Due to my interests and to get more familiar with Arduino I got an idea to build security alarm device, which will detect movement (motion detection).

Components:

• Arduino MEGA 2560,
• PIR motion sensor,
• 4x4 matrix keypad,
• 128x32, 0.91inch OLED display module,
• Siren DC 5V 120dB,
• Breadboard power module,
• 2 LED (indicators).

I order needed items and start with work. First I was investigating about code and similar project which have been already done. After month or two, when I got all ordered components I started with real work (connecting all parts together in the system and coding).

I helped myself with following links:

• about PIR motion sensorhttps://learn.adafruit.com/pir-passive-infrared-proximity-motion-sensor
• about 4x4 matrix keypadhttps://learn.parallax.com/tutorials/language/propeller-c/propeller-c-simple-devices/read-4x4-matrix-keypad
• about OLED 0.91" 128x32 I2Chttps://protosupplies.com/product/oled-0-91-128x32-i2c-white-display/
• projectArduinoprojecthubMotion Sensing Alarm With Keypad & Passwordfrom thehack904https://create.arduino.cc/projecthub/thehack904/motion-sensing-alarm-with-keypad-password-53f05c
• project Circuit Basics How to use keypad on Arduino from Krishna Pattabiraman https://www.circuitbasics.com/how-to-set-up-a-keypad-on-an-arduino/

Basic principle or workflow:

• system can be in two states 0 - Alarm System is turned OFF (motion detection is not allowed) or 1 - Alarm System is turned ON (motion detection is allowed),
• by default system is always in state 1, which means even after losing of power supply (power down, power up), system is always prepared for motion detection,
• when you type correct password on 4x4 keypad system goes from 0 or 1 to state 0 or 1, depending on previous state,
• when movement is detected you have 30 seconds to type correct password, otherwise siren will start to work,
• if change of state is happened 0 -> 1, you have also 30 seconds to move out from PIR sensor or close the door,
• two LED indicators: first LED (in code signalPin) for detection and count down if password is correct and second for indicating when siren turns on.

Workflow diagram:

Of course there is possible to add also another modules, e.g. wifi module, GPRS module for remote communication or camera for face recognition. There are plenty ideas how you can improve your alarm system.

Notes:

• My first published project
• All outputs on display can be modified (format, size, output on display etc.)
• Code can have some bugs
• All opinions and reviews are very welcome

Thanks for your time and interest

Martin

EXPANDED TECHNICAL DETAILS

Scalable Perimeter Security Logic

A professional-grade alarm project that allows for the addition of multiple PIR motion sensors across different "Zones," all controlled by a central Arduino hub.

• Zone-Based Sensor Interrupts: Each PIR sensor is wired to a specific digital pin. The Arduino identifies which "Zone" was breached (e.g., Zone 1: Garage, Zone 2: Hallway) and provides a unique alert for each.
• Multi-State Alert Sequencer: Manages a high-decibel siren and a GSM module. The firmware handles "Silent Alarm" modes (text message only) and "Panic Modes" (siren and lights) via a physical keypad or remote switch.

Performance

• Verified with Arduino IDE: Optimized for 100% stability, with a software "Arming Delay" that gives the user 30 seconds to exit the house before the motion sensors become active.