turn on dashcam when alarm goes off?

Hi, I have a 2 way Compustar alarm (Compustar 2w900fm) and recently picked up a nice little 1080p dash cam. I have it wired to a switched 12v source and it works great. However, my car was hit and ran twice in the past 6 months. Luckily, a witness left a note the 2nd time and the offending driver had to pay. Leaving my dashcam running with the car powered off will drain the car battery below 12V just after 2 days according to my calculations. Sometimes my car sit for 3 days at a time. I'm trying to figure out how to make my dashcam turn on whenever my alarm is set off. I'm guessing I would need to wire up a relay to the alarm and have that turn on the camera, however I don't know where to start. Any help would be appreciated. Cheers!

If you have a CM6000 brain, CN3 Pin 20 is a +12V Siren output.  You could try that as the +12V power source for the camera.  You

can program the CM6000 for siren output duration ( 30, 60 or 120 seconds ) with Menu 3-07.   The only down-side is this wire also goes to +12V briefly with a lock, unlock & start depending on Menu 3-09 programming.   Additionally, if you have the OP-500 Programmer, you could reprogram an unused POC as a Type 20 - Siren2 output.

Not sure if a relay would be required, depends on the cameras current draw, but it wouldn't hurt.  Here is the relay wiring :

Relay Pin 85 to Chassis GroundRelay Pin 86 to CM6000 CN3 Pin 20 Brown wireRelay Pin 87 to +12V with fuse appropriate for cameraRelay Pin 30 to camera + wireRelay Pin 87a   Not used

Soldering is fun!

Thanks for the detailed and quick response! I'll dig into the alarm manual to confirm the brain model and the output pins. The reason I am asking about a relay, is that I also want the dashcam to run when the car is on when it powered by a switched +12v, not only when the alarm is on. Does that change your answer? Also, is there a specific relay type I need to be looking for?

The relay is a standard Bosch style 30/40 Amp SPDT relay.  Use the relay and connect the switched +12V to Pin 30.  Probably want to put a quenching diode across the relays coil.  1N4007 diode on Pins 85 to 86 with band towards Pin 86.Soldering is fun!