Monday, February 10, 2014

Raspberry Pi Home Security + Automation - Phase 3

In Phase 1 and 2 of my previous posts in this series, I showed the basic setup of a Home security  +  automation system. No home security system is complete without a siren/alarm so this posts addresses that.

I was looking for a way to trigger the alarm and wanted it to be completely isolated from the Pi GPIO to avoid false triggers.  I also wanted to avoid using more GPIO for this project so I decided to a 433Mhz wireless siren similar to the one on Ebay here

If you open up the wireless strobe siren you will find this:

There is a small switch on the PCB to switch the circuit on/off. A white wire goes from the board to the piezo siren. For initial testing, I would recommend disconnecting the siren so that you can verify that your system works correctly without the really loud (90 dB) siren.

A 433MHz transmitter accompanies the strobe/siren to trigger it. I wanted to decode the code sent by this to allow me to trigger the siren myself. So I hooked it up to a 12V battery below and pressed the test button (see picture below).

The receiver already connected to the Pi (as shown in Phase 1) will help you find the code for your siren module. (use RFSniffer provided on the ninjablocks website to do this)

Here is a  short video showing the system in action.

Note - 
  • The 433 MHz door/window sensor  shown here is actually one that is normally connected to my  door/window and is not the one provided for triggering the siren. 
  • I have removed the waits in the code to trigger the siren immediately for the purpose of this video. You would normally have a delay to allow system disarm by an authorized individual