de-bounce

[Henry]

I am tinkering with some 25 year old TTL logic chips and I need to make a
de-bounce circuit that will stay on for the duration of a the push-button. I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close and open
of the push button to be debounced and it to keep the duration of the button
push. I have seen schmitt trigger circuits (that I have tried to build but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked an some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

Henry

 

[Henry]

"Dan Hollands" <dhollan3@rochester.rr.com> wrote in message
news:qGyrf.55110$XC4.23793@twister.nyroc.rr.com...

"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...
I am tinkering with some 25 year old TTL logic chips and I need to make a
de-bounce circuit that will stay on for the duration of a the
push-button.
I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close and
open
of the push button to be debounced and it to keep the duration of the
button
push. I have seen schmitt trigger circuits (that I have tried to build
but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked an
some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

Henry




The easiest way is to use a pushbutton with Form C contact (single pole,
double throw) connected to 2 cross connected NOR gates so that when the
moving contact hits one pole connected to one NOR gate the cross
connection
latches in one state and when the moving contact hits the other pose
connected to the other NOR gate the cross connection latches in the other
state. Thus you get a latch circuit the follows the pushbutton with no
glitches.

If you don't know how to implement this let me I can give you more details

Dan

Thanks, but I have no control over the push button. Its a camera shutter.
Might be mechanical, might be electronic. Either way it acts like a simple
push button closing a circuit. The mechanical ones, of course have noise.

I have an old camera that I want to try some specialy effects photography
with. I also have a view camera that has a focal plane leaf shutter (built
into the lens) that, in theory, should sync with a flash through its range
of shutter speeds (up to 1/250 of a second.)

Anyway, thanks. I will keep looking.

Henry

 

[Henry]

Yes, I have read how difficult of a problem that it is. And what makes it
worse is that I wanted to make it a general circuit good for mony, if not
most, camera shutters whether they be mechanical or digital. One of the
things is that I wanted to make a timer to measure how long a shutter is
open (old mechanical camera shutters can vary (as much as 20%) from the
indicated shutter speed. I have an idea for a solution, but is seems odd.

Henry


"Dan Hollands" <dhollan3@rochester.rr.com> wrote in message
news:IPJrf.55962$XC4.2928@twister.nyroc.rr.com...

Henry

Without some knowledge of the type and electrical charactoristis of the
button it is hard to design a debounce circuit. Even with a mechanical
switch are sure that need one - what is the button going to do

--
Dan Hollands
1120 S Creek Dr
Webster NY 14580
585-872-2606
dhollan3@rochester.rr.com
www.QuickScoreRace.com
"Henry" <henrytj@pghmail.com> wrote in message
news:A5qdnYzHhKLWzzLeRVn-ig@pghconnect.com...

"Dan Hollands" <dhollan3@rochester.rr.com> wrote in message
news:qGyrf.55110$XC4.23793@twister.nyroc.rr.com...
"Henry" <henrytj@pghmail.com> wrote in message
news:5cadnTvrJqLH5zPenZ2dnUVZ_vidnZ2d@pghconnect.com...
I am tinkering with some 25 year old TTL logic chips and I need to
make
a
de-bounce circuit that will stay on for the duration of a the
push-button.
I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close
and
open
of the push button to be debounced and it to keep the duration of the
button
push. I have seen schmitt trigger circuits (that I have tried to
build
but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio
Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked
an
some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

Henry




The easiest way is to use a pushbutton with Form C contact (single
pole,
double throw) connected to 2 cross connected NOR gates so that when the
moving contact hits one pole connected to one NOR gate the cross
connection
latches in one state and when the moving contact hits the other pose
connected to the other NOR gate the cross connection latches in the
other
state. Thus you get a latch circuit the follows the pushbutton with no
glitches.

If you don't know how to implement this let me I can give you more
details

Dan


Thanks, but I have no control over the push button. Its a camera
shutter.
Might be mechanical, might be electronic. Either way it acts like a
simple
push button closing a circuit. The mechanical ones, of course have
noise.

I have an old camera that I want to try some specialy effects
photography
with. I also have a view camera that has a focal plane leaf shutter
(built
into the lens) that, in theory, should sync with a flash through its
range
of shutter speeds (up to 1/250 of a second.)

Anyway, thanks. I will keep looking.

Henry

 

[Jasen Betts]

On 2005-12-25, Henry <henrytj@pghmail.com> wrote:

I am tinkering with some 25 year old TTL logic chips and I need to make a
de-bounce circuit that will stay on for the duration of a the push-button. I
have several ways already to debounce the button close, but they are
one-shot pulses that have thein own duration. I need both the close and open
of the push button to be debounced and it to keep the duration of the button
push. I have seen schmitt trigger circuits (that I have tried to build but
dont seem to work (have to triple check the wiring)), and other RC
variations. What kind of easily accessible parts (like from Radio Shack)
should I be looking for. It all has to run on 4-AA batteries. Looked an some
op-amp parts at RS but they seem to all require 18v, or more, supply.

BTW, the debouncing solution needs to be acurate to within about 1
milli-second.

something like this might do the trick

+------------------+--+5
| |
[10K] [10K]
| |
\ +-----+ +---+---- out
in /\ | | | |
-------[1K]---+---[100K]---(---+ | | /
| / | | | r2 | |/
| \ | +-[100K]-)-|
__L__ \| | | |\|
~~T~~ |-+---[330k]-+ -\
| 0.1uF |/| R1 |
| /- |
| | |
-------------+------------+------------------+-------

the input may need a pull up, the output should be capable of driving TTL.
small capacitors in parallel with the base resistors may help with the
waveform a bit.

increasing the timing capacitor to 1uF may help if you're still seeing
bounce with this,

Bye.
Jasen

 

[Henry]

Henry, please bottom post, since it makes it much easier to follow
the chronological flow of the thread. Thanks.

Thanks, I will try to keep that is mind. Im on several different forums
(photography, sci-fi, etc.) and different ones have different preferences,
if any. Ussually I follow with what the last person used, or I try to.

Thanks everyone for all the help and suggestions. I will be giving several
suggested circuits a try soon. Assuming that I can build them correctly, and
have the parts.

Henry

 

[deadcarnahans]

Forget RS.
Order Mousers catalog. www.mouser.com (800) 346-6873