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Buses and Radiators: An Update


titleOpenTRV is all about energy efficiency (thus cutting carbon and your bills) at home, by making important but boring energy hogs, firstly your heating, work better and with less attention from you. Who gets up in the morning and thinks "How can I tune my heating today" (other than me)? Most of us have better things to devote our brains and time to, but as a consequence as much as half the money we spend on our heating is wasted.

OpenTRV aims to add just enough IoT smarts to radiator valves, with no smartphone or Internet connection or even instructions required, to automatically cut the heat when you won't notice.

It's IoT because we have microcontrollers, radio, and distributed algoithms, but it isn't flashy expensive screens: boring and simple is good.

Partly because we're a social enterprise, and partly because we think it's the right thing to do anyway, we're keeping as much of what we do open source and permissive, software and hardware and mechanics, eg see our GitHib repos at:

titleSo one thing we care about is radios, ideally: simple, low power, cheap, secure where possible, and controllable by microcontrollers. We also want to stay as far as possible vendor neutral.

We have a couple of channels in the unlicensed 868MHz ISM band that we use for in-building communications, but our stack lets us swap in alternative radios such as GSM (2G/GPRS) in the form of Arduino GSM shields, and LoRa (see below) both of which get us out of the building and into the smart city...

GSM works but is often expensive in practice in terms of power and telco bills, which is where LoRa comes in. Potentially free for low-bandwidth IoT applications once infrastructure is up, and for example as part of The Things Network.

OpenTRV has put up two LoRa base stations in London so far, including one on top of the Digital Catapult on the Euston Road:


The range in urban areas is expected to be up to 2km, but that's a bit variable, which we are exploring with our deployments in London bus shelters, of LoRa-equipped sensors to detect how busy the bus stops are.


I mentioned security above; often badly neglected in IoT and home environments.

When the first 1000 OpenTRV valves are rolled out, security weaknesses are a nuisance. If we achieve our vision of being on 400 million EU domestic radiators, a failure to protect sensitive data and prevent hacking of devices could be very serious indeed, on a par with weaknesses in energy infrastructure that gets the media in periodic panics.

One of our contributions to world peace is an initial permissively-licenced, microcontroller-friendly, small (~4kB) AES-GCM implementation for industrial-strength security (authentication and encryption) from IoT sensors and actuators back to a home hub or beyond:- Github/OTAESGCM

AES-GCM is a great and widely-understood security scheme, but in order to to apply it in the world of small and simple processors and radios we have proposed a framework which we are starting to use ourselves: - Github/Framework

Feedback on both the library and the spec would be very welcome; more eyes to spot flaws should help make our bugs shallow.

Equally if you can suggest alternatives not tied to particular vendors' hardware then we'd be very happy to hear from you.


OpenTRV will only achieve its energy/carbon ambitions if it is low cost and plays nicely with the other gear already in your house (and can avoid reinventing too many wheels).

To that end we have just had an interoperability hackathon with the great guys from Open Energy Monitor and others including Ken Boak, and we set ourselves some goals for the next six months: - Github/interoperability hackathon

It would be great if we could help OEM find a way to secure its radio traffic!

And Ken has some great board designs which we may be able to agree on a common connector for his and ours and others, all small by helpful ways of reducing friction in this IoT space.


We are going to round off our IoT Launchpad project with a final workshop (which RS has kindly contributed some goodies to, thank you!): "Internet of Things and The Things Network workshop”.

The following booking link includes a discount:

This includes LoRa sensor boards to take away, and will conveniently held in the DigiCat which also hosts our LoRa base station!

We are also aiming to show off our stack of standard simple IoT boards that match the aims of our original stack-of-Lego-bricks pitch!

Related Articles - 

FEEDBACK WANTED: IoT secure radio comms

OpenTRV - Saving Energy via the Internet of Things

The Things Network Reading 

OpenTRV sets out to make it easy to save lots of energy by just heating the rooms that you’re using, and by no longer trying to use a single thermostat to get your whole house comfortable. It is designed to be simple to (retro-)fit to existing UK housing stock with radiator central heating.