Add temp sensors to EmonHP

New to OEM, just purchased Heat Pump Monitoring bundle but without Heat Meter option for time being.

Also purchased 2 x temperature sensors (Encapsulated DS18B20) with RJ45 terminal block (emonPi / emonTx RJ45 to Terminal Block Breakout for DS18B20).

Any advice on how to connect temp sensors to EmonHP, which doesn’t appear to have second RJ45 for probes etc?

The emonHP does not support connecting external temperature sensors. The emonHP bundle is designed to work with heat meters which provide flow and return temperatures which is all that’s required for heat pump monitoring and COP calculation. Outdoor temperature is provided from a metoffice observation.

Potentially an RFM69Pi receiver could be added to the emonHP to receive data from the emonTH. I’ll have to check if the RFM69Pi will fit in the emonHP enclosure, and also we’re currently out of stock of emonTH.

Thanks Glyn,
At some point I will order and fit the heat meters, but there are various difficulties now. Hence I just plan to get through this winter monitoring electricity plus DHW cylinder and Buffer Vessel temps using DS18B20 probes.
I would also like to add TH Nodes to several rooms too, maybe 4 to start with. Another 4 pending other works in the home.
Any thoughts on how best to approach this now so that the system can be scaled up?

If the RFM69Pi does fit in the emonHP enclosure, then that seems like a great place to start.
Many thanks for your help.

PS absolutely loving having the emonHP up and running, even if it’s just monitoring electricity for now.
Prior to emonHP, I’d have to read the LCD display on meter in heat pump (whose pulse outputs are not even connected) and enter into a spreadsheet. I also tried using a cheap DIN rail electricity meter which used its own proprietary phone app – great for seeing a crude, un-customisable graph, but wouldn’t allow me to download data.

The Simplest way (IMHO) is to use a WemosD1 (get a genuine one rather than a clone) and Tasmota (or ESPHome). Tasmota will handle 8 sensors. ESPHome is a better choice if you are using HomeAssistant.

I put together a small breakout board with sockets and added plugs to the DS18B20 probes so I could swap easily if necessary.

Out of curiosity, what hardware is inside the emonHP?

There’s a Raspberry Pi inside that aluminium case, with a small breakout board to access the ports from the outside.


Sorry, I’m afraid the RMF69Pi doest fit inside the emonHP enclosure.

However, the new RFM69CW direct to RasPi board that @TrystanLea has been working on should fit, this board is not yet in production, but we may have a few to spare. However, since we’re currently out of stock of emonTH this is not very useful, but will be in the future!

It’s also possible to connect a DS18B20 direct to the raspberryPi with the addition of a single resistor:

EmonHub has support for reading direct from DS18B20: emonhub/conf/interfacer_examples/DS18B20 at master · openenergymonitor/emonhub · GitHub

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thanks Glyn,
Given that all of this will be located within a 19" wall-mounted rack case with glass door, containing RJ45 patchbay, unmanaged switch, etc. then maybe that’s not an issue?
I’m happy to install a dedicated rack shelf for the OEM kit and interconnect myself.
What do you think?

BTW the tank and probes are ~10m from emonHP. Hence thinking hard-wired instead of RF. What would I need to add the same sort of extra (non-LAN) RJ45 to emonHP?

Thanks Brian, I wasn’t aware of those options but after a bit of Googling looks v interesting.

But first, I’d like to explore capability of emonHP before getting into a parallel system. Still learning here. Best, David

You can do the same as I suggested above, but just connect direct to the Pi.

I’d hard wire to the Pi (add the resistor there) to just outside the EmonHP and then fit a small connector at that point. I do this for any device I put together - you always want to unplug it for some reason!

You can then run a single wire to a breakout box of some form and then connect the Sensors to that.

OEM sell some RJ45 wired sensors - I usually buy sensors and connectors from Aliexpress and make them up myself as it is much cheaper, but I do have the pins and crimping tool etc.

Thanks Brian, Glyn,
Works perfectly.
Best, David

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