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Crownstone – the smart power outlet

KDE and ownCloud developer Jos Poortvliet speaks to the DoBots creator about their latest smart home tech


Crownstone by DoBots is a Dutch Kickstarter project that wants to make your power outlets smarter. A Crownstone is either built or plugged in and enables you to switch devices on and off and measure power consumption. It also knows where you are, which device is plugged in (by measuring its power consumption) and forms a mesh network with other nearby Crownstones.

We spoke with Anne van Possum – robotics guy, and COO and founder of DoBots – to ask him about DoBots and how they came up with this idea.

CrownstoneAnne: We’ve been on this for about a year now. DoBots is a spinoff from a company doing research into smart digital networking in Rotterdam. We’ve been working on biology-inspired algorithms to create digital ‘swarms’ of devices, from microbots to trucks.

One of these algorithms helps you build maps and locate objects in an area – think indoor GPS. We wanted to use that to make a house smarter, and as everything is controlled by power, we started with the power outlets. Add in some algorithms to detect what device is connected, and a mesh network, and there you have the Crownstone.

Jos: Clever! What devices can you recognise?

Anne: Many are simple: fridges, televisions. Others are harder – we’ve got trouble with the difference between LCD- and TFT-based monitors, for example. Our algorithm is about 93% accurate right now and we’re working on making it better before we put it on Github. Did I mention that everything we do is open source?

Jos: That is awesome. But why would you make your secret sauce open source?

Anne: Because we believe in it. We can never, by ourselves, figure out all the smart things you can do with a device like this, but if everybody starts making apps and tools, it can do anything.

Like, somebody could build an app to make a list of all the devices you have. Useful for insurance, or perhaps a local power tool sharing initiative.

Or make a child lock system which disables the TV or microwave under certain conditions, like when you leave the room or house or at certain times.

Jos: So we all know home automation is cool. What makes Crownstone different?

CrownstoneAnne: Well, for one, it is relatively cheap, in no small part because we don’t need a hub. We use the smartphone as a hub to analyse and store the data! The devices aren’t entirely dumb – each has its own little chip with 16K RAM (we’re going to move to 32K soon) and 256Kb flash. Doesn’t sound like much, but it is enough to store 24 hours of power usage statistics at a 1-minute sample rate, which is plenty.

It is all built around open protocols like Bluetooth LE, so it isn’t only extremely low power, it will work with nearly any smartphone. If you want a static hub, we have a flash card for Raspberry Pi devices. Stick in a Bluetooth dongle and it can act as hub, so you’ll get a warning on your smartphone when your TV gets unplugged while you’re not home… We use XMPP to get through your router’s firewall for that.

And the devices aren’t just sending – they can also receive and scan for data. If you walk around with a smartwatch, a Fitbit or another beacon, the Crowns can see you and act accordingly.

Combined with the automatic device detection, this means the system requires very little up-front configuration. You don’t need to spend time configuring every Crownstone to know what device it is connected to or what room it is in – they know that already. No need to configure your fridge to stay on and your TV to be turned off when you leave the house.

CrownstoneJos: How about security? I’d like to know if my Chromebox gets stolen when I’m on holiday, but I’d rather not have a potential thief know I’m not home!

Anne: Got you covered. Bluetooth 4 is actually reasonably decent, security-wise. Not perfect – the key exchange is a bit of a mess, and I personally hacked some devices already (see my Github), but Bluetooth 4.2 is darn solid. I’ve yet got to see somebody crack an elliptic curve Diffie-Hellman key exchange. So if you have an up-to-date phone or Bluetooth dongle, you’re very much secure.

You can find more interesting details on our blog, too:

Jos: What do you have to offer for people who want one and want to build with it?

Anne: We offer both a set of two Crownstones you plug between the device and the wall outlet, and three Crownstones you can build into your wall outlet yourself. So, easy or DIY; both. And what we do is on Github, as I mentioned – even the firmware. How many projects do you know which publish that?

On Github you can find several small mobile applications, mostly Android-based but iOS comes as soon as our Kickstarter has succeeded. There we also feature an SD card image for the Raspberry Pi, turning it into a hub.

Go get yours here:

Jos Poortvliet
About Jos

This article was kindly contribted by Jos Poortvliet, a people person, technology enthusiast and all-things-open evangelist. Jos is also community manager at ownCloud and openSUSE, and a KDE marketing veteran.