DS18B20 Temperature

I’ve a single RJ45 Encapsulated DS18B20 temperature sensor, the DS18B20 is not found?
2017-02-01 12:34:44,153 INFO RFM2Pi Publishing: emon/emonpi/power1pluspower2 45
2017-02-01 12:34:44,156 INFO RFM2Pi Publishing: emon/emonpi/vrms 253.22
2017-02-01 12:34:44,157 INFO RFM2Pi Publishing: emon/emonpi/t1 0

It is necessary to have a RJ45 Expander ?

Have you restarted the emonpi board?

temp sensors are only looked for at the start-up of the firmware. On an emonPi this will involve a power cycle rather than a reboot as it’s the firmware on the attached emonpi board rather than the software on the Pi that needs restarting. A restart could be induced via the command line but that is not documented or easily accessible so it’s probably easier to power cycle the emonPi.

Yes, firmware message:
Detected: 0
DS18B20 Temp

Hopefully a daft question. Do you have the temp sensor plugged in to the right RJ45? ie the one next to the CT’s NOT the one next to the USB ports, that’s an Ethernet socket.

Otherwise it would seem you have a bad connection or faulty sensor. @Robert.Wall has advised on other threads there maybe a poor conn at the rj45 plug and maybe the little gold contacts can be pushed further into the wires, possibly by carefully using a screwdriver (slotted) to push on each contact at 90deg to the cable entry, ie sideways into the cable rather than on the end.

To resurrect a very old thread - I couldn’t get my new emonPi to recognise a new DS18B20, and so following the comments above I checked the contacts (all seemed good); I then plugged in a second DS18B20 and it worked perfectly. I’ll play some more but it could be that it is faulty.

As Paul said, if the RJ45 isn’t crimped fully home (or it’s not the correct RJ45 for the wire type) then you can have problems. On the back of the plug contact is a spike that pierces the wire insulation. I’ve used the back edge of a craft knife blade to push the contact fully home, and then a collar of hot melt glue where the cable enters the plug to provide a better strain relief.