Above is an image of a CAN bus node. This is an Arduino with a CAN bus shield and on top of that is a DIY shield, which connects to the OneWire bus, the relay board for the gate valve and the analogue input for the tank senders. This is what I have used for testing so far.

I have added the current sensor below and used it to determine if the gate valve is moving (current draw of the motor or running against the end when open) because the open signal comes already when the gate is open a bit and not when it is open fully.
I will use the same technique to verify if a power consumer is actually using some power when it was switched on to determine
that it is actually alive. This is a bit like the check of the light bulbs work on a car. A decent car tells you when a light is not
working. My truck does not but I will add a sensor like this to the main lights. The Merc does that standard and it is really handy not to have to run around the car to check if the lights work, especially the trailer lights. This will be added to the trailer lights too, so I will know that they are working. I finished the program functions to determine the actual current, however the version I have is for 30A so the resolution is quite low. I have also ordered some 5A ones, which are better suited for the lower currents like the valves and the normal lights on the van.

I have also tested my 240V current sensors (they are non invasive hall effect transducers) and allow me to measure total current in the various 240 circuits and switch off some circuits if load gets too high. I have latching relays in the main 240V supplies for the secondary circuits with NC contacts (normally closed), so it only needs only a momentary connection to 12V to disconnect that contactor and the 240V circuit goes dead. Same applies to the main supply. My emergency button will simply trigger the contactor to open and all 240V is disconnected, pretty simple really.

current_sensor

I have experimented a bit with the analogue inputs of the Arduino and came to the conclusion that I will use a precision
reference voltage for the Arduinos (use an LM4040diz as a reference voltage source) and that each Arduino gets a little DC-DC step down power supply for exact 12V. This avoids any fluctuations in supply voltage and all my readings are more precise and repeatable, otherwise the analogue inputs will vary depending in supply voltage. Not really a good idea to allow that.
The little DC-DC units are cheap enough to warrant that.

Tomorrow I will be cutting again. I have to get going that everything is ready for Friday. My mate has dropped off the gas bottle and his Mig welder. We will do everything in Mig not Tig.