AlarDuino: car alarm Arduino shield
It uses accelerometer, PIR and temperature sensor to detect breaks in the car environment. The shield activates an external 12V siren as the one shown in the pictures. This project design will be updated in its GitHub repository.
Two potentiometers allow to set the sensitivity of the accelerometer and temperature sensors. The PIR sensor has its own potentiotemeter to set its sensitivity.
A buzzer is integrated in the shield for debug purposes, once you have the system programmed and tested, you can ignore this buzzer. The led light can be programmed to flash every 10 seconds, reducing its power consumption.
The whole system, powered by a 12V battery (using LM7805 5V regulator) has an average current consumption of 10-12mA when the siren is off, and approximately 70mA when the siren is on.