a little short …

Unlike the MiHome app from Xiaomi, I did not observe any 4G latency. The app is simple and effective as you will see.

eweelink user account

Add the 4CH to the EWelink app

Once connected to your account, turn on the 4CH and press a relay control button for 5 seconds. The blue LED flashes 3 times and then starts again. The 4CH Pro is ready to be integrated.

You must be connected to the same WiFi network as the device during the inclusion phase.

From the application, press + at the bottom of the screen to start adding the device to your user account

3a bouton add sonoff 4ch pro

Pass the first information screen to access the password entry. The WiFi network is preselected. It seems that the application automatically selects the network with the best reception level. Specify the network password and continue.

sonnof 4ch pro configuration wifi

Module configuration ends in seconds

sonoff 4ch pro avancement configuration

You can give a name to the device to find it more easily if you have many

sonoff 4ch pro name device

It’s finished, your Sonoff 4CH Pro (or 4CH) is ready to work!

sonoff 4ch pro ready to use

The arrow to the right of the block provides access to the advanced functions and settings of the device. The other functions are detailed afterwards. To access the settings press the “…” icons in the upper right corner.

9 sonoff 4ch pro detail appareil

It is possible to rename each channel (relay), the device name, update the firmware of the 4CH Pro, activate or deactivate the vibration of the smartphone which signals the validation of the change of state of a relay. Finally, it is possible to choose for each relay the behavior at power up:

  • Enabled (default) on power-up
  • Off (default) when power is turned on
  • The previous state (Restore) is restored.

sonoff 4ch pro device info page

Other Features: Timer, Sharing, Countdown, Scenarios

The EWelink app offers some useful additional functions

Timer (Timer)

It is possible to set up to 8 timers which can be executed once or at regular intervals. Practical to activate the garden watering pump every morning at 7 am, light a lamp to simulate a presence …

sonoff 4ch pro minuteur timer


The countdown activates or deactivates a relay after a certain time. Practical to stop a device automatically after your departure

Sharing devices

Finally, you can give your Itead devices access to other family members or friends. For this, each person must install and create an Itead account. Convenient when you go on holiday. You can very easily allow a friend to open the portal from his smartphone.

sonoff 4ch deballage test ewelink

Here, in a few minutes you will have a home automation installation clean and perfectly integrated with your electrical installation. Only regret, both models do not offer energy consumption measurement (like the SONOFF POW). This would be a real plus for v2. If you are a beginner in home automation, the 4CH Pro is ideal because you can start to “play” safely by powering the module in 5-24VDC. SONOFF boxes are very often found in promo on the main Chinese sales sites, do not hesitate to compare before buying on Banggood or AliExpress for example. Shipping costs are often offered.

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