Reply by Terry Pinnell●September 17, 20182018-09-17
Dimitrij Klingbeil <nospam@no-address.com> wrote:
>On 2018-09-12 18:54, Terry Pinnell wrote:
>> 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
>
>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.
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
Reply by Phil Hobbs●September 15, 20182018-09-15
On 9/15/18 6:59 AM, Terry Pinnell wrote:
> Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 9/13/18 3:25 PM, amdx wrote:
>>> On 9/12/2018 11:54 AM, Terry Pinnell wrote:
>>>> 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
>>>>
>>>
>>> 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.
>>>> http://photobucket.com/gallery/http://s395.photobucket.com/user/Qmavam/media/Debouncejpg.jpg.html
>>>>
>>
>> 7 parts is a lot for a debouncer. An RC lowpass and a tinylogic Schmitt
>> will work fine.
>>
>> Cheers
>>
>> Phil Hobbs
>
> 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
>
Tiny logic is one gate per package.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by Terry Pinnell●September 15, 20182018-09-15
asdf <asdf@nospam.com> wrote:
>On Wed, 12 Sep 2018 17:54:46 +0100, Terry Pinnell wrote:
>
>> My starting assumption is a simple CR filter in front of a Schmitt.
>
>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.
Thanks, but no micro hardware or software skills here.
Terry, East Grinstead, UK
Reply by Terry Pinnell●September 15, 20182018-09-15
George Herold <gherold@teachspin.com> wrote:
>On Wednesday, September 12, 2018 at 12:54:50 PM UTC-4, Terry Pinnell wrote:
>> 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
>
>If you can do a double throw switch then there is a config that uses
>an SR flip flop. (And others.. see AoE3.)
Thanks. Mine is version 2 but I'll check it out.
> With a single pole I think you are stuck with a long
>time delay... (Some RC thing ~10's of milli seconds.)
>
>George H.
Terry, East Grinstead, UK
Reply by Terry Pinnell●September 15, 20182018-09-15
Jasen Betts <jasen@xnet.co.nz> wrote:
>On 2018-09-12, Terry Pinnell <me@somewhere.invalid> wrote:
>> Is there any consensus on the neatest circuit to take a noisy push
>> button signal and output a clean rectangular pulse?
>
>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)
>
>> My starting assumption is a simple CR filter in front of a Schmitt
>
>yeah, thats the third option.
Thanks Jasen. No micros here. And just plain single pole buttons.
Terry, East Grinstead, UK
Reply by Terry Pinnell●September 15, 20182018-09-15
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
>On 9/13/18 3:25 PM, amdx wrote:
>> On 9/12/2018 11:54 AM, Terry Pinnell wrote:
>>> 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
>>>
>>
>> �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.
>>> http://photobucket.com/gallery/http://s395.photobucket.com/user/Qmavam/media/Debouncejpg.jpg.html
>>>
>
>7 parts is a lot for a debouncer. An RC lowpass and a tinylogic Schmitt
>will work fine.
>
>Cheers
>
>Phil Hobbs
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
Reply by Terry Pinnell●September 15, 20182018-09-15
amdx <nojunk@knology.net> wrote:
>On 9/13/2018 2:25 PM, amdx wrote:
>> On 9/12/2018 11:54 AM, Terry Pinnell wrote:
>>> 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
>>>
>>
>> �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.
>>> http://photobucket.com/gallery/http://s395.photobucket.com/user/Qmavam/media/Debouncejpg.jpg.html
>>>
>>
>> �������������������������� Mikek
>>
> I guess I didn't read enough, it outputs a pulldown pulse.
Still an interesting circuit that I mean to try, thanks.
Reply by Phil Hobbs●September 14, 20182018-09-14
On 9/14/18 6:25 AM, Rick wrote:
>
> "asdf" <asdf@nospam.com> wrote in message
> news:pnem1h$1184$1@gioia.aioe.org...
>> On Wed, 12 Sep 2018 17:54:46 +0100, Terry Pinnell wrote:
>>
>>> My starting assumption is a simple CR filter in front of a Schmitt.
>>
>> 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.
>
> Look at the MC14490. Works great.
>
>
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
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by Phil Hobbs●September 14, 20182018-09-14
On 9/13/18 3:25 PM, amdx wrote:
> On 9/12/2018 11:54 AM, Terry Pinnell wrote:
>> 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
>>
>
> 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.
>> http://photobucket.com/gallery/http://s395.photobucket.com/user/Qmavam/media/Debouncejpg.jpg.html
>>
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
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.nethttp://hobbs-eo.com
Reply by whit3rd●September 14, 20182018-09-14
On Thursday, September 13, 2018 at 5:56:39 AM UTC-7, George Herold wrote:
> On Wednesday, September 12, 2018 at 12:54:50 PM UTC-4, Terry Pinnell wrote:
> > Is there any consensus on the neatest circuit to take a noisy push
> > button signal and output a clean rectangular pulse?
> If you can do a double throw switch then there is a config that uses
> an SR flip flop. (And others.. see AoE3.)
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.