A WSN project: Best way forward?

Hello, I’ve been directed to Electric Imp to try to find a possible way forward for a WSN project. Here is some context from a different forum;

I’m thinking Terrence’s theory might suit me best here due to the fact that my proposed network actually consists of 6 different sensor locations around the Isle of Man TT race track (Motorcycle road racing). The idea is to try to provide real-time humidity and temperature data to a central task manager to help organisers and competitors make informed safety decisions ie. damp patches, melting tarmac, what time might be safe to race etc. Initially I thought I could have several sensors at each location around the track which feed data through a controller and on to a nearby PC at an adjacent building with WiFi. The next step would have been to use a long range WiFi extender (such as the Ubiquiti Networks Powerbeam AC) to transmit the data to a central task manager located within the track boundary. I was hoping then to use NetMF to create a simple visual basic UI to present the readings to the user.
However, Terrence’s Electric Imp 001 looks to be a whole lot more cost effective for such a project in terms of finance and time. Thing is, I have no knowledge whatsoever when it comes to programming these devices. Do you reckon the Electric Imp would be quite straight forward to program for a beginner? Have you ever used NetMF to create a UI based on Electric Imp?

…to which I got the following reply from Terrence;

Do you reckon the Electric Imp would be quite straight forward to program for a beginner?
Well no it will be a struggle. BUT there are some great examples on the Electric Imp site that you should be able to cut and paste that will get data up into the Imp Servers. From there getting into Azure is a whole 'nother ball game. There are 10 different ways to do it depending on what you want to do.

Have you ever used NetMF to create a UI based on Electric Imp?
You won’t need to. Once you get your data into a database “somewhere” you can extract it with a full windows pc and use the full .net framework to build your UI.

Can anyone provide any direction on a topic I have limited knowledge of? Any would be greatly appreciated.

Regards, Ben.

A very interesting WSN project.

For your 6 different sensor locations, a couple of questions which will help narrow down possible solutions:

  1. Is there a power source for each sensor or do you envisage operating sensors from batteries.
  2. What is the terrain like and distances between each sensor. Is it a couple of km apart or 10’s of km apart.
  3. What volume of data will you want. Is this updates every hour or every couple of minutes, or event driven or streaming.

I’m based in Dublin so could help if it is needed. Please PM me if you need any technical assistance with full stack development.

Hello Gerrikoio, thanks for your reply.

  1. I think using batteries at each point might be OK, partly because the event only lasts for two weeks. However, if it is the case that the sensors can be powered by some source at each point it will obviously help with cost etc. This will require further research on my part.
  2. The track consists of normal two lane A roads. My thinking was two have several multi hop sensors along the side of the track at each of the six points, to try to increase the likelyhood that perhaps one or two of them are in a dry patch, when really it’s quite damp if you see what I mean. So let’s say 10 sensors at each of the six points? Maybe I would only require one sensor? I’m really not sure at the moment.
  3. I think due to the scale of the track and the changeability of the island weather it might be better to have updates every couple or few minutes.

FYI this is a conceptual project. The idea is for me to investigate if such a network is possible and feasible. If so I will try to explain in depth to the reader how the recommended hardware will communicate with eachother and attempt presenting a UI based on NetMF, ideally to the extent that if the project ever were to be physically implemented, the bulk of the work has been done. My limited programming experience is in visual basic and I’m an Open University student.

Thanks again, Ben.

btw, you may want to look at the nora board, as it’s an off the shelf, pre-built, 2xAA powered temperature/humidity/air pressure sensor board. It’s not weatherproof though, so you’d have to sort out housings, but you could certainly run it for weeks from 2xAA even with a regular reporting schedule.

These are on amazon US for $50, but if you needed some for this in the UK then that could be arranged I’m sure.

We’ve used ubiquiti long range (airgrid) devices with imps and yes, you can get a huge distance with them - and an unmodified imp at the other end. We got over a km as I remember, but ran out of flat area to go further.

We didn’t document this in the blog post http://blog.electricimp.com/post/56247500373/going-to-great-lengths-with-the-imp-and-wifi as… well, it’d be more impressive if we could actually run out of signal :wink:

Not sure what the mobile phone coverage is like along the track but I would have thought that posting data updates every couple of minutes would be fine using GPRS connectivity. This is lower hardware cost but you’ll be paying a usage fee for data transmitted. I’m no antenna expert but would have thought in that terrain you would need to elevate your directional antenna to get your line of site distances. You would probably need to push up TX dB which will consume more battery power. Have you looked at LoRaWAN as another possible solution for your WSN.

@Hugo and @Gerrikoio Thanks for you replies.
I’m going investigate both of your recommendations asap. I’ve had a quick look at both after reading your messages and I definitely seem to be getting closer to my solution.

In relation to data transmission from sensor points to central task manager I was under the impression following a previous reply from Terrence, that as long as I had WiFi access at each of the six points, I could send sensor data to the cloud (preventing the need for long range WiFi hardware etc) and then download it at the central task manager, providing it had internet access obviously.

Yes that would be a correct presumption to make and electric imp would certainly be suitable if wifi access available at each of the 6 sites. So overall system architecture looks viable. There’s plenty alternatives/options available on how you consolidate your data set and present it via your front end, e.g the central task manager could readily reside on any hosted web server. .

Hi Gerrikoio and Hugo. I’ve narrowed my options to the Xbee WIFI module (which requires a Zigbee sensor connected and an explorer board so that I can communicate with the WIFI module from my PC) and the Nora option mentioned above. Could any of you clarify if I would require any other hardware to proceed with the Nora option, the equivilent of an explorer board for example?

Correction: xBee THT Grove board with xBee WIFI module and Grove temp/humidity sensor connected

Yes Seeed Studio’s Grove modular system is a nice way to get up and running fast.

The nora is totally self contained - just add 2xAA batteries for a working system.