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.

UK Grid Carbon Intensity API

Following on from my blog post creating an ambient indicator to indicate wind turbine renewable electricity generation we have extended the Emoncms UK electric grid statistic aggregation to calculate and record the UK electric grid carbon intensity i.e. the amount of carbon emitted per kWh (CO2/kWh). As before we have created a dashboard open API for easy access to this data.


UK grid carbon intensity:
UK wind:

Other feeds are also available including grid fuel mix and current energy demand, just place 'id' in the API with the feed ID's below: 

FeedNameCurrent Value (22/11/15 22hrs)
If you use the API in your project please drop us a line and give Emoncms some credit :-)

The data is captured from the UK Balancing BM Reports XML. Our figure for grid intensity matched the figure generated by

Node-RED Emoncms Node

I have recently been experimented using Node-RED for a number of tasks. Thanks to the work of others a Node-RED flow node already existed for Emoncms making it very easy to post data to Emoncms. For my Ambient Wind Energy Indicator I had the need to extract real-time feed data from Emoncms feeds using the Emoncms API. I have now contributed this functionality to the official Node-RED Emoncms node. Using the updated Emoncms node it's now super easy to post data to extract latest real-time feed values from any Emoncms server including

Get the latest version from: If you're interested in viewing and improving the functionality the open-source code behind the node is up on the Node-RED flows GitHub

Emoncms Node-RED node

Install with:

$ cd ~/.node-red
$ npm install node-red-node-emoncms

Node Documentation

Emoncms in Node Config

Emoncms Server Config

OpenEnergyMonitor November 2015 - Overview Presentation

Here's a few slides giving an overview of the OpenEnergyMonitor project as it stands currently in November 2015. It features some of the work we have been doing looking at the embodied energy involved in producing and shipping some of our products as well as latest developments on Emoncms application dashboards

OpenEnergyMonitor Overview November 2015 from OpenEnergyMonitor

Notes to accompany the slides can be found here.

Interpreting Emoncms Dashboards

The emonPi / emonTx standard install is designed to monitor whole house power consumption. An excellent learning exercise that we recommend everyone undertake soon after installing a whole house energy monitor is to turn off every appliance in the house then slowly turn on each appliance keeping a close eye on the real-time Emoncms dashboard. Walking around the house using a handheld mobile device to display the Emoncms dashboard works great for this. For fastest response we recommend connecting to the local Emoncms running locally on the emonBase / emonPi which will update ever 5s (emonPi default) or 10s (emonTx default).

After this exercise you should have a good idea what the trace signature of each of your appliances looks like on the graph. The easiest to identify are the large power consumers e.g kettle 3kW spike and shower 8kW spike. However with a bit of observation it's possible to identify subtler power signatures. Here's an excellent example by posted by @Zapaman showing a Solar PV dashboard annotated to identify his fridge / freezer and central heating pump running over night. It's great to see the solar PV kick in providing more then the demand when the sun hits the panels in the morning :-)

Ambient Wind Energy Indicator using Node-RED and Blink(1) USB

As we move to a low carbon electric grid with large amount of input from renewable sources we will need to match our consumption of energy to generation. The wind will not always blow and the sun doesn't always shine. Grid energy storage will play a role, however the closer we can match our consumption of energy to generation the less storage will be required. In the future we can expect dynamic pricing to act as as an incentive for shifting consumption patterns. 

As an experiment I have been playing around with creating a real-time ambient indicator of UK wind energy generation. Since wind energy is the greatest input of renewable energy into the UK grid we can assume that when wind generation output is high this is the best time for us to use power e.g. run the washing machine, dish washer etc.. 

I've used,  Node-RED and a ThingM blink(1) USB RGB LED plugged into an emonPi energy monitor to create the indicator.

Real-time wind energy indicator

Blink USB Indicator

First let's install the software to control the Blink(1) USB on the emonPi / RaspberryPi:

$ git clone
$ sudo cp ~/blink1/linux/51-blink1.rules /etc/udev/rules.d/
$ sudo udevadm control --reload-rules
un-plug then re-plug device
$ cd blink1/commandline
$ make

Note: if Node HID fails to compile you may need to install gcc-4.8. I did not experience this problem using Raspbian Wheezy:

Test it's operation by turning on a white LED with
$ ~/blink1/commandline./blink1-tools --on

To make the Blink(1) USB work with Node-RED we need to install the Blink(1) node-RED flow and libusb driver. If you haven't already got it installed this example also requires the emoncms noe-RED flow to pull data from

$ sudo apt-get install
$ cd ~/.node-red
$ npm install node-red-node-blink1
$ npm install node-red-node-emoncms

Then restart node-RED.

Node-RED makes it super easy to link the required software components together, with pre built nodes available for emoncms and Blink USB it's just a case of linking the nodes together and adding some logic. Here is now node-RED flow, see node-RED export at bottom of this post:

We have a script running on to pull in real-time UK wind energy generation. We have been logging this data for almost a year now. Checkout the dashboard here:

The read API key for this account is 8f5c2d146c0c338845d2201b8fe1b0e1 and the feed ID is 67088. To pull the real time data into node red just plug in the  api key and feed ID into the node-RED emoncms in node. Node-RED will then execute the following GET request:

The blink usb node requires RGB csv to represent a colour output. A node is used to map the generation 0 -  7000 MW (currently!) to 0 - 255 RGB representation. 

[{"id":"98c24074.673dc","type":"emoncms-server","server":"","name":"emoncms UK windpower"},{"id":"5a3294d0.a5cd6c","type":"function","name":"Create RGB values CSV","func":"// convert to integer \n//var wind = +msg.payload;\n\n// green = 255 @ max wind output\nvar g = msg.payload\n\n// red = 255 @ zero wind output\nvar r= 255 - msg.payload\n\n// Round to whole number\ng = Number((g).toFixed(0));\nr = Number((r).toFixed(0));\n\nvar csv = r + \",\" + g + \",\" + 0;\nreturn {payload:csv};","outputs":1,"noerr":0,"x":617,"y":348,"z":"c0b0c402.3f4f38","wires":[["52d8719f.ad279","f3dd00d0.0c23"]]},{"id":"6ec040ed.913fc","type":"inject","name":"Trigger every 10min 7AM-11PM","topic":"","payload":"1445415635","payloadType":"string","repeat":"","crontab":"*/10 7-22 * * *","once":false,"x":297,"y":261,"z":"c0b0c402.3f4f38","wires":[["68f8d790.970728"]]},{"id":"52d8719f.ad279","type":"debug","name":"","active":false,"console":"false","complete":"false","x":878,"y":334,"z":"c0b0c402.3f4f38","wires":[]},{"id":"b5d43139.4a2bd","type":"inject","name":"Test 100MW","topic":"","payload":"100","payloadType":"string","repeat":"","crontab":"","once":false,"x":223,"y":421,"z":"c0b0c402.3f4f38","wires":[["2da76a85.d25896"]]},{"id":"9122dd65.6edd2","type":"inject","name":"Test 2000 MW","topic":"","payload":"2500","payloadType":"string","repeat":"","crontab":"","once":false,"x":225,"y":469,"z":"c0b0c402.3f4f38","wires":[["2da76a85.d25896"]]},{"id":"b5c8e6e5.4a3718","type":"inject","name":"Test 5000MW","topic":"","payload":"5000","payloadType":"string","repeat":"","crontab":"","once":true,"x":224,"y":514,"z":"c0b0c402.3f4f38","wires":[["2da76a85.d25896"]]},{"id":"f3dd00d0.0c23","type":"blink1","fade":"600","name":"Blink(1) USB","x":847,"y":440,"z":"c0b0c402.3f4f38","wires":[]},{"id":"68f8d790.970728","type":"emoncms in","name":"Get UK wind generation output from","emonServer":"98c24074.673dc","feedid":"67087","x":263,"y":343,"z":"c0b0c402.3f4f38","wires":[["2da76a85.d25896"]]},{"id":"2da76a85.d25896","type":"range","minin":"0","maxin":"6000","minout":"0","maxout":"255","action":"clamp","round":true,"name":"Range: Scale wind output to RGB value","x":551,"y":417,"z":"c0b0c402.3f4f38","wires":[["5a3294d0.a5cd6c"]]},{"id":"64a3fa26.9b5c04","type":"inject","name":"Turn off after 11PM","topic":"","payload":"0,0,0","payloadType":"string","repeat":"","crontab":"01 23 * * *","once":false,"x":613,"y":488,"z":"c0b0c402.3f4f38","wires":[["f3dd00d0.0c23"]]}]

emonPi, NodeRed and MQTT

Using the emonPi in it's 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.

Using a tool called Node-Red the emonPi can become a central hub for home automation, control and notification. Node-RED is a tool for wiring together hardware devices, APIs and online services in new and interesting ways. At the heart of Node-RED is a visual editor allowing complex data flows to be wired together with only a little coding skills.  Here are some of my ideas of things I might like to achieve with Node-RED, For more inspiration check out Martin's IoT Google hangout 29min in:

Install Node-RED on emonPi / emonHub / Raspberry Pi 

Make emonPi file-system RW:
$ rpi-rw

Install Node-RED (taken from node-RED RaspberryPi install guide):
$ curl -sL | sudo bash - 
$ sudo apt-get install -y build-essential python-dev python-rpi.gpio nodejs
$ sudo npm install -g --unsafe-perm node-red

Open up port 1880 so we can access Node-RED editor:
$ sudo iptables -A INPUT -p tcp -m tcp --dport 1880 -j ACCEPT

Open up port 1883 so we can access MQTT server:
$ sudo iptables -A INPUT -p tcp -m tcp --dport 1883 -j ACCEPT

Make iptables rules persistent
$ apt-get install iptables-persistent

Choose yes to save rules, if needed edit the persistent rules:
$ sudo nano /etc/iptables/rules.v4

Start Node-RED with:
$ node-red-pi --max-old-space-size=128

To view the node-RED graphical editor browse to:
http://emonpi:1880/ (or use IP address if this does not work)

To use Node-RED as a permanent setup you will want to set it up as a service to autostart at boot and enable secure authentication access to node-RED editor.

When you are done don't forget to put the emonPi back to read-only mode to preserve SD card lifespan:
$ rpi-ro

Getting data from the emonPi into Node-RED

There are two options to get our energy data into Node-RED:

1. Real-time data from emonHub using MQTT (see example below):

MQTT is a lightweight communication protocol for small web-connected devices. The latest version of emonHub as setup on the emonPi (and emonHub from July 15) uses MQTT as a link to Emoncms and also to provide data to the emonPi LCD script. Since MQTT is already running all we need to do is to point Node-RED MQTT input block to subscribe to the 'emonhub/rx/#' MQTT topic on port 1883. The '#' topic includes data received from all nodes. To subscribe to just one node use e.g. emonPi use: 'emonhub/5/values' or 'emonhub/10/values' for emonTx.

To subscribe the the emonPi's MQTT topics externally (if your running node-RED on another machine) you will need to open up the MQTT port on the emonPi:

$ sudo iptables -A INPUT -p tcp -m tcp --dport 1883 -j ACCEPT

2. Historic data from Emoncms using HTTP API: 

To pull historic data already logged to Emoncms (e.g KWh data) into Node-RED we can use Emoncms's API. Here is a simple example to pull in the latest value from the KWh feed, just enter your RW API key and feed ID:

To view all Emoncms API see:

Node-RED example: send warning email when emonTH battery is low

Simple but useful example, use Node-RED connecting to emonPi in real-time data via MQTT (localhost) and sending email (via Gmail SMTP) if emonTH battery drops below 1.7V. Also in this flow as an example is a node to decode emonPi power data.

Here is the contents of each node: 
MQTT Node subscribing to emonhub mqtt topic on localhost (running node-RED on emonPi)
Separate node to split the MQTT data up into nodes based on ID: e.g emonTx = 10, emonPi = 5, emonTH = 19
CSV node to split up MQTT CSV string
If function node
email node, enter your Gmail (or otherwise) SMTP login

Node-RED flow export, import by copy and pasting into import>clipboard in Node-RED editor:

[{"id":"eb57a13e.14a86","type":"mqtt-broker","broker":"localhost","port":"1883","clientid":""},{"id":"44c7eefa.bb381","type":"mqtt in","name":"MQTT: emonhub/rx/#","topic":"emonhub/rx/#","broker":"eb57a13e.14a86","x":159,"y":386,"z":"fa6ca080.05936","wires":[["2c7fcc53.d38034","eb7e04d9.1481f8"]]},{"id":"2c7fcc53.d38034","type":"debug","name":"RAW MQTT output: emonhub/rx/#","active":false,"console":"false","complete":"topic","x":242,"y":461,"z":"fa6ca080.05936","wires":[]},{"id":"eb7e04d9.1481f8","type":"switch","name":"Seperate Nodes","property":"topic","rules":[{"t":"cont","v":"5"},{"t":"cont","v":"19"},{"t":"cont","v":"20"}],"checkall":"true","outputs":3,"x":343,"y":317,"z":"fa6ca080.05936","wires":[["b0618044.4f9e8"],["9077dea0.6f882"],[]]},{"id":"9077dea0.6f882","type":"csv","name":"emonTH 1: emonhub/19/values > Decode MQTT CSV","sep":",","hdrin":"","hdrout":"","multi":"one","ret":"\\n","temp":"temp,temp_external,humidity,battery,pulsecount","x":664,"y":373,"z":"fa6ca080.05936","wires":[["75ee731f.8a118c"]]},{"id":"b0618044.4f9e8","type":"csv","name":"emonPi: emonhub/5/values > Decode MQTT CSV","sep":",","hdrin":"","hdrout":"","multi":"one","ret":"\\n","temp":"power1,power2,power1_plus_2,Vrms,temp1,temp2,temp3,temp4,temp5,temp6,pulseCount","x":647,"y":236,"z":"fa6ca080.05936","wires":[["cda897fa.325768"]]},{"id":"cda897fa.325768","type":"debug","name":"Debug: emonPi Power1 output","active":false,"console":"false","complete":"payload.power1","x":1015,"y":235,"z":"fa6ca080.05936","wires":[]},{"id":"75ee731f.8a118c","type":"function","name":"If emonTH battery < 1.7V","func":"if (msg.payload.battery < 1.7) {\n   return {payload:'WARNING: emonTH battery low  '+msg.payload.battery+'V'  };\n}","outputs":1,"noerr":0,"x":1015,"y":363,"z":"fa6ca080.05936","wires":[["f8d8fd72.0727"]]},{"id":"f8d8fd72.0727","type":"delay","name":"Limit 1 email per day","pauseType":"rate","timeout":"5","timeoutUnits":"seconds","rate":"1","rateUnits":"day","randomFirst":"1","randomLast":"5","randomUnits":"seconds","drop":true,"x":948,"y":447,"z":"fa6ca080.05936","wires":[["1d4154b2.e2beab"]]},{"id":"1d4154b2.e2beab","type":"e-mail","server":"","port":"465","name":"","dname":"Send warning email","x":1198,"y":439,"z":"fa6ca080.05936","wires":[]}]

China Shenzhen Electronic Market & HopeRF Factory Visit

For the past two weeks I have been travelling out to the South of China from the UK via overland travel. I have always wanted to visit China but could not bring myself to justify the carbon impact of flying*. My journey took me from the UK to Moscow via European trains then the Trans Siberian Railway across Russia and Mongolia to China. It was a fantastic adventure, we broke up the travel by stopping off in various locations on route. I have posted a couple of blog posts on my personal blog accounting the journey.

Even though at OpenEnergyMonitor we do most of our manufacturing and assembly locally in the UK there are many components that are only possible to source in China e.g CT sensors, power adapters and RF modules. In fact most electronic components originate in some way from a factory in China. Even though we do our SMT assembly and PCB fabrication in the UK we still rely heavily on Chinese manufacturing. For heavy items like power adapters and CT sensors we purchase in bulk (pallet load) and ship via ocean freight rather than air cargo to reduce carbon footprint.

I wanted to visit China to experience the culture and see for myself the working conditions in the factories that supply some of the components we use. No doubt attempting to trace back every factory and company in a supply chain for a complex items such as electronic components is a big task, something large corporation (think Apple and Samsung) have struggled with. We have all heard the horror stories of overworked and under-age employees in Chinese electronic factories.

My epic train ride to China rolled me into the North of China and Beijing first. After being a tourist for a day and visiting the very 'great' Great Wall of China I took a fast train down to Shenzhen. This train was seriously impressive, cruising at a smooth 307 Km/hr. I was glued to the window watching countryside and cities larger than London that I had not heard of fly by. I was aware that China is home to many, many people however this was really evident looking out the window watching huge cities and row upon row of skyscrapers flash by. In every town town and city it seemed many more tower blocks were in the process of being built, there is no doubt that China is undergoing an economic boom. After 8hrs of fast train blur we arrived in Shenzhen, nicknamed together with it's neighbouring city Guangzhou as the ‘factory of the world’; it's almost certain that the laptop/tablet/phone you are using to read this was made in factories in these cities.

During my time in Shenzhen I visited the world's largest electronic component market and the HopeRF factory where the RFM12B and RFM69CW RF modules that we use are designed and manufactured. I didn't manage to visit the factory where our CT sensors are manufactured since this factory was located in the north of China, however I did post up some photos I was sent from inside the factory a while back.

Electronic component market in downtown Shenzhen (I'm pictured with the seller of encapsulated DS18B20 temperature sensors that we stock)

Visiting the electronics market in downtown Shenzhen was a fantastically crazy experience. It was amazing to see all types of components carefully organised under the glass counters. There is something satisfyingly tactile about being able to hold different types of connectors and switches to compare quality and dimensions and chat to the seller about the pros, cons and cost of each item. Assuming you could speak Mandarin shopping for components here would be a far more social experience than an online parametric search tool! Obviously prices for these components are significantly cheaper than in the West.

Before I started working in electronic manufacture I assumed (like I think many people do) that most electronic manufacture is performed by robots. This is mainly true for pick-and-place assembly, however there are many more manufacturing steps which require significant human effort such as thru-hole soldering, testing and final assembly.

I am happy to report that the HopeRF I visited was clean, air conditioned and all employees were at least the minimum age, paid at least the minimum wage and worked 8am - 6pm with a 2hr lunch / siesta break. Overtime is common but employees are paid accordingly. All employees I met seems happy, although I did happen to arrive just as they were leaving on their lunch break! On the wall in the corridor there was a notice board with photos showing various company employee group outings including activities such as hill walking, running, swimming and group dinners. I also noticed an employee suggestion box.

Hope RF Factory Visit

I did get a chance to speak to an engineer at Hope RF who is involved in the design of new modules. As I had presumed the RFM69CW using a more standard IC package is much more suited to reflow soldering and less susceptible to humidity ingression than the older RFM12B design that often used a 'black blob' IC package. Second photo down on the left shows a naked RFM12B before receiving it's 'blob' dressing! Interestingly I learned (and witnessed!) that each and every single module is hand tested before leaving the factory. Modules that fail the test are debugged by hand. I was told that they have no plans to halt manufacture of the older RFM12B modules as long as there is demand.

HopeRF factory in Shenzhen where RF modules are designed, manufactured & tested.

* Travelling via train emits 80-90% less carbon then flying [Source:].

The international 'safe' level of emissions per person is around 2T/yr to contain global temperature changes at or below 2 deg C which will 'hopefully' keep runway climate change and subsequent rise in sea levels at bay. Return fight from London to Málaga will emit 2/3T of carbon per person

6.5T to Auckland Australia or 2T to New York. [Source: Only Planet, Ed Gillespie 2014]

Using emonPi Offline: How to setup a WIFI Hotspot on an emonPi

This guide details how to setup a WIFI Hotspot using the Edimax USB WIFI adapter on an EmonPi or EmonBase to make it possible to connect directly to an EmonPi from a tablet or computer without the need for a router or internet connection.

The guide is based on Dave Conroy's guide here but also covers setting up a DHCP server rather than ethernet to WIFI bridge.

There are 3 pieces of software that need to be installed to get this to work:
  • hostapd – WIFI Hotspot
  • edimax version of hostapd
  • isc-dhcp-server – DHCP Server
1) Install dhcp server 

sudo apt-get install isc-dhcp-server 

2) Install Edimax version of hostapd

Either use precompiled binary or compile yourself:

Pre-compiled (update: does not seem to work with wheezy, use self compile see below)
sudo mv /usr/sbin/hostapd /usr/sbin/hostapd.bak
sudo mv hostapd /usr/sbin/hostapd.edimax
sudo ln -sf /usr/sbin/hostapd.edimax /usr/sbin/hostapd
sudo chown root.root /usr/sbin/hostapd
sudo chmod 755 /usr/sbin/hostapd

Compile yourself (recommended for wheezy, tested March16)

sudo apt-get install libnl-genl-3-dev libnl-3-dev
git clone
cd hostapd-rtl8188/hostapd
sudo make
sudo make install 

3) Configure /etc/network/interfaces

Open the network interfaces file to edit:

sudo nano /etc/network/interfaces

Replace content with:

auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet manual

#allow-hotplug wlan0
#iface wlan0 inet manual
#    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

iface wlan0 inet static

allow-hotplug eth1
iface eth1 inet dhcp

If required add bridge to bridge eth0 to wlan0 - although it's better to use NAT iptables forwarding since then we can still access pi via ssh (see below)

auto br0
iface br0 inet dhcp
bridge_ports eth0 wlan0
pre-up ifconfig eth0 up
pre-up ifconfig wlan0 up
pre-up brctl addbr br0
pre-up brctl addif br0 eth0
post-down ifconfig wlan0 down
post-down ifconfig eth0 down
post-down brctl delif br0 eth0
post-down brctl delbr br0

4) Configure /etc/hostapd/hostapd.conf
Open hostapd config file with:

sudo nano /etc/hostapd/hostapd.conf

Add the following lines to hostapd.conf (set SSID and password of your choice)





Manual start to test everything is working, you should see a Wifi network called 'emonPi':

$ sudo hostapd -dd /etc/hostapd/hostapd.conf

5) Configure /etc/default/hostapd

sudo nano /etc/default/hostapd



6) Configure /etc/dhcp/dhcpd.conf
Open dhcpd config file:

sudo nano /etc/dhcp/dhcpd.conf

Add the following to the end of the file:

lease-file-name "/home/pi/data/dhcpd.leases";
subnet netmask {
        option broadcast-address;
        option routers;
        default-lease-time 600;
        max-lease-time 7200;
        option domain-name "local";
        option domain-name-servers,;

comment out #option domain-name "";

#option domain-name-servers,;



7) Configure /etc/default/isc-dhcp-server

sudo nano /etc/default/isc-dhcp-server 

Remove the comment from DHCPD_CONF, DHCPD_PID and then set the INTERFACES to "wlan0" (including ""), see example below:

# Defaults for isc-dhcp-server initscript
# sourced by /etc/init.d/isc-dhcp-server
# installed at /etc/default/isc-dhcp-server by the maintainer scripts
# This is a POSIX shell fragment

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).

# Path to dhcpd's PID file (default: /var/run/

# Additional options to start dhcpd with.
#       Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".

8.) Setup NAT forwarding to bridge eth0 the wlan0 while still allowing us to access the Pi via SSH (pure network bridge does not)

To set this up automatically on boot, edit the file /etc/sysctl.conf and add the following line to the bottom of the file:


Second, to enable NAT in the kernel, run the following commands:

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT

If bride is also required to eth1 (for 3G dongle) add:
sudo iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
sudo iptables -A FORWARD -i eth1 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
sudo iptables -A FORWARD -i wlan0 -o eth1 -j ACCEPT

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"

Now edit the file /etc/network/interfaces and add the following line to the bottom of the file:

up iptables-restore < /etc/iptables.ipv4.nat # This did not work for me I had to add entry to rc.local (see below)

8) Edit /etc/rc.local

sudo nano /etc/rc.local

Add before exit 0 the following lines to tell the wlan interface to use ip address and then start the isc-dhcp-server:

sudo iptables-restore < /etc/iptables.ipv4.nat
sudo ifconfig wlan0

sudo service isc-dhcp-server restart
sudo iptables-restore < /etc/iptables.ipv4.nat

9) Start services at boot

sudo update-rc.d isc-dhcp-server defaults
sudo update-rc.d hostapd defaults

Thats it restart your emonpi/emonbase to finish and then connect to network emonPi with password: raspberry

11) Add a Real Time Clock (RTC)
When running an emonPi in offline mode we recommend adding a hardware RTC to ensure the system time is always correct. See emonPi Wiki:

Hardware RTC

Useful blogs, guides and forum threads that I used to work out how to set up the above: