On 12/19/2015 04:17 PM, Robert Baer wrote:> 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? >> >> Can I drop a crystal or ceramic resonator across the resistor to >> "lock" the frequency? >> > 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." Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
CD4093 oscillator frequency
Started by ●December 19, 2015
Reply by ●December 19, 20152015-12-19
Reply by ●December 19, 20152015-12-19
John Larkin <jjlarkin@highlandtechnology.com> Wrote in message:> 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. > > >I'm now using a 68k R and a 680 p polystyrene capacitor - I'm right in the 32 kHz ballpark. -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
Reply by ●December 19, 20152015-12-19
On 2015-12-19, 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?when a CD4060 is run from crystal it seems that it does not use a schmitt inverter what frequency are you chasing? 32768 Hz is a standard frequency. -- \_(ツ)_
Reply by ●December 19, 20152015-12-19
"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! Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
Reply by ●December 20, 20152015-12-20
On Sunday, 20 December 2015 00:00:50 UTC, Tim Williams wrote:> 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!and smiles at the price
Reply by ●December 20, 20152015-12-20
On Saturday, December 19, 2015 at 12:50:45 PM UTC-5, 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.You'll be hosting Romper Room next...
Reply by ●December 20, 20152015-12-20
On Sun, 20 Dec 2015 09:26:44 -0800 (PST), bloggs.fredbloggs.fred@gmail.com wrote:>On Saturday, December 19, 2015 at 12:50:45 PM UTC-5, 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. > >You'll be hosting Romper Room next...And you'll be organizing Canasta games at the managed care facility.
Reply by ●December 20, 20152015-12-20
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? --
Reply by ●December 20, 20152015-12-20
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. --
Reply by ●December 20, 20152015-12-20
"Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> Wrote in message:> 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. > > -- >Mornings are the times for thinking...this time of the afternoon is for drinking -- ----Android NewsGroup Reader---- http://usenet.sinaapp.com/
