How does failsafe behavior work with SONOFF S20 with weak WIFI connection

  • Platform information:
    • Hardware: Synology& ITEAD S20 SONOFF
    • openHAB version: 2.3
  • Issue of the topic: How does failsafe behavior work with SONOFF S20 (internally using a ESP8266) with weak WIFI connection

Beside controlling my heating and suqeezebox Radios I would like to continously extend the use of Openhab. Next mini-Project (understanding the automatic Control of devices depending on ambient luminous intensity). My garden house will be the location of the S20 device. The WIFI Network is pretty weak there and I am asking myself how OPENHAB is behaving in this case:

  • Is the command to activate/ deactive the S20 send once to the device? Is it send periodically?
  • Is there a Feedback Signal send from S20 to execute some kind of closed Loop System?
  • What happens to S20 when WIFI Connection is temporarily lost?

I am not sure if this is the right forum- please guide me to the correct if I put it wrong.
Thanks for your suport

What firmware will you use on the S20?
If it’s tasmota, the firmware will continuously try to reconnect to the network.
However, it the connection is lost the device instruct the MQTT broker to publish a LWT (last Will & Testament) topic (eg. tele/sonoff/LWT with the payload Offline). You can pull this in OH and see if you sonoff is still on the network.

Have you considered adding a wifi AP nearer the garden house to ensure better reception?

Yes- I want to use the tasmota one.

Two issues:
Sender: LWT with the LWT and try to resend command when reconnected- understood so far
Receiver: Is the tasmota staying with the last commend received or going to OFF state when WIFI lost?

I installed a brand new repeater (Fritz 1750E) which needs to go through 1 brick wall and about 6m with a thin wooden gardhouse layer. The reponse to the WEMOS D1 mini unit without external antenna though is pretty weak (<96dBi)

You can configure that with tasmota

Ahh- did not know that
So I will order one device for testing.

Thanks for your Support.

Hello! I want to add your comment. If the connection of the wi-fi is very weak, then the Sonoff (tasmota) devices die after some time (you can throw it away). I have already lost several devices, I had to expand the network of Wi-Fi, this solved the problem.

Can you tell more about this? I noticed my S20 does get warmer if the AP is not reachable and it keeps trying to reconnect, but are you saying it will actually overheat and kills the device? How long did it take? What was the environmental temperature where the broken devices were located?

If this is indeed reproducible it seems like a major flaw in the firmware and/or the S20 and maybe even a fire hazard.

Hello! The temperature is about 5 degrees Celsius. This is a cellar. I do not think that this is dangerous, I do not think that this is the problem of firmware. Over time, the device stops working, tests showed that after it stopped working, when it turned on, next to the access point, it shows a very low level of the signal of the wi-fi, for example 5 although before commissioning it was 100%. Ie it can no longer be used. As far as it is heated, I can not say. I happen there very rarely, remote control.

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Huh, that’s really strange. Good to know nonethless, if my devices ever stop working I’ll at least have a hint where to look.