Simple security alarm using Arduino

A simple security alarm was developed in two consecutive workshops at Techno e School.

1 Workshop Part I on Sunday,3rd Jan 2016

1.1 Alarm specifications:

The alarm project is a FREE project. The details of the security alarm were discussed in the workshop on Sunday, 3rd January 2016. They are:

  • Per unit (customer) price: Rs. 1000=00
  • Separate model for window and door.
  • Magnetic sensor and reed relay to be used.
  • Automobile ignition lock-key for activation/deactivation
  • 30 seconds delay for the owner to deactivate the door alarm
  • 3 seconds delay for window unit to avoid noise triggering.
  • Atmega 8 used as cpu.
  • crystal freq 8 Mhz
  • Use Arduino language to write software
  • PWM pins used to produce sound
  • Because it is a FREE project; the drawings, circuit designs will be released under creative commons license and software will be released under GNU GPL license.

1.2 Expected operation

There will be two modes of the alarm.

  • Window mode
    • Fitted to the window.
    • When a burglar breaks open the window, reed switch is open and sends signal to the controller
  • Door mode
    • Fitted to the door
    • When the owner activates the alarm, it is inactive for 30 seconds, so that the owner can go out without sounding the alarm.
    • When the owner comes into the house through the door, the alarm shouldn’t sound.
    • When a burglar breaks open the door, the alarm will sound after 30 seconds.
    • If the burglar breaks in and closes the door again, the alarm must start after 30 seconds delay because (s)he doesn’t have the deactivation key.
    • The owner must deactivate the alarm (using the ignition switch type deactivation) within 30 seconds after (s)he enters the house through the door.

1.3 The hardware

  • Atmega8 cpu
  • 8 MHz crystal
  • Mode switch to decide the door mode or window mode (input)
  • Magnet-reed switch pair to sense window/door breaking (input)
  • Speaker to sound alarm (output)
  • Battery as power supply: 9V or 12V
  • Voltage regulator
  • Reset ckt for controller
  • Power transistor to drive the speaker
  • Ignition switch for system activation/deactivation

1.4 The flow chart

  • One of the participants of the workshop, Abhijit Tikore had sent a flow-chart for the above logic.
  • We expect others to send their logic in the flow chart form.
  • When flow-charts are available from other participants, we will discuss them in the second part of the workshop to be conducted on 17th Jan 2016.

2 Workshop Part II on 2016-01-17 Sun

Participants did the following in this part:

  • Abhijit Tikore sent a flow-chart after the workshop-Part I. Omkar Desai modified it.
  • Sneha wrote the sample code in Arduino Language.
  • Omkar Desai provides the hardware circuit diagram using “Dia” software on linux.


  • After modifications, final code in the zip form can be downloaded here.

Get yourself or your engineers trained in our workshops to manufacture simple security alarm.

%d bloggers like this: