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Open-source tools for energy monitoring and visualisation
Updated: 11 min 51 sec ago

Energy Display Options...

Thu, 19/03/2015 - 12:24
Sadly as of last week we have run out of emonGLCD kits in the shop and have decided to discontinue the emonGLCD for the moment. Preparing the through-hole kits is very labour intensive and the time and skill required to solder assemble is lagging behind our other pre-assembled SMT units.

Work has begun on a SMT pre-assembled replacement (see forum thread). However this would probably require significant investment in injection moulding tooling and commitment to high volume production. This would not would be a problem if we were sure on the design. However, I'm not sure if a standalone display is the right avenue to go down...

I am aware there that there is certainly value in an 'always on' wall mount / coffee table energy display. Being able to easily glance at the display throughout the day when your home really does remind me to switch off lights and appliances when not in use. As well as checking everything is turned off (base level energy consumption) when leaving the house. An always on display gives users a 'feel' for how much energy various devices use as the display increases or decreases in real-time as a device is switched on or turned off.

The future is mobile, everyone has at least one mobile device and increasingly as these devices are upgraded there are a large number of perfectly working just a bit slow older devices which could easily be given a second life as an energy display. This could help reduce the number of devices which end up being recycled or worse put into landfill, therefore helping to save energy in more ways the one! Old second hand Android phones or tablets can be picked up on Ebay for less than we could make an emonGLCD!

I recently repurposed an old Nexus 7 tablet (2012 model) with a cracked screen as a home energy display displaying Emoncms MyElectric. I installed an app to keep the screen on all the time when plugged in charging. The tablet uses 5W of power. An added advantage of using a mobile device as an energy display is they are 'mobile'! The display can easily be moved around the house to support investigation power consumption of various appliances.

Much work could be done on the software side to make a really nice packaged Android app for Emoncms which would support an energy display mode, useful features might be:

  • Intelligent screen-on-off e.g the display could turn off at night, when energy falls to base level consumption indicating the house is unoccupied 
  • Using the tablets motion / proximity / light sensor to sense movement to turn screen on-off
  • If device has an AMOLED display only certain pixels could be lit up to save power, like on the Moto-x Active Display 
  • Auto start at startup and full screen mode 
  • Home screen widget to be used if user does not want to decicate a devices solely as an energy display or to be placed on current mobile home screen to enable quick checking of power consumption / temperature etc when out and about.    


Emoncms MyElectric on Nexus 7 with cracked screen
A super low power alternative could be to use an old e-reader with an E-ink display. Here's Emoncms MyElectric running on a hacked Nook Touch.

Emoncms MyElectric on Nook TouchHead over to the forums and let us know what you think...
Discussion Thread: http://openenergymonitor.org/emon/node/10353
Categories: Blog

Real World emonTH Battery Life

Fri, 27/02/2015 - 11:07



The battery on my home emonTH Temperature & Humidity Node has just died for the second time in 14 months. Each set of batteries lasted exactly 221 days (7 months and 9 days)! The 2 x AA alkaline battery voltage started at 3.1V and the emonTH stopped working just after the voltage dropped below 1.2V (final dying breath was at a battery voltage of 0.8V!).  The two AA batteries installed were low cost alkaline batteries unbranded from e-spares. Battery life would not doubt be longer from some quality cells. 
I recommend using rechargeable alkaline batteries if possible in the emonTH, for least environmental impact. See my previous posts on emonTH battery selection and power consumption optimisation
My emonTH had a DHT22 temperature and humidity sensor connected and was set to the default post rate of one minute in-between samples. The unit was running V1.0 firmware (the firmware is now at V1.2, there have been a couple of minor battery life improvements). 
It's very impressive how the DC-DC boost converter onboard the emonTH continues to boost the depleting battery voltage to 3.3V, using this method allows the battery to be drained much further than powering the unit directly. 




Categories: Blog

RFM69CW Power Consumption

Mon, 23/02/2015 - 14:33
Following on from my post on RFM12B power consumption here's the same measurements for the RFM69CW (see RFM69CW intro blog post).

Current consumption was measured in the same way as explained in the RFM12B post back in July 2013. Voltage drop was measured across 10R current shunt resistor.

A fully populated emonTx V3.4 with a 433Mhz RFM69CW running discrete sampling code with a single CT connected was used in the test. The V3.4 was powered directly with 3.3V DC from bench PSU.

emonTx V3.4 with RFM69CW Test Setup
Test setup illustration

Test BenchPlease excuse my photos of the scope traces rather than screen captures, for some reason the USB socket on the scope did not seem to be working today :-(

Full sample and RFM69CW transmit trace capture
When an AC-AC adapter is not connected the emonTx goes to sleep in between readings. The above current trace shows the ATmega328 waking up for 295ms to sample from one CT channel the spike at the end is the RFM69CW transmitting. The trace below is a zoomed in capture of the RFM69CW transmission and LED. 
RFM69CW transmission current consumption The current trace above shows the RFM69CW transmission: 33mA @ 3.3V (109mW) for 4ms. The current spike at the end (up to 39mA) is the emonTx LED. In this test the emonTx was running the standard discrete sampling firmware transmitting a JeeLib packet structure with six integers. Since we were only sampling from one CT four out of the five integers will be zero. 
This equates to a 15 bytes payload plus 9 byte overhead @ 48kb/s. See JeeLib packet structure

In comparison I measured the RFM12B to consume 25.5mA @ 3.3V (84.2mW) for 3ms.
My measurements pretty much agree with the datasheets, here's a comparison table compiled by Low Power Labs:

Even though the RFM69CW does consume more power while it's transmitting it does have a lower sleep consumption than the RFM12B. This increased transmission power should result in an increased transmission range.
I've started a forum thread for discussion: http://openenergymonitor.org/emon/node/10210
Categories: Blog

Introducing emonPi: Raspberry Pi Based Energy Monitor

Fri, 13/02/2015 - 10:56





The emonPi has been developed with input from our community merging the monitoring unit and web-connected base station into a single easy to install and setup energy monitoring solution.

The emonPi is fully open source hardware and software. It's been designed for maximum hackability and customisation being built on a fusion of two popular open source hardware platforms Arduino and Raspberry Pi. emon Pi Features 
  • Two channel CT monitoring with AC sample input 
  • RJ45 DS18B20 on-wire temperature bus to allow many temperature sensors to easily be added using a RJ45 breakout board for heatpump monitoring applications 
  • PWM and IRW I/O's on RJ45 
  • Status LCD
  • Compatible with RaspberryPi model A, model B, model B+ and Pi 2 
  • Option for RFM12B / RFM69CW with SMA antenna to receive or transmit data from other sensor nodes
  • OOK (on-off keying) transmitter footprint for controlling remote plugs etc. 
  • ATmega328 with ability to remotely upload sketches vis Raspberry Pi Serial 
  • Open-source hardware, firmware and software 
  • High quality custom made, wall mountable enclosure

Development has been documented in an ongoing open forum thread: http://openenergymonitor.org/emon/node/3937

See G+ album for more photos: https://plus.google.com/b/114424977493521882459/photos/+OpenenergymonitorOrgpage/albums/5999656723837107313

 LCD demo:




Please join in the emonPi's open-development forum thread if you have any ideas of thoughts to contribute:
http://openenergymonitor.org/emon/node/3937#comment-21865


Categories: Blog

Introducing RFM69Pi V3 Raspberry Pi Expansion Board

Tue, 10/02/2015 - 11:37

RFM69Pi on Raspberry Pi B+, also compatible with Raspberry Pi Model B and Pi2

RFM69Pi - just like RFM12Pi but with upgraded radio and more I/O available



The RFM69Pi is a minor update to the popular RFM12Pi Raspberry Pi Expansion board. It adds support for the RFM69CW RF module as well as breaking out as much I/O as possible from the ATmega328 to open up the options for greater connectivity and compatibility. The RFM69Pi was developed with help and inspiration from Nanode RF designer Ken Boak, together we are working on a relay heating controller board using the RFM69Pi. 
The RFM69CW is backward compatible with RFM12B, see blog post introducing the module. From an end user's perspective there should be no difference when using the RFM69Pi over the RF12Pi apart from a new input called RSSI (Received Signal Strength Indication) appearing in Emoncms. 
You must be running the latest pre-build SD card image emonSD-26-02-15.img (now shipping) or emonHub must be updated manually to the latest Development branch version to enabled auto detection of the faster baud rate used by the RFM69Pi (38400 as opposed to 9600 on the RFM12Pi), and RSSI value handling. 
If you're running pre-built SD card image emonSD-13-08-14.img or earlier then emonHub can be updated by running:

$ sudo service emonhub stop

$ cd emonhub

$ git pull 

$ sudo service emonhub start 

check log for errors 

$ tail /var/log/emonhub/emonhub.log


The RFM69Pi is now shipping from our online shop
http://shop.openenergymonitor.com/base-stations/

RFM69Pi Technical Docs Wiki Page:
http://wiki.openenergymonitor.org/index.php?title=RFM69Pi_V3

Open-Source Hardware Design:
https://github.com/openenergymonitor/Hardware/tree/master/RFM2Pi/board/RFM69Pi_V3.1

RFM69Pi Default Firmware:
https://github.com/openenergymonitor/RFM2Pi/tree/master/firmware/RFM69CW_RF_Demo_ATmega328
Categories: Blog

An open source hourly zero carbon energy system model

Fri, 06/02/2015 - 02:05
I've been doing some work recently with Philip James from the Centre for Alternative Technology on developing a set of open source zero carbon energy system models based on ZeroCarbonBritain that visualise in a javascript based web page application how energy demand can be supplied by a variable renewable energy supply using a mix of storage technologies. You can create your own scenarios, choosing how much wind, solar, storage technologies etc are used.

Its still work in progress but the models we have built so far are now online and can be explored here:
http://zerocarbonbritain.org/energy_model

The source code is all available there too as well as the original ZeroCarbonBritain spreadsheet model: https://github.com/philJam/energymodel

Visualising hourly surplus and shortfall:

 
Visualising battery, hydrogen, synthetic liquid and gas store levels:

This builds partly on findings and questions raised from our earlier work on the Snowdonia household energy study: here;http://openenergymonitor.blogspot.co.uk/2014/11/snowdonia-household-energy-study.html


The aim will be to extend that analysis to look at the amount of renewable energy and energy storage required to supply the energy demand after implementing measures like building insulation/retrofit, heatpumps and electric transport.


I find it very interesting looking at how all of these different elements can come together to create a zero carbon energy system, to understand better the relevance of different solutions. With a framework like this it becomes more possible to put ideas like smart electric car charging or excess pv diversion to immersion heaters and battery stores in context, to get a better idea of actually how much effect different solutions can have.
Categories: Blog

Pre-built heatpump dashboards

Tue, 03/02/2015 - 19:07
I've been experimenting with the idea of a pre-built heatpump dashboard - a bit like the myelectric module for home energy monitoring.

The initial concept is up on emoncms.org under the Extras > heatpump tab. The heatpump fan turns in relation to power input a bit like the winderful windturbine.

Configuration is by naming convention at the moment, the dashboard looks automatically for feeds named or containing the words: heatpump_power, heatpump_kwh, heatpump_flow_temp, heatpump_return_temp, ambient_temp and room_temp, using these if present.

 

Next I plan to extend this for heatpump monitors that also monitor either flow rate or heat output in order to show COP information including a daily power input/ heat output bar graph below the heatpump graphic.

I've been doing this work with John Cantor who is using the OpenEnergyMonitor system for heatpump monitoring.

The source code for this can be found here if youd like to try it on your own install, just drop the folder heatpump into your emoncms modules directory: https://github.com/emoncms/development/tree/master/Modules/heatpump
Categories: Blog