For better or worse, automobile alarm systems are a fast growing segment of the automotive aftermarket. This note briefly describes some of the more common systems, some ideas for future development, and how the MIC5010 family of high side MOSFET drivers can ease their design while improving performance and reliability.
The typical automotive alarm system consists of three main blocks: sensors for intrusion detection, the control unit, and output devices for alerting passersby or disabling the vehicle. Sensors vary from electronic ultrasonic intrusion detectors and audio devices (microphones and audio amplifiers) for vibration and glass breakage detection, through a mercury switch for motion detection, to electromechanical contact switches showing an open door, trunk or hood. The control unit is the processing device. It enables and disables the sensors and output devices, and knows whether an input is expected or is cause for alarm.