Book Image

Building a Home Security System with BeagleBone

By : William Pretty
Book Image

Building a Home Security System with BeagleBone

By: William Pretty

Overview of this book

One of the best kept secrets of the security industry is just how simple the monitoring hardware actually is - BeagleBone has all the computing power you need to build yourself an extremely sophisticated access control, alarm panel, and home automation and network intrusion-detection system. Security companies make a fortune each year by charging exorbitant fees to their customers. You will learn how easy it is to make an alarm system with Beaglebone. A company-maintained-and-monitored alarm system has its place - your dear old mum is probably not going to be creating her own system any time soon. But if you are reading this book, you are probably a builder or a hobbyist with all the skills required to do it yourself. With Building a Home Security System with BeagleBone, you will learn everything you need to know to develop your own state-of-the-art security system, all for less than a year's worth of monitoring charges from your local alarm company! You will start by building and testing your hardware and open source software on an experimenter's prototype board before progressing to more complex systems. You will then learn how to test your new creations in a modular fashion and begin to utilize BeagleBone. Once your system is built and tested, you will install some of the professional-grade sensors used in modern alarm systems and learn how to use them. You will also discover how to extend your alarm system in a variety of different ways. The only limit will be your imagination.
Table of Contents (16 chapters)

The hardware


The alarm system, in this case the BeagleBone, must be able to monitor the world around it. It does this by using ICs called comparators. You can think of a comparator as an op-amp with extremely high gain. Like an op-amp, when the voltage on the positive (+) input is higher than the voltage on the negative (-) input, the output goes high. When the opposite is true, the output goes low.

The LM339 comparator

We will be using an LM339 comparator. I chose the LM339 comparator because it has been around forever, and still comes in through-hole DIP packages. It is cheap and easy to source. Best of all, it is hard to blow up! The device has an open collector output. What this means is, a resistor is required to pull the output high. By connecting the output pull-up resistor to 3.3V, we now have a level converter that can be safely connected to the BeagleBone.

In the following diagram of the single zone comparator circuit, a 4.7K ohm resistor—R5 is used as a pull-up. The LM339 comparator...