Simplest, cleanest, push button debouncer?

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Is there any consensus on the neatest circuit to take a noisy push
button signal and output a clean rectangular pulse?

Searching through my ancient (paper) files I found dozens, but my
scribbled notes on many show that when tested I'd found lots failed,
allowing some noise to reach the output. My starting assumption is a
simple CR filter in front of a Schmitt. But before I head for the shed
and start bread boarding I'd much appreciate any recommendations please.

Terry, East Grinstead, UK

Re: Simplest, cleanest, push button debouncer?
On 2018-09-12 18:54, Terry Pinnell wrote:
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The good old 555 timer works nicely in this application. It has a very
wide hysteresis (from 2/3 of Vcc to 1/3 of Vcc) that makes the circuit
immune to noise and unwanted re-triggers. There is a push-pull logic
output available as well as the open-collector "discharge" one, and
everything apart from the 3 timing-related passives is integrated. For
CMOS logic compatibility from 1.5 V supply and up, there's the LMC555.


Re: Simplest, cleanest, push button debouncer?

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Thanks Dimitrij, that looks like my favourite.

(Sorry for delay; this post was my first reply, but I didn't spot it had
somehow got stuck in the outbox.)

Terry, East Grinstead, UK

Re: Simplest, cleanest, push button debouncer?
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If  a microcontroller is involved do it it in software  

If the button is dual throw wire NO/NC across the logic supply and put a
small capacitor on the output (C)

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yeah, thats the third option.

--  
     ?

Re: Simplest, cleanest, push button debouncer?

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Thanks Jasen. No micros here. And just plain single pole buttons.

Terry, East Grinstead, UK

Re: Simplest, cleanest, push button debouncer?
On Wednesday, September 12, 2018 at 12:54:50 PM UTC-4, Terry Pinnell wrote:
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If you can do a double throw switch then there is a config that uses  
an SR flip flop. (And others.. see AoE3.)  
  With a single pole I think you are stuck with a long  
time delay... (Some RC thing ~10's of milli seconds.)  

George H.  

Re: Simplest, cleanest, push button debouncer?
On Thursday, September 13, 2018 at 5:56:39 AM UTC-7, George Herold wrote:
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Yep, that's a good 'un.   There's also Hall switches (or used to be) from
Cherry, in keyboard-mountable form, that give good clean output
and don't fail from dirty contacts.   I'm not seeing any inexpensive such
items nowadays, but have a box of the old ones somewhere.

Re: Simplest, cleanest, push button debouncer?

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Thanks. Mine is version 2 but I'll check it out.
  
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Terry, East Grinstead, UK

Re: Simplest, cleanest, push button debouncer?
On 9/12/2018 11:54 AM, Terry Pinnell wrote:
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  Here's one I came up I came up with that worked in a very noisy  
product we had. I've posted it many times never got any response, good  
or bad.
It uses an SCR.
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                            Mikek


Re: Simplest, cleanest, push button debouncer?
On 9/13/2018 2:25 PM, amdx wrote:
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  I guess I didn't read enough, it outputs a pulldown pulse.

Re: Simplest, cleanest, push button debouncer?

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Still an interesting circuit that I mean to try, thanks.

Re: Simplest, cleanest, push button debouncer?
On 9/13/18 3:25 PM, amdx wrote:
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7 parts is a lot for a debouncer.  An RC lowpass and a tinylogic Schmitt  
will work fine.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Simplest, cleanest, push button debouncer?

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True, but it always feels wasteful using only half a 14-pin IC, like a
4013 for example. And time-consuming terminating the unused inputs.

But my interest in the SCR circuit is mainly because I have a bunch of
ancient, low-power SCRs, maybe 40-50 years old.

Terry, East Grinstead, UK

Re: Simplest, cleanest, push button debouncer?
On 9/15/18 6:59 AM, Terry Pinnell wrote:
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Tiny logic is one gate per package.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
We've slightly trimmed the long signature. Click to see the full one.
Re: Simplest, cleanest, push button debouncer?
On Wed, 12 Sep 2018 17:54:46 +0100, Terry Pinnell wrote:

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Yup, that's probably the simplest and cheapest effective way.
But if you need more buttons to be debounced, a uC solution might
be more scalable and simpler so that the filter could be
implemented in software virtually using no components other
than the minumum necessary to have the uC run.

Re: Simplest, cleanest, push button debouncer?

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Look at the MC14490.  Works great.  



Re: Simplest, cleanest, push button debouncer?
On Fri, 14 Sep 2018 05:25:58 -0500, Rick wrote:

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Never heard of that chip, looks interesting. Thanks.

Re: Simplest, cleanest, push button debouncer?
On 9/14/18 6:25 AM, Rick wrote:
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Four bucks in reels!  Six 1-cent caps, six 0.3-cent resistors, one  
8-cent 74HC14.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Simplest, cleanest, push button debouncer?
wrote:

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A uP doesn't need hardware or software debouncing. Just sample the
switch state 10 times per second and use what you see.

It could use emi/esd protection, but that's just one capacitor.




--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Simplest, cleanest, push button debouncer?

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Thanks, but no micro hardware or software skills here.

Terry, East Grinstead, UK

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