The Security System
I wanted the security system to be controllable and queryable
from
the
central controller. This would preferable occur over the home control
network,
since the security system could be a long distance away. At the time of
my search (fall 96) I could not find any system at an affordable price
that precisely met my needs, so I decided to build one instead. This
section
will not be very detailed for obvious security reasons.
The system runs on a small commercial microcomputer board,
with the
program written in C. It has the following sensors, all hardwired:
- Exterior Door Sensor
- Windows
- Motion Sensors
- Glass Break Sensor
- Smoke Detector interface
- Garage Door Sensor
There were several features I implemented to increase reliability:
- All sensors wired via
twisted shielded
cat 5 cables
- High Current (5mA) loops
for all zones
- All inputs have
individually
customizable half second software
filters
to remove glitches
- There is a hardware
watchdog timer that
the processor pings at a
set
rate.
Should the processor die (due to glitch, brown out, programming error,
or whatever reason) a hardwire security circuit takes over. This
circuit
simply trips the alarm horn and flashes lights when there is a security
violation while the system is armed.
- 12 Volt, 50Ahour battery
for backup
power
These are the features of the system:
- Electronic bell pings a
number of times
depending on which door
opened,
allowing us to know where the entry occurred
- Modes (perimeter, away,
normal) etc.
setable from the central
controller
- Status of all zones
continuously
available to central controller
- Disarm and degree of Arm
controllable
by central controller
- Central controller turns
on a light if
it is dark one exterior
doors
- Central controller turns
on interior
light if its is night time
and a
certain
collection of lights is off
- As in the case of the
standard X-10
alarm system, all lights in
the
house
flash when there is a security violation. A very loud horn mounted
exterior
to the house also sounds in this case
- Central controller calls
and speaks or
pages in case of violation
- Central controller speaks
the zone of
violation or entry (future
enhancement)
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