On 6/20/2015 1:19 PM, Jim Thompson wrote:> On Sat, 20 Jun 2015 12:52:26 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 6/20/2015 11:42 AM, Jim Thompson wrote: >>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>> duration, and stretch it out long enough to flash a LED brightly enough >>>> to be visible indoors under "ordinary" lighting conditions. >>>> >>>> I currently only have op-amps on the board and would rather not add any >>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>> fine. The pulse source into the stretcher would be low impedance. >>>> >>>> An optional feature would be to have the "stretch" duration decrease the >>>> more rapidly pulses are coming into the circuit. But that is not a >>>> requirement if it needs significant complexity. >>> >>> Supplies? >>> >>> ...Jim Thompson >>> >> >> Looks like it's going to be +5V virtual ground split into +2.5 and -2.5 >> at this point so they'll be low-voltage opamps. > > So your input pulse is -2.5V to +2.5V _relative_ to your virtual > ground? > > ...Jim Thompson >Nosir, it will be 5 volts relative to the overall common, i.e. the -2.5 volt point wrt virtual ground.
super simple pulse stretcher
Started by ●June 20, 2015
Reply by ●June 20, 20152015-06-20
Reply by ●June 20, 20152015-06-20
On Sat, 20 Jun 2015 13:39:40 -0400, bitrex <bitrex@de.lete.earthlink.net> wrote:>On 6/20/2015 1:19 PM, Jim Thompson wrote: >> On Sat, 20 Jun 2015 12:52:26 -0400, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> On 6/20/2015 11:42 AM, Jim Thompson wrote: >>>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>>> <bitrex@de.lete.earthlink.net> wrote: >>>> >>>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>>> duration, and stretch it out long enough to flash a LED brightly enough >>>>> to be visible indoors under "ordinary" lighting conditions. >>>>> >>>>> I currently only have op-amps on the board and would rather not add any >>>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>>> fine. The pulse source into the stretcher would be low impedance. >>>>> >>>>> An optional feature would be to have the "stretch" duration decrease the >>>>> more rapidly pulses are coming into the circuit. But that is not a >>>>> requirement if it needs significant complexity. >>>> >>>> Supplies? >>>> >>>> ...Jim Thompson >>>> >>> >>> Looks like it's going to be +5V virtual ground split into +2.5 and -2.5 >>> at this point so they'll be low-voltage opamps. >> >> So your input pulse is -2.5V to +2.5V _relative_ to your virtual >> ground? >> >> ...Jim Thompson >> > >Nosir, it will be 5 volts relative to the overall common, i.e. the -2.5 >volt point wrt virtual ground.Isn't that what I just said ?:-) ...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 20, 20152015-06-20
On Sat, 20 Jun 2015 12:40:55 -0400, bitrex <bitrex@de.lete.earthlink.net> wrote:>On 6/20/2015 11:11 AM, John Larkin wrote: >> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>> duration, and stretch it out long enough to flash a LED brightly enough >>> to be visible indoors under "ordinary" lighting conditions. >>> >>> I currently only have op-amps on the board and would rather not add any >>> logic ICs to do this. So using low-speed op amps and discretes would be >>> fine. The pulse source into the stretcher would be low impedance. >>> >>> An optional feature would be to have the "stretch" duration decrease the >>> more rapidly pulses are coming into the circuit. But that is not a >>> requirement if it needs significant complexity. >> >> NPN emitter follower driving R-C to ground, then a comparator. Use an >> opamp as the comparator. >> >> > >I'm probably going to need to be using something like an LM324A. Will >they work OK in that role?Sure. If you have two sections available, use one open drain to discharge the capacitor, and the other section as the threshold sensor. Quiescent high, RC pulsed low. Easy. We sometimes have a "trigger" LED that is basically a stretched input. In some cases, we want to catch very short pulses - a couple ns - but also indicate a static high input. Laser drivers want that sort of indication. We use a fast one-shot (SN74LVC1G123) and OR its input into the output. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●June 20, 20152015-06-20
On 6/20/2015 1:19 PM, Jim Thompson wrote:> On Sat, 20 Jun 2015 12:52:26 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 6/20/2015 11:42 AM, Jim Thompson wrote: >>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>> duration, and stretch it out long enough to flash a LED brightly enough >>>> to be visible indoors under "ordinary" lighting conditions. >>>> >>>> I currently only have op-amps on the board and would rather not add any >>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>> fine. The pulse source into the stretcher would be low impedance. >>>> >>>> An optional feature would be to have the "stretch" duration decrease the >>>> more rapidly pulses are coming into the circuit. But that is not a >>>> requirement if it needs significant complexity. >>> >>> Supplies? >>> >>> ...Jim Thompson >>> >> >> Looks like it's going to be +5V virtual ground split into +2.5 and -2.5 >> at this point so they'll be low-voltage opamps. > > So your input pulse is -2.5V to +2.5V _relative_ to your virtual > ground? > > ...Jim Thompson >Correct.
Reply by ●June 20, 20152015-06-20
On 6/20/2015 1:54 PM, John Larkin wrote:> On Sat, 20 Jun 2015 12:40:55 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 6/20/2015 11:11 AM, John Larkin wrote: >>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>> duration, and stretch it out long enough to flash a LED brightly enough >>>> to be visible indoors under "ordinary" lighting conditions. >>>> >>>> I currently only have op-amps on the board and would rather not add any >>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>> fine. The pulse source into the stretcher would be low impedance. >>>> >>>> An optional feature would be to have the "stretch" duration decrease the >>>> more rapidly pulses are coming into the circuit. But that is not a >>>> requirement if it needs significant complexity. >>> >>> NPN emitter follower driving R-C to ground, then a comparator. Use an >>> opamp as the comparator. >>> >>> >> >> I'm probably going to need to be using something like an LM324A. Will >> they work OK in that role? > > Sure. If you have two sections available, use one open drain to > discharge the capacitor, and the other section as the threshold > sensor. Quiescent high, RC pulsed low. Easy. > > We sometimes have a "trigger" LED that is basically a stretched input. > In some cases, we want to catch very short pulses - a couple ns - but > also indicate a static high input. Laser drivers want that sort of > indication. We use a fast one-shot (SN74LVC1G123) and OR its input > into the output. > >I'm not sure I follow what you mean by using one "open drain." If you have a moment could you show me in LTSpice? Also I only got 4 hours sleep last night and jesus I'm lazy today.
Reply by ●June 20, 20152015-06-20
On Sat, 20 Jun 2015 17:44:34 -0400, bitrex <bitrex@de.lete.earthlink.net> wrote:>On 6/20/2015 1:54 PM, John Larkin wrote: >> On Sat, 20 Jun 2015 12:40:55 -0400, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> On 6/20/2015 11:11 AM, John Larkin wrote: >>>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>>> <bitrex@de.lete.earthlink.net> wrote: >>>> >>>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>>> duration, and stretch it out long enough to flash a LED brightly enough >>>>> to be visible indoors under "ordinary" lighting conditions. >>>>> >>>>> I currently only have op-amps on the board and would rather not add any >>>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>>> fine. The pulse source into the stretcher would be low impedance. >>>>> >>>>> An optional feature would be to have the "stretch" duration decrease the >>>>> more rapidly pulses are coming into the circuit. But that is not a >>>>> requirement if it needs significant complexity. >>>> >>>> NPN emitter follower driving R-C to ground, then a comparator. Use an >>>> opamp as the comparator. >>>> >>>> >>> >>> I'm probably going to need to be using something like an LM324A. Will >>> they work OK in that role? >> >> Sure. If you have two sections available, use one open drain to >> discharge the capacitor, and the other section as the threshold >> sensor. Quiescent high, RC pulsed low. Easy. >> >> We sometimes have a "trigger" LED that is basically a stretched input. >> In some cases, we want to catch very short pulses - a couple ns - but >> also indicate a static high input. Laser drivers want that sort of >> indication. We use a fast one-shot (SN74LVC1G123) and OR its input >> into the output. >> >> > >I'm not sure I follow what you mean by using one "open drain." If you >have a moment could you show me in LTSpice? Also I only got 4 hours >sleep last night and jesus I'm lazy today.Oh, sorry, I was thinking LM339, the comparator. I'm starting to forget those antique part numbers. If you use opamps, you'll need a diode or a transistor to discharge the cap. An active discharge part (transistor or mosfet) can give fast discharge and high stretch ratios. https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretchers.JPG and here's an oldie https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretcher.JPG -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●June 20, 20152015-06-20
In article <5585dece$0$7017$4c5ecfc7@frugalusenet.com>, bitrex@de.lete.earthlink.net says...> > On 6/20/2015 1:54 PM, John Larkin wrote: > > On Sat, 20 Jun 2015 12:40:55 -0400, bitrex > > <bitrex@de.lete.earthlink.net> wrote: > > > >> On 6/20/2015 11:11 AM, John Larkin wrote: > >>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex > >>> <bitrex@de.lete.earthlink.net> wrote: > >>> > >>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms > >>>> duration, and stretch it out long enough to flash a LED brightly enough > >>>> to be visible indoors under "ordinary" lighting conditions. > >>>> > >>>> I currently only have op-amps on the board and would rather not add any > >>>> logic ICs to do this. So using low-speed op amps and discretes would be > >>>> fine. The pulse source into the stretcher would be low impedance. > >>>> > >>>> An optional feature would be to have the "stretch" duration decrease the > >>>> more rapidly pulses are coming into the circuit. But that is not a > >>>> requirement if it needs significant complexity. > >>> > >>> NPN emitter follower driving R-C to ground, then a comparator. Use an > >>> opamp as the comparator. > >>> > >>> > >> > >> I'm probably going to need to be using something like an LM324A. Will > >> they work OK in that role? > > > > Sure. If you have two sections available, use one open drain to > > discharge the capacitor, and the other section as the threshold > > sensor. Quiescent high, RC pulsed low. Easy. > > > > We sometimes have a "trigger" LED that is basically a stretched input. > > In some cases, we want to catch very short pulses - a couple ns - but > > also indicate a static high input. Laser drivers want that sort of > > indication. We use a fast one-shot (SN74LVC1G123) and OR its input > > into the output. > > > > > > I'm not sure I follow what you mean by using one "open drain." If you > have a moment could you show me in LTSpice? Also I only got 4 hours > sleep last night and jesus I'm lazy today.GND From /-\ V+ supply ___ V+ supply ( ) Threshold ref -|___|- \+/ ___ ___ | |--+|___|+-+++|___|-GND V -> + | R4 - | R3 + | short pulse + | | |/ | |\| ||-+ o--------o-| NPN +-+|-\ longer Pulse ||<- |> | >-+---o-------+--------+||-+ + +++|+/ | + | | |/| | | +-----+-----+ ___ | | | +--+|___|+--+ | + .-. R2 | --- | | | C1 --- | |R1 | + '-' | | | | | | | === === + GND GND GND (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de) C1 and R2 is the charge constant hold time before it goes below Threshold. R2 is a + feed back to aid in a little snap action for the off cycle, make sure to select a value that does not hold + input higher than the reference input while output is on, otherwise it'll latch. Jamie
Reply by ●June 20, 20152015-06-20
On 6/20/2015 7:31 PM, John Larkin wrote:> On Sat, 20 Jun 2015 17:44:34 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 6/20/2015 1:54 PM, John Larkin wrote: >>> On Sat, 20 Jun 2015 12:40:55 -0400, bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> On 6/20/2015 11:11 AM, John Larkin wrote: >>>>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>>>> <bitrex@de.lete.earthlink.net> wrote: >>>>> >>>>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>>>> duration, and stretch it out long enough to flash a LED brightly enough >>>>>> to be visible indoors under "ordinary" lighting conditions. >>>>>> >>>>>> I currently only have op-amps on the board and would rather not add any >>>>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>>>> fine. The pulse source into the stretcher would be low impedance. >>>>>> >>>>>> An optional feature would be to have the "stretch" duration decrease the >>>>>> more rapidly pulses are coming into the circuit. But that is not a >>>>>> requirement if it needs significant complexity. >>>>> >>>>> NPN emitter follower driving R-C to ground, then a comparator. Use an >>>>> opamp as the comparator. >>>>> >>>>> >>>> >>>> I'm probably going to need to be using something like an LM324A. Will >>>> they work OK in that role? >>> >>> Sure. If you have two sections available, use one open drain to >>> discharge the capacitor, and the other section as the threshold >>> sensor. Quiescent high, RC pulsed low. Easy. >>> >>> We sometimes have a "trigger" LED that is basically a stretched input. >>> In some cases, we want to catch very short pulses - a couple ns - but >>> also indicate a static high input. Laser drivers want that sort of >>> indication. We use a fast one-shot (SN74LVC1G123) and OR its input >>> into the output. >>> >>> >> >> I'm not sure I follow what you mean by using one "open drain." If you >> have a moment could you show me in LTSpice? Also I only got 4 hours >> sleep last night and jesus I'm lazy today. > > Oh, sorry, I was thinking LM339, the comparator. I'm starting to > forget those antique part numbers. > > If you use opamps, you'll need a diode or a transistor to discharge > the cap. An active discharge part (transistor or mosfet) can give fast > discharge and high stretch ratios. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretchers.JPG > > and here's an oldie > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretcher.JPG > > >Cool, thanks!
Reply by ●June 20, 20152015-06-20
On 6/20/2015 7:31 PM, John Larkin wrote:> On Sat, 20 Jun 2015 17:44:34 -0400, bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> On 6/20/2015 1:54 PM, John Larkin wrote: >>> On Sat, 20 Jun 2015 12:40:55 -0400, bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> On 6/20/2015 11:11 AM, John Larkin wrote: >>>>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>>>> <bitrex@de.lete.earthlink.net> wrote: >>>>> >>>>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>>>> duration, and stretch it out long enough to flash a LED brightly enough >>>>>> to be visible indoors under "ordinary" lighting conditions. >>>>>> >>>>>> I currently only have op-amps on the board and would rather not add any >>>>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>>>> fine. The pulse source into the stretcher would be low impedance. >>>>>> >>>>>> An optional feature would be to have the "stretch" duration decrease the >>>>>> more rapidly pulses are coming into the circuit. But that is not a >>>>>> requirement if it needs significant complexity. >>>>> >>>>> NPN emitter follower driving R-C to ground, then a comparator. Use an >>>>> opamp as the comparator. >>>>> >>>>> >>>> >>>> I'm probably going to need to be using something like an LM324A. Will >>>> they work OK in that role? >>> >>> Sure. If you have two sections available, use one open drain to >>> discharge the capacitor, and the other section as the threshold >>> sensor. Quiescent high, RC pulsed low. Easy. >>> >>> We sometimes have a "trigger" LED that is basically a stretched input. >>> In some cases, we want to catch very short pulses - a couple ns - but >>> also indicate a static high input. Laser drivers want that sort of >>> indication. We use a fast one-shot (SN74LVC1G123) and OR its input >>> into the output. >>> >>> >> >> I'm not sure I follow what you mean by using one "open drain." If you >> have a moment could you show me in LTSpice? Also I only got 4 hours >> sleep last night and jesus I'm lazy today. > > Oh, sorry, I was thinking LM339, the comparator. I'm starting to > forget those antique part numbers. > > If you use opamps, you'll need a diode or a transistor to discharge > the cap. An active discharge part (transistor or mosfet) can give fast > discharge and high stretch ratios. > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretchers.JPG > > and here's an oldie > > https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretcher.JPG > > >I think I may go with option #2 - should the op amp be configured as a comparator in that example?
Reply by ●June 20, 20152015-06-20
On Sat, 20 Jun 2015 21:41:56 -0400, bitrex <bitrex@de.lete.earthlink.net> wrote:>On 6/20/2015 7:31 PM, John Larkin wrote: >> On Sat, 20 Jun 2015 17:44:34 -0400, bitrex >> <bitrex@de.lete.earthlink.net> wrote: >> >>> On 6/20/2015 1:54 PM, John Larkin wrote: >>>> On Sat, 20 Jun 2015 12:40:55 -0400, bitrex >>>> <bitrex@de.lete.earthlink.net> wrote: >>>> >>>>> On 6/20/2015 11:11 AM, John Larkin wrote: >>>>>> On Sat, 20 Jun 2015 09:08:31 -0400, bitrex >>>>>> <bitrex@de.lete.earthlink.net> wrote: >>>>>> >>>>>>> I have a need to take a square pulse of 0V/+5V and about 5-10ms >>>>>>> duration, and stretch it out long enough to flash a LED brightly enough >>>>>>> to be visible indoors under "ordinary" lighting conditions. >>>>>>> >>>>>>> I currently only have op-amps on the board and would rather not add any >>>>>>> logic ICs to do this. So using low-speed op amps and discretes would be >>>>>>> fine. The pulse source into the stretcher would be low impedance. >>>>>>> >>>>>>> An optional feature would be to have the "stretch" duration decrease the >>>>>>> more rapidly pulses are coming into the circuit. But that is not a >>>>>>> requirement if it needs significant complexity. >>>>>> >>>>>> NPN emitter follower driving R-C to ground, then a comparator. Use an >>>>>> opamp as the comparator. >>>>>> >>>>>> >>>>> >>>>> I'm probably going to need to be using something like an LM324A. Will >>>>> they work OK in that role? >>>> >>>> Sure. If you have two sections available, use one open drain to >>>> discharge the capacitor, and the other section as the threshold >>>> sensor. Quiescent high, RC pulsed low. Easy. >>>> >>>> We sometimes have a "trigger" LED that is basically a stretched input. >>>> In some cases, we want to catch very short pulses - a couple ns - but >>>> also indicate a static high input. Laser drivers want that sort of >>>> indication. We use a fast one-shot (SN74LVC1G123) and OR its input >>>> into the output. >>>> >>>> >>> >>> I'm not sure I follow what you mean by using one "open drain." If you >>> have a moment could you show me in LTSpice? Also I only got 4 hours >>> sleep last night and jesus I'm lazy today. >> >> Oh, sorry, I was thinking LM339, the comparator. I'm starting to >> forget those antique part numbers. >> >> If you use opamps, you'll need a diode or a transistor to discharge >> the cap. An active discharge part (transistor or mosfet) can give fast >> discharge and high stretch ratios. >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretchers.JPG >> >> and here's an oldie >> >> https://dl.dropboxusercontent.com/u/53724080/Circuits/Timing/Stretcher.JPG >> >> >> > >I think I may go with option #2 - should the op amp be configured as a >comparator in that example?The one with the 2N7002? Opamps usually work OK as comparators, as long as you don't need super fast response or rise/fall times. They usually don't oscillate so generally don't need hysteresis. So there's not really a "configure as a comparator" issue. Oh, there's one gotcha. Some brands of LM324 do weird things when used as a comparator. When one section rails, it messes up the bias of the other three sections. That's because opamp sections use shared current sources. The original National part did that, maybe still does. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
