How to trigger on releasing a push button?

thecritic said:

I am trying to design an automatic Door Bell curcuit.
I will be hiding a large push button under a door-mat. Whenever someone steps over the door mat and then moves out, I want the door bell to ring for some time and then stop. Please keep in mind that the door bell should start ringing only after the person leaves (after the push button is released).

I know that there are ICs that meet my demands. But I would like to do it as simple and as cheap as possible. I can afford a couples of relays (I already have) and large or small capacitors and some resistors. I am in no way able to buy a couple of ICs.

So, this is in some way a problem of economy too. Otherwise it would be very simple to do what I want by using, say, a microprocessor.

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Gary B said:

Here is a simple circuit using a slow release relay and a DC bell.

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thecritic said:

I have just got an idea, but need some improvement. I need to use a double push button. Can you see some way round for using a single one.

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