Power bus

[otto001]

Hi forum,

I am planning my new house right now and I am thinking about using mysensors along with fhem.
As I have the possibility to completely wire the house, I think some kind of power-bus-wire (eg CAT7) would be nice to power all the arduinos and hardware along it´s way. Im am considering to have 3.3V, 5V and 12V plus 3 x GND in that wire.
What kind of power supply would you use? I think that it will about 20 arduinos (mainly minis) within the next year...

Thanks for advice!

[tbowmo]

if you have the possibility to run wires to all your sensors, then why not make them rs485 or something similair, multidrop serial-something?

[otto001]

do you have any suggestions how to do this?
I am new to arduino stuff and dont know if fhem supports stuff like this?

[otto001]

Think, I will try with a computer power supply + regulator for 3.3v....

[tbowmo]

One advice would be to run a higher voltage around the house, and then locally have a ldo or buck converter to make your 3v3.

Let's say your entire sensor network consumes 5W, then if you run it on 3.3v the current consumption would be 1.5A. While if you run it on 20V the current will only 0.25A.

The higher amps you are running through your wires, the higher the voltage drops will become across the wires. Of course depending on wire gauge, and length of the wire.

[axillent]

you are on a right way)

take into account that long wires are always subject of the voltage drop
I will suggest you to consider a higher voltage for the bus, 12V or even 24V
and you will need step-down before each arduino to get 5V or 3.3V
there are cheap and small step-down can be purchased on ebay or ali

the advantage of the step-down comparing to linear regulator is current transformation - step-down not only drop voltage down from 12V to 5V (for example) but also decrease current on a bus side. As lower current as lower voltage drop across the bus

RS485 could be a good choice for the communication. definitely RS485 at some point will be a standard option for mysensors, and a gateway from RS485 to a controller will be also a standard option.

I personally working on a similar project. In my case power will be 48V, I will use just 3 wires, In my case 48V will source not only sensors but also LED light. This why I choose a bit higher voltage

[otto001]

Thanks for the hints :-)
Yes, RS485 would be a very interesting option, but is not implemented yet - and I am modifying my house right now. I think I will add some pins to the power wires for future use...