VM167 Prototype: SMS on Open

For some reason I decided today to make a system to drop me a text message when the door of my bedroom is opened. I started off thinking about how this could be done - I didn’t fancy hacking a mobile to send a text particularly, I wanted more of a computer controlled solution. While I was thinking about the more complicated aspects of my sudden unexplained desire to make my room high security I did the more boring task of laying 10 meters of alarm cable neatly and invisibly around the perimeter of my room.

With this done, I had formulated the solution in my head - here’s how it works:

The VM167 Prototype Experiment board created by the good people at Velleman has an ample number of digital inputs to do this. I basically hooked up the reed switch on my door (Read: a type of switch that closes when it’s placed in a magnetic field that is strong enough and opens when it isn’t) to the VM167 on the other side of the room. From there, I hooked the VM167 up to the lovely netbook I got as one of our teams prizes at the Microsoft UK Imagine Cup 2011 finals. I then wrote a quick application in C# that accesses the Mediaburst SMS API to send SMS messages for a nice low fee.

Prototype board

The little black taped-up thing in the picture above is just a small Lithium battery - the board doesn’t react to open/closed circuit as an alarm-geek like myself might expect, it actually expects a potential difference between 1 and 5 volts to set the input to high. A minute amount of current is drawn so this little Lithium cell placed in-line works a treat.

And the result? Works like a charm. The program I wrote is really simple - it just provides a 15 second timer to “escape” the room and get the door shut. Once the door is opened, a text message is dispatched instantly and the program waits for the user to reset it to avoid spamming hundreds of texts if the door is just blowing around or something).

Message screenshot

I doubt I’ll ever have any use for it, but it got me using the VM167 prototype that Velleman sent me, and I might even develop something for iOS later down the line if Apple can stop people stealing my work.

Anyway, to finish off here’s a little preview of how silly my UI design is:

UI screenshot

Stay tuned for some posts from NYC!

Damien Walsh

I'm a 28 year old Computer Science graduate working in software & electronics development. I like electronics, programming, a variety of weird music and I sort of have a thing for motorbikes too.

Manchester, UK damow.net