Alarms and security related schematics

• 4 Photo-Detector circuit with delayed release and bipolar output
• 5 Zone alarm circuit
• 5 Zone Alarm Circuit
• 5 Zone Alarm System
• Alarm control keypad
• Arduino Based Security / Automation Sensors
• Automatic Intruder Alarm
• Automatic Intruder Alarm
• Build an iButton electronic lock based around a AT91C2051 microcontroller (includes ASM source code)
• Circuit diagram for basic alarm with delayed trigger
• CMOS single zone intruder alarm
• Cold activated switch (frost alarm)
• Combination Lock (PIC16F84)
• Constructing your own Light Alarm
• Digital combination lock
• Digital combination lock using pair of CD4013 CMOS chips
• Digital Keypad Combination Lock
• Door Alarm circuit diagram
• Door knob alarm (PDF)
• Doorbell for the Deaf
• Easy to build tripwire activated alarm
• Electronic door codelock (PIC16F84)
• Electronic locker digital combination lock circuit diagram