One-shot triggered rising and falling?

[Douglas Beeson]

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

--
Douglas Beeson <c.difficile@gmail.com>

 

[jfeng@my-deja.com]

I would use a quad XOR to build an edge detector: wire three of the XORs as non-inverting buffers and put them in series, connect the output of this series string to one of the inputs of the fourth XOR, and wire the other input of the fourth XOR to the input of the first of the three series XORs. This will produce a narrow pulse on both polarity edges of the input. The width of the pulse will be the propagation delay in the series string (when I did it a long time ago with standard TTL, the spec sheet gave the delay as 10ns/gate, but when I measured it, it was closer to 3-4 ns). If these pulses are too narrow, you and increase the propagation delay by putting some small capacitors to ground at the interior nodes of the series string.

 

[M Philbrook]

In article <20150629195657.82bc45f35fb6fb813683805a@gmail.com>,
c.difficile@gmail.com says...

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

If you take advantage of progation time with inverters you can
create a inverted pulse of the original but with a enough gap
between, to possibly retrigger the one shot circuit on the down side.

you combine two open collector type inverter outputs, one of them being
past down lets say 3 inverters and the original using only one inverter.

As long as the one shot responds to that you're all set.

Jamie

 

[John Fields]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

---
You could use either a 74HC123 or a CD4538.

Make one of the one-shots in the package negative triggered, one
positive triggered, and then combine the outputs as required.

 

[Bob Masta]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

jfeng has suggested feeding the two inputs of an XOR (such
as CD4070) with the direct signal on one, and a delayed
signal on the other. You can get that delay from
propagation delay of multiple gates, as he suggests.

An alternative (which I first saw in the "CMOS Cookbook" by
Don Lancaster) is to use a simple RC delay and a single XOR
gate. You connect the signal directly to one gate input,
and through an R to the other (with the C going to ground).

This gives you some adjustment flexibility for noise
rejection, etc, if you don't mind adding the discrete RC
parts. You also may find other uses for the remaining 3
XORs in your CD4070 (or whatever).

Best regards,


Bob Masta

DAQARTA v8.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!

 

[Jim Thompson]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

From ~1980....

<http://www.analog-innovations.com/SED/EqualRiseFallEdgeDelay.pdf>

May need some adaptation to fit your needs.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| 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.

 

[John Larkin]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

You can do the XOR trick that others have suggested, but you could
also use a dual one-shot.

This is a tach circuit that uses both edges.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/DoubleTach.jpg



--

John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Fields]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

---
1. What output pulse width would you like?

2. Do you want the same output width for both high and low going
input edges?

3. would you like the one-shot to be retriggerable on one or both
edges, or would you like it to be non-retriggerable?

John Fields

 

[John Fields]

On Tue, 30 Jun 2015 08:36:44 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

You can do the XOR trick that others have suggested, but you could
also use a dual one-shot.

This is a tach circuit that uses both edges.

https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/DoubleTach.jpg

 

[jfeng@my-deja.com]

On Tuesday, June 30, 2015 at 6:41:09 AM UTC-7, Jim Thompson wrote:

From ~1980....

http://www.analog-innovations.com/SED/EqualRiseFallEdgeDelay.pdf
I think the request was for a simple circuit.

May need some adaptation to fit your needs.

No kidding!

 

[John Larkin]

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
<c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

I suppose there are a lot of Beesons, but do you know of a physics
professor at LSUNO, ca 1965?

 

[Douglas Beeson]

On Sat, 04 Jul 2015 15:25:14 -0700
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

I suppose there are a lot of Beesons, but do you know of a physics
professor at LSUNO, ca 1965?

No, not in my close family line. Legend has it there were "northern Beesons" who went to Ohio after the Revolutionary War and "southern Beesons" who went to Alabama and elsewhere. All the well-known Beesons (except for Chalkley Beeson, my great-great uncle - Google him) came from the southern line.

--
Douglas Beeson <c.difficile@gmail.com>

 

[Douglas Beeson]

On Tue, 30 Jun 2015 13:03:00 -0500
John Fields <jfields@austininstruments.com> wrote:

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

---

Hi John,

Sorry about the long delay answering. Went to Europe for two weeks with practically no access to internet.

> 1. What output pulse width would you like?

No narrower than about 6 ns. I am using it to clock a SN74LVC1G175 flip-flop (your idea, actually, some time ago..). 20-100 ns would be ideal.

2. Do you want the same output width for both high and low going
input edges?

Yes.

3. would you like the one-shot to be retriggerable on one or both
edges, or would you like it to be non-retriggerable?

No, it should be non-retriggerable.


I have seen the suggestion for an XOR with an RC delay circuit. I think that might work just fine here. Thoughts?

John Fields

--
Douglas Beeson <c.difficile@gmail.com>

 

[Douglas Beeson]

Thank you all for your suggestions. I like the XOR approach, especially the single gate with an RC delay. My timing requirements are not super tight. The output needs to clock a flip-flop that can handle up to 175 MHz - so around 6 ns pulse width minimum. My application will work just fine with 100 ns -- or even wider -- pulse widths, so I am thinking a 1k resistor and a 1 nF cap as RC.


On Mon, 29 Jun 2015 19:56:57 -0400
Douglas Beeson <c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

--
Douglas Beeson <c.difficile@gmail.com

--
Douglas Beeson <c.difficile@gmail.com>

 

[Douglas Beeson]

On Tue, 30 Jun 2015 12:41:26 GMT
N0Spam@daqarta.com (Bob Masta) wrote:

On Mon, 29 Jun 2015 19:56:57 -0400, Douglas Beeson
c.difficile@gmail.com> wrote:

Hi all,

I'm sure someone has an quick answer for this. I'd like a simple circuit or a part that produces a pulse -- basically a one-shot -- with both a rising edge and falling edge input signal. All the multivibrator ICs I have seen will trigger on rising OR falling, but not on both. How can I get a trigger on both?

Thank you!

jfeng has suggested feeding the two inputs of an XOR (such
as CD4070) with the direct signal on one, and a delayed
signal on the other. You can get that delay from
propagation delay of multiple gates, as he suggests.

An alternative (which I first saw in the "CMOS Cookbook" by
Don Lancaster) is to use a simple RC delay and a single XOR
gate. You connect the signal directly to one gate input,
and through an R to the other (with the C going to ground).

This gives you some adjustment flexibility for noise
rejection, etc, if you don't mind adding the discrete RC
parts. You also may find other uses for the remaining 3
XORs in your CD4070 (or whatever).

Thanks for this idea. I have been away from the bench for a while but have tried it out on Spice and a 1k resistor and 1nF cap seems to work just great for me.

Best regards,


Bob Masta

DAQARTA v8.00
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, Pitch Track, Pitch-to-MIDI
FREE 8-channel Signal Generator, DaqMusiq generator
Science with your sound card!

--
Douglas Beeson <c.difficile@gmail.com>