ITEAD Sonoff switches and sockets - cheap ESP8266 Wifi+MQTT hardware

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( ) #149

The missing certificate was bugging me too but hacking something together yourself will probably not be better nor cheaper… I’m a tinkerer in heart but it’s also nice to be able to buy a finished solution from stock for a reasonable price. To me these devices look well designed, I’d maybe not drive them with constant 16A though.

Of course not. Gogogo!

(Lionello Marrelli) #150

Someone published on youtube measurements with a thermal camera for a 10A load for different devices. (
I would say that these temperatures are too high even for a 10A load. If the boards are enclosed in abox heat will accumulate and temperature will increase further.
In order to drive 3.5kW (i.e. 16A @230V), the minimum copper diameter is 1.5mm. (more details
I am not an electronic expert, but tin is 5-10 times more resistive than copper: I would naively expect that the tin required cross section increases accordingly!

EDITED (Updated with temperature measurements)
I measured the temperature under 10A load: after a few minutes, the tin gets as hot as 120 degrees!
I added some tin and i also soldered some copper, but temperature on that part of the PCB was always above 100 degrees.

I would say that these Sonoff Pows are not well suited for currents above 5A (or even less)!

(Lionello Marrelli) #151

It is possible to set a Power limit for the switch. If the power exceed the threshold set by the command MaxPower for the amount of seconds set by MaxPowerHold then the device automatically switches itselff off.
It also issues a warning on the mqtt bus so that openhab can manage this exception.

A temperature reading would be obviously much better (which, by the way is available in my Fritz!Dect 200 reliable but much more expensive switches)

(Michael) #152

I have 4 of the standard Sonoff devices and 1 wall socket (UK 240 volt version). I was impressed by the quality of the build but not so happy about the solder enhanced copper tracks and the size of the relay. Luckily my applications are all low power but I made a mental note at the time not to use them with any high power devices.

I am an Electronics Engineer but have little experience with high current PCB design. However, you only have to compare the cable used in the UK to power 3KW appliances and these small copper tracks to realise that they are unsuitable for the specified 10 Amp current. A maximum of 3-4 amps maximum (at 240 volts) is my opinion.

(martiniman) #153

Hi, i use Sonoff POW and Sonoff-Tasmota firmware and connect to washing machine in stand by.
Set TelePeriod to 20 sec and look at Web page on Power value - it changes 0w -5w- 0w- 4w in 20 sec.
Power value sent to MQTT topic was sometimes 0w, sometimes 5w.
But i think Power value sending to topic must be AVG (0+5+0+4)/4=2.25w of power reading for TelePeriod for 20 sec.
Or i wrong?

( ) #154

Hello @martiniman, I didn’t quite get your question. Are you asking if the Tasmota firmware averages measurements? It does not. Evaluating measurements and processing them should be part of the next step. I can recommend Grafana to do so.

(martiniman) #155

Hi @ThomDietrich, i mean when i set Teleperiod to 20 sec, i want to receive sum of power measurement in 20 sec period.
Is Tasmota firmware send to mqtt sum of measures in 20 sec, or only last second measurement?

( ) #156

Wattage is a timeless unit.
The measurements sent are samples from the moment of sending and can be seen as the current state of the consumer (similar to brightness, speed or temperature of something). If you are looking for consumption over time you need to integrate over the samples (sum over time).

If this is in fact what you are looking for Tasmota offers the “ENERGY” topic, which does this job for you and counts kWh:

e.g. tele/sonoff-xyz/ENERGY:

{"Time":"2017-03-27T21:02:28", "Yesterday":"0.029", "Today":"0.020", "Period":0, "Power":4, "Factor":"0.28", "Voltage":236, "Current":"0.068"}

(Rossko57) #157

I wonder if the concern here is to do with the granularity of the power measurement. It’s a cheap device, expecting to read power consumption in the 1000-2000W area. I would not expect it to be very good at instantaneous measuring say 3W consumption, some form of averaging over several samples will be needed, and even then may not be very accurate.

(Elias Hackradt) #159

Hello Community I am trying to get my Sonoff itead Switch to work with openHAB.

Solved: My Old Problem

EDIT# I found out my topic is wrong it must be “cmnd/cmnd/sonoff-977686/POWER”

Now I can send ON or OFF command but it will not stay in this position, instead it switches itself back to the old state.
Someone knows how to fix this?

This is my current item

Switch LivingRoom_Light "Living Room Light"  (ALL, Office_Workstation, Office_First_Floor) { mqtt=">[mosquitto:cmnd/cmnd/sonoff-977686/POWER:command:*:default], <[mosquitto:stat/cmnd/sonoff-977686/POWER:state:default]" }


I changed the topic for the Sonoff Itead Switch to sonoff-977686 and now its working fine with the following Item

Switch LivingRoom_Light "Living Room Light"  (ALL, Office_Workstation, Office_First_Floor) { mqtt=">[mosquitto:cmnd/sonoff-977686/POWER:command:*:default], <[mosquitto:stat/sonoff-977686/POWER:state:default]" }

( ) #160

Hey everyone,

ATTENTION Version 5.0.0 specific information

just wanted to make you aware of the latest changes with Sonoff-Tasmota v5.0:

(Kim Skatun) #161

What is the dimension of the PCB(not case) of the POW module? Need to fit inside my wall box:) I am planning to control my heating cables and with the POW module I can also see how much heating cost!

(Chris Van Humbeeck) #162

I’ve measured 89 x 45 (mm). Seems to be in line with the design:

(Thomas Lang) #163

Did anyone have any luck with using the Sonoff SC with the Tasmota firmware? I had the sonoff S20 switches running in minutes, but now the SC will only send me default information over mqtt, no temp, or humidity etc…:

sensor/sonoffSC/INFO1 {"Module":"Sonoff SC", "Version":"5.1.0", "FallbackTopic":"DVES_F8B292", "GroupTopic":"sonoffs"}
    sensor/sonoffSC/INFO2 {"WebserverMode":"Admin", "Hostname":"sonoffSC-4754", "IPaddress":""}
    sensor/sonoffSC/INFO3 {"Started":"Software/System restart"}
    sensor/sonoffSC/STATE {"Time":"2017-05-17T11:14:15", "Uptime":0, "Vcc":3.138, "Wifi":{"AP":1, "SSID":"Wifi", "RSSI":62, "APMac":"10:FE:ED:C8:AA:AA"}}

(Tommy Sharp) #164

Hey guys, this is probably me not understanding a core component of OpenHAB…

I have a basic sonoff device. If I toggle the switch in my sitemap then the physical light switches off and on as expected.

If I use the physical button on the device to turn it on/off then my sitemap is not updated, but if I just refresh my browser and the sitemap then the correct state of the switch is shown.

I don’t have this issue with some other switching devices so I’m not quite sure what it could be…

Any help would be appreciated. This is my item…

Switch Sonoff01 "Salt Lamp" <light> [ "Lighting" ] {mqtt="<[mosquitto:stat/sonoff01/POWER:state:default],>[mosquitto:cmnd/sonoff01/POWER:command:*:default]"}

(Thomas Lang) #165

Seems like another power cycle has done the job, it’s now working :slight_smile:

(Elias Hackradt) #166

Someone else updated their Sonoff-Tasmota to Version 5.1.3 and noted that the topic changed from ‘cmnd/myTopic/POWER’ to ‘myTopic/cmnd/POWER’ ?

The full Topic was MyTopic and not the Topic :slight_smile:

( ) #167

many things changes with version 5.0, check here:
The switch of the topic structure was actually motivated by me :slight_smile:
I’ll have to yet update the openHAB wiki article on this change. I’ll post a note after this is done.

(Elias Hackradt) #168

@ThomDietrich @community
Did anyone of you guys flashed the SONOFF SC ? If so could you give me some guidance ?
I found found this image, but sadly this did not work for me.



Flashing the ESP8266

Flashing the ESP8266 is very easy since the header close to it has all the required connections (3V3, TX, RX, GND) and the button is connected to GPIO0. Press and hold the button while powering the board to set the ESP8266 into flashing mode. You will have to remove the TX jumper in the board to avoid the ATMega328P to interfere in the upload process.

Note! After flashing you need to set the baudrate to 19200

( ) #169

Would you please add your findings here: