Does NE1 know how I can find a 12V source for alarm trigger?
 

I am trying to complete a project to add a siren in the car to assist in protecting my new aftermarket headunit. I cant find a trigger for a relay when the OEM siren is on. I tested the wires on the siren harness but the trigger for the alarm is just a pulse. It cant be used to trigger. Thanks all.

Pics to follow of new HU Pioneer z110bt.

Why do you need to add to the OEM alarm? It has the ultrasonic interior sensor and everything already... If you want the appearance of an aftermarket alarm just add a blinking blue LED on the dash, activated when key off etc.

Wanted to add a siren...
 

Wanted to add a siren or 2 behind the head unit for deterance. It will be tough for a thief to steal my aftermarket radio (value $1600) with 2 sirens blarring in your face.

I would prefer a thief to not tear up the dash trying to rip a radio out. Less time in the car the less damage they can do.

Things that I gotta do to live in NYC.

I did get aftermarket car audio insurance but I just want to minimize the interior damage if it occurs.

Thanks.

Hi have a look at this relay.PAC TR7 UNIVERSAL LATCHING/TIMER/PULSER RELAY MODULE I have used these with a positive or negative pulse and they also have an adjustable time on for the relay. It sounds like it would do the job for you cheers Rondo.

Hi Rondo...
This may work. I just want to confirm with you before I purchase since you sound very knowledgable about this topic.

I tested the wire from the X that I will use as the trigger. It measure the wire while disconnected from the siren and it was 12.3V on standby. Once the alarm is triggered ON then it drops down to almost no voltage. It stays this way for about 30 seconds or the duration of the siren. The siren automatically shuts off after 30 seconds although the lights might remain flashing.

When I tap this wire and put it onto the trigger wire of a 5 pin Bosch relay it drops the voltage all together. Disconnecting the tap brings it right back to 12.3V.

Does this sound familiar to you and will the TR7 work in this scenario?

Thank you very much for your assistance.