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Newbi Alarmed by this site

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nudgie

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Hi All, just found this site and it looks great, load of info all most too much to look through, so appolgies if there is a circuit on here somewhere.

I am after some help my electronics is limited and is about 30 years old, however it looks as things don't change that much, looking at some of the circuits I have seen, anyway I am trying to build a simple car alarm for one of my sons car. Years ago I built one for myself using a couple of 555 timers. Now I have forgotten how I did it, to my amazement they are still around.

What I want to acheive is :-

To use the 12v from the door light switches to trigger the circuit, which will via a relay switch on the horns and lights for a predetermined (adjustable) time say 2-10 mins, then resets, irrespective of wheather the doors remain open or shut.

I want to be able to set and disable the alarm via a switch from inside the car so it needs to have an entry and exit timer (adjustable would be nice).

I have found this circuit which looks like it does what I want, but it looks like the relay stays on all the time until disarmed i.e no timer, but I am so rusty, is my undertanding correct, could someone just talk me through the circuit, and how to time the alarm on preiod or suggest something better..

So looking at this circuit, from memory R1 + C1 and R1 + C2 adjust the delays (but don't know how to calculate them)

Switch on alarm by closing S1
Open S2 to arm
timed delay for exit (R1 +C1)
(open and close door with no effect within the time delay)
Delay time elapsed
open doors
timed delay for entry (R1 +C2) starts
timed delay for entry ends
relay powers up (reains on until S2 is closed)
Close S2 disarmed

Thanks in anticipation Keith

PS: got another problem/project anyone know anything about CAN BUS's in cars, differnt car I hasten to add..
 

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nudgie

New Member
Hi Thanks for this I think (Micro-controllers) Hmm go on then point me somewhere, not oppossed to learning curve but this was just going to be a very quick cheap alarm .... not re engineered Cobra although it certainly do with it...
 

tcmtech

Banned
Most Helpful Member
Just have you son do what I did. Drive the oldest ugliest piece of junk around. No one will even think about stealing it or even breaking into it! :(

If it needs an alarm its to expensive or you have to much junk inside!:p

Plus having a eye sore car that stands out keeps him out of trouble simply because everybody will remember what vehicle was at the site of the crime!:eek:
 
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