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>
One-shot triggered rising and falling?
Started by ●June 29, 2015
Reply by ●June 29, 20152015-06-29
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.
Reply by ●June 29, 20152015-06-29
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
Reply by ●June 30, 20152015-06-30
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.
Reply by ●June 30, 20152015-06-30
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!
Reply by ●June 30, 20152015-06-30
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 | | | Voice:(480)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.
Reply by ●June 30, 20152015-06-30
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
Reply by ●June 30, 20152015-06-30
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
Reply by ●June 30, 20152015-06-30
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
Reply by ●July 1, 20152015-07-01
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!
