I purchased 3 grove onewire temperature probes to track my solar hot water heating system. I have it attached to an Adafruit Feather M0 airlift and use a Grove Particle Mesh shield. My solar is a closed loop system, meaning I run glycol in the solar loop and the heat transfers into the tank with an exchanger.
One probe measures the water inside my tank, another the temp of the solar glycol fluid going into the heat exchanger, and the last coming out of the heat exchanger. This lets me measure how much heat is transferring into my tank. Was excited as 2 of the probes were in harmony and the other only about 0.5F different. Often the temp transferred into my tank isn’t even 1F so the ones in perfect sync were a blessing.
I hooked it all up, works great, except the probe that measures the glycol going into the heat exchanger works flawless until 131F and then gets stuck there as temps continue to rise, once the temp is about 145F then it will increase to say 132F. I then start to see that going into the heat exchanger is 132F and coming out is 145F which makes no sense. In the evening when the solar glycol loop drops to 130F it then starts to work again and show accurate temps.
I don’t know how these probes work, but does that make any sense? I replaced that sensor and the new is working but my Spidey sense can’t seem to grasp how that one can consistently work up to 131F and then gets stuck time after time and when temps get below 131F starts working again.
What exactly is this product? can you provide a link or SKU#
Does the particle shield match the pinout?
The temperature probe you are using should be within its specified operating range. Some temperature sensors have an upper limit beyond which they may not function correctly. If 131°F is near the upper limit of the sensor’s range, it may explain why the readings get stuck around that temperature.
Try using different models or brands of temperature sensors to see if the issue persists. Here are some more alternative temperature sensors: Interface DHT11 Sensor with Raspberry Pi 4 - The Engineering Projects
Thanks, the particle mesh shield is correct but my feather is Assembled Adafruit Feather M0 WiFi with Stacking Headers : ID 3044 : Adafruit Industries, Unique & fun DIY electronics and kits
They warn when using the particle mesh shield the pin #'s don’t match what’s on the feather so some experimentation is needed to get the real pins. I made a simple program that goes from pins 20 to 1 and put the temp probe one at time to get what pin goes to what port.
I had a thought, these one-wire probes need a resistor connected between yellow and red (if you get the non-grove version, the grove version they put in the resistor). I’m thinking the easiest explanation is that there’s a short/crack which, everything is fine until it reaches 131F then the short/crack happens (probably with that resistor) and it doesn’t work right. Once temps drop below 131F the short/crack fixes itself and why it starts working again. I think that’s the occum’s razor (“The simplest explanation is usually the best one.”)
Thanks!
Hi there,
So is it powered or are you using parasitic power method?
Look at those and know what your doing… 
HTH
GL 
PJ
I have a demo on here using a one wire probe on the Grove Expansion board, using the Parasitic method.
