ray_sabado - We are adding three sensors to our...
We are adding three sensors to our generator. Oil pressure, water temperature, and exhaust temperature. The sensors are meant to connect to the factory wiring harness then into factory gauges on the control panel.
Because we didn't opt for the gauge package, our control panel does not have the analog gauges just unterminated wires.
I think a ESP32 is what I would use to read that data and then send it to Signalk. Is that correct?
If so, can someone please point me in the right direction on learning how to do this?
Thank you very much!
6 Replies
The analog guages would typically respond to output voltage.
So you would expect to read a voltage between each of the “unterminated” wires (& ground) .
Yes an ESP can be used for this, note however the ESP has a max Voltage of 3.3V on its analog pins,
AND it gets very non linear when you measure above ~3.0V ; accordingly you need to scale the voltage using a voltage divider, to ensure it NEVER exceeds 3.3V (on the ESP32 input pins) .. and ideally
in normal operation is <3.0V
you can use sensESP - which makes setting up the ESP and publishing data to signalk server easier .
The challenge is that you need to identify the “calibration” that will be required, to translate the raw voltage vs temperature reading (that would normally power the analog guage)
so that along with the resistor volt divider (to keep input to ESP <3.0V) you get a correct computed temperature reading that is sent to signalk server path.
there are variius commercial solutions available, however based on your “ESP32 point me in a direction” .. its assumed you want a DIY solution, hence
As far as “pointing you” in corect direction
- sensESP documentation (includes examples)
- ESP32 documents for details on ESP32 analog in Pins etc.
this is very useful for details on the ESP GPIO pins, and also has details on the ADC linearity that i mention above.
https://randomnerdtutorials.com/esp32-adc-analog-read-arduino-ide/
not sure you electronics knowledge… do you understand “resistive voltage dividers”?
sensESP has a bit of a learning curve, but plenty of help here, and good examples at https://github.com/SignalK/SensESP also to note, you can use a module such as INA219 to measure the voltage of the unterninated guage wires, this obviates the need to use resistive voltage dividers, and also offers much better protection for the ESP inputs.. you would need one INA219 module for each item your measuring. (INA219 assumes you boat is a 12v system? … if its 24V you need to use different INA module)
sensESP has a bit of a learning curve, but plenty of help here, and good examples at https://github.com/SignalK/SensESP also to note, you can use a module such as INA219 to measure the voltage of the unterninated guage wires, this obviates the need to use resistive voltage dividers, and also offers much better protection for the ESP inputs.. you would need one INA219 module for each item your measuring. (INA219 assumes you boat is a 12v system? … if its 24V you need to use different INA module)
In addition to what @gregy said, I have measured voltage from random gauges with a multimeter, which helps figure out how to spec your voltage divider.
And if you just don't feel like soldering, something like this can be useful: https://www.amazon.com/gp/product/B01HTC4XKY/ref=ppx_yo_dt_b_search_asin_title
I'm using https://github.com/SignalK/SensESP/blob/v1/examples/ads1x15_volt_meter.cpp for several years already with great results for measuring four 12v battery banks. But keep in mind this is "v1" branch and not latest.
I use ds18b20 thermometer sensors, very useful. One on cylinder head, exhaust & alternator.
You might want to check out HALMET, it's specifically designed to monitor engines. Depends on the exhaust temp measurement whether you need a separate module for that. Are you interested in the actual exhaust gas temperature or the wet exhaust temp?
Lots of good information. As far as skill 😂 I'm am an engineer so I always think I know everything 😎. I can figure python out and I do understand basic electronics but I'm much better at fixing cabinets, resplicing halyards, changing oil, and other boat jobs so I wouldn't mind a more off the shelf solution.
I would add analog gauges but we don't easily have room for them.
I am a little concerned about calibrating the readings without having the analog gauges. I did that for our fuel and water tanks but that was much easier because I did it while filling them.
I could possibly install the analog gauges at the generator I suppose.
This looks good. For the exhaust temp, I was planning on attaching a one wire sensor to the exhaust elbow with a hose clamp.