Design a Customized
By John Blankenship and Samuel Mishal
Nowadays, home security systems are commonplace, but often have limited
capabilities. If you could design your own system, it could meet your
specific needs and perhaps even save you money. If your home could call
your cell phone when a violation occurs, for example, you might be able to
dispense with monthly monitoring fees. If you travel a lot, imagine the piece
of mind you would have if you received an email every day telling you
everything is secure.
Assume that in addition to the standard window and door sensors, your home has motion sensors mounted outside the house to give an early warning so the system can react before a break-in actually happens. When outside motion is detected, lamps
and perhaps a radio could be turned on to give the
impression that someone is home. Furthermore, the times
of the outside movements could be logged and included
in an email report.
Consider what you could do if your system could
interface with a camera. Instead of just saying that the
house is secure, the daily emails could actually include
one or more pictures as proof that everything is okay.
And, should an intrusion actually occur, the system could
take a picture of the intruder and immediately email it to
Once the system has the ability to interface with a
camera, imagine the added functionality you would have
if it could be mounted on a motorized turret. You might
even want the ability to point the camera from a remote
laptop and request pictures in real time. If you need more
flexibility, imagine mounting the camera on a mobile
robot that can be controlled over the Internet from
anywhere in the world.
Remember, the whole idea is to create a custom
system that meets your needs. You may or may not want
all these features, and you probably have additional
requirements we haven’t even considered. With all these
complexities, you might be wondering how difficult it
would be to implement such a robust design. The
software for such a project — especially if it grows over
time — could eventually become quite complex. For that
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reason, the language we choose for implementation
should have strings, floating-point math, arrays, and a
significant amount of memory which would be beyond
the capabilities of most microcontrollers.
If we center the hardware portion of the project
around a PC, we can take advantage of low cost web
cams, and memory will certainly not be a problem. With
Microsoft’s constant pressure to make Windows more
stable, though, many PC languages cannot even handle
basic I/O operations any more, let alone our more
advanced needs. Just capturing images from a web cam,
for example, is difficult (if not impossible) to do in many
languages, and support for Internet communication and
the sending of emails is even less common.
FIGURE 1. Standard magnetic window and door
switches are easy to interface.