DEI mini piezo siren install question

there is no way to have the piezo only go off when the alarm is going off? for example, somehow (and im not sure how) make it so that the piezo doesnt receive the warning chirps from the dual stage shock sensor, but only receives the full siren sounding? because, in this case, if the alarm is already sounding it wont matter if the glass break sensor picks up the noise from the piezo.

or (and i really DONT want to do this) what if the warn away stage on the shock sensor was disabled? would the piezo still interfere? i believe the chirps upon arming the alarm shouldnt be a problem as there is a few second delay after you arm the 791 until sensors can be triggered. like i said though, i really dont want to disable the warn away. but im just trying to figure out if the warn  away is my only obsticle in this piezo thing not being able to work.

is there a way to hook up a relay to the siren output of the alarm to power the piezo, but between the relay and the piezo have a time delay box on either the + or the - wire so that the box has to be powered up for X amount of time before it lets power through to the piezo? say for example a 5 second time delay? this way the warn away will not trigger the piezo, but if the siren goes off, after the first 5 seconds of being in an alarmed state the piezo will start going off. this way, the arming and disarming will not activate the piezo, and the warn away will not activate it either.

i know for Air Conditioning units for homes they have time delays installed that you can adjust (i was an AC tech for a few years), but i just am unaware of time delays for DC power in cars.

anybody know, or can you point me in the right direction? would this idea work?

there is not a horn output. only a siren output on the 791XV. however, this siren output can be programmed as pulsed (to run a factory horn instead of a siren) or constant (to run a siren). perhaps this is what you were thinking about?

at any rate, i have to use the siren output if i want the piezo to go off when the alarm sounds. however, im worried about the dual stage shock sensors warn away tripping the glass break sensor.

well guys, here is what i ended up doing...

i tried this first (the suggestion of bobk) , then i realized a flaw, so i changed it, but still used the same idea - however, i think this way works much better. hopefully somebody else can use this in the future.

original suggestion from bobk that gave me the idea using a relay;

pin 30 -- piezo (+) wire  [in addition, ground the (-) piezo wire to the chassis]

pin 87 -- +12v

pin 85 -- positive door trigger (if you have a negative door trigger, use another relay to reverse the polarity. i had to do this)

pin 86 -- negative armed output wire on alarm

well, the idea behind this is for the piezo to sound when the alarm is armed, and the door is open. this way, it doesnt sound the piezo siren upon arming and disarming. nor will it sound the piezo when the warn away dual stage shock sensor goes off (thus setting the alarm into full alarming mode by disrupting the glass break sensor and/or shock sensor.)

this works, except i found a flaw. what if a thief breaks in, opens the door, panics, and runs away leaving your door open. say your car is parked in a remote lot all day. well, the alarm only sounds for 30 or 60 seconds (depending on how you programmed it) then the siren shuts off. however, your piezo will continue to sound for an infinate amount of time, and will only stop sounding when you return and DISARM the alarm, OR when your battery completely DRAINS - whichever comes first. if you are at work for 8 hours and leave your car in the metro parking lot, you will surely return to a dead battery. i did  not like this option.

so i decided to modify the suggestion, but still use the door trigger as the method of determining when the piezo is sounded.

my method is as follows;

pin 30 -- piezo (+) wire  [in addition, ground the (-) piezo wire to the chassis]

pin 87 -- +12v

pin 85 -- NEGATIVE door trigger (if you have a positive door trigger, use another relay to reverse the polarity)

pin 86 -- + input from siren output of alarm ***(note, my door triggers are negative, but when you close the door the wire has a positive charge. this positive charge backfeeds through the relay and makes the siren sound very softly (its not much voltage). so if your door is closed, the siren constantly sounds regardless of the alarm being armed or disarmed. this is easily fixable with a diode on the siren wire)

this new method i used to wire up the piezo ONLY sounds the piezo when the door is opened, AND the alarm is going off. this way, if a theif runs away and leaves your door open, the piezo will only sound as long as your regular siren is sounding, then it will shut off after the 30 or 60 second alarming state, thus not draining your battery.

what do you think bobk? is this way better?

i figure if the theif is still there 10 minutes later, and has opened the door 3 times so far, then he probably is not leaving, or has figured something out (disconnected the battery terminal or cut some wires). if he is there for that long, and the alarm hasnt deterred him, i doubt it will if it goes off longer.

its like the old handgun saying (i carry a conceiled weapon and my magazine on my .45 online holds 8 rounds instead of 10). when people ask me if id rather have a 9mm because the magazines hold 10 rounds, i tell them "well, if im ever in a situation up against so many people that 8 rounds isnt enough, then i dont think 10 rounds would save my ass either, and id probly be dead in that situation anyways"

haha, not quite the same, but you get the idea.