Arduino with an ethernet shield and 2 analogue LM35 sensors.
I used some copper pipe to make better thermal contact with the radiator and engine block, and also to provide a place to mount the sensors. One went onto the outside of the engine block and one on top of the radiator (couldn’t find a better place). The radiator sensor consistently measures about 5 degrees hotter than the one on the engine block.
Copper pipe banged flat at the end with a hole drilled for the temperature sensor: very neat. Did you put any paste or anything in the pipe to improve the thermal connection to the sensor?
What are the black cuboids on the strip board, relays for the fan and engine cutoff? I assume by “generator safety unit” you mean something to stop the engine if it’s getting too hot?
I should probably have used some paste, but couldn’t be asked
I’ve checked the temperature of the engine block vs. that reported by the sensors, and it was within 1 degree, so good enough.
The cuboids are low voltage/power signal relays, 5V which can be driven directly from the Arduino’s pin outs. One of them is used to drive the remove switch functionality of the generator control unit (DeepSea 3110), i.e. to turn it on or off.
The other relay is to turn the radiator fan on and off, but that relays is used to drive a second automotive relay which can handle the current. There’s a third relay there, which is the solid state relay for switching the 80W extractor fan and of off, but I’ve not connected it yet.
Yep the “Safety unit” part is exactly as you suspect: turn the engine off if there’s over temperatue in either the radiator or engine block sensor.
Thanks for the extra notes.