Thanks to Cédric for sending in this great project! Check out the full tutorial on his site here.
One of the “issues” we have at home is that we want to know when a specific door has been opened. We all know the door bell we’ve been using in shops for ages. When a customer enters the shop a bell will ring and the shop owner gets notified that someone entered; the bell was traditionally placed above the entrance door. This is basically the behaviour we want, but nowadays we have more advanced technologies to notify someone: we could trigger a wireless alarm, send a notification (mail/Growl/PubNub) to our smartphone, etc.
Unfortunately that’s not the only reason why we want to have such kind of technology. Nowadays, burglary has become a habit in our lifes and a lot of people started investing in home security; but ofcourse not everybody is capable to invest, due to the high costs.
You will find a myriad of information on the internet about home surveillance, and a lot of different brands which are offering surveillance hardware. In most cases, a company would offer a control station, which you can expand with additional features, for example: a security cam, door/window magnets, heating sensors, etc. The control station will manage and control all the different devices. As mentioned above a lot of these features are expensive, you will be paying a lot of money for a single feature; for example if you want to expand the control station with an extra door magnet, you will be paying 50€ and more.
Therefore people can “Do It Yourself” with equipment that’s less expensive, and with some time and effort. One could consider to buy a low-budget microcontroller, for example the very popular and open source Raspberry Pi, and a set of door magnets.
What is this tutorial about?
In this tutorial we will build a simple security system using two Raspberry Pi’s and a set of door magnets. The idea is that one Raspberry Pi will be controlling the magnet and will send a message to the second Raspberry Pi which in its turn will trigger an alarm when it received the message. So let’s get started!
What do we need?
To get started we will need 2 working Raspberry Pi’s with SD card and 5V charger. You’ve installed Arch Linux on the SD cards and have a networking connection (LAN or WLAN). We also need a set of magnets; in this tutorial I’ve been using the magnetic door sensors from adafruit. At last we need an audio device so that we can play sound (alarm/Text To Speech); I have been using this one from the Pi Hut. The audio device is not required, as you can send a Growl message instead; in this case you will need only one Raspberry Pi.
For this tutorial we will be using the Arch Linux operating system, so to get started get a fresh installation of Arch Linux on your two SD cards. Make sure you have a connection with your internal network, and both Raspberry Pi’s can communicate with eachother; try to ping.
Featured Adafruit Product!
Magnetic contact switch (door sensor): This sensor is essentially a reed switch, encased in an ABS plastic shell. Normally the reed is ‘open’ (no connection between the two wires). The other half is a magnet. When the magnet is less than 13mm (0.5″) away, the reed switch closes. They’re often used to detect when a door or drawer is open, which is why they have mounting tabs and screws. You can also pick up some double-sided foam tape from a hardware store to mount these, that works well without needing screws. Read more.
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