Home whole house Energy Monitor System
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.
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.
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.
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.
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 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.
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