Help building an alarm system

[McGooTheWise]

I'm not sure if I should go from scratch for what I want, because I would like to program different audio files onto the system, or if I should mod a system off of ebay. It has to be a motion sensor, and be very aduible over a running diesel engine. I'm not exactly new to electronics, but I am new to building them from scratch, and I would like to learn as I go with this project.

Basically, all I need to know is what components might compose something like this, just what type of bus, or processor I need. I'm in the research stage now, and any extra help is very apreciated. Thanks.

 

[jackorocko]

Well you don't give a whole bunch of information about the purpose of your alarm. So one can only speculate on what you need.

This is something I was working on a year or so ago. It uses a simple voltage comparator to trip the alarm and then after a set time the alarm will be reset ready to be tripped again. Maybe it will give you a start

 

[McGooTheWise]

Well, its purpose is to use on a car or truck as a proximity alarm with interchangeable audio files for scaring off people who might like to steal fuel, or bug truckers when they're trying to sleep.