Dividing a 32768 Hz crystal frequency...

[John Woodgate]

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?

 

[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.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Lasse Langwadt Christensen]

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?

 

[Lasse Langwadt Christensen]

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

 

[Chris Jones]

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.

 

[whit3rd]

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.

 

[Mike Monett VE3BTI]

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

 

[Anthony William Sloman]

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

 

[Jan Panteltje]

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...

 

[Ricky]

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

 

[Martin Brown]

On 26/06/2023 23:54, 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

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.

Depending on how much is not much then for a spot frequency integrating
it once and diode shaping followed by a filter will get all the higher
harmonics well down. HP patent on this trick is long out of date.

I\'m curious - what is special about 1591.55 Hz ?

To do that you actually want to divide 32768 by (almost)
20.6 which gets 1590.68 or easier 20.5 which gets 1598.44

20 21 alternately and then combine with the original clock signal to get
20.5 20.5 equal mark space ratio at your chosen frequency.

20 21 20 21 20 would get your 20.6 but with terrible phase noise and
harmonic content that might well be more problematic to eliminate.

> Is that the way it is set up?

More likely how your news client is set up.
Thunderbird has \"Reply\" (to author) as one of its buttons.

Updates sometimes promote it to being the default action too!

--
Martin Brown

 

[Jasen Betts]

On 2023-06-26, John Woodgate <jmw28563@gmail.com> wrote:

On Monday, June 26, 2023 at 4:09:51 PM UTC+1, John Larkin wrote:
On Mon, 26 Jun 2023 08:00:44 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

mandag den 26. juni 2023 kl. 16.20.48 UTC+2 skrev John Woodgate:
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.

get a 32768 Hz oscillator instead of a crystal, saves alot of headaches
Yes. Oscillators made from a crystal and a chip and some caps and
maybe a resistor, tend to not oscillate. And certainly won\'t be PPMs
on-frequency, as a purchased oscillator usually is.

Maybe play with the math and use some other oscillator frequency and
some easy divisor?
I think I\'d be very lucky to find a better combination of crystal frequency and division ratio. But if you could suggest a simple way of getting closer to 1591.55 Hz I would be very interested.

1638.4Hz doesn\'t seem especially close 3%


25.6khz/16 = 1600Hz unfortunately this crystal is out of stock everywhere I looked.

100Khz/64 = 1562.5 can do this with a CD4060 and a crystal

6.5MHz/4096 = 1586.9 maybe possible with a CD4060 but probably need more than 5V

and I\'m only looking a power of two divisors.

--
Jasen.
🇺🇦 Слава Україні

 

[Phil Allison]

John Woodgate wrote:
-------------------------------------

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.

** How temp stable does the frequency REALLY have to be for your app ??
If 3% away from ideal f is OK - maybe no crystal or ceramic doovey is needed.

How about a one ( cheap) IC, linear RC oscillator with near perfect sine output - allows adjustable f to spot on your desired number.
Using 1% MF resistors and polystyrene caps, temp stability can be suprisingly good.


BTW nice to see you back.



.......Phil

 

[John Woodgate]

On Tuesday, June 27, 2023 at 8:15:58 AM UTC+1, Martin Brown wrote:

On 26/06/2023 23:54, 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

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.
Depending on how much is not much then for a spot frequency integrating
it once and diode shaping followed by a filter will get all the higher
harmonics well down. HP patent on this trick is long out of date.

I\'m curious - what is special about 1591.55 Hz ?

To do that you actually want to divide 32768 by (almost)
20.6 which gets 1590.68 or easier 20.5 which gets 1598.44

20 21 alternately and then combine with the original clock signal to get
20.5 20.5 equal mark space ratio at your chosen frequency.

20 21 20 21 20 would get your 20.6 but with terrible phase noise and
harmonic content that might well be more problematic to eliminate.
Is that the way it is set up?
More likely how your news client is set up.
Thunderbird has \"Reply\" (to author) as one of its buttons.

Updates sometimes promote it to being the default action too!

--
Martin Brown
Thanks, Martin and all the others who have given helpful advice --- too many to reply individually. The project is tutorial in nature, so I don\'t want to use too many \'integrated\' fixes, and SMD-only devices are not an option. Regarding the frequency, it does need to be near 10k/2pi, but other things can be adjusted to suit the exact frequency, which needs to be stable within ±1% and not require a counter to determine it.

I will try \'Reply to list\' instead of \'Reply\' to see if that works.

 

[Jan Panteltje]

On a sunny day (Mon, 26 Jun 2023 23:20:14 -0700 (PDT)) it happened Ricky
<gnuarm.deletethisbit@gmail.com> wrote in
<c49794d7-262f-4006-9b9e-5cc15ed60dd7n@googlegroups.com>:

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 M=
onett
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 oscilla=
te
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 tha=
t
combines some of the output signals via an EXOR to achieve divisors th=
at
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 ha=
d
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=
?

Well, 100 pF does not form a low impedance for slow things like mains.
PIC datasheet specifies a clamp-current for the input pins;
Clamp current, IK (VPIN < 0 or VPIN > VDD) ± 20 mA
So now you can calculate how much and how fast an input voltage change you need with 100 pF for destruction.
Ask Martin?
Its still working AFAIK after so many years.
But I do not work with pico seconds rise time kilovolts.
Mostly use higher frequencies and spectrum analyzers based on RTL_SDR sticks, accuracy 1ppm and more info:
http://panteltje.nl/pub/spectrum_analyzer_IX_IMG_0699.JPG
http://panteltje.nl/pub/radar10_135000000_versus_1374576000_MHz.mpeg

You can make it as complicated and precise as you want:
https://panteltje.nl/pub/FPGA_board_with_25MHz_VCXO_locked_to_rubidium_10MHz_reference_IMG_3724.GIF
https://panteltje.nl/pub/GPS_L1_locked_to_rubidium_reference_test_setup_IMG_3733.GIF
was that not from my artificial GPS sattelite Mr Bond?

Does this help?

 

[Martin Brown]

On 27/06/2023 10:17, John Woodgate wrote:

On Tuesday, June 27, 2023 at 8:15:58 AM UTC+1, Martin Brown wrote:

I\'m curious - what is special about 1591.55 Hz ?

To do that you actually want to divide 32768 by (almost) 20.6 which
gets 1590.68 or easier 20.5 which gets 1598.44

20 21 alternately and then combine with the original clock signal
to get 20.5 20.5 equal mark space ratio at your chosen frequency.

20 21 20 21 20 would get your 20.6 but with terrible phase noise
and harmonic content that might well be more problematic to
eliminate.

Is that the way it is set up?
More likely how your news client is set up. Thunderbird has \"Reply\"
(to author) as one of its buttons.

Updates sometimes promote it to being the default action too!

-- Martin Brown

Thanks, Martin and all the others who have given helpful advice ---
too many to reply individually. The project is tutorial in nature,
so I don\'t want to use too many \'integrated\' fixes, and SMD-only
devices are not an option. Regarding the frequency, it does need to
be near 10k/2pi, but other things can be adjusted to suit the exact
frequency, which needs to be stable within ±1% and not require a
counter to determine it.

OK. How about a Wein bridge sine wave oscillator instead then?
eg.

https://www.analog.com/en/technical-articles/analysis-of-a-digitally-controlled-wienbridge-oscillator.html

You could even discipline it against a square wave reference frequency
derived from the 32kHz xtal oscillator.

--
Martin Brown

 

[Phil Hobbs]

John Woodgate <jmw28563@gmail.com> wrote:

On Tuesday, June 27, 2023 at 8:15:58 AM UTC+1, Martin Brown wrote:
On 26/06/2023 23:54, 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

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.
Depending on how much is not much then for a spot frequency integrating
it once and diode shaping followed by a filter will get all the higher
harmonics well down. HP patent on this trick is long out of date.

I\'m curious - what is special about 1591.55 Hz ?

To do that you actually want to divide 32768 by (almost)
20.6 which gets 1590.68 or easier 20.5 which gets 1598.44

20 21 alternately and then combine with the original clock signal to get
20.5 20.5 equal mark space ratio at your chosen frequency.

20 21 20 21 20 would get your 20.6 but with terrible phase noise and
harmonic content that might well be more problematic to eliminate.
Is that the way it is set up?
More likely how your news client is set up.
Thunderbird has \"Reply\" (to author) as one of its buttons.

Updates sometimes promote it to being the default action too!

--
Martin Brown
Thanks, Martin and all the others who have given helpful advice --- too
many to reply individually. The project is tutorial in nature, so I
don\'t want to use too many \'integrated\' fixes, and SMD-only devices are
not an option. Regarding the frequency, it does need to be near 10k/2pi,
but other things can be adjusted to suit the exact frequency, which needs
to be stable within ±1% and not require a counter to determine it.

I will try \'Reply to list\' instead of \'Reply\' to see if that works.

Some years ago, we had a George Herold thread on making sine waves. The
eventual solution was a 4017 with resistors forming a weighted sum of the
outputs. This cancels the second through ninth harmonics, making filtering
much easier.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[Phil Allison]

John Woodgate wrote:

-----------------------------------------

The project is tutorial in nature, so I don\'t want to use too many \'integrated\' fixes, and SMD-only devices are not an option.
Regarding the frequency, it does need to be near 10k/2pi, but other things can be adjusted to suit the exact frequency,
which needs to be stable within ±1% and not require a counter to determine it.

** OK - we finally have an actual \" spec\" for your 1591 Hz sine wave oscillator.

This simple topology will do the job very easily:

https://sound-au.com/project86.htm

The DC supply can be to 9v as shown, or +/- 5V or up to +/- 15 v.
Quad op-amps like the TL064 or TL074 are perfect - so are many other duals.

THD is about 0.15% and frequency can be trimmed by adjusting one or both RT values as shown in fig 2.
Amplitude stability depends only on the tempco of the 4 diodes.

Essentially it is my design and many hundreds have been built.
Way better than a Wein bridge topology since there\'s no need for ( now unobtainable) thermistors, tiny lamps or fussy FETs.


..... Phil

 

[Ricky]

On Tuesday, June 27, 2023 at 6:00:27 AM UTC-4, Jan Panteltje wrote:

On a sunny day (Mon, 26 Jun 2023 23:20:14 -0700 (PDT)) it happened Ricky
gnuarm.del...@gmail.com> wrote in
c49794d7-262f-4006...@googlegroups.com>:
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 M> >onett
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 oscilla> >te
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 tha=
t
combines some of the output signals via an EXOR to achieve divisors th=
at
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 ha> >d
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=
?

Well, 100 pF does not form a low impedance for slow things like mains.
PIC datasheet specifies a clamp-current for the input pins;
Clamp current, IK (VPIN < 0 or VPIN > VDD) ± 20 mA
So now you can calculate how much and how fast an input voltage change you need with 100 pF for destruction.
Ask Martin?
Its still working AFAIK after so many years.
But I do not work with pico seconds rise time kilovolts.
Mostly use higher frequencies and spectrum analyzers based on RTL_SDR sticks, accuracy 1ppm and more info:
http://panteltje.nl/pub/spectrum_analyzer_IX_IMG_0699.JPG
http://panteltje.nl/pub/radar10_135000000_versus_1374576000_MHz.mpeg

You can make it as complicated and precise as you want:
https://panteltje.nl/pub/FPGA_board_with_25MHz_VCXO_locked_to_rubidium_10MHz_reference_IMG_3724.GIF
https://panteltje.nl/pub/GPS_L1_locked_to_rubidium_reference_test_setup_IMG_3733.GIF
was that not from my artificial GPS sattelite Mr Bond?

Does this help?

What\'s the rise time of touching some voltage rail? I don\'t see even a resistor, to allow the capacitor to form an RC circuit, so I suppose this is depending on the parasitic diodes to prevent damage. That\'s my point. There\'s nothing to limit the current through the diodes, including your nonsense about kilovolt, ps rise time signals.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Tuesday, June 27, 2023 at 5:17:21 AM UTC-4, John Woodgate wrote:

On Tuesday, June 27, 2023 at 8:15:58 AM UTC+1, Martin Brown wrote:
On 26/06/2023 23:54, 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

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.
Depending on how much is not much then for a spot frequency integrating
it once and diode shaping followed by a filter will get all the higher
harmonics well down. HP patent on this trick is long out of date.

I\'m curious - what is special about 1591.55 Hz ?

To do that you actually want to divide 32768 by (almost)
20.6 which gets 1590.68 or easier 20.5 which gets 1598.44

20 21 alternately and then combine with the original clock signal to get
20.5 20.5 equal mark space ratio at your chosen frequency.

20 21 20 21 20 would get your 20.6 but with terrible phase noise and
harmonic content that might well be more problematic to eliminate.
Is that the way it is set up?
More likely how your news client is set up.
Thunderbird has \"Reply\" (to author) as one of its buttons.

Updates sometimes promote it to being the default action too!

--
Martin Brown
Thanks, Martin and all the others who have given helpful advice --- too many to reply individually. The project is tutorial in nature, so I don\'t want to use too many \'integrated\' fixes, and SMD-only devices are not an option. Regarding the frequency, it does need to be near 10k/2pi, but other things can be adjusted to suit the exact frequency, which needs to be stable within ±1% and not require a counter to determine it.

I will try \'Reply to list\' instead of \'Reply\' to see if that works.

Why the requirement to not use a counter??? I don\'t know what that means in this context, since you are proposing on using a counter. Can you explain?

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209