Switch debouncing

[Abstract Dissonance]

Notwithstanding what Ben Bradley said about an R-S flip-flop if it gets
multiple "sets" or "resets", to answer your debouncer question, lose R2,
and go directly from the switch to ground:


That will immediately discharge the capacitor, and with the Schmitt, it
doesn't matter how long as it takes to charge, as long as it's quicker
than the next time they push the button! ;-)

yeah. I was using low values of R2. I think I put it there to limit the
current and to actually see the thing charge.

There are also "Jeopardy buttons"-type circuits on the internet, which
would give you your lockout, but with independent buttons, you might
even not need that much logic - there isn't going to be any competition
between the buttons, so you don't need a priority resolver, just a - OK,
I think I've got it.

I'm not familiar with that.

Take another capacitor, from the switch/R1/cap/ST junction, about 1 nf,
and on its other side, put a 1K or so resistor to +Vcc. Condition that
with a couple of diodes, (one each to +Vcc and to ground, reverse biased,
of course - this clamps the spike), and send it to the "reset" of _all_
of the flip-flops. It resets them, and then the "set" signal from your
button sets the target flop.

Kewl! I'll try not to dislocate my elbow patting myself on the back.

heh. Ok, I'll try it and see what happens. So basicaly you are making a
filter and a using a diode as a sort of voltage limiter(so basicaly the
bouncing will have to overcome the diode but since you put a cap and
resistor there to reduce the voltage and filter it it will not have enough
to do it?).

Cheers!
Rich

Thanks again,
AD

 

[[email protected]]

I still think you need that reset button. Consider the blender again.
There must be a button to turn it OFF instead of just changing speed.
Unless of course that is not important in your application. Don't you
usually find something like:

[ 1 ] [ 2 ] [ 3 ] [OFF]

Well, the problem was that I was originally going to have it so n buttons
acted like a group. You would make a button combination to select a preset.
So with n buttons one would have 2^n potential combinations... then I
figured that it might just be to much trouble to do that and much easier
just to have one button per preset but got hung up on the debouncing stuff.
Its still something I want to look into though since its been pretty
interesting.

Thanks for the help though.

In that case, have you considered using a rotary switch for this? I
know it's a mechanical solution but those mini rotary switches are
really small.