The emonPi is an open-hardware Raspberry Pi and Arduino based web-connected energy and environmental monitoring unit.
The emonPi energy monitor has been designed with community input to be easy to setup and install while still retaining maximum hackability and customisation for many different types of applications: home energy monitoring, solar PV monitoring, heat-pump monitoring and temperature & humidity monitoring.
The unit will be beautifully enclosed in a robust wall-mountable extruded aluminium enclosure designed and manufactured in the UK by our partners Lincoln Binns. Aluminium was chosen as unlike acrylic or ABS plastic it can be 100% recycled at end-of-life.
With a connection to the web via WIFI or Ethernet the emonPi will not just be a tidy bit of standalone hardware. The data it collects is posted real-time to Emoncms, our powerful open-source web-app, for processing, logging and visualising. Emoncms can be run locally on the emonPi itself, your own server, or you can use our free hosted service.
The emonPi design is the cumulation of 6 years of collaborative development by the OpenEnergyMonitor team.
Home Energy Monitor
In the most basic application the emonPi can monitor up to two single-phase AC circuits with plug-and-play setup, using clip-on current sensors (CTs).
An optical pulse counting sensor can be connected to the emonPi RJ45 Aux I/O connection for interfacing with utility meters.
An additional AC-AC plug-in power adapter can be used to provide the emonPi with an AC voltage signal to enable calculation of more accurate Real Power calculations.
emonPi Home Energy Monitor setup demo:
Solar PV Monitor
Using two clip-on current sensors (CTs) and an AC-AC plug in power adapter (to provide an AC waveform sample to allow detection of current flow direction and more accurate Real Power calculations) the emonPi can monitor solar PV generation and grid import / export.
Choose 'High Accuracy / Solar PV' Kickstarter reward for Solar PV monitor application.
Temperature sensors can be connected directly to the emonPi via RJ45, multiple sensors can easily be added using an RJ45 breakout. The emonPi can also receive data via wireless from other compatible temperature and humidity sensor nodes such as the emonTH remote room sensor node.
Heat Pump Monitor*
Using a clip on current sensor (CT) sensor, AC-AC sensor adapter and multiple DS18B120 temperature sensors the emonPi can be used to monitor air and ground source heat pumps.
Solar PV diversion*
Usingadditional hardware developed by the OpenEnegyMonitor community the emonPi can serve as a solar PV diversion controller, diverting excess solar PV generated power into an electric immersion hot water heater.
Home Automation and Heating Controller*
The possibilities from easily hackable open-hardware and software are almost limitless. With some tinkering the emonPi can be used as a central hub for home automation and control. The emonPi can be used to command control nodes via a direct connection by aux I/O through the RJ45 socket or via RF using the on-board RFM69CW transceiver or an OOK RF module. We have in development a central heating and immersion heater RF relay control board.
Pulse Counting Direct Utility Meter Interface*
The emonPi can be used to count pulses (optical LED flashes) from some electricity, gas and water utility meters. This can be achieved using an optical sensor connected to the emonPi's interrupt input accessible on RJ45 socket.
* Some tinkering required
At its heart the emonPi is an Arduino energy monitoring shield for the Raspberry Pi.
An Arduino compatible ATmega328 is used to perform the energy monitoring ADC sampling and power calculations. Data is passed to the Raspberry Pi via its GPIO internal serial port in JeeLabs packet format. Arduino compatible firmware sketches can be uploaded directly to the emonPi's ATmega328 via the Raspberry Pi GPIO.
The emonPi connects to the Raspberry Pi via GPIO. The emonPi is not fussy over its flavour of Pi: model A, A+, B, B+ and 2 are all compatible, although only the model B+ and 2 will fit inside the custom aluminium enclosure.
Raspberry Pi 2 will be shipped with all emonPi Kickstarter rewards that include a Pi.
The emonPi is fitted with an RFM69CW RF transceiver module (433Mhz*) to enable it to act as an emonBase web-connected base station; this can receive data via RF from other OpenEnergyMonitor and JeeLabs modules such as emonTx energy monitor and emonTH remote temperature and humidity monitor. For further technical info and open-hardware design files see the emonPi Wiki
*We can offer a limited number of emonPi's with 868Mhz if required.
The emonPi has been in development for the past 12 months. Hardware design and prototyping has been undertaken by ourselves with community input and collaboration, including from the outset a lively ongoing emonPi development thread on the OpenEnergyMonitor Community Forums.
Initially we had planned for the emonPi to include a Raspberry Pi + 2.5" HDD, in practice this proved to be impractical and clunky with an external SATA link cable. Software developments on a low-write version of Emoncms logging and a read-only SD-card stack made it possible to only use the Pi's SD card for reliable long-term logging. As the HDD was discarded, the emonPi enclosure could be slimmed down. However the emonPi PCB has kept four mounting holes for attaching to a 2.5" HDD should this be required.
The software stack running on the Raspberry Pi inside the emonPi is fully open-source. It is based on Debian Raspbian running in read-only mode with emonHub python service; this decodes data received on the Pi's internal serial port from the emonPi in JeeLink Packet format and posts to emoncms: local server on the Pi or remotely (emoncms.org), or any other web logging service with an open API.
Another python service controls the emonPi's LCD display, push-button and shutdown button.
The emonPi's open-source firmware and software is available in the emonPi's GitHub repo.
Technology that helps us live within ecological limits.
We started the OpenEnergyMonitor project 6 years ago in 2009. The development of the system and its applications has been guided by the motivation to make the transition to sustainable energy in our own lives.
In the beginning we couldn't find any open-source designs to build an energy monitor so we set about tinkering with Arduino and breadboards to build our own. We created a website (OpenEnergyMonitor.org) and started documenting and sharing our progress. We thought it would be useful to be able to view our energy consumption on-line so we made the system web-connected. Collaborative development continued and the system gradually matured into a set of powerful and flexible open-source energy and temperature monitoring and analysis tools. With applications for home energy monitoring, solar PV monitoring, heat pump monitoring and solar PV energy diversion.
In 2011 out of demand for the system we set-up our business 'Megni' - short for 'Monitro Egni', which translates as 'Energy Monitoring' in Welsh. Today we have a small team to run our on-line shop, shipping worldwide from our base in North Wales, UK.
We believe open-source is a better way of doing things. You can learn more about this, how the technology works and how to build, repair and improve it, on the project website.
Ethical Design and Circular Economy
We started the OpenEnergyMonitor project to help ourselves and others understand our energy, inform energy saving undertakings, and better optimise our energy systems. We try to apply these core values and motivations to all parts of our design choices and manufacture. Taking inspiration from the Fair Mouse and FairPhone project the PCB’s are manufactured and assembled locally in the UK, all electronic components are chosen to be RHoS compliant and free from conflict materials. See our blog post: Ethical and Sustainable Electronics. Aluminium was chosen as the enclosure material since it can be 100% recycled, see our blog post: Embodied Energy of Electronic Enclosure Materials.
Previously we have always relied on bootstrapping our hardware manufacture, starting small and building up as demand and cash flow allowed. With the emonPi we want to reach a larger audience and offer the unit at an affordable price. To do this we need the help of Kickstarter backers to help us to manufacture the unit in a larger volume.
Looking Forward to The Future
Taking a step back and looking forwards at the bigger picture, the next 20 years are set to be a revolution for our energy systems as we transition from fossil fuels to a zero-carbon energy supply in an attempt to avoid exceeding a 2°C global temperature increase.
Since we started the OpenEnergyMonitor project 6 years ago global PV capacity has grown over 10 x from 16 GW to 185GW! Global wind power capacity grew over 2.5 x from 121GW to 318GW. The number of EV's on the road has grown over 6 x from 100,000 in 2011 to over 604,000 in Sep 2014.
The ZeroCarbonBritain report by the Center for Alternative Technology shows how it is technically possible to achieve a zero-carbon energy system in the UK through new and efficient buildings, existing buildings retrofit, electrification of transport, land use changes and renewable energy combined with extensive storage and control technologies to balance supply with demand.
To better understand the requirements and dynamics of such an energy generation and delivery system we have been looking in detail at the hourly model developed by ZeroCarbonBritian and helping to create an open-source web-based version of the ZeroCarbonBritain model.
The opportunities and benefits of taking an open-source approach to smart monitoring and control challenges are significant; we hope to encourage others to start projects & businesses that also work towards a zero carbon future in an open way.
Risks and challenges
There are many things which need to come together to successfully manufacture hardware on time. We are no strangers to the problems which can be encountered! For the past couple of years we have been manufacturing hardware in the UK and have built up a strong network of partners, suppliers and manufacturers, as well as a strong open-source development community.
Preparation is the key to enable on-time fulfilment. The emonPi PCB and enclosure design have been finalised and finished prototypes have been built and tested. We have already placed advanced orders with our suppliers for components and connectors. Our partners Lincoln Binns have already started fabrication of the emonPi aluminium enclosures.
The units will be finally hand assembled, tested and shipped from our base in North Wales. We are familiar with the logistical challenges of packaging and worldwide shipping. Over the past two years we have shipped over 7K orders to over 70 countries worldwide and have built up an excellent record for customer service and support.Learn about accountability on Kickstarter
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