Maybe I am missing something, but wouldn’t the simplest solution to the two/three wire problem be a light switch with a built-in battery to accept commands when the switch is off? Thereby bypassing the need for the neutral wire.
There are some good battery powered switches, but they don’t actually control the current flow. They just act as wallmount remotes. In the U.K., Devolo and Popp make nice versions of these that will work with SmartThings. But then there has to be some device which actually does cause the lights to go on and off. It could be that the lamps themselves are smart or it could be and in the wall micro, not battery-operated, installed in the ceiling Rose where there typically will be a neutral. So the switch sends a message to the SmartThings hub which then sends the message on to the device that does control the brightness of the Lamp.
Note, though, that all of those are “surface mount” devices which are mounted on top of the wall, not inside it.
The reason why we can’t just hook a battery to the radio that is inside the wall is that pretty much any battery-operated device inside the wall becomes a fire hazard. Safety codes generally prohibit that in both the US and the UK.
Thanks, I have seen those, however, the problem as I understand it is that UK 2 wire systems leave the switch with no power when the switch is open, hence it cannot “listen” for the command to turn on the light. If a battery was incorporated into the switch to power the zwave device when the switch was open, it would solve this problem. Allowing a “normal” current control. The Lightwaverf dimmer seems to be the only other option apart from a device similar to the Fibaro universal dimmer and potentially deepening the patress. However, the Lightwaverf dimmer is only rated to 250w, I have 8 x 40w on one dimmer. I was simply exploring the feasibility of a 2 wire switch controlling the current with a built-in battery handling the zwave.
That’s correct, that’s why there has to be an additional device involved, either an in wall relay at some point on the circuit where there is a neutral, or by using a smart bulb such as a Phillips hue.
The Fibaro in wall dimmer micro can be used with just two wires, so it’s a popular solution, but as you noted, it’s not just the neutral that’s the issue, it’s also the size of the pattress box.
a battery was incorporated into the switch to power the zwave device when the switch was open, it would solve this problem.
Putting a battery inside the wall solves the problem of powering the radio, but if you burn down your house it’s not really an effective long-term solution. 
Our goal is never just to make a single light turn on–it’s to safely incorporate home automation controls into your overall electrical system.
The Lightwaverf dimmer seems to be the only other option apart from a device similar to the Fibaro universal dimmer and potentially deepening the patress. However, the Lightwaverf dimmer is only rated to 250w, I have 8 x 40w on one dimmer.
There are some additional options. A common one is to put the micro at the ceiling rose rather than at the wall switch. There’s almost always a neutral there.
Another option is to use the energie or Lutron switches with one of the community created methods, although at present both of these require also using a “man in the middle” server device, typically a raspberry pi, and that requires more effort and technical set up than many people want to do.
Just this month at CES 2017 and official SmartThings/Lutron integration was announced, with the lutron staff saying they expected it in place by March. If it does arrive in that timeframe, that will provide another set of alternatives.
But for now, the most effective may be just to consider putting a micro at the ceiling Rose. That will give you a choice of more brands, as well.
Thanks, micro in the ceiling seems to be the most effective and easiest way to go.
As an aside, why would a battery (removable) in the light switch be a fire hazard? Surely it’s no worse than a backup battery in a smoke detector.
I think you’re right. There’s just no standard that currently allows for this right now. Automation is still a relatively niche industry, hopefully if it becomes more mainstream, then standards will be created that allow for safe inclusion of batteries for such use.
The smoke detector is also a surface mount device, it’s not sunk inside the ceiling.
You asked why Z wave light switches don’t just have a battery inside. The answer is that the ones that are surface mount devices can. The ones which go inside the Patress box inside a wall would not comply with safety code. There are actually multiple technical reasons why this is true, but the fact that it’s true is why those devices are not on the market.
Thanks again for the response. It seemed such an obvious solution that I wondered why it hadn’t been done.
Looks like I need the older Fibaro FGD-211 as the 212 is only rated at 250w.
1 Like
Thanks for the heads up about the batteries, just checked. I had one leaking. Brand new hub, only installed in December. Have now removed.
1 Like
I have just had another thought. My main problem is both only 2 wires (solution dimmer in ceiling). The other problem was that the current set up is 8 x 40w too much for the Fibaro 2 (250w), the 1st generation Fibaro has a 500w rating, but very difficult to find in the UK now. The obvious solution came to me today. Bit slow, I guess, replace existing 40w with 4w LED’s! Job done, now I can use the second generation.
1 Like
Does anyone know if the new Sonoff pow switch could be used to emulate an inline relay to control the lights but know the state, so that it could “interact” with the physical switch on the wall… I know there are a few rather dull looking zwave light switches that will run if you have a neutral wire. (I am lucky i do) and i know there is an expensive relay that will do it from Fibaro i think, but i want the affordable option. (i will make an informed decision on the safety merits of one of the newer sonoff devices in good time) Replacing with a sonoff touch is one option for some lights, but not good for 2 and 3 gang etc… I want to be able to purchase a nice standard brushed silver light switch and use a relay… (either momentary push switch, rocker or switched style) (the sonoff pow is a bit big so that might be a prob, if it it could be setup to work )
any thoughts would be appreciated… read too many forums and have lost the plot on this topic in the last few days, but still learning. I am a newbie to HA
The Sonoff pow switch is an inwall Relay, just like the Fibaro micro, it’s just using Wi-Fi instead of zwave. It says it’s CE certified and it’s not using a battery, so it should be fine as far as safety goes. It works exactly the same way as the other inwall micros, so you can use it with an existing switch, but it’s still going to act as a momentary, so the switch may not work quite the way you expect.
I don’t know if it has an open API, so don’t know if there’s going to be any easy integration with SmartThings.
Here’s an article from a guy who did an MQTT/Thingspeak integration, but it’s very technical:
So… I can’t say how well engineered these devices are, but if they have the CE certification they should be fine for the described purpose.
As far as coordinating with the physical switch, that’s going to work like any other in wall micro.
And as far as integration with SmartThings, something should be possible, I just haven’t looked deeply enough to see if there are any easy options.
Note that it’s only Spec’d for a max load of 10 A, so it should be fine for most lighting implementations , but you wouldn’t want to run a blender or a coffeemaker on it.
https://www.itead.cc/sonoff-pow.html
@erocm1231 has done a lot with Sonoff devices, he might have more to add.
Also, since it can be hard to be really clear on all these technical distinctions, I’m not saying that you can take anything with the CE Mark and put it inside a wall and use it safely. Rather that a device that is intended for in wall use, like this one, will be rated for that purpose when it receives its CE Mark authorisation. I hope that’s clear. 
Thats all clear , thanks. I know it can be used like a normal relay, in parallel. But what I am trying to establish is … with an appropriate device driver, and the correct wiring, can it be setup to work in conjunction with the physical switch, so if the physical switch is on, it knows the state (using the pow capability) and vice versa if off, eg read the power consumption to establish what state it is in (now i know with some “official” expensive solutions i think they are using this technique, but it is not working on low wattage leds, because of low current.) Then if i switch on via smartthings, it will turn off if physical switch is on (so would need to work like two way switch i guess, or a momentary switch with latch relay maybe ?
trying to understand the art of the possible, with limited knowledge at this point and dont want to reinvent the wheel if it has been done or is being planned… … (a low cost version i mean)
folks have connected these to smartthings , so that is doable i believe via wifi.
It will likely not fit in a switch box. Also, you would have to do some soldering if you want to hook a physical switch up to it.
1 Like
yep, i was coming to the conclusion it would only be suitable in the ceiling. Can you give me a pointer on how it would need soldering. I am assuming the normal pinouts wont be enough to connect in the way i want and therefore would need to pick up off the relay or something else on the board ? thanks
But why not make a switch that is effectively a Fibaro Micro Switch with front switch? all powered .
Or a Devolo that can be optionally wall powered instead of battery for those wanting a permanent maintenance free switch?
Personally I would like to see a Devolo style switch that has a built in connector to permanently connect the light socket to turn it in to an always on with an emergency slot maybe for some compliance to kill power.
That way you have no batteries, you use the existing hole in the wall and you keep the look of a normal switch.
Agree totally, and they do have these but the choice is very limited to a few white or silver plastic examples which I dont like. Nobody has brought out a premium one like the lightwaverf for example. The purpose of this exercise is to be able to automate 15+ lights at a relatively low unit cost per light. (eg something more like 300gbp for the lot rather than 800) using existing face plates.
The new sonoff products that have at least some level of conformance certification now, and look tantalizingly close to being able to do this and be relatively safe. Although ultimately a nice 1/2/3 gang brushed silver, zwave controller switch from a manufacturer is what i want.
I believe some have got the lightwaverf working through a bridge to smartthings, but i would like to invest in something with less hops to make it work. I am sure it is only a matter of time before more products are available from manufacturers… But I want to take the plunge now.
issue is with Hue bulbs or other smart bulbs you need a dumb switch to ensure power is always available. you need both products depending on your use.
The dumb market doesn’t cater for uk face plates (Devolo etc is the only option but battery powered)
or switch control (Fibaro/lightwave) but microswitches need large housing or in the floorboards. and lightwave needs a dedicated hub.
Battery power is good for some things but soon Ill need to have a room to store spare batteries and 3 days to swap them all out!
1 Like
Hey everyone
Totally brand new to this, and I have not yet taken the plunge into home automation. I got an Echo Dot for Christmas, and realised that it would be perfect for voice-activated automation stuff… and then I fell into the Pit of Light Switch Despair.
Just like @109matt I’m in the UK. However, after purchasing a ridiculously old house where everything was terrible, I had the entire place stripped and refurbished, including all new plumbing and wiring. As such, everything is up to the current IEC standard and all of my switches and outlets are 3-wire deals (yay!).
I’m not terribly experienced with hands-on electrics & electronics, but I am a pretty experienced programmer, so when I discovered the API of SmartThings, I got pretty excited… and then pretty bummed when I realised the limitations of UK switch options.
I pretty much only want to control the lights and a few sockets (and maybe get a Nest or something similar) - I’ve got no real interest in motion or moisture sensors; mostly I just want light & heat. However, since we tend to have a LOT of individual lights (the living room has 9 wall-mounted bulbs and 4 lamps), I would definitely prefer a 1/2/3-gang 2-way switch over paying out for all those individual bulbs.
I would much rather use something like SmartThings that uses open protocols and a user-editable API, but at the moment it does look like LightwaveRF is the only system that might actually suit my requirements.
With all of that said… has anyone seen WifiPlugs? I stumbled across them by chance (http://www.wifiplug.co.uk/wifiplug-glass.html) - they appear to be UK-focused with their switches and plugs… but they do require a 3-wire system. The other thing is, I have no idea how compatible they are with SmartThings - they are apparently IFTTT-compatible (and so, by proxy, would be Alexa-compatible too), but they appear to have individual wifi connections for each switch/plug rather than being controlled by a central hub. Does that kind of thing work with SmartThings?
Sorry if any of these are dummy questions, but I only discovered ST was a thing yesterday, and I’m still crawling up the home-automation curve.
Not to steer you away from ST but lightwave will do your plugs and lights all in one no issue. Then have the heating separate. (Evohome)
Then your done nice and simple. But if you go ST you will be sucked in to automating everything.
1 Like