Figure 30 - A semi-permanent installation using a magnetic door switch
Figure 30 - A semi-permanent installation using a magnetic door switch

I also used this alarm system to protect several storage buildings on my property that did not have power available. By installing magnetic door and window switches via wires to the alarm system, it was able to act much like a typical home alarm system, allowing time to set or deactivate the alarm using the secret code during entry and exit. In this mode, the alarm unit needs to be inside the building in a place that is out of the way, just in case the intruder is brave enough to hunt around for the alarm unit as it is screeching away. The intruder will likely flee the scene right away, and even if he/she does try to find the alarm box, it will be very difficult as the high pitch of the siren is not at all easy to track. Figure 30 shows the alarm mounted in one room while the magnetic door sensor is in another room. Multiple sensors can be chained in parallel this way as long as they are all either "normally open" or all "normally closed" circuit.

This project leaves plenty of room for improvements and modification, and you can use just about any sensor imaginable to trigger the alarm system. Infrared motions sensors, gas sensors, light sensors, sound sensors and even radiation sensors can be used as long as you power them externally. If you build this project using surface mounted components, it could be made very small and easily concealed inside another object, making it very stealthy. You will never have to be without some kind of security system with this simple project!
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