simple oneshot

[George Herold]

Hi all, OK a silly basic question.
I'm doing some digital stuff.
I wanted a one shot to reset some things, but didn't want to put in an entire chip
(74HC123.. or whatever the number is.)
So I just used a cap, resistor, diode and inverter.
https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG
Is this OK?

Thanks,
George H.

 

[George Herold]

On Wednesday, April 16, 2014 12:56:49 PM UTC-4, Phil Hobbs wrote:
> On 04/16/2014 11:11 AM, George Herold wrote:
(weird I can see your reply but not my original post..
google groups is broken again... (yeah I know.))

The output rise time will be slow, due to the limited gain of the gate.
Using a 74HC14 Schmitt inverter will help.
Check that's what I've got.


It loads down its input very badly on falling edges, and the pulse width
Good point. I'll add another resistor in series with the cap. (say 1k in series an 10k to ground.) That will take care of my worries about the diode current too.
will be uncertain by about a factor of 2 due to the threshold voltage
tolerance of the inverter.
Yeah no problem there... I've got plenty of time.


But for some jobs, a little M-squared-L is just the ticket.

M-squared-L? what's that? A transformer?
(googling brings up Mellissa's instagram site... I don't think that was your reference. :^)

George H.


Cheers



Phil Hobbs



--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC

Optics, Electro-optics, Photonics, Analog Electronics



160 North State Road #203

Briarcliff Manor NY 10510



hobbs at electrooptical dot net

http://electrooptical.net

 

[Phil Hobbs]

On 04/16/2014 11:11 AM, George Herold wrote:

Hi all, OK a silly basic question.
I'm doing some digital stuff.
I wanted a one shot to reset some things, but didn't want to put in an entire chip
(74HC123.. or whatever the number is.)
So I just used a cap, resistor, diode and inverter.
https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG
Is this OK?

Thanks,
George H.

The output rise time will be slow, due to the limited gain of the gate.
Using a 74HC14 Schmitt inverter will help.

It loads down its input very badly on falling edges, and the pulse width
will be uncertain by about a factor of 2 due to the threshold voltage
tolerance of the inverter.

But for some jobs, a little M-squared-L is just the ticket.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Jim Thompson]

On Wed, 16 Apr 2014 08:11:11 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

Hi all, OK a silly basic question.
I'm doing some digital stuff.
I wanted a one shot to reset some things, but didn't want to put in an entire chip
(74HC123.. or whatever the number is.)
So I just used a cap, resistor, diode and inverter.
https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG
Is this OK?

Thanks,
George H.

<http://www.analog-innovations.com/SED/GeorgeHeroldOneShot_2014_04_16.png>

Leave D5 out if you don't mind symmetrical delay.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Phil Hobbs]

On 04/16/2014 01:52 PM, George Herold wrote:

On Wednesday, April 16, 2014 12:56:49 PM UTC-4, Phil Hobbs wrote:
On 04/16/2014 11:11 AM, George Herold wrote:
(weird I can see your reply but not my original post..
google groups is broken again... (yeah I know.))

The output rise time will be slow, due to the limited gain of the gate.
Using a 74HC14 Schmitt inverter will help.
Check that's what I've got.


It loads down its input very badly on falling edges, and the pulse width
Good point. I'll add another resistor in series with the cap. (say 1k in series an 10k to ground.) That will take care of my worries about the diode current too.
will be uncertain by about a factor of 2 due to the threshold voltage
tolerance of the inverter.
Yeah no problem there... I've got plenty of time.


But for some jobs, a little M-squared-L is just the ticket.

M-squared-L? what's that? A transformer?
(googling brings up Mellissa's instagram site... I don't think that was your reference. :^)

George H.

Mickey Mouse Logic. (hat tip to Don Lancaster)

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Maynard A. Philbrook Jr.]

In article <12536e91-630e-49ee-a04f-2b3b35b06974@googlegroups.com>,
gherold@teachspin.com says...

Hi all, OK a silly basic question.
I'm doing some digital stuff.
I wanted a one shot to reset some things, but didn't want to put in an entire chip
(74HC123.. or whatever the number is.)
So I just used a cap, resistor, diode and inverter.
https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG
Is this OK?

Thanks,
George H.

If you have two inverters you can put two in series and have a little
hysteresis back to the first inverter via a R network to give you a nice
fast snap.

Of course, if you had a Schmitt inverter that would do the same for you
, too. I am sure the common ones are more than quick enough.

Or you can combine a PNP and NPN in a thyristor configuration which
will not hold latch but will snap very quickly and give you hysteresis.

Or, you could employ a 555 and just do a one shot there. But in that
case, you could simply open the digikey or mouser book and get a power
management chip.

Jamie

 

[George Herold]

On Wednesday, April 16, 2014 2:27:59 PM UTC-4, Jim Thompson wrote:

On Wed, 16 Apr 2014 08:11:11 -0700 (PDT), George Herold

https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG


http://www.analog-innovations.com/SED/GeorgeHeroldOneShot_2014_04_16.png


Leave D5 out if you don't mind symmetrical delay.

Thanks Jim... I'll have to look at that a bit more.
Is this going to give me a delay or a one shot at the edge?
(At the moment I just want a one shot...)

George H.

...Jim Thompson

--

| James E.Thompson | mens |

| Analog Innovations | et |

| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |

| San Tan Valley, AZ 85142 Skype: Contacts Only | |

| Voice480)460-2350 Fax: Available upon request | Brass Rat |

| E-mail Icon at http://www.analog-innovations.com | 1962 |



I love to cook with wine. Sometimes I even put it in the food.

 

[George Herold]

On Wednesday, April 16, 2014 5:36:44 PM UTC-4, Maynard A. Philbrook Jr. wrote:

In article <12536e91-630e-49ee-a04f-2b3b35b06974@googlegroups.com>,

gherold@teachspin.com says...



Hi all, OK a silly basic question.

I'm doing some digital stuff.

I wanted a one shot to reset some things, but didn't want to put in an entire chip

(74HC123.. or whatever the number is.)

So I just used a cap, resistor, diode and inverter.

https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG

Is this OK?



Thanks,

George H.



If you have two inverters you can put two in series and have a little

hysteresis back to the first inverter via a R network to give you a nice

fast snap.



Of course, if you had a Schmitt inverter that would do the same for you

, too. I am sure the common ones are more than quick enough.



Or you can combine a PNP and NPN in a thyristor configuration which

will not hold latch but will snap very quickly and give you hysteresis.



Or, you could employ a 555 and just do a one shot there. But in that

case, you could simply open the digikey or mouser book and get a power

management chip.



Jamie

Thanks Jamie, What i've got looks very simple. Two R's, a C and Diode.

George H.

 

[George Herold]

On Wednesday, April 16, 2014 4:24:27 PM UTC-4, Phil Hobbs wrote:

Mickey Mouse Logic. (hat tip to Don Lancaster)

Got it. (That doesn't sound very good at the design review though.)

Does Don do stuff like this in his CMOS cookbook.
(I've never read any of Don's books. I thought it would be obsolete,
but it looks to still be selling well on amazon.

George h.

Cheers



Phil Hobbs





--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC

Optics, Electro-optics, Photonics, Analog Electronics



160 North State Road #203

Briarcliff Manor NY 10510



hobbs at electrooptical dot net

http://electrooptical.net

 

[Jim Thompson]

On Thu, 17 Apr 2014 10:32:26 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Wednesday, April 16, 2014 2:27:59 PM UTC-4, Jim Thompson wrote:
On Wed, 16 Apr 2014 08:11:11 -0700 (PDT), George Herold

https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG


http://www.analog-innovations.com/SED/GeorgeHeroldOneShot_2014_04_16.png


Leave D5 out if you don't mind symmetrical delay.
Thanks Jim... I'll have to look at that a bit more.
Is this going to give me a delay or a one shot at the edge?
(At the moment I just want a one shot...)

George H.


[snip]

It's a delay block, but should serve your purpose as a delayed reset.

I use that architecture in a lot of my chip designs because, without
ESD, it's a pretty stable delay, independent of VDD, pretty much just
the RC time constant for delays much longer than the inherent inverter
delay.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Phil Hobbs]

On 04/17/2014 01:42 PM, George Herold wrote:

On Wednesday, April 16, 2014 4:24:27 PM UTC-4, Phil Hobbs wrote:


Mickey Mouse Logic. (hat tip to Don Lancaster)


Got it. (That doesn't sound very good at the design review though.)

Does Don do stuff like this in his CMOS cookbook.
(I've never read any of Don's books. I thought it would be obsolete,
but it looks to still be selling well on amazon.

George h.

I think it might be the TTL book, but it's certainly one of the two.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[George Herold]

On Friday, April 18, 2014 8:27:16 AM UTC-4, Bob Masta wrote:

On Thu, 17 Apr 2014 14:52:39 -0400, Phil Hobbs

pcdhSpamMeSenseless@electrooptical.net> wrote:



On 04/17/2014 01:42 PM, George Herold wrote:

On Wednesday, April 16, 2014 4:24:27 PM UTC-4, Phil Hobbs wrote:





Mickey Mouse Logic. (hat tip to Don Lancaster)

Got it. (That doesn't sound very good at the design review though.)



Does Don do stuff like this in his CMOS cookbook.


I think it might be the TTL book, but it's certainly one of the two.


Dunno about the TTL book, but in the "CMOS Cookbook" it's on
pages 186-189. Great book! A few specific topics might be
outdated, but the sections on one-shots and oscillators are
particularly handy.

Got it, thanks Bob. (Figure 4-36 in the second volume.. found on amazon.)
Hey I hadn't thought about tying the R and diode to the positive rail.
George H.
ps anything found in the cmos cookbook must be kosher. :^)

Best regards,

Bob Masta



DAQARTA v7.50

Data AcQuisition And Real-Time Analysis

www.daqarta.com

Scope, Spectrum, Spectrogram, Sound Level Meter

Frequency Counter, Pitch Track, Pitch-to-MIDI

FREE Signal Generator, DaqMusiq generator

Science with your sound card!

 

[Bob Masta]

On Thu, 17 Apr 2014 14:52:39 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 04/17/2014 01:42 PM, George Herold wrote:
On Wednesday, April 16, 2014 4:24:27 PM UTC-4, Phil Hobbs wrote:


Mickey Mouse Logic. (hat tip to Don Lancaster)


Got it. (That doesn't sound very good at the design review though.)

Does Don do stuff like this in his CMOS cookbook.
(I've never read any of Don's books. I thought it would be obsolete,
but it looks to still be selling well on amazon.

George h.

I think it might be the TTL book, but it's certainly one of the two.

Dunno about the TTL book, but in the "CMOS Cookbook" it's on
pages 186-189. Great book! A few specific topics might be
outdated, but the sections on one-shots and oscillators are
particularly handy.

Best regards,


Bob Masta

DAQARTA v7.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!

 

[Wayne Chirnside]

On Thu, 17 Apr 2014 10:34:11 -0700, George Herold wrote:

On Wednesday, April 16, 2014 5:36:44 PM UTC-4, Maynard A. Philbrook Jr.
wrote:
In article <12536e91-630e-49ee-a04f-2b3b35b06974@googlegroups.com>,

gherold@teachspin.com says...



Hi all, OK a silly basic question.

I'm doing some digital stuff.

I wanted a one shot to reset some things, but didn't want to put in
an entire chip

(74HC123.. or whatever the number is.)

So I just used a cap, resistor, diode and inverter.

https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG

Is this OK?



Thanks,

George H.



If you have two inverters you can put two in series and have a little

hysteresis back to the first inverter via a R network to give you a
nice

fast snap.



Of course, if you had a Schmitt inverter that would do the same for
you

, too. I am sure the common ones are more than quick enough.



Or you can combine a PNP and NPN in a thyristor configuration which

will not hold latch but will snap very quickly and give you hysteresis.



Or, you could employ a 555 and just do a one shot there. But in that

case, you could simply open the digikey or mouser book and get a power

management chip.



Jamie

Thanks Jamie, What i've got looks very simple. Two R's, a C and Diode.

George H.

My solution is a cmos 4093 quad two input schmitt trigger.
resistor, cap and one gate

 

[John Larkin]

On Wed, 16 Apr 2014 17:36:44 -0400, "Maynard A. Philbrook Jr."
<jamie_ka1lpa@charter.net> wrote:

In article <12536e91-630e-49ee-a04f-2b3b35b06974@googlegroups.com>,
gherold@teachspin.com says...

Hi all, OK a silly basic question.
I'm doing some digital stuff.
I wanted a one shot to reset some things, but didn't want to put in an entire chip
(74HC123.. or whatever the number is.)
So I just used a cap, resistor, diode and inverter.
https://www.dropbox.com/s/flnonc9rgwmerhw/DSCF0082.JPG
Is this OK?

Thanks,
George H.

If you have two inverters you can put two in series and have a little
hysteresis back to the first inverter via a R network to give you a nice
fast snap.

Of course, if you had a Schmitt inverter that would do the same for you
, too. I am sure the common ones are more than quick enough.

Or you can combine a PNP and NPN in a thyristor configuration which
will not hold latch but will snap very quickly and give you hysteresis.

Or, you could employ a 555 and just do a one shot there. But in that
case, you could simply open the digikey or mouser book and get a power
management chip.

Jamie

Another home-made one-shot is a d-flop that resets itself. That's edge
sensitive.

If you connect q-bar to reset with a delay line of some sort, it works fine. An
RC is trickier. Original 74xx TTL would usually hang if it tried to reset itself
with an RC. Later logic, with more gain, would usually reset clean.

This works well with fast logic, like EclipsLite. Just a bit of trace makes a
good delay line, like for a 1 ns one-shot.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Bob Masta]

On Fri, 18 Apr 2014 06:25:35 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Friday, April 18, 2014 8:27:16 AM UTC-4, Bob Masta wrote:
On Thu, 17 Apr 2014 14:52:39 -0400, Phil Hobbs

pcdhSpamMeSenseless@electrooptical.net> wrote:



On 04/17/2014 01:42 PM, George Herold wrote:

On Wednesday, April 16, 2014 4:24:27 PM UTC-4, Phil Hobbs wrote:





Mickey Mouse Logic. (hat tip to Don Lancaster)

Got it. (That doesn't sound very good at the design review though.)



Does Don do stuff like this in his CMOS cookbook.


I think it might be the TTL book, but it's certainly one of the two.


Dunno about the TTL book, but in the "CMOS Cookbook" it's on
pages 186-189. Great book! A few specific topics might be
outdated, but the sections on one-shots and oscillators are
particularly handy.

Got it, thanks Bob. (Figure 4-36 in the second volume.. found on amazon.)
Hey I hadn't thought about tying the R and diode to the positive rail.
George H.
ps anything found in the cmos cookbook must be kosher. :^)

Funny story: Back when this first came out (1977ish) and I
was thinking of buying it, my mother asked me what she could
get me for Christmas... always a problem for her. So I
figured I could hold off on buying it myself, and I told her
"the CMOS Cookbook by Don Lancaster".

Christmas came and she gave me something else, saying "I
searched the cookbook sections of 3 different bookstores,
even asked at the desk, but nobody had heard of the "Sea
Moss Cookbook"!

Best regards,


Bob Masta

DAQARTA v7.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE Signal Generator, DaqMusiq generator
Science with your sound card!