| T O P I C R E V I E W |
| pityocamptes |
Posted - Jan 24 2007 : 12:16:39 PM
I was wondering if anyone has a simple circuit for a car alarm delay. I would like the alarm to activate when a push pin grounds, once the door is open, and then sound a 140db piezo speaker within the interior of the vehicle until the on/off swith (hidden of course) is turned off.
I would like the circuit to operate by a hidden switch inside the car (on/off), and allow a time delay of a few seconds so that the door can be closed (depressing the pin) and then the alarm arms. If the door is opened (pin grounds out) the circuit has a built in time delay of a few seconds so that the switch can be turned off so that the piezo does not sound.
I have tried using a few 555 timers but can't figure out how to get an initial delay so that the door can be closed (then the circuit arms) and also cannot figure out how to set a secondary delay, once armed, that allows the circuit to be disarmed once you get back into the car before the piezo sounds.
Any thoughts, or circuit someone could post? I would really appreciate it! Thanks again!!! |
| 4 L A T E S T R E P L I E S (Newest First) |
| Aaron Cake |
Posted - Jan 28 2007 : 10:57:11 AM
quote:
Originally posted by pityocamptes
Thanks, the problem for auto detect if door is open is that I have an older vehicle that does not have this feature  Any other thoughts? Thanks again!
Does the car have a courtasy light that illuminates when the door is open? If so then it will have a switch in the door frame that grounds one side of the light when the door is open. You can use that signal to detect the door open.
Or you can aldd your own switch. |
| CurrentOverflow |
Posted - Jan 26 2007 : 11:07:29 PM
After almost a days thought heres the best idea ive come up with. Hide a light dependant resistor somewhere and when your car door opens a light goes on which triggers the ldr and turns on the circuit. The only other thing i could think of is running a current through the door and when the door is opened that circuit also opens which would switch a relay back or something. Best ideas i got
Good Luck! |
| pityocamptes |
Posted - Jan 24 2007 : 6:13:37 PM
Thanks, the problem for auto detect if door is open is that I have an older vehicle that does not have this feature Any other thoughts? Thanks again! |
| CurrentOverflow |
Posted - Jan 24 2007 : 5:30:09 PM
Heres just an idea.
555 timer, 4017. Adujust it to the speed u want and put a relay on the 10th output :)
the switch just turns it off.
To activate it hmmmm, dont take this seriously but i think theres already somehting built into the car that finds out when a doors been oppened, maybe you can hook it up to that somehow
well i tried , im not sure if a 4017 can trip a relay but ah well :) |
