Intruder alarm module installed and wired
Intruder alarm module installed and connected.

I build this intruder alarm controller for my old apartment. It had two modes; away and armed. It was activated either with a key switch, or using the Security keypad with programmable PIN module. When the key switch was turned, a green and red LED started to toggle back and forth. If the key was turned back on green, the away mode would activate, if on red then the system would arm. The key switch and LEDs was mounted in status panel that I had in the apartment.

Table of content


The alarm buzzer could be turned on by other controlling modules, by activating the buzzer override input.

Mode 1, away

This mode had no alarm function. It just turned off the apartment lights, put the system in mute (no audible system failure alarms) and turned of the status panel that I used to control everything in the apartment. The intruder alarm controller just activated inputs on other controlling modules, that would, in turn, actually turn off and mute alarms and lights. If it was dark in the apartment then the light turned on automatically if there was movement in the hallway.

Mode 2, armed

Intruder alarm key and LEDs
Alarm, green and red LED, and key for Intruder alarm.

When activated the system counted down 60 seconds for me to leave the area. During this countdown the alarm and the green LED was flashing and a buzzer gave short bursts. The alarm would not arm if either the alarm or tamper input was triggered after counting down. If the tamper input was triggered curing the countdown, the buzzer switched to long bursts. When the countdown was complete the alarm armed, the status panel turns off, system was muted (well, not the alarm siren) and the apartment lights was turned off.

When the alarm was tripped I had 30 seconds to deactivate, or the siren would sound. The alarm and red LED flashed quickly, and the buzzer gave long signal bursts. If the tamper circuit was broken, the siren sounded instantly. If it was dark in the apartment, the light will turn on. The alarm LED would stay lit if the alarm had been tripped, until the system was armed again.



  1. PD0 Key switch N.O
  2. PD1 Key switch N.C
  3. PD2 Alarm trigger N.C
  4. PD3 Buzzer override
  5. PD4 Activate mode 1
  6. PD5 Activate mode 2
  7. PD6 Tamper N.C


  1. PB0 Alarm LED
  2. PB1 Green LED
  3. PB2 Red LED
  4. PB3 Buzzer
  5. PB4 Siren
  6. PB5 Lights out signal
  7. PB6 Away mode signal
  8. PB7 Heartbeat signal

D-Sub 9 pin

Connector 1

  1. 5V
  2. 0V
  3. Key switch N.O
  4. Key switch N.C
  5. Alarm trigger N.C
  6. Buzzer override
  7. Activate mode 1
  8. Activate mode 2
  9. +12V for status LED

Connector 2

  1. Tamper N.C
  2. Alarm LED
  3. Green LED
  4. Red LED
  5. Buzzer signal
  6. Siren
  7. Lights out signal
  8. Away mode signal
  9. Heartbeat signal

Please leave a comment or tweet if you have any questions or feedback on this project.

Schematic drawing

Intruder alarm circuit
Schematic drawing for intruder alarm; with AVR ATtiny2313.

Source code


A simple intruder alarm controller, written with BASCOM-AVR.

Master Releases

0 0 0 v1.0 Visual Basic 4 months ago

Image gallery

Parts list

Project: Intruder alarm system controller by Thomas Jensen is licensed under CC BY-SA 4.0 with attribution required.

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  •   Created Nov 02, 2007
  •   Last modified 5 days ago
  •   Project status: Completed