Security System
Leah Langston
Daniel Suhr
Project Description
 When Distance
Sensor is triggered
within 6 inches, a
song is played
 In order to turn off
the song, the correct
code must be inputted
to keypad
Important Concepts Used
 Tables
 A to D conversion
 Timer System (Input Capture and Output Compare)
 Interrupts
 RTI
Hardware
 HCS12 microcontroller
 Internal Speaker
 Keypad
 GP2D12 distance sensor
Circuit Schematic
Flowchart - Main
Flowchart- Song Notes Interrupt
Flowchart – Alarm Interrupt
 t=(1/(freq of note))/42nS
 Flag is set when TC7 = t
Challenges
 Initially thought we could set TCNT to desired amount to
generate desired frequencies
 Can’t use output compare on PM4 (speaker), used pin PT7
for toggling PM4
Why this is useful
 Security Systems are valuable for protection
 Fun to have the flexibility to program your own song as
alarm
Questions?