How do i use this relay?
Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=18839
Printed Date: May 17, 2025 at 1:37 PM
Topic: How do i use this relay?
Posted By: burnerofhells
Subject: How do i use this relay?
Date Posted: September 12, 2003 at 4:29 PM
I want to hook up some more sirens to my car alarm and a backup battery. My car has a factory alarm with a siren already. I figured i should hook the relay up to the power sorce of the factory siren and use it as a trigger for my other sirens to go on. How should i hook up a relay for this? I have a SPDT Relay .
Replies:
Posted By: Rox0rz_Carz0rz
Date Posted: September 12, 2003 at 5:33 PM
just hook the new sirens in parallel. don't worry about a relay as for backup battery. a nine volt usually works use use some diodes (it might be a good idea to run a couple in parallel instead of just one if ur using multiple sirens.  ------------- Did Anybody Order A Pizza?
Posted By: Rox0rz_Carz0rz
Date Posted: September 12, 2003 at 5:43 PM
sorry, didn't look like the last pic loaded. here: https://roshfe.com/pulsarnx/scripts/xfer/Docs/Teh_Rox0rz_Carz0rz/siren.JPG  but if u are worried about current draw (if the factory siren is wired straight into alarm "brain" without relay) you will want to use a relay. a simple automotive relay will work https://roshfe.com/pulsarnx/scripts/xfer/Docs/Teh_Rox0rz_Carz0rz/siren_with_relay.JPG 
------------- Did Anybody Order A Pizza?
Posted By: burnerofhells
Date Posted: September 12, 2003 at 7:54 PM
The pictures help a lot, thanks. I think i am going to use the relay as im a little worried about the brain. How would i wire in the relay and a backup battery? I dont want the backup battery to be in use unless the main car battery wires get cut. How could this be done?
Posted By: Rox0rz_Carz0rz
Date Posted: September 12, 2003 at 8:29 PM
sorry, I just looked at that diagram again. It wouldn't work. (I designed and built my own system from the ground up, and it's wired a little different than factory stuff and i'm skipping steps here - sorry) ok: here yah go! - the only problem with this model is that the relay on the backup battery will be on at all times, even when the alarm is disarmed, car is off, etc. https://roshfe.com/pulsarnx/scripts/xfer/Docs/Teh_Rox0rz_Carz0rz/it_works.JPG very confusing diagram, but i don't feel like taking the time to make it good  ------------- Did Anybody Order A Pizza?
Posted By: burnerofhells
Date Posted: September 12, 2003 at 8:35 PM
I think i get most of it. Why does it say additional realys at the bottom left? You say it that one realy will always be using power, just how much? Wil it be draining my backup batt or my car batt? It is very minamal to the point that i shouldnt care?
Posted By: auex
Date Posted: September 12, 2003 at 9:24 PM
Ok, if your going to do it that way then the sirens will always be getting power and SOUNDING from the battery. First, it is worth buying the right parts if you are trying to protect your car. Go buy a back up battery that is specifically designed for this purpose. If you don't want to buy a BUB then buy a back up battery siren. As far as adding sirens most alarms can power two sirens, if you want to add more then wire a relay like this
The wire labeled remote turn on lead would be the alarm's output for the siren, the additional accessories would be the additional sirens. A relay can support upto 30 sirens. ------------- Certified Security Specialist
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Posted By: Rox0rz_Carz0rz
Date Posted: September 12, 2003 at 10:11 PM
sorry dude, it's supposed to say "additional SIRENS" and accually that diagram would work. they would NOT be on constantly (it's true ;) ) since the 86 pin is connected to the (+) for the siren, it will only flip when the alarm sends power to that factory siren. I have seen complete alarms (cheap ones) built into the siren (brain and all) in which case it has constant power going to it at all times, but with a factory alarm system, that (+)12v on the siren is only hot when the siren is wailing. mmmmm. big long complicated sentence to say one simple thing. I like it :-) ------------- Did Anybody Order A Pizza?
Posted By: Rox0rz_Carz0rz
Date Posted: September 12, 2003 at 10:20 PM
**additional note** the relay for the backup battery is being used as a NC rrelay (87a and 30) so, as long as there is constant 12 volt power powering that relay, no connection is being made, and the sirens will be silent. As soon as that 12v supply is disconnected (i.e. battery removed), that relay will snap shut, completing the circuit, and activating the backup battery. (The additional diodes are used to protect the 9v from a 12 surge that could destroy the battery since relays need time to flip over once power is reconnected and such) and like I said, ignore those first two diagrams. I'll be deleting them off the servery anywhoo. they are useless :) happy wiring! ------------- Did Anybody Order A Pizza?
Posted By: burnerofhells
Date Posted: September 13, 2003 at 1:43 AM
OK, ONE LASt thing. You are using 9v batts in your diagrams, what would the advantage of that be over running 2 6v batteries in series to make 12v? The sirens i have are 12v sirens and im not sure how well they would run with only 9v. Your not talking about using one of thoughs tinny 9v batteries are you?
Posted By: Rox0rz_Carz0rz
Date Posted: September 13, 2003 at 10:00 AM
meh, that's what i'm using. it's small, and compact (i don't have much room inside my car), and it does the job - since if someone unhooks the battery, and hears the alarm ring, they usually hook it back up again hoping it will stop. mine won't but i'm not sure about the factory guys two sixes will defenitly give you more power (and for longer - if u have the room) . but yah, if u have room for two sixes, y not just use a 12v motorcycle battery? you can hook it up to ur charging system easily, and they really don't take up alot of room. Just a thought . have fun ------------- Did Anybody Order A Pizza?
Posted By: burnerofhells
Date Posted: September 14, 2003 at 1:21 PM
I was thinking and what happens if the battery is cut and the backup kicks in. When i disable the alarm will the sirens stop and the system restart or will the sirens keep going off the backup battery?
Posted By: burnerofhells
Date Posted: September 15, 2003 at 8:46 AM
Another question, what size of diodes do i need? I dont really know much about diodes so i have no idea what size i need.
Posted By: Rox0rz_Carz0rz
Date Posted: September 15, 2003 at 11:04 AM
just make sure they can handle the current of your combined sirens. usually estimate for a little more too. as for the backup battery keeping the sirens going, you'll have to make sure that the power is hooked back up before disarming the alarm. then (yes) they will stop. note: you will have to unhook the sirens before you disconnect power to work on your car, even if the alarm is disarmed. and such. ------------- Did Anybody Order A Pizza?
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