emonBase & RJ45 to Terminal Block Breakout for DS18B20

I have an emonPi monitoring my Solar etc, and I want to measure some temperatures elsewhere in the house so I figured, why not use another Pi? So I have:

  1. Raspberry Pi 2 model B v1.1, powered by iPhone plug 5v DC 1a.
  2. 8gb card with emonSD-03May16 image.
  3. RJ45 to Terminal Block Breakout for DS18B20 connected to RPi via RJ45.
  4. 5x DS18B20 sensors wired into the Breakout.

I was hoping that would magically give me the 5 temperatures but no, that would have been too easy. I have avoided having 2 emonPi devices on the same network (in case that causes problems) by using an old router.

When I log into emoncms on the above Pi there are no nodes on the inputs page; I was expecting to see a node 5 for the Pi, and the list of inputs, similar to what I see in the proper emonPi, and it appears to be configured that way by default in the EmonHub Config Editor.

Is what I’m trying to do reasonable?
If so, have I missed something?


I’m not sure if you are using a “Pi” or an “emonPi” so this bit worries me

There is nowhere to plug the RJ45 breakout into a regular Pi, there is an actual ethernet socket for connecting to a network but you shouldn’t be plugging temp sensors in there, I have no idea how either party will cope with that.

The normal Pi can work with 1-wire but you will need to hook up via the gpio connector.

If you are using an emonPi it should indeed work as you expect IF you are plugging the RJ45 breakout in the right end of the emonPi as that too has an Ethernet socket at the other end. if you are using an emonPi the node 5 should be there with or without the temp sensors so you should work on getting that sorted first before plugging the temp sensors in.

Ah, I see, I’m using a regular Pi; thanks!

Funny thing is, plan A was to connect it to my emonTx, I wired up the sensors and… It’s an emonTx v3.2 with no RJ45 socket! Usually I’m guilty of not reading the instructions but on this occasion I read them but didn’t think to check the gadget!

Can you tell I’m more a software guy than hardware/electronics?

You can use one of these modules to connect the RJ45 DS18B20 network you have directly to a RaspberryPi:


See RaspberryPi info page, they do a variety of different adapters. The RP2 looks like the best suit for you, since you have 6 sensors I don’t think the rpi1 running at 3.3V would work.


There will also be software configueration. The easiest method to get the data into emoncms is via MQTT, possibly utilising nodeRED

I would ditch the RJ45 breakout and wire the 6 sensors direct to the emonTx v3.2 terminal block (probably via a bit of terminal strip as 6 wires will be a squeeze at best).

That was the original wiring method before RJ45 was adopted, see the wiki section on emonTx v3.2 temperature sensing. It does state there that the default firmware only does one sensor but times have moved on and the current v3.2 firmware does 6 sensors.

You would need to use a 5vdc power source for the emonTx rather than powering via the ac:ac adapter but aside from loading the new sketch, editing emonhub.conf and attaching the temp sensors you should be set.

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Even better as there is probably no change required (unless running on batteries?)

Thank you all for the advice & guidance; I have a question, it’s probably stupid, but I’ll ask it anyway as you already know I’m a numpty.

Could I not chop an RJ45 cable, plug it into my breakout board and connect the relevant 3 wires into the emonTx terminal block?

This is incorrect, the emonTx V3.2 CAN be powered by AC-AC adapter. All versions of the emonTx V3 have had this feature. See emonTx V3.3 Wiki. The V3.4 hardware update just included RJ45 socket, DIP switches to set node ID and RFM69CW (although the first hundred V3.4’s where shipped with RFM12B due to a 69 shortage).

Sure, this will work. See V3.2 terminal pinout.

D’Oh - Even though I typed “V3.2”, my brain was on V2! Sorry for the confusion.

No worries, happens to me all the time!