Aqara wall switch turns off on load increase

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Hi and thanks for interest.
I’ve faced with undocumented behavior of Aqara Wall Switch (single key, no neutral line). I’m using it with Tradfri bulbs — don’t judge.

When bulbs are off for a while (at least for 15 seconds), turning them on (or just one of them) causes wall switch to turn off itself. This is a load increase protection, I guess.

I thought that was a factory defect, so I’ve replaced my wall switch with a new one — nothing changed, new switch continues to behave like its predecessor.

Have someone else faced the same problem?
Do you have any ideas to fix that?

(And yeah, I’m already created an automation that turns switch on when it’s turning off).

After few days of research I found a simple answer.

When relay inside of wall switch is turned off, the switch is getting power for itself via incoming live wire and outcoming wire as neutral (while your load is not connected to line, live wire can be used as a neutral line).

But when relay is turned on, Aqara can’t power itself with the method above and requires a minimum wattage of 3W on load to keep itself turned on.

What’s happening when your load consumes less than 3W?
Switch simply turns off – you can’t control your live line anymore, pressing on button does nothing, but relay is still turned on.

When load increases and connected devices start consuming at least 3W, wall switch turns on again, discovers relay turned on, and turns it off.

So all you need to avoid this issue is to provide a minimum load all the time.

Hi @alexfrom

I have the same problem. How can i provide minium load all the time? I dont have electric knowledges

Also have this issue. I’m using the single key no neutral model.

It worked fine for over a year then started to exhibit this behavior. Swapped it out with another piece I had in the other room and the problem went away, but came back after a month.

I think you’re pretty close on the root cause. My load is a DC ceiling fan with LED light. I only encounter the problem when the fan is on at low speed but the light is off. Based on user manual the power consumption is exactly 3W in this state. Essentially the switch can work fine to turn on/off like this, but will lose ability to turn off after being on for about 15-30min or so (never measured the exact time), which I call the paralyzed state. In order to recover, I have to increase the load, either by turning up the fan speed, or turning on the LED light using the fan remote. If I had clicked the Aqara switch any number of times during the paralyzed state (or toggled any number of times via App/Zigbee), the switch obviously ignores it, but will turn off within 1 second after performing the load increase recovery. The switch will not automatically turn off after load increase–it must have received a switch command during the paralyzed state at least once first.

What this tells me is that during the paralyzed state, the switch is still registering the keypress or Zigbee commands but is simply refusing to release the relay. So I don’t think it is a power loss issue to the switch electronics because the relay is clearly still energized the whole time, plus the switch remembers if it was commanded to turn off and executes it once load has increased. To me it seems like a logic/coding issue where somehow there is a timeout period after relay turning on where if the load drops below a minimum (3W) the electronics ignores all state changes.

There must be a shunt capacitor in there which the switch uses to power itself. I wonder if that can be replaced or adjusted so that the minimum threshold is 2W instead of 3W.

I have found a fix. You need to place a shunt capacitor parallel to the load. In my case I used a 470nF rated at 630V. My mains is 230V 50Hz, so adjust according to your mains.

I have confirmed that what is happening is that the logic board loses power within 10seconds of the relay turning on and the load is <3W. You can verify this by removing the rocker plate and watching the blue LED. When load drops below 3W or starts below 3W, the LED will start to blink and gradually fade away (the LED should be solid blue when the relay is on) and MiHome App will no longer detect the switch. The relay appears to be energized independtly.

When load is increased, the blue LED returns and the switch becomes responsive again.

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