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Home Security System
This is the alarm system I have in my house. I designed and built this
project in 2002. It is the fourth alarm system I have created. This is
a traditional wired alarm with an entrance and exit delay, shut-off
timer, 6 digit combination lock, and rise-fall siren. The alarm has 3
sensor loops: one delayed, one instantaneous, and one that is always on.
Commercial alarm systems are invariably based on microcontrollers. This
project is built with low power Schottky TTL. A board full of TTL chips
would not be cost-competitive today. But TTL was easiest for me to
design!
The alarm's design is practically a textbook example of finite state
machines. The main FSM has 7 states: off, door open, exit delay, armed,
entrance delay, intrusion, and shut-off. It clocks at a leisurely
1.5KHz.
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