House renovation, how to a good electrical system oriented to MySensors?



  • Hi,

    my name is Bruno and i write from Italy.

    I'm in process to renovate an old three floors farm house that currently not have electrical system.

    From your experience is more best to have a main electrical box at ground floor for example, and from here starts directly with the lights lines, power line and with the 12V lines (arduino power source) for every floor with some PBCs relays inside, or to have one electrical box on every floor with the same lines?

    it's a stupid idea think to have only 12V/5V lines inside the wall switch for power the arduino+wifi or to not have completely the wall switch?

    Many thanks for every suggestions.


  • Hardware Contributor

    Its a hard question. I wish many times I had power for Arduino in every wall but that would also cost a lost of money.



  • @sundberg84 said:

    Its a hard question. I wish many times I had power for Arduino in every wall but that would also cost a lost of money.

    That would cost most people a lot of money, especially to retrofit, but he is remodeling / adding electric anyway, so it's just a matter of pulling another small wire or two. And then he would be saving on power supplies for each and every node (he would only need one central power supply / step down transformer in the basement), won't have to worry about batteries, etc...

    What are the building codes in your area however with regards to having low voltage wiring along in the same conduits as your mains wiring? I'm guessing it would need to be run separately in parallel. Is conduit required inside walls or can you run just insulated wire (especially for the low voltage)? These questions are what is going to determine your cost.



  • @TRS-80 said:

    And then he would be saving on power supplies for each and every node (he would only need one central power supply / step down transformer in the basement)

    Energy efficient wise it would be even interesting to run 12/24V through the house and step that down on the sensors. He could run led-lights etc. directly from this power source.
    Its much more efficient to use one big transformer to do the 230V AC -> DC conversion instead 10-20 small transformers all over the place. (Think: Sensors, USB-Charger, LED-Lights, different other small gadgets)

    If a solar panel is planned for his house he could even source the DC directly from it instead of doing the costly 230V AC transform.



  • I'd always thought Id wire my house with Ethernet to everything. An old boss did with his house when he moved in. Everything had an Ethernet connection. doorbell, sinks, bath.. everything..

    You could then perhaps power sensors over PoE. I think standard Power Over Ethernet voltage is maybe like 44v but you could just inject it yourself for your own sensor network and adapt the sensors accordingly at the other end. Ideally all the ports would go back to a central location and be patchable so you could swap ports quickly.

    https://en.wikipedia.org/wiki/Power_over_Ethernet



  • @Oitzu said:

    Energy efficient wise it would be even interesting to run 12/24V through the house and step that down on the sensors. He could run led-lights etc. directly from this power source.
    Its much more efficient to use one big transformer to do the 230V AC -> DC conversion instead 10-20 small transformers all over the place. (Think: Sensors, USB-Charger, LED-Lights, different other small gadgets)

    As someone who is in the planning phases of installing some HA connected, controlled LED task and accent light strips, I find this interesting, as getting control there is one thing (easily done by MySensors over RF) but you still need to power the actual LEDs separately somehow. Also any other low voltage DC loads such as small motors, servos (for blinds), etc. It would be so handy and clean looking (hidden) installation if you had a separate, parallel system of DC running through the house. Even if you didn't run wire for every eventuality, as long as you had some of that secondary system running between the floors, attic, and/or crawlspace, you could always tie back into it later. And if your secondary low voltage system eventually grew to the point where it was necessary, you just upgrade the one central transformer / power supply to a larger unit. The more I think about it, I really like this idea, for those who have the luxury of implementing it!

    EDIT: Just make sure you run your "trunk" wires (or perhaps, all wires?) a little larger than you think you will need (current/amperage wise), in order to allow plenty of capacity/flexibility for future expansion.

    The thing is, how far can you go with DC? IIRC, wasn't AC chosen over DC as mains supply, due to it's more efficient transmissions over longer distances? Or are the distances we are talking about inside a house not significant enough to worry about transmission loss?

    But man, you could have like, USB outlets all over the place, too. You would only need a small step down from 12 to 5v in the USB "outlet." Plug in your device anywhere and charge it. Run/charge small low voltage DC devices off inexpensive USB wires anywhere. Like take an old Android tablet and re-purpose it as a digital picture frame, things like that (personally, in the "system of my dreams" I plan to eventually re-purpose old phones and tablets into room specific, in wall touch master controls (controlling light, zone temp, zone music, etc. for each room).

    This is a good topic to think about, in the event any of us may be in a similar boat one day where we completely renovate a place, or build from new.


  • Hardware Contributor

    @Qu3Uk said:

    I'd always thought Id wire my house with Ethernet to everything. An old boss did with his house when he moved in. Everything had an Ethernet connection. doorbell, sinks, bath.. everything..

    You could then perhaps power sensors over PoE. I think standard Power Over Ethernet voltage is maybe like 44v but you could just inject it yourself for your own sensor network and adapt the sensors accordingly at the other end. Ideally all the ports would go back to a central location and be patchable so you could swap ports quickly.

    https://en.wikipedia.org/wiki/Power_over_Ethernet

    Might be going of topic here now... but

    Whats good to know here is that you have a voltage drop in Ethernetcables/PoE. Normal PoE are powered with 48v and then your nodes convert it to whatever it needs. If you have an injector (and be safe with correct voltage) you need to inject a higher voltage and have a converter in the end. I had this problem with a 12v IpCam - it didnt work to inject just 12 V so i had to inject 18v and have a 18-12v -> 12v converter. Here is a great resource for that: Cheap power over ethernet

    But I agree with the enternet! Its a great resource and I have also ran ethernet cables along when I have remodeled at home.



  • Hi,

    many thanks for all your replies and sorry for my english!

    I think that one ethernet cable for every switch is too much voluminous because the house have three floor of 90mq/968sqft, and with only 15 switchs/floor i will have 45 ethernet cables.

    After all your suggestions and internet search i think to start with four corrugated (diameter 25mm/1inch) from the main box at ground floor for every floor:

    • one for 5V (arduinos and USBs in the outlet)
    • one for 12V light lines with common ground (big size cable for the ground from central box to a little box at every floor)
    • one for 220 V outlet
    • one for ethernet cables (centralized wifi)

    As power supplies i plan to use two like that one (one for 5V and one for 12V), that not have fan and have protection for short circuit, overload, overtemperature, etc
    http://media.it-tronics.de/Datasheets/Power_Supplies/MeanWell/DR-120.pdf

    3D print some of this DIN clip for the lights PCB relay:
    https://www.thingiverse.com/thing:866856

    And light lamps somethings like that:
    http://www.amazon.it/Lampadina-Officina-Pannello-Fotovoltaico-Solare/dp/B00TOCJC5E?ie=UTF8&redirect=true&ref_=s9_simh_gw_p201_d0_i1

    For the WiFi AP a used Cisco POE Switch 10/100.

    For the law is possible to run the DC line in a separate corrugated, and also i want to cover the actual brick walls with a low profile drywall on all perimeters with insulation, and electrical/ethernet corrugated inside.

    I try to find the max length that i can use for 12V and 5V cables without loosing too much V and in future for sure i want to install solar panels.

    It's good?

    Thanks!


  • Mod

    Common household electrical cables are 12 AWG, which is rated for 20 amps maximum. That means you can use a maximum of 240W at 12V. It is recommended that you don't exceed 80% load, which is 16A/192W.

    12AWG has a resistance of 0.00521 ohm per meter. If you have 100m cable (which can happen easily in a house, remember that you need to calculate the distance to the lamp/whatever and back) you will have a resistance of 0.5 ohm in the cable. At 16A you will loose 16*0.5=8V on the way from the central to the lamp, so your 12V are suddenly only 4V.

    So I'd say 12V is useless for powering anything over approximately 10W. With low voltage, transfer losses are simply too high. So the difference is not AC vs DC, it is 12V vs 110/240V. An that's why the long-distance lines (both AC and DC) use several hundred thousand volts. And that's why we're beginning to see 24V led strips instead of 12V.



  • Many thanks!

    So the best solution is 12V for arduinos and for other thinghs the 220V line, or 12V line for arduinos with 24V line for lightings with one power supply for every floor and 220V line for outlet, correct?

    Thanks



  • This post is deleted!


  • @mfalkvidd said:

    Common household electrical cables are 12 AWG, which is rated for 20 amps maximum. That means you can use a maximum of 240W at 12V. It is recommended that you don't exceed 80% load, which is 16A/192W.

    Yes but in the U.S. that is 20 Amps @ 110V = 2,200 W.

    Which kind of throws all the rest of your calculations off a bit. πŸ™‚

    Also, OP is in Italy, my understanding is mains in Europe are like ~220 or whatever. I'm not sure if that comes on one leg or not (in the U.S. we also have 220V circuits for larger loads like dryers and pumps, but we get the 220 by putting 2 legs of 110 together). So I have no idea what the average size house wires are in Europe...

    At any rate, some additional careful and knowledgeable planning definitely should be done. This is doable, but not something you want to rush into without proper planning...


  • Mod

    @TRS-80 said:

    Yes but in the U.S. that is 20 Amps @ 110V = 2,200 W.

    Which kind of throws all the rest of your calculations off a bit. πŸ™‚

    Yes. If you use regular voltage, you will of course get regular wattage. But that's not what this thread is about, unless I misunderstood the OP's question about running on 5/12V.



  • @mfalkvidd said:

    Yes. If you use regular voltage, you will of course get regular wattage. But that's not what this thread is about, unless I misunderstood the OP's question about running on 5/12V.

    What I meant was, when you say that 12AWG is usually good for 20 Amps, that is in a home circuit which assumes 110V.

    However, if you are only running 12V, couldn't you run more Amps? Or is wire sizing strictly based on amperage?


  • Mod

    @TRS-80 yes it is only based on amperage. In Sweden, where we have 230V mains the same cable can be used to transfer 20*230=4600W.

    http://www.homedepot.com/c/factors_to_consider_when_wiring_your_home_HT_BG_EL H has some information on cable selection.


  • Admin

    It's a bit complicated. The problem is that the lower the voltage, the higher the amperage is needed to be, to keep the same output wattage on the string.

    if you are not running sufficient wiring on the low voltage bus, you'll get into troubles with voltage drops across the wires (ohms law). And THAT would also lead to heat dissipation on those wires (Again, ohms law)

    Power dissipation on the wires would be something like : (IΒ²)*R = P. Where I = total current drawn, R = wire resistance, and P = Watt dissipated.



  • Interesting conversation. I can't help but throw a fly in the ointment, as they say. Have you calculated the cost of all this additional infrastructure? Wouldn't it make more sense if you are going to this level of implementation, to go with a standard system like zWave/ZigBee modules, or something else on the open market? It's plug and play into any existing standard home electrical infrastructure. In addition, they are all fully certified products for home use and limit your risk of liability should you have an electrical fire or anything else that could be attributed to your self built system.

    Don't get me wrong, I like MySensors and am using some point solutions that make sense for me. I myself have contemplated putting in a full blown MySensors environment for control of devices, but I'm having a hard time justifying the costs and risk in doing so. In addition, I won't plan on staying in my house forever, so the potential resale could be more difficult with a non standard infrastructure.

    Just some thoughts to consider. Would love to hear some additional ideas on the topic.



  • The house at the moment is completely without the electrical system, so for me the price, at the end, will be the same of a traditional system.
    Also today i decided to not use a drywall with electrical pipes inside, but to use external electrical system like this just for idea:

    alt text

    So all is more easy (installation, maintenance and price).

    I think to never resell this house in future, but if this will happen i can convert it to a traditional system in a relatively easy way.

    It's true that is more simple and secure to use a commercial system, but in this way i will loose the taste to realize the whole system πŸ™‚

    @TRS-80 : In Italy we have 220V mono-phase for civil installation and 380V tri-phase for civil/industrial installation (usually for industrial machine or for a farm like mine).
    And wire size usally are 1,5mm for lights (10A) and 2,5mm for sockets (16A).


 

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