Using a standard switch as a momentary switch

I have a very nice non-momentary switch I'd like to use for a computer
project. The obvious problem is that I need a momentary switch, not a
normal one.

Any thoughts on how I can go about this? I'm trying to design a
circuit that would burst power when the switch is flipped for a short
time before cutting itself off, but no luck so far. Google isn't any
help either.

Thanks a bunch

wrote in message
ups.com...
I have a very nice non-momentary switch I'd like to use for a computer
project. The obvious problem is that I need a momentary switch, not a
normal one.

Any thoughts on how I can go about this? I'm trying to design a
circuit that would burst power when the switch is flipped for a short
time before cutting itself off, but no luck so far. Google isn't any
help either.

Thanks a bunch

Switch it off again

MJP

In alt.comp.hardware.pc-homebuilt wrote:

I have a very nice non-momentary switch I'd like to use for a computer
project. The obvious problem is that I need a momentary switch, not a
normal one.

Any thoughts on how I can go about this? I'm trying to design a
circuit that would burst power when the switch is flipped for a short
time before cutting itself off, but no luck so far. Google isn't any
help either.

Thanks a bunch

Usually, I'd just go down to Radio Schlock and pick up any of the dozen
or so momentary-contact switches they have, and use that.

However, a resistor/capacitor combo occurs to me to be possible; if you
don't need to press it very often. Put the resistor and capacitor in
parallel with each other, and in series with the switch. Each time you
turn the switch on, it will drop the voltage momentarily as the
capacitor charges. When you open the switch, the resistor will slowly
bleed off the charge on the capacitor. You *do* have to cycle the
switch both on and off each time, for this to work.

You have to pick capacitor size and resistor value to match the load
needed to act as momentary short. For that, try increasing values of
capacitor, starting with about .02uf up to small electrolytic (properly
polarized, of course), until you get a size that toggles the circuit
properly when applied across the desired switching mechanism.
Similarly, start with a high-value resistor like about one megohm and
decrease the value in decades (100k, 10k, 1k) until you get a value that
drains the capacitor in a reasonable time, without acting like a short
itself to the desired circuit.

But I'd just go buy a real momentary contact switch.
LOTS easier; and probably cheaper too.

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It probably would be cheaper to just use a momentary, but the switch I
wanted to use is a real antique, and it would be a shame to not use
it.

I have a working circuit using a 555 timer and a capacitor, I guess
that's as good as I'm going to get.
The circuit pulses 5v for about 1/8 of a second whenever the switch
changes states, which ends up working perfectly for me.