Oxford (Hebden Bridge) Flood Network
On 15th-17th August we’ll be at Wuthering Bytes technology festival at Hebden Bridge where Ben & Andrew will be talking about and making the Oxford Flood Network.
If you’ve never been before, Wuthering Bytes is held in the picturesque and quirky town of Hebden Bridge, Yorkshire. It’s a combination of a technology festival and the Open Source Hardware Camp, an annual event run by OSHUG (Open Source Hardware Users’ Group) and thoroughly recommended for meeting people whose desks are covered in dev boards and Raspberry Pis.
On Saturday Ben will be exploring citizen sensing and creating your own evidence for your own issues such as flooding, air quality or noise.
On Sunday 17th Ben & Andrew will be running a workshop, so bring your wellies and we’ll split into two teams - one installing the wireless sensors in useful locations around the town, the other linking these up to the Internet using Raspberry Pi, Node Red, MQTT and lots of other sexy Internet of Things technologies.
If you want more information about the project, have a look at https://oxfloodnet.co.uk/background or just get hacking on https://github.com/oxfloodnet
See you there!
Ben & Andrew
Sensor v3 is Ready for Action
Since our first sensor back at Sushack in November 2013 we’ve learnt quite a lot about what works and what doesn’t work with a river sensor. Many of these lessons came from our test installation in Central Oxford.
It manifested in different ways but it’s fair to say moisture is our biggest enemy. The ultrasonic sensor was only rated for indoor use and when suspended above a stream would start reporting 22cm no matter what the actual water height was. Tests with a more expensive IP67 rated sensor have proved we can’t skimp on the transducer, but has put the cost up by £40 or so.
Shortly after we discovered this issue the entire device went offline. Not all IP55 rated cases are made the same and water got into the device after some very heavy rainfall. We now have a sturdy case with a seal and sensible holes.
The other issue was RF reception. The sensor was attached to a large steel girder under a bridge and this blocked much of the precious transmitted signal. During heavy rain ironically we believe it suffered from “rain fade” where the signal is disrupted by rainfall. To this end Andrew has added an external antenna. Which makes it look sexier too if I’m honest.
Finally, Andrew has created on how to assemble the latest version from the custom PCB design and some off-the-shelf boxes.
If you want to order an assembled device (approx £140) or a kit then email and we’ll let you know when we can deliver them.
Links to more information added
Down the side of the page you might notice I’ve updated the links to explain some of the background. We’re active on Github (software & designs) and also Twitter ().
There’s also a PDF (oxfloodnet-summary.pdf) which gives a full summary of the project.
A wet sensor. It’s hard to tell if this is condensation, sideways rain, or drips from above, but this is where we learn the value of IP55 rated boxes.
Sensor v3 will have a weatherproof enclosure (see IP code system) and also a weatherproof ultrasonic rangefinder. Luckily it seems sensor v2’s electronic hardware is still working after this soaking.
The innards of sensor v2, and a picture of Ben installing the sensor. The Internet of Things sometimes involves laying in duck shit.
Progress! Sensor v2 mounted
This weekend Andrew and I worked on getting the new sensor installed.
- A custom PCB was designed and manufactured for this sensor
- It uses a single 3.7v lithium polymer battery so needs no voltage regulators.
- It doesn’t have the massive battery drain I designed into the first one ;-)
- It’s much smaller
- There’s a Dallas DS18B20 temperature sensor which compensates for the velocity of sound in different temperatures (surprisingly it makes a difference of centimetres). This could also provide a unique ID for each device later. And of course a temperature reading
- Code and some schematics available on a new github project: https://github.com/oxfloodnet
The mounting uses strong magnets to hold it in place instead of velcro strips, which is interesting, but not cheap. It has a piece of wire wrapped around it in case it becomes dislodged (we didn’t have any string). We need to work on the mounting but the priority was to get radio range and battery life tested.
For now it’s still in situ and stable. It’s currently tweeting heavily to a private account but a visualisation should be available soon. The main aim at the moment is to produce a viable outdoor device and then bring in all the data.
More updates coming soon.
Sensor version 2 mounted under bridge.
First Sensor: The Story So Far
The first prototype sensor is out in Oxford, near the Castle Mill Stream in a small parallel stream called Wareham Stream.
On Saturday the distance to the water level was 66cm, now it’s 64cm, so I hope this is a rise in the water level and not a sag of my fixings!
The radio reception has been a bit of a problem. According to http://openmicros.org/index.php/articles/84-xrf-basics/289-adding-antennas-to-ciseco-radios the wire whip antenna is 1 quarter of the wavelength at 82.2mm. (868MHz) However, it’s buckled over inside the case whereas it should be vertical, perpendicular to the girder the sensor is stuck to. This can be resolved, but needs a hole drilled in the box to allow the wire to emerge. If I’m doing that I might get a better result with a half wavelength antenna at 16cm. At night the reception gets worse, which could be down to a baby monitor being turned on.
Andrew, another contributor to the project, is building an RSSI (Receive Signal Strength Indicator) test box, which allows us to wander around checking reception, rather than waiting 5 minutes for the next reading (or not, if it’s out of range).
More to come on this later.