[Coco] Re: OT request

John E. Malmberg wb8tyw at qsl.net
Sun May 23 00:11:32 EDT 2004

Dave Kelly wrote:
> This is the only group of electronic people I know so this is where I 
> ask this kind of question.
> I want to hook my trailer into the panic alarm on my car. What I would 
> like to happen is;
> The door lock button on my key ring would activate the alarm device.
> The door unlock button would deactivate the alarm device.
> The alarm device would be attach to the trailer. When I lock the doors 
> of the car to go fishing, the alarm device is turned on.
> Someone comes along and starts fooling with the trailer. A mercury 
> switch causes a signal to be sent to the panic alarm on the car cause it 
> to go bonkers.

To hook into an existing alarm system requires the schematic of it and 
operational details.  And that may be something hard to get.  This is 
intentional on the part of the car manufacturers.

Tampering with such a circuit could result in permanent damage to it.

It is probably easier to rig up a second system.  Vibration sensors are 
easy to get, and it is probably easy to hide some batteries, a siren and 
a switch on a trailer.  After all, no one is going to expect a system. 
Once it is triggered, the idea is that you expect the perpetrators to flee.

Also in the case of theft of the trailer, having the alarm going off on 
the car is not going to be much use as the trailer is being hauled away.

When the alarm goes off, they will either not be concerned about it, or 
will not have time to try to figure out what other surprises that you 
might have in it.

Tricks can be done so do discourage someone from thinking that they can 
stop the alarm by cutting a wire.  Extra dummy wires with the real wires 
hidden, multiple small sirens hidden with a visible dummy siren.

Either they have plenty of time, in which case the alarm is meaningless, 
or they will flee at the first alarm.

Also make sure that there is a timeout, or is not activated anywhere you 
can not get to it fast.

Also some experts think that a sound effect of a woman screaming for 
help will get more attention than a siren.

Personal Opinion Only

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