Capture state of a physical light switch and questions about Aeotec Nano

My problem- I want to know the state of a light switch in ST. I want to keep the existing physical switch and I want to keep the existing lights it turns on. I don’t particularly want to be able to turn on the lights using ST, I just want to know when they are on and off.

Reason: I am trying to extend our outdoor lights as we have cabled lights on the house and (planned) wall lights on the back of the garden. It’s a right pain to run a cable to the new lights, so I want them to be ST controlled, triggered by the light switch being toggled.

Doesn’t seem hard but I can’t find a solution!

Dismissed ideas so far:

  • smart bulbs (one or many) in the existing lights, as on takes a while to sync and there is no off (as the power is turned off so they are just unresponsive)

  • clamp over the cables to detect load when switch is on, due to the price of clamps

  • MacGyver’d solution using a motion sensor board and a relay connected to the lighting main - can’t fit it in the light switch pattress or the wall cavity behind!

  • Similar approach with a smart socket taken apart, plus if it gets stuck off I have to take the wall apart to force it backy on (or to re-pair it!)

It cannot be this hard to detect if power is switched on, surely!

I also asked Vesternet and they drew a blank



What country are you in, and what is the physical style of the switch. This is going to make a difference.

That said, can I ask why you don’t want to just use an in-line relay? That’s what most people do, and they work well. You can keep your existing switch if you want, you’re just going to wire the smart device in between the switch and the lamps.

Aeotec nanos are popular and among the smallest. Vesternet should have those.

Sorry good point, I’m in the UK and it is a typical live switching switch.

Usefully we have neutral to our switch pattresses in this house (unused just passes through)

I would post a photo but it’s not much use with text to speech

I have no issue with a relay as such, just where to hide it inside the wall cavity



I have some vision problems, particularly double vision when I’m tired, but I can see photos unless it’s a bad day. I use text to speech because I’m quadriparetic, and don’t have much use of my hands, so I need voice navigation. :sunglasses: And of course others might be helped by the photos as well.

Anyway, I would just look at the micro’s. The Aeotec nano, as I mentioned, is one of the smallest and will usually fit in the Pattress box. If not, they can be put closer to the fitting or in a junction box or really almost anywhere along the circuit branch.

There are a number of different models, so you will need to check the specs to see what would work best for you (vesternet should also be able to help with that), but here’s one example:

Ah ok cool, I’ll pop a switch off the wall when I get a sec and take a photo

Those nanos are switches as far as I know, ie they go across the switch and allow you to turn the switch on and off via ST (and still have the option of on off via the physical switch).

However they don’t know if the physical switch has been changed do they?

There is an option here that I replace the physical switch with a blanking plate and stick a nano inside to do the actual power switching, and a zwave remote on the front of the blanking plate, so the switching is all via ST. Feels expensive though if I can be avoided, and has a wife annoyance factor if I break webCoRE as the lights stop working entirely!

It’s yes to both those questions, which is why it would solve your use case. :sunglasses:. You don’t need a blanking plate and another device, your existing switch wired to the nano will be used to trigger the light to go on or off, and the nano can still receive a direct instruction from the network.

Most people do end up changing the wall switch to a momentary/refractive design, but there’s already a lot of discussion on that in the forum and I’m tired today. If you can’t find enough explanation on that point, just ask and someone else can explain it. But it’s still just one smart device, the nano. The physical device on the wall is dumb but wired to the nano. So you get control of the lights from the physical wall switch or wirelessly. Both work.

Brilliant I had no idea the physical switch went into it, I missed that entirely, I thought you wired around it.

Surprised vesternet didn’t pick up on that when I asked them


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No, it’s very bad.

The purpose of an electrical box is not just to have something to screw the switch or receptacle into. The primary purpose of an electrical box is to contain the heat and arcing that could occur as a result of a short circuit or overcurrent situation. It keeps the surrounding materials (wood, drywall, insulation, etc.) from becoming ignited and burning your house down.

By breaking the box, you’ve destroyed its primary purpose and have created a potential fire hazard.

You really should fix this asap.

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For more room, in most setups you can add a “collar” to the faceplate that will lift it up a small amount above the wall surface. These are widely available and should meet safety codes.

Here is just one example:

But the Aeotec nano is quite small and does fit most backboxes.

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You are right, this does not apply to all cases.
In my case, don’t worry, the wall is made of brick, cement and plaster. There is no near of wood, fiber …
I delete the post, it is not suitable as advice
Thank you

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Just an extension of my original problem, the nano switch solves the need for sure in one side of my house but on the other it’s a 3 way switch (3 switches, 1 (set of) lights)

Im looking now at the nano dual switch, and I’m trying to work out if that will work in a 3 way setup (or indeed if the single switch would, but I dont think it will). For simplicity I drew the following diagram, with standard SPDT light switches and an intermediate switch as is standard in this setup, and a dual nano switch at the bottom with the switch ports S1 and S2 and output ports OUT1 and OUT2 (other ports abs cables not shown for simplicity, ditto Earth cables)

Obviously without the nano switch L1 on the SPDT switch connect to L1 on the intermediate and the same for L2-L2

In this scenario, if S1 was live (S2 off) would OUT1 become live (OUT2 off), and if S2 because live (and thus S1 drops) does OUT2 become live instead of OUT1? Is it just a soft configuration what S1 and S2 do? I can’t find any good guides on how the nano switches present themselves to ST (as S1 and S2 sensors and OUT1 and OUT2 switches, or are S1 and S2 hidden from ST?

Or in short can the dual nano switch replicate/mirror an SPDT switch properly?

Note that I can’t easily change the cables here as they are in the walls so I only have the wires that exist to work with. Also note that I have neutral in my wall switches (unusually) so I can fit it behind a switch plate.



The Aeotec manuals have wiring diagrams in them, take a look at those.

The short answer is that you can definitely set up what in the UK is normally called a “2 way“ ( One light fitting, two switches that can control it). It just depends on the specific wiring pattern, but they have different ones in the manual.

In the US, the same pattern is called a “3-way,” btw.

If you talk to Vesternet or any other European supplier, be sure you make clear how many switches you are talking about, as if you just say “three-way“ you are presenting them with a very different problem than your actual use case.

Thanks for the tip. I’ve just emailed vesternet as their wiring diagrams confused the hell out of me but they seem to be pretty good on implementation tips

The thing I can’t find out is how S1/S2 are represented to Smartthings (can I see their state?) and whether OUT1 and OUT2 are presented as two switches to Smartthings

If I can see all that in Smartthings I can make it work - the electrical bit I am ok with, it’s the behaviour of the nano switches I’m not sure about (and it doesn’t seem to be documented, their manuals have wiring diagrams inclusion/exclusion instructions)



I don’t quite understand the question.

With the Aeotec, S1 and S2 are wires in from dumb external switches. O1 and O2 are wires out to separate lamps.

When using a composite DTH, a smart device with two endpoints like the Aeotec Dual will show up on the device list in one of two ways:

  1. Master device with two child devices.
  2. or just two devices.

In either case, the two switches are shown as on or off in the SmartThings app. There’s no attempt to separately display the various wire branches. Or to display the switches and lamps separately.

In other words, the app displays it from the typical person’s point of view, not as an electrician’s diagram. You walk into a room. It has two switches that each control a different light. The app shows you two devices, each with a lamp icon.

I can’t see well enough to comment on your wiring diagram, hopefully others who are using this device will be able to say more.

Sorry about that diagram, all I had was some paper and a phone camera. And my description was awful.

The point I was aiming at (taking all the other electrical detail out) was that I need an mains input on S1 to turn on mains output from OUT1, and an mains input on S2 to turn on mains output from OUT2.

That my minimum for this to work.


  • I can turn on OUT1 and OUT2 from Smartthings (I’m sure I can)

  • I can see if S1 and S2 are “on” from Smartthings (less sure I can) - making the assumption that there does not have to be a direct correlation between the S and OUT ports, otherwise this is irrelevant as OUT1 and OUT2 status serves the same purpose.

Neither of these are critical but would make it a better experience for the wife



And other thing that is critical - and again I’m sure it will - when I turn off S1 (remove the mains input from it), OUT1 turns off in response (either automatically or programmatically)

I don’t doubt I’m overthinking this but I’m hanging a lot of other projects on the back of this working, and I have a box of smart devices I don’t use any more that had shortcomings I had assumed wouldn’t occur, and I’m trying to avoid more of them!

I’m not sure whether you’re underthinking it or overthinking it, but you need to read the manual.

There are parameters that can be configured to determine whether changing the wall switch connected to one of the two switch ports will change what happens with the loads connected to the output ports or instead just send a radio message to specified devices or do both. So this is configurable.

Sound like it’s going to work fine.

I can’t find a manual anywhere about expected behaviour and settings like that. I have the user manual but that explains installation and setting all the different input voltage and input switch soft options.

I have also emailed aeotec to see if they can supply the info-I’ll triple check the site to check I’m not being stupid.

Only slightly related but I thought you might know whether OTA updates will be available to zwave aeotec kit from Smartthings hubs after this new commitment of working together recently, or is a usb zwave stick and a laptop still required to apply updates? And if it is possible, any idea whether Popp kit is the same as aeotec own them?

At the present time, smartthings hub firmware does not allow for over the air zwave updates, but they have said they are working on it, and I would expect that to be something that Aeotec would want. Not here yet, though.

On the manual, it sounds like you are looking at the setup guide, not the manual. What you want is something that shows the “parameter configurations.“

Ah thanks, I was reading the same document but without the last appendix of parameters!

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