On Sat, 19 Dec 2015 18:01:43 -0600, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >news:t5SdnWucovBAV-jLnZ2dnUU7-UWdnZ2d@supernews.com... >>> For practical purposes, the threshold(s) are one-half of the CMOS >>> supply voltage (at room temp). >>> Reasonably dependable. >>> >> >> "half" in the sense of "anywhere between one third and two thirds." >> > >And that, on the properly specified kinds only. > >I've seen microcontrollers and shitty ASICs like that where the input >thresholds are 20-80%, I think even 10-90%. One boggles at how their >process can even be so awful! >I've never seen a threshold down at .3V. That would be bad!
CD4093 oscillator frequency
Started by ●December 19, 2015
Reply by ●December 20, 20152015-12-20
Reply by ●December 20, 20152015-12-20
On Sun, 20 Dec 2015 16:34:36 -0500 "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:> Tom Del Rosso wrote: > > John Larkin wrote: > >> On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex > >> <bitrex@de.lete.earthlink.net> wrote: > >> > >>> > >>> I'm buidling a little relaxaton oscillator for a project using a > >>> cd4093 quad nand gate with schmitt trigger inputs. I'm using a > >>> 200 ohm resistor and a 100n cap in the RC network. > >> > >> 200 ohms is way too low. Scale up R and scale down C, by 20:1 at > >> least. > > > > Here's another stupid question from me. If the output impedance > > inflates the value of his R then why is his frequency lower than he > > calculated? > > Nevermind. I wrote that a few seconds ago standing on my head. >Thot so. I couldn't believe what I was reading. :) joe
Reply by ●December 20, 20152015-12-20
On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex <bitrex@de.lete.earthlink.net> wrote:> >I'm buidling a little relaxaton oscillator for a project using a > cd4093 quad nand gate with schmitt trigger inputs. I'm using a > 200 ohm resistor and a 100n cap in the RC network. > >If I've done my calculations correctly, I was hoping to have an > oscillator at around 30kHz. But my frequency counter is only > showing around 8. Supply voltage is 5V. > >I understand that the frequency is dependent on the hysteresis > thresholds, which are device dependent, but I didn't expect it to > be that far off. Anything to check? > >Can I drop a crystal or ceramic resonator across the resistor to > "lock" the frequency?See "MonolithicOscCMOS.pdf" on the S.E.D/Schematics Page of my website. ...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 ●December 20, 20152015-12-20
Joe Hey wrote:> On Sun, 20 Dec 2015 16:34:36 -0500 > "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote: > >> Tom Del Rosso wrote: >>> John Larkin wrote: >>>> On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex >>>> <bitrex@de.lete.earthlink.net> wrote: >>>> >>>>> >>>>> I'm buidling a little relaxaton oscillator for a project using a >>>>> cd4093 quad nand gate with schmitt trigger inputs. I'm using a >>>>> 200 ohm resistor and a 100n cap in the RC network. >>>> >>>> 200 ohms is way too low. Scale up R and scale down C, by 20:1 at >>>> least. >>> >>> Here's another stupid question from me. If the output impedance >>> inflates the value of his R then why is his frequency lower than he >>> calculated? >> >> Nevermind. I wrote that a few seconds ago standing on my head. >> > > Thot so. I couldn't believe what I was reading. :)I'm having a lot of senior moments lately. It's got me a little worried frankly, but worrying about things might be the reason. --
Reply by ●December 21, 20152015-12-21
On Sun, 20 Dec 2015 22:16:53 -0500 "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:> Joe Hey wrote: > > On Sun, 20 Dec 2015 16:34:36 -0500 > > "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote: > > > >> Tom Del Rosso wrote: > >>> John Larkin wrote: > >>>> On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex > >>>> <bitrex@de.lete.earthlink.net> wrote: > >>>> > >>>>> > >>>>> I'm buidling a little relaxaton oscillator for a project using a > >>>>> cd4093 quad nand gate with schmitt trigger inputs. I'm using a > >>>>> 200 ohm resistor and a 100n cap in the RC network. > >>>> > >>>> 200 ohms is way too low. Scale up R and scale down C, by 20:1 at > >>>> least. > >>> > >>> Here's another stupid question from me. If the output impedance > >>> inflates the value of his R then why is his frequency lower than > >>> he calculated? > >> > >> Nevermind. I wrote that a few seconds ago standing on my head. > >> > > > > Thot so. I couldn't believe what I was reading. :) > > I'm having a lot of senior moments lately. It's got me a little > worried frankly, but worrying about things might be the reason. >A tablespoon of coconut oil a day keeps Alzheimer away[1][2][3]. joe [1] http://www.alzheimers.net/2013-05-29/coconut-oil-for-alzheimers/ [2] http://www.ncbi.nlm.nih.gov/pubmed/26667739 [3] http://www.ncbi.nlm.nih.gov/pubmed/25997382
Reply by ●December 21, 20152015-12-21
On Sun, 20 Dec 2015 16:34:36 -0500, "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:>Tom Del Rosso wrote: >> John Larkin wrote: >>> On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex >>> <bitrex@de.lete.earthlink.net> wrote: >>> >>>> >>>> I'm buidling a little relaxaton oscillator for a project using a >>>> cd4093 quad nand gate with schmitt trigger inputs. I'm using a >>>> 200 ohm resistor and a 100n cap in the RC network. >>> >>> 200 ohms is way too low. Scale up R and scale down C, by 20:1 at >>> least. >> >> Here's another stupid question from me. If the output impedance >> inflates the value of his R then why is his frequency lower than he >> calculated? > >Nevermind. I wrote that a few seconds ago standing on my head.Darn, I was fixed to jump all over that one. The bigger question is why the waveform at the cap is such a nice triangle. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●December 21, 20152015-12-21
In article <20151221184958.21849587.joehey@mailinator.com>, joehey@mailinator.com says...> > On Sun, 20 Dec 2015 22:16:53 -0500 > "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote: > > > Joe Hey wrote: > > > On Sun, 20 Dec 2015 16:34:36 -0500 > > > "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote: > > > > > >> Tom Del Rosso wrote: > > >>> John Larkin wrote: > > >>>> On Sat, 19 Dec 2015 10:52:07 -0500 (EST), bitrex > > >>>> <bitrex@de.lete.earthlink.net> wrote: > > >>>> > > >>>>> > > >>>>> I'm buidling a little relaxaton oscillator for a project using a > > >>>>> cd4093 quad nand gate with schmitt trigger inputs. I'm using a > > >>>>> 200 ohm resistor and a 100n cap in the RC network. > > >>>> > > >>>> 200 ohms is way too low. Scale up R and scale down C, by 20:1 at > > >>>> least. > > >>> > > >>> Here's another stupid question from me. If the output impedance > > >>> inflates the value of his R then why is his frequency lower than > > >>> he calculated? > > >> > > >> Nevermind. I wrote that a few seconds ago standing on my head. > > >> > > > > > > Thot so. I couldn't believe what I was reading. :) > > > > I'm having a lot of senior moments lately. It's got me a little > > worried frankly, but worrying about things might be the reason. > > > > A tablespoon of coconut oil a day keeps Alzheimer away[1][2][3]. > > joe > > > [1] http://www.alzheimers.net/2013-05-29/coconut-oil-for-alzheimers/ > [2] http://www.ncbi.nlm.nih.gov/pubmed/26667739 > [3] http://www.ncbi.nlm.nih.gov/pubmed/25997382If only you can remember to take it! Now what was it we were talking about? Sounds to me the coconut business is slowing. Jamie
Reply by ●December 21, 20152015-12-21
M Philbrook wrote:> > Sounds to me the coconut business is slowing.Maybe the migrating swallows will bring more. --
Reply by ●December 21, 20152015-12-21
On Saturday, December 19, 2015 at 10:52:34 AM UTC-5, bitrex wrote:> I'm buidling a little relaxaton oscillator for a project using a > cd4093 quad nand gate with schmitt trigger inputs. I'm using a > 200 ohm resistor and a 100n cap in the RC network. > > If I've done my calculations correctly, I was hoping to have an > oscillator at around 30kHz. But my frequency counter is only > showing around 8. Supply voltage is 5V. > > I understand that the frequency is dependent on the hysteresis > thresholds, which are device dependent, but I didn't expect it to > be that far off. Anything to check?The other guys have already straightened you out on not loading 4000 CMOS with 200 ohms. As far as depending on hysteresis, you can make the oscillator largely independent of hysteresis and thresholds by greatly increasing the voltage swing across the timing cap. I solved that problem from scratch a few months ago, only to find I'd been beaten by, um, thirty years or so... This oscillator... Fig. 1 ====== |\ .----| >o--+--> | |/ | | Rt | | '----------+ | --- Ct --- | --- has a timing swing across timing cap Ct equal to merely the hysteresis voltage, a small and highly variable quantity that varies with Vdd. Fig. 2 ====== If you drive Ct's "cold" end with a buffer, though, you increase the swing by Vdd in each direction, making the timing dramatically less dependent on threshold or hysteresis. R1 is a high value resistor to prevent the CMOS gate's input diodes from conducting and spoiling the R*C time constant. For accuracy, most of the timing current should flow thru Rt, thus, R1 >= 3 or 4*Rt. |\ |\ .-- R1 --| >o--+---| >o--+--> | |/ | |/ | | Rt | | | Ct | '--------------+----||---' The resulting behavior is surprisingly close to ideal. Cheers, James Arthur
Reply by ●December 21, 20152015-12-21
In article <n5a3t6$hgs$1@dont-email.me>, "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:> M Philbrook wrote: > > > > Sounds to me the coconut business is slowing. > > Maybe the migrating swallows will bring more.African or European swallows? -- Cats, coffee, chocolate...vices to live by Please don't feed the trolls. Killfile and ignore them so they will go away.
