06-19-2021, 04:25 PM
(06-19-2021, 02:34 PM)Rob F Wrote: Hi Phil, sorry to hear, yeah unfortunately this can be a problem but as far as I know people who were affected got if fixed one way or another. When you tried the Maxim sensor did you unplug the other DS18B20's? They share the same pin so if one hangs the bus the others are effected. With a little mod you can use a sensor port as another 1wire bus so they are on separate lines but doesn't fix the issue.
Other possible causes can be electrical noise affecting the sensor, for example a pump turning on. In one case someone had this issue and after plugging the controller into a different AC circuit in the house the problem went away. As it appeared to work until you moved it to fish room maybe it's something sharing the same power line creating too much electrical noise.
Another source of noise can come through the aquarium, adding a ground probe to the tank could help. If you have a piece of wire you could add a temporary probe, place the wire in the tank and other end in the Ground of an AC outlet. You could also simply leave the probe out the tank to see if problem goes away.
Unfortunately I've never experienced this nor has the people who develop the software so it's hard to troubleshoot. A little while ago I was told about the trick of cutting power to sensors via GPIO but that requires changes in reef-pi to perform the reset.
Any chance you have another SD card and you could load up my software to see if the problem persists? On my test setup I'm running 3 sensors, when I started I would get 186 or -1 sometimes on a sensor or two, never locked up though. I added some checks in the code to skip on different errors and no longer get false readings but in log can see it still happens just it's caught now. I'm wondering if catching the errors when it happens will prevent the bus from locking.
Rob F asks: When you tried the Maxim sensor did you unplug the other DS18B20's?
Yes: right now, it's the only sensor and the error has appeared.
Rob F comments: As it appeared to work until you moved it to fish room maybe it's something sharing the same power line creating too much electrical noise.
I have 3 independent AC circuits in the fish room. All my systems (lights, pumps) are dual to get redundancy, plus there is one other circuit that has no fish room stuff (pumps, lights, heaters, etc) on it. Originally I had plugged the controller into that one, but I moved it to one of the others and got no improvement.
Rob F comments: adding a ground probe to the tank could help
I had already considered that and sealed the metal thermometer bulb in heat shrink and RTV to preclude any potential ground loop/common mode issue: no improvement.
Rob F asks: Any chance you have another SD card and you could load up my software to see if the problem persists?
I don't understand what you are asking here. I'm sure I could find another SD card, but this controller is now running my reef. Is the software you want me to load some custom version of reef-pi, or something else? What's involved with giving it a try?
One other thing I noticed this afternoon is that the PH probe stopped working a while ago, with a similar error:
ph subsystem: Failed read probe:PHError:pin 0 on analog input 1 has no driver: driver 1 for analog input pH not found: driver by id 1 not available
Thanks for helping out,
Phil
