Hi all,
I’m a newbie, but I’ve really studied all the books. I would like to create a home automation system for my 34 foot Fifth wheel which is my full time home. I have both 12 volt and 24 volt sources. I believe I could power the ESP 32 or 8266s board with the 12 volts going to the voltage regulator, however it would make sense to power the relays also with the same 12 volt source. I believe that would negate the circuit isolation. Does it matter? Would it help if I used a Mosfet as the switch instead of a mechanical relay board?
Thanks for your help.
Steve

Pretty sure we had the same question a few days ago. From my recollection you should be fine as the voltage regulator on most ESP32 dev boards can handle 12V fine. You should check, however, whether a heatsink should be used on said regulator.
 
My thoughts would be to isolate as much as possible. Even though a 5th wheel runs on 12/24V it’s not the voltage that kills you – it’s the current. If you’ve ever felt a small jolt when opening a car door etc then that is 50,000V+ but negligible current.
 
I used to live full time in a luxury 37 foot 5th wheel myself.