My system comprises multiple DS18S20, DS18B20 temperature sensors, some
DS2438 I/O modules and a DS2437 to measure system voltage.
The voltage normally sits at around 5.1 volts, up to maybe 5.15 when no
outputs are on, down to 4.95 with several outputs on.
A while back I saw the voltage drop to 4.82 and it stayed low even with
the outputs off. Power cycle and it was back to normal again.
I have just seen this happen again, but this time I noticed something
else. I have a DS18S20 in the loft space and it was reading 63 degrees
C, but the actual temperature was more like 23 - 24. Again the voltage
stayed low even with all outputs off.
I power cycles it and the voltage came back to normal and the DS18S20 in
the loft space dropped to 23 degrees, which seems correct.
The system takes around 8-10 seconds to run through everything
Looking at the logs I see
21 deg 5.04 volts - all is fine!
85 deg 4.82 volts - read failure
37 deg 4.82 volts - seems to be reading OK but value is high
rises to 50 deg over the next 60 seconds
rises to 60 deg over the next few hours
Power cycle
34 deg 5.14 volts - all seems OK but temp still high
drops to 24 deg over the next 5 minutes, which seems correct
So the question is - is it possible to have a fault on a DS18S20 which
can cause it to heat up and pull the voltage down?
Thanks
Mick
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