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Upgrade firm to 3.5 now house lights wont stop flashing

Hi all I have loads of sonoff mini installed controlling the house lights. Yesterday I update ewelink and then updated all firmware on the mini from 3.4.0 to 3.5.0. All went well apart from 1 which every second or less turns the hall lights on then just as quickly turns them back off constantly. I had one spare so I removed the Mini that was constantly flashing the lights on and off and replaced it. Then I upgraded the firmware to 3.5.0 and now that one is constantly flashing. Has anyone else had this??? Any ideas for a fix??? Is there anyway I can re-flash with 3.5.0 incase it didn't flash properly? ?? Is there away to put 3.4.0 back on it???

11 people have this problem

The issue remain the same, the issue is with sonoff firmware not with EWeLink App
I've go an answer from the support. They put different types of efternal switch in the FW 3.5.0 and sonoff became very EDS sensitive for terminals S1 and S2. In two weeks the new EWeLink App version should add possibility to choose the type of external switch. After you will choose the right external switch type the problem should disappear.

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Guys I found the SOLUTION. if you have the same problem, LIGHTS BLINKING AFTER 3.5 UPGRADE, just put a capacitor 104 between terminals s1 and s2, the same in the photo , that solves the problem.

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Sounds good. Thank you.


aparentemente funcionou comigo, fui em configurações do dispositivo, modo de disparo externo e escolhi a opçao seguinte modo

Conecte à chave de travamento, chave SPDT.  Ou conecte ao sensor de contato seco.  O status do relé seguirá o status do comutador externo ou sensor externo.


apparently it worked for me, I went to device settings, external shooting mode and chose the following mode option

Connect to the locking switch, SPDT switch. Or connect to the dry contact sensor. The relay status will follow the status of the external switch or external sensor.

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Capacitor works for me. Thank Eduardo Galvao

This is my reply from support

Dear paul,

What we did in V3.5.0:
We add a function that allows customers to choose the switch type of the external switch. There are three types:
1.following mode
Connect to latching switch, SPDT switch. Or connect to dry contact sensor. The relay status will follow the status of the external switch or external sensor.
2.edge mode
Connect to latching switch, SPDT switch, commonly used in dual control light switch.
3.pulse mode
Connect to momentary switch, commonly used in door exit switch.
The app will support choose the mode in the next version.

The default switch type is "2.edge mode".If the switch connected doesn't match the default switch type, it will show unexpected problems.
Could you please confirm your external switch? If you make sure the switch type matches the default type and the wiring has no problem

Lets clarify some wiring terminology


The word “Gang” represents how many switches there are on a single wall plate.


 1 Gang, a single switch on a single plate. 2 Gang, two switches on one plate. 3 Gang, three switches and so on.


The word “way” tells you how many switches control the same light or group of lights

1 way, one switch controls one light or one group of lights.

2 way, two switches controls the same light or group.

3 way, three switches controls the same light or group and so on.


The switches themselves come in three types 1 way or 2 way or an intermediate. You can only use a 1 way in a 1 way setup. But a 2 way switch you can use in all setups 1 way and 2 way 3 way and so on.

I always buy 2 way switches as they cost about the same and they are universal. Also if you are using it on a 1 way setup and you damage the screw or thread on the L1 side you can use the L2 screw or that side as a spare.

So if you buy a 3 Gang 2 way switch you get 3 switches on a single wall plate that all have 2 way capabilities.

If you are setting up a 3 way you need an intermediate switch and two 2 way switches. If you want a 4 way or more you just add more intermediate switches in the circuit.


This info I’m sure everyone knows but if you don’t.








support asked me for a video of the problem

link to video of problem

: )

The problem is the mini only uses around 3volt on the sw1 and sw2. Which works fine if you are using short wires.

But when you’re using long wires or 2 way or 3way or more that voltage isn’t enough. Old wires old switch or low quality switches also cause a problem with voltage drop.

Some people had problems when they turned the switch on the voltage between sw1 and sw2 wasn’t high enough to toggle the state so the lights didn’t come on.So the firmware was updated to make the sw1 and sw2 more sensitive and that caused a problem where it can detect false positives or if the wires are to long it’s detecting the voltage as pulses and each pulse causes the switch to change state flashing your lights.

The shorter your wires and the least amount of way (2,3,4way) the easer the fix if any actually work for you.

Using a 104 capacitor placed between sw1 and sw2 builds the voltage up to around 50v so has the potential to flow through the circuit. The smaller the circuit the more chance of it working. The longer the circuit the more unpredictable the results. Toggling the switch on then off and back on again can still cause this fix not to work and that’s if it worked in the first place.

Your light switch may not conduct low voltage very well as it was designed for 240 or 110 voltage. You could test your switch by temporarily disconnecting your current switch and wiring it to a low voltage one. Don’t forget if you’re in the UK or anywhere that earths the back box that box will be a negative 240volts so don’t let your positive sw1 and sw2 wires touch it. Your mini wont like 240v been run though a 3v circuit.

Old wires can also be a problem so replacing them could help. Some people have used cat5 or 6 hopping to get less voltage drop.

I’m having problems with 2 circuits a 3 way and a 4 way. The cables are new 1.5mm and new good quality switches.

To be clear.

I’ve renewed the lighting cables.

I’ve renewed the switches.

I’ve tried using a 104 capacitor.

None of which have worked for me but some others have had some luck with these fixes.

The only fix I can see working for everyone would be to change the Sonoff mini hardware to use 240/110 volts for the sw1 and sw2. There's differently a market for both a 3volt mini and 240volt mini.

So please bring out a Sonoff mini Plus : )

So if it is a firmware problem and itead is taking too long to solve, maybe if we upgrade to tasmota may solve it?
Sorry but it won't

what would the solution be? a group of things? expect 3.7.0 firmware soon + capacitor?

because i am running 3.6.0 and still have problem, and weird thing is, only in bathroom... rest of house seems ok so far

These Are pretty much the only things you can do. 1. Capacitor 2. Update your light switches new one may have better conductivity. 3. If possible Shorten the length of cable running from s1 to s2 4. Change wiring to a better Quality one so you get less voltage drop 5. If all else fails use a different product. Some of them are a bit extreme but they have been known to work...

is there any difference if I put capacitor in the S1/S2 Sonoff side or "s1/s2" switch side?

As they were installed above the plaster ceiling, it would be much easier installing capacitors in the wall switch side

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