AC Power and/or Relay interface



  • I am looking for a way to put an MySensors Relay actuator behind a wall switch. I read a lot of information provided here (special thanks goes to @sundberg84 for all his research and sharing his findings and results) and also studied some power supply designs found on the web (Openhardware.io and also some commercial products).

    I learned a lot and feel like I demystified the architecture of power supplies a bit, so that I am now a lot more comfortable with AC mains electronics in theory. I think the recommended design for Safe In-Wall AC to DC transformers is safe enough to use and as far as I have seen it is even more secure (at least by design, schematic is another topic) than a lot of commercial products out there.

    But nevertheless I am still concerned because of missing certifications and the fact that assurances might decline to pay in case of an accident. That's why I am currently looking for another solution. My dream solution would be something that deals with everything AC related and provides an low voltage output (as well as an digital input for controlling an embedded relay).
    I am pretty sure there is nothing like that, but asking doesn't hurt.

    I also like the Sonoff devices. I'd consider them also, if they would be using an Atmega instead of an ESP8266 and if they were smaller in size. But on the other hand using a custom software would again break the certification...
    Also the Livolo switches are nice for tinkering, but missing an interface I could use, I think this is also not a solution for the certification issue.

    Maybe here is somebody who has seen something like that or who has another suggestion.


  • Mod

    What's the problem with esp8266? If you want really small relays you need to look at zwave products



  • @gohan There is no problem. I like the devices very much, but I'd like to have something not WiFi based for that purpose.

    Why Z-Wave? Do you know a Z-Wave device, that serves low voltage output and is externally controllable?



  • You can find that in any electronic shop, it is called phone charger or just 5v power supply. If You want to put it behind the wall switch You have to search for flush mounted power supply, but it is hard to find realy small one that will fit with another device.



  • @rozpruwacz Thank you for your suggestion. I already searched for that for hours (if not days). Most results are either uncased (so not certified) or/and quite expensive.
    The best thing I could find was the Recom RAC03. But the price (and again the missing certification, not sure) make it not suitable.



  • @exilit said in AC Power and/or Relay interface:

    Recom RAC03

    I'm no expert in consumer electronics certification but i think that this is the same as HLK module. I'm talking about something like this:
    https://ealarmy.com.pl/produkt-4167/psc12015-12v-15a-62mm-zasilacz-impulsowy-hermetyczny-ip67-pulsar?gclid=Cj0KCQjwierMBRCHARIsAHl9i4G8b3ruKpyNMhiZV7nL7iWaJ4oatzqpXHaiDZJeQOPKOxElJeeoS9oaAvwjEALw_wcB



  • @rozpruwacz Wow, that looks great. Still missing the relay for my dream product :-) but that's a starting point. Do you know more of that? Like I said, I searched that for days and didn't find anything similar.



  • @exilit said in AC Power and/or Relay interface:

    Recom RAC03

    oh, You are talking about this ?
    https://www.digikey.com/product-detail/en/recom-power/RAC03-05SCR-277/945-1702-ND/3844914

    if so then yes this is exactly what I mean and actualy this item looks very good :) about the price I believe that maybe you could find something half the price but not less ...


  • Mod

    http://www.widom.it/it/universal-relay-switch I think this could be an option



  • @gohan Thanks, but I believe Z-Wave will be expensive. And apart that I would really like to run MySensors (Not mandatory, but currently my goal).



  • @exilit said in AC Power and/or Relay interface:

    like to run

    from my personal experience: more You do yourself the cheaper unit price but You spent on it more time - so You have to calculate how much Your time costs.
    The other issue with making something to fit into wall switch is that it has to be small, so this requires more custom design -> so more made by yourself -> then it won't be certified. Or You choose small but very expensive parts.
    Personally I wouldn't buy cheap power supply, this is the most important part of the device.

    So if You have good knowledge how to design safe power supply just do this and don't worry about certification, If You design it well then it will not cause your home tu burn :)



  • other solution would be, considering that there are thick cables in the walls to handle large currents, to run only low DC voltage instead of high AC voltage for the lighting, but it would require to use low voltage (12V DC) led lights everywhere. And this might be a problem, because there is very little bulbs operating on 12V DC axept of led strips and some halogen replacement bulbs.



  • @rozpruwacz said in AC Power and/or Relay interface:

    If You design it well then it will not cause your home tu burn

    :-) Yes you are most probably right. But if it does, I will not only lose my house, I will also be bankrupt and homeless.

    But seriously: This is what I was thinking for some time also. Especially because I have seen In-Wall device that are way unsafer than the ones on this forum using the HLK. But for some reason I'm very unsure for the last few days...
    So if there is another solution I think I still would like to take that. If not... well, I will do it myself and hope that my house does not burn. Maybe I put a CE sticker on it... :-D


  • Mod

    You wanted small device that is also certified and the smallest solution I know are Zwave devices. I don't think you can find a certified product running on atmega controller with mysensors and be also certified



  • @gohan I know the requirements are very specific and hard to find. I am just searching for ideas.


  • Mod

    It is just a matter of choosing commercial or DIY, that means certified or not certified :)



  • @rozpruwacz said in AC Power and/or Relay interface:

    @exilit said in AC Power and/or Relay interface:

    Recom RAC03

    oh, You are talking about this ?
    https://www.digikey.com/product-detail/en/recom-power/RAC03-05SCR-277/945-1702-ND/3844914

    if so then yes this is exactly what I mean and actualy this item looks very good :) about the price I believe that maybe you could find something half the price but not less ...

    Yes, that is what I was talking about. Half the price sounds good.
    But to be honest, I think the one you posted suits it better. The Recom power supply's use cases seem to be the same as the HLK module.



  • @exilit the one i posted is much bigger and 12v, so You need buck converter. This makes it harder to fit atmega board, but maybe You will :). for sure there is more 12v flush mounted power supplies and they are cheaper because they are used for led lighting. The cheaper ones will propably draw more power, they will be powered 24/7 so it is important that they draw at lest less than 0.5W.



  • @exilit what voltage are you needing?



  • @Black-Cat Ideally 5V or 3.3V. But in the end it doesn't matter too much, as converting it down wouldn't be too difficult. Do you know something?


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