I have a Solar water heating controller (Pro Solar PSR5) which I would like to use. The controller start the pump if the panel is above the temperature in the waterboiler. The temperature measurement in the boiler works fine. But because I making new solar panel the temperature measurement on the panels I have to rebuiled.
I adjusted the restistor and measured the voltage over the resistor at different temperatures. But I did not figure out what temperature depended restriction I should use. I think I need to use RTDs be non of the standards seems to come close to my measured values. Maybe I need several RTD in serie but also than I do not get 14.5 Ohm/degC and the same overall resistance.
If I get this working than I can use an Arduino to publish the temperature to MQTT and from there to Home Assistant.
Volt
Ohm
deg C
1.53
1529
20
1.81
1639
30
1.93
1721
40
2.03
2020
50
2.13
2070
60
I calculated a line : y = 14.657x + 1209.3 (R² = 0.9671)
raschemmel is seems very linear.
The display switches on leds 20, 30, 40, 50, 60 deg C.
I protected the measured data and did a linear curve fit ([Ohms] = 14.657*[deg C] + 1209.3) The R² = 0.9671 seems okay.
larryd
Thanks, indeed very interesting as soon as I have the temperature measurement working with the existing controller. You would expect that some standard RTDs used.
There one additional information I did not share....if there is no restriction installed is the voltage 6 V. With that I concluded that there should be a 3.8K restictor in the controller
I've used DS18B20s and they are a breeze to use, especially since you bus them all together because they are addressable with 16 digit hex address or something like that.
There's tons of examples on line. I prefer the Dallas Semiconductor Library.
In stalling an alternative temperature system is possible, but than I can not use the existing controller.
If someone can help me back engineering the existing probe on the solar panel would be fantastic !
Could try to sent voltage back from the Ardiona after measuring with for example DS288B20 but would preferable solve it within the existing controller and only send signal to Arduino for reporting
I found on the internet a simular controller KTY restictors. I order 2 KTY84-130 restictors, when I put them in serie and add another normal restictor it should come close.
It tried for sometime with the KTY restrictors. They showed however very sensitive for the supply power of the controlling unit and although the controller worked the temperature were not very reliable.
I replace the temperature sensors with DS16B20 sensors as advise in this topic. Build a small oled screens with the collector and boiler temperature. I also build a 10 led display bar for the graphic display of the temperatures. (See Midi VU meter, LM3914, Arduino, PWM -)
