Whole House Energy Monitor

Home whole house Energy Monitor System

EMON Pi in enclosure with RFM12Pi wireless board

emon-Base in enclo­sure with RFM12Pi wire­less board

A home ener­gy mon­i­tor­ing and man­age­ment sys­tem using a com­pact (emon-Tx) mea­sure­ment and trans­mit­ter board, along with a Raspberry Pi based (emonBase) base sta­tion, and sev­er­al oth­er wire­less mod­ules (emon-RH). 
The sys­tem is based on the OpenEnergyMonitor project, whose founders and lead devel­op­ers are Glyn Hudson and Trystan Lea.  It start­ed as a UK based project to “devel­op open-source ener­gy mon­i­tor­ing tools to help us relate to our use of ener­gy, our ener­gy sys­tems and the chal­lenge of sus­tain­able ener­gy” and has been adapt­ed to worl­wide use.

A few years back I used some of the OpenEnergyMonitor cir­cuit­ry and code for the DIY OpenEVSE ver­sion 4.0 board, to mon­i­tor pow­er used in charg­ing elec­tric vehi­cles. I am now tack­ling my entire house includ­ing solar pro­duc­tion.

Pair of compact EMON-TX boards
Pair of com­pact emon-Tx boards

The com­pact emon-Tx boards are open hard­ware, with the designs released under the Creative Commons Attribution-Share Alike 3.0 Unported License, and use an ATmega328 micro­con­troller. The board uses a Hope RFM12B 433Mhz radio mod­ule for com­mu­ni­ca­tions, and includes 4 ana­log ports for mea­sur­ing cur­rent using cur­rent trans­form­ers (CT’s). The board also has a 1‑wire port for con­nect­ing tem­per­a­ture sen­sors, and cir­cuit­ry for mea­sur­ing AC line volt­age thru a step­down trans­former. There is also an input for pulse count­ing using com­pat­i­ble pow­er meters.

OpenEnergyMonitor compact EMON-TX 3.2 board
OpenEnergyMonitor com­pact ver­sion cir­cuit board emon-Tx ver­sion 3.2

I designed these boards sev­er­al years ago based on the emon-Tx ver­sion 3.2, using a Ciseco RFu mod­ule which is now obso­lete. The mod­ule includ­ed an area for attach­ing a Hope RFM12B or RFM69CW radio mod­ule. I do not rec­om­mend this mod­ule for new designs.
If I were to redesign this board I would most like­ly go with a Teensy 3.2 mod­ule and sep­a­rate RFM69CW radio mod­ule due to the high­er ADC res­o­lu­tion and pro­cess­ing pow­er of the Teensy 3.2 mod­ule.

I am using two com­pact emon-Tx mod­ules in my sys­tem. One will be ded­i­cat­ed for col­lect­ing solar pow­er infor­ma­tion, and the sec­ond mod­ule will mea­sure main util­i­ty pow­er and air con­di­tion­er pow­er usage in two sep­a­rate loca­tions.
The emon-Tx boards acquire volt­age wave­form and RMS cur­rent data, and then process­es that data as Real Power for each of the con­nect­ed CT chan­nels. Channel pow­er along with AC volt­age, option­al tem­per­a­ture and pulse count is then trans­mit­ted to the emon-Base base sta­tion typ­i­cal­ly once every 10 sec­onds.

OpenEnergyMonitor emonTH temperature and humidity sensor and transmitter module
emonTH tem­per­a­ture and humid­i­ty sen­sor and trans­mit­ter mod­ule

I am also using an emon-TH, tem­per­a­ture and humid­i­ty mod­ule that I pur­chased direct­ly from the OpenEnergyMonitor Store. It runs off of two AA bat­ter­ies and uti­lizes the same Hope wire­less mod­ule onboard. There are sev­er­al options avail­able for this mod­ule such as an exter­nal tem­per­a­ture sen­sor, with or with­out the humid­i­ty, with or with­out the inter­nal tem­per­a­ture sen­sor, or an exter­nal pow­er meter pulse count sen­sor. Battery life should be around 8 months using the inter­nal tem­per­a­ture and humid­i­ty sen­sor and trans­mit­ting every 60 sec­onds with good qual­i­ty bat­ter­ies.

emon-Base station using a Raspberry Pi and wireless module
emon-Base sta­tion using a Raspberry Pi and wire­less mod­ule

For the base sta­tion I am using a Raspberry Pi 2B with an OpenEnergyMonitor RFM12Pi V2 plug-in mod­ule, in an Adafruit enclo­sure. The RFM12Pi V2 mod­ule was pur­chased direct­ly from the OpenEnergyMonitor Store. I had built a func­tion­al RFM12Pi V1 mod­ule sev­er­al years ago, but it is no longer sup­port­ed with the cur­rent soft­ware.
I have mod­i­fied the Adafruit Pibow case a bit to improve air­flow and added a hole in the top plate for the wire anten­na. I also added heat sinks on the proces­sor and net­work IC’s as this unit will be on 24/7.
The base sta­tion col­lects data from the emon-Tx and emon-RH mod­ules and for­wards sen­sor data to a remote emon­cms, and/or host emon­cms local­ly on the Raspberry Pi. Acting as a serv­er, record­ed data is view­able via a LAN or option­al WiFi, thru a con­nect­ed web brows­er. The Raspberry Pi runs a mod­i­fied ver­sion of Debian Raspbian Jessie Lite, a pre-build SD card image is avail­able from OpenEnergyMonitor on GitHub.

emoncms solar example with data captures from past week
emon­cms solar exam­ple with data cap­tured from past week.

Emoncms is a pow­er­ful open-source web-app for pro­cess­ing, log­ging and visu­al­is­ing ener­gy, tem­per­a­ture and oth­er envi­ron­men­tal data. It is the inter­face used to visu­al­ize the data from all the emon sen­sors.

Solar monitor emon-Tx box installed next to solar breaker panel
Solar mon­i­tor emon-Tx box installed next to solar break­er pan­el.

Due to the radio dis­tance I end­ed up mount­ing the Solar emon-Tx flat to increase the coun­ter­poise ground plane area as much as pos­si­ble. I used a 433 MHz RPSMA 1/4 wave­length anten­na from Linx Technologies. The sig­nal strength is good, with a trans­mit dis­tance about 90 feet and pass­ing thru 5 walls.

I high­ly rec­om­mend pur­chas­ing boards and mod­ules direct­ly from the OpenEnergyMonitor Store, unless you need to design for a very spe­cif­ic foot­print or need. Even though I enjoyed build­ing sev­er­al of the mod­ules myself, I could of had a work­ing sys­tem two years ago at near­ly the same cost.

emon-Tx Compact V3.2–1 board files

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