On 8/3/19 4:00 PM, John Larkin wrote:> On Sat, 3 Aug 2019 15:12:01 -0400, bitrex <user@example.net> wrote: > >> On 8/3/19 2:40 PM, Rick C wrote: >>> On Saturday, August 3, 2019 at 2:28:58 PM UTC-4, Tauno Voipio wrote: >>>> On 3.8.19 19:08, bitrex wrote: >>>>> On 8/3/19 12:06 PM, bitrex wrote: >>>>>> IRL I don't think there's anything this configuration of the 'HC74 >>>>>> could do but oscillate; with an RC network from not-Q to not-CLR and >>>>>> D, CLK, and not-PRE grounded. >>>>>> >>>>>> But with these models from the Yahoo LTSpice users group the LTSPice >>>>>> time domain looks like it manages to find some other metastable state >>>>>> and sits there spinning its wheels. >>>>>> >>>>>> Can anyone suggest some ICs that could bust it out and get it to >>>>>> square-wave in the sim? Thanks >>>>>> >>>>>> <https://imgur.com/a/Idv4LSs> >>>>> >>>>> plz use this link instead >>>>> >>>>> <https://imgur.com/a/ochGSav> >>>> >>>> Your circuit is simply wrong: there is a stable state >>>> with both Q- and CLR- high. >>> >>> I think not. The PRE- pin is grounded. If CLR- is high the Q is 1 and Q- is 0. The circuit should work in simulation. If the waveform shown in the picture is anything relative to the Q- output, there is something logically wrong with the simulation... which is very possible if the FF doesn't initialize properly. >>> >> >> With the error that I made wrt setting parameters corrected and the sim >> tested such that the flip flop divides down and otherwise operates >> correctly here is the output in the former configuration, with more >> clear labeling of voltages. also no oscillation. >> >> <https://imgur.com/a/tHr6Qij> > > You might try a real flop. The model may not properly handle this > case. > >Yeah I don't know if it's a model problem at this point or if this circuit is just a bust I'm curious now. It would be amusing/sad if that referenced patent just didn't work at all. Maybe the crystal makes the "magic" happen
74HC74 oscillator simulation
Started by ●August 3, 2019
Reply by ●August 3, 20192019-08-03
Reply by ●August 3, 20192019-08-03
On 8/3/19 1:34 PM, bitrex wrote:> On 8/3/19 12:59 PM, John Larkin wrote: >> On Sat, 03 Aug 2019 09:24:40 -0700, John Larkin >> <jjlarkin@highlandtechnology.com> wrote: >> >>> On Sat, 3 Aug 2019 12:06:05 -0400, bitrex <user@example.net> wrote: >>> >>>> IRL I don't think there's anything this configuration of the 'HC74 >>>> could >>>> do but oscillate; with an RC network from not-Q to not-CLR and D, CLK, >>>> and not-PRE grounded. >>>> >>>> But with these models from the Yahoo LTSpice users group the LTSPice >>>> time domain looks like it manages to find some other metastable state >>>> and sits there spinning its wheels. >>>> >>>> Can anyone suggest some ICs that could bust it out and get it to >>>> square-wave in the sim? Thanks >>>> >>>> <https://imgur.com/a/Idv4LSs> >>> >>> The voltage gain from \Q to \CLR is low, >> >> Actually meant \CLR to \Q, the gain inside the IC. >> >> > > The easy thing to do to get a square wave is the schmitt inverter, I'd > like a low frequency (10s of Hz) with the Q and not Q outputs but I > don't wanna use a large R, large cap, wanna use a small R and cap that's > relatively cheap to get tight tolerance/tempco on the components. > > The easy thing to then do is run a higher frequency from the standard > schmitt inverter with smaller Rc, C into a divider chain. > > But it would be cool if there were some self-oscillating structure of > flops that did it all without needing the Schmitt inverter at all, so > far my attempts to find it have been unproductive though > > If you have Q and not Q whether from a flip-flop or just from a set of > appropriately-connected inverters it might be possible to bootstrap the > RC constant capacitor somehow instead of grounding it.I think a ripple counter would work fine to divide down a clock from a faster Schmitt oscillator, also. Then I could use the fast clock for some other purpose. That'd be cool.
Reply by ●August 3, 20192019-08-03
On Saturday, August 3, 2019 at 4:14:51 PM UTC-4, bitrex wrote:> On 8/3/19 4:00 PM, John Larkin wrote: > > On Sat, 3 Aug 2019 15:12:01 -0400, bitrex <user@example.net> wrote: > >> > >> With the error that I made wrt setting parameters corrected and the sim > >> tested such that the flip flop divides down and otherwise operates > >> correctly here is the output in the former configuration, with more > >> clear labeling of voltages. also no oscillation. > >> > >> <https://imgur.com/a/tHr6Qij> > > > > You might try a real flop. The model may not properly handle this > > case. > > > > > > Yeah I don't know if it's a model problem at this point or if this > circuit is just a bust I'm curious now. > > It would be amusing/sad if that referenced patent just didn't work at > all. Maybe the crystal makes the "magic" happenIt's not magic. Just that most people aren't familiar with the issues of designing an oscillator. I assume this is not a circuit which is important to operate in a real circuit. Oscillators like this can have intermittent startup problems. I just use oscillators these days. Easier. Even when the oscillator is in an MCU they do a crappy job of specifying the crystal parameters. You have to beg for things like ESR of the crystal. Pick the wrong part and it will work fine on the bench, them may not start reliably with changes in temperature, etc. You could try working that thread again. I can't find the model you indicate at ADI (bought LT). Try copying the text in Harald's post and make helmut's modification. Harald said that was what worked for him. -- Rick C. -+ Get 1,000 miles of free Supercharging -+ Tesla referral code - https://ts.la/richard11209
Reply by ●August 3, 20192019-08-03
On 8/3/19 4:32 PM, Rick C wrote:> On Saturday, August 3, 2019 at 4:14:51 PM UTC-4, bitrex wrote: >> On 8/3/19 4:00 PM, John Larkin wrote: >>> On Sat, 3 Aug 2019 15:12:01 -0400, bitrex <user@example.net> wrote: >>>> >>>> With the error that I made wrt setting parameters corrected and the sim >>>> tested such that the flip flop divides down and otherwise operates >>>> correctly here is the output in the former configuration, with more >>>> clear labeling of voltages. also no oscillation. >>>> >>>> <https://imgur.com/a/tHr6Qij> >>> >>> You might try a real flop. The model may not properly handle this >>> case. >>> >>> >> >> Yeah I don't know if it's a model problem at this point or if this >> circuit is just a bust I'm curious now. >> >> It would be amusing/sad if that referenced patent just didn't work at >> all. Maybe the crystal makes the "magic" happen > > It's not magic. Just that most people aren't familiar with the issues of designing an oscillator. I assume this is not a circuit which is important to operate in a real circuit. Oscillators like this can have intermittent startup problems. I just use oscillators these days. Easier. Even when the oscillator is in an MCU they do a crappy job of specifying the crystal parameters. You have to beg for things like ESR of the crystal. Pick the wrong part and it will work fine on the bench, them may not start reliably with changes in temperature, etc. > > You could try working that thread again. I can't find the model you indicate at ADI (bought LT). Try copying the text in Harald's post and make helmut's modification. Harald said that was what worked for him. >I'm just gonna feed a faster Schmitt trigger-oscillator clock into a a long counter I think so I can divide it down to a few Hz and use the faster clock for some other purpose. The single gate or two-gate NAND schmitt oscillator is not sexy but it's pretty reliable. You're right it might be possible to get this to work with fiddling in simulation but I need something that will work consistently IRL, not any point in spending much more effort on it. I thought it would be cool if there were a way to make say a quad D flop self-oscillate and divide itself down but sounds like a challenge for another day
Reply by ●August 3, 20192019-08-03
On Sat, 3 Aug 2019 16:31:23 -0400, bitrex <user@example.net> wrote:>On 8/3/19 1:34 PM, bitrex wrote: >> On 8/3/19 12:59 PM, John Larkin wrote: >>> On Sat, 03 Aug 2019 09:24:40 -0700, John Larkin >>> <jjlarkin@highlandtechnology.com> wrote: >>> >>>> On Sat, 3 Aug 2019 12:06:05 -0400, bitrex <user@example.net> wrote: >>>> >>>>> IRL I don't think there's anything this configuration of the 'HC74 >>>>> could >>>>> do but oscillate; with an RC network from not-Q to not-CLR and D, CLK, >>>>> and not-PRE grounded. >>>>> >>>>> But with these models from the Yahoo LTSpice users group the LTSPice >>>>> time domain looks like it manages to find some other metastable state >>>>> and sits there spinning its wheels. >>>>> >>>>> Can anyone suggest some ICs that could bust it out and get it to >>>>> square-wave in the sim? Thanks >>>>> >>>>> <https://imgur.com/a/Idv4LSs> >>>> >>>> The voltage gain from \Q to \CLR is low, >>> >>> Actually meant \CLR to \Q, the gain inside the IC. >>> >>> >> >> The easy thing to do to get a square wave is the schmitt inverter, I'd >> like a low frequency (10s of Hz) with the Q and not Q outputs but I >> don't wanna use a large R, large cap, wanna use a small R and cap that's >> relatively cheap to get tight tolerance/tempco on the components. >> >> The easy thing to then do is run a higher frequency from the standard >> schmitt inverter with smaller Rc, C into a divider chain. >> >> But it would be cool if there were some self-oscillating structure of >> flops that did it all without needing the Schmitt inverter at all, so >> far my attempts to find it have been unproductive though >> >> If you have Q and not Q whether from a flip-flop or just from a set of >> appropriately-connected inverters it might be possible to bootstrap the >> RC constant capacitor somehow instead of grounding it. > >I think a ripple counter would work fine to divide down a clock from a >faster Schmitt oscillator, also. Then I could use the fast clock for >some other purpose. That'd be cool.Packaged XOs are so cheap now it's barely worth making your own oscillator. Well, maybe a schmitt if the frequency accuracy doesn't matter much. Small uPs usually have a pretty good internal oscillator. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●August 3, 20192019-08-03
On 8/3/19 4:48 PM, John Larkin wrote:> On Sat, 3 Aug 2019 16:31:23 -0400, bitrex <user@example.net> wrote: > >> On 8/3/19 1:34 PM, bitrex wrote: >>> On 8/3/19 12:59 PM, John Larkin wrote: >>>> On Sat, 03 Aug 2019 09:24:40 -0700, John Larkin >>>> <jjlarkin@highlandtechnology.com> wrote: >>>> >>>>> On Sat, 3 Aug 2019 12:06:05 -0400, bitrex <user@example.net> wrote: >>>>> >>>>>> IRL I don't think there's anything this configuration of the 'HC74 >>>>>> could >>>>>> do but oscillate; with an RC network from not-Q to not-CLR and D, CLK, >>>>>> and not-PRE grounded. >>>>>> >>>>>> But with these models from the Yahoo LTSpice users group the LTSPice >>>>>> time domain looks like it manages to find some other metastable state >>>>>> and sits there spinning its wheels. >>>>>> >>>>>> Can anyone suggest some ICs that could bust it out and get it to >>>>>> square-wave in the sim? Thanks >>>>>> >>>>>> <https://imgur.com/a/Idv4LSs> >>>>> >>>>> The voltage gain from \Q to \CLR is low, >>>> >>>> Actually meant \CLR to \Q, the gain inside the IC. >>>> >>>> >>> >>> The easy thing to do to get a square wave is the schmitt inverter, I'd >>> like a low frequency (10s of Hz) with the Q and not Q outputs but I >>> don't wanna use a large R, large cap, wanna use a small R and cap that's >>> relatively cheap to get tight tolerance/tempco on the components. >>> >>> The easy thing to then do is run a higher frequency from the standard >>> schmitt inverter with smaller Rc, C into a divider chain. >>> >>> But it would be cool if there were some self-oscillating structure of >>> flops that did it all without needing the Schmitt inverter at all, so >>> far my attempts to find it have been unproductive though >>> >>> If you have Q and not Q whether from a flip-flop or just from a set of >>> appropriately-connected inverters it might be possible to bootstrap the >>> RC constant capacitor somehow instead of grounding it. >> >> I think a ripple counter would work fine to divide down a clock from a >> faster Schmitt oscillator, also. Then I could use the fast clock for >> some other purpose. That'd be cool. > > Packaged XOs are so cheap now it's barely worth making your own > oscillator. Well, maybe a schmitt if the frequency accuracy doesn't > matter much. > > Small uPs usually have a pretty good internal oscillator. > >uP's are so cheap and easy that there's little reason for me to not recommend one for most simple projects right off the bat This is a great tool, it lets you drag and drop little functional blocks like "voltage controlled" oscillators, logic gates, functional blocks of various types and bang it up to an 8 pin AVR in about 5 minutes: <https://xod.io/> But I don't turn down money because a client asks me to design something they'd like to build themselves without a uP and wants to pay me some cash for my nice-dinner-with-the-girlfriend fund for doing it
Reply by ●August 3, 20192019-08-03
On Saturday, August 3, 2019 at 4:43:16 PM UTC-4, bitrex wrote:> On 8/3/19 4:32 PM, Rick C wrote: > > On Saturday, August 3, 2019 at 4:14:51 PM UTC-4, bitrex wrote: > >> On 8/3/19 4:00 PM, John Larkin wrote: > >>> On Sat, 3 Aug 2019 15:12:01 -0400, bitrex <user@example.net> wrote: > >>>> > >>>> With the error that I made wrt setting parameters corrected and the sim > >>>> tested such that the flip flop divides down and otherwise operates > >>>> correctly here is the output in the former configuration, with more > >>>> clear labeling of voltages. also no oscillation. > >>>> > >>>> <https://imgur.com/a/tHr6Qij> > >>> > >>> You might try a real flop. The model may not properly handle this > >>> case. > >>> > >>> > >> > >> Yeah I don't know if it's a model problem at this point or if this > >> circuit is just a bust I'm curious now. > >> > >> It would be amusing/sad if that referenced patent just didn't work at > >> all. Maybe the crystal makes the "magic" happen > > > > It's not magic. Just that most people aren't familiar with the issues of designing an oscillator. I assume this is not a circuit which is important to operate in a real circuit. Oscillators like this can have intermittent startup problems. I just use oscillators these days. Easier. Even when the oscillator is in an MCU they do a crappy job of specifying the crystal parameters. You have to beg for things like ESR of the crystal. Pick the wrong part and it will work fine on the bench, them may not start reliably with changes in temperature, etc. > > > > You could try working that thread again. I can't find the model you indicate at ADI (bought LT). Try copying the text in Harald's post and make helmut's modification. Harald said that was what worked for him. > > > > I'm just gonna feed a faster Schmitt trigger-oscillator clock into a a > long counter I think so I can divide it down to a few Hz and use the > faster clock for some other purpose. The single gate or two-gate NAND > schmitt oscillator is not sexy but it's pretty reliable. > > You're right it might be possible to get this to work with fiddling in > simulation but I need something that will work consistently IRL, not any > point in spending much more effort on it. > > I thought it would be cool if there were a way to make say a quad D flop > self-oscillate and divide itself down but sounds like a challenge for > another dayThe circuit is the same as an inverter, just no Schmitt trigger. The quad FF doesn't have the preset and clear controls that turn one stage into an inverter. You could wire one stage to be a divide by two, use a differentiator to produce glitches with a diode to clamp the low going pulses so they become positive pulses. That would be a tricky circuit. -- Rick C. +- Get 1,000 miles of free Supercharging +- Tesla referral code - https://ts.la/richard11209
Reply by ●August 3, 20192019-08-03
On 8/3/19 5:10 PM, bitrex wrote:>> Small uPs usually have a pretty good internal oscillator. >> >> > > uP's are so cheap and easy that there's little reason for me to not > recommend one for most simple projects right off the bat > > This is a great tool, it lets you drag and drop little functional blocks > like "voltage controlled" oscillators, logic gates, functional blocks of > various types and bang it up to an 8 pin AVR in about 5 minutes: > > <https://xod.io/>There's a niche for low-speed hairball logic-like circuitry, that being able to "program" a microprocessor visually and end up with a "circuit" but expressed in auto-generated code, but that is provably glitch-free and that runs on a general-purpose uP that this tool fills very nicely
Reply by ●August 4, 20192019-08-04
On Sunday, August 4, 2019 at 5:12:06 AM UTC+10, John Larkin wrote:> On Sat, 3 Aug 2019 21:31:15 +0300, Tauno Voipio > <tauno.voipio@notused.fi.invalid> wrote: > > >On 3.8.19 19:58, bitrex wrote: > >> On 8/3/19 12:24 PM, John Larkin wrote: > >>> On Sat, 3 Aug 2019 12:06:05 -0400, bitrex <user@example.net> wrote: > >>> > >>>> IRL I don't think there's anything this configuration of the 'HC74 could > >>>> do but oscillate; with an RC network from not-Q to not-CLR and D, CLK, > >>>> and not-PRE grounded. > >>>> > >>>> But with these models from the Yahoo LTSpice users group the LTSPice > >>>> time domain looks like it manages to find some other metastable state > >>>> and sits there spinning its wheels. > >>>> > >>>> Can anyone suggest some ICs that could bust it out and get it to > >>>> square-wave in the sim? Thanks > >>>> > >>>> <https://imgur.com/a/Idv4LSs> > >>> > >>> The voltage gain from \Q to \CLR is low, and there's no schmitt > >>> action, so you can get a stable negative feedback loop. It would > >>> likely oscillate at a higher frequency, where the logic prop delay > >>> becomes important. > >>> > >>> Why not use a schmitt inverter? This circuit could be rescued, but it > >>> would take more parts. > >>> > >>> Maybe "ground" C1 to Q? > >>> > >>> But I wouldn't trust the Spice models for what is basically analog > >>> behavior. > >>> > >>> > >> > >> Check this out someone actually got a patent for this back in 1990 (the > >> crystal probably helps a lot): > >> > >> <https://imgur.com/a/YryI2p6> > > > >An idea can be patented even if it does not work. > > For some people, getting patents is a kind of addiction.Places like IBM, Bell Labs and EMI Central Research had teams of patent lawyers, and a culture where the staff were encourage to put in patent queries. One of my colleagues at EMI held the record for patent queries filed in any one year. None of them went through. One of the two I got resulted from what had struck me as a perfectly obvious point, but after I'd had to explain it to some half-dozen people I decided that it probably wasn't obvious to those skilled in the art. The patent examiners agreed. -- Bill Sloman, Sydney
Reply by ●August 4, 20192019-08-04
On Saturday, August 3, 2019 at 9:06:10 AM UTC-7, bitrex wrote:> IRL I don't think there's anything this configuration of the 'HC74 could > do but oscillateThe innards of a master/slave D flipflop are huge; a simpler oscillator (ring oscillator) just takes an odd number of inverters, so in CMOS it starts at six transistors, maybe even two, no external capacitors/resistors required. One generally uses other things, to minimize side-effects (power supply current spikes) , and timing components accurate over temperature, aging, device variation.
