I sketched out my main installation in my project vehicle. To summarize, it runs with isolated DC converters, one gets the input from main battery (standard 12V lead acid) and converts it to clean stable 12V. This 12V is used on a high side switch that switches 2 loads. Another buck converter is 12 to 5V one, since stable clean 5V is needed for the three microcontrollers.
My problem is I'm not sure what would be the proper way to ground this setup. The load1 and load2 will most likely be grounded to chassis ground. But the Arduino 1 will use 3 buttons for typical logic level function of buttons. Where would be the best practice to ground these buttons, 5V buck converter's -Vout ?
Also - the 3 cables carrying the pin signal from Arduino will have to be at least 5 feet long, I presume shielding would be advised because of interferences of the engine and such?
Thanks for any help