Designing and building an environmental monitoring system.

You are aware the PI does not have an analogue input to read your DC voltage sensor, you will have to implement your own.

Fortunately this is not difficult, this is a great article from Adafruit  https://learn.adafruit.com/reading-a-analog-in-and-controlling-audio-volume-with-the-raspberry-pi/overview

this one deals with using the I2C interface https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

have fun and come back for more help if needed

You are aware the PI does not have an analogue input to read your DC voltage sensor, you will have to implement your own.

Fortunately this is not difficult, this is a great article from Adafruit  https://learn.adafruit.com/reading-a-analog-in-and-controlling-audio-volume-with-the-raspberry-pi/overview

this one deals with using the I2C interface https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c

have fun and come back for more help if needed

Thanks for the pointers. I must have been mistaken when I thought the Pi had analogue inputs, ah well. There's only going to be a couple of analogue inputs so do you think something like this would suffice? The aim is to get a proof of concept/prototype board made using a Pi and the pre-made modules to get the software implemented and working and then to refine the hardware design.

For analog that would work nicely, do remember though it is not isolated from the PI or any other connected devices. You have not specified what your monitoring in the environment. Lightning

You could try the beaglebone black, that has LOTS (read: to many) analog inputs. It also will run linux I believe. I'm wondering how you are planning on uploading the info to a server as that is a project I am working on now for temperature and pressure, but I am using the freescale xtrinsic sensor board with a Tiva C Launchpad and CC3000 Boosterpack.

I would have preferred to use a CC3100 Boosterpack with a launchpad or a CC3200 Lanchpad, I will hopefully try those soon. As for the the data you can upload that to either Plotly or Xively the second one is more powerful but I think more complex to use, and that will give you real time graphs.

Good luck on your project and hopefully it all goes well for you, keep us updated on your progress

Kas

It's mainly going to be used for internal monitoring of buildings, and the guys said, and I quote, "If we can get a sensor for it then stick it on there."

I've given the Beaglebone black a look but as far as I can find it doesn't support I2C connections, which slightly scuppers the idea of using that.

As for the transmission of data, the server to store the data will be running MySQL and I'm thinking to get round network issues I will set up OpenVPN to act as a bridge between the software running on whatever system it is implemented on and the server, this was the main draw to the pi, the fact that I know it runs Linux well and can do these things. Really the network can be LAN, WLAN or a 3G connection as long as it can get an OpenVPN connection, then SQL commands can be tunneled through that. The guys have said they want the data to be accessible to export to specialist software they use so doing it in this format makes it fairly easy to do that with. I might give those services a go for the prototyping stage but I reckon that it will end up being MySQL in the end.

The BBB definitely has I2C support (Page 72, 85, 89 ) I don't recall the pin numbers (P9-17,18. P9-19,20) but I know its there because I have used them before. As for the linux issue I'm pretty sure you can run linux on the BBB.

Either way good luck

http://derekmolloy.ie/beaglebone/beaglebone-an-i2c-tutorial-interfacing-to-a-bma180-accelerometer/