Help, I am new to this

Hi Everyone,

I have read and read all the different articles. I am coder so not totally a beginner to this. However I am confused by all the hardware options.

I have a property where 3 phase comes into a consumer unit. From there there are several circuits. 7 individual feeds go to a sub-meter and then on to a room. There are several other circuits for communal areas.

My requirement is to monitor the temperature in each room (10 in total - 7 bedrooms, hallway, landing, kitchen) these rooms are spread over 2 floors. I do have cat5 going to each room.

I also need to measure the electricity on as many circuits as possible possible 10 or more.

I also need to measure the Gas supply meter if possible, not sure if thats possible ?

My goal is to get as many relevant metrics as possible to make energy saving decisions.

My current thoughts are

Emon PI

RJ45 Encapsulated DS18B20 temperature sensors
a few of the SWE2 Sensor Connection Modules for the temp sensors

On the electricity monitor I am confused. I have 3 phase power but can monitor each of the single phases going to the rooms ? do I need a reference power for that (which would be impossible due to distance). I don’t need the wireless option as everything will be housed in a room which has the consumer unit breaker and all the cat5 feeds.

Any thoughts cause I would love some feedback


I’ll try to pick off as many points as I can.

  1. You’ll want an emonPi or an emonBase to store and publish the data and/or send it onwards to If you have an emonPi, you add two current/power inputs.
  2. The emonPi and emonTx are essentially a single-phase design.
  3. Do you have 7 sub-meters, and are they single or 3-phase? I’ll assume each meter & room is single phase.
  4. You should be able to measure 10 temperatures from one device, but you need to be careful how the cabling is arranged. Those connectors might not necessarily be the best way forward. There’s some information and links to more in Resources > Building Blocks.
  5. If you treat the installation as three single phases, then you can monitor 4 circuits on one emonTx. However, there are some designs by others (Boredom Projects is one) that have more inputs. These are based on the same design and run very similar software as our emonTx, but I don’t know if these are available as finished items.
  6. If you can add a sensor to your gas meter, then it’s possible monitor that. The simplest is to use a magnetic compass and see if you can detect a magnet moving past as the fastest number changes. There are many threads in the old forum about gas meters.

I don’t understand what you’re getting at there.
If you want to measure real power, which is the quantity that the meters measure (as distinct from apparent power), then you need to measure the voltage (ideally on each phase independently) as well as the current to each load on that phase. Until you measure both voltage and current in the same device, you cannot measure real power.

What you need to do next is draw a distribution diagram showing which meters, rooms and other things are connected to which phases, and the points where you want to monitor the power. Also put on the diagram the anticipated maximum current at each monitoring point. You’ll then be able to identify the best mix of hardware - emonTx’s, emonBase or emonPi, or 3rd party hardware.

All the Emon units are designed to communicate by radio, but as you’re a coder, it shouldn’t be hard to connect them using a serial bus using one as a master to poll each unit for its data.

Thanks Robert

All the sub-meters are single phase. Basically its a multi-let property and we need to monitor energy use and how well the heating system is performing.
We would like to add to the monitoring to include hotwater temp in the tank etc but that can be at a later date.
I will put together a distribution diagram.

I was just reading more about the EmonPI and it occurred to me we have no need at all to log locally. These premises are to be monitored externally via internet.
Could we get away not having an EmonPI and just having a “device” that reads sensors and submits to the data. It would be nice to have MQTT as it would allows
to setup some automatic actions - Temp high in rooms cut the heating etc.

The heating and hot water system is setup on Hive. Has anyone interfaced with the HIVE, there is some documentation around its API online.

I don’t know about MQTT or Hive, so I’ll leave that to others to answer.

Thanks Robert, this is probably exactly what I need.
Just need someone to build it or something I can buy off the shelf :frowning:

You can buy emonTx’s off the (mail order) shelf, also emonBase (but you need to box it).
I didn’t mention power supplies and ac adapters, those will be needed too.

The one in the store doesn’t have the 10 inputs like the one boredom projects one. Can I link a few to the store emontx together ?

As I wrote above, the emonTx is a single phase device. So is Boredom’s. But you can fudge both to get an estimate of power on the other two phases. But using one emonTx per phase gives you 4 powers per phase and the best accuracy. This is why the distribution diagram is needed.
You’ll link them by modifying the default sketch. As it stands, it sends by radio every few seconds. You’ll need to change that to listen to the serial bus, then respond when asked. If you ask nicely, the shop may be able to do the emonTx minus the radio module - otherwise you just write it out of the sketch.

hello team,
I m new to this
how to measure 3 phase AC voltage using arduino uno and step down transformer.

If you want to measure the voltage of three phases separately, you need to look at [Learn] >Voltage Sensing ( and build 3 interface circuits of 3 step-down transformers - one to each phase.
You did not say that you want three currents as well, but if you do, then you need to add the very similar interface for three current transformers (“CT Sensors”). You can then write a sketch following the guidelines on those pages and using emonLib to give you the real power on each phase.

I am want to measure only three phase voltage and angle.
please help in sketch.

Can you clarify what you want to measure? The angle between phases is nominally 120° but any impedance in the neutral combined with an imbalance will mean that is no longer the case. Is it that which you want to measure?