On Monday, June 26, 2023 at 11:39:14 PM UTC+1, Phil Hobbs wrote:> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote: > > John Woodgate <jmw2...@gmail.com> wrote: > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > >> (sorry about these ancient devices, but they are still good for some > >> things), but I would have to add something to make the crystal oscillate > >> unless there is a way to use the other half of the 4013 to make the oscillator. > >> > >> I also looked at using just a 4096, which gives me the oscillator, but I > >> can't see how to make it divide by 20. I know there is a technique that > >> combines some of the output signals via an EXOR to achieve divisors that > >> are not powers of 2, but I can't find information on which signals to combine. > >> > > > > Hey, John, > > > > Nice to see you back on SED, man! > > An HC40103 will do it, if you don’t mind a 5% duty cycle. > > > Plus a 74HC1G04 or something for the oscillator. > Cheers > > Phil Hobbs > > -- > Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / > Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog ElectronicsThanks, Phil. I left SED when it turned into a political forum. I will certainly look at 40103, but the duty cycle is a problem. I want to filter the output to make a sine wave with not too much distortion. I don't seem to be able to reply to this group by email. Is that the way it is set up?
Dividing a 32768 Hz crystal frequency
Started by ●June 26, 2023
Reply by ●June 26, 20232023-06-26
Reply by ●June 26, 20232023-06-26
On Monday, June 26, 2023 at 6:54:40 PM UTC-4, John Woodgate wrote:> On Monday, June 26, 2023 at 11:39:14 PM UTC+1, Phil Hobbs wrote: > > Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote: > > > John Woodgate <jmw2...@gmail.com> wrote: > > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > > >> (sorry about these ancient devices, but they are still good for some > > >> things), but I would have to add something to make the crystal oscillate > > >> unless there is a way to use the other half of the 4013 to make the oscillator. > > >> > > >> I also looked at using just a 4096, which gives me the oscillator, but I > > >> can't see how to make it divide by 20. I know there is a technique that > > >> combines some of the output signals via an EXOR to achieve divisors that > > >> are not powers of 2, but I can't find information on which signals to combine. > > >> > > > > > > Hey, John, > > > > > > Nice to see you back on SED, man! > > > An HC40103 will do it, if you don’t mind a 5% duty cycle. > > > > > Plus a 74HC1G04 or something for the oscillator. > > Cheers > > > > Phil Hobbs > > > > -- > > Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / > > Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics > Thanks, Phil. I left SED when it turned into a political forum. I will certainly look at 40103, but the duty cycle is a problem. I want to filter the output to make a sine wave with not too much distortion. > I don't seem to be able to reply to this group by email. Is that the way it is set up?There are circuits to do that using multiple outputs to create a crude approximation to a sine wave using several stair steps. Turns out, by using a good filter on the output, you really don't need more than a handful of steps to get a decent sine wave. Dig around a little, I expect you can find this circuit. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●June 26, 20232023-06-26
tirsdag den 27. juni 2023 kl. 00.39.14 UTC+2 skrev Phil Hobbs:> Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote: > > John Woodgate <jmw2...@gmail.com> wrote: > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > >> (sorry about these ancient devices, but they are still good for some > >> things), but I would have to add something to make the crystal oscillate > >> unless there is a way to use the other half of the 4013 to make the oscillator. > >> > >> I also looked at using just a 4096, which gives me the oscillator, but I > >> can't see how to make it divide by 20. I know there is a technique that > >> combines some of the output signals via an EXOR to achieve divisors that > >> are not powers of 2, but I can't find information on which signals to combine. > >> > > > > Hey, John, > > > > Nice to see you back on SED, man! > > An HC40103 will do it, if you don’t mind a 5% duty cycle. > > > Plus a 74HC1G04 or something for the oscillator.I usually see an unbuffered inverter used, and then you have to mess with drive levels and load caps. Unless power is an issue is it worth he hassle when you can get an oscillator you know will work for a dollar?
Reply by ●June 26, 20232023-06-26
tirsdag den 27. juni 2023 kl. 00.57.30 UTC+2 skrev Ricky:> On Monday, June 26, 2023 at 6:54:40 PM UTC-4, John Woodgate wrote: > > On Monday, June 26, 2023 at 11:39:14 PM UTC+1, Phil Hobbs wrote: > > > Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote: > > > > John Woodgate <jmw2...@gmail.com> wrote: > > > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > > > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > > > >> (sorry about these ancient devices, but they are still good for some > > > >> things), but I would have to add something to make the crystal oscillate > > > >> unless there is a way to use the other half of the 4013 to make the oscillator. > > > >> > > > >> I also looked at using just a 4096, which gives me the oscillator, but I > > > >> can't see how to make it divide by 20. I know there is a technique that > > > >> combines some of the output signals via an EXOR to achieve divisors that > > > >> are not powers of 2, but I can't find information on which signals to combine. > > > >> > > > > > > > > Hey, John, > > > > > > > > Nice to see you back on SED, man! > > > > An HC40103 will do it, if you don’t mind a 5% duty cycle. > > > > > > > Plus a 74HC1G04 or something for the oscillator. > > > Cheers > > > > > > Phil Hobbs > > > > > > -- > > > Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / > > > Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics > > Thanks, Phil. I left SED when it turned into a political forum. I will certainly look at 40103, but the duty cycle is a problem. I want to filter the output to make a sine wave with not too much distortion. > > I don't seem to be able to reply to this group by email. Is that the way it is set up? > There are circuits to do that using multiple outputs to create a crude approximation to a sine wave using several stair steps. Turns out, by using a good filter on the output, you really don't need more than a handful of steps to get a decent sine wave. Dig around a little, I expect you can find this circuit. >just the right amount of "flat spot" at the zero crossing (aka. "modified sine") will take of much of the third and fifth harmonic
Reply by ●June 26, 20232023-06-26
On 27/06/2023 12:20 am, John Woodgate wrote:> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. > > I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.To get 10kHz/(2*pi), why not start with a 13MHz or 26MHz xtal oscillator and divide by 8192 or 16384? (-2192 ppm) - that is closer than 32768/20 (+29437 ppm). 13 MHz and 26 MHz VCTCXOs were common in GSM phones and were quite good oscillators, low noise and stable.
Reply by ●June 26, 20232023-06-26
On Monday, June 26, 2023 at 3:57:30 PM UTC-7, Ricky wrote:> On Monday, June 26, 2023 at 6:54:40 PM UTC-4, John Woodgate wrote: > > On Monday, June 26, 2023 at 11:39:14 PM UTC+1, Phil Hobbs wrote: > > > Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote: > > > > John Woodgate <jmw2...@gmail.com> wrote: > > > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > > > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > > > >> (sorry about these ancient devices, but they are still good for some > > > >> things), but I would have to add something to make the crystal oscillate => > ...I want to filter the output to make a sine wave with not too much distortion. > > I don't seem to be able to reply to this group by email. Is that the way it is set up? > There are circuits to do that using multiple outputs to create a crude approximation to a sine wave using several stair steps. Turns out, by using a good filter on the output, you really don't need more than a handful of steps to get a decent sine wave. Dig around a little, I expect you can find this circuit.Actually, a CD4017 gives a ten-divide, with one-of-ten driven outputs, and a 4013 does a two-divide, AND... a LM13700 section can (in conjunction with nine resistors connected to 4017 output pins) take a half-wave sinusoidal current into its current-program pin. The divide-by-two after the divide-by-ten can be wired to the differential input of the LM13700 to change the current sense every halfcycle so the LM13700 output is the right twenty-point current fit to a sine. With +/- 12V supplies, all the CMOS on +12, it takes a level translator transistor (PNP grounded base) to drive the LM13700 input correctly, with resistors (from 4017 outputs to PNP emitter) being "0" output: open (infinite resistance, programs LM13700 for zero current out) "1" output: 12000 *(sin(18degrees)) ohms = 3708 ohms "2" output: 12000 *(sin 2*(18)) = 7053 ohms "3" output: 12000 *(sin 3*(18)) = 9948 ohms ... and so on. Twenty-point fit to sinewave, using nine resistors. A load on the LM13700 output (1k ohm to ground) will keep the output biased correctly, then you connect an LC tank filter. There's uncommitted darlingtons and another section of the LM13700 free, you can buffer (or maybe oscillate) with that.
Reply by ●June 26, 20232023-06-26
John Woodgate <jmw28563@gmail.com> wrote:> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > frequency for a component bridge. I could use a 4017 and half a a 4013 > (sorry about these ancient devices, but they are still good for some > things), but I would have to add something to make the crystal oscillate > unless there is a way to use the other half of the 4013 to make the > oscillator. > > I also looked at using just a 4096, which gives me the oscillator, but I > can't see how to make it divide by 20. I know there is a technique that > combines some of the output signals via an EXOR to achieve divisors that > are not powers of 2, but I can't find information on which signals to > combine.Tom Van Baak, moderator of the Time-Nuts group, posted an article years sgo on using a PIC to count down from 2 to 255. It had very low jitter. He measured the jitter in the picosecond range. The device he used was extremely cheap, and is not the same as the PIC microcrollers, which could never give picosecond timimg. I believe it had only 4 pins. I emailed him and asked for more information. I will post when he replies. -- MRM
Reply by ●June 26, 20232023-06-26
On Tuesday, June 27, 2023 at 12:20:48 AM UTC+10, John Woodgate wrote:> I want to divide a 32768 Hz crystal frequency by 20 to get a stable frequency for a component bridge. I could use a 4017 and half a a 4013 (sorry about these ancient devices, but they are still good for some things), but I would have to add something to make the crystal oscillate unless there is a way to use the other half of the 4013 to make the oscillator. > > I also looked at using just a 4096, which gives me the oscillator, but I can't see how to make it divide by 20. I know there is a technique that combines some of the output signals via an EXOR to achieve divisors that are not powers of 2, but I can't find information on which signals to combine.I had to sleep on it to remember the part but the 4060 s probably what you had in mind https://assets.nexperia.com/documents/data-sheet/HEF4060B.pdf It's got a built-in oscillator driver, and could be programmed to divide by 20. You have mentioned that you want to end up with a decent sine wave and the 4017 does offer one way of getting close to that. If you hang ten resistors - one on each of Q0 to Q9 - and feed them all into a summing junction - you can get a ten-step step-wise approximation to a sine wave, and a low pas filter can clean out the higher harmonics pretty effectively. Using the outputs to drive 4016 transmission gates can give you better controlled step heights. Buying an Analog Devices Direct Digital Synthesis Chip give you many more steps, but isn't all that cheap. -- Bill Sloman, Sydney
Reply by ●June 27, 20232023-06-27
On a sunny day (Tue, 27 Jun 2023 01:20:59 -0000 (UTC)) it happened Mike Monett VE3BTI <spamme@not.com> wrote in <XnsB02FD9304AC2Fidtokenpost@135.181.20.170>:>John Woodgate <jmw28563@gmail.com> wrote: > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable >> frequency for a component bridge. I could use a 4017 and half a a 4013 >> (sorry about these ancient devices, but they are still good for some >> things), but I would have to add something to make the crystal oscillate >> unless there is a way to use the other half of the 4013 to make the >> oscillator. >> >> I also looked at using just a 4096, which gives me the oscillator, but I >> can't see how to make it divide by 20. I know there is a technique that >> combines some of the output signals via an EXOR to achieve divisors that >> are not powers of 2, but I can't find information on which signals to >> combine. > >Tom Van Baak, moderator of the Time-Nuts group, posted an article years sgo >on using a PIC to count down from 2 to 255. It had very low jitter. He >measured the jitter in the picosecond range. > >The device he used was extremely cheap, and is not the same as the PIC >microcrollers, which could never give picosecond timimg. I believe it had >only 4 pins. > >I emailed him and asked for more information. > >I will post when he replies.Here is a Microchip PIC frequency counter: https://panteltje.nl/panteltje/pic/freq_pic/ coded by somebody else, just modified it for RS232 output as I had no suitable LCD, and put it in a RS232 connector housing. Modify it for any output? just use a preloaded downcounter? But not everybody can program PICs, can the OP? For if it realy needs to be precise I have a 10 MHz Rubidium reference too. My Casio DFC77 radio watch is always right.... And then there is GPS... https://panteltje.nl/panteltje/pic/gm_pic2/ Whats that song? "Time is on my side" Or is it? Oh, and relativity...
Reply by ●June 27, 20232023-06-27
On Tuesday, June 27, 2023 at 1:38:44 AM UTC-4, Jan Panteltje wrote:> On a sunny day (Tue, 27 Jun 2023 01:20:59 -0000 (UTC)) it happened Mike Monett > VE3BTI <spa...@not.com> wrote in <XnsB02FD9304A...@135.181.20.170>: > >John Woodgate <jmw2...@gmail.com> wrote: > > > >> I want to divide a 32768 Hz crystal frequency by 20 to get a stable > >> frequency for a component bridge. I could use a 4017 and half a a 4013 > >> (sorry about these ancient devices, but they are still good for some > >> things), but I would have to add something to make the crystal oscillate > >> unless there is a way to use the other half of the 4013 to make the > >> oscillator. > >> > >> I also looked at using just a 4096, which gives me the oscillator, but I > >> can't see how to make it divide by 20. I know there is a technique that > >> combines some of the output signals via an EXOR to achieve divisors that > >> are not powers of 2, but I can't find information on which signals to > >> combine. > > > >Tom Van Baak, moderator of the Time-Nuts group, posted an article years sgo > >on using a PIC to count down from 2 to 255. It had very low jitter. He > >measured the jitter in the picosecond range. > > > >The device he used was extremely cheap, and is not the same as the PIC > >microcrollers, which could never give picosecond timimg. I believe it had > >only 4 pins. > > > >I emailed him and asked for more information. > > > >I will post when he replies. > Here is a Microchip PIC frequency counter: > https://panteltje.nl/panteltje/pic/freq_pic/ > coded by somebody else, just modified it for RS232 output as I had no suitable LCD, > and put it in a RS232 connector housing. > Modify it for any output? just use a preloaded downcounter?I believe I would add some input protection. Is that not a problem for you? -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
