Car-Alarm-Delay

OK, so I bought this car alarm. It’s nice and all, but it has this really irritating habit of chirping every time I activate and deactivate the alarm. I keep odd hours, so I have no interest in bothering my neighbours with the chirping in the night.
Unfortunately there is no way to disable this feature.

So what does a fellow do then? He of course finds a solution to the problem. In this case a simple delay on the alarm output did the job.

Here is the schematic
alarm-delay

The NE555 is really a versatile IC. In this configuration it works as a delay on trigger. As soon as the alarm output is activated, the NE555 is supplied and the timer is started. the delay is calculated as R1*C1.
After the defined time has elapsed, the NE555 output is activated and Q1 is supplying the output and the LED.

Rather simple isn’t it 🙂