Measuring boat engine temperature

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 An sailboat with an old engine(Volvo Penta 2003T) is the scene, and the fear of insufficient cooling is the subject that I need an solution for.
On most modern sailboat engines, this comes out the box, or at least as a plugin, but for the good old engines like this, it simply does not exist.. yet ;)

So with an Arduino Nano 33 IoT , a 128x64 SPI display and 3 DS18B20 1-Wire temperature sensors.
I created a "peace of mind" thing.
I used the Arduino Nano 33 IoT due to it's  Wi-Fi capabilities, so that I could sit in the cockpit, steering the boat, and keep a eye on the motor temperature , when ever I wanted to.

I made this prototype in spring 2020, and tested it through the season with some minor adjustments to the web interface:


I ended up making the web interface extremely simple and color coded, so the blue means cold, green is normal operating temperature, and red is over normally temperature .

A thing some might note, is that the temperature, is way to low to be called operating temperature (~50 degree C.), this would normally be around 80 degree C.
This is due the the non-invasive way I have placed to temperature probes. the important part for me was to monitor if anything is unnormal.
I measure the temperature in 3 places:

Ferskvand (Freshwater) - the temperature of the closed freshwater circuit, this ensures me that the impeller is working and the freshwater circuit has enough coolant( no major leaks)

Saltvand (Saltwater)  - the temperature of the saltwater just before it goes to exhaust. by doing this I know if the heat exchanger works as expected, and that enough saltwater is coming in - and out.

Motor (Engine) - the engine block it self, basically this make sure that every thing else is normal.








The diagram is pretty much the same from start to now, and very simple ;) actually only one change was made, and that was to put an Alert port on the board, so external stuff could be activated in case of an fault.(i.e. light, buzzer, horn etc.)





During winter 2020 and 2021(Corona left plenty of time for projects like this), I made a prototype PCB







, and then another prototype... because without thinking I put the sensor bus pins right in front of the USB port, as seen on the pictures above, so any software updated would be impossible

A new set of PCB's has arrived, and a case is prepared:






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