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.