Raspberry Pi 3

The latest and greatest from the awesome Raspberry Pi team! An iterative upgrade but very welcome addition of on-board WiFi and a faster processor.

The latest emonSD for emonPi / emonBase seemed to work out of the box with the RasPi3, however it became apparent that something rather important was missing...serial communication with the emonPi's ATmega328!

The emonPi communicates with the RasPi via GPIO 14/15 which on the Model B,B+ and Pi2 is mapped to UART0. However on the Pi3 these pins are mapped to UART1 since UART0 is now used for the Bluetooth module. However UART1 is software UART and baud rate is dependent to clock speed which can change with the CPU load, under voltage and temperature; therefore not stable enough. One hack is to force the CPU to a lower speed ( add core_freq=250 to /boot/cmdline.txt)which cripples the Pi3 performance.

A better solution for the emonPi is to disable BT and map UART1 back to UART0 (ttyAMA0) so we can talk to the emonPi in the same way as before.

Read on →

Outdoor Temperature Data from Weather Underground to Emoncms & MQTT

Monitoring the temperature outside your house is super useful to inform your home automation systems and calculate domestic heating (and dressing!) requirements.

One way is to monitor external temperature is to install your own external emonTH wireless temperature node or use a commercial web-connected weather station. However a cheaper way is to tap into the Internet of Things and connect to another weather station in your area.  Weather Underground have over 18K weather stations online in the USA and a free API for non commercial use.

Here's an example of using nodeRED to poll the Weather Underground API and post to Emoncms (using nodeRED Emoncms flow) and MQTT. Read on →

Heat pump Testing: Initial results

Headline figures
Test period: 17th of October to 7th of February (113.3 days)
Electricity input: 413 kWh (3.6 kWh/d)
Heat output: 1405 kWh (12.4 kWh/d)
COP: 3.4
Electricity input includes: heat pump compressor, heat pump controller and circulation pump.

In late October last year I installed with John Cantors help an air source heat pump at home, I currently live in a small cottage in Snowdonia, North Wales and after several winters of heating with a wood stove and direct electrical fan heaters, its been great having a warm place with much reduced electrical input requirement and wood consumption and its given me a good opportunity to test the technology in order to understand and confirm how well it works, albeit in a building which is far from low energy in terms of building fabric performance.

Here is a photo of  the cottage which gives a good idea of the kind of building it is; for a detailed look at the space heating energy requirements and building fabric see appendix. Read on →

Low carbon energy film featuring OpenEnergyMonitor

A few months ago we were lucky to be contacted by a French film team wanting to feature OpenEnergyMonitor as part of a film about low carbon energy. The film "ACHIEVING 2050 I OPTIMIZE ENERG" aired in November this year.

The film can be watched online here (in French), the part featuring us starts at 28min in: Read on →

Heatpumps in the ZeroCarbonBritain model by the Centre for Alternative Technology.

Following on from last blog post on heat pump monitoring I will try in this post to give a bit of context on heat pumps. Heat pumps are interesting because they provide a way to make efficient use of renewable electricity for heating. They are used in many zero carbon energy scenario's including the ZeroCarbonBritain scenario from the Centre for Alternative Technology which is one of the most comprehensive UK based 100% renewable energy scenarios created.

This sankey diagram from the ZeroCarbonBritain report gives an overview of the energy flows in their scenario, with heat pumps providing the bulk of the heating and hot water demand: Read on →

Heat pump Monitoring

For a number of years now I have been working with John Cantor on monitoring heat pumps. John is one of the UK's foremost experts on heat pumps having worked in the field since the early 1980's, he has written a book on heat pumps and is an advisor and consultant on the technology.

Earlier this year we worked on reading heat metering data from a Kamstrup heat meter in order to obtain accurate heat output measurement in addition to system flow temperatures and electrical power input. After spending quite a bit of time adapting existing emontx hardware and often emontx v2 hardware to integrate the additional circuitry required we decided it might be better to try and design a dedicated heat pump monitoring board that would have all the functionality we needed on a single board.

This board is currently going through initial testing.
Read on →

OpenEnergyMonitor, emonPi and openHAB

Using the emonPi in it's current default configuration works great to post data to Emoncms for logging and visualisation. However there may be times when you want some more flexibility and or ability to interface with other hardware or services 

In my last few blog posts I have been taking a look at making the emonPi the heart of a smart energy optimised home and how live energy monitoring data from the emonPi can easily be used to inform other services:   

North Wales Tech Meetup Presentations

Yesterday evening Trystan and I attend a local meetup in Bangor, North Wales hosted by NorthWalesTech It was a good event with some interesting talks. Here are the slides from the 5min lightning talks we gave:
My slides give a brief overview of the OpenEnergyMontor project before diving in to MQTT and node-RED with a live demo controlling LightWave RF plugs switching Christmas lights over the web using MQTT and nodeRED:

Slides from N.Wales Tech meetup Dec 15. Brief overview of OpenEnergyMonitor and MQTT, nodeRED and LightWaveRF demo.

Related blog posts:


Trystan's lightning talk was focused on a heatpump which he has recently installed with John Cantor to heat his home. Trystan gave an overview of heatpump technology, his monitoring setup and the preliminary performance results:

Remote Control of LightWave RF plugs via MQTT using emonPi with OOK Tx

Using a Raspberry Pi as an emonPi / emonBase web-connected base station for energy monitoring has many advantages (maintainability, remote access, debugging, updated etc.) but it does seem rather wasteful to have a 900Mhz 1GB RAM machine being used to post a couple of integers to a web-server! The always-on nature of a web-connected base station and plenty of spare processing power makes it ideal to use the emonPi for more than just energy monitoring; home automation and heating control optimisation are obvious candidates.


Many home automation products such as RF plugs, relays and heating remotes use a simple OOK (On-Off-Keying) wireless protocol. UK company LightWaveRF produce a variety of RF plugs and relays which can be controlled via OOK RF. The protocol is also compatible with some cheaper OOK learning receiver relays.  While maybe not strictly open-source the protocol and been reverse engineered allowing plugs to be easily controlled from Arduino / Raspberry Pi. There is an active LightWaveRF online community. Using off-the shelf hardware like this is a 'safe' way to control lights, heaters and appliances  around a home without getting our hands dirty dealing with with high voltages. These plugs and relays can be used to control anything from lights to immersion heaters, most LightWaveRF plugs/relays will switch up to 13A / 3kW.

Note: OOK protocol by it's simplistic nature is not particularly secure, I would not recommend controlling anything you don't mind getting accidently switched.

An OOK transmitter can easily be added to the emonPi.  We have started stocking OOK transmitter modules in the OpenEnergyMonitor store as well as adding an option to have OOK module factory installed on new emonPi's.

See emonPi Technical Hardware Wiki for details how to retrofit OOK TX module to existing emonPi's.


We have been working with Lawrie Griffiths from Geek Grandad blog to develop a LightWaveRF MQTT service to run on a Raspberry Pi to allow LightWaveRF plugs to be controlled via MQTT.

Once running a plug can be controlled by publishing to the 'lwrf' MQTT topic:

E.g "1 1" switches on plug 1 while "1 0" switches off plug 1. Plugs can be paired in the usual LightWaveRF plug.

See emonPi technical Wiki for how to install & setup.

Existing LightWaveRF remotes can be emulated allowing plugs to be controlled from either emonPi MQTT or via the remote.

Now our plugs can be controlled via MQTT there are a many of options open as to how to control either via interface openHAB (blog post coming soon..), nodeRED, android Tasker etc.

I have been using nodeRED with input from android OwnTracks running on my phone to detect when I'm home and turn on a couple of lights:


Using NodeRED and OwnTracks to turn on LightWave RF sockets when I arrive home: 

Using android Tasker with  AutoVoice and MQTT plugins to control LightWaveRF sockets:

Next Steps

Now we can control appliances remotely via MQTT the next logical step is to add a mobile user interface. In my next blog post I plan to explore setting up openHab to control appliances. Here's a early preview: 

We plan to include out-of-the-box support for OOK LightWave RF, nodeRED and openHab pre-configured on our next emonPi pre-built SD card. Due for release in December 2015.