No neutral means, that the module does not require a neutral wire to power itself, but it has to be part of the circuit with the load (lamp). As it part of the circuit, it has to be always closed to power the module. When the light off (assumed that the circuit open), it is actually still closed, but the module does a parasitic load only, and not enough current passed through to make the bulb light up.
The switch with the no neutral module is basically changing the state of the module and does not control the circuit to be open/closed. It does the same way as a zigbee command would do. Some modules allow yo set what triggers a state change from a switch, being open/closed (change) or if open then state off, if closed then state on. I don’t own any of these zigbee modules to try them, so I cannot tell how they actually behave. But I assume the first, change of the switch causes change of state.
I´m looking for an exact replacement for the fibaro double relay switch just using zigbee so beeing able to connect to a hue bridge used as my zigbee controller.
Those “no neutral” modules reside on the live wire in the light switch wall socket and are supplied with power due to the parasitic drawn mentioned by @GSzabados. The module can be also attached to a doorbell-type monostable button for turning the life on and off when you don’t want to use Home Assistant (also to reset the module when you long press the button). Although this seems to be much simpler solution than the modules that require the neutral wire connection, from my experience it has several drawbacks:
The relays without neutral wire are Zigbee end devices and do not extend the Zigbee mesh network range unlike the relays with the neutral wire which are valid Zigbee routers
They allow for much smaller loads than the modules with neutral wires - up to 100W or something unlike the ones with neutral which allow for over 1000W. Shouldn’t be much of an issue with modern LED lights, but if your LED strip is long, it might require more than 100W (not to mention the old bulbs)
If your attached light consumes too little power (less than ~4W), the module might not work
If you happen to mess up the live and neutral wire when connecting the module, the module might stop working permanently. Sounds incredibly dumb, but that’s precisely what I did, since I’ve been testing it by attaching the cables outside the wall and then plugging it to the wall socket for testing purposes. This way it’s very simple to mess up the live and neutral wires when you plug the cable in the wrong orientation - for normal electrical appliances it doesn’t make the difference, but those relays were explicitly told to be attached to the live wires. Since I’m not an electrician, I can’t really say why my module broke. However, the fact is that since I did it, I can’t make it work anymore.
As I said, the advantage of this particular relay model without neutral wire is that it works with the monostable buttons. The model equipped with the neutral wire works only with the bistable buttons, which is just stupid - my button on the wall can be pressed and it won’t magically “unclick” itself if I open Home Assistant and turn the light off.
However, looks like Aqara decided to make the legends come true and released the European version of their in-wall relay module:
From what I see, there is only 1-gang version available, in two variations - with neutral and without neutral wire. According to FAQ on their page, it works with both monostable and bistable buttons which is controllable from the software - not a fan of that, this setting is probably another custom Zigbee channel and won’t be available from the ZHA. On top of that the bistable button setting is a default one - I don’t know why all manufacturers hate the monostable buttons so much.
I bought the neutral wire equipped module and should get it soon since it was already shipped (from my country, not China). Can’t wait to have it tested - Aqara has already proven they can produce a ZCL-compliant device (their smart plug) so maybe this one won’t require custom ZHA device handler either and the monostable button support would be possible to activate by issuing custom command (saw such option somewhere in HA). Fingers crossed.
Thank you for your insights, i will go ahead and buy one, lets see if i can get them to work.
Actully i´m looking for an even simpler way for installations where there would not be enough room in the wall. Do you know if there is a complete replacement for the in wall switch, in my case Busch Jäger, with one that has zigbee already builtin but still directly wired to the lamp.
Something like the aquara in wall switches but working with hue
Okay, so I’ve got my Aqara module. Nicely built, as all Aqara stuff and most importantly works perfectly with HA, just like the smart plug I mentioned - no need for ZHA device handler for its basic functionality. Here is the screenshot of the device screen, with the entities which are of the same types as the ones in the smart plug (power consumption, on/off toggle and some field which is always unknown):
Long pressing attached button doesn’t reset the module, so it’s a slight disadvantage from my point of view, but not a huge one. Unfortunately there is no entity for switching the button mode between monostable and bistable - I kinda expected that to be honest, but seeing it not being there is always a bit disappointing.
Connected it to Aqara hub with the Aqara app, also to check if there were any firmware updates (none yet) and immediately after adding the module I was given an option to choose the type of the button that was connected to it. After reconnecting it to Home Assistant I went through the “Manage clusters” menu in the ZHA device screen which has the list of clusters, their attributes and commands but didn’t see anything that would look like a button mode. There must be a way to communicate with the module and tell it what button it should work with, but Aqara might’ve went with some custom implementation since HA didn’t discover any manufacturer-specific clusters. The compliance documents from the Zigbee Alliance page didn’t help or tell anything about the custom cluster either (or maybe I just don’t know how to read them). Wondering if that’s something that could be debugged by somebody equipped with a Zigbee sniffer and taken care of with the help of ZHA device handler quirk? Having a dedicated entity for switching a button mode sounds a bit excess, but being able to issue a command from the “Manage clusters” menu to a cluster that would change a button mode would be fantastic - it’s configuration thing after all and is not done all the time.
Hi @konpon96, it’s been a while since you reported here, thanks for the detailed write ups.
Anything new you have to add since you last wrote?
I’m on the lookout for similar devices (dimmers, actually) and have been looking at this model (QS-ZigBee-D02-TRIAC-2C-LN 2 gang dimmer with N):
Those only work with push buttons (monostable switches), as it would be pretty weird to operate with a rocker one. Why would switches (as opposed to dimmers) only work with bistable ones is beyond me.
Here’s a post from hejdom about them:
Was wondering if anyone has experience with those above? Or maybe similar ones?
Hi @Saviq, unfortunately I didn’t have much time to continue with my Zigbee endeavours recently. So far the only one I saw was the new Aqara switch, but its monostable button support works only with Aqara Hub - they don’t expose configuration capability in a way ZHA could see it. I guess it’ll be necessary to write a custom ZHA handler for it to work, since I doubt Xiaomi will release a firmware update that will suddenly expose this setting in a compliant way. Maybe once I have a bit more free time I’ll research how to develop the handlers and how to reverse engineer the signals exchanged by Aqara hub and the switch. I thought that I’ll just wait for the new Zigbee devices to pop up on the market, in hope that there will be one having all the features I’m looking for like the monostable button support and ZHA compliance.
As for the Tuya dimmer, I have both 1-gang and 2-gang versions of it:
I described them in one of my beefy posts above - the reason why I didn’t write much about them in comparison to the switches is that dimmers simply work flawlessly. Not only they are properly discovered by ZHA, work with monostable buttons (as all smart home switches and relays should) but they also allow for resetting the module without digging into the wall - just long press the light switch. The only feature I saw in other Zigbee dimmers which is not available in the Tuya one is possibility to configure minimum light output - it just dims the light to zero and then goes up. One of the models I saw with the minimum light output capability is one below. However, I don’t have it and I cannot say if it works properly with ZHA:
That’s interesting, maybe they exposed it as ZCL-compliant manufacturer channel after all? I’ll check it out, but considering how manufacturers approach Zigbee, I don’t really have huge hopes about it - won’t be surprised if it turns out to be another vendor-specific implementation, not available without developing a custom ZHA device handler.
Idle question: does zigbee compliance require a device to work with monostable buttons? I can see why they are needed with a dimmer, but not necessarily with an on/off switch.
Similarly, what does the standard require for minimum brightness?
I’m pretty sure that Zigbee compliance is mainly about defining the channels (eg. on/off, power consumption etc) in such a way that it’s possible to use Zigbee hubs from different manufactures, much like in case of ZWave. What’s more, it doesn’t seem to force the manufacturers to implement everything in the compliant way, as the new Aqara switch shows - it’s present on the Zigbee Alliance site with all the documents, exposes basic functionality like on/off and power consumption to be used by Home Assistant without having to use a custom handler, but has the functionality of changing the button type which can be accessed only when connected to Aqara Hub through Aqara app.
That’s a shame, since unless the requirements for certification of Zigbee devices change to enforce proper handling of such a custom features, we will never achieve the same level of seamless experience ZWave ecosystem offers.
@konpon96, @nickrout If you are ready for a lecture regarding Zigbee compliance, then navigate to the SmartThings Community Forum and ask the question to @JDRoberts. He will give you a detailed answer what you need to know about Zigbee’s compliance requirements.
Some of the features what you are expecting are not necessarily part of the standard. Then companies implementing it through the manufacturer specific options.
If not, then I assume the dimming can only be done via zigbee, so what effect does pressing the switch have?
Do switch presses always control the attached circuit or do they emit a Zigbee event? I.e. could I have a switch connected to a light but have the physical switch actually cause something else in my HA setup?
Also regarding the 2 way switches/dimmers. I suppose it is possible to close the circuit via the switch and zigbee. This means you could end up with the 2 gang switches in different positions but the connected circuits in the same state (i.e. the lights both on)?
Edit: and since this thread is EU focused, here’s a new seller that seems to have entered the market in the EU. Haven’t heard of anyone using them yet though.
The dimmers can have one or two monostable (doorbell) buttons attached to them, depending on if they are controlling one or two lights. Single press of the button toggles the light, while holding the button down makes it change the brightness gradually from 100% to 0% and then from 0% back to 100%. They remember the setting, so if you turn the light off and then on again, the brightness will be the same as before it was turned off. There is no way to connect a rotary switch to it.
From my tinkering with them I can say that they always control the circuit. They are visible in HA as a dimmable light, so the most you can do is hook on the light’s standard behaviours (toggle, change brightness). That’s not bad though - the fact that the button controls the circuit directly means that the switch won’t go fully dumb when the Home Assistant malfuncitons or goes down.
You’re right about the switches - the fact that they can be controlled both by the button and Zigbee means that the 2 gang switches could end up in different positions, which doesn’t look very well. That’s why I’m waiting for some manufacturer to finally release an in-wall switch that would work with Home Assistant AND the monostable buttons. Aqara switch does support both bistable and monostable ones, but the mode toggle is implemented in a way that can be changed only when paired with Aqara hub - there is no option to do that from Home Assistant.
These iolloi dimmers look interesting. Although they charge quite a lot for their rotary dimmers, the in-wall mounted ones are quite decent with their $45 price tag - especially considering that they have a hardware minimum brightness setting. However, if that’s not required then the Tuya dimmers seem to be much more wallet-friendly option. Would love to see iolloi release a switch though - maybe it would finally be my Holy Grail of Zigbee switches that would work with the monostable buttons.
Thanks for the great reply! That really clears a lot up. I didn’t realize the dimmers are designed to work with only monostable buttons.
How is it having such buttons in your house? At least in my experience it’s not common to have monostable buttons indoors. Do people comment on it? Does it take time to get used too (thinking of WAF here).?
I don’t know, since I didn’t finish my HA-based smart home project due to the lack of the in-wall light switches on the market that would be compatible with monostable buttons and ZHA in Home Assistant. As if it wasn’t bad enough, I can’t even continue to look for them due to lack of time. At this point I hope that if I finally manage to get back to that project, there will be something on the market that I will be able to use - maybe the group that Apple, Amazon, Google and Zigbee Alliance formed will finally clean up the Zigbee smart house world by then.
I don’t imagine monostable buttons to be difficult to get used to - after all, we make our button pressing decision based on the fact if the light is turned on or off, not on the button’s position. The reason I didn’t opt in for mounting the bistable button in-wall switches is purely the aesthetics, or rather the lack of it when the buttons are in the different positions. I can imagine the guests to be confused when they discover that the buttons act like the doorbell ones, but in fact it’s not entirely uncommon to use the monostable buttons to control the light - I’ve seen plenty of these used in the staircases, complete with a timer to turn off the light after some time.
This way it’s very simple to mess up the live and neutral wires when you plug the cable in the wrong orientation - for normal electrical appliances it doesn’t make the difference, but those relays were explicitly told to be attached to the live wires. Since I’m not an electrician, I can’t really say why my module broke. However, the fact is that since I did it, I can’t make it work anymore. 
Not only they are properly discovered by ZHA, work with monostable buttons (as all smart home switches and relays should) but they also allow for resetting the module without digging into the wall - just long press the light switch. The only feature I saw in other Zigbee dimmers which is not available in the Tuya one is possibility to configure minimum light output - it just dims the light to zero and then goes up. One of the models I saw with the minimum light output capability is one below. However, I don’t have it and I cannot say if it works properly with ZHA:
At this point I hope that if I finally manage to get back to that project, there will be something on the market that I will be able to use - maybe the group that Apple, Amazon, Google and Zigbee Alliance formed will finally clean up the Zigbee smart house world by then.