active alarm without power consumption?

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Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=115440
Printed Date: July 02, 2025 at 8:18 AM

Topic: active alarm without power consumption?

Posted By: ludapower
Subject: active alarm without power consumption?
Date Posted: August 03, 2009 at 6:13 PM

Is it possible to have a setup where you have an alarm and once you break a wire, the alarm instantly goes off, yet when the wire is connected it doesn't consume any power from the battery.
Hopefully you can understand what I'm trying to describe.
Thanks :)

Replies:

Posted By: i am an idiot
Date Posted: August 03, 2009 at 10:04 PM

They do make Back-Up battery sirens. They do what you are wanting it to do. But it does draw a little current from the battery.

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Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

Posted By: howie ll
Date Posted: August 04, 2009 at 1:45 AM

Current draw on a battery back-up siren is negligable. And why not tell us what vehicle or alarm yu have or are considering, it might just be relevant.

Posted By: dualsport
Date Posted: August 08, 2009 at 8:35 AM

Negligible yes, but zero power consumption not really, since everything needs power to work.

If you simply use a transistor that's kept off by your monitoring wire keeping the input grounded, you could have it switch turn on when the wire's broken.
The input gets pulled up high, and the transistor turns on your siren.
The small amount of pullup current is the power that would be needed in standby, but it would only be 12 microamps if you used a 1M ohm pullup. Definitely negligible, but technically not zero. posted_image

Posted By: boxhead78
Date Posted: October 18, 2009 at 12:21 AM

regardeless to how you do it .it will take some power

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boxead78

Posted By: hotwaterwizard
Date Posted: October 22, 2009 at 9:37 PM

You can not get something from nothing.

Electrons must have a current to make it flow.

Think of a puddle of water sitting in a hole. Something must happen to make it flow.

The wind can blow and move the water but, wind is energy.

Gravity is also energy that can make the water flow.

Evaporation is another way to make water flow upwards but, it takes Heat which is also energy.

Perpetual Motion is a Myth.

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John DeRosa (Hotwaterwizard)
Stockton California
When in doubt, try it out !