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Tuesday, February 1, 2011

Inexpensive perimeter alarm

Security after TEOTWAWKI (The End of the World as We Know It) will be important. Depending upon your location – methods used to be aware of “trespassers” will vary. For those on a budget – I have discovered a very inexpensive method to provide a decent alert when  a passerby trips the alarm.  
The main component is a window/door alarm that can be purchased at your local Dollar Tree for $1.00 each. These alarms are very loud (90 decibels). They contain a simple on-off switch and work via a corresponding piece that when moved away from the main unit – activates the alarm. Below are the step-by-step instructions on how I made one:  

STEP ONE (below): Purchase the alarm – often available at Dollar Tree and other “fine outlets”. 

STEP TWO (below):Obtain a piece of wood – such as the 2×4 pictured – and add two attachment loops for mounting.  

 STEP THREE (above): Remove the battery compartment door and unscrew the small screw which holds the top and bottom half of the alarm together. You will need to find a longer small screw to replace the screw you just removed in this step.  
STEP FOUR (above): Screw the longer screw into the hole all the way through the unit into wood to securely mount the alarm to the board. DO NOT OVERTIGHTEN  – you want the screw to be snug against the alarm.  

STEP FIVE (below): Making sure the switch is in the OFF position – install the included batteries.  
STEP SIX (below):I did not provide a very good illustration – but the bottom-left corner of the second piece needs to have a small amount of material carved away with a sharp knife or file. This will allow the piece to swivel away from the main unit. After carving material away from that corner - attach the 2nd piecewith a small screw. You need the second piece to be loose – so do not even make the screw snug.   

FINAL (above):The unit is basically complete. This design allows the board and alarm to be mounted to a tree/object via bungee cords. A fishing line can be attached to the empty hole in the 2nd piece and attached to a tree or some other object. The 2nd piece is held next to the main alarm unit via an internal magnet. A small rubber band or a piece of double-sided scotch tape may be needed to hold the two pieces together without prematurely setting off the alarm. 

 Summary: This is but one design and depending upon your application can be changed and adapted. Painting to camouflage it may be needed to prevent it from being noticed. The unit is not weather-proof  – so a small “roof” can be mounted over the alarm using  a 20-oz soda bottle cut in half length-wise. You do not want to cover the unit as that will reduce how loud the alarm is when activated. 
Of course – the alarms can be used for their intended purposes – mounting on doors and windows. 
A lot of possibilities here - 
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