In wall - PCB, (AC to DC 5v)

[Samuel235]

So, this is what i have to contend with. Inside the socket i need to fit an arduino, nano or mini and some form of power supply (cell battery looks the only way) an nRF24L01 and then connect it to the rear of the switch. I may have to create my own board and arduino to reduce the footprint of my design to enable it to fit. Idealy i want to keep those current wires in the box but terminated, simply so if we move house all we need to do would be to remove the terminals and rewire into the switch.

[martinhjelmare]

I've been thinking about installing a PCB with transformer in the wall myself. I like this project, but how do you feel about leaving exposed high voltage circuitry in the wall box. Normally the wires in the box should have at least one layer of insulation and splicing should be done inside insulated caps. Don't know all the correct terms in English, so I hope you understand what I mean.

Ideally I'd want a box for the PCB inside the wall box, but that will probably never fit. Right now my plan is to put a new box on the outside of the wall next to the coupling box up under the ceiling vertically ~ 120 cm from the wall box with the buttons for the lamps etc. But in my basement there are no coupling boxes under the ceiling, so there I'm forced to put everything inside the wall box, if I want it to look good.

Any other ideas?

[Samuel235]

@martinhjelmare In your case it would be high voltage open circuitry as you plan on running it on the existing power lines that are there currently. If i understand what you're saying anyway, am i correct? However, in my case, i plan on terminating the existing wires in a terminal block or taping them off if possible to save space, then have my sensor node running off of a custom PCB holding a custom made Arduino to save even more space and then run the whole board off of a cell coin battery.

[martinhjelmare]

@samuel235

My worry, when having exposed high voltage circuitry inside a standard wall box, with otherwise insulated wires, is that someone else than me, for example an electrician, might poke around unknowingly in the box and get electrocuted. If you have the PCB inside a separate box with warning label, the risk is at least slightly lower.

[Samuel235]

@martinhjelmare I would agree, with your situation, and like that proposed on this PCB design (@sundberg84, please correct me if i'm wrong), like i said in my previous post. You should either conceal them or avoid using them. That is what i would advise (using UK/British rules and regulations).

[sundberg84]

Maybe someone could open a own thread discussing this with a battery operated in wall node.
For example, someone needs to put a circiut diagram for how to operera that relay with power only from the battery.

[m26872]

I agree with @martinhjelmare I just assumed there would be some other insulation and it would be the second step of the design. Good you cleared this out early.
I think it is almost possible, but really hard, to copy the size and shape of commercial in-wall devices and still fit in all we want. Small customized PSUs may be necessary.
Personally I'd prefer external boxes. They could be in wall as well, as long as there's space for safe (diy) designs or even future projects.

[martinhjelmare]

I'm thinking I'd like to try and design a custom box for 3d printing that could fit this project by @sundberg84 and also fit inside the wall box. Has this been done already and do you think it's worthwhile, i.e. is it possible?

[sundberg84]

What I know of, this has not been done before... not the PCB or the 3d printing.
Good points taken above! We need to consider this and this might not be the optimal design.
Maybe thought was that this design can break some ground and maybe it can lead to better and even smaller designs.

I like my designs easy :) Pro Minis with ready bootloaders so everyone can be inluded, but this might not be possible...
I will still finish my design and see how it looks.

[yancym]

Hey everyone. Been following this as I'm very interested in having this functionality with the Arduino's. I'm a newbie and have very limited knowledge with anything electrical, so forgive my ignorance. How is this problem any different than what the X10/ZWave/etc. solutions have already overcome years ago? I have an X10 wall socket that does very similar switching on/off of one socket. All the components are built inside the socket, putting the control components and the high voltage very close together. The wall switches are another example. They always have some current running thru them even when the light is switched off, to detect the signal. Again, forgive my lack of understanding how all this works, but it seems like this may not be as big of an issue as I'm reading here. Thanks.

[Samuel235]

Some awesome input here for @sundberg84's project! I would love to see your designs completed whether or not they suit other people's situations dude. Once you have completed yours then we can build from your base to create another product that would suit others. Note i said build ANOTHER product, not upgrade yours. Your's would be widely used by others, just not the ones that need it inside of a UK Sized box maybe. So, most importantly, lets help develop yours and help test it if needed.

I'm going to be doing some basic designs on getting a battery powered one installed into a UK socket as my next major development in my network, so we might have a starting point by the time yours is nearing completion.

If you need any input/help/testing just give us a shout ;)

[martinhjelmare]

I started a new thread for my attempt at a custom box design.
http://forum.mysensors.org/topic/2509/box-for-in-wall-pcb

[Samuel235]

I have also started my own thread to save me clogging your development thread up @sundberg84. I'm hoping that we can gather seperate ideas and then discuss to develop products that are a creation of many of opinions/improvements.

[sundberg84]

I recieved my PCB today - Yea!

The good news is - its working, and it fits inside my wall socket.
The bad news is that as always i will need another revision - the hole for the fuses are to close to each other.

Some pictures:

Anyone with any input on this?

[Samuel235]

@sundberg84 Fantastic news on receiving this before the Christmas dull in mailing! Super happy for you to receive, populate and get working your custom board dude! I have no input other than to congratulate you on a successful board, shame on the fuse issue :( Could i ask you, do you have any components sitting under your nRF module?

I'm currently having a few little teething issues on getting the board down in size slightly, it should fit my application as it is right now, but i would like it a little smaller. The thing that is really holding me back on sizing is the screw terminal being a 4 pos block. I might have to reset to maybe 2 x two pos, or even some singles. Although i only need two switches on this particular application, i would like to make it accept 3 so just in case i install a 3 way switch somewhere, i am able to use this board, rather than creating another.

Hopefully I'm not too far away from completion now.

[martinhjelmare]

Nice! Good images, and thanks for the scale. Is your wall box also 4 cm deep, like the ones I have in my house?

[Łukasz Rybak]

Hi all,
It looks very good @sundberg84, It's still a little bit bigger than fibaro switch but costs much much less :) Looking forward to see your next revision

Is it any chance to place another screw terminal to allow turn on/off not only via radio but with the local button as well?
From other side as a workaround it still should be possible to hard soldering some wires to appropriate pin on arduino side.

I'm wondering why some Asia manufacturer is not able to build a tiny pcb with integrated arduino, nrf radio, ac-dc trafo and relay on one single board to keep small footprint.

[m26872]

@sundberg84 Good job and nice fit! Looks like you can even make the discussed separate box-in-box for it if you like.
Do you have a BOM of the parts you used this far? And which ones you need to replace or move around.

[sundberg84]

@samuel235 - No components between the NRF and the PCB but yes, if you mean on the other side of the pcb. There is the 5->3.3v converter and caps.

@martinhjelmare - Yes, 4.5cm it seems but there is some room on the sides so i hope to be able to squise in a relay.

@łukasz-rybak - You can connect a local button between d3 and gnd on the MYSX connector on the right side. This can read the switch and change a relay depending on what state the switch is in.

@m26872 - Yea, lets hope so... ill do another revision of the board and lets see where this ends up.

[sundberg84]

So, my rev 3 is coming along:

• moved the Dallas temp sensor
• added some more space for the 240v fuses:
• labels changed

The BOM? Is that the parts used?
I have used what we concluded here:
http://forum.mysensors.org/topic/1607/safe-in-wall-ac-to-dc-transformers

This is what i bought (no garantees given this works/doesnt burn)

HKL-PM01 http://www.ebay.com/sch/sis.html?_nkw=HLK-PM01+AC-DC+220V+to+5V+Step-Down+Power+Supply+Module+Household+Switch+Q15274&_id=351418782712&&_trksid=p2057872.m2749.l2658
(DO NOT BUY THIS!!)Fuse http://www.ebay.com/itm/111433875797?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Thermal Fuse http://www.ebay.com/itm/221560426284?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Varistor http://www.ebay.com/itm/260848704608?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Pro Mini 5v
Nrf radio
LE33a http://www.ebay.com/itm/400691492273?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT