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Since most of us know the alarm siren on the Crossfire causes problems with battery drain when the circuit board batteries corrode and fails. It is easy to disconnect and just ignore the siren, or get an OEM replacement. As my wife is quite aware, I never seem to take the easy path and would rather find a complicated solution. With that being the case, I decided to design and build my own alarm siren. I initially tried to decode the Single Wire CAN signal that the original alarm uses. The documentation on this system does not seem to be available. If anyone has that information, I would still like you to let me know where I can get that information. Lacking the details on the CAN, I decided that the inputs I needed would have the be a little crude. I selected the fog lights flashing to trigger my theft alarm signal and the relay that flashes the parking lights when the car is locked/unlocked for the lock/unlock signal. An ignition on signal tells the alarm to ignore the inputs when the car is running. I am using an Arduino 328P Mini Pro as the controller, an MP3 player module for the sound effects and a five-pin audio amp for the output. The amp is powered through a voltage boost controller module to increase the 12VDC available to 30VDC to allow higher wattage output from the audio amp. The entire system spends most of its time in sleep mode and draws <1mA while asleep. When a signal is received, an interrupt is generated to awaken the processor and identify which tones to play. The program for the controller is written in C++ using several libraries to handle the details. I am attaching photos of the alarm which is housed in an old computer speaker I had laying around. The PCB was designed in EasyEDA (free to download) and purchased from JLCPCB (PCB Prototype & PCB Fabrication Manufacturer - JLCPCB). The components are all very common values and can be purchased just about anywhere. This is the 12VDC to 30VDC boost controller Lower left is the MP3 module, lower right is the 328P Arduino Mini-Pro, upper left is the audio amp, upper right is the quad-opto-isolator for inputs from the car and to turn on the P channel MOSFET that controls the boost module. Other side of the PCB. Mostly used for power and filtering. EasyEDA schematic of the alarm. Free to use or modify. No warranties or guarantee of fitness. Overall view of the alarm in the computer speaker housing.
DIY Alarm/Siren replacment
