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?
One-shot triggered rising and falling?
Started by ●June 29, 2015
Reply by ●July 4, 20152015-07-04
Reply by ●July 15, 20152015-07-15
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>
Reply by ●July 15, 20152015-07-15
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>
Reply by ●July 15, 20152015-07-15
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>
Reply by ●July 15, 20152015-07-15
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>
