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switch that stays closed for a specified time period

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marchache

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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
 
Switch question

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
 
Switch question

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
 
Re: Switch question

marchache said:
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 ?

If you have a look at it contains a really good 555 tutorial.

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

Yes, it will consume power at all times, there are various ways to reduce power consumption - one way would be to use a PIC microcontroller, putting it in 'sleep mode' to minimise consumption, and using the 'wake up on pin change' feature. But that's probably getting too difficult for you, a CMOS version of the 555 would reduce consumption considerably, and could be worth a try.
 
Nigel said:

If you have a look at 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
 
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