Not all USB power supplies are created the same

We recently ordered a load of cheap (~£1.50) USB power adapters such as this one and started to notice problems, nanode missing posts, rfm12 problems, emonGLCD crashes and so we ordered another two: one branded htc another ~£4 unbranded one which work well. The more expensive unbranded one specifically outlined that it was better quality in the ebay description.

Using the sampler program we can shed some more light on whats going on here. So first here is the cheap USB power supply:

As you can see a lot of noise, a standard deviation of 6.4.

With the unbranded more expensive adapter the standard deviation is reduced to 1.5!

The branded htc adapter is pretty similar at 1.6

USB power direct from a laptop, should be as good as it can get. A standard deviation of 1.2

Conclusion: its worth ensuring that the power adapter is a good quality one in order to get consistent performance from the hardware.

Nanode Applications weekend

We have just come to the end of two great days in London at the nanode applications weekend, an un-conference style event at the Center for Creative Collaboration CC4C bringing people together to share and explore what can be done with the nanode an open-source Arduino like board with built in web connectivity developed by Ken Boak.

Over the weekend we presented our work on our end-to-end open-source energy monitoring system, comprising of the emonTx  wireless transmitter unit, emoncms energy visualisation web-app and the emonGLCD display. Download a copy of our slides

As well as presenting we attended the event to hear about what other people are working on.

Here are a few of the highlights for us of the weekend:

  • Andrew Lindsay’s arduino sketch upload to nanode over Ethernet using TFTP.  Fantastic, glimpse of the future?
  • Nick Boyle’s home monitoring with twitter and iphone notifications (partial documentation) - he gets a notification on his phone triggered by a certain energy event in his house!
  • Great to meet Franck Oxener a long time member on OpenEnergyMonitor who came all the way from the island of Texel, Northen Netherlands.

It was fantastic to meet lots of enthusiastic people all working on similar things. Since we are based in the mountains of North Wales this is not something we do on a regular basis. London can even be beautiful, on Saturday night we were treated to a wonderful rainbow display.

Project development

As of today 285 people have signed up to be developers / contributors / users on OpenEnergyMonitor. This is fantastic, It's great to see the project expanding and becoming more collaborative. Activity on the forums has been steadily increasing, they are now a great place to discuss ideas, share problems and showcase what you have been working on. 

Thank you to everyone who has signed up and contributed to the project. 

A large number of people come with a large number of skills. We have encouraged people to write a little bit about themselves and their interest in the project when they sign up. Until now the only way to access this information was to click on each user individually in the developer section on the right hand side of the page. We now created a page to allow easy access to user profiles. This should make it easier for people with similar interests and working on similar projects to connect with each other and collaborate. The new page can be accessed by clicking on the little more link on the developers section of the right hand side of the page. 

New user profile page
We have taken this a step further by installing a messaging system which will allow users to message each other directly. Just click on a users profile then 'send this user a message' link. The messaging system is very new, shiny and largely untested. Please report any problems. 

New messaging system 

I have been working improving the emonTx design and writing firmware examples.
We are working towards opening an online shop in the next few months...exciting times! In the meantime if you are keen to get your hands on an emonTx please contact me at [email protected] or message me using new OpenEnergyMonitor messaging system.

emonTx open-source wireless energy monitoring node

Trystan has been working on documentation and improving the code for emoncms to make it more modular, easier to understand and build upon.

Follow us on twitter for all the latest developments from OpenEnergyMonitor labs.

Cheap AC transformers are no good

The Open Energy Monitor uses an AC transformer as a voltage sensor, but the choice of this transformer can influence the accuracy of your monitor.

Jean Claude from JeeLabs (brilliant engineer BTW) investigated the difference between a bad and a good AC transformers and here are the results in images:

1) Bad quality transformer:

2)Better quality transformer:

You can read his complete post on his blog: JeeLabs Daily Weblog.

Twitter age

OpenEnergyMonitor has joined the twitter age. Follow us to keep up with current developments, find out what we'r currently working on and join the in the conversation.

How we envisage emonTx being used

Many if you might be thinking what is our motivation behind the developments at OpenEnergyMonitor and how we see our designs being used. 

Firstly we believe open-source is a better way of doing things, it is a way in which people can get involved in developing and making technology and build on the work of others. The OpenEnergyMonitor hardware builds upon the Arduino open-source micro-controller platform. 

Taking the recently released emonTx as an example; we see the design being used in two ways: 

  • For the enthusiast/hobbyist/maker/student: to be able to easily build an open-source monitoring system. They will assemble it themselves and customise it for their needs and hopefully develop some cool applications. To help them get going we will provide good documentation and code examples. Think along the lines of Arduino, Adafruit and JeeLabs. We hope that user developments will feed back to OpenEnergyMonitor. We are considering setting up an OpenEnergyMonitor online shop to sell the PCBs and kits. We have created a feedback form to try and gauge interest from the community. 
  • For commercial use: The emonTx could be used in a professional large scale energy monitoring systems. Trystan Lea (founder of openenergymonitor) and I are in the process of setting up a business to offer energy monitoring services to organisations and businesses in our local area (see We are currently working on a community energy project which will also be a pilot test for our monitoring system see: We are happy for and very much encourage other people to use our designs in a commercial setting as long as they attribute OpenEnergyMonitor and make any resulting designs available under the same open-source license; thus allowing others and us to benefit. 
The same reasoning also applies to all other content on this site. 

To read more about open-source at OpenEnergyMonitor please click here.

A prototype OpenEnergyMonitor  monitoring system (emonTx + NanodeRF)
being exhibited at a recent sustainability event

emonTx feedback form

Here at OpenEnergyMonitor we are trying to decide how best to engage with interested parties and to promote exciting open-source development. 
With our launch of emonTx we are considering opening an online shop to sell emonTx PCB's / kits. 
We hope that making emonTx PCB's available at a reasonable cost will help people to quickly get an open-source energy monitor up and running. Leaving more time free for development.
I've created a feedback form on the website to try and gauge interest. Please could you take a few moments to fill it in. 
Thanks a lot.

Meet the emonTx

At OpenEnergyMonitor labs we have been working on designing a unit that makes building an open-source energy monitor easier. We wanted a unit that is cheap enough for a small home monitoring system yet powerful enough for a large system. We also wanted it to be easy to install and small enough to look pretty!

Two months ago Trystan announced a software milestone with the release of emoncms. Today marks another milestone for us, a hardware milestone with the release of emonTx.

emonTx stands for Energy-Monitoring-Transmitter. It's a small wireless energy monitoring node designed to take inputs from multiple CT sensors, optically from a pulse-output utility meter and from multiple one-wire temperature sensors. It is designed to be powered by 2x AA batteries or 5V USB.

  • Electricity consumption monitoring  
  • Renewable generation monitoring 
  • Heatpump monitoring 
  • Water and gas monitoring (from pulse output meter) 
  • Temperature monitoring 
  • Large scale monitoring - up to 26 emonTxs can potentially transmit to a single base station

emonTx PCB with bare minimum of components
for single channel CT monitoring

The unit has been designed to fit nicely in a case

Sneak peak inside 

emonTx is based on the Atmega328 and is fully compatible with Arduino IDE.   
The design is based on the JeeNodeV5 design, is fully open-source and is designed for easy expandability and compatability with JeeLabs shields.
The firmware is still in development, so far we have an emonTx monitoring a single CT channel and transmitting the data to a base station (Nanode + RFM12 breakout) where it is posted online to emoncms. We hope to release a beta version of the firmware in the next few weeks. 
For more information see the emonTx documentation page

Snowdonia build April 2011

Now that the dust has settled, kitchen cleaned and toilet fixed it seems like a good time to look back on the last week.

Firstly, thanks to Ken Boak, Samuel Carlisle and Matthew Gaffen for making the trip up here to OpenEnergyMonitor HQ in North Wales for the 2nd ever Snowdonia build event. We had a great time and look forward to a reciprocal event in London.

The Team (minus Ken behind the camera)

The idea behind these build sessions is to get together a group of similar minded 'techies' together for a week, add in beer, food and plenty of enthusiasm and have some fun developing cool open-source technology.
Morning planning meeting in the sun

The common theme of last weeks development was sustainability and how open-source technology can be used to help people learn about and reduce their energy consumption and move to energy generation.

The Lab 2010  
The Lab 2011
A rough wiki page has been made here to try and document the weeks developments.

Ken's great blog posts detail day by day developments: 
Mats blog post: snowdonbuild

An interesting development for us at OpenEnergymonitor was Sam giving us a tutorial of how to use Github to share and keep track of open-source code. Over the coming months we hope to shift more of our code to the site. Click here to access the Github group. At present emoncms is the only fully implemented code on Github.