Introducing emonDC

emonDC is a project aiming to develop DC current and voltage measuring tools compatible with project. The main board in development is emonDCduo, a dual-channel DC monitor, WiFi enabled, aimed at solar/battery systems. emonDC has been developed by Daniel Bates.

emonDC development kits are now available in the OpenEnergyMonitor Store.

Example System Schematic

Target Uses

  • 12V, 24V and 48V Solar PV systems, up to 64.4V max
  • Battery monitoring.
  • Remote DC data-logging.

Documentation on the unit, and on DC monitoring theory, is contained at the Github repo.


  • Two-channel high or low-side DC current and voltage sensing, up to 64.4V or 75V, suitable for a wide range of extra low voltage generator/battery systems.
  • 50Amps onboard shunt rating or 1000A external shunt rating.
  • Hall-effect current sensor footprint alternative for isolated current only measurement.
  • Waterproof, clear-top plastic case.
  • 128 x 32 OLED display.
  • WiFi Connectivity.
  • Low-power mode (10mA draw).
  • Accurate 12-bit ADC.
  • Over-voltage and reverse voltage protected (fuses).

Also, it can function as an independent unit, self-powered using an onboard buck voltage converter powered from a measurement channel. Data can be stored locally to a MicroSD card, keeping time with an on-board RTC and coin-cell. RFM69 based radio transmission is possible through a RFM69Pi module. For accuracy, the voltage sensing resistors and other reference voltage resistors are through hole, for easier modification, ensuring the option of very high resolution at low voltages. The I2C ports can connect control boards for power management, GPIO expander modules, or can forward data to a charge controller module. Skipping wireless transmission altogether, a standard 6-pin UART header is available.


Hardware Options

emonDCduo as designed here has shunt, termination, power-supply and other module options. See this demo video of the options.

Selection process

To help users with their purchase, a few options are available at the shop page. A specification process is required to purchase a unit, based on the installation context.

A recommended process would be something like:

  • Find the required Amperage of the target channels.
  • Select shunt on shop page exceeding the maximum expected current.
  • Select cable mounting, ring terminals require crimping, screw terminals are convenient.
  • Select power supply option. If the unit is powered from a measurement channel, then a DC-DC buck regulator is required. I the unit is powered from an external 5V PSU, then wires need connecting to a 5.08mm terminal block on board.
  • Check the remaining options on the store page.


The firmware is based on emonESP, and detailed instructions on compiling and uploading the firmware can be found in the emonESP documentation.


Other Customisation

Below are a set of images outlining some other customisations.

Online Support

Find answers, post questions, or message Dan directly via the Community Forum. Username @danbates

EmonDC Github Repo: Hardware & Fimrware

2018 Development Review

We have been refreshing the project development plan and as part of this looking at the goals we set ourselves in the last plan, posted last February: OpenEnergyMonitor goals 2018/2019. This post is an update on the progress made before outlining the new development plan in a separate post.

Its been a busy year, with significant progress made on most of the goals outlined, looking through all of the github pull requests and commits its evident how much of a team effort it has all been. Thank you to everyone who has helped throughout the year.

Read on →

Demand Side Response Development

openevse leaf

Demand side response (DSR) has been a OpenEnergyMonitor project interest for some time (e.g PV diversion) but has only made its way into a product more recently with our work on the OpenEVSE charging station. The OpenEVSE already implements real-time DSR, this post outlines how we are working on improving on this by integrating the forecasting and scheduling approaches being developed as part of our involvement in the EnergyLocal project.

Read on →

Emoncms Blue Theme

For a fresh clean start to 2018 the default Emoncms theme has now been set to “blue” :-)

The blue theme was chosen to give a consistent user experience between the other OpenEnergyMonitor websites e.g. Forum, Guide, Learn, Homepage etc.

We like the clean look of the blue theme, we hope you do also :-)

If you don’t it’s easy to revert to back to the old black theme by setting $theme = standard in settings.php. There is also a user contributed yellow theme called sun which is available.

emonPi Emoncms will update automatically during emonPi update to use the new theme as long as settings.php has not been user modified.

Feed view in Standard, Blue and Sun theme:

Read on →

emonPi Remote Access with Dataplicity

Network devices such as an emonPi connected to a local network are secured behind a firewall, often integrated into a router.

The conventional way for obtaining access remotely is to open a port in the firewall and ‘port-forward’ requests to this port to the local emonPi. This method works but is cumbersome and insecure. It’s cumbersome because most users connect to the internet via their ISP using a non-static IP. Therefore the WAN IP address often changes, a dynamic DNS service such as Duck DNS, or noIP can be used to link a dynamic IP to a static domain name, however this is cumbersome to set up and often requires purchasing a domain name, dynamic DNS Subscription and handling the dynamic DNS IP address updates.

The port forwarding method of remote access is also insecure since by default the emonPi uses an insecure http connections, this is not a problem on a secure local network but not recommend for use over the internet.


Dataplicity offers a easy to setup web-service service to enable secure remote access (SSH/HTTPS) to RaspberryPi devices. The free tier allows free access to a single RaspberryPi device.




Follow the steps on the Remote Access page of our User Guide to setup Dataplicity on an emonPi.

Introducing IoTaWatt

IotaWatttm is an open-hardware 14 channel WiFi connected electric power monitor. It’s based on the ESP8266 IoT platform using MCP3208 12 bit ADCs to sample AC voltage and current.

IoTaWatt can log data locally to on-board SD card and post directly to via WiFi.

There are no plans to discontinue the emonTx. Both the IoTaWatt and emonTx have advantages in key areas which complement each other.

IoTaWatt is fully open-source and has been developed by Bob Lemaire @overeasy in partnership with OpenEnergyMonitor.


View in Shop → Setup IoTaWatt



The IoTaWatt uses the WiFi enabled ESP8266 (ESP-12S) microprocessor. The ESP8266 is mounted using NodeMCU adaptor, the decision was made to use the NodeMCU form-factor to allow flexibility for customisation and future upgrades e.g ESP32.

The onboard SD card allows data to be saved locally with high resolution and network resilience. If the IoTaWatt is posting to an Emoncms server and loses network connectivity data logged to the SD card will be bulk uploaded to Emoncms when a network connection is restored.

An on-board real-time clock (RTC) ensure the time-stamp is always correct. The RTC is set using NTP. Using the IoTaWatt on a WiFi network with a reliable internet connection is highly recommended, however, the IoTaWatt can operate without an internet connection once the RTC has been initially set via NTP.



The IoTaWatt is configured via a web interface served directly from the IoTaWatt ESP8266. See for a live demo of the interface.

The IoTaWatt supports automatic over the air (OTA) firmware updates.

Read on →

CydYnni – Energy Local, community hydro smart grid

Over the last year we have been involved in a project in our local area (Snowdonia, North Wales) called CydYnni – EnergyLocal. The project is at the forefront of making it possible for households to source their electricity directly from local, community-owned renewable sources.

The Bethesda pilot project, How it works

The first part of the CydYnni project started with about 80 households (with 20 more joining soon) and a single 100 kW hydro generator. Using smart meters suitable for half hourly billing in participating households and at the hydro generator, the amount of hydro power used by the community is calculated for every half hour. The hydro tariff is 7p / kWh for the power used each half hour by the community providing a significant saving for households. Any additional power required is bought from the supplier Co-operative Energy on a time-of-use tariff.

The project provides cost savings to participating households, increased income for local renewable energy schemes and a more direct sense of having electricity provided from - in the case of the pilot project a hydro turbine just down the road!

There is a nice video here on the project which gives a good overview:

There are a number of organisations working on the project of which we are one small part:

  • EnergyLocal: The organisation founded by Mary Gillie with the initial idea and in depth understanding of the energy market behind the project.
  • CydYnni: A local consortium of community energy projects and organisations including Ynni Ogwen and Partneriaeth Ogwen, Ynni Padarn Peris, Moelyci, Coetir Mynydd, Antur Waunfawr, Ynni Anafon and the National Trust.
  • Co-operative Energy: The Energy Supplier through which households participate in the project.
  • Epower also known as NFPAS: The non fossil fuel purchasing agency – handling aggregation, power sharing and the nuts and bolts of billing.
  • 1010: Graphic design
  • OpenEnergyMonitor: web app development in part 1 and home hub (base-station) development in part 2.

It’s been great being involved in such a pioneering project run in the local community in which we live (the OpenEnergyMonitor office is about 5 miles from Bethesda).

Our role so far has been to develop a web app / energy dashboard so that participants can see when the local hydro generator is running and how likely they are to be on the cheaper hydro tariff. Participants can see their own consumption as well as the aggregated consumption of all participants.

The main energy dashboard app designed by 1010 and implemented by ourselves can be viewed online here:


The source code for the app is open source and available on github here:

We have also developed a dashboard that is more focused on exploring the full data history of the hydro generation and community consumption, this dashboard can be viewed online here:


From the start of January the hydro supplied 57% of the electricity consumption of the participating households. You can really see how the available hydro generation decays usually over about a week after a significant rain event and the extent of the oversupply when it is raining.

It would be interesting to model the addition of solar to see how periods of lower rainfall might be supplanted by solar generation and explore other options for supplying the unmatched demand - e.g. anaerobic digestion.

Part 1: Energy Dashboard / Web App development

This first stage of the project relies on the app or looking at how rainy it is to signal to the households when it’s a good time to use energy. Any demand shifting is done manually by the householder. The data update rate from the smart meters is also relatively slow, with 48 half hourly readings updated daily but usually available in the app with a lag time of anywhere from 15 hours up to 63 hours over the weekend.

Part 2: Hub

The next stage of the project for us is to improve on this with an in home hub (based currently on the OpenEnergyMonitor emonbase), which will interface with a WIFI/radio meter gateway developed by Energy Assets, providing much faster 5-10s meter readings as well as enabling control of smart appliances, plugs and EV charging.

This development has driven some of our most recent improvements to the EmonPi/EmonBase, such as the recently launched WIFI Hotspot setup and ongoing development on the emoncms device module, which alongside auto-configuration of inputs and feeds provides the option to define control devices starting with the Sonoff S20 WIFI Socket, Martin’s WIFI Relay unit and the OpenEVSE charging station.

Over the coming months I will try to blog more on development progress and the technical implementation of the system in addition to insights into the data coming from the project demonstrating local community energy.

Advances Wales Magazine Article

Advances Wales is a quarterly magazine showcasing the latest news, research and developments in science, technology and engineering here in Wales, UK.

In the latest issue (82) we have been lucky enough to have an article featuring OpenEnergyMonitor. It’s well written and mentions a number of exciting developments that we have been working on e.g. CydYnni local energy project. Stay tuned for a blog post coming soon about this project.

Download the full magazine here.

advances artice

Emoncms Android App V2

Yesterday we have launched a significant update to the Emoncms Android app.

androidv2-1 Get it on Google Play

New features

1. Multiple emoncms accounts:

Monitor multiple Emoncms accounts, very useful for installers, power users etc. It’s also possible for these accounts to be on different Emoncms servers e.g., emonPi, emonBase, etc. Additional account are easily added to the app using the built in QR code scanner and scanning the QR code on the ‘Account’ section of Emoncms.


2. Multiple MyElectric graphs per account:

Useful to monitor more than one power feed: e.g. House consumption, Heat Pump consumption, Solar PV production, EV charging etc.


3. Multiple currency rates for each MyElectric graph:

e.g day rate / night rate, Economy7, solar PV FIT, hydro etc.


4. Language Translations:

French, German, Dutch, Italien and Spanish all rank among the top 5 for the Emoncms app in terms of active installs. We have now added the full native language support they deserve. Thanks a lot to the community for helping to proof and beta test. See bottom of this post for how to get involved.


5. Chromebook support:

Many Chromebooks can now run native android apps, the Emoncms app works great on a Chromebook. It’s much quicker to load than the web version and does not require a login each time.


Read on →

emonPi Network Setup Wizard

Ever since we launched the emonPi we have always wanted to make the first time setup process as easy as possible for new users.

emonpi wifi

We have just made significant progress in streamlining the setup process by enabling the emonPi / emonBase to broadcast a WiFi access-point (AP) on first boot then scan for local WiFi networks and allow the user to connect. The emonPi will then turn off it’s AP and connect to the local network. There is also an option to connect via Ethernet or stand-alone WiFi AP mode when no local network is available.


This has now been made possible using the Raspberry Pi 3 which supports WiFi access-point AP mode, some bash scrips and a new emoncms-setup module.

The new Network Setup Wizard will be included on all new purchased in July 2017 onwards. Existing emonPi’s with a Raspberry Pi 3 can be updated by running Admin > emonPi update in Emoncms. The emonPi will only broadcast a WiFi AP if Ethernet is not connected and no WiFi setup is currently present.

Trystan is also working on making the input-processing setup for new devices easier by adding device template support to the Emoncms Device module. More on this the come…see development forum thread.

Read on more screenshots of the emonPi network setup wizard….

Read on →