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