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Short talk given at #OSHUG (Open Source Hardware Users Group) event #26 in London 16th May 2013. Quick overview of the OpenEnergyMonitor project and how we use wireless sensors to collect data. Practical examples of home temperature monitoring cross referenced with SAP calculator building fabric modelling, heat pump monitoring and bee hive temperature monitoring!
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Low Power Wireless Sensors
Glyn Hudson @openenergymon OSHUG #26 16/05/13
...and their role in helping us build a sustainable future
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Open-source sustainable technologies
Technology that empowers us to participate in creating a future where we live within ecological limits.
openenergymonitor.org
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Sustainable EnergyTools to help us work towards sustainable energy in a way that adds up.
Energy Stacks based on DavidMacKay's book: withouthotair.comTrystan's Stack 2012
Only 17% Sustainable Energy
2030Target*
2012 UK Average
2012 Trystan
*CAT zerocarbonbritain.com/
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OpenEnergyMonitor.orgOpen-source energy monitoring
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The OpenEnergyMonitor System
6http://openenergymonitor.org/emon/emontx
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Raspberry Pi
http://openenergymonitor.org/emon/emonbase/raspberrypi
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An open-source web-app for processing, logging and visualising energy, temperature and other environmental data
●Open-source, downloadable and installable on your own server (e.g RaspberryPi)
●Specifically designed with processing and visualising energy data in mind.
● Written in php, mysql, javascript and jquery
● Follows MVC architecture
emoncms.orgopenenergymonitor.org/emon/emoncmsgithub.com/emoncms
Visual Dashboard Editor
Drop & drop, customisable graphs, re-sizeable widgets, buttons and live feeds
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Contents
Technology of a wireless node- Wireless considerations - Wireless Module Hardware- Mircrocontrollers- Low power optimisation - Battery Life Estimation
Practical Examples - Home Temperature and Energy Monitoring- Home energy modelling & simulation - Heat Pump Monitoring- Bee Hive Temperature Monitoring
The Future - Current Hardware Prototypes
Live Demo?
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Wireless Considerations – ISM bands
● Industrial Scientific and Medical
● Licence exempt
● 433Mhz, 915Mhz, 868Mhz and 2.4GHz
● Commonly used for low power, low range wireless transmission
● Applications need to be interference tolerant
● 433/868/912MHz - Restricted duty cycle <10%
● Lower frequency's have less free space attenuation and better propagation – better range
2.4GHz 433MHz / 868Mhz / 915Mhz
Wifi Doorbells
Bluetooth Security Systems
Zigbee Cordless telephones
Weather Stations
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Low Power Wireless Modules
RFM12B (HopeRF)
SRF (Ciseco) TI - CC1110
XBEE (Digi) NRF24L01+ (Nordic Semi)
Interface SPI Serial / SPI Serial SPI
Freq 868 Mhz 868 Mhz 2.4GHz 2.4 Ghz
AES Encryption
NO YES YES NO
Power Supply 2.2V - 3.8V 2.0V - 3.6V 2.1V – 3.6V 1.9 – 3.6 V
Rx / TX Power 14 / 23mA 20 / 36.2mA 35/ 38mA 11.3/13.5ma
Sleep mode 1 132.2ua @ 2.6v
26uA
Sleep mode 2 0.3uA 0.2uA @2.6v <1uA <1uA (900nA)
Price (inc VAT) x1 May 2013
£4.79 £11.52made in UK!
£17 £4
Regulatory Approval FCC/ETSI
No In Progress Yes No
http://blog.homelabs.org.uk/wireless-connectivity/
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Microcontrollers
● Ciseco RFu – ATmega328 MCU plus SRF / RFM12B radio in XBEE form factor
● Designed & made in UK
ATmega328 with Arduino Uno bootloader
+ commonly used+ easy to develop for using Arduino IDE+ easy to upload code and debug+ active community- not the most low power option, but not too bad:
6.8mA running @ 16Mhz 3.3V 4.6uA while sleeping
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emonTx / emonTx Arduino
ShieldEnergy monitoring
node
emonTx Low Power Temp
Semi – populated emonTx with 2 x
AA and DS28B20 temperature
sensor
NanodeRFWeb-connected base station -
Arduino clone with ENC28J60
Ethernet and RFM12B wireless
onboard
RFM12PiRFM12B wireless
Raspberry Pi expansion board. Uses Pi's Serial
UART GPIO pins
OpenEnergyMonitor Modules – ATmega328 & RFM12B wireless
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http://nathan.chantrell.net/tinytx-wireless-sensor/
ATtiny84 Based Nodes
x
http://harizanov.com/wiki/wiki-home/funky/
http://jeelabs.net/projects/hardware/wiki/JeeNode_Micro
+ Cheaper and smaller than ATmega328+ easily run off internal 8Mhz oscillator+ Can use Arduino IDE (with some tweaks)
- Does not support hardware serial- Requires ISP programmer to upload code- Harder to debug
Examples with DS18B20 temperate sensor and DHT22 Humidity Sensor
TinyTX – Nathan Chantrell
Funky Sensor – Martin Harizanov JeeNode Micro – JCW JeeLabs
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Low Power Ticks - software
● AVR sleep mode
– Disable all unneeded functions (e.g ADC) and put processor to sleep
– Reduce current consumption from 6.4mA to 4.6uA
● Requires internal watchdog timer or external interrupt to wakeup
● Radio should also be put to sleep
– if not needed for receiving packets
– 14mA (Rx) / 23mA (Tx) reduced to 0.3uA when sleeping for RFM12B
* Running @ 16Mhz 3.3V - 6.4mA
* SLEEP_MODE_IDLE -the least power savings (2.8mA
* SLEEP_MODE_ADC
* SLEEP_MODE_PWR_SAVE
* SLEEP_MODE_STANDBY
* SLEEP_MODE_PWR_DOWN -the most power savings (4.6uA)
https://github.com/jcw/jeelib/blob/master/Ports.cpp
http://jeelabs.org/2011/06/26/current-measurements/
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Simple Low Power RFM12B example
● Simple sketch to send out an ever increasing integer once every minute
● Estimated battery life of 3 years on a single 1300mAhr 3.3V LiPo battery – ATmega328 @ 16Mhz, approx average current draw <57uA
http://jeelabs.org/2013/04/18/9-50-days-and-counting/
JeeLabs Real word test, 2.5 years and still going!
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Battery Life Estimator Tool
http://oregonembedded.com/batterycalc.htm
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Low Power Tricks - Hardware
● Turn off sensor in-between reads – e.g. DS18B20 VCC powered from MCU digital I/O
● Don't use a voltage regulator – Eliminate quiescent current draw: MCP1702 1.6 uA , LM7805 5-8mA!)
● DC-DC boost converter ● Disable ATmega BOD – Arduino default is 2.6V (Brown
Out Detection)
● Slow down – ATmega328 can work down to 1.8V with 4Mhz clock – default is 16Mhz
● Energy harvesting – Mini solar PV
– Battery less operation
– Super capacitor
– PFET to disable RFM12B at startup
Energy consumption of RFM12B packet transmission with ATtiny84. Duration 5.7ms,
average: 10mA, peak 25mA
http://jeelabs.org/2010/09/03/jeenode-goes-solar/
http://harizanov.com/2013/04/scope-screenshots/
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Practical Example – Home Temperature Monitoring
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Home Heating Energy Input & Temperature Monitoring
January 2011 - April 2013
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Real World Monitoring Data
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Heat Pump MonitoringJohn Cantor, heat pump consultant
● Remotely monitor heat pump performance
● Identify problems
● Optimise control by providing feedback
www.heatpumps.co.ukhttp://openenergymonitor.org/emon/applications/heatpump
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RF Link
Ambient Temp probe
Solar PV
Battery
Core temperature probe
Winter 2010
Bee Hive MonitoringClive Hudson, Meirionnydd Bee Keepers
http://openenergymonitor.org/emon/beehive/v2
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A 'normal' bee temperature week
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The Future - Hardware Prototypes
emonTHTEMPERATURE & HUMIDITY
open hardware
emonTxV3
energy monitoring node
openenergymonitor.orgopen hardware
● SMT design● Enclosures
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Thank you.