[sdiy] faulty switch causing bounce?

[Harry Bissell]

I saw the hex switch MC14490 debouncer IC at Electronic Goldmine yesterday. Other than there, the part is
extremely rare IMHO (out of catalogs for maybe 20 years ?)

H^) harry


----- Original Message -----
From: John Speth <John.Speth at coherent.com>
To: Synth DIY <synth-diy at dropmix.xs4all.nl>
Sent: Fri, 27 Aug 2010 11:19:52 -0400 (EDT)
Subject: Re: [sdiy] faulty switch causing bounce?

Even the best switches will eventually bounce.  It's a real shame when expensive switches bounce in their infancy.  The RC filter (a great inexpensive solution) will prolong a bouncy switch's useful life but will eventually cease to provide the filtering needed by a constantly degrading switch.  You can buy switch debouncing ICs (at least you could 7 years ago when I looked).  I never used one.  Software debouncers can be very flexible and quite useful but it's quite an expensive solution if debouncing is the only thing your embedded MCU is needed for.

The best debouncer I've ever used is a SPDT switch and an SR latch (flip-flop?).  That's what I would use for important heavy-use switches like a sequencer manual step switch.

Unfortunately, whatever method you choose, the switch will eventually need to be replaced.  Debouncers just keep them in service longer.

John Speth
mailto:john.speth at coherent.com

> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
> bounces at dropmix.xs4all.nl] On Behalf Of mark verbos
> Sent: Thursday, August 26, 2010 7:36 PM
> To: Synth DIY
> Subject: Re: [sdiy] faulty switch causing bounce?
>
> I replaced the switch and it works as expected. That is a pretty
> expensive switch to be still born. Jeez.
>
> Mark
>
>
>
> On Aug 26, 2010, at 10:29 PM, mark verbos wrote:
>
> > Is it possible for a bad switch to cause bounce? I have a C&K
> 7105 (on) off (on)  set up as an advance switch on a sequencer. If
> I push it one was it works fine, but the other way makes the
> sequencer count 2 steps. I have a 2.2M resistor to ground and a
> .05 uF cap to the positive rail. This setup has worked fine for me
> many times before. I'm confused, how can it be only when the
> switch goes one way?
> >
> > Mark
> >
> >
> > _______________________________________________
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> > Synth-diy at dropmix.xs4all.nl
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>
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-- 
Harry Bissell & Nora Abdullah 4eva