What I am looking for is a switch that when pressed stays closed for x seconds and then opens. For a 1.5-9V circuit.

Does such an animal exist ?

Thanks
Marc

This circuit called monostable multivibrator.

you could also rig a 555 timer circuit with a couple transistors.

Thanks, I figured I could use the 555 but I'm really trying to keep this as simple as possible (maybe the 555 is ?)

Basic idea is simliar to the timer on a washing machine. Turn it to the desired time, push the switch and circuit is closed for that duration.

Same idea just much smaller and only need run for 10s or so.

But...if a switch like this doesn't exist then it doesn't exist.

In that case, having not yet played with the 555, a couple of questions:

-Do I need to hold pin 2 high (1/3V) or is that done internally ?

-What is the best (simplest) way to generate the trigger pulse? I'm assuming a momentary contact switch but how to I make the pulse negative ?

Thanks for bearing with me. I'm new to this stuff.
Marc

Just saw another post in the general discussion group that may answer my question on the 555. He has a n.o. momentary contact switch connected between pin 2 and ground. Would this work ?

Follow on question: Does the circuit consume power at all between timing pulses (i.e after output goes low) ?

Thanks
Marc

Nigel said:

If you have a look at http://www.uoguelph.ca/~antoon/gadgets/555/555.html it contains a really good 555 tutorial

Thanks Nigel. That is an excellent tutorial!

Yes, it will consume power at all times,

I figured as much. For this particular application I'll just put in a switch to turn on power to the 555

Thanks
Marc