2023-01-17, 10:30 AM
First of all, I want to thank all the members of this forum, - specially SAILOOG- for their contributions throughout the development of the OP project.
I am currently working on a version of the “digitise an older engine” project that suits my needs (VP 2003T with temperature and RPM gauges), and I have tried the following modifications:
In addition to the exhaust temperature, I have installed a second DS18B20 probe with "one wire" to measure the turbo temperature.
Since I already have a BM280 installed in OP2 for the barometer, I was not interested in putting another one in the ESP32. Consequently, I measure engine room temperature with a third DS18B20 inside the ESP32 box (this one in TO92 format).
So, “One wire” controls all three temperatures, and I have removed the BM280 library and dependencies from the program.
For the temperature of the cooling liquid, I have changed the way of measuring:
Instead of measuring the resistance of the Thermistor, I take the voltage of the signal that already goes to the temperature indicator (which is sufficiently linear in the range 60 – 100 ºC) and I condition it with a divider in order to not exceed 3V3 in GPIO. With this, only one “linear transform” code line is necessary to generate the temperature in ºK. (Instead of calculating resistance and interpolating in data curve). Offset and multiplier coefficients are experimental to match with temp. gauge readings.
For the RPM indicator, I am also going to try a somewhat different circuit, incorporating a "buffer" of the "W" signal, to avoid that the current needed by the photodiode can interfere with the proper functioning of the RPM gauge. (I'll send another post when I've tried it)
By the way; Notifications and alarms in SignalK, and plugin in OP work pretty well to warn in any temperature deviation from expected temp. Also in KIP pages.
I am currently working on a version of the “digitise an older engine” project that suits my needs (VP 2003T with temperature and RPM gauges), and I have tried the following modifications:
In addition to the exhaust temperature, I have installed a second DS18B20 probe with "one wire" to measure the turbo temperature.
Since I already have a BM280 installed in OP2 for the barometer, I was not interested in putting another one in the ESP32. Consequently, I measure engine room temperature with a third DS18B20 inside the ESP32 box (this one in TO92 format).
So, “One wire” controls all three temperatures, and I have removed the BM280 library and dependencies from the program.
For the temperature of the cooling liquid, I have changed the way of measuring:
Instead of measuring the resistance of the Thermistor, I take the voltage of the signal that already goes to the temperature indicator (which is sufficiently linear in the range 60 – 100 ºC) and I condition it with a divider in order to not exceed 3V3 in GPIO. With this, only one “linear transform” code line is necessary to generate the temperature in ºK. (Instead of calculating resistance and interpolating in data curve). Offset and multiplier coefficients are experimental to match with temp. gauge readings.
For the RPM indicator, I am also going to try a somewhat different circuit, incorporating a "buffer" of the "W" signal, to avoid that the current needed by the photodiode can interfere with the proper functioning of the RPM gauge. (I'll send another post when I've tried it)
By the way; Notifications and alarms in SignalK, and plugin in OP work pretty well to warn in any temperature deviation from expected temp. Also in KIP pages.