Run-on timer circuit

Thread Starter


Joined May 28, 2008
Hi all,

Been trying to think up a way to be able to activate my car alarm system while the turbo timer is still running.

The problem is the turbo timer holds on the ignition power,thus not letting the alarm system arm because its still reading power from the ignition.

i thought up a crude little method of switching the alarm ignition wire onto a pole on the ignition switch which is not held on by the turbo timer,however this pole drops out when the starter signal is being applied,therefore the alarm will register no ignition and activate the immobilisers not letting me start the car.This is where my expertise stops & hopefully u electronic geniuses can help me.

To overcome this i need a 10 sec run on timer to be triggered by the loss of power(12V) on this wire that will then hold on the ignition feed to the alarm(which i will power from constant supply elsewhere thru a relay) for 10 secs,allowing me to crank the engine.I cant see myself ever needing to crank the engine for longer than 10secs.

So, power goes off > triggers timer(fast trigger) > holds relay on for 10secs(does not need to be accurate +/- 2secs ok) > turns relay off.

Any ideas of how to build this circuit & with what components?

Thanx kindly
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