[sdiy] Minimum parts count switch de-bouncer.

[Tim Parkhurst]

On 4/11/06, Dave Kendall <davekendall at ntlworld.com> wrote:
> Hi all.
>
> I've got a load of 406UBs, and quite a few CD40106s lying around. I found a
> schemo for a switch debouncer using 2 stages of a 4069, but it's inverted in
> output, so probably needs 3 stages, and works on  0V +5V. (will test it
> later tonight hopefully)
>
> Does anyone know of a debouncer circuit that will operate on GND and +15V
> that uses fewer stages of either a 4069 or 40106? (ideally only one stage,
> but that's probably pushing it...)
>
> I'm trying to get the parts count down for a control and audio switching
> board that I'm building for a DIY monosynth.
>
> The momentary switches I'm using are relatively good ("D6 type" from
> memory?), but rapid switching sometimes produces false triggers.
>
> cheers,
>
> Dave
>
>

Hey Dave,

The "circuit beans" site has a few good bits, including this
http://www.interq.or.jp/japan/se-inoue/e_ckt10_3.htm#2

Check under "chattering prevention." The circuit basically uses an RC
integrator (i.e. low-pass filter) and a 40106 schmitt trigger. Of
course, use one 40106 section if you want to invert the output, and
two if you don't want to invert. The 40106 helps ensure that a nice
clean pulse is produced (sounds like you already knew that).

The circuit above shows a switch that connects to +V, the R and C tied
to ground, and then two 40106 sections. This arrangement produces a
nice, clean transition from GND to +V when the switch is pressed. You
might be able to save one inverter section by hooking the R and C to
+V, and letting the switch connect to GND when it is pressed. Seems
like it should work, although I haven't tried it. Probably worth a few
minutes on a breadboard to check it out.


Tim (new band name: "A Few Minutes on a Breadboard") Servo
--
"Imagination is more important than knowledge." - Albert Einstein