Super loud security alarm

Step 6 Upload the code, and test it!

Now all that's left is for you to upload the code, set it upright against a lamp or bookshelf or anywhere it has a 'view' of the whole room, turn it on, and walk away. You can even place it behind a picture frame that's on a desk/table/bookshelf, and leave the PIR sensor poking out, but hide the 'guts' (and the battery-powered/plugged-in mini amp) so that it's inconspicuous. Now it's barely noticeable! The amp that I got from radioshack has a socket that accepts 9V wall warts, and the BS2 carrier board has a barrel jack connector, too and a regulator, so you can wire up the whole system to run on outlet power.

Below is the source code for the alarm.