ray_sabado - We have a generator that only has ...
We have a generator that only has shutdown sensors for exhaust temp, water temp, and oil pressure. What is the easiest way to get actual values for those parameters into Signalk?
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presumably the various sensors are being “read” by an ECU … which makes a determination to “shutdown” the engine .
from my experience, exhaust temp is often a “switch” (rather than an analog sensor), the other two of course are analog senders.
if so, then there is no benefit in monitoring this (its either ok, or over temp and generator shutsdown).. however if its a true thermocouple sensor .. then yes monitoring it can be useful. (of course you could also add an EGT sensor into exhaust system)
you didnt mention if the gen has guages? analog? digital? display of oil press and water temp.
if yes, then you can likely “sniff” the votage across the guages and with AtoD read them into SK. (&apply calibration factor etc)
however if it doesnt have guages ..
effectively you need to connect monitoring in paralell with existing sensors (ensuring you dont upset the monitoring done by ECU) .. as you still want it to operate correctly.
OR
in some instances i have added a second temp sender (eg i had a water pump that had a spare “port” in its housing that i was able to insert a second temperature sensor.. thus avoiding using original).
the senders are usually just a “variable resistive sender “ … that of course has a bias voltage applied by ECU …. so in effect you “sniff” in parallel, ie measure the voltage across sender.
of course if you have a engine manual that shows wiring diagram and details … this helps enormously .
..otherwise its a multimeter and quite a bit of messing around measuring …
To get “analog” signals into SK there are various methods …. commercial and DIY…
but you need to answer the above questions first, to understand what type of signals you are dealing with.
All of the sensors are actually just switches. They are either NO or NC and simply trip the fuel solenoid if they change.
There are no gauges of any kind for the generator.
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It shuts off with a generic error that doesn't say why it shut off. Additionally, just like tracking anything, it can help see trends so I can actually address an issue before it becomes a problem.
"exhaust temperature is getting higher than normal so I should check for clogged raw water inlet or impeller issues". I would much rather deal with that before the generator shuts down when we are in the middle of charging, cooking, etc.
ok, so you simply want to monitor three digital inputs and read the state into SK.
there are numerous ways to achieve this.
1) SK Rpi - if its close enough and you can run wires, you can use rpi GPIO (with appropriate buffer between the switches and GPIOs… eg a relay, or opto coupler etc)
2) if you have a victron device like cerbo, it has digital IO
3) commercially available N2K digital switching unit
4) wirelessly … ESP32 or similar.
sensESP is a good place to start.
.. im surebthere are many other ways, these are just some that i have used.
.. like the above post however, reading the switches will tell you the reason is shutdown …. however
thats not really ”preventive” … its certainly “investigative”
… but i would prefer to know inhad a problem BEFORE the generator takes the extreme decision to shutdown.
eg if you rely on EGT over temp switch .. by that time the engine has run hot for a while … not good.
depending on how mechanical you are …
i would be investigating if you can fit actual analog sensors in “parallel” with the “switches”.
particularly for engine oil pressure and coolant temperature… these are the critical two for preventative purposes.