Soften Siren Chirp?
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=20031
Printed Date: July 16, 2025 at 6:57 AM
Topic: Soften Siren Chirp?
Posted By: yakky
Subject: Soften Siren Chirp?
Date Posted: October 13, 2003 at 6:28 AM
I just installed a Crimestopper CS-2001RS, great unit, no hassles with the install, sick range! My only problem is the siren chrip... sounds a little bit like Smokey's mom's Pinto in the movie Friday. I'd like to soften up the chirp quite a bit. Any ideas of how to do this without affecting the siren output (which is pretty damn loud!). I know I can get another siren but I'm on the cheap here.
Replies:
Posted By: daniel2002p
Date Posted: October 13, 2003 at 12:37 PM
Give your siren a bad ground or put a resistor on it!
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1.8L VVT-i I-4
Always double check your wires with a DMM!!!
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Posted By: k2thz
Date Posted: October 13, 2003 at 12:49 PM
Do you want to change the tone/sound or just the volume? If just a volume change, then you'll just need a resistor. Make sure you measure the current going into the siren first.
The siren's output will probably vary logarithmically with the current through it; i.e. if you drop the current by 10%, the output will drop by half. So calculate the current you want based on the volume decrease you're after, and use a resistor to reduce the voltage drop across the siren...
THE BELOW IS ONLY A 1st-ORDER CALCULATION!
Say your siren draws 1A, for ease in calculation.
If you want 50% output, you'll want 0.9A or 900mA.
To get 900mA, you'll want 90% of the existing voltage drop.
90% of 12V is 10.8V.
So at 900mA, you'll want the resistor to drop 1.2V.
So V=IR or R=1.3Ohms.
Keep in mind that at 1.3 ohms and 900mA the power dissipated by the resistor is 1.17 watts. So don't go sticking a little 1/4-watt resistor from radio shack in there! You'll probably want two 1-ohm resistors in series, and you'll want at LEAST 1-watt resistors. I would go with two 1-ohm, 2-watt resistors in series.
Of course, this gets very interesting if the siren draws different amounts of current at different frequencies! I won't even go there...
DDR
Posted By: yakky
Date Posted: October 14, 2003 at 6:42 AM
Thanks for the info guys, what I was looking for was something to soften the chirps, not the siren output. It came to me while I was in the gym, use resistors for one feed of the siren, then use a relay with a resistor and cap to switch on after 1 second to give full siren output.
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