Reef-Pi Temperature Dropping to -1?

[ReeferLou]

Hi All,

Just wanted to see if anyone else has an issue with the Reef-Pi temp dropping to -1 a few times a day. I just replaced my DS18B20 temp probe since my previous one started to drift and was dropping occasionally too. I put a new probe and also double sealed the end with a straw and some aquarium silicon to prevent water damage. I am still running reef-pi 4.1 since I have been extremely happy with everything and I search the git and did not see any fixes for this type of issue.

As you can see in the graph below the lines are the drops to -1

Thanks for any feedback .

 

[Ranjib]

this happens when the sensor reading is failed https://github.com/reef-pi/reef-pi/blob/main/controller/modules/temperature/sensor.go#L33 .

 

[ReeferLou]

Thanks. I see there can be multiple sources of the error. I will try to read the w1_slave file when the error occurs to rule out a bad sensor vs a open connection. The file /sys/bus/w1/devices/28-0119387cd43d ) has format like this:

90 01 4b 46 7f ff 0c 0c 0d : crc=0d YES
90 01 4b 46 7f ff 0c 0c 0d t=25000

Temp is 25 deg C = 77 in this read.

 

[ReeferLou]

Note on the DSB protocol in case anyone is interested:

90 01 4b 46 7f ff 0c 0c 0d

Byte 0,1 : Temp = 0190h = 400 dec x .0625 (12 bit resolution) = 25 deg C
Byte 2,3 = alarm bits TH= 4b=75 deg C TL 46=70 deg C Assume not used by RPi

Byte 4: Config = 7f = 12 bit resolution

Byte 5-7: Reserved

Byte

 

[Ranjib]

Reef-pi check for that “YES’” at the end of the file. Absence of that indicates checksum or other kinds of failures

 

[ReeferLou]

I am writing a script to log all the w1_slave values to a text file to prove this but..... I suspect what is happening is that the w1_slave file is empty when the call is done to open it an count the lines and look for the YES. So the file will not have 2 lines of data.

Could be a synchronization issue in reading and updating that file?

I also do not get any error in the reef-pi log in configurations.

I am running the VNC in the background so maybe this is affecting the performance?